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SpaceX Vehicles and Missions => SpaceX Starship Program => Topic started by: Chris Bergin on 09/28/2016 09:10 pm

Title: ITS Development Updates and Discussion Thread
Post by: Chris Bergin on 09/28/2016 09:10 pm
This thread is for specific discussion (and updates) of the ITS.

I think we're still a bit way off for a specific update thread, so we can have this centralized thread for now and expand as things progress. Main updates - at least via articles on this site - will be standalone threads anyway.

Resources:

Baseline ITS News Article (https://www.nasaspaceflight.com/2016/09/spacex-reveals-mars-game-changer-colonization-plan/)

--

Live Updates from the IAC Speech (http://forum.nasaspaceflight.com/index.php?topic=41250.0)

IAC Speech Discussion Thread (http://forum.nasaspaceflight.com/index.php?topic=41249.0)

*L2 SpaceX Section (http://forum.nasaspaceflight.com/index.php?board=60.0)

--

As always, stay on topic, there are threads for all elements of ITS discussion, so check the SpaceX Mars Forum Section Menu  (https://forum.nasaspaceflight.com/index.php?board=72.0) 
Title: Re: ITS Development Updates and Discussion Thread
Post by: Lars-J on 09/28/2016 10:25 pm
Looking at the ITS spacecraft, I find that it reminds me a *lot* about the Saturn V S-II stage... Very similar, especially how the fuel tank has a conical bottom that connects to the non-vacuum Raptors.

In fact, the whole spacecraft is almost like an S-II stage with additional engines and a cargo/crew compartment on top.
Title: Re: ITS Development Updates and Discussion Thread
Post by: Mongo62 on 09/28/2016 11:54 pm
Tim Urban has a new article about the ITS (http://waitbutwhy.com/2016/09/spacexs-big-fking-rocket-the-full-story.html) up. The title contains an easily guessable "F" word, so I won't be writing it here.

He had a discussion about it with Elon Musk several months ago, and kept quiet about it until today.

I do not know if this image is well-known yet, but attached to this post is a large image of the booster plus spaceship. The quoted excerpt includes an Elon Musk quote from his talk with Tum Urban .

Quote
But if SpaceX can manage to get this thing started, Elon thinks it could be not just a big deal in itself, it could jumpstart a slew of new possibilities for humanity. He explains:

The big picture isn’t just to back up the hard drive but to really change humanity into a multi-planetary species. Essentially what we’re saying is we’re establishing a regular cargo route to Mars. With the economic forcing function of interplanetary commerce, there will be the resources and the incentive to massively improve space transport technology, and I think then things really go to a whole new level.

What I’m describing may sound really crazy, but it actually will be a small fraction of what is ultimately done, as long as we become a two-planet civilization. Look at shipping technology in Europe. When all you had to do was cross the Mediterranean, the ships were pretty lame—they couldn’t cross the Atlantic. So commerce basically had short-range vessels. Without the forcing function, shipping technology didn’t improve that much—you could do the same things with ships, pretty much, around the time of Julius Caesar as you could around the time of Columbus. 1,500 years later, you could still just cross the Mediterranean. But as soon as there was a reason to cross the Atlantic, shipping technology improved dramatically. There needed to be the American colonies in order for that to happen.


The people at SpaceX believe that once we’re on Mars, the rest of the Solar System becomes accessible as well. That’s why they didn’t just create images of their Big frakking Rocket standing proudly on Mars. They showed it flying by Jupiter.

And Saturn.

And bringing human explorers to faraway moons.

They’re planning for a time when any person can go anywhere they want in our vast Solar System—a new golden age for exploration, with uncharted physical frontiers in every direction.
Title: Re: ITS Development Updates and Discussion Thread
Post by: Lars-J on 09/29/2016 05:35 am
For those who still have a hard time visualizing how to unload cargo from so far up, here is what Elon tweeted:

https://twitter.com/elonmusk/status/781206685553528833
Quote
@BArtusio:
@elonmusk How will occupants descend from the spacecraft?At 162 ft., appears too tall to utilize ladder w/  spacesuit. Especially repeatedly

@elonmusk:
@BArtusio Three cable elevator on a crane. Wind force on Mars is low, so don't need to worry about being blown around.

So basically slightly fancier version of this classic Tin-Tin crane.  :)
Title: Re: ITS Development Updates and Discussion Thread
Post by: Oersted on 09/29/2016 09:57 am
Nice ITS profile illustration on Tim Urban's page.
Title: Re: ITS Development Updates and Discussion Thread
Post by: sanman on 09/29/2016 11:57 am
BTW, could ITS ever become a ship-prefix designation like "USS" or "HMS" -- as in the "ITS Heart-of-Gold"?
(ITS could then stand for "Interplanetary Transport Ship")
Title: Re: ITS Development Updates and Discussion Thread
Post by: sanman on 09/29/2016 12:46 pm
If you like the old-style Heinlein space fiction, check out the classic sci-fi fansite "Atomic Rockets"

http://www.projectrho.com/public_html/rocket/embarking.php

Lots of artwork of big rockets with their big cargo cranes

(http://www.projectrho.com/public_html/rocket/images/embarking/cargocrane2.jpg)

(http://www.projectrho.com/public_html/rocket/images/embarking/polarisCut059sm.jpg)

So I guess people on Mars would have to embark/disembark in a basket held by the crane? Is that the fastest, safest, most efficient form of ingress/egress? What if someone has a leak in their spacesuit? Hopefully the winch won't break down. For frequent ingress/egress it might be nicer to have one of those scissor-lift things:

(http://3.imimg.com/data3/WF/EM/MY-1989502/high-rise-scissor-lift-tables-250x250.jpg)

They could even support vehicles easily:

(https://sc01.alicdn.com/kf/HTB1VgCYGFXXXXXlXVXXq6xXFXXXT/200496405/HTB1VgCYGFXXXXXlXVXXq6xXFXXXT.jpg)


Title: Re: ITS Development Updates and Discussion Thread
Post by: nacnud on 09/29/2016 06:25 pm
Question: Why launch the spaceship first, then the tankers.

I think that launching the spaceship first allows more time to fettle the most important launch, the one with the humans on it, so it can be as perfect as possible. It's also going to take more time to load cargo and people than fuel. Given the long launch windows possible with this thing there is time to fix any problems with the spaceship, if there is a problem with a tanker just switch it for another one.

Thoughts?
Title: Re: ITS Development Updates and Discussion Thread
Post by: RonM on 09/29/2016 06:37 pm
Question: Why launch the spaceship first, then the tankers.

I think that launching the spaceship first allows more time to fettle the most important launch, the one with the humans on it, so it can be as perfect as possible. It's also going to take more time to load cargo and people than fuel. Given the long launch windows possible with this thing there is time to fix any problems with the spaceship, if there is a problem with a tanker just switch it for another one.

Thoughts?

Launching the spacecraft first requires the least number of vehicles; booster, spacecraft, and tanker.

If there was a fuel depot, then the tanker flights could fill up the depot first and the spacecraft could be the last launch, but that would require a depot or second tanker. With these vehicles costing hundreds of millions of dollars, that's a big jump in cost.
Title: Re: ITS Development Updates and Discussion Thread
Post by: Lars-J on 09/29/2016 06:40 pm
Question: Why launch the spaceship first, then the tankers.

I think that launching the spaceship first allows more time to fettle the most important launch, the one with the humans on it, so it can be as perfect as possible. It's also going to take more time to load cargo and people than fuel. Given the long launch windows possible with this thing there is time to fix any problems with the spaceship, if there is a problem with a tanker just switch it for another one.

Thoughts?

Launching the spacecraft first requires the least number of vehicles; booster, spacecraft, and tanker.

If there was a fuel depot, then the tanker flights could fill up the depot first and the spacecraft could be the last launch, but that would require a depot or second tanker. With these vehicles costing hundreds of millions of dollars, that's a big jump in cost.

Yep... I you launch the tankers first, you need to have them up there waiting. All 5(?) of them. Whereas in the other approach you could do it with 1 tanker.

I also think that having the spacecraft in LEO for a couple of weeks of outfitting and testing (while tankers are launched) is a good thing. But that would probably mean that passengers should be brought up later, closer to departure by other means. (which might be safer anyway, if other vehicles have abort capability)
Title: Re: ITS Development Updates and Discussion Thread
Post by: sanman on 09/29/2016 07:09 pm
Question: Why launch the spaceship first, then the tankers.

I think that launching the spaceship first allows more time to fettle the most important launch, the one with the humans on it, so it can be as perfect as possible. It's also going to take more time to load cargo and people than fuel. Given the long launch windows possible with this thing there is time to fix any problems with the spaceship, if there is a problem with a tanker just switch it for another one.

Thoughts?

Launching the spacecraft first requires the least number of vehicles; booster, spacecraft, and tanker.

If there was a fuel depot, then the tanker flights could fill up the depot first and the spacecraft could be the last launch, but that would require a depot or second tanker. With these vehicles costing hundreds of millions of dollars, that's a big jump in cost.

Yep... I you launch the tankers first, you need to have them up there waiting. All 5(?) of them. Whereas in the other approach you could do it with 1 tanker.

I also think that having the spacecraft in LEO for a couple of weeks of outfitting and testing (while tankers are launched) is a good thing. But that would probably mean that passengers should be brought up later, closer to departure by other means. (which might be safer anyway, if other vehicles have abort capability)

So you mean have a little shuttle to take you up to the Big Shuttle? Like a Dragon or a Dreamchaser?

A Depot could be used for lots of things, not just Mars trips.
Title: Re: ITS Development Updates and Discussion Thread
Post by: nacnud on 09/29/2016 07:15 pm
I agree no need for a depot. The spacecraft is the depot, and the spacecraft, etc...
Title: Re: ITS Development Updates and Discussion Thread
Post by: RoboGoofers on 09/29/2016 08:11 pm
So I guess people on Mars would have to embark/disembark in a basket held by the crane? Is that the fastest, safest, most efficient form of ingress/egress? What if someone has a leak in their spacesuit? Hopefully the winch won't break down. For frequent ingress/egress it might be nicer to have one of those scissor-lift things:

pulleys and cables are millennia old technology. They're pretty safe and well understood. you can easily lift anything that would fit in one of the cargo containers with a long enough cable, by hand if needed, esp in the lower gravity of Mars. There are many rigging techniques to make this safe and easy. COTS mountain climbing equipment is way overkill for Mars gravity, so there will be plenty of margin.
https://en.wikipedia.org/wiki/Prusik (https://en.wikipedia.org/wiki/Prusik)

if the scissor lift breaks down and you didn't bring rope, you're screwed.
Title: Re: ITS Development Updates and Discussion Thread
Post by: RyanC on 09/29/2016 09:23 pm
I loved the From the Earth To The Moon episode dealing with the LEM so this post is in the vein of that episode.

I'm just wondering what changes we'll see in the ITS between Phase 0 that we have now in September 2016 and the final flight article sometime in 202x.

Some things off the top of my head:

1.) Their early plans for using tons of Carbon Fiber everywhere may be too aggressive and might be toned down.

2.) The number of windows might be reduced substantially for cost/quality reasons -- it's one thing to qualify a window in Dragon 2 for a 30 day on orbit period; another to qualify a window for a period approaching a year in space before it can return to Earth for inspection.
Title: Re: ITS Development Updates and Discussion Thread
Post by: Lars-J on 09/29/2016 09:29 pm
2.) The number of windows might be reduced substantially for cost/quality reasons -- it's one thing to qualify a window in Dragon 2 for a 30 day on orbit period; another to qualify a window for a period approaching a year in space before it can return to Earth for inspection.

Oh yeah... If this thing ever flies in this form, the front end will end up looking VERY different. I'm sure of it.
Title: Re: ITS Development Updates and Discussion Thread
Post by: Oersted on 09/29/2016 09:54 pm
I loved the From the Earth To The Moon episode dealing with the LEM so this post is in the vein of that episode.

Yes, I remember that episode as well, and got more background info from the book "Moon lander" by Grumman chief engineer Thomas Kelly (https://www.amazon.com/Moon-Lander-Developed-Apollo-Module/dp/156098998X).

They originally wanted a big helicopter-like bubble canopy for the LM, to give maximum visibility for landing, even though such a bubble would be very heavy and probably not very solid. When they realised that the astronauts might as well stand up during landing, they also concluded that a small pane of optically perfect glass right up against the face of the astronauts would give a very good view.

Very possibly something similar will happen to the IST. Would they really sacrifice payload to the Martian surface for quite useless panorama windows? - I doubt it.
Title: Re: ITS Development Updates and Discussion Thread
Post by: HVM on 09/29/2016 10:03 pm
Comparing sizes again:

Also excluding panorama window, shuttle orbiter have bigger individual windows than ITS.
Title: Re: ITS Development Updates and Discussion Thread
Post by: Snake on 09/30/2016 02:09 am
I was impressed with robustness and redundancy of the engine configuration on the BFS. I have been imagining how the ship would fare if engines were lost and doing some rough calculations. I think it could probably land on Mars with any 2 engines out and land on Earth with perhaps 3 out (as long as they are not all Sea Level Raptors).

This 6-3 engine set-up seems optimized to be a minimum engine configuration to get a maximum redundancy level. But I really don't know how to quantify it.
Title: Re: ITS Development Updates and Discussion Thread
Post by: RedLineTrain on 09/30/2016 03:45 am
Presumably, SpaceX could have a robust testing regime, given the relatively modest consumables budget, but I'm guessing that you wouldn't want to do it at 39A.

But I wonder whether it would be possible to transport the booster and spaceship to Spaceport America for suborbital flights.  Would the transport cost be prohibitive?
Title: Re: ITS Development Updates and Discussion Thread
Post by: Nathan2go on 09/30/2016 03:46 am
... I'm just wondering what changes we'll see in the ITS between Phase 0 that we have now in September 2016 and the final flight article sometime in 202x.
Radiator panels that open up to let out heat?  (Shuttle had radiators in the cargo bay doors.)
ITS will need radiators for the passenger compartment, and I would assume for the propellant refrigeration system?
Title: Re: ITS Development Updates and Discussion Thread
Post by: b0objunior on 09/30/2016 03:47 am
Comparing sizes again:

Also excluding panorama window, shuttle orbiter have bigger individual windows than ITS.
Made myself one also. Sea Dragon for fun.
Title: Re: ITS Development Updates and Discussion Thread
Post by: Jim on 09/30/2016 03:48 am
I would assume for the propellant refrigeration system?

What propellant refrigeration system?
Title: Re: ITS Development Updates and Discussion Thread
Post by: Seer on 09/30/2016 04:06 am
How is the heat from the heatshield rejected from the spacecraft during entry, especially on Mars entry which is hotter and where the atmosphere on the surface won't conduct heat away very quickly?

How will the heatshield be inspected in for damage either in space or on Mars after entry? Imagine having to replace one of the PICAX panels on this thing when its on the surface of Mars.
Title: Re: ITS Development Updates and Discussion Thread
Post by: zodiacchris on 09/30/2016 04:24 am
I was wondering, given that the spaceship can just about make LEO on it's own, without the booster, would it be conceivable to launch an early prototype into LEO, stripped down to the bare essentials, and then refuel it using repeated FH tanker flights? That would allow shake down cruise in earth orbit or further out, maybe cis-lunar, and EDL. If it has life support, a Dragon 2 could even bring crew up, and take them down again, before the autonomous landing of the BFS. ???
Anybody done the numbers?
Title: Re: ITS Development Updates and Discussion Thread
Post by: Seer on 09/30/2016 04:26 am
I was wondering, given that the spaceship can just about make LEO on it's own, without the booster, would it be conceivable to launch an early prototype into LEO, stripped down to the bare essentials, and then refuel it using repeated FH tanker flights? That would allow shake down cruise in earth orbit or further out, maybe cis-lunar, and EDL. If it has life support, a Dragon 2 could even bring crew up, and take them down again, before the autonomous landing of the BFS. ???
Anybody done the numbers?

I think the propellant fraction of the upperstage is around 85%, much less than the >90% needed for SSTO.
Title: Re: ITS Development Updates and Discussion Thread
Post by: docmordrid on 09/30/2016 04:43 am
I would assume for the propellant refrigeration system?

What propellant refrigeration system?

I would assume using densified propellants in Raptor means chilling them on Mars and in transit.
Title: Re: ITS Development Updates and Discussion Thread
Post by: Dante80 on 09/30/2016 05:12 am
Question: Why launch the spaceship first, then the tankers.

I think that launching the spaceship first allows more time to fettle the most important launch, the one with the humans on it, so it can be as perfect as possible. It's also going to take more time to load cargo and people than fuel. Given the long launch windows possible with this thing there is time to fix any problems with the spaceship, if there is a problem with a tanker just switch it for another one.

Thoughts?

Launching the spacecraft first requires the least number of vehicles; booster, spacecraft, and tanker.

If there was a fuel depot, then the tanker flights could fill up the depot first and the spacecraft could be the last launch, but that would require a depot or second tanker. With these vehicles costing hundreds of millions of dollars, that's a big jump in cost.

Lets say that you need 4 tanker flights to refuel the spaceship. There are three ways to do this when starting the endeavor.

1. 1x booster, 1x tanker, 1x spaceship

Flight 1: Spaceship goes up with passengers
Flights 2-3-4-5 Tankers refuel the Spaceship.

2. 1x booster 2x tanker, 1x spaceship

Flight 1: Tanker goes up.
Flights 2-3-4: Tankers refuel the tanker.
Flight 5: Spaceship goes up with passengers and refuels from the tanker.

3. 1x booster, 1x tanker, 2x spaceship

Flight 1: Spaceship goes up unmanned.
Flights 2-3-4-5 Tankers refuel the Spaceship
Flight 6: Spaceship goes up and transfers passengers.

Between the three, the first approach allows for the leanest start hardware, the second allows you to use a tanker as a fuel depot and limit the time passengers spend on the staging area and the third is simply a contigency approach Elon described if the refueling process is not as rapid (2-3 weeks) as assumed.

Interestingly enough, the second approach points to the introduction of a staging area depot in the future (it simply scales operations better as you add hardware to the system). Especially since you limit the number of rendevous and fuelling operations for the fully manned Spaceship, as well as the time the passengers have to spend on the ship before departure (using the ships' supplies).

You can simply start a more dedicated depot by bringing a tanker up with some solar arrays and added insulation to make the propellants space storable for a much larger time.
Title: Re: ITS Development Updates and Discussion Thread
Post by: Dante80 on 09/30/2016 05:39 am
I was impressed with robustness and redundancy of the engine configuration on the BFS. I have been imagining how the ship would fare if engines were lost and doing some rough calculations. I think it could probably land on Mars with any 2 engines out and land on Earth with perhaps 3 out (as long as they are not all Sea Level Raptors).

This 6-3 engine set-up seems optimized to be a minimum engine configuration to get a maximum redundancy level. But I really don't know how to quantify it.

The only engines that gimbal on the spaceship are the three atmo optimized Raptors. The only engines that gimbal on the booster are the inner 7 engines.

Btw...here is a thought. I think that the spaceship engine configuration for Mars landing is designed so that each engine gimbals slgihtly towards the fins on the very final approach so as to clear the ground for the feet at touchdown. This would introduce some cosine losses, but also make the landing on unprepared surfaces easier I think (as well as protect from debris impacting the spaceship).
Title: Re: ITS Development Updates and Discussion Thread
Post by: biosehnsucht on 09/30/2016 06:34 am
Those cosine losses give you effectively even lower than 20% throttle, which might be also useful on it's own. They're not likely to need 3x 100% on the last seconds of landing burn...
Title: Re: ITS Development Updates and Discussion Thread
Post by: Snake on 09/30/2016 07:06 am
A 600 t BFS landing on Mars would have a weight of 3.8 x 600 = 2,280 kN. Raptor SL engines have a max. thrust of 3,050 kN, so any or all of them could be used to land.

And yes, gimballing the engines outwards while landing on an unprepared site seems like it would help reduce blowback.
Title: Re: ITS Development Updates and Discussion Thread
Post by: Dante80 on 09/30/2016 07:31 am
A 600 t BFS landing on Mars would have a weight of 3.8 x 600 = 2,280 kN. Raptor SL engines have a max. thrust of 3,050 kN, so any or all of them could be used to land.

And yes, gimballing the engines outwards while landing on an unprepared site seems like it would help reduce blowback.

SL Raptors on Mars surface have more than 3050 kN of thrust. If we assume that they use the same 40:1 nozzle area ratio with the BFR Raptors, then the derived thrust according to the available information should be somewhere between 3,285 kN and 3,333 kN (138 MN / 42 engines or (31MN - 6x3,500kn) /3 engines), or a little less.
Title: Re: ITS Development Updates and Discussion Thread
Post by: Snake on 09/30/2016 07:56 am
A 600 t BFS landing on Mars would have a weight of 3.8 x 600 = 2,280 kN. Raptor SL engines have a max. thrust of 3,050 kN, so any or all of them could be used to land.

And yes, gimballing the engines outwards while landing on an unprepared site seems like it would help reduce blowback.

SL Raptors on Mars surface have more than 3050 kN of thrust. If we assume that they use the same 40:1 nozzle area ratio with the BFR Raptors, then the derived thrust according to the available information should be somewhere between 3,285 kN and 3,333 kN (138 MN / 42 engines or 31MN - 6x3,500kn) /3 engines), or a little less.

Yes, thanks, the Raptor will have a higher thrust than I said. But even at 3,333 kN, you could still throttle low enough to land a full payload on all 3 Raptor SLs, (even without gimballing cosine losses), if desired.
Title: Re: ITS Development Updates and Discussion Thread
Post by: TheTraveller on 09/30/2016 08:26 am
Tim Urban has a new article about the ITS (http://waitbutwhy.com/2016/09/spacexs-big-fking-rocket-the-full-story.html) up. The title contains an easily guessable "F" word, so I won't be writing it here.

He had a discussion about it with Elon Musk several months ago, and kept quiet about it until today.

Interesting timeline attached.

1st uncrewed ITS to be launched Dec 2022!
Title: Re: ITS Development Updates and Discussion Thread
Post by: TheTraveller on 09/30/2016 09:11 am
Can the ITS tanker version of the spaceship do SSTO to allow orbital testing before the ITS booster files?

From the attached maybe it can do so and even carry a small test crew, assuming 91t of fuel in LEO is enough to deorbit and land.
Title: Re: ITS Development Updates and Discussion Thread
Post by: Dante80 on 09/30/2016 09:18 am

From the attached maybe it can do so

Musk said it cannot.
Title: Re: ITS Development Updates and Discussion Thread
Post by: TheTraveller on 09/30/2016 09:29 am

From the attached maybe it can do so

Musk said it cannot.

Pax SpaceShip, sure. But the tanker at 2,590t wet and 90t dry should be capable of SSTO with 91.7t of fuel to get home.

Rocket equation for the ITS SpaceShip makes it clear SSTO is not possible as max lift is 147t and SpaceShip dry mass is 150t as attached. Even if it did just make orbit, there is no fuel to get back home.

However it should be possible for the ITS Tanker to allow testing with a small crew prior to ITS Booster availability as the 90t Tanker can make orbit with 91.7t of fuel (181.7t total LEO mass) to get back home.
Title: Re: ITS Development Updates and Discussion Thread
Post by: high road on 09/30/2016 10:02 am
For those who still have a hard time visualizing how to unload cargo from so far up, here is what Elon tweeted:

https://twitter.com/elonmusk/status/781206685553528833
Quote
@BArtusio:
@elonmusk How will occupants descend from the spacecraft?At 162 ft., appears too tall to utilize ladder w/  spacesuit. Especially repeatedly

@elonmusk:
@BArtusio Three cable elevator on a crane. Wind force on Mars is low, so don't need to worry about being blown around.

So basically slightly fancier version of this classic Tin-Tin crane.  :)

Is it just me or is there a certain 'redneck on Mars' vibe to using these? European depictions of 17th-18th century America always show hay attics with these cranes. And if you count similar cranes for ships, all harbour images going back thousands of years show them. Not that romanticism about going to Mars is a problem, if the people paying for it accept the associated injury (and some death) rate. Which would go a long way in bringing down the cost of a Mars mission anyway.

So I guess people on Mars would have to embark/disembark in a basket held by the crane? Is that the fastest, safest, most efficient form of ingress/egress? What if someone has a leak in their spacesuit? Hopefully the winch won't break down. For frequent ingress/egress it might be nicer to have one of those scissor-lift things:

(http://3.imimg.com/data3/WF/EM/MY-1989502/high-rise-scissor-lift-tables-250x250.jpg)

They could even support vehicles easily:

(https://sc01.alicdn.com/kf/HTB1VgCYGFXXXXXlXVXXq6xXFXXXT/200496405/HTB1VgCYGFXXXXXlXVXXq6xXFXXXT.jpg)

This comes with a mass penalty because you need the center of mass to be low for stability, and maintenance issues because the crane has a lot more moving parts, that are now standing in Martian dust and on the outside of the biggest rigid pressurized area that wasn't constrained by having to be easy to set up on Mars. Oh, and that means loading them also becomes more difficult than a retractible beam.
Title: Re: ITS Development Updates and Discussion Thread
Post by: MP99 on 09/30/2016 10:45 am
I would assume for the propellant refrigeration system?

What propellant refrigeration system?
Elon seemed to say that they relied on subcooled prop to avoid various issues, including cavitation.

Is it possible for prop to remain sub-cooled over a multi month Mars transit?

ISTM the alternative is to let the prop reach boiling point, then manage boiloff?

Cheers, Martin
Title: Re: ITS Development Updates and Discussion Thread
Post by: Jim on 09/30/2016 12:56 pm
I would assume for the propellant refrigeration system?

What propellant refrigeration system?
Elon seemed to say that they relied on subcooled prop to avoid various issues, including cavitation.

Is it possible for prop to remain sub-cooled over a multi month Mars transit?

ISTM the alternative is to let the prop reach boiling point, then manage boiloff?

Cheers, Martin

Use the boil off for attitude control and electrical power production
Title: Re: ITS Development Updates and Discussion Thread
Post by: OneSpeed on 09/30/2016 02:49 pm
Can the ITS tanker version of the spaceship do SSTO to allow orbital testing before the ITS booster files?

From the attached maybe it can do so and even carry a small test crew, assuming 91t of fuel in LEO is enough to deorbit and land.

The SL Raptor has 3,050 kN of thrust at sea level, or 311 mT. If there are only 3 SL Raptors on the tanker, that is 933 mT of thrust, which from earth is not sufficient to launch a 2590 mT ship.
Title: Re: ITS Development Updates and Discussion Thread
Post by: TheTraveller on 09/30/2016 04:35 pm
Can the ITS tanker version of the spaceship do SSTO to allow orbital testing before the ITS booster files?

From the attached maybe it can do so and even carry a small test crew, assuming 91t of fuel in LEO is enough to deorbit and land.

The SL Raptor has 3,050 kN of thrust at sea level, or 311 mT. If there are only 3 SL Raptors on the tanker, that is 933 mT of thrust, which from earth is not sufficient to launch a 2590 mT ship.

Interesting the atmo Raptors have a 361 Isp on the BFS spec sheet, which is higher than the stated atmo Isp of 334 and lower than the Vac Isp of 382 on the Raptor engine spec sheet. Just maybe they can burn all 9 engines in atmo to get a combined 361 Isp and a combined thrust of around 2,800mT?

Elon did say that on Earth, the BFS was the Launch Abort System, so the 9 x BFS Raptors much have the capacity to get the BFS away from the BFR.
Title: Re: ITS Development Updates and Discussion Thread
Post by: wrvn on 09/30/2016 04:44 pm
Interesting the atmo Raptors have a 361 Isp on the BFS spec sheet, which is higher than the stated atmo Isp of 334 and lower than the Vac Isp of 382 on the Raptor engine spec sheet.

Could it be that 361 Isp figure is for Mars atmosphere?
Title: Re: ITS Development Updates and Discussion Thread
Post by: Dante80 on 09/30/2016 04:50 pm
Here is how it works.

1. SL Raptor with 40:1 ratio nozzle

SL Isp: 334s
Vac Isp: 361s

2. Vac Raptor with 200:1 ratio nozzle

Vac Isp 382s

Both the booster and the spaceship use the same SL Raptors (in the Booster, the inner 7 have gimbals, and in the spaceship all three).The booster has an additional 35 SL Raptors that cannot gimbal, and the spaceship has six Vac Raptors that cannot gimbal.
Title: Re: ITS Development Updates and Discussion Thread
Post by: TheTraveller on 09/30/2016 05:02 pm
Here is how it works.

1. SL Raptor with 40:1 ratio nozzle

SL Isp: 334s
Vac Isp: 361s

2. Vac Raptor with 200:1 ratio nozzle

Vac Isp 382s

Both the booster and the spaceship use the same SL Raptors (in the Booster, the inner 7 have gimbals, and in the spaceship all three).The booster has an additional 35 SL Raptors that cannot gimbal, and the spaceship has six Vac Raptors that cannot gimbal.

The BFS spec sheet shows atmo Raptor Isp of 361 which as all 9 BFS Raptors need to fire up to do Earth side LAS, would suggest that 361 is the averaged Isp of 3 atmo bell and 6 Vac bell Raptors running at the same time.
Title: Re: ITS Development Updates and Discussion Thread
Post by: MP99 on 09/30/2016 05:02 pm


I would assume for the propellant refrigeration system?

What propellant refrigeration system?
Elon seemed to say that they relied on subcooled prop to avoid various issues, including cavitation.

Is it possible for prop to remain sub-cooled over a multi month Mars transit?

ISTM the alternative is to let the prop reach boiling point, then manage boiloff?

Cheers, Martin

Use the boil off for attitude control and electrical power production

But what if the engine needs sub-cooled propellants?

Cheers, Martin

Title: Re: ITS Development Updates and Discussion Thread
Post by: IRobot on 09/30/2016 05:13 pm

Look at shipping technology in Europe. When all you had to do was cross the Mediterranean, the ships were pretty lame—they couldn’t cross the Atlantic. So commerce basically had short-range vessels. Without the forcing function, shipping technology didn’t improve that much—you could do the same things with ships, pretty much, around the time of Julius Caesar as you could around the time of Columbus. 1,500 years later, you could still just cross the Mediterranean. But as soon as there was a reason to cross the Atlantic, shipping technology improved dramatically. There needed to be the American colonies in order for that to happen.
Actually, the Atlantic sailing vessels (Caravels) were developed by the Portuguese 40-50 years before Columbus, in incremental steps to be able to sail against the wind on the African coast.
Ships would be sent, they would fail, then after 2-3 years they would try with some modified ships.

The real drive for development was the discovery of the maritime path to India, America's discovery was an "accident". There were no european colonies in India, so the analogy is not correct.
Title: Re: ITS Development Updates and Discussion Thread
Post by: Dante80 on 09/30/2016 05:14 pm
The BFS spec sheet shows atmo Raptor Isp of 361 which as all 9 BFS Raptors need to fire up to do Earth side LAS, would suggest that 361 is the averaged Isp of 3 atmo bell and 6 Vac bell Raptors running at the same time.

I think it is pretty clear, and distinct. Read this slide.

(https://i.imgur.com/rUOJ2Kh.png)

3 seal level raptors = 361s
6 vacuum raptors   = 382s

And in another slide, it is shown that vac and SL Raptors are pretty much the same engine, with different nozzles.

(https://i.imgur.com/OPLxwk8.png)

If SpaceX added two lines in the second slide for sea level nozzle Raptor thrust and Isp performance in vacuum, this confusion would be averted.
Title: Re: ITS Development Updates and Discussion Thread
Post by: TheTraveller on 09/30/2016 05:26 pm
The BFS spec sheet shows atmo Raptor Isp of 361 which as all 9 BFS Raptors need to fire up to do Earth side LAS, would suggest that 361 is the averaged Isp of 3 atmo bell and 6 Vac bell Raptors running at the same time.
If SpaceX added two lines in the second slide for sea level nozzle Raptor thrust and Isp performance in vacuum, this confusion would be averted.

And the sea level Isp for the vac Raptor nozzle would be?
Title: Re: ITS Development Updates and Discussion Thread
Post by: Dante80 on 09/30/2016 06:02 pm
And the sea level Isp for the vac Raptor nozzle would be?

Irrelevant? Do you get an SL Isp for RL-10 or J-2X?

The vacuum Raptors are going to work strictly in vacuum, or near vacuum.Nowhere near Earth sea level with that huge nozzle.
Title: Re: ITS Development Updates and Discussion Thread
Post by: Snake on 09/30/2016 06:06 pm
And the sea level Isp for the vac Raptor nozzle would be?

Irrelevant? Do you get an SL isp for RL-10 orJ-2X?

The vacuum Raptors are going to work in vacuum.

The vacuum Raptors will work at or near sea level for some launch abort/escape sequences. I would like to know the engine's Isp at sea level for this reason alone.
Title: Re: ITS Development Updates and Discussion Thread
Post by: TheTraveller on 09/30/2016 06:11 pm
And the sea level Isp for the vac Raptor nozzle would be?

Irrelevant? Do you get an SL Isp for RL-10 or J-2X?

The vacuum Raptors are going to work strictly in vacuum, or near vacuum.Nowhere near Earth sea level with that huge nozzle.

All 9 BFS Raptors are used for Earth side LAS, Vac nozzles included.

BTW RPA Lite (free version):
http://www.propulsion-analysis.com/downloads.htm
calcs:

SL Nozzle (40 expansion) @ SL = 334 Isp, @ Vac = 360 Isp.
Vac Nozzle (200 expansion) @ SL = 253 Isp, @ Vac = 382 Isp.

Both at 300 bar chamber pressure, mixture ratio 2.7/2.8, fuel LCH4/LOX.
Title: Re: ITS Development Updates and Discussion Thread
Post by: baldusi on 09/30/2016 06:14 pm
And the sea level Isp for the vac Raptor nozzle would be?

Irrelevant? Do you get an SL isp for RL-10 orJ-2X?

The vacuum Raptors are going to work in vacuum.

The vacuum Raptors will work at or near sea level for some launch abort/escape sequences. I would like to know the engine's Isp at sea level for this reason alone.
Nope, you get flow separation issues on the 200 expanded nozzle, which might even created burn troughs. No SL ignition of vacuum optimized nozzles.
Title: Re: ITS Development Updates and Discussion Thread
Post by: TheTraveller on 09/30/2016 06:17 pm
And the sea level Isp for the vac Raptor nozzle would be?

Irrelevant? Do you get an SL isp for RL-10 orJ-2X?

The vacuum Raptors are going to work in vacuum.

The vacuum Raptors will work at or near sea level for some launch abort/escape sequences. I would like to know the engine's Isp at sea level for this reason alone.
Nope, you get flow separation issues on the 200 expanded nozzle, which might even created burn troughs. No SL ignition of vacuum optimized nozzles.

If so then how can the BFS engines work as LAS as Elon stated? The 3 atmo nozzled Raptors don't have enough lift for LAS.
Title: Re: ITS Development Updates and Discussion Thread
Post by: Barrie on 09/30/2016 06:25 pm
And the sea level Isp for the vac Raptor nozzle would be?

Irrelevant? Do you get an SL isp for RL-10 orJ-2X?

The vacuum Raptors are going to work in vacuum.

The vacuum Raptors will work at or near sea level for some launch abort/escape sequences. I would like to know the engine's Isp at sea level for this reason alone.
Nope, you get flow separation issues on the 200 expanded nozzle, which might even created burn troughs. No SL ignition of vacuum optimized nozzles.

Wouldn't you be quite happy to trash the nozzles for an abort?
Title: Re: ITS Development Updates and Discussion Thread
Post by: JasonAW3 on 09/30/2016 06:26 pm
Comparing sizes again:

Also excluding panorama window, shuttle orbiter have bigger individual windows than ITS.
Made myself one also. Sea Dragon for fun.

Wonder if a Methalox Sea Dragon would be feasible?
Title: Re: ITS Development Updates and Discussion Thread
Post by: notsorandom on 09/30/2016 06:39 pm
Wouldn't you be quite happy to trash the nozzles for an abort?
Not if it creates asymmetric thrust that cannot be compensated for.
Title: Re: ITS Development Updates and Discussion Thread
Post by: rubicondsrv on 09/30/2016 06:49 pm
Wouldn't you be quite happy to trash the nozzles for an abort?
Not if it creates asymmetric thrust that cannot be compensated for.

IMO that will be sorted out at some point.   this is still very early in the design process and many things can change.   

it would be quite possible to design a mechanism to shorten the nozzle in an abort if the overexpansion would not be tolerable for a few seconds.  however this would add weight to the engine

given how much remains to be done before production expect many changes to the final version before production.   
Title: Re: ITS Development Updates and Discussion Thread
Post by: DanielW on 09/30/2016 06:51 pm
Wouldn't you be quite happy to trash the nozzles for an abort?
Not if it creates asymmetric thrust that cannot be compensated for.

There must be a way to pryo cut the nozzle in this case. Or release a band that holds it on.
Title: Re: ITS Development Updates and Discussion Thread
Post by: Robotbeat on 09/30/2016 08:03 pm
And the sea level Isp for the vac Raptor nozzle would be?

Irrelevant? Do you get an SL isp for RL-10 orJ-2X?

The vacuum Raptors are going to work in vacuum.

The vacuum Raptors will work at or near sea level for some launch abort/escape sequences. I would like to know the engine's Isp at sea level for this reason alone.
Nope, you get flow separation issues on the 200 expanded nozzle, which might even created burn troughs. No SL ignition of vacuum optimized nozzles.

If so then how can the BFS engines work as LAS as Elon stated? The 3 atmo nozzled Raptors don't have enough lift for LAS.
Not enough thrust for pad abort, unless you severed the nozzle to prevent flow sep. but would still have enough thrust for some abort scenarios. With liquid rockets, you can reliably terminate thrust of the booster engines in case of abort.
Title: Re: ITS Development Updates and Discussion Thread
Post by: RoboGoofers on 09/30/2016 08:15 pm
lets not forget what abort means with ITS; propulsive landing or abort to orbit only. Without the vac bells, maybe only landing. with a full load of fuel, cargo and passengers, abort sounds about as comforting as 'aborting' an airplane into a forest.
Title: Re: ITS Development Updates and Discussion Thread
Post by: Lars-J on 09/30/2016 08:23 pm
For those who still have a hard time visualizing how to unload cargo from so far up, here is what Elon tweeted:

https://twitter.com/elonmusk/status/781206685553528833
Quote
@BArtusio:
@elonmusk How will occupants descend from the spacecraft?At 162 ft., appears too tall to utilize ladder w/  spacesuit. Especially repeatedly

@elonmusk:
@BArtusio Three cable elevator on a crane. Wind force on Mars is low, so don't need to worry about being blown around.

So basically slightly fancier version of this classic Tin-Tin crane.  :)

Is it just me or is there a certain 'redneck on Mars' vibe to using these? European depictions of 17th-18th century America always show hay attics with these cranes. And if you count similar cranes for ships, all harbour images going back thousands of years show them. Not that romanticism about going to Mars is a problem, if the people paying for it accept the associated injury (and some death) rate. Which would go a long way in bringing down the cost of a Mars mission anyway.

What is redneck about using simple and proven (& safe) technology? Don't let our simple images & drawings fool you, it isn't going to look exactly like that.

But I do find it funny that some people think that lowering cargo from a greater height is somehow going be the the 'gotcha' moment or technological challenge that will somehow break Elon's plan.  ;D
Title: Re: ITS Development Updates and Discussion Thread
Post by: Snake on 10/01/2016 12:24 am
And the sea level Isp for the vac Raptor nozzle would be?

Irrelevant? Do you get an SL isp for RL-10 orJ-2X?

The vacuum Raptors are going to work in vacuum.

The vacuum Raptors will work at or near sea level for some launch abort/escape sequences. I would like to know the engine's Isp at sea level for this reason alone.
Nope, you get flow separation issues on the 200 expanded nozzle, which might even created burn troughs. No SL ignition of vacuum optimized nozzles.

If so then how can the BFS engines work as LAS as Elon stated? The 3 atmo nozzled Raptors don't have enough lift for LAS.
Not enough thrust for pad abort, unless you severed the nozzle to prevent flow sep. but would still have enough thrust for some abort scenarios. With liquid rockets, you can reliably terminate thrust of the booster engines in case of abort.

How would the regenerative cooling system continue to work if the nozzle were truncated during abort?

Also I imagine that during its flight testing, before the booster is built, the BFS may be mounted with all Raptor (SL) engines so that it CAN take off with close to a standard payload.
Title: Re: ITS Development Updates and Discussion Thread
Post by: Robotbeat on 10/01/2016 12:39 am
And the sea level Isp for the vac Raptor nozzle would be?

Irrelevant? Do you get an SL isp for RL-10 orJ-2X?

The vacuum Raptors are going to work in vacuum.

The vacuum Raptors will work at or near sea level for some launch abort/escape sequences. I would like to know the engine's Isp at sea level for this reason alone.
Nope, you get flow separation issues on the 200 expanded nozzle, which might even created burn troughs. No SL ignition of vacuum optimized nozzles.

If so then how can the BFS engines work as LAS as Elon stated? The 3 atmo nozzled Raptors don't have enough lift for LAS.
Not enough thrust for pad abort, unless you severed the nozzle to prevent flow sep. but would still have enough thrust for some abort scenarios. With liquid rockets, you can reliably terminate thrust of the booster engines in case of abort.

How would the regenerative cooling system continue to work if the nozzle were truncated during abort?
...
Yes, because the bottom part of a vacuum nozzle is radiatively cooled, not regeneratively.
Title: Re: ITS Development Updates and Discussion Thread
Post by: jiv on 10/01/2016 01:40 am

From Tim Urban's Elon Musk quote:
Look at shipping technology in Europe. When all you had to do was cross the Mediterranean, the ships were pretty lame ... There needed to be the American colonies

Actually, the Atlantic sailing vessels (Caravels) were developed by the Portuguese 40-50 years before Columbus, in incremental steps ...

The real drive for development was the discovery of the maritime path to India... There were no european colonies in India, so the analogy is not correct.

I've given this statement some thought, and wanted to both highlight and address it. It struck me as an excellent reminder to check one's facts and assumptions, and very relevant to the discussion of ITS' value since the "forcing function" concept is important to the future Elon is trying to achieve.

While it's true that the American Colonies did not lead to the development of Caravels or even other significantly more advanced ships, I think this view is too focused. It's certainly true that the American Colonies and trade in the Indies were the lucky beneficiaries of other forcing functions, such as the African trade mentioned above. However, once established, these initially-dubious ventures themselves became forcing functions for better technologies, and now we have these incredible ships that could move probably the entire first century's worth of transatlantic trade in a single voyage.

Technological progress occurs where our ambitions are just at the edge of what is possible. I have no idea whether profit will be found in interplanetary trade, but I think it's clear that a successful colony will lead to better ships.

Edit 1: fix quote attribution: I didn't mean to make it look like Mongo62 was the one talking about forcing functions for shipping technology.
Edit 2: @mods -- it occurs to me that defending Elon's rationale for ITS may be off topic for a development discussion thread, but I'm not sure if it would make more sense to reply out of context in another thread. Long story short: feel free to delete this post if it doesn't belong.
Title: Re: ITS Development Updates and Discussion Thread
Post by: high road on 10/01/2016 10:44 am
For those who still have a hard time visualizing how to unload cargo from so far up, here is what Elon tweeted:

https://twitter.com/elonmusk/status/781206685553528833
Quote
@BArtusio:
@elonmusk How will occupants descend from the spacecraft?At 162 ft., appears too tall to utilize ladder w/  spacesuit. Especially repeatedly

@elonmusk:
@BArtusio Three cable elevator on a crane. Wind force on Mars is low, so don't need to worry about being blown around.

So basically slightly fancier version of this classic Tin-Tin crane.  :)

Is it just me or is there a certain 'redneck on Mars' vibe to using these? European depictions of 17th-18th century America always show hay attics with these cranes. And if you count similar cranes for ships, all harbour images going back thousands of years show them. Not that romanticism about going to Mars is a problem, if the people paying for it accept the associated injury (and some death) rate. Which would go a long way in bringing down the cost of a Mars mission anyway.

What is redneck about using simple and proven (& safe) technology? Don't let our simple images & drawings fool you, it isn't going to look exactly like that.

But I do find it funny that some people think that lowering cargo from a greater height is somehow going be the the 'gotcha' moment or technological challenge that will somehow break Elon's plan.  ;D

The redneck/romantic part is where a safe and proven technology is represented by how it looked like 200 years ago, so it becomes easier to forget that making this part easier, makes other things way harder.

I see no showstoppers per se. But lowering everything from the rocket by sling means the individual components need to be relatively small. So lots of assembly required, which is not easy on Mars, especially if everything needs to withstand airpressure and needs to be moved and assembled by muscle alone (continuing the redneck vibe I got from the idea). The alternative is to bring a truck that again requires maintenance, and needs to be able to mqnipulate all components with high precision. Not impossible, but not handwavable either.
Title: Re: ITS Development Updates and Discussion Thread
Post by: sanman on 10/01/2016 02:01 pm
I forget if it was covered in the presentation - but what is the cost of a single ITS likely to be? (booster+spaceship)
Title: Re: ITS Development Updates and Discussion Thread
Post by: AncientU on 10/01/2016 02:05 pm
I forget if it was covered in the presentation - but what is the cost of a single ITS likely to be? (booster+spaceship)

Video at 1:04:40

Booster -- $230M
Tanker -- $150M
Ship -- $200M
Title: Re: ITS Development Updates and Discussion Thread
Post by: docmordrid on 10/01/2016 02:13 pm
I forget if it was covered in the presentation - but what is the cost of a single ITS likely to be? (booster+spaceship)

Presentation slides

http://www.spacex.com/sites/spacex/files/mars_presentation.pdf
Title: Re: ITS Development Updates and Discussion Thread
Post by: sanman on 10/01/2016 05:21 pm
Holy smokes - so that's on the order of a billion dollars - this really is more like a luxury cruise ship than an airliner - will Lloyds of London insure something like the ITS? Because if one of these prized ships were to go up in smoke, particularly during the early years, then that's a huge hole in your cash flow.
Title: Re: ITS Development Updates and Discussion Thread
Post by: Mongo62 on 10/01/2016 05:52 pm
Holy smokes - so that's on the order of a billion dollars - this really is more like a luxury cruise ship than an airliner - will Lloyds of London insure something like the ITS? Because if one of these prized ships were to go up in smoke, particularly during the early years, then that's a huge hole in your cash flow.

A typical new Boeing 777 costs USD 320M, and a 747 costs USD 357M. A typical Airbus A380 costs USD 375M. I would say that the costs of an ITS fleet and a jumbo jet fleet would be very comparable.

I think that costs for passengers to LEO would be of the same order of magnitude as current luxury long-distance air flights.
Title: Re: ITS Development Updates and Discussion Thread
Post by: sanman on 10/01/2016 06:34 pm
Here are some remarks from M̶u̶s̶k̶  Andy Weir (author of The Martian) quoted in Ars Technica:

http://arstechnica.com/the-multiverse/2016/10/the-martians-andy-weir-talks-to-ars-about-the-science-of-musks-mars-vision/


Quote
The reasons for choosing to go with a whole bunch of smaller engines versus a few massive ones are myriad, but there are also risks—primarily around the complexity of the plumbing and controls to make that many separate thrusters work. The only other example of a launch vehicle with something approaching that many engines is the ill-fated Soviet N1 booster, which packaged thirty NK-15 kerolox engines into its first stage. Four N1 boosters flew from Baikonur between February 1969 and November 1972, and all four exploded. Three of the explosions were either related to or directly caused by the complicated KORD system that managed the N1’s bouquet of engines. (KORD is an acronym for “Control of Rocket Engines”— “KOntrol Racketnykh Dvigateley” or Контроль ракетных двигателей.)

But comparisons between the underfunded N1 and the potential failures awaiting Musk’s ITS BFR aren’t necessarily valid or useful. We asked Weir how Musk’s idea of slapping forty-two engines on a rocket made him feel.

“It makes me feel good,” he replied. “The more engines you have, the more safe points of failure you have. In other words, if, you know, if four engines go out during the ascent when you have forty-two of them, then you just burn the other thirty-eight a little longer. If four of your five Saturn V engines go out during ascent, then you’re really, really super-fucked.”

“The complexity that the Soviets ran into with the N1 was all about control systems, and nowadays we have computers that can handle that sort of thing….So, yeah, I think lots of little engines is a good approach,” he laughed. “The only question is how much mass you end up putting onto the booster to have all of those—to have a whole bunch of engines as opposed to one big one. One big one might be a more mass-efficient method of acquiring the same thrust than the equivalent number of small ones.”

So it sounds like M̶u̶s̶k̶ Andy Weir is quite fine with taking the N-1 approach of many engines, and has no concerns about this  - other than mass.
Title: Re: ITS Development Updates and Discussion Thread
Post by: ncb1397 on 10/01/2016 06:45 pm
Engines can fail gracefully or catastrophically. On one of N-1s flights, an engine was shut-down demonstrating the value of having a bunch of engines that can pick up the slack. The second engine to fail on that flight failed catastrophically(the plumbing came loose), demonstrating the potential problems with so many failure points.
Title: Re: ITS Development Updates and Discussion Thread
Post by: mr2828 on 10/01/2016 11:12 pm
Here are some remarks from Musk quoted in Ars Technica:

Those quotes are from Weir.
Title: Re: ITS Development Updates and Discussion Thread
Post by: sanman on 10/01/2016 11:27 pm
Here are some remarks from Musk quoted in Ars Technica:

Those quotes are from Weir.

OOPS -- sorry, you're right  :-[

Let me EDIT that
Title: Re: ITS Development Updates and Discussion Thread
Post by: Impaler on 10/01/2016 11:44 pm
With regard to the ITS doing abort separation on the pad or in flight, it can't and won't.  Even if all engines were employed the thrust would barely exceed the stages substantial mass when full and it would barely accelerate away from the booster, to escape an exploding booster you need several G's of acceleration.

Their is also the roughly 1 second that turbo pump engines need to come up to full power, though the boosters length may provide a margin of safety here as any explosion may start farther from the spacecraft.

I can not recall any comment from Musk that the ITS will have an abort mode of any kind, in fact I seem to recall him dismissing the need by saying that commercial aircraft have no escape systems.
Title: Re: ITS Development Updates and Discussion Thread
Post by: Johnnyhinbos on 10/01/2016 11:48 pm
Is that true? The MCT / BFR / ITS Section 2 / whatever would not have a fuel/O2 load. Instead it would have just the abort  quantity.
Title: Re: ITS Development Updates and Discussion Thread
Post by: Impaler on 10/02/2016 12:03 am
It wouldn't reach orbit without a full propellant load.
Title: Re: ITS Development Updates and Discussion Thread
Post by: Robotbeat on 10/02/2016 12:37 am
It wouldn't reach orbit without a full propellant load.
It could, however, possibly land somewhere after bleeding off propellant on the way down. If you can find someplace to land. Also, even landing on water may provide some possibility of survival of the crew (although the vehicle would probably be damaged or even break up after falling over after water-landing)
Title: Re: ITS Development Updates and Discussion Thread
Post by: Robotbeat on 10/02/2016 12:37 am
There was one high-altitude abort, and I don't believe it used the LAS.
Title: Re: ITS Development Updates and Discussion Thread
Post by: gongora on 10/02/2016 01:14 am
Tweet from @futuregames, retweeted by Elon (https://twitter.com/futuregames/status/782325951753547776)
Quote
modelled the Interplanetary Transport System in @KerbalSpaceP & can confirm that @elonmusk's centre gimbal stack works... in RSS/RO

Has there been discussion in any of these threads about that center engine group on the booster?  The seven engines are mounted to something that gimbals all of them together?
Title: Re: ITS Development Updates and Discussion Thread
Post by: envy887 on 10/02/2016 01:27 am
Musk said the BFS can "take care of itself" if the booster fails in flight.

I don't know that outrunning a booster explosion would be possible, but I'd really be worried about the booster tanks separating like the LH2 tank on Challenger, blowing forward and crushing the upper stage engines. Or a loss of control authority leading to aerodynamic forces breaking up the ship.

As long as the ship is aerodynamically stable, it should be reasonably likely to survive a booster deflagration in flight, which is considerable more likely than an actual explosion.
Title: Re: ITS Development Updates and Discussion Thread
Post by: Robotbeat on 10/02/2016 02:34 am
Musk said the BFS can "take care of itself" if the booster fails in flight.

I don't know that outrunning a booster explosion would be possible, but I'd really be worried about the booster tanks separating like the LH2 tank on Challenger, blowing forward and crushing the upper stage engines. Or a loss of control authority leading to aerodynamic forces breaking up the ship.

As long as the ship is aerodynamically stable, it should be reasonably likely to survive a booster deflagration in flight, which is considerable more likely than an actual explosion.
SRBs can't be shut down. Liquid engines easily can. You can assume that in a major failure, the engines will be shut down.
Title: Re: ITS Development Updates and Discussion Thread
Post by: Zed_Noir on 10/02/2016 07:31 am
Anyone think a 3-stage ITS  is worthwhile for outer system missions?

Stripped down the ITS SC to 3 Raptor Vac and remove the crew & cargo sections as expendable second stage.

Have a third stage with dual solar and nuclear (RTG) powered electric propulsion. With the solar arrays being jettison after the stack gets beyond Jupiter's orbital distance.
Title: Re: ITS Development Updates and Discussion Thread
Post by: Xentry on 10/02/2016 10:11 am
(...)
While it's true that the American Colonies did not lead to the development of Caravels or even other significantly more advanced ships, I think this view is too focused. It's certainly true that the American Colonies and trade in the Indies were the lucky beneficiaries of other forcing functions, such as the African trade mentioned above. However, once established, these initially-dubious ventures themselves became forcing functions for better technologies
Trade with Africa wasn't but the entree; Portugal's Prince Henry, and later his nephew John II (also known as the Perfect Prince and one of the most celebrated figures in the history of the country) were relentless in their multi-decade search for a maritime route to India. You might as well call India Mars to Africa's Moon. However, having established trade with India, Portugal had to quickly develop new kinds of vessels, since getting there involved basically crossing the Atlantic all the way to Brazil and then enter the Indian Ocean directly past the southern coast of Africa, in order to avoid the delay caused by strong southern winds near the Cape.
So the Portuguese in fact ended up having to develop much larger ships to carry out the trade with the Indias - by the time that trade with the Americas became profitable in the 1550s (with the discovery of the world's largest silver mine at Potosi in Peru), both Portuguese and Spanish galleons had been travelling the seas for about half a century.
With respect to SpaceX's Mars plans it appears that, by putting the problem in terms of what it takes to colonize Mars with 1 million people, as opposed to incrementally develop a system with initially limited capabilities, they want to build the "Mars galleon" directly without ever trying to learn anything from the corresponding caravelle.
I wish them luck and hope for the best; nevertheless, there will be consequences to the whole enterprise in the form of added risk.
Title: Re: ITS Development Updates and Discussion Thread
Post by: AncientU on 10/02/2016 01:02 pm
There is added risk in the incremental approach, too, as attested to by our failure to persist long enough at the task over the last five decades.

A couple examples where incrementalism falls short:
1. Building up a significant electric automobile population -- constrained by World's total production of batteries and the cost of those batteries in high demand.  This is analogous to the limitations of the existing launch capabilities when a massive tonnage to TMI is needed.  Musk built a giga-factory... people laughed at the scale.
2. Building the Golden Gate Bridge -- incrementalism isn't ever going to get the job done.  All in or nothing sometimes are the only options.  We built the bridge in 1937 (in the depths of the Depression) for far less than the estimates at the time by employing innovative technology.
Title: Re: ITS Development Updates and Discussion Thread
Post by: DJPledger on 10/02/2016 01:56 pm
Engines can fail gracefully or catastrophically. On one of N-1s flights, an engine was shut-down demonstrating the value of having a bunch of engines that can pick up the slack. The second engine to fail on that flight failed catastrophically(the plumbing came loose), demonstrating the potential problems with so many failure points.
Looks like each Raptor has a blast shield that completely encases everything upstream of the throat so if one did explode then it would likely be contained saving the booster.
Title: Re: ITS Development Updates and Discussion Thread
Post by: dror on 10/02/2016 03:06 pm
From the slideshow -

"Spreading the required lift capacity across
multiple launches substantially reduces
development costs and compresses schedule

Combined with reusability, refilling makes
performance shortfalls an incremental rather
than exponential cost increase"


I strongly feel that the size of ITS contradicts Elon's statement:

A 4 times smaller Raptor powered system could have fulfilled all of BFR's goals with lower development costs and risks and more flights to amortize costs. Also it would be easier to incorporate with other, more terrestrial uses, and could be developed incrementally.
Later, as the 'forcing function' is established, a full scale ITS can be developed  if and when needed.

More so, The numbers 100 passengers  and 100 tons which where stated as design goals are arbitrary and even Elon has stated that ITS is too big for those numbers, stating that 200-300 passengers are probable later with ITS.
Title: Re: ITS Development Updates and Discussion Thread
Post by: Anabasis on 10/02/2016 07:31 pm
First of, a quick Hello! :)  My first post here, altough I have been following the forum for quite a while.

I'll start off with a question:

According to the presentation slides the ITS's dry mass is 150,000 kg. Compared to roughly 78,000 (http://www.esa.int/Our_Activities/Human_Spaceflight/Space_Shuttle/Shuttle_technical_facts) kg for the Space Shuttle Orbiter.

Now considering the size (100 vs 8 crew) and required capability differences (LEO vs Mars)...


How is that going to work?
Title: Re: ITS Development Updates and Discussion Thread
Post by: GalacticIntruder on 10/02/2016 07:56 pm
From the slideshow -

"Spreading the required lift capacity across
multiple launches substantially reduces
development costs and compresses schedule

Combined with reusability, refilling makes
performance shortfalls an incremental rather
than exponential cost increase"


I strongly feel that the size of ITS contradicts Elon's statement:

A 4 times smaller Raptor powered system could have fulfilled all of BFR's goals with lower development costs and risks and more flights to amortize costs. Also it would be easier to incorporate with other, more terrestrial uses, and could be developed incrementally.
Later, as the 'forcing function' is established, a full scale ITS can be developed  if and when needed.

More so, The numbers 100 passengers  and 100 tons which where stated as design goals are arbitrary and even Elon has stated that ITS is too big for those numbers, stating that 200-300 passengers are probable later with ITS.

It just means, for Musk's goal of COLONIZATION, they designed the vehicle to have so much margin with in-space refueling, that it can accomplish the mission without having to achieve perfection on their metrics--- like mass, power, dV etc. They can massage performance over time, and not have to build a new, larger craft. Even if the first gen ITS can only can do 80 percent, it still good enough.  Remember the first F9 and Dragon could not achieve their ISS contracts, so they had to do costly upgrades, and are still doing upgrades.
Title: Re: ITS Development Updates and Discussion Thread
Post by: Space Ghost 1962 on 10/02/2016 08:04 pm
Contrasting Musk with Bezos.

The highly specific goal that Musk has with SX has led to a tightly focused, purpose driven ITS.

The nonspecific goal that Bezos has with BO has lead to a progression of LV's described that heads them on a path, with growth and a vague notion of "end point".

Yet Musks F9 seemed to be "all over the map" in everything from reuse all the way to RD on Mars.

While Bezo's New Shepard was an tightly focused , purpose driven space tourist suborbital business.

One sort of functions but has issues. The other seems to gradually be "standing up".

Interesting how they overtake each other and exchange attributes.
Title: Re: ITS Development Updates and Discussion Thread
Post by: Robotbeat on 10/03/2016 03:26 am
A good enough LAS would also mitigate the leg "issue."

Musk mentioned the idea of flying crew up separately (in another spaceship?) to the spaceship in case refueling takes longer than they're currently expecting. In that case, LAS could be provided for that leg of the trip without impacting the mass on the rest of the trip.

LAS is something that could be developed using the enormous mass budget available with the spaceship. But is it the best use of funds for SpaceX at this moment?
Title: Re: ITS Development Updates and Discussion Thread
Post by: Hyperion5 on 10/03/2016 03:31 am
A good enough LAS would also mitigate the leg "issue."

Musk mentioned the idea of flying crew up separately (in another spaceship?) to the spaceship in case refueling takes longer than they're currently expecting. In that case, LAS could be provided for that leg of the trip without impacting the mass on the rest of the trip.

LAS is something that could be developed using the enormous mass budget available with the spaceship. But is it the best use of funds for SpaceX at this moment?

Chris, how would a leg failure upon Mars arrival be mitigated by LAS?  The vehicle excepting a crew module with LAS would be a complete loss, and a completely unnecessary 200 million dollar+ one at that.  Unless there's a spare ITS laying around, the crew could be stranded a whole cycle on Mars or worse.  How would adding a pair of legs to this design possibly not be worth it to Spacex?  The benefits to crew & vehicle safety are massive compared to the mass penalty costs you would incur. 
Title: Re: ITS Development Updates and Discussion Thread
Post by: Robotbeat on 10/03/2016 03:47 am
There may only be a single synod where only one ITS is on Mars. Within one or two synods, plenty of resources to rescue a downed crew.

This isn't Apollo. Mars will be populated quickly (or not at all).
Title: Re: ITS Development Updates and Discussion Thread
Post by: Elladan on 10/03/2016 05:06 am
You can have redundancy in the leg deployment mechanism without having actual redundant legs, I think. For example, redundant hydraulic mechanisms with isolated lines.
Title: Re: ITS Development Updates and Discussion Thread
Post by: MP99 on 10/03/2016 05:08 am




Gas is circulated back to the cryocooler, where it is liquefied and returned to the tank.

Cheers, Martin

Where would the cryo-cooler put the heat? One way or another I think they will need some sun shaded radiator panels.

I was responding to "it's a long way back to the cryocooler", not "there is no cryocooler".

I'm assuming that crew compartment points towards the Sun, and prop tanks away, though I'm surprised not to see some sort of sunshield, however small, for the crew compartment.

Cheers, Martin
Title: Re: ITS Development Updates and Discussion Thread
Post by: x15_fan on 10/03/2016 05:24 am
You can have redundancy in the leg deployment mechanism without having actual redundant legs, I think. For example, redundant hydraulic mechanisms with isolated lines.

Landing gear on shuttle deployed via hydraulic, gravity and pyrotechnic as backup, every time (whether needed or not). So deployment redundancy is possible and failure to lock (we've seen that movie before) also could be made redundant. still would be concern around coping with a mechanical jam (especially early on) that deployment redundancy can't overcome or some kind of fouled landing location which compromises a leg.
Title: Re: ITS Development Updates and Discussion Thread
Post by: winkhomewinkhome on 10/03/2016 05:44 am
Thinking out loud...

As the ITS comes in to land the gear deploys and locks, sensors confirm, ITS lands and engines shut down...

As the ITS comes in to land the gear deploys and one leg or another fails in some mode, and...?

ITS throttles up and returns to orbit?  Doubtful due to lack of fuel reserves...?

Would the ITS be built robust enough to simply layover without a RUD resulting.  Aircraft manage to land everyday of the week without a full set of gear..."any landing you can walk away from" philosophy??
Title: Re: ITS Development Updates and Discussion Thread
Post by: Lars-J on 10/03/2016 06:03 am
Contrasting Musk with Bezos.

The highly specific goal that Musk has with SX has led to a tightly focused, purpose driven ITS.

The nonspecific goal that Bezos has with BO has lead to a progression of LV's described that heads them on a path, with growth and a vague notion of "end point".

Yet Musks F9 seemed to be "all over the map" in everything from reuse all the way to RD on Mars.

While Bezo's New Shepard was an tightly focused , purpose driven space tourist suborbital business.

One sort of functions but has issues. The other seems to gradually be "standing up".

Interesting how they overtake each other and exchange attributes.

The difference can be attributes largely to funding resources... Musk has a specific focus, but needs to diversify to raise capital to accomplish his end vision. Bezos can fund himself entirely, and is in no real hurry.
Title: Re: ITS Development Updates and Discussion Thread
Post by: Elladan on 10/03/2016 06:15 am
You might imagine aborting to the ocean if a leg fails to latch on an Earth landing and you detect it soon enough.

The ship is 50 meters tall. Even if the tanks didn't explode I think you're having a bad day if it falls over on land.

With the tanks empty it looks top heavy too.
Title: Re: ITS Development Updates and Discussion Thread
Post by: Lars-J on 10/03/2016 06:16 am
Here is something I doodled up, to see how the internal decks would be used in an ITS lander/ship.  :)
(based on the assumption that the cargo decks are unpresssurized, as the schematics seem to imply)

(Mods, feel free to move to another thread if this is in the wrong place)

I have also attached the schematic I used as reference.
Title: Re: ITS Development Updates and Discussion Thread
Post by: cartman on 10/03/2016 06:28 am
The ITS has internal tanks for its landing fuel. Wouldn't that minimize the amount of propellant in the outer tanks during the landing burns, thus making a possible breach of them more survivable? They could even empty the tanks during the voyage to Mars, possibly filling them with an inert gas.
Title: Re: ITS Development Updates and Discussion Thread
Post by: Impaler on 10/03/2016 06:31 am

The difference can be attributes largely to funding resources... Musk has a specific focus, but needs to diversify to raise capital to accomplish his end vision. Bezos can fund himself entirely, and is in no real hurry.

The need for Musk to keep SpaceX commercially viable should logically have driven him to make the smaller more practical vehicle capable of serving existing markets, something 'only' equivalent to one or perhaps 2 Saturn V's, or at the least to apply the new tech to upgrading their existing vehicles to keep them competitive.  It now looks like New Glen is the vehicle best targeted at existing markets and near term potential markets like LEO tourism.

I think the difference is that Musk has eyes only for Mars and Bezos is destination agnostic outside of 'space' broadly.  That and Musk personally has a greater need to see results quickly and within his own lifetime.
Title: Re: ITS Development Updates and Discussion Thread
Post by: TheTraveller on 10/03/2016 10:31 am
Here is something I doodled up, to see how the internal decks would be used in an ITS lander/ship.  :)
(based on the assumption that the cargo decks are unpresssurized, as the schematics seem to imply)

(Mods, feel free to move to another thread if this is in the wrong place)

I have also attached the schematic I used as reference.

Nice graphic Lars.

Here is one of many possible cabin layouts.
Title: Re: ITS Development Updates and Discussion Thread
Post by: JamesH65 on 10/03/2016 10:49 am

The difference can be attributes largely to funding resources... Musk has a specific focus, but needs to diversify to raise capital to accomplish his end vision. Bezos can fund himself entirely, and is in no real hurry.

The need for Musk to keep SpaceX commercially viable should logically have driven him to make the smaller more practical vehicle capable of serving existing markets, something 'only' equivalent to one or perhaps 2 Saturn V's, or at the least to apply the new tech to upgrading their existing vehicles to keep them competitive.  It now looks like New Glen is the vehicle best targeted at existing markets and near term potential markets like LEO tourism.

I think the difference is that Musk has eyes only for Mars and Bezos is destination agnostic outside of 'space' broadly.  That and Musk personally has a greater need to see results quickly and within his own lifetime.

Not sure I agree. He is proposing, presumably, the smallest project that achieves the required aims. So why produce something smaller* for existing markets when the F9 and F9H should serve them and keep them commercial?

* But still bigger than any current requirements whilst industry catches up with the new capabilities.
Title: Re: ITS Development Updates and Discussion Thread
Post by: Johnnyhinbos on 10/03/2016 10:56 am
As a reference, here's what a 18m^2 living space looks like. Personally I would turn each segment sideways and move the common corridor towards the center. This would increase number of cabins.

https://www.youtube.com/watch?v=mDPvW50VHmY
Title: Re: ITS Development Updates and Discussion Thread
Post by: TheTraveller on 10/03/2016 12:05 pm
Here are 10 cabins per floor, varying from 2 pax per cabin to 8 pax per cabin.

Can handle 50 pax and 2 crew per floor with some common space outside the cabins plus a zero G toilet and shower.

Many modifications are possible.
Title: Re: ITS Development Updates and Discussion Thread
Post by: philw1776 on 10/03/2016 12:14 pm
Having 50+ people waiting to use the not quick to use zero gee toilet upon arising is NOT a good idea
Title: Re: ITS Development Updates and Discussion Thread
Post by: TheTraveller on 10/03/2016 12:54 pm
Having 50+ people waiting to use the not quick to use zero gee toilet upon arising is NOT a good idea

Happens all the time on long haul international flights when the movie / meal ends and 350 pax all need to go. OK probably do need a few more toilet facilities that 1 per 52 pax.

Added a few more toilets and showers. Would suspect daily showering may be a strict requirement.
Title: Re: ITS Development Updates and Discussion Thread
Post by: rsdavis9 on 10/03/2016 01:03 pm
So I didn't see it specifically mentioned.
So will they also have the cargo ITS be able to deliver satellites etc to LEO and GEO.
It would probably only take 1 or 2 flights per year to deliver what is currently planned from all customers.
The cargo ITS would just be outfitted with a different internal seat layout.(too use the airline industry metaphor). No redesign of any rocket or on orbit hardware.
Title: Re: ITS Development Updates and Discussion Thread
Post by: rsdavis9 on 10/03/2016 01:22 pm
So I didn't see it specifically mentioned.
So will they also have the cargo ITS be able to deliver satellites etc to LEO and GEO.
It would probably only take 1 or 2 flights per year to deliver what is currently planned from all customers.
The cargo ITS would just be outfitted with a different internal seat layout.(too use the airline industry metaphor). No redesign of any rocket or on orbit hardware.

It looks like my question is discussed in this thread:
http://forum.nasaspaceflight.com/index.php?topic=41084.0
Title: Re: ITS Development Updates and Discussion Thread
Post by: Lars-J on 10/03/2016 03:55 pm
Having 50+ people waiting to use the not quick to use zero gee toilet upon arising is NOT a good idea

Happens all the time on long haul international flights when the movie / meal ends and 350 pax all need to go. OK probably do need a few more toilet facilities that 1 per 52 pax.

Added a few more toilets and showers. Would suspect daily showering may be a strict requirement.

Actually, no. The ISS crew doesn't shower, they only wipe themselves down. (not sure how often) But apparently the body seems to perspire less in micro-gravity. I would not expect *ANY* showers onboard, the mass and water usage would be large. (And how would a shower work?)
Title: Re: ITS Development Updates and Discussion Thread
Post by: TheTraveller on 10/03/2016 04:07 pm
Having 50+ people waiting to use the not quick to use zero gee toilet upon arising is NOT a good idea

Happens all the time on long haul international flights when the movie / meal ends and 350 pax all need to go. OK probably do need a few more toilet facilities that 1 per 52 pax.

Added a few more toilets and showers. Would suspect daily showering may be a strict requirement.

Actually, no. The ISS crew doesn't shower, they only wipe themselves down. (not sure how often) But apparently the body seems to perspire less in micro-gravity. I would not expect *ANY* showers onboard, the mass and water usage would be large. (And how would a shower work?)

Surly ALL water used on BFS and on Mars would be recycled?

As for the shower, building a zero G discharge of water drops only need a bit of pressure and passage from head to feet of the water drops is just differential air pressure.

There will be 100 pax plus crew enclosed in a space for 4-6 months. Don't know if wipes would keep the BO pong to an acceptable level.
Title: Re: ITS Development Updates and Discussion Thread
Post by: Eerie on 10/03/2016 04:17 pm
Actually, no. The ISS crew doesn't shower, they only wipe themselves down. (not sure how often) But apparently the body seems to perspire less in micro-gravity. I would not expect *ANY* showers onboard, the mass and water usage would be large. (And how would a shower work?)

Mir used to have a shower.
Title: Re: ITS Development Updates and Discussion Thread
Post by: Negan on 10/03/2016 04:19 pm
Actually, no. The ISS crew doesn't shower, they only wipe themselves down. (not sure how often) But apparently the body seems to perspire less in micro-gravity. I would not expect *ANY* showers onboard, the mass and water usage would be large. (And how would a shower work?)

Mir used to have a shower.

Skylab also had one.
Title: Re: ITS Development Updates and Discussion Thread
Post by: envy887 on 10/03/2016 04:20 pm
The ITS has internal tanks for its landing fuel. Wouldn't that minimize the amount of propellant in the outer tanks during the landing burns, thus making a possible breach of them more survivable? They could even empty the tanks during the voyage to Mars, possibly filling them with an inert gas.

Not much point in filling them with anything. Scavenge the residual propellent for landing and thrusters, and leave the main tanks vented to hard vacuum/Mars atmosphere/earth atmosphere.
Title: Re: ITS Development Updates and Discussion Thread
Post by: Lars-J on 10/03/2016 04:39 pm
Actually, no. The ISS crew doesn't shower, they only wipe themselves down. (not sure how often) But apparently the body seems to perspire less in micro-gravity. I would not expect *ANY* showers onboard, the mass and water usage would be large. (And how would a shower work?)

Mir used to have a shower.

Skylab also had one.

I stand corrected. But ISS certainly does not have one, and people have been up there for a year at a time. Showers are not a necessity, and this is not going to that kind of luxury cruise.
Title: Re: ITS Development Updates and Discussion Thread
Post by: TheTraveller on 10/03/2016 05:06 pm
Stacking the bunks beds x3 would boost free floor space as you could then fit 6 pax in a 4 pax cabin and 9 pax in a 6 pax cabin.

These images have 9 beds in a 3x3m (9m^2) space. History has proven that sort of sleeping space does work. From the images, I could do 4-6 months sleeping in space in a bunk that size. Which says a lot more than 50 pax could fit on each of the BFS 2 accommodation floors.
Title: Re: ITS Development Updates and Discussion Thread
Post by: Kansan52 on 10/03/2016 05:33 pm
From a Smithsonian 2014 article:

"Before the dirty laundry can be ejected into space, it has a tendency to pile up. According to NASA, all of these dirty garments can cause storage and weight problems, and lint from cotton fibres can clog filters. Then, there's the smell.

A new NASA study is looking to reduce the amount of clothing waste by extending the amount of time astronauts' garments can be worn. As part of the study, ISS crew members are being provided with exercise clothing that's been treated with an antimicrobial compound, or made with antimicrobial yarn.

Yesterday, a privately operated resupply mission took off from the Virginia coast carrying resupply materials, including the new clothes. As per NASA, astronauts will wear the clothes during their daily two and a half hour exercise regimen for a total of 15 days."

So, yes, smell and weight and volume and filter clogging, ect are all things that's on the list.
Title: Re: ITS Development Updates and Discussion Thread
Post by: Elvis in Space on 10/03/2016 05:46 pm
Actually, no. The ISS crew doesn't shower, they only wipe themselves down. (not sure how often) But apparently the body seems to perspire less in micro-gravity. I would not expect *ANY* showers onboard, the mass and water usage would be large. (And how would a shower work?)

Mir used to have a shower.

Skylab also had one.

Yes but I believe the Astronauts were limited to 2 quarts of water per shower once per week. I think it was as much an experiment as anything. I've roughed it in the woods for days on end and I'm not sure I'd notice a two liter shower once a week.
Title: Re: ITS Development Updates and Discussion Thread
Post by: TheTraveller on 10/03/2016 05:50 pm
Actually, no. The ISS crew doesn't shower, they only wipe themselves down. (not sure how often) But apparently the body seems to perspire less in micro-gravity. I would not expect *ANY* showers onboard, the mass and water usage would be large. (And how would a shower work?)

Mir used to have a shower.

Skylab also had one.

Yes but I believe the Astronauts were limited to 2 quarts of water per shower once per week. I think it was as much an experiment as anything. I've roughed it in the woods for days on end and I'm not sure I'd notice a two liter shower once a week.

Sure but the other 99 pax + crew in the BFS may notice. Would assume all the shower and other grey water would processed and recycled. The more solid wastes may be reused as Watney reused them.
Title: Re: ITS Development Updates and Discussion Thread
Post by: Eerie on 10/03/2016 06:12 pm
People used to go to years long sailing voyages without any showers at all. You can definitely get used to the smell.

In fact, this is one way to winnow out the weak-willed colonists. Just add a couple of months stay in closed quarters without showers and without complaining.
Title: Re: ITS Development Updates and Discussion Thread
Post by: Lars-J on 10/03/2016 06:27 pm
People used to go to years long sailing voyages without any showers at all. You can definitely get used to the smell.

In fact, this is one way to winnow out the weak-willed colonists. Just add a couple of months stay in closed quarters without showers and without complaining.

Yep... If you are colonizing Mars, you will have to get used to some odors. It will be cramped on the ITS, but that is just a warm-up for life on Mars.
Title: Re: ITS Development Updates and Discussion Thread
Post by: Robotbeat on 10/03/2016 06:28 pm
Did any of you watch Musk's IAC presentation? He seemed intent on making it look like a luxury cruise.

If he is putting a huge ass window in the front of the ship, you can bet there will be showers of some sort.

I wouldn't bother. I'd also force everyone to eat Soylent and take drugs to extend their sleeping hours to 20h/ day if not full torpor/hibernation (so you could stack the passengers like firewood).

But this is Musk he wants as many people to want to go as possible while still making it affordable. There will be showers.
Title: Re: ITS Development Updates and Discussion Thread
Post by: pobermanns on 10/03/2016 06:34 pm
Musk mentioned the idea of flying crew up separately (in another spaceship?) to the spaceship in case refueling takes longer than they're currently expecting. In that case, LAS could be provided for that leg of the trip without impacting the mass on the rest of the trip.
If the pax were sent up separately, would there be any other things which could be stripped down? At first I was thinking about launch-worthy crash couches, but then again those'd be needed for the arrival at Mars, launch from Mars and especially arrival back at Earth. But, might there be something else for which the weight could be saved?
Title: Re: ITS Development Updates and Discussion Thread
Post by: Robotbeat on 10/03/2016 06:38 pm
You could do SSTO with the short-term passenger version of the ITS spaceship, in addition to some sort of LAS. Probably not enough mass to do more.
Title: Re: ITS Development Updates and Discussion Thread
Post by: high road on 10/03/2016 06:47 pm
Stacking the bunks beds x3 would boost free floor space as you could then fit 6 pax in a 4 pax cabin and 9 pax in a 6 pax cabin.

These images have 9 beds in a 3x3m (9m^2) space. History has proven that sort of sleeping space does work. From the images, I could do 4-6 months sleeping in space in a bunk that size. Which says a lot more than 50 pax could fit on each of the BFS 2 accommodation floors.

So with an outer ring fully occupied by beds stacked three high, there would be room for almost a hundred people. Maybe substract a ring around the edge to store the supplies, for radiation protection.

Considering that there is no day/night cycle in space, the crew could rotate using the beds, limiting both the number of people in the 'bedroom' and in the comon areas at any given time..

Just a thought on the bed: if there's no gravity to hold you down, wouldn't the headspace appear smaller?

And we're still lacking a galley. Preparing food, even if it's just microwaving prepackaged food, on such a small space will be no small feat. So I'm guessing people will rotate eating as well so there's only 3 out of every 24 to 48 people eating at any given time. Lots of space saved.
Title: Re: ITS Development Updates and Discussion Thread
Post by: pobermanns on 10/03/2016 06:53 pm
Here is something I doodled up, to see how the internal decks would be used in an ITS lander/ship.  :)
(based on the assumption that the cargo decks are unpresssurized, as the schematics seem to imply)

(Mods, feel free to move to another thread if this is in the wrong place)

I have also attached the schematic I used as reference.

Nice graphic Lars.

Here is one of many possible cabin layouts.
I tried to find the volume and dimensions of the sleeping cubicles in use on the ISS, but zilch. Any idea on that, and whether such cubicles could be useful in your layout?
Title: Re: ITS Development Updates and Discussion Thread
Post by: pobermanns on 10/03/2016 07:12 pm
People used to go to years long sailing voyages without any showers at all. You can definitely get used to the smell.

In fact, this is one way to winnow out the weak-willed colonists. Just add a couple of months stay in closed quarters without showers and without complaining.

Yep... If you are colonizing Mars, you will have to get used to some odors. It will be cramped on the ITS, but that is just a warm-up for life on Mars.
Indeed!

Being aboard ship, I always found that my nose became desensitized to BO. Maybe it was just me, but I rather think all of the guys became oblivious to it. Water-hours - which were common on some ships I cruised on, made it hard even to take a "Navy shower".
Title: Re: ITS Development Updates and Discussion Thread
Post by: pobermanns on 10/03/2016 07:15 pm
Did any of you watch Musk's IAC presentation? He seemed intent on making it look like a luxury cruise.

If he is putting a huge ass window in the front of the ship, you can bet there will be showers of some sort.

I wouldn't bother. I'd also force everyone to eat Soylent and take drugs to extend their sleeping hours to 20h/ day if not full torpor/hibernation (so you could stack the passengers like firewood).

But this is Musk he wants as many people to want to go as possible while still making it affordable. There will be showers.
You may be totally right about the luxury idea. However, I was thinking that that is an aspiration, not a hard goal. For sure, at this early stage of development most of the hard engineering choices have not yet been made, so we'll just have to wait and see.
Title: Re: ITS Development Updates and Discussion Thread
Post by: ZachF on 10/03/2016 07:16 pm
Did any of you watch Musk's IAC presentation? He seemed intent on making it look like a luxury cruise.

If he is putting a huge ass window in the front of the ship, you can bet there will be showers of some sort.

I wouldn't bother. I'd also force everyone to eat Soylent and take drugs to extend their sleeping hours to 20h/ day if not full torpor/hibernation (so you could stack the passengers like firewood).

But this is Musk he wants as many people to want to go as possible while still making it affordable. There will be showers.

hahaha
Title: Re: ITS Development Updates and Discussion Thread
Post by: pobermanns on 10/03/2016 07:18 pm
Stacking the bunks beds x3 would boost free floor space as you could then fit 6 pax in a 4 pax cabin and 9 pax in a 6 pax cabin.

These images have 9 beds in a 3x3m (9m^2) space. History has proven that sort of sleeping space does work. From the images, I could do 4-6 months sleeping in space in a bunk that size. Which says a lot more than 50 pax could fit on each of the BFS 2 accommodation floors.
Another option is to use "hot bunking", like aboard nuke subs. Gross, but it works.
Title: Re: ITS Development Updates and Discussion Thread
Post by: Lars-J on 10/03/2016 07:51 pm
Here is something I doodled up, to see how the internal decks would be used in an ITS lander/ship.  :)
(based on the assumption that the cargo decks are unpresssurized, as the schematics seem to imply)

(Mods, feel free to move to another thread if this is in the wrong place)

I have also attached the schematic I used as reference.

Nice graphic Lars.

Here is one of many possible cabin layouts.
I tried to find the volume and dimensions of the sleeping cubicles in use on the ISS, but zilch. Any idea on that, and whether such cubicles could be useful in your layout?

Your answers are here: http://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/20080013462.pdf

ISS bunks have a volume of ~2 cubic meters.

One complication for the ITS is that each passenger/crew needs to have their own chair/couch for handle launch and landing. Incorporating that into the cabins probably makes sense. But those chairs will probably need to swivel a bit to handle the 'flip' maneuver before landing. This will take up some more space.
Title: Re: ITS Development Updates and Discussion Thread
Post by: AncientU on 10/03/2016 07:52 pm
Stacking the bunks beds x3 would boost free floor space as you could then fit 6 pax in a 4 pax cabin and 9 pax in a 6 pax cabin.

These images have 9 beds in a 3x3m (9m^2) space. History has proven that sort of sleeping space does work. From the images, I could do 4-6 months sleeping in space in a bunk that size. Which says a lot more than 50 pax could fit on each of the BFS 2 accommodation floors.
Another option is to use "hot bunking", like aboard nuke subs. Gross, but it works.

Not really.
Been there, done that.
Title: Re: ITS Development Updates and Discussion Thread
Post by: cro-magnon gramps on 10/03/2016 07:53 pm
Did any of you watch Musk's IAC presentation? He seemed intent on making it look like a luxury cruise.

If he is putting a huge ass window in the front of the ship, you can bet there will be showers of some sort.

I wouldn't bother. I'd also force everyone to eat Soylent and take drugs to extend their sleeping hours to 20h/ day if not full torpor/hibernation (so you could stack the passengers like firewood).

But this is Musk he wants as many people to want to go as possible while still making it affordable. There will be showers.

hahaha

So Sleeping Drawers (aka PJ's) might take on a whole new meaning; picture a morgue, just a tad more comfortable base  ::)
Title: Re: ITS Development Updates and Discussion Thread
Post by: pobermanns on 10/03/2016 09:01 pm
Stacking the bunks beds x3 would boost free floor space as you could then fit 6 pax in a 4 pax cabin and 9 pax in a 6 pax cabin.

These images have 9 beds in a 3x3m (9m^2) space. History has proven that sort of sleeping space does work. From the images, I could do 4-6 months sleeping in space in a bunk that size. Which says a lot more than 50 pax could fit on each of the BFS 2 accommodation floors.
Another option is to use "hot bunking", like aboard nuke subs. Gross, but it works.
Not really.
Been there, done that.
Yeah, no argument with that :o. The 'bubbleheads' that I knew hated it. It was just a suggestion.
Title: Re: ITS Development Updates and Discussion Thread
Post by: ThereIWas3 on 10/03/2016 09:02 pm
Talking about 'floor space' indicates a lack of thinking in 3 dimensions.   :)  Which way is 'down' will matter for about 15 minutes out of a 100 day flight.

Millions to the person who perfects an efficient zero-G shower.
Title: Re: ITS Development Updates and Discussion Thread
Post by: pobermanns on 10/03/2016 09:14 pm
Here is something I doodled up, to see how the internal decks would be used in an ITS lander/ship.  :)
(based on the assumption that the cargo decks are unpresssurized, as the schematics seem to imply)

(Mods, feel free to move to another thread if this is in the wrong place)

I have also attached the schematic I used as reference.

Nice graphic Lars.

Here is one of many possible cabin layouts.
I tried to find the volume and dimensions of the sleeping cubicles in use on the ISS, but zilch. Any idea on that, and whether such cubicles could be useful in your layout?

Your answers are here: http://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/20080013462.pdf

ISS bunks have a volume of ~2 cubic meters.

One complication for the ITS is that each passenger/crew needs to have their own chair/couch for handle launch and landing. Incorporating that into the cabins probably makes sense. But those chairs will probably need to swivel a bit to handle the 'flip' maneuver before landing. This will take up some more space.
Would there be a way of having the launch couch and sleeping cubicle integrated? Otherwise the launch couch will only get use during two launches and two landings. Kind of a waste of space.
Title: Re: ITS Development Updates and Discussion Thread
Post by: JasonAW3 on 10/03/2016 09:21 pm
Talking about 'floor space' indicates a lack of thinking in 3 dimensions.   :)  Which way is 'down' will matter for about 15 minutes out of a 100 day flight.

Millions to the person who perfects an efficient zero-G shower.

How about a "Bath Bag"?

      Essentially, a large bag that a person would get into, sticking their head out through a hole that has elastic around it to "seal" it and a water tight zip lock for the front of the bag.

      A small amount of water, maybe a liter, would be injected into the bag.  The person would have a washcloth and a sort of non-rinse liquid soap and use the washcloth to clean up with.  A vacuum hose on the inside of the bag could be used to remove the majority of the water after use, (to be recycled) and the person would get out of the bag, toweling off any water still adhering to them, re-zipping the bag up, and using a hose to pump some hot air into the bag through the neck hole.  As the water evaporates after a few minutes, the vacuum hose would then be used to remove the water saturated hot air from the bag, again, recycling the water.
     Face, ears and neck would be washed with wet naps, while the hair would use a non-rinse liquid soap.  (Toweling it out of the hair to remove the dirt and grime).

     The bag would either be rolled up for storage, or used by another person.
Title: Re: ITS Development Updates and Discussion Thread
Post by: ThereIWas3 on 10/03/2016 09:29 pm
A vacuum hose will only remove the water if there is a force pushing the water toward the hose.

I was thinking of something like a phone booth with a big fan on top, blowing air downward.  A fine mist of water (maybe 1 Liter) is sprayed in at the top, wafts down to the bottom where drain holes collect it, to be repumped to the top and sprayed in again.  The constant breeze prevents choking on the water, and alsy\o propells it down toward the floor.   After washing, all the now soapy water is pumped to the grey-water processing facillity and a second Liter of clear water in inserted for rinsing.  This also recycles from bottom to top.  When done, the fan continues to blow, forcing remaining water down the body to the drains which now also feed to the general grey water processing facility.
Title: Re: ITS Development Updates and Discussion Thread
Post by: cuddihy on 10/03/2016 09:35 pm
That sounds like a fungal nightmare...

This isn't an unsolvable problem, but the ISS solution isn't going to cut it. You're going to have to have laundry. It's not fun, but someone's got to do it!
Title: Re: ITS Development Updates and Discussion Thread
Post by: RoboGoofers on 10/03/2016 09:48 pm
It would make sense to remove the sleeping pods once landed. maybe also internal partitions. I'm sure the colonists will find a use for them, if one isn't planned for.

If you don't take the beds, they'll have to waste fuel to send them all the way back to earth. Also, if the cabin is reconfigurable like this, you can easily make room for more cargo/less passengers.

It would also be useful to pressurize the unpressurized cargo area. once landed and the cargo is unloaded, the bunks can be moved to the cargo area for unloading without having to bring each one through the airlock. It's also a good open space close to the cargo doors to use to assemble rovers and such.
Title: Re: ITS Development Updates and Discussion Thread
Post by: Lars-J on 10/03/2016 10:42 pm
That sounds like a fungal nightmare...

This isn't an unsolvable problem, but the ISS solution isn't going to cut it. You're going to have to have laundry. It's not fun, but someone's got to do it!

Oh there will certainly be laundry, but the shower part is what is being discussed. And while I appreciate my daily shower here on Earth, I also realize that it is a very recent development in humanity's history, and it is a LUXURY - not a necessity for being clean.
Title: Re: ITS Development Updates and Discussion Thread
Post by: meekGee on 10/03/2016 11:43 pm
That sounds like a fungal nightmare...

This isn't an unsolvable problem, but the ISS solution isn't going to cut it. You're going to have to have laundry. It's not fun, but someone's got to do it!

If you make a box with walls that wick water, you're set. You're just somewhat limited by the rate you can introduce water in the box.
Title: Re: ITS Development Updates and Discussion Thread
Post by: Robotbeat on 10/04/2016 12:23 am
"Shower in space?? Why, that's IMPOSSIBLE!"
https://www.youtube.com/watch?v=cSWsyYozdv4
Title: Re: ITS Development Updates and Discussion Thread
Post by: Lars-J on 10/04/2016 02:50 am
"Shower in space?? Why, that's IMPOSSIBLE!"
https://www.youtube.com/watch?v=cSWsyYozdv4

Yes? And clearly not necessary, since it was abandoned by ISS.
Title: Re: ITS Development Updates and Discussion Thread
Post by: Robotbeat on 10/04/2016 03:12 am
"Shower in space?? Why, that's IMPOSSIBLE!"
https://www.youtube.com/watch?v=cSWsyYozdv4

Yes? And clearly not necessary, since it was abattndoned by ISS.
And a huge ass window on a vehicle that does reentry isn't terribly necessary.

Again, did you listen to the presentation? Musk want it to be fun.

No, I wouldn't put a shower on ITS, but Musk would.
Title: Re: ITS Development Updates and Discussion Thread
Post by: GREverett on 10/04/2016 04:08 am
Would love to know what the thinking is about including actual windows on the ITS ship? They are mass inefficient and complicate the structural integrity and costs, and for most of the trip all you would see is the velvety deep black of space due to sun glare. Use of 3D, High Def. displays could be made to look like window and would show space without the glare. Or they could display anything the occupant of the stateroom wished, and be used as video component of com system. Even the forward viewing deck could be emulated with video. It just doesn’t seem to make sense to cut wholes in a perfectly good ship for an inferior viewing experience. Has anyone heard anything about why SpaceX wants to do that?
Title: Re: ITS Development Updates and Discussion Thread
Post by: Eric Hedman on 10/04/2016 04:33 am
Would love to know what the thinking is about including actual windows on the ITS ship? They are mass inefficient and complicate the structural integrity and costs, and for most of the trip all you would see is the velvety deep black of space due to sun glare. Use of 3D, High Def. displays could be made to look like window and would show space without the glare. Or they could display anything the occupant of the stateroom wished, and be used as video component of com system. Even the forward viewing deck could be emulated with video. It just doesn’t seem to make sense to cut wholes in a perfectly good ship for an inferior viewing experience. Has anyone heard anything about why SpaceX wants to do that?
Right now a lot of things are probably there to look cool to help sell this idea.  If this ever gets built there will be quite a few changes during the development process.  Losing the large windows may just be one of them.  Though I could imagine the view near Earth or on final approach to Mars might be quite spectacular through them.  And there is a psychological difference between looking directly at something or through a monitor.
Title: Re: ITS Development Updates and Discussion Thread
Post by: Craig_VG on 10/04/2016 06:02 am
@Eric

While I mostly agree, it's important to note that Elon said the models presented were based on actual CAD files and the final ship would look like the one presented.
Title: Re: ITS Development Updates and Discussion Thread
Post by: guckyfan on 10/04/2016 10:20 am
That shower arrangement does not look attractive to me. Really wet towels are more convenient IMO. For comfort they should invest into convenient toilets. I think there are improvements to be made.

Edit: You can use good towels and wipes when you have washing machines on board. Another convenience worth investing in.
Title: Re: ITS Development Updates and Discussion Thread
Post by: Stan-1967 on 10/04/2016 11:21 am
That sounds like a fungal nightmare...

This isn't an unsolvable problem, but the ISS solution isn't going to cut it. You're going to have to have laundry. It's not fun, but someone's got to do it!

If you make a box with walls that wick water, you're set. You're just somewhat limited by the rate you can introduce water in the box.

This is the right concept.  I am thinking of a larger cylindrical or perhaps sectioned cone that has an inner perforated wall that makes a cage within the larger cone/cylinder section.  Water & air is sprayed out from a tube running up the centerline.   Air flow and water flow will push water droplets towards the outer wall, through the perforated wall, which then collects and wicks the water to a spot where it can be captured in a close looped system to remove contaminants/dirt and then go through a purify & recycle system.  You could even throw in a slow rpm spin dry cycle at the end.   It's more like a car wash for humans than what we we think of as a shower.  It will also work in .38 g on mars, or any other body in the solar system.

I think showering will need to be efficient with so many people on board.  One really great YUUGE shower for everyone.  No shyness allowed.   Basically the space monkeys (errr..mars colonists) go into the shower 10-15 at a time, and get hosed down.   

I'm calling it the "Get Wright Space Shower" (tm).  My little contribution to the Musk space ecosystem.  It is true that to as high a degree as possible, the standard of living on the ship is a selling point.  I'm already thinking of the commercials!  I'm casting the best looking hollywood actresses for the product launch.
Title: Re: ITS Development Updates and Discussion Thread
Post by: TheTraveller on 10/04/2016 12:41 pm
That sounds like a fungal nightmare...

This isn't an unsolvable problem, but the ISS solution isn't going to cut it. You're going to have to have laundry. It's not fun, but someone's got to do it!

If you make a box with walls that wick water, you're set. You're just somewhat limited by the rate you can introduce water in the box.

This is the right concept.  I am thinking of a larger cylindrical or perhaps sectioned cone that has an inner perforated wall that makes a cage within the larger cone/cylinder section.  Water & air is sprayed out from a tube running up the centerline.   Air flow and water flow will push water droplets towards the outer wall, through the perforated wall, which then collects and wicks the water to a spot where it can be captured in a close looped system to remove contaminants/dirt and then go through a purify & recycle system.  You could even throw in a slow rpm spin dry cycle at the end.   It's more like a car wash for humans than what we we think of as a shower.  It will also work in .38 g on mars, or any other body in the solar system.

I think showering will need to be efficient with so many people on board.  One really great YUUGE shower for everyone.  No shyness allowed.   Basically the space monkeys (errr..mars colonists) go into the shower 10-15 at a time, and get hosed down.   

I'm calling it the "Get Wright Space Shower" (tm).  My little contribution to the Musk space ecosystem.  It is true that to as high a degree as possible, the standard of living on the ship is a selling point.  I'm already thinking of the commercials!  I'm casting the best looking hollywood actresses for the product launch.

The 1st colonists will probably be living in the 1st noncrewed and the 2nd crewed BFSs for some time on the Martian surface as digging underground or burying above ground living and working quarters will take some time.

For sure there will be a lot of sweat work to do and those work teams will greatly appreciate a hot shower as they finish their shift.

One of the 1st sweaty surface jobs might be to erect dust shelters before the earth moving equipment is unloaded from the BFS cargo hold. http://www.ufsinc.com/applications/military/aircraft-hangars/
Title: Re: ITS Development Updates and Discussion Thread
Post by: jpo234 on 10/04/2016 01:10 pm
It just doesn’t seem to make sense to cut wholes in a perfectly good ship for an inferior viewing experience. Has anyone heard anything about why SpaceX wants to do that?

For the same reason the Tesla Model X has Falcon Wing doors: Elon likes it and it's cool.
Title: Re: ITS Development Updates and Discussion Thread
Post by: AbuSimbel on 10/04/2016 01:10 pm
That shower arrangement does not look attractive to me. Really wet towels are more convenient IMO. For comfort they should invest into convenient toilets. I think there are improvements to be made.

Edit: You can use good towels and wipes when you have washing machines on board. Another convenience worth investing in.
And you must make good use of towels onboard the Hearth of Gold. Otherwise you don't live up to the name.
Title: Re: ITS Development Updates and Discussion Thread
Post by: AbuSimbel on 10/04/2016 01:16 pm
Elon's choices seem crazy only if you refuse to understand the general plan: ITS is designed for colonization: if its passengers thought it's the same to watch Mars from a screen they wouldn't risk their lives to actually go there.
Title: Re: ITS Development Updates and Discussion Thread
Post by: Burninate on 10/04/2016 01:22 pm
Tim Urban has a new article about the ITS (http://waitbutwhy.com/2016/09/spacexs-big-fking-rocket-the-full-story.html) up. The title contains an easily guessable "F" word, so I won't be writing it here.

He had a discussion about it with Elon Musk several months ago, and kept quiet about it until today.

Interesting timeline attached.

1st uncrewed ITS to be launched Dec 2022!
Attached from where?  State your sources.
Title: Re: ITS Development Updates and Discussion Thread
Post by: Burninate on 10/04/2016 01:24 pm
Can the ITS tanker version of the spaceship do SSTO to allow orbital testing before the ITS booster files?

From the attached maybe it can do so and even carry a small test crew, assuming 91t of fuel in LEO is enough to deorbit and land.

It cannot do so while holding anywhere near its rated payload, because it would not have the thrust to lift off the pad on Earth.
Title: Re: ITS Development Updates and Discussion Thread
Post by: Burninate on 10/04/2016 01:43 pm
That sounds like a fungal nightmare...

This isn't an unsolvable problem, but the ISS solution isn't going to cut it. You're going to have to have laundry. It's not fun, but someone's got to do it!

I'm unclear on that.  We're trying to figure out whether the mass economics, both durable(machine) and consumable(dirty brine / fabric), are better for
*Some sort of laundry machine
or for a whole bunch of disposable, lightweight silver-coated:
*cotton
*microfiber polyester & spandex, as in athleticwear
*nonwoven polyethylene/polypropylene/PET, as in hospital gowns or Tyvek

garments, in what is essentially an aseptic cleanroom environment (there's no rolling in the dirt, air is constantly filtered, etc).  And how they compare to the principal consumable, food, which runs around 2kg/day, and provides water and oxygen as a side benefit further down the recycling stream.

Please provide your mass estimates on each for a 1000 day mission (or what's the standard now?  Should I assume short transit, but not short stay, will be the rule of things?).
Title: Re: ITS Development Updates and Discussion Thread
Post by: Robotbeat on 10/04/2016 02:25 pm
Can the ITS tanker version of the spaceship do SSTO to allow orbital testing before the ITS booster files?

From the attached maybe it can do so and even carry a small test crew, assuming 91t of fuel in LEO is enough to deorbit and land.
Orbital or near-orbital. Seems the spaceship will be doing X-33-style test flights.
Title: Re: ITS Development Updates and Discussion Thread
Post by: John Alan on 10/04/2016 02:31 pm
Would love to know what the thinking is about including actual windows on the ITS ship? They are mass inefficient and complicate the structural integrity and costs, and for most of the trip all you would see is the velvety deep black of space due to sun glare. Use of 3D, High Def. displays could be made to look like window and would show space without the glare. Or they could display anything the occupant of the stateroom wished, and be used as video component of com system. Even the forward viewing deck could be emulated with video. It just doesn’t seem to make sense to cut wholes in a perfectly good ship for an inferior viewing experience. Has anyone heard anything about why SpaceX wants to do that?

A window lets you look out with the depth perception that our two eye 3D brain system allows...  8)
You don't get that looking at a flat screen...  :(   

Yes... they could use other VR means to get the same sensation without hull windows...   ???
Maybe that's plan B...

Try driving a car with one eye covered and see how much visual distance info you loose in 2D...  :o
Title: Re: ITS Development Updates and Discussion Thread
Post by: TheTraveller on 10/04/2016 02:48 pm
Tim Urban has a new article about the ITS (http://waitbutwhy.com/2016/09/spacexs-big-fking-rocket-the-full-story.html) up. The title contains an easily guessable "F" word, so I won't be writing it here.

He had a discussion about it with Elon Musk several months ago, and kept quiet about it until today.

Interesting timeline attached.

1st uncrewed ITS to be launched Dec 2022!
Attached from where?  State your sources.

The attached schedule is quoted in Tim Urban's in depth interview with Elon that was embargoed till after his IAC talk. Lots of really good information here:

http://waitbutwhy.com/2016/09/spacexs-big-fking-rocket-the-full-story.html

Scroll down to the PLAN and read Elon's more in depth multi decade Mars Colonisation plan, which includes the 1st BFS uncrewed landing. As he never talks about the uncrewed BFS coming back to Earth, maybe assume it becomes the start of the Mars base?

Did you know Elon plans to donate the 1st returned BFS to the Air & Space Museum?

1st BFS on Mars (uncrewed) stays there. 2nd BFS returns to Earth and goes on display.
Title: Re: ITS Development Updates and Discussion Thread
Post by: DOCinCT on 10/04/2016 03:12 pm
It just doesn’t seem to make sense to cut wholes in a perfectly good ship for an inferior viewing experience. Has anyone heard anything about why SpaceX wants to do that?

For the same reason the Tesla Model X has Falcon Wing doors: Elon likes it and it's cool.
And about which he has second thoughts once manufacturing got under way.  Of course they are still there, but the Model 3 won't have them.
Title: Re: ITS Development Updates and Discussion Thread
Post by: mfck on 10/04/2016 03:13 pm
While the early flights will be crewed by steely eyed pioneers, who only need to look at each other for hygiene, later flights would need some massive personal hygiene solution for ordinary people. The reasons for that, I think, are mostly psychological - humans are very adaptable, given the right conditioning; strong will and the focus on the goal does this for the steely eyed pioneers kind, but ordinary people having been given a couple of days of training, as EM put it at the IAC Q&A (god's mercy upon us), will not be conditioned enough to stay social and excellent to one another and have to wait in-line to use amenities. The toilet is a soul asylum, especially in a crowded ship.

So, there will need to be a personal hygiene solution, and an excessive one, compared to a Navy or NASA standards.

I might be wrong, but istm that the proposals with flowing water, where the drain is recycled are not acceptable - it might be possible to recycle for a crew of 5 for three month, but recycling shower drain for 100 people would be either consumables (filters) or energy intensive. Solutions that minimise water flow do so by introducing mass/complexity overhead. Moreover, as someone mentioned it already, massive graywater processing is a bacterial and fungal heaven (or nightmare).

Additionally, we got to remember, that human body produces and sheds waste not only when it's owner decides - skin, hair and moisture are continuously produced and dumped into the environment.

So, it would seem the needed system should be
- highly available - don't want waiting lines, don't want set hours, don't want downtimes
- closed circle - to save the consumables mass
- anticeptic/antibacterial - actively (chemical/uv) and passively - small system, that can be sanitised fully (which, for example, would be hard with any kind of water processing plant)
- power and mass efficient

Now, with a hat tip to Frank Herbert, Dava Newman and many more I am ignorant of

What I envision as a solution is a kind of hygiene garment that is applied, rather than worn, on individual basis and is recycled after use.  The garment would have those major functions:

- minimise human waste introduced into the environment - body hair, skin and most of the volatiles
- serve as sensor layer for biometrics
- serve as the standard garment for any higher order suits.
- possibly (later development) serve as a biochemical and electrical interface to the contained body

The way I see it done is by spraying gel layers and curing them with UV on the wearer's body, producing a personally adjusted garment. Microgravity
and surface tension should help with uniformity, methinks.

The gel itself and the curing patterns are, obviously, the crux of the solution and the imaginary part of it :). Not being an engineer, I assume it is possible to create a pattern of nano-structures that causes any debris in the liquid flow to move in one direction, but not the other. The garment, being a system of manifolds, converts natural body movement to differential pressure between the manifolds, which circulates the fluid, providing a flow, that'd carry the waste particles through the nano-structure filters, trapping them inside. Excrements and urine are not collected by the garment (not by the basic, daily hygiene garment)

The garment saturation with waste would dictate the change frequency. Supposedly, the basic garment would be thin enough to be used as standard underwear for day-to-day use and would allow a minimum of couple of days to a week circle.

Once the garment is saturated, or needs replacement due to damage it is peeled off the body and recycled -  chemically, thermally and mechanically into water, garment material (probably some kind of polymer) and organic waste, that can be used further (to create fertilizer, maybe?).

I WAG the following

Garment dry mass - 1 to 2 kg (net polymer)
Garment wet mass - 5 to 10 kg
Base material total is mass times number of people times any margin required for redundancies, say three, so 2*100*3 = 600kg of base material + about a tonne of water + the mass of the processing plant (let's be optimistic with 1t ), doubled for redundancy + the mass of several change-stations (0.5t each) - we'are talking about 5t system for 100 people. I have no viable way to assess the power usage of such system, so again, wag - about 1000W peak while donning (uv laser, pumps, gantry movement) and about 5000W peak while recycling (pumps, centrifuge, heating)

While it seems to be mass and energy intensive, compared to wiping yourself with a wet cloth, it mostly closes the resource cycle and has synergies with other life-support requirements.
Title: Re: ITS Development Updates and Discussion Thread
Post by: docmordrid on 10/04/2016 03:53 pm
There are also the metal-ceramic glasses - aluminium oxynitride etc. - which can stop a .50 BMG at close range. Radiation resistant to boot.
Title: Re: ITS Development Updates and Discussion Thread
Post by: meekGee on 10/04/2016 03:54 pm
Would love to know what the thinking is about including actual windows on the ITS ship? They are mass inefficient and complicate the structural integrity and costs, and for most of the trip all you would see is the velvety deep black of space due to sun glare. Use of 3D, High Def. displays could be made to look like window and would show space without the glare. Or they could display anything the occupant of the stateroom wished, and be used as video component of com system. Even the forward viewing deck could be emulated with video. It just doesn’t seem to make sense to cut wholes in a perfectly good ship for an inferior viewing experience. Has anyone heard anything about why SpaceX wants to do that?

And there is the difference between engineering and marketing.. :)

All the great engineering in the world is meaningless if no one buys your products.

It's beyond marketing.  It's designing something that needs to be used by people, not just carry cargo.

Everyone forgets that a Mars Colony is also a social and psychological experience.

Having the crews in a good mental state when they arrive is super important.

Consider also that the first ships will probably act as habitats for a while.

That said, maybe they can make the window a little bit smaller?
Title: Re: ITS Development Updates and Discussion Thread
Post by: IRobot on 10/04/2016 04:01 pm
Would love to know what the thinking is about including actual windows on the ITS ship? They are mass inefficient and complicate the structural integrity and costs, and for most of the trip all you would see is the velvety deep black of space due to sun glare. Use of 3D, High Def. displays could be made to look like window and would show space without the glare. Or they could display anything the occupant of the stateroom wished, and be used as video component of com system. Even the forward viewing deck could be emulated with video. It just doesn’t seem to make sense to cut wholes in a perfectly good ship for an inferior viewing experience. Has anyone heard anything about why SpaceX wants to do that?
Astronomy observations could be done directly through the window, for crew enjoyment, with several magnitudes of luminance increase compared to ground amateur telescopes. Even without telescope it would be an amazing sight.

There is no "3D High def. display" with enough dynamic range to simulate that.
Title: Re: ITS Development Updates and Discussion Thread
Post by: mvpel on 10/04/2016 04:12 pm
It just doesn’t seem to make sense to cut wholes in a perfectly good ship for an inferior viewing experience. Has anyone heard anything about why SpaceX wants to do that?

The launch of CRS-8 was my first in-person launch viewing in my 45-year life. My son and I watched it from the veranda of the OSB-II building in the shadow of the VAB.

And let me tell you... it's an entirely different universe from video.

After seeing that Falcon 9 haul itself into the sky atop a retina-searing shard of man-made sunlight, all the dozens and dozens of launches I've ever watched on video since my first (the Apollo-Soyuz launch in 1975), and all the launch photos I've ever seen, are now no longer amazing in their own right but rather a reminder of something amazing which I witnessed with my own two eyes on that sunny April 8.

The exhaust plume was so bright it was bouncing reflections inside the material of my glasses lenses as if they were fiber optics - there was the brilliant exhaust I was witnessing at the center, and four or five bright ghost images of it on either side.

There's photos here and there of the Falcon 9 plume with the daytime sun in the background, and it had never occurred to me to notice that the sun and the plume were the same fully saturated #ffffff white - it's because the sun and the Falcon 9 exhaust are the same blinding white brightness, and #ffffff is the best a poor pitiful piece of paper or a monitor can deliver.

And I think any ISS astronaut would tell you exactly the same thing after their first visit to the Cupola.

And finally, consider this quote from the 2003 opposition:

Quote from: ISS Astronaut Edward Lu
Mars … is bright enough that even when we are on the lit side of the Earth, and with all the lights on inside, it is clearly visible against the black background of space.

So even if they do orient the ITS so that the sun is coming in the windows and there's some level of glare, Mars at the very least will undoubtedly be even more clearly visible than it was to Lu, particularly without the glare from the Earth below.

The Overview Effect: Something profound happens when astronauts see Earth from space for the first time (http://www.techinsider.io/overview-effect-nasa-apollo8-perspective-awareness-space-2015-8)

Title: Re: ITS Development Updates and Discussion Thread
Post by: Lars-J on 10/04/2016 06:09 pm
A new view of the ITS prototype LOX tank from instagram: https://www.instagram.com/p/BLJlTTeDpOr/
Title: Re: ITS Development Updates and Discussion Thread
Post by: sanman on 10/04/2016 06:25 pm
So according to the diagram and what Musk said, the LOX tank width is basically the width of the spaceship, right?
Title: Re: ITS Development Updates and Discussion Thread
Post by: Lars-J on 10/04/2016 06:27 pm
So according to the diagram and what Musk said, the LOX tank width is basically the width of the spaceship, right?

Yes. That tank appears to be 12m wide. (based on the people, each concrete square appears to be ~5m)
Title: Re: ITS Development Updates and Discussion Thread
Post by: Snake on 10/04/2016 07:39 pm
There are also the metal-ceramic glasses - aluminium oxynitride etc. - which can stop a .50 BMG at close range. Radiation resistant to boot.
Here is an article published today on new 18" x 35" ALON windows: http://www.prweb.com/releases/2013/5/prweb10774558.htm
Title: Re: ITS Development Updates and Discussion Thread
Post by: RanulfC on 10/04/2016 08:48 pm
Lets say that you need 4 tanker flights to refuel the spaceship.

Just FYI the presentation, (page 24, "Systems Architecture") shows what looks like 4-5 tankers per ship, (depends on how you interpret the picture) but at least 4 for filling up the Mars bound flight. This may change of course :)

Randy
Title: Re: ITS Development Updates and Discussion Thread
Post by: RanulfC on 10/04/2016 09:09 pm
Would love to know what the thinking is about including actual windows on the ITS ship? They are mass inefficient and complicate the structural integrity and costs, and for most of the trip all you would see is the velvety deep black of space due to sun glare. Use of 3D, High Def. displays could be made to look like window and would show space without the glare. Or they could display anything the occupant of the stateroom wished, and be used as video component of com system. Even the forward viewing deck could be emulated with video. It just doesn’t seem to make sense to cut wholes in a perfectly good ship for an inferior viewing experience. Has anyone heard anything about why SpaceX wants to do that?

And there is the difference between engineering and marketing.. :)

All the great engineering in the world is meaningless if no one buys your products.

It's beyond marketing.  It's designing something that needs to be used by people, not just carry cargo.

Everyone forgets that a Mars Colony is also a social and psychological experience.

Having the crews in a good mental state when they arrive is super important.

Consider also that the first ships will probably act as habitats for a while.

That said, maybe they can make the window a little bit smaller?

I fully expect the 'picture window' to change over time. While it does look impressive from LEO or LMO socially and psychologically the window will spend most of the time being a moral sink looking out into the 'big-black' of deep space. At this stage it's 'marketing' really since it would have no purpose either for the crew, (call me a Geth but windows ARE structural "weakness" areas and you won't have someone piloting from there at any point, unlike the LEM) or passengers that they can't get from the smaller more practical windows.

Something to consider is that despite the idea that an armored window can 'withstand' a .50BGM round they still tend to be operationally destroyed, (either structurally compromised or the frame itself is) and the more 'window' area, (or frame) the more susceptible they are. They are also going to have to layered/laminated and heat/cold resistant as well which will effect optics on a larger scale.

On the deck layout I'd expect the "inner" cabins would in fact be mostly storage/support with a central 'storm shelter' area for protection.

Randy
Title: Re: ITS Development Updates and Discussion Thread
Post by: guckyfan on 10/05/2016 08:38 am
Space is not black. Ever seen the splendor of a dark night without any light pollution? That's on earth with its atmosphere. In space it must be even more impressing. Earth and Mars are just the highlights at beginning and end of the journey.
Title: Re: ITS Development Updates and Discussion Thread
Post by: nacnud on 10/05/2016 09:58 am

It's beyond marketing.  It's designing something that needs to be used by people, not just carry cargo.

Everyone forgets that a Mars Colony is also a social and psychological experience.

Having the crews in a good mental state when they arrive is super important.

Consider also that the first ships will probably act as habitats for a while.

That said, maybe they can make the window a little bit smaller?

Makes me think of this https://www.bas.ac.uk/wp-content/uploads/2015/11/Halleywinter1-e1461581815397-1800x324.jpg
Title: Re: ITS Development Updates and Discussion Thread
Post by: DOCinCT on 10/05/2016 07:16 pm
A vacuum hose will only remove the water if there is a force pushing the water toward the hose.
I was thinking of something like a phone booth with a big fan on top, blowing air downward.  A fine mist of water (maybe 1 Liter) is sprayed in at the top, wafts down to the bottom where drain holes collect it, to be repumped to the top and sprayed in again.  The constant breeze prevents choking on the water, and also propells it down toward the floor.
This sounds like the "Fog Gun" by Buckmister Fuller.
Designed in 1927 (and prototyped in 1949) the ‘Fog Gun’ is a device that uses a jet of compressed air mixed with a small amount of finely atomized water to blast the dirt off of objects and people, soap optional.  He claimed a shower would use less than a pint of water.  Being mostly airborne water, the vacuum system suggested would take care of "drainage".
Title: Re: ITS Development Updates and Discussion Thread
Post by: RanulfC on 10/05/2016 10:35 pm
Space is not black. Ever seen the splendor of a dark night without any light pollution? That's on earth with its atmosphere. In space it must be even more impressing. Earth and Mars are just the highlights at beginning and end of the journey.

It actually isn't that impressive and that's what the astronauts said about it. You get used to it quickly and it loses its fascination. And unlike going to the Moon you will rapidly lose sight of Earth and Mars which will both be nothing but 'dots' I the sky and the window will begin to get on peoples nerves rather than being an attraction.

This isn't speculation and I'm somewhat surprised that Elon apparently didn't know this. (I suspect though it's 'marketing' so it may not have been brought to his attention) The ISS cupola IS an attraction because the Earth is RIGHT there and that's NOT going to be the case for the majority of the trip. This isn't something that psychologists haven't thought of and there are studies and information out there. The problem is it is not what most people want to think and combined with very little of the work being spread outside of the 'specialty' publications it is a common mistake to see.

Randy
Title: Re: ITS Development Updates and Discussion Thread
Post by: RanulfC on 10/05/2016 10:44 pm
A vacuum hose will only remove the water if there is a force pushing the water toward the hose.
I was thinking of something like a phone booth with a big fan on top, blowing air downward.  A fine mist of water (maybe 1 Liter) is sprayed in at the top, wafts down to the bottom where drain holes collect it, to be repumped to the top and sprayed in again.  The constant breeze prevents choking on the water, and also propells it down toward the floor.
This sounds like the "Fog Gun" by Buckmister Fuller.
Designed in 1927 (and prototyped in 1949) the ‘Fog Gun’ is a device that uses a jet of compressed air mixed with a small amount of finely atomized water to blast the dirt off of objects and people, soap optional.  He claimed a shower would use less than a pint of water.  Being mostly airborne water, the vacuum system suggested would take care of "drainage".

Part of the reason for not having a shower on the ISS is that airborne water in microgravity is VERY dangerous. Both Mir and Skylab showers had the user wearing a mask so that there was little danger of inhaling water. We still haven't figured out an effective microgravity shower mostly because its not 'really' needed but you will need it on the ITS. While wipes 'work' for the ISS nobody considers them effective and if microgravity reduces your sweating somewhat the fact is you actually tend to work harder as well. (A bonus is your sense of smell is degraded as well)

Early ITS's will be both habitat and vehicle so you'll be dealing with people who ARE working up a sweat and none of the effects of microgravity since you're on Mars. I can see it being arguable that being able to shower would be an incentive to being on Mars taking it away for the trip back is going to be a bummer and lest we forget Elon has hopes that the ITS can be used for voyages FUTHER than Mars :)

So like good looking, (and more work-capable) space suits investing in a reliable and effecve microgravity shower will pay benefits down the road :)

And the "Fog-Gun" concept is a good place to start :)

Randy
Title: Re: ITS Development Updates and Discussion Thread
Post by: rakaydos on 10/06/2016 01:12 am
What about a vaguely traditional shower on a rotating track? Even if it's only 1/10g effective gravity, combined with a good seal on the door that should keep the airborn water to a minimum.
Title: Re: ITS Development Updates and Discussion Thread
Post by: envy887 on 10/06/2016 02:31 am
What about a vaguely traditional shower on a rotating track? Even if it's only 1/10g effective gravity, combined with a good seal on the door that should keep the airborn water to a minimum.

Why not slowly rotate the whole ship? It would only take 2 or 3 RPM to produce a useful acceleration at the 6m radius. There are some issues with keeping power, cooling and comms all pointed in the right directions, but it's not insurmountable.
Title: Re: ITS Development Updates and Discussion Thread
Post by: IRobot on 10/06/2016 10:52 am
Space is not black. Ever seen the splendor of a dark night without any light pollution? That's on earth with its atmosphere. In space it must be even more impressing. Earth and Mars are just the highlights at beginning and end of the journey.

It actually isn't that impressive and that's what the astronauts said about it. You get used to it quickly and it loses its fascination.

As an amateur astronomer, I am completely fascinated by a very dark sky location and I can stare the stars (with/without telescope) for hours. Been doing it for decades, so your statement is a bit strange, as I would expect it to be much more impressive and overwhelming from space.

Maybe those astronauts were not into astronomy? can you provide some links to those statements?
Title: Re: ITS Development Updates and Discussion Thread
Post by: Semmel on 10/06/2016 12:50 pm
The problem can also be that you don't find any dark spot on the iss. Whenever there is light inside, reflections on the windows kill stargazing pretty fast. Not sure if SpaceX plans to make the observatory room completely dark or not. If it has as any light source, chances are it's useless for stargazing.
Title: Re: ITS Development Updates and Discussion Thread
Post by: guckyfan on 10/06/2016 02:56 pm
The problem can also be that you don't find any dark spot on the iss. Whenever there is light inside, reflections on the windows kill stargazing pretty fast. Not sure if SpaceX plans to make the observatory room completely dark or not. If it has as any light source, chances are it's useless for stargazing.

I am not sure about orientation. The Cupola seems mostly pointed towards earth. That would blend out most of the stars. What I have heard is that the view from the Cupola holds an endless fascination with the Astronauts.

Title: Re: ITS Development Updates and Discussion Thread
Post by: Snake on 10/07/2016 06:26 pm
Do you think the tanker will have a second pair of tanks that store the 380 t of fuel for delivery, or will it just have a single extended pair of tanks? Thanks.
Title: Re: ITS Development Updates and Discussion Thread
Post by: rsdavis9 on 10/07/2016 06:40 pm
I would guess an pair of extended tanks to keep the rest of the spacecraft/rocket as much as possible the same. Remember this is a second stage/spacecraft. The second stage should stay the same if possible to get commonality of manufacturing.
Title: Re: ITS Development Updates and Discussion Thread
Post by: biosehnsucht on 10/07/2016 07:33 pm
If it's not carrying much cargo and the crew section is gutted / never install in the first place, it should have quite a bit of extra fuel when it reaches orbit even without adding/stretching tanks. I don't know if it's enough that 4-5 flights would have enough fuel remaining to refuel a spaceship for Mars, or if it would take more flights though. I'm sure someone could math it out though...
Title: Re: ITS Development Updates and Discussion Thread
Post by: rsdavis9 on 10/07/2016 07:36 pm
What do you think of the possibility that the ISRU on mars is going to take longer and be harder then just sending tankers to mars to refuel the return ship. At least for the first couple of flights. It does make it more expensive because it requires tankers to sit idle on mars.

Title: Re: ITS Development Updates and Discussion Thread
Post by: matthewkantar on 10/07/2016 08:12 pm
(7-11 cm of Al, typical for ISS Columbus module according to the paper) would still exceed the 30-days limit recommended for ESA astronauts, although the colonists might perhaps accept such risk.

Do you mean 7-11 mm? Is there 4 inch thick aluminum on the ISS?

Matthew
Title: Re: ITS Development Updates and Discussion Thread
Post by: Toast on 10/07/2016 08:14 pm
What do you think of the possibility that the ISRU on mars is going to take longer and be harder then just sending tankers to mars to refuel the return ship. At least for the first couple of flights. It does make it more expensive because it requires tankers to sit idle on mars.

I don't think that would be possible. The tankers would burn all or almost all their fuel in transit and EDL, so you'd need to send lots of them for each spaceship. Way too many to be feasible in the first few flights, when they'll likely only have a few spaceships and tankers to begin with. Then on Mars you'd have logistics problems of how to get the fuel from the tankers to the spaceship, since they're designed to transfer fuel by docking in orbit--can't do that on the ground. Piping it between them would be hard, since I doubt they can land six or more spaceships in a tight cluster. Not to mention the worry that if one lands too far away for the piping you brought to reach it, then you may be stranded.
Title: Re: ITS Development Updates and Discussion Thread
Post by: Impaler on 10/07/2016 08:59 pm
What do you think of the possibility that the ISRU on mars is going to take longer and be harder then just sending tankers to mars to refuel the return ship. At least for the first couple of flights. It does make it more expensive because it requires tankers to sit idle on mars.

I don't think that would be possible. The tankers would burn all or almost all their fuel in transit and EDL, so you'd need to send lots of them for each spaceship. Way too many to be feasible in the first few flights, when they'll likely only have a few spaceships and tankers to begin with. Then on Mars you'd have logistics problems of how to get the fuel from the tankers to the spaceship, since they're designed to transfer fuel by docking in orbit--can't do that on the ground. Piping it between them would be hard, since I doubt they can land six or more spaceships in a tight cluster. Not to mention the worry that if one lands too far away for the piping you brought to reach it, then you may be stranded.

Sending tankers to Mars orbit would be the way to go, around 730 mt of propellant in Mars orbit could be delivered by a tanker that uses airobraking on arrival to capture into an high elliptical mars orbit.  Then on launch the returning spaceships need for propellant is massively reduced as it only needs to reach the tanker which is less then 5 km/s from the surface, so your surface propellant needs would be around 400 mt, and that means about 100 mt of Methane could be brought with you on landing to be supplemented by Oxygen produced entirely from the atmosphere.  Now you have a return capability without having to set up any ice mining on the first trips.  The tanker could be left in Mars orbit permanently to become a propellant depot in the future.
Title: Re: ITS Development Updates and Discussion Thread
Post by: rsdavis9 on 10/07/2016 09:18 pm
that means about 100 mt of Methane could be brought with you on landing to be supplemented by Oxygen produced entirely from the atmosphere.  Now you have a return capability without having to set up any ice mining on the first trips.  The tanker could be left in Mars orbit permanently to become a propellant depot in the future.

Thats what has bothered me about ISRU. I can see how a little device that takes electricity and atmosphere and makes oxygen. But the melting of soil into water and then getting it into tanks didn't seem to be as automatable as the oxygen extraction. You need diggers and conveyors and etc to get the liquid h2o.
Title: Re: ITS Development Updates and Discussion Thread
Post by: Semmel on 10/07/2016 09:27 pm
that means about 100 mt of Methane could be brought with you on landing to be supplemented by Oxygen produced entirely from the atmosphere.  Now you have a return capability without having to set up any ice mining on the first trips.  The tanker could be left in Mars orbit permanently to become a propellant depot in the future.

Thats what has bothered me about ISRU. I can see how a little device that takes electricity and atmosphere and makes oxygen. But the melting of soil into water and then getting it into tanks didn't seem to be as automatable as the oxygen extraction. You need diggers and conveyors and etc to get the liquid h2o.

And on top of that, any purifier will be pestered with residuals like minerals and tend to clog up, cover up electrodes, sensors, anything. Ever seen a water cooker after using it for a few weeks with tab water? How do you keep such equipment clean robotically? Really beats me how that should work.
Title: Re: ITS Development Updates and Discussion Thread
Post by: Chris Bergin on 10/07/2016 11:14 pm
Depsite two members twice noting there is a specific thread about Radiation protection on ITS, several members continued to flap their lips over it in this thread ;D

Those posts have been merged into the correct thread. Use that thread for radiation discussion:
https://forum.nasaspaceflight.com/index.php?topic=41309.0

And be civil, or you'll lose your post. Quote a bad post and start off an argument, and that chain will be removed.
Title: Re: ITS Development Updates and Discussion Thread
Post by: IainMcClatchie on 10/08/2016 12:10 am
Thats what has bothered me about ISRU. I can see how a little device that takes electricity and atmosphere and makes oxygen. But the melting of soil into water and then getting it into tanks didn't seem to be as automatable as the oxygen extraction. You need diggers and conveyors and etc to get the liquid h2o.

Agreed.

There is another big problem.  Mars doesn't have local supplies of chemical energy.  ISRU just means using the reaction mass that's there.  You have to bring your own energy in the form of solar panels or a reactor.  The energy requirements for the return trip are large enough that the electrical supply system will be the majority of the landed mass for the first couple of missions.

Producing methane not only requires separating CO2 into CO and O2, but requires subsequent high energy steps.  These are all going to be lossy, especially when using lightweight equipment.  So while methalox gets you more impulse per propellant weight, it does not get you more impulse per energy input when compared to just the carbon monoxide - LOX propellant combo.  The latter metric can be turned into impulse per Earth-to-Mars mass.

I did a rough design sketch of two systems which would return 100 tonnes from Mars to Earth, and it turns out that the mass needed from Earth to Mars is about the same.  One system used methalox for the return trip.  The other used carbon monoxide and LOX for the return trip.  My guess is that mission cost scales with Earth to Mars mass.  And so my guess is that there is nothing to be saved by using Mars' water for propellant.  And if there is no huge leverage from all that added processing, then I think about the mass, energy, maintenance, failure modes, and just complexity associated with mining and refining water.  No thanks!

That said, for propellants coming from Earth, methalox makes more sense.  Musk's plan requires both the Earth-Mars and Mars-Earth rockets to use the same propellants because they are the same rockets.  But as e.g. Robert Zubrin has pointed out, taking the empty rocket tanks all the way from Earth to Mars seems really wasteful.  It's better to use a refueled upper stage to boost the Mars rocket into near-TMI, and then return to Earth.  The Mars rocket does the rest of the trip on carbolox.

Musk's plan also has no staging from the surface of Mars all the way back to Earth.  That drives a requirement for very high Isp and makes methalox attractive.  But if you are willing to stage in Mars orbit, by refuelling the Mars-Earth trip with a bunch of tanker runs just as the Earth-Mars trip is done, then the vehicle gets much smaller and the Isp requirements allow carbolox.
Title: Re: ITS Development Updates and Discussion Thread
Post by: rsdavis9 on 10/08/2016 02:26 am
So how about mining water with something like how they mine sulfur? They pump hot water into a drill hole and melt the sulfur. Sort of like fraking. Drill holes and make lots of crevices so water may be melted out. Use hot water to do the melting.
Title: Re: ITS Development Updates and Discussion Thread
Post by: CuddlyRocket on 10/08/2016 03:55 am
Producing methane not only requires separating CO2 into CO and O2 ...

No it doesn't. You combine hydrogen with CO2 directly to produce methane and water.

Quote
Musk's plan also has no staging from the surface of Mars all the way back to Earth.  That drives a requirement for very high Isp and makes methalox attractive.  But if you are willing to stage in Mars orbit, by refuelling the Mars-Earth trip with a bunch of tanker runs just as the Earth-Mars trip is done, then the vehicle gets much smaller and the Isp requirements allow carbolox.

Where do you get the infrastructure to maintain and operate such a fleet of rockets from? And have you optimised for cost here? It sounds like you're optimising for performance.
Title: Re: ITS Development Updates and Discussion Thread
Post by: Robotbeat on 10/08/2016 04:03 am
I think that a tanker based on Mars actually makes a lot of sense. In the long term, if any of this settlement stuff happens, the architecture will evolve in that direction.
Title: Re: ITS Development Updates and Discussion Thread
Post by: Kaputnik on 10/08/2016 12:25 pm
Seeing as this is the ITS DEVELOPMENT thread.

What do we think will/should/might be the first actual hardware to fly in support of ITS development? There are a lot of options and combinations ranging from subscale component testing to all up integrated flight of the first ship or booster, and everything inbetween. A few options off the top of my head:
- 1/3rd Raptor and/or composite tankage flight tested in space via F9 (dedicated test stage as a payload or new US?)
- 1/3rd scale Raptor and/or composite tankage flight tested via a Grasshopper style suborbital vehicle
- full scale Raptor and tankage Grasshopper vehicle
- all up ITS Ship launched with partial prop load, likely suborbital only
- all up ITS Booster

Based on zero evidence, I think the full scale LOX tank could point towards full scale testing. I would like to see a flying bedsted type vehicle constructed from a development tank and engines, as a sort of Grasshopper for the ITS Ship, to retire multiple risks.
Title: Re: ITS Development Updates and Discussion Thread
Post by: RonM on 10/08/2016 02:51 pm
Considering to short time between now and planned first flight, SpaceX will have to skip subscale vehicle testing.
Title: Re: ITS Development Updates and Discussion Thread
Post by: Semmel on 10/08/2016 02:54 pm
One thing that I find puzzling.. if the spheres inside the fuel tanks are fuel reserves for landing, why is there no sphere in the LOX tank of the BFR booster?
Title: Re: ITS Development Updates and Discussion Thread
Post by: RonM on 10/08/2016 03:16 pm
One thing that I find puzzling.. if the spheres inside the fuel tanks are fuel reserves for landing, why is there no sphere in the LOX tank of the BFR booster?

Or why there is a sphere in the booster methane tank.

It seems to me they only need the reserve tanks in the spacecraft/tanker. The booster comes back for a landing immediately, just like the F9 first stage.
Title: Re: ITS Development Updates and Discussion Thread
Post by: DOCinCT on 10/08/2016 03:46 pm
Noticed an interesting similarity the ITS spaceship to the spaceship landing in this clip from a trailer for the upcoming Nat Geo Mars Global Event (mini-series in TV lingo).  Here the engines are canted outward do help keep blow-back low.  Landing legs extend down from "bays", just like in the animation from SpaceX.
[As Elon had technical input into the production, maybe not too surprising.]
Title: Re: ITS Development Updates and Discussion Thread
Post by: Kaputnik on 10/08/2016 06:26 pm
Considering to short time between now and planned first flight, SpaceX will have to skip subscale vehicle testing.

I agree that the timescale seems very short. But then again the original FH timescale seemed a little optimistic at the time, and wildly so in hindsight.

Going straight into full scale integrated testing is very daunting. It means building the launch facility before you have any experience with the vehicle. What if the proposed landing the booster back on the pad turns out to be impractical, for example?
Title: Re: ITS Development Updates and Discussion Thread
Post by: RonM on 10/08/2016 06:47 pm
Considering to short time between now and planned first flight, SpaceX will have to skip subscale vehicle testing.

I agree that the timescale seems very short. But then again the original FH timescale seemed a little optimistic at the time, and wildly so in hindsight.

Going straight into full scale integrated testing is very daunting. It means building the launch facility before you have any experience with the vehicle. What if the proposed landing the booster back on the pad turns out to be impractical, for example?

The dangers of rushing development. SpaceX will be building and testing the spaceship before the booster. They could make a small test vehicle to see if the new landing ops makes sense without delaying booster development. If there is a problem then they can redesign the booster.

Elon wants people on Mars by the middle of the next decade. Could easily wind up being in the 2030s.
Title: Re: ITS Development Updates and Discussion Thread
Post by: AncientU on 10/08/2016 07:00 pm
Considering to short time between now and planned first flight, SpaceX will have to skip subscale vehicle testing.

I agree that the timescale seems very short. But then again the original FH timescale seemed a little optimistic at the time, and wildly so in hindsight.

Going straight into full scale integrated testing is very daunting. It means building the launch facility before you have any experience with the vehicle. What if the proposed landing the booster back on the pad turns out to be impractical, for example?

The dangers of rushing development. SpaceX will be building and testing the spaceship before the booster. They could make a small test vehicle to see if the new landing ops makes sense without delaying booster development. If there is a problem then they can redesign the booster.

Elon wants people on Mars by the middle of the next decade. Could easily wind up being in the 2030s.

Testing the ITS spaceship (and then booster) at the Cape may explain why the main landing pad is oversized... and why the HIF is so large, too.
Title: Re: ITS Development Updates and Discussion Thread
Post by: Robotbeat on 10/08/2016 07:48 pm
I was thinking they'd test the spaceship suborbitally near white sands.
Title: Re: ITS Development Updates and Discussion Thread
Post by: Oli on 10/08/2016 08:49 pm
Sending tankers to Mars orbit would be the way to go, around 730 mt of propellant in Mars orbit could be delivered by a tanker that uses airobraking on arrival to capture into an high elliptical mars orbit.

That assumes capture with 730t propellant is feasible.
Title: Re: ITS Development Updates and Discussion Thread
Post by: Toast on 10/08/2016 09:54 pm
One thing that I find puzzling.. if the spheres inside the fuel tanks are fuel reserves for landing, why is there no sphere in the LOX tank of the BFR booster?

It may be because unlike the booster, the spaceship needs to store that propellant for the three to five month transfer before using it.
Title: Re: ITS Development Updates and Discussion Thread
Post by: Chris_Pi on 10/09/2016 12:51 am
One thing that I find puzzling.. if the spheres inside the fuel tanks are fuel reserves for landing, why is there no sphere in the LOX tank of the BFR booster?

It may be because unlike the booster, the spaceship needs to store that propellant for the three to five month transfer before using it.

Okay, That could make sense. But why is there a spherical tank in the booster fuel tank if it's a storage time issue? That tank would be needed in either both or none, But just one?
Title: Re: ITS Development Updates and Discussion Thread
Post by: Bob Shaw on 10/09/2016 12:57 am
The booster sphere may be used as part of the engine pressurisation system - remember, they won't be using He. The pressure vessels may look similar, but do different jobs.
Title: Re: ITS Development Updates and Discussion Thread
Post by: adrianwyard on 10/09/2016 01:07 am
I just posted the following in the Basic Rocket Science Q&A thread since there's probably a simple answer that doesn't need to be addressed in this thread. But what prompted the question was ITS' use of cryogenic methalox on very long duration missions (i.e. including outer planets): Would it make sense to let the methane and lox turn to gas and reliquify them only when needed?
 
For long duration missions cryogenic propellants are problematic because they tend to boil off to a gaseous state. To circumvent this we hear of designs that go to the trouble of keeping it cold enough that it stays liquid, or just switch to another propellant. But is there a straightforward reason that it couldn't be allowed to turn to gas, and then recooled and liquified only when needed?

Perhaps the energy and mass of the equipment needed to reliquify is always going to be demonstrably greater than insulation?
Title: Re: ITS Development Updates and Discussion Thread
Post by: Burninate on 10/09/2016 01:21 am
I just posted the following in the Basic Rocket Science Q&A thread since there's probably a simple answer that doesn't need to be addressed in this thread. But what prompted the question was ITS' use of cryogenic methalox on very long duration missions (i.e. including outer planets): Would it make sense to let the methane and lox turn to gas and reliquify them only when needed?
 
For long duration missions cryogenic propellants are problematic because they tend to boil off to a gaseous state. To circumvent this we hear of designs that go to the trouble of keeping it cold enough that it stays liquid, or just switch to another propellant. But is there a straightforward reason that it couldn't be allowed to turn to gas, and then recooled and liquified only when needed?

Perhaps the energy and mass of the equipment needed to reliquify is always going to be demonstrably greater than insulation?

Basically, as a gas they would occupy too great a volume, or require too high a pressure, or both;  Either of these makes the storage tank too heavy.  For oxygen, the Liquid/gas equivalent (1.013 bar and 15 °C (59 °F))  is 843.6 vol/vol.  That means that some small quantity of liquid oxygen permitted to boil off and heat up to room temperature, into a pressure vessel at 1 atmosphere, expands in volume by a factor of 843x.  You can squeeze that down to lower volume at higher pressure & the same temperature, but this higher pressure then needs a stronger pressure vessel.  There's no free lunch here - the mass of the storage tanks becomes ridiculously high if you permit much of the mass of your propellant to exist as gas (or more generally, to exist at a temperature much higher than its triple point)
Title: Re: ITS Development Updates and Discussion Thread
Post by: adrianwyard on 10/09/2016 01:50 am
Ah, I should have guessed. So mission-long active refrigeration and insulation is the plan?

(Part of me does wonder if a different in-space vehicle could use a huge super lightweight inflatable balloon - made of unspecified material - to temporarily store the boiled-off propellants. It certainly would be goofy looking. But that's off topic for ITS.)
Title: Re: ITS Development Updates and Discussion Thread
Post by: RanulfC on 10/09/2016 02:21 am
Considering to short time between now and planned first flight, SpaceX will have to skip subscale vehicle testing.

I agree that the timescale seems very short. But then again the original FH timescale seemed a little optimistic at the time, and wildly so in hindsight.

Going straight into full scale integrated testing is very daunting. It means building the launch facility before you have any experience with the vehicle. What if the proposed landing the booster back on the pad turns out to be impractical, for example?

The dangers of rushing development. SpaceX will be building and testing the spaceship before the booster. They could make a small test vehicle to see if the new landing ops makes sense without delaying booster development. If there is a problem then they can redesign the booster.

Elon wants people on Mars by the middle of the next decade. Could easily wind up being in the 2030s.

I need to point out that 'first flight' in no way is certain to be full-scale first flight and the first landings on Mars in the 2020s are going to be Red Dragon's launched by Falcon-Heavies. Musk himself says he's often carried away by his own optimism so I see no reason to assume the timeline given is carved in stone. (After all if you look at it the Falcon heavy seems to 'go-away' sometime before 2018 which would make no sense whatsoever :) )

I'm going to be very surprised if we don't see flight and orbital testing of sub-scale crew/tanker shapes as upper stages on F9/FH flights long before the full scale ones fly.

Randy
Title: Re: ITS Development Updates and Discussion Thread
Post by: Stan-1967 on 10/09/2016 03:28 am
Any additional discussion on the 200 kW deployable solar arrays?  They apparently deploy after the TMI burn, and then when the ITS is at Mars entry interface, they are gone.  I am thinking they are stowable, and can be redeployed when on the surface.   Alternately, they are jettisoned before EI.  Either case presents difficult trades
1.  Getting them stowed inside the ITS is a big challenge.  What it they get stuck and won't fold back up?  That could complicate entry.

2.  If they are jettisoned, it would be a shame, as the colonists need to be energy rich.   They will need more surface power than can be made with the 200kW panels anyways, but nice to have them as a additional source.

3.  If they are jettisoned, what does ITS do for power on the journey back to Earth?  This, more than anything, tells me they need to be able to be stowed well before entry interface.

How would they be deployed on the surface?   Mass wise, I would think that they could be extended like a tent canopy at the base of the ship, and supported from beneath with rigging/support structure.  They could be the start of meeting surface power requirements.



Title: Re: ITS Development Updates and Discussion Thread
Post by: Impaler on 10/09/2016 04:21 am
Sending tankers to Mars orbit would be the way to go, around 730 mt of propellant in Mars orbit could be delivered by a tanker that uses airobraking on arrival to capture into an high elliptical mars orbit.

That assumes capture with 730t propellant is feasible.

As the vehicle would normally make direct atmospheric entry at that mass and it only needs to scrub off around 1 km/s to capture into a high orbit that has to be within the vehicles capability or else it could never do the far high velocity and higher deceleration of landing from orbit on Earth.  The trajectory would be a slow hohman as their is no one on board and were trying to maximize propellant delivery.

Musks own cost calculus can be used to determine the price of this propellant delivery to mars orbit, if the tanker is one that's reached the end of it's lifespan and is thus fully amortized then the cost comes to just 35 dollars a kg, basically 3 times the LEO price of 11 dollars a kg.  Getting mass down the the martian surface is another 4 fold jump in cost because of the spacecrafts cost. 

The only restriction is that you can only send about 5 percent of your propellant in LEO to mars before you start using tankers that are not fully amortized yet and this would begin to raise the cost, so any propellant in mars orbit needs to be rationed and used just for speeding up the return of crew carry vessels or other high priority activity.
Title: Re: ITS Development Updates and Discussion Thread
Post by: MP99 on 10/09/2016 04:33 am
I just posted the following in the Basic Rocket Science Q&A thread since there's probably a simple answer that doesn't need to be addressed in this thread. But what prompted the question was ITS' use of cryogenic methalox on very long duration missions (i.e. including outer planets): Would it make sense to let the methane and lox turn to gas and reliquify them only when needed?
 
For long duration missions cryogenic propellants are problematic because they tend to boil off to a gaseous state. To circumvent this we hear of designs that go to the trouble of keeping it cold enough that it stays liquid, or just switch to another propellant. But is there a straightforward reason that it couldn't be allowed to turn to gas, and then recooled and liquified only when needed?

Perhaps the energy and mass of the equipment needed to reliquify is always going to be demonstrably greater than insulation?

You require a very large cryocooler, with heavy power demands, to reliquify that much gas over a short period at the end of the transit.

A much smaller cryocooler can maintain subcooled temperatures throughout the flight. (I suspect that pushing prop through the cooling channels of the Raptors will be sufficient for this, depending on the spaceship attitude.)

Also, for flights to destinations beyond Mars, the task of cooling will become much easier.

Cheers, Martin
Title: Re: ITS Development Updates and Discussion Thread
Post by: Chris_Pi on 10/09/2016 04:35 am
The booster sphere may be used as part of the engine pressurisation system - remember, they won't be using He. The pressure vessels may look similar, but do different jobs.

Could be that. Starting up with a lower-pressure gas, and as many engines as the booster will have the storage tank could get pretty big.
Title: Re: ITS Development Updates and Discussion Thread
Post by: Patchouli on 10/09/2016 04:39 am
Any additional discussion on the 200 kW deployable solar arrays?  They apparently deploy after the TMI burn, and then when the ITS is at Mars entry interface, they are gone.  I am thinking they are stowable, and can be redeployed when on the surface.   Alternately, they are jettisoned before EI.  Either case presents difficult trades
1.  Getting them stowed inside the ITS is a big challenge.  What it they get stuck and won't fold back up?  That could complicate entry.

2.  If they are jettisoned, it would be a shame, as the colonists need to be energy rich.   They will need more surface power than can be made with the 200kW panels anyways, but nice to have them as a additional source.

3.  If they are jettisoned, what does ITS do for power on the journey back to Earth?  This, more than anything, tells me they need to be able to be stowed well before entry interface.

How would they be deployed on the surface?   Mass wise, I would think that they could be extended like a tent canopy at the base of the ship, and supported from beneath with rigging/support structure.  They could be the start of meeting surface power requirements.





One thing I been thinking involving the solar arrays is they're large enough if you use an array of ten or more vs two you can seriously consider using electric propulsion for part of the delta V which would have an effect of reducing the mass of the entire system.

Title: Re: ITS Development Updates and Discussion Thread
Post by: savuporo on 10/09/2016 04:44 am
Ah, I should have guessed. So mission-long active refrigeration and insulation is the plan?
SpaceX so far has not given any indication that there is yet a plan for managing cryogenic propellants in long duration deep space flights.
Ditto for other issues like robustness of turbopumped engines beyond earth departure burns and plethora of other details.
Title: Re: ITS Development Updates and Discussion Thread
Post by: CuddlyRocket on 10/09/2016 06:08 am
I think that a tanker based on Mars actually makes a lot of sense. In the long term, if any of this settlement stuff happens, the architecture will evolve in that direction.

In the long term, very probably. But (as I'm sure you appreciate), the ITS isn't being designed for the long term, it's being designed for the here and now when there is no industrial infrastructure on Mars whatsoever. People (not you) can't criticise the ITS design based on more efficient architectures without explaining where the infrastructure needed to create, support and maintain those architectures comes from.
Title: Re: ITS Development Updates and Discussion Thread
Post by: guckyfan on 10/09/2016 06:13 am
Ah, I should have guessed. So mission-long active refrigeration and insulation is the plan?
SpaceX so far has not given any indication that there is yet a plan for managing cryogenic propellants in long duration deep space flights.
Ditto for other issues like robustness of turbopumped engines beyond earth departure burns and plethora of other details.

Actually Elon Musk has in his presentation. He said subcooling helps avoid cavitation in the turbopumps. This sounds to me like they need it subcooled to run the engines. It worries me somewhat. Though they will have thougt about it and made their design accordingly.
Title: Re: ITS Development Updates and Discussion Thread
Post by: Toast on 10/09/2016 06:35 am


Musks own cost calculus can be used to determine the price of this propellant delivery to mars orbit, if the tanker is one that's reached the end of it's lifespan and is thus fully amortized then the cost comes to just 35 dollars a kg, basically 3 times the LEO price of 11 dollars a kg.  Getting mass down the the martian surface is another 4 fold jump in cost because of the spacecrafts cost. 

The only restriction is that you can only send about 5 percent of your propellant in LEO to mars before you start using tankers that are not fully amortized yet and this would begin to raise the cost, so any propellant in mars orbit needs to be rationed and used just for speeding up the return of crew carry vessels or other high priority activity.

I still think this is incredibly impractical and unlikely. First, it would be only 1% of the tanker fleet that can be sent, the presentation showed tankers targeting 100 uses before retirement. Second, the only benefit is that it could help avoid difficulties with ISRU for early trips, but on early trips you can't afford to send tankers you can't get back. And last, you're running a risk that if a tanker fails to land (or even lands too far away to transfer propellant) you've then stranded both the spaceship and the tanker(s). ISRU has risks and will be hard to set up, but it's also an incredibly vital part of the ITS infrastructure and cannot be avoided. Without ISRU, ITS will not work. Can't reuse spaceships without ISRU, can't amortize costs without reuse, can't keep ticket prices low without amortization. It's ISRU or bust.

Sent from my Nexus 5X using Tapatalk

Title: Re: ITS Development Updates and Discussion Thread
Post by: Impaler on 10/09/2016 08:25 am


Musks own cost calculus can be used to determine the price of this propellant delivery to mars orbit, if the tanker is one that's reached the end of it's lifespan and is thus fully amortized then the cost comes to just 35 dollars a kg, basically 3 times the LEO price of 11 dollars a kg.  Getting mass down the the martian surface is another 4 fold jump in cost because of the spacecrafts cost. 

The only restriction is that you can only send about 5 percent of your propellant in LEO to mars before you start using tankers that are not fully amortized yet and this would begin to raise the cost, so any propellant in mars orbit needs to be rationed and used just for speeding up the return of crew carry vessels or other high priority activity.

I still think this is incredibly impractical and unlikely. First, it would be only 1% of the tanker fleet that can be sent, the presentation showed tankers targeting 100 uses before retirement. Second, the only benefit is that it could help avoid difficulties with ISRU for early trips, but on early trips you can't afford to send tankers you can't get back. And last, you're running a risk that if a tanker fails to land (or even lands too far away to transfer propellant) you've then stranded both the spaceship and the tanker(s). ISRU has risks and will be hard to set up, but it's also an incredibly vital part of the ITS infrastructure and cannot be avoided. Without ISRU, ITS will not work. Can't reuse spaceships without ISRU, can't amortize costs without reuse, can't keep ticket prices low without amortization. It's ISRU or bust.

Sent from my Nexus 5X using Tapatalk

I'm explicitly saying NOT to land propellant on surface, but to rendezvous with it in orbit.

Early missions is where I see propellant sent from Earth being used because you get a huge reduction in your propellant needs on surface from 1900 ton to something like 300 if you rendezvous in LMO, that is when your going to have the lowest propellant production capacity in place and this makes it feasible to even land the methane portion of that first return trip propellant needs in the vehicle so you only need atmospheric CO2 cracking for your LoX which can be a completely passive process occurring before astronauts arrive.

Long term you use the empty tankers in mars orbit as propellant depots and bring propellant from mars up to them once it is cheaper then sending it from Earth.  Basically replicating your Earth side system of tankers and on orbit propellant transfer.  If it's good for the goose it's good for the gander.

At that point you are landing the tanker on mars and only cycling between surface and orbit which means amortization is just like on Earth, a tankers lifespan could be split between earth and mars work with just one transit in between to retire them to mars so as to avoid losing more then 8 months not in active duty.  Each tanker would put between 1/3rd 1/4th of it's launch propellant in LMO but the low propellant consumed by the return ship at launch means the total propellant consumed is almost identical to sending the spacecraft directly to Earth at 9 km/s.  And that's before accounting for the lower mass it would have as a 5 km/s vehicle rather then a 9 km/s which means much lower dry mass, smaller tanks etc etc.
Title: Re: ITS Development Updates and Discussion Thread
Post by: Lumina on 10/09/2016 09:41 am
Considering to short time between now and planned first flight, SpaceX will have to skip subscale vehicle testing.

I agree that the timescale seems very short. But then again the original FH timescale seemed a little optimistic at the time, and wildly so in hindsight.

Going straight into full scale integrated testing is very daunting. It means building the launch facility before you have any experience with the vehicle. What if the proposed landing the booster back on the pad turns out to be impractical, for example?

Well, up to a point, the Falcon 9 has provided many subscale lessons for the ITS booster stage. Elon actually said in his IAC presentation that in many respects the Booster is a scaled-up version of the Falcon 9 booster stage.

For example, addressing the "What if..." question above, after all the Falcon 9 landing attempts SpaceX now knows that supersonic retropropulsion, the gridfins and their algorithm will always get them back to within X metres of the target centrepoint. They probably also know what correlates with the remaining error, much of which IMO is likely to be translation due to wind in the last seconds as the booster descends ever more slowly. If this is most of it, it is a solvable problem: I have personal experience docking an 80 foot boat in narrow berths under high crosswinds and I can tell you that bowthrusters make all the difference between slipping into the berth or crashing into the boat next to you. The equivalent for the booster would be a more powerful RCS and an extension to the algorithm so that the RCS can neutralize last-seconds crosswind error in real time.
Title: Re: ITS Development Updates and Discussion Thread
Post by: Torbjorn Larsson, OM on 10/09/2016 10:27 am
if you look at it the Falcon heavy seems to 'go-away' sometime before 2018 which would make no sense whatsoever :)

On the ITS presentation timeline FH goes away as a project using up development resources, not necessarily as a commercial entity which, yes, would make no sense whatsoever.

It is hard to foresee all the possible pathways forward in a project that is contingent on stuff like how many start and landing pads (which could be separate at the start) and demonstrators are undergoing RUDs, et cetera. So, say, in orbit refueling and ISRU fuel depots are part of the larger ITS, but I would think they will stick to simplicity and low cost if they can. Refueling in Mars orbit is not impossible, but also not optimal.

Title: Re: ITS Development Updates and Discussion Thread
Post by: Lumina on 10/09/2016 06:14 pm


Musks own cost calculus can be used to determine the price of this propellant delivery to mars orbit, if the tanker is one that's reached the end of it's lifespan and is thus fully amortized then the cost comes to just 35 dollars a kg, basically 3 times the LEO price of 11 dollars a kg.  Getting mass down the the martian surface is another 4 fold jump in cost because of the spacecrafts cost. 

The only restriction is that you can only send about 5 percent of your propellant in LEO to mars before you start using tankers that are not fully amortized yet and this would begin to raise the cost, so any propellant in mars orbit needs to be rationed and used just for speeding up the return of crew carry vessels or other high priority activity.

I still think this is incredibly impractical and unlikely. First, it would be only 1% of the tanker fleet that can be sent, the presentation showed tankers targeting 100 uses before retirement. Second, the only benefit is that it could help avoid difficulties with ISRU for early trips, but on early trips you can't afford to send tankers you can't get back. And last, you're running a risk that if a tanker fails to land (or even lands too far away to transfer propellant) you've then stranded both the spaceship and the tanker(s). ISRU has risks and will be hard to set up, but it's also an incredibly vital part of the ITS infrastructure and cannot be avoided. Without ISRU, ITS will not work. Can't reuse spaceships without ISRU, can't amortize costs without reuse, can't keep ticket prices low without amortization. It's ISRU or bust.

Sent from my Nexus 5X using Tapatalk

I'm explicitly saying NOT to land propellant on surface, but to rendezvous with it in orbit.

Early missions is where I see propellant sent from Earth being used because you get a huge reduction in your propellant needs on surface from 1900 ton to something like 300 if you rendezvous in LMO

(...snip...)

But does it make sense to introduce new architecture and more steps in the flight profile if all that will buy you is a reduction in ISRU propellant requirement from 1900 tons to 300 tons?

My take is that if you can make 300 tons of fuel on Mars then you can make 3,000 or 30,000 tons with more plants or more time (or both). There is no shortage of the resources, for a few centuries at least. Musk correctly pointed out in his presentation that water and CO2 are in "effectively unlimited" supply on Mars.
Title: Re: ITS Development Updates and Discussion Thread
Post by: meekGee on 10/09/2016 06:53 pm
One thing that I find puzzling.. if the spheres inside the fuel tanks are fuel reserves for landing, why is there no sphere in the LOX tank of the BFR booster?

It may be because unlike the booster, the spaceship needs to store that propellant for the three to five month transfer before using it.

Okay, That could make sense. But why is there a spherical tank in the booster fuel tank if it's a storage time issue? That tank would be needed in either both or none, But just one?

It could be on the other side, so the section view hid it.
Title: Re: ITS Development Updates and Discussion Thread
Post by: guckyfan on 10/09/2016 08:06 pm
It looks like the tanks in the upper stage are centered and the fuel lines run through them. The tank in the booster stage is off center, so maybe it has a different purpose. I sure would like so see question in the AMA answered about those spheres.
Title: Re: ITS Development Updates and Discussion Thread
Post by: Impaler on 10/09/2016 08:24 pm

But does it make sense to introduce new architecture and more steps in the flight profile if all that will buy you is a reduction in ISRU propellant requirement from 1900 tons to 300 tons?

My take is that if you can make 300 tons of fuel on Mars then you can make 3,000 or 30,000 tons with more plants or more time (or both). There is no shortage of the resources, for a few centuries at least. Musk correctly pointed out in his presentation that water and CO2 are in "effectively unlimited" supply on Mars.

No for the millionth time, propellant consumed actually matters on mars because it all has to be manufactured, even if the total resource in the ground is effectively unlimited the rate you can produce it at is going to be dependent on infrastructure which has cost, higher rates mean higher costs period.

If Propellant production on mars costs more then about 15 dollars a kg then it's cheaper to do the Mars orbital refill I've described because each kg of propellant taken on in orbit substitutes for more then 2 on the surface.
Title: Re: ITS Development Updates and Discussion Thread
Post by: RedLineTrain on 10/09/2016 08:30 pm

But does it make sense to introduce new architecture and more steps in the flight profile if all that will buy you is a reduction in ISRU propellant requirement from 1900 tons to 300 tons?

My take is that if you can make 300 tons of fuel on Mars then you can make 3,000 or 30,000 tons with more plants or more time (or both). There is no shortage of the resources, for a few centuries at least. Musk correctly pointed out in his presentation that water and CO2 are in "effectively unlimited" supply on Mars.

No for the millionth time, propellant consumed actually matters on mars because it all has to be manufactured, even if the total resource in the ground is effectively unlimited the rate you can produce it at is going to be dependent on infrastructure which has cost, higher rates mean higher costs period.

If Propellant production on mars costs more then about 15 dollars a kg then it's cheaper to do the Mars orbital refill I've described because each kg of propellant taken on in orbit substitutes for more then 2 on the surface.
But then the system would be dependent on Earth methane for return.  In his plan, Musk has been careful to avoid unnecessary interim gating items.  They require engineering effort that could instead be applied to the desired end system.
Title: Re: ITS Development Updates and Discussion Thread
Post by: DOCinCT on 10/09/2016 08:48 pm
A lot of what ifs, needs to be developed, insufficient etc.
Elon presented a presentation in Sept 2016 on an overall plan for a transit system, not the entire Mars infrastructure.  The NET window for a cargo ship to Mars is in 2027 (using dates in presentation).  That's 10 years to design, engineer and manufacture solutions to problems. Many of those solutions will not come from SpaceX but from NASA, ESA, Bigelow, Boeing, Lockheed, Japan, etc. (who knows maybe China as well).
Almost everything for Apollo had to be developed from scratch using slide-rules, calculators and some very primitive computers.  We should be able to do better.
Title: Re: ITS Development Updates and Discussion Thread
Post by: Impaler on 10/09/2016 08:48 pm

But does it make sense to introduce new architecture and more steps in the flight profile if all that will buy you is a reduction in ISRU propellant requirement from 1900 tons to 300 tons?

My take is that if you can make 300 tons of fuel on Mars then you can make 3,000 or 30,000 tons with more plants or more time (or both). There is no shortage of the resources, for a few centuries at least. Musk correctly pointed out in his presentation that water and CO2 are in "effectively unlimited" supply on Mars.

No for the millionth time, propellant consumed actually matters on mars because it all has to be manufactured, even if the total resource in the ground is effectively unlimited the rate you can produce it at is going to be dependent on infrastructure which has cost, higher rates mean higher costs period.

If Propellant production on mars costs more then about 15 dollars a kg then it's cheaper to do the Mars orbital refill I've described because each kg of propellant taken on in orbit substitutes for more then 2 on the surface.
But then the system would be dependent on Earth methane for return.  In his plan, Musk has been careful to avoid unnecessary interim gating items.  They require engineering effort that could instead be applied to the desired end system.

Being dependent on a on orbit propellant transfer is far and away preferable to being dependent on ISPP when that has never been done before, the propellant transfer being done here is just like that at Earth between a tanker and the manned spacecraft so their is no additional engineering here if you can get a craft to the surface you can get propellant to mars orbit even easier.
Title: Re: ITS Development Updates and Discussion Thread
Post by: Toast on 10/10/2016 04:32 am
Being dependent on a on orbit propellant transfer is far and away preferable to being dependent on ISPP when that has never been done before, the propellant transfer being done here is just like that at Earth between a tanker and the manned spacecraft so their is no additional engineering here if you can get a craft to the surface you can get propellant to mars orbit even easier.

ISRU for propellant production may not have been done before, but I cannot stress enough that without it the entire Mars colonization architecture is completely and utterly impossible. It's hard and it's unprecedented, but it's required for the entire system to work. And I don't think Martian-orbit propellant transfer is really any more sensible a proposal than Martian-surface propellant transfer. You've still got the massive problem of incredible inefficiency and massively wasteful use of critically needed spacecraft.

One tanker can carry 380 tons of fuel to orbit--that's what's left after it reaches orbit, plus a small reserve for Earth EDL. To make the transfer burn, 1,900 tons of propellant are needed. That's five tankers worth. So you launch a tanker, launch five more tankers to refuel it, burn the vast majority of the fuel to transfer to Mars, and aerobrake into orbit. Then a ship launches off the surface to rendezvous in Martian orbit--but it will already need ISRU to do that, because it will require a bare minimum of 3.8 km/s of delta-v to do so, which is more than half the total delta-v budget of the entire Earth return trip (~5.8-6.5 km/s). Then it'll need to refuel. It won't need a full propellant load since it's pretty much halfway to earth in terms of delta-v, but it'll need (optimistically) 550 tons or so, probably more. That's two or three tankers worth. So you are talking about launching two to three tankers to LEO, then launching ten to fifteen more to refuel them. Then you send them to Mars; a trip that will take 90-150 days, during which the tankers are useless. A tanker on earth can be used year-round to ferry fuel up to a fleet in LEO awaiting conjunction to launch, but while it's en route to Mars it is of no use to anybody. Then they get there, see one brief bit of use, and are then useless again. They just sit in orbit, drained of fuel and thus unable to return to Earth or to land on Mars. You could use them as a Martian orbital fuel depot, as you mention, but to do so you're going to need to supply them with fuel: Transfer the fuel from Earth and you're relegating even more of your tanker fleet to being useless for months on end, and still have the problem of them being out of fuel after they arrive and make their orbital fuel depot deposit, unable to return to Earth or land on Mars. And if you launch the fuel from Mars to the fuel depot, then you didn't need to send the tanker to Mars to refuel the spaceship in the first place.

All of this to avoid relying on ISRU, except you will need ISRU anyways. You'll need to load the Spaceship with the 3.8 km/s worth of delta-v to reach Martian orbit. And in doing so, you are essentially throwing away at least two tankers. Even if you can get them back, they'll be out of commission for years while en route. And the only time that ISRU could be problematic is in early missions, when you absolutely can't afford to throw away spacecraft without amortizing costs.

I could see a Martian fuel depot eventually being used--but only for ships that weren't going to the Martian surface in the first place, only stopping to refuel en route to the outer solar system. And if that's the case, the fuel will be generated from ISRU on Mars, not trucked in from Earth.

Sorry, but for spaceships going from Mars to Earth, refueling from tankers launched from Earth to Mars is just a really, really bad idea.

Title: Re: ITS Development Updates and Discussion Thread
Post by: Lars-J on 10/10/2016 04:35 am
Being dependent on a on orbit propellant transfer is far and away preferable to being dependent on ISPP when that has never been done before [snip]
[snip]
All of this to avoid relying on ISRU, except you will need ISRU anyways. You'll need to load the Spaceship with the 3.8 km/s worth of delta-v to reach Martian orbit.

Bingo. LMO propellant transfer does not remove the need for ISRU, it just changes how much ISRU you need to do.

(and not by a significant margin, more like the difference between filling up the ship with a half or full tank)
Title: Re: ITS Development Updates and Discussion Thread
Post by: Impaler on 10/10/2016 07:02 am
Being dependent on a on orbit propellant transfer is far and away preferable to being dependent on ISPP when that has never been done before, the propellant transfer being done here is just like that at Earth between a tanker and the manned spacecraft so their is no additional engineering here if you can get a craft to the surface you can get propellant to mars orbit even easier.

ISRU for propellant production may not have been done before, but I cannot stress enough that without it the entire Mars colonization architecture is completely and utterly impossible. It's hard and it's unprecedented, but it's required for the entire system to work. And I don't think Martian-orbit propellant transfer is really any more sensible a proposal than Martian-surface propellant transfer. You've still got the massive problem of incredible inefficiency and massively wasteful use of critically needed spacecraft.

One tanker can carry 380 tons of fuel to orbit--that's what's left after it reaches orbit, plus a small reserve for Earth EDL. To make the transfer burn, 1,900 tons of propellant are needed. That's five tankers worth. So you launch a tanker, launch five more tankers to refuel it, burn the vast majority of the fuel to transfer to Mars, and aerobrake into orbit. Then a ship launches off the surface to rendezvous in Martian orbit--but it will already need ISRU to do that, because it will require a bare minimum of 3.8 km/s of delta-v to do so, which is more than half the total delta-v budget of the entire Earth return trip (~5.8-6.5 km/s). Then it'll need to refuel. It won't need a full propellant load since it's pretty much halfway to earth in terms of delta-v, but it'll need (optimistically) 550 tons or so, probably more. That's two or three tankers worth. So you are talking about launching two to three tankers to LEO, then launching ten to fifteen more to refuel them. Then you send them to Mars; a trip that will take 90-150 days, during which the tankers are useless. A tanker on earth can be used year-round to ferry fuel up to a fleet in LEO awaiting conjunction to launch, but while it's en route to Mars it is of no use to anybody. Then they get there, see one brief bit of use, and are then useless again. They just sit in orbit, drained of fuel and thus unable to return to Earth or to land on Mars. You could use them as a Martian orbital fuel depot, as you mention, but to do so you're going to need to supply them with fuel: Transfer the fuel from Earth and you're relegating even more of your tanker fleet to being useless for months on end, and still have the problem of them being out of fuel after they arrive and make their orbital fuel depot deposit, unable to return to Earth or land on Mars. And if you launch the fuel from Mars to the fuel depot, then you didn't need to send the tanker to Mars to refuel the spaceship in the first place.

All of this to avoid relying on ISRU, except you will need ISRU anyways. You'll need to load the Spaceship with the 3.8 km/s worth of delta-v to reach Martian orbit. And in doing so, you are essentially throwing away at least two tankers. Even if you can get them back, they'll be out of commission for years while en route. And the only time that ISRU could be problematic is in early missions, when you absolutely can't afford to throw away spacecraft without amortizing costs.

I could see a Martian fuel depot eventually being used--but only for ships that weren't going to the Martian surface in the first place, only stopping to refuel en route to the outer solar system. And if that's the case, the fuel will be generated from ISRU on Mars, not trucked in from Earth.

Sorry, but for spaceships going from Mars to Earth, refueling from tankers launched from Earth to Mars is just a really, really bad idea.

I'm afraid you haven't done your calculations right.  The cost breakdown Musk himself used showed that all the tanker launchers to prepare a single full tanker, it's 6.6 launches actually, to send that full tanker to mars are small in comparison to sending the crew spacecraft, a price of 35 dollars a kg for propellant in LMO can be extrapolated and 720 mt is delivered by one full tanker traveling a slow hohman transfer.

On the first mission I would utilize only LoX extraction via a MOXIE like device while bringing 64 mt of Methane to the surface in the lander which is then supplemented by 244 mt of LOX produced on mars to give 308 mt of propellant, that puts the 150 mt dry mass of the spaceship plus 25 mt of return cargo into LMO.  This allows the leanest and lowest risk on your initial flights and avoids stranding large numbers of vehicles on mars during the setup of the ISPP process.

Then the spacecraft needs to take on enough propellant to provide for a 5.3 km/s burn to Earth because I'm doing an apples to apples comparison and replicating the 9 km/s burn that Musk clearly has planned for his direct Earth return as that's what's necessary for a 1 synod cycle, not that I think that's wise mind you, I'm just not low balling the calculations. 

This requires 525 mt of propellant to be transferred on orbit which is less then the tanker holds, so it could be sent to mars with less or we can consider this to be a contingency amount either for the tanker to use on capturing at mars or in rendezvousing with the manned spacecraft, of if you want the tanker can fly back to Earth or land and probably land their or descend and land on Mars as it would have 4.3 km/s of DeltaV remaining.

Long term the use of tankers from Earth in mars orbit has to compete with propellant on the mars surface, and visa-versa and I can even calculate how much propellant on mars has to cost to be competitive with tanker propellant, just 15 dollars a kg or about 90x what the propellant costs on the ground in bulk at the cape, any more expensive then that and it's cheaper to refill in orbit and utilize the on surface production capacity only for reaching orbit.  This is assuming all the propellant in the tanker is used because it's at the end of lifespan, return it to Earth would shift the price point up a small amount mostly depending on how well amortized the tanker was over it's lifespan as the propellant consumed is just 30 mt for a hohmann return and is almost trivial portion of what is delivered.
Title: Re: ITS Development Updates and Discussion Thread
Post by: darkenfast on 10/10/2016 07:02 am
I was thinking they'd test the spaceship suborbitally near white sands.


How would they get the spacecraft to White Sands? 
Title: Re: ITS Development Updates and Discussion Thread
Post by: rsdavis9 on 10/10/2016 11:53 am

Sorry, but for spaceships going from Mars to Earth, refueling from tankers launched from Earth to Mars is just a really, really bad idea.

I think thats the main point of musks idea. Fuel is cheap and spacecraft will always be expensive. Keeping the ships in the maximum possible duty is paramount to making the whole system cheap. ISRU us the technology that will make fuel cheap. Whether it lives up to its promise remains to be seen.

I think one of most important payloads for red dragon will be ISRU equipment to test out the ideas of massive fuel creation. LOX separation should be easy to prototype and be scalable from the prototype. Harvesting water has to harder. What ideas do people have for a simple prototype water harvester to make methane?
Title: Re: ITS Development Updates and Discussion Thread
Post by: savuporo on 10/10/2016 01:27 pm
I think one of most important payloads for red dragon will be ISRU equipment to test out the ideas of massive fuel creation.
With what power source exactly?
Title: Re: ITS Development Updates and Discussion Thread
Post by: rsdavis9 on 10/10/2016 01:29 pm
Whatever it is it will have to be small so small solar panel power source.
Title: Re: ITS Development Updates and Discussion Thread
Post by: envy887 on 10/10/2016 04:16 pm
I was thinking they'd test the spaceship suborbitally near white sands.


How would they get the spacecraft to White Sands?

Suborbital test flight and landing, naturally 8)

The ship is about the same diameter, length, and dry mass as the Saturn S-1C, which can be transported over land for short distances. 700 miles from McGregor to Spaceport America isn't "short" by any stretch of the imagination, but is certainly within the realm of possibility for a one-off trip.
Title: Re: ITS Development Updates and Discussion Thread
Post by: savuporo on 10/10/2016 08:19 pm
Whatever it is it will have to be small so small solar panel power source.

But you understand that a small solar panel is at odds with "massive fuel creation" ?
Title: Re: ITS Development Updates and Discussion Thread
Post by: rsdavis9 on 10/10/2016 08:35 pm
Whatever it is it will have to be small so small solar panel power source.

But you understand that a small solar panel is at odds with "massive fuel creation" ?

You have to prove the concept early on so you can then scale up.
Title: Re: ITS Development Updates and Discussion Thread
Post by: guckyfan on 10/10/2016 08:58 pm
Whatever it is it will have to be small so small solar panel power source.

But you understand that a small solar panel is at odds with "massive fuel creation" ?

You have to prove the concept early on so you can then scale up.

I think there is something much more urgent than a subscale test bed for ISRU. What we need is to know the nature of the water source. We need something ground penetrating that can give us this information. Not drilling, that is quite complex once it is more than a meter or two. Something like the ground penetrating radar the chinese Yutu rover on the moon had. Once we have that knowledge we can plan for water mining equipment.
Title: Re: ITS Development Updates and Discussion Thread
Post by: Toast on 10/10/2016 09:47 pm
What we need is to know the nature of the water source. We need something ground penetrating that can give us this information. Not drilling, that is quite complex once it is more than a meter or two. Something like the ground penetrating radar the chinese Yutu rover on the moon had. Once we have that knowledge we can plan for water mining equipment.

Agreed. The Sabatier reaction is well-understood (after all, it was discovered over a century ago), and ISRU is technologically very simple--IF you can get the water. The Spaceship could easily carry a 10 MW+ solar array: Based on commercially available ultraflex arrays we can estimate performance of ~150 W/kg, giving us an expected mass of ~67 mt, and a volume of ~250 m3. That's an easily obtainable goal, and an array of that size can power a Sabatier reactor to generate ~0.6 mt of propellant per hour. That part's easy, it's just a matter of logistics to manage the solar array and the reactor, and to deliver the components. The hard part is supplying the Sabatier reactor with hundreds of kg of water per hour to keep up that production rate when there's no readily available surface water (outside of the poles).
Title: Re: ITS Development Updates and Discussion Thread
Post by: b0objunior on 10/10/2016 09:51 pm
Whatever it is it will have to be small so small solar panel power source.

But you understand that a small solar panel is at odds with "massive fuel creation" ?

You have to prove the concept early on so you can then scale up.

I think there is something much more urgent than a subscale test bed for ISRU. What we need is to know the nature of the water source. We need something ground penetrating that can give us this information. Not drilling, that is quite complex once it is more than a meter or two. Something like the ground penetrating radar the chinese Yutu rover on the moon had. Once we have that knowledge we can plan for water mining equipment.

Mars 2020 rover will have one.
Title: Re: ITS Development Updates and Discussion Thread
Post by: Robotbeat on 10/10/2016 10:49 pm
Or you can just plan on harvesting random regolith which has 2-10% water absorbed in it anywhere on Mars.
Title: Re: ITS Development Updates and Discussion Thread
Post by: Impaler on 10/10/2016 11:19 pm
Some or possibly all of that widely distributed, aka at the equator' water is in hydrated minerals which require high temperatures to extract, it would need to be basically baked in a kiln to be extracted.  While possible it represents such a huge jump in cost and difficulty that it can't not have a significant impact on all aspects of the mission architecture.
Title: Re: ITS Development Updates and Discussion Thread
Post by: Robotbeat on 10/10/2016 11:38 pm
Extracting the water from even hydrated minerals takes significantly less energy than electrolyzing it for propellant, which dominates the power requirements. So yeah, it may take, say, 12MW instead of 10 or 11, or take 120 days instead of 110. Ultimately, if accessibility of glaciers is difficult, all you have to do is provide more power or take a little bit longer. Not a big deal in the grand scheme of things. Just the energy advantage of getting full sun and the rotational energy of sitting near the equator vs poles may be more than enough to offset the 10% overall higher energy costs of extracting water from regolith vs glacier.
Title: Re: ITS Development Updates and Discussion Thread
Post by: Impaler on 10/11/2016 04:25 am
Its the energy cost of moving and heating and disposing of all the non-water material that's the problem, you may even need to pulverize a lot of the material to get the vapor release from it to be fast enough.  Your estimates of trivial increases in cost don't have any justification.
Title: Re: ITS Development Updates and Discussion Thread
Post by: IainMcClatchie on 10/11/2016 04:46 am
Musk's plan also has no staging from the surface of Mars all the way back to Earth.  That drives a requirement for very high Isp and makes methalox attractive.  But if you are willing to stage in Mars orbit, by refuelling the Mars-Earth trip with a bunch of tanker runs just as the Earth-Mars trip is done, then the vehicle gets much smaller and the Isp requirements allow carbolox.

Where do you get the infrastructure to maintain and operate such a fleet of rockets from? And have you optimised for cost here? It sounds like you're optimising for performance.

You'd do it with only one (rocket) vehicle type at Mars.  Plug it into an electrical cord, and it (slowly) fills its tanks with carbolox.  It has sufficient delta-V to get to Mars orbit.  One lauches to Mars orbit, where it accumulates propellant from another making multiple trips from the ground.  Once the orbiting tanker is full, the first can take a full payload from the surface to Mars orbit, refuel, and from there boost back to Earth.

The key realization is that the vehicle size isn't driven by the amount of payload you want to land on Mars.  It's driven by the amount of payload you want to bring back (and how fast you want to come back).  Any vehicle with enough delta-V to get back, even staged, has enough delta-V to land a much larger payload on the surface.  A carbolox vehicle capable of returning 100 tonnes can land a 300 tonne payload (same as ITS).  Its departure burn from Earth is done by a methalox-powered upper stage.  For a cargo flight (long transit time), recovering that upper stage is only slightly more difficult than recovering an upper stage for a geostationary orbit.

For a given amount of mass from Mars to Earth, the vehicle size required is much, much smaller than the ITS architecture.  The required mass boosted from Earth is commensurately smaller.  So the BFR gets smaller and cheaper.  For a 100 tonne return, the Mars vehicle is 43 tonnes empty, holding 469 tonnes propellant.  Since you aren't sending most of 275 tonnes (ITS spaceship empty mass) of empty tankage to Mars and back along with your 300 tonnes of payload, everything gets smaller.  The vehicle itself gets smaller still if you use methalox, but as I said the energy requirements do not and so the dominant power system weight does not.

The Mars tanker idea actually has a nice option: you can lop a bit over a month off the return journey by using two tankers in Mars orbit.  The first refills the crewed vehicle leaving the Mars surface, and the second acts as a booster for leaving Mars.  The booster is not expended... it lands back on Mars when it's done, ready to refuel again.  You might even do this with three vehicles but the time gain is much smaller.

With a 43 tonne empty weight, the Mars vehicle can be launched into LEO atop a much smaller rocket: 12 raptors on the first stage, 1 on the second.  And that rocket, with 98 tonne LEO capability, is far better suited for lifting large (moneymaking) Earth comsats.
Title: Re: ITS Development Updates and Discussion Thread
Post by: Robotbeat on 10/11/2016 12:13 pm
Its the energy cost of moving and heating and disposing of all the non-water material that's the problem, you may even need to pulverize a lot of the material to get the vapor release from it to be fast enough.  Your estimates of trivial increases in cost don't have any justification.
Your assertions have less.

And I never said trivial. I said fairly small relative to the huge energy needed for electrolysis.
Title: Re: ITS Development Updates and Discussion Thread
Post by: envy887 on 10/11/2016 01:00 pm
...  Since you aren't sending most of 275 tonnes (ITS spaceship empty mass) of empty tankage to Mars and back along with your 300 tonnes of payload, everything gets smaller.
...
The ITS spaceship is only supposed to be 150 tonnes dry.
Quote
With a 43 tonne empty weight, the Mars vehicle can be launched into LEO atop a much smaller rocket: 12 raptors on the first stage, 1 on the second.  And that rocket, with 98 tonne LEO capability, is far better suited for lifting large (moneymaking) Earth comsats.
On the other hand, a larger vehicle is far better suited for paradigm changes (e.g. generic launch).
Title: Re: ITS Development Updates and Discussion Thread
Post by: uhuznaa on 10/11/2016 02:29 pm
Whatever it is it will have to be small so small solar panel power source.

But you understand that a small solar panel is at odds with "massive fuel creation" ?

You have to prove the concept early on so you can then scale up.

I think there is something much more urgent than a subscale test bed for ISRU. What we need is to know the nature of the water source. We need something ground penetrating that can give us this information. Not drilling, that is quite complex once it is more than a meter or two. Something like the ground penetrating radar the chinese Yutu rover on the moon had. Once we have that knowledge we can plan for water mining equipment.

MRO already did that and found glaciers with (relatively) pure water ice up to half a mile thick covered by a thin layer of regolith:

http://www.nbcnews.com/id/27827606/ns/technology_and_science-space/t/buried-glacier-found-mars/
Title: Re: ITS Development Updates and Discussion Thread
Post by: Ludus on 10/11/2016 04:56 pm
It would make sense on the quick SpaceX timetable to pick the location for the first human landing very soon so Red Dragon missions can contribute to understanding the site.

You'd have to know the exact circumstances to design the ISRU for propellant and that's primary. It would matter to the lander aerobraking and how much could be delivered to the surface.

Those glaciers in the Hellas basin seem like a decent site. Sitting on top of a glacier with relatively pure water ice in the thickest atmosphere available for ISRU and aerobraking, near the equator for solar and launch efficiency seems to cover a lot of important requirements.

ISRU designed for that site would be quite different from designs for locations that are leaner in water and carbon access.

Maybe you could occupy the space hollowed out in the glacier as it's melted and consumed. MRO measured glaciers 250-450m thick.
Title: Re: ITS Development Updates and Discussion Thread
Post by: guckyfan on 10/11/2016 05:36 pm

I think there is something much more urgent than a subscale test bed for ISRU. What we need is to know the nature of the water source. We need something ground penetrating that can give us this information. Not drilling, that is quite complex once it is more than a meter or two. Something like the ground penetrating radar the chinese Yutu rover on the moon had. Once we have that knowledge we can plan for water mining equipment.

MRO already did that and found glaciers with (relatively) pure water ice up to half a mile thick covered by a thin layer of regolith:

http://www.nbcnews.com/id/27827606/ns/technology_and_science-space/t/buried-glacier-found-mars/

Yes, but the data don't have a good enough vertical resolution. It is known that the regolith cover is no less than 1m or else the ice would sublimate. We know it is not more than 10m because if it were the orbital radar could have detected it.

Knowin what it is. 1m, 10m, or something inbetween is what we need to know for designing the ISRU equipment to mine that water. Designing for the worst case, 10m is possible, getting to know in advance is better. There would also be better data on how pure that ice is. Orbit data indicate, it is quite pure but local data would be much better.
Title: Re: ITS Development Updates and Discussion Thread
Post by: Lumina on 10/12/2016 03:38 am

But does it make sense to introduce new architecture and more steps in the flight profile if all that will buy you is a reduction in ISRU propellant requirement from 1900 tons to 300 tons?

My take is that if you can make 300 tons of fuel on Mars then you can make 3,000 or 30,000 tons with more plants or more time (or both). There is no shortage of the resources, for a few centuries at least. Musk correctly pointed out in his presentation that water and CO2 are in "effectively unlimited" supply on Mars.

No for the millionth time, propellant consumed actually matters on mars because it all has to be manufactured, even if the total resource in the ground is effectively unlimited the rate you can produce it at is going to be dependent on infrastructure which has cost, higher rates mean higher costs period.

If Propellant production on mars costs more then about 15 dollars a kg then it's cheaper to do the Mars orbital refill I've described because each kg of propellant taken on in orbit substitutes for more then 2 on the surface.

Yes that is true, but not just for fuel: virtually everything on Mars (air, water, food, fuel, habitable space, you name it...) will have to be manufactured or at least processed by some machine. Many of these things are nature's gifts here on Earth. So the challenge is huge. This challenge is currently a physical bottleneck, not so much a cost bottleneck. If we want the colony to grow and become self-sufficient someday we have to solve it, and I believe it is solvable with clever systems design and engineering.
Title: Re: ITS Development Updates and Discussion Thread
Post by: IainMcClatchie on 10/12/2016 05:51 am
It occurs to me that the upper stage (spaceship and tanker) would benefit more from the technology of landing on its launch mount than the booster does.  The landing gear on these vehicles cycles through a lot more delta-V than the booster.

For the tanker, it seems no more difficult than for the booster.  The spaceship can land on that same cradle on Earth, but what does it do on Mars?

It might be possible to land a landing and launch platform on Mars.  I realize a bunch of you folks are already talking about blast deflectors.  I'm suggesting something that has shock absorbers and active precision catch mechanisms.

For Elon's ITS, the benefit on Mars is marginal, since the spaceship just goes there and comes back.  All that is saved is the landing gear mass on the return trip.  I'd guess that a landing pad that can be dropped on the surface is likely to be much heavier than just landing gear.  So it's probably not a win.

I did the calculation for a modified system which uses a Mars orbit tanker and repeated launches from the Mars surface to fuel that tanker.  In this case the landing gear is left on the ground for many cycles, and it's a bigger win.  The leverage of ISRU pares it back quite a bit, however, so it's not as wonderful as I had initially thought.  I figured I'd post my results anyway.

1 kg saved on the Mars vehicle saves (with my assumptions) 37 kg of methalox propellant or 163 kg of carbolox propellant per return trip, whichever system you like best.  That in turn requires 0.53 and 0.93 kg less solar panel mass from Earth.  So if the grounded landing gear weighs less than 1.53x the mass saved on a methalox spaceship, there is less landed mass in a single return mission.  If that landing gear can be reused for a second return mission, mass is saved if it is less than 2.53x the vehicle mass saved.  For carbolox, the numbers are 1.93x and 2.93x.

It might be possible to put the launch platform under the spaceship, with a one-time-use heatshield underneath.  The spaceship uses extra propellant during the first landing to hover just above the surface for a second, while the same hydraulics which handle the precision catch operation later work backwards to reach out and place the platform against the ground.  Then the engines shut down and the spaceship settles into the launch mount as usual.

No landing gear means the spaceship loses the ability to land in different places.  But since the spaceship has to refuel and has to be close to the huge power source in order to do that, it really wasn't going to be able to land in widely disparate places anyway.  One thing a spaceship with gear can do, however, is short (~1000 km) hops on the surface, dawdle a while, and hop back, all with one fuel load.  Incredible reliability would be required to make this a feasible prospect with the only ride home for ~100 people.
Title: Re: ITS Development Updates and Discussion Thread
Post by: savuporo on 10/12/2016 03:28 pm
Whatever it is it will have to be small so small solar panel power source.

But you understand that a small solar panel is at odds with "massive fuel creation" ?

You have to prove the concept early on so you can then scale up.

So, reflying MOXIE then ? With MER level solar power or is there going to be a magic MMRTG available like Curiosity/Mars2020 ?
Just for reference, Curiosity was able to stuff about 2.5kWh into its batteries from the radioisotope generator at the mission starts, where MER's got 0.5kWh on a good day.
Title: Re: ITS Development Updates and Discussion Thread
Post by: Robotbeat on 10/12/2016 04:09 pm
MER level is fine for MOXIE which is only a 2ndary payload on 2020 rover.

But I suspect SpaceX wants to test their solar array tech. So much, much more than MER or even an entire "magic" MMRTG. Musk mentioned roll out arrays deployed by inflation as one thing they were looking at. If not 2018 then in the 2020 missions.
Title: Re: ITS Development Updates and Discussion Thread
Post by: MATTBLAK on 10/18/2016 11:25 pm
Mini-I.T.S. "MITS" - Proof-of-concept, scaled test vehicle for a crew of 3 or 4 Astronauts to Mars. Launch vehicle: upgraded Falcon Heavy with single Raptor engine upper stage. 5 or 6x launch architecture for Mars Design Reference Mission.

MITS has same shape and concept as large ITS; but scaled to be a 50 ton mass into Low Earth Orbit. Falcon Heavy Launch 1 places an unmanned Mini ITS into LEO to await a series of expendable LOX/CH4 tankers to rendezvous, dock and fill up the MITS. Last launch is the crew in a Dragon to dock with the MITS, get aboard it and depart on TMI. The Dragon returns unmanned to Earth.

Not in the plans, no. But technically feasible, yes?!
Title: Re: ITS Development Updates and Discussion Thread
Post by: envy887 on 10/19/2016 12:29 am
Falcon Heavy has enough thrust to lift off with a single Raptor mini ITS up to 1:6 volume / mass or 1:1.81 linear scale. That comes out at 50t payload, 25t ship dry mass, and 325t of methalox. Looks like it would stage the boosters at about 1400 m/s and the core at about 2000 m/s, which is good for RTLS and ASDS respectively. The core would have to be "buffed up" some more to take 400t of upper stage sitting on it, and the ship would need dedicated landing thrusters for terminal landing (SuperDracos would likely work for terminal hover if the Raptor does most of the delta-v at landing)

Why would it launch expendable tankers? And what does 50t of payload get you on Mars? It would get 20-25t payload for the return.
Title: Re: ITS Development Updates and Discussion Thread
Post by: MATTBLAK on 10/19/2016 01:25 am
I guess I was implying a fully-expendable Falcon Heavy - so as to get into orbit the biggest volume MITS possible. But it also occurs to me that a Mars Direct style mission could be done with a roughly ITS-shaped blunt biconic vehicle, that would include enough propellants for a direct descent to the Martian surface; aided by an aero-entry. And perhaps instead of 'tankers' - Earth Departure stages. The scaled-down resemblance to the big ITS architecture can be added to or taken away from as needed.
Title: Re: ITS Development Updates and Discussion Thread
Post by: Robotbeat on 10/19/2016 01:44 am
Mini-I.T.S. "MITS" - Proof-of-concept, scaled test vehicle for a crew of 3 or 4 Astronauts to Mars. Launch vehicle: upgraded Falcon Heavy with single Raptor engine upper stage. 5 or 6x launch architecture for Mars Design Reference Mission.

MITS has same shape and concept as large ITS; but scaled to be a 50 ton mass into Low Earth Orbit. Falcon Heavy Launch 1 places an unmanned Mini ITS into LEO to await a series of expendable LOX/CH4 tankers to rendezvous, dock and fill up the MITS. Last launch is the crew in a Dragon to dock with the MITS, get aboard it and depart on TMI. The Dragon returns unmanned to Earth.

Not in the plans, no. But technically feasible, yes?!
Basically this Hercules lander people at NASA Langley are looking at: http://www.thespacereview.com/article/3085/1

Discussed in this thread:
http://forum.nasaspaceflight.com/index.php?topic=41476.msg1600567#msg1600567
Title: Re: ITS Development Updates and Discussion Thread
Post by: MATTBLAK on 10/19/2016 01:50 am
Excellent! Wasn't aware of that at all. Great minds think alike? Nah - probably not... ;)
Title: Re: ITS Development Updates and Discussion Thread
Post by: Robotbeat on 10/19/2016 02:16 am
Excellent! Wasn't aware of that at all. Great minds think alike? Nah - probably not... ;)
It is pretty close to the vehicle I'd develop, too.
Title: Re: ITS Development Updates and Discussion Thread
Post by: Impaler on 10/19/2016 04:20 am
Mini-I.T.S. "MITS" - Proof-of-concept, scaled test vehicle for a crew of 3 or 4 Astronauts to Mars. Launch vehicle: upgraded Falcon Heavy with single Raptor engine upper stage. 5 or 6x launch architecture for Mars Design Reference Mission.

MITS has same shape and concept as large ITS; but scaled to be a 50 ton mass into Low Earth Orbit. Falcon Heavy Launch 1 places an unmanned Mini ITS into LEO to await a series of expendable LOX/CH4 tankers to rendezvous, dock and fill up the MITS. Last launch is the crew in a Dragon to dock with the MITS, get aboard it and depart on TMI. The Dragon returns unmanned to Earth.

Not in the plans, no. But technically feasible, yes?!
Basically this Hercules lander people at NASA Langley are looking at: http://www.thespacereview.com/article/3085/1

Discussed in this thread:
http://forum.nasaspaceflight.com/index.php?topic=41476.msg1600567#msg1600567

That hercules lander is basically what I've been preaching during this whole run up to the ITS reveal, vertical lander from mars orbit, sized for a round trip to orbit and back to surface with some offloading of propellant in mars orbit, pressure fed canted landing engines to not endanger the main propulsion system, cargo bay at the base of the vehicle for roll-on-roll-off access.

The use of the abort capsule on top is not what I imagined but using it when a separate sub-orbital hopper is a good idea and something I had imagined for the whole lander so as to move cargo from site to site, they see it as an exploration and rescue tool.

The main advantage is it's vastly smaller size and mass, at about 1/8th the mass of ITS and with a much lower payload fraction and deltaV requirement it looks infinity more practical.  Your looking at vehicle about the mass of the F9 1st stage here with only the amount of propellant found in the 2nd stage.  Something this size could be launched by F9H and with a few refueling missions and a departure stage it could be sent to mars to test it's landing capabilities.
Title: Re: ITS Development Updates and Discussion Thread
Post by: DOCinCT on 10/19/2016 05:14 pm
The main advantage is it's vastly smaller size and mass, at about 1/8th the mass of ITS and with a much lower payload fraction and deltaV requirement it looks infinity more practical.  Your looking at vehicle about the mass of the F9 1st stage here with only the amount of propellant found in the 2nd stage.  Something this size could be launched by F9H and with a few refueling missions and a departure stage it could be sent to mars to test it's landing capabilities.
Assuming I am reading the source documents correctly, you are missing the point.  It's not about what is landing and leaving the Martian Surface. 
It would take 8 SLS class launches to assemble and transit to Mars 2 cargo deliveries AND at least one LMO rendezvous, maybe more.   Then you need 4 SLS class launches to get a transit vessel (assembled in 3 launches) and the crew to Mars. One more SLS class launch is need to bring the crew back to earth.
Title: Re: ITS Development Updates and Discussion Thread
Post by: envy887 on 10/19/2016 05:55 pm
A development ITS that can be boosted by reuseable Falcon Heavy does seem eminently more feasible and practical than going straight to the full-scale version. An unmanned version could easily approach the mass fractions planned for the crewed ITS, and demonstrate orbital refueling, deep space operations, Mars EDL, automated cargo drop, automated ISPP, Mars surface propellant storage, relaunch, and Earth entry from interplanetary velocities.

I agree that the top-mounted terminal landing engines appear to be a good idea, and at this smaller scale they could double as launch abort propulsion for a crewed version. The 10t class pressure-fed gaseous methalox thruster SpaceX is supposedly working on could be ideal for this.

I don't think it's feasible to make the vehicle both modular and reusable as the joints in the heat shield would be a major liability at entry, and reassembling the vehicle at Mars would be highly impractical. It's also impractical to put the cargo deck at ground level with rear main propulsion, so I think hoisted unloading is the best option unless the vehicle is never returning from Mars.

Falcon Heavy reusable can definitely launch a vehicle with enough mass and volume to return a 4-6 person crew directly from Mars surface, if refueled and re-provisioned at the landing site by pre-positioned cargo vehicles and ISPP equipment. I get about 3 to 6 FHR launches to put the vehicle and it's TMI fuel tankers in LEO, but a full design study with the ITS US architecture and a FH booster would be interesting.
Title: Re: ITS Development Updates and Discussion Thread
Post by: hkultala on 10/19/2016 07:43 pm
Mini-I.T.S. "MITS" - Proof-of-concept, scaled test vehicle for a crew of 3 or 4 Astronauts to Mars. Launch vehicle: upgraded Falcon Heavy with single Raptor engine upper stage. 5 or 6x launch architecture for Mars Design Reference Mission.

The upper stage here is the unnecessary expensive component. Subscale version of ITS would be equally capable of working as upper stage than the final ITS is.
Title: Re: ITS Development Updates and Discussion Thread
Post by: rsdavis9 on 10/19/2016 07:53 pm
I still like musks system.
One booster stays on earth.
One upper stage.
Mods for upper stage while keeping the engines and airframe the same.
Tanker
Cargo carrier
People transporter
Should be easy to have a 4th mod. LEO and GEO shuttle style doors laucnher.

Less stuff to develop.
Title: Re: ITS Development Updates and Discussion Thread
Post by: envy887 on 10/19/2016 08:40 pm
Mini-I.T.S. "MITS" - Proof-of-concept, scaled test vehicle for a crew of 3 or 4 Astronauts to Mars. Launch vehicle: upgraded Falcon Heavy with single Raptor engine upper stage. 5 or 6x launch architecture for Mars Design Reference Mission.

The upper stage here is the unnecessary expensive component. Subscale version of ITS would be equally capable of working as upper stage than the final ITS is.

Exactly. Musk skipped the "Exploration" phase vehicle with equal capability and went straight to "Colonization" phase with greater CAPACITY. I think that substantially increases the risk that it will never be built, unfortunately.

A 1/6th scale upper stage launched on Falcon Heavy could prove every ITS concept for something like 1/10th the dev and testing cost.
Title: Re: ITS Development Updates and Discussion Thread
Post by: rsdavis9 on 10/19/2016 08:44 pm
Exactly. Musk skipped the "Exploration" phase vehicle with equal capability and went straight to "Colonization" phase with greater CAPACITY. I think that substantially increases the risk that it will never be built, unfortunately.

A 1/6th scale upper stage launched on Falcon Heavy could prove every ITS concept for something like 1/10th the dev and testing cost.

Maybe size doesn't matter as to the development cost. Most of the development is the same whether big or small.
Title: Re: ITS Development Updates and Discussion Thread
Post by: envy887 on 10/19/2016 08:51 pm
Exactly. Musk skipped the "Exploration" phase vehicle with equal capability and went straight to "Colonization" phase with greater CAPACITY. I think that substantially increases the risk that it will never be built, unfortunately.

A 1/6th scale upper stage launched on Falcon Heavy could prove every ITS concept for something like 1/10th the dev and testing cost.

Maybe size doesn't matter as to the development cost. Most of the development is the same whether big or small.

It doesn't matter when designing parts in CAD. But when you build and test a dev article, bigger is definitely much more expensive. Filling that 12m LOX tank for a single cryo test would cost hundreds of thousands of dollars.
Title: Re: ITS Development Updates and Discussion Thread
Post by: Nomadd on 10/19/2016 08:53 pm
Exactly. Musk skipped the "Exploration" phase vehicle with equal capability and went straight to "Colonization" phase with greater CAPACITY. I think that substantially increases the risk that it will never be built, unfortunately.

A 1/6th scale upper stage launched on Falcon Heavy could prove every ITS concept for something like 1/10th the dev and testing cost.

Maybe size doesn't matter as to the development cost. Most of the development is the same whether big or small.

It doesn't matter when designing parts in CAD. But when you build and test a dev article, bigger is definitely much more expensive. Filling that 12m LOX tank for a single cryo test would cost hundreds of thousands of dollars.
Only if you throw away the LOX when you're done.
Title: Re: ITS Development Updates and Discussion Thread
Post by: drzerg on 10/19/2016 09:44 pm
remember the rule - every experiment should be finished before death of the experimentator. musk do not have time for subscale multi year approach company.
Title: Re: ITS Development Updates and Discussion Thread
Post by: guckyfan on 10/19/2016 09:49 pm
It doesn't matter when designing parts in CAD. But when you build and test a dev article, bigger is definitely much more expensive. Filling that 12m LOX tank for a single cryo test would cost hundreds of thousands of dollars.
Only if you throw away the LOX when you're done.

Throwing the LOX away is what is usually done. They won't have a tank big enough to store it. Unless they build 2 test tanks and keep pumping the LOX between them, only replacing boiloff losses.  ;) I think if they had two they would have mentioned it.
Title: Re: ITS Development Updates and Discussion Thread
Post by: GWH on 10/19/2016 10:01 pm
It doesn't matter when designing parts in CAD. But when you build and test a dev article, bigger is definitely much more expensive. Filling that 12m LOX tank for a single cryo test would cost hundreds of thousands of dollars.

Also much more expensive if it fails, or requires redesign after testing or to suit high reuse operations.

I think building the big building block component prototypes first such as the LOX tank make sense, so they know they can.  But learning lessons on operation and components with low TRL would be much better on a smaller scale IMO.

Besides, if they went this route with the mini ITS there would be a good chance (build it in to the design from the get go) it could function as a reusable upper stage for F9/FH for regular launches and allow for rapid development and design iterations and building up to repeated reuse like they have done with F9 up till now - while using paid for launches to do so.
Title: Re: ITS Development Updates and Discussion Thread
Post by: lamontagne on 10/19/2016 10:05 pm
Somehow people don't seem to get that developing any generation of spaceship is extremely expensive.  The concept is relatively cheap, it's those thousands of hours of detailed engineering for everything from a fuel line to a nose fairing that will not be recoverable for the later vehicle.  All those simulations, all the documentation, etc...
If it then goes to just a few vehicles, it's crazy from a business viewpoint. 
Title: Re: ITS Development Updates and Discussion Thread
Post by: lamontagne on 10/20/2016 12:40 am
For those who worry about the difference is scale between the Falcon 9 and ITS, and have forgotten their history, I give you the difference in scale between gemini and Saturn 5, and the difference in scale between Falcon 9 and ITS.

Title: Re: ITS Development Updates and Discussion Thread
Post by: lamontagne on 10/20/2016 12:49 am
It doesn't matter when designing parts in CAD. But when you build and test a dev article, bigger is definitely much more expensive. Filling that 12m LOX tank for a single cryo test would cost hundreds of thousands of dollars.
Only if you throw away the LOX when you're done.

Throwing the LOX away is what is usually done. They won't have a tank big enough to store it. Unless they build 2 test tanks and keep pumping the LOX between them, only replacing boiloff losses.  ;) I think if they had two they would have mentioned it.

Yes, I agree it was likely just boiled off.  Lox is just energy, really.  A few big compressors running for a few days.  You might want to close the vent for a few hours and watch the pressure rise, while you're at it.  From a safe distance.
Title: Re: ITS Development Updates and Discussion Thread
Post by: Lumina on 10/20/2016 01:46 am
Exactly. Musk skipped the "Exploration" phase vehicle with equal capability and went straight to "Colonization" phase with greater CAPACITY. I think that substantially increases the risk that it will never be built, unfortunately.

A 1/6th scale upper stage launched on Falcon Heavy could prove every ITS concept for something like 1/10th the dev and testing cost.

Maybe size doesn't matter as to the development cost. Most of the development is the same whether big or small.

Right. I think there are several system architecture advantages in Musk's plan. It has beauty in its simplicity, if you can learn to not fear the sizes of the pieces.
Title: Re: ITS Development Updates and Discussion Thread
Post by: GWH on 10/20/2016 02:13 am
For those who worry about the difference is scale between the Falcon 9 and ITS, and have forgotten their history, I give you the difference in scale between gemini and Saturn 5, and the difference in scale between Falcon 9 and ITS.

Whats all those things between Gemini and Saturn V?

Personally less worried about difference in size between F9 and ITS but rather Dragon and ITS spaceship.
Title: Re: ITS Development Updates and Discussion Thread
Post by: Robotbeat on 10/20/2016 02:49 am
remember the rule - every experiment should be finished before death of the experimentator. musk do not have time for subscale multi year approach company.
I think this is the primary constraint, here. Musk is pretty young still, but this project is going to take a LONG time. He doesn't think he has a decade to just prove out a subscale system first. There's also the possibility that he could die early or otherwise lose control of SpaceX.

Also, there is, I think, some expectations-management being done by Elon, here. By proposing something ludicrous but still possible, it pushes his competitors to much greater efforts than they otherwise would.

I think asking the question "Is Musk trying to egg on Bezos?" is often a fruitful one.

EDIT:The egging on of one rocket leader to another is a game that I think von Braun and Korolev played with each other, dragging their countries to space and even to the Moon.
Title: Re: ITS Development Updates and Discussion Thread
Post by: su27k on 10/20/2016 04:30 am
Besides, if they went this route with the mini ITS there would be a good chance (build it in to the design from the get go) it could function as a reusable upper stage for F9/FH for regular launches and allow for rapid development and design iterations and building up to repeated reuse like they have done with F9 up till now - while using paid for launches to do so.

Requiring F9/FH to test mini ITS is not necessarily a good thing, it means modification of existing pad, range approval and fees, interrupting their commercial launches, and risk of taking out their existing pad if something went wrong.

A full scale ITS Ship should be able to be tested just like F9R-Dev1 or DC-X, which may actually have some advantage from operation point of view.
Title: Re: ITS Development Updates and Discussion Thread
Post by: GWH on 10/20/2016 06:01 am

Requiring F9/FH to test mini ITS is not necessarily a good thing, it means modification of existing pad, range approval and fees, interrupting their commercial launches, and risk of taking out their existing pad if something went wrong.

Launch facilities in Brownsville coming online could offset that disruption,  and if something does go wrong.. well that pretty well justifies all the effort of development at a smaller scale for new systems.
Title: Re: ITS Development Updates and Discussion Thread
Post by: envy887 on 10/20/2016 07:32 pm
Somehow people don't seem to get that developing any generation of spaceship is extremely expensive.  The concept is relatively cheap, it's those thousands of hours of detailed engineering for everything from a fuel line to a nose fairing that will not be recoverable for the later vehicle.  All those simulations, all the documentation, etc...
If it then goes to just a few vehicles, it's crazy from a business viewpoint. 

A cargo variant ITS spaceship scaled to Falcon Heavy could most likely put a ~10t commsat through supersynchronous GTO and return to land while all 3 FH boosters RTLS. Might make more business sense for 5t commsats too, compared to zero-margin extra-toasty F9 droneship landings. This is basically the fully reusable Falcon upper stage Musk said he was temped to pursue, but he prefers to focus on the full-size ITS.
Title: Re: ITS Development Updates and Discussion Thread
Post by: CuddlyRocket on 10/20/2016 08:58 pm
For those who worry about the difference is scale between the Falcon 9 and ITS, and have forgotten their history, I give you the difference in scale between gemini and Saturn 5, and the difference in scale between Falcon 9 and ITS.

Whats all those things between Gemini and Saturn V?

From the left: Mercury-Redstone; Mercury-Atlas 2; Gemini-Titan II; Apollo-Saturn IB; Apollo-Saturn V.

(If memory serves!)
Title: Re: ITS Development Updates and Discussion Thread
Post by: Kansan52 on 10/20/2016 09:05 pm
Looks correct. But going on memory as well.
Title: Re: ITS Development Updates and Discussion Thread
Post by: GWH on 10/20/2016 09:31 pm

From the left: Mercury-Redstone; Mercury-Atlas 2; Gemini-Titan II; Apollo-Saturn IB; Apollo-Saturn V.


Ah right, Mercury THEN Gemini.  Was thinking it was the opposite and being cheeky about the incremental steps taken leading up to Saturn V.  But yeah - Titan II to Saturn 1 (which was a cluster, apt analogy to FH) to Saturn 5. Perfect analogy for historical massive increase in size and capabilities and comparison to SpaceX now.

But still, I don't think the scale up to the booster is the big challenge.  Going to a rapidly reusable upper stage/spaceship from an expendable stage + reusable capsule is where an intermediate step is really needed IMO.
And going back to the historical example, wasn't Saturn 1 mostly built to test fly components of the Apollo program?
Title: Re: ITS Development Updates and Discussion Thread
Post by: JamesH65 on 10/21/2016 08:07 am
I wonder if by going for the full scale ITS as a first iteration, they actually might save a little money. They will have less constraints on size, and weight, which means designwise and manufacturing, an easier job. The use of many multiple Raptors also means one development path for the engine, which would be the same whether large or small ITS. Additional dev work on plumbing, but that's just plumbing, not in the same league as the engine development itself.

A lot of the hull dev work would also be the same for either - the tech for the large scale carbon  composite manufacture.

As others have said, making it big does increase manufacturing and testing costs for dev articles.

Lots of swings and roundabouts.
Title: Re: ITS Development Updates and Discussion Thread
Post by: Llian Rhydderch on 10/24/2016 02:28 am
It doesn't matter when designing parts in CAD. But when you build and test a dev article, bigger is definitely much more expensive. Filling that 12m LOX tank for a single cryo test would cost hundreds of thousands of dollars.
Only if you throw away the LOX when you're done.

Throwing the LOX away is what is usually done. They won't have a tank big enough to store it. Unless they build 2 test tanks and keep pumping the LOX between them, only replacing boiloff losses.  ;) I think if they had two they would have mentioned it.

Trucks?  Take it back to the LOX plant.

Rent the LOX for the test; pay for any LOX used and transportation/handling/overhead costs to the LOX producer as negotiated as part of the deal; return the rest back into the supply system to be sold as LOX as usual; cleaned/refined if necessary.
Title: Re: ITS Development Updates and Discussion Thread
Post by: DOCinCT on 10/25/2016 07:18 pm
In the recent reddit Elon was asked: "What level of completion is the interior habitable area layout of ITS at, and when might we expect to see renderings of it?"
His reply was: "Will aim to release details of the habitation section when we have actual live mockups. Maybe in a year or two."
Not willing to wait that long I decided to try my hand at layouts for 3 decks of the habitation section, which I have posted to the the L2 Level: SpaceX F9/FH/ITS Renderings  http://forum.nasaspaceflight.com/index.php?topic=35307.0. 
As that forum is mainly for images rather than extended discussion, I created this post instead (hopefully that's OK to do).

Title: Re: ITS Development Updates and Discussion Thread
Post by: lamontagne on 10/25/2016 07:56 pm
In the recent reddit Elon was asked: "What level of completion is the interior habitable area layout of ITS at, and when might we expect to see renderings of it?"
His reply was: "Will aim to release details of the habitation section when we have actual live mockups. Maybe in a year or two."
Not willing to wait that long I decided to try my hand at layouts for 3 decks of the habitation section, which I have posted to the the L2 Level: SpaceX F9/FH/ITS Renderings  http://forum.nasaspaceflight.com/index.php?topic=35307.0. 
As that forum is mainly for images rather than extended discussion, I created this post instead (hopefully that's OK to do).
Only 42 berths?  It does seem a little small for 100 people, or perhaps I have misunderstood the quantities?
Title: Re: ITS Development Updates and Discussion Thread
Post by: DOCinCT on 10/25/2016 08:26 pm
In the recent reddit Elon was asked: "What level of completion is the interior habitable area layout of ITS at, and when might we expect to see renderings of it?"
His reply was: "Will aim to release details of the habitation section when we have actual live mockups. Maybe in a year or two."
Not willing to wait that long I decided to try my hand at layouts for 3 decks of the habitation section, which I have posted to the the L2 Level: SpaceX F9/FH/ITS Renderings  http://forum.nasaspaceflight.com/index.php?topic=35307.0. 
As that forum is mainly for images rather than extended discussion, I created this post instead (hopefully that's OK to do).
Only 42 berths?  It does seem a little small for 100 people, or perhaps I have misunderstood the quantities?

It's reasonable for early missions.  Musk did say 100 (or more) eventually.  Space starts to get tight as you go up levels. In a linear design as in a sub, you can pack more in.
I see upper levels being flight crew and infirmary and then more recreation space.

Update:  I did a quick floor plan for the 4th deck (flight crew infirmary)  space is tight.
Title: Re: ITS Development Updates and Discussion Thread
Post by: lamontagne on 10/25/2016 08:30 pm
In the recent reddit Elon was asked: "What level of completion is the interior habitable area layout of ITS at, and when might we expect to see renderings of it?"
His reply was: "Will aim to release details of the habitation section when we have actual live mockups. Maybe in a year or two."
Not willing to wait that long I decided to try my hand at layouts for 3 decks of the habitation section, which I have posted to the the L2 Level: SpaceX F9/FH/ITS Renderings  http://forum.nasaspaceflight.com/index.php?topic=35307.0. 
As that forum is mainly for images rather than extended discussion, I created this post instead (hopefully that's OK to do).
Only 42 berths?  It does seem a little small for 100 people, or perhaps I have misunderstood the quantities?

It's reasonable for early missions.  Musk did say 100 (or more) eventually.  Space starts to get tight as you go up levels. In a linear design as in a sub, you can pack more in.
I see upper levels being flight crew and infirmary and then more recreation space.
Wonder if the ITS Spaceship design is stretchable, rather like an aircraft, or if it's a whole new design of you add a few meters to the length? Three more floors would do wonders for living space, at the cost of about 7.5m in extra length...
Title: Re: ITS Development Updates and Discussion Thread
Post by: Terra Incognita on 10/25/2016 08:32 pm
I like the idea of the spiral staircase for the on Mars 0.4g which could also be used in zero g.

Well done in putting the effort in, I appreciate it but the ITS will spend most of its time in zero-g this layout is almost 100% designed for gravity. It also if you don't mind me saying it looks a bit grim rather than cruise ship.

I think we should be looking to high-end yacht manufacturers design and layout not the navy.

This architect student has done some very sexy inspiring designs for the ITS internal layout. It has a way to go but it looks like a lot more of a fun design: http://imgur.com/a/SOGnu
Title: Re: ITS Development Updates and Discussion Thread
Post by: Kaputnik on 10/25/2016 08:44 pm
In the recent reddit Elon was asked: "What level of completion is the interior habitable area layout of ITS at, and when might we expect to see renderings of it?"
His reply was: "Will aim to release details of the habitation section when we have actual live mockups. Maybe in a year or two."
Not willing to wait that long I decided to try my hand at layouts for 3 decks of the habitation section, which I have posted to the the L2 Level: SpaceX F9/FH/ITS Renderings  http://forum.nasaspaceflight.com/index.php?topic=35307.0. 
As that forum is mainly for images rather than extended discussion, I created this post instead (hopefully that's OK to do).
Only 42 berths?  It does seem a little small for 100 people, or perhaps I have misunderstood the quantities?

It's reasonable for early missions.  Musk did say 100 (or more) eventually.  Space starts to get tight as you go up levels. In a linear design as in a sub, you can pack more in.
I see upper levels being flight crew and infirmary and then more recreation space.
Wonder if the ITS Spaceship design is stretchable, rather like an aircraft, or if it's a whole new design of you add a few meters to the length? Three more floors would do wonders for living space, at the cost of about 7.5m in extra length...


Doubtful, as it would change the OML and centre of gravity. Perhaps expansion into the cargo space would be feasible.
Title: Re: ITS Development Updates and Discussion Thread
Post by: lamontagne on 10/25/2016 08:56 pm
Using the cargo area might do the trick, although there seems to be a pressure bulkhead there, with the cargo unpressurized in the presentation spaceship.  If the spaceship Musk showed is the Heart of Gold, i.e. a very early ship, then it will not have 100 people aboard.  So perhaps we should not try to pack 100 people in.  20 to 30 might be the upper limit to that arrangement.
After all, we should expect all passenger, mixed and all cargo versions.
Isn't there a door/area too many in the airlock? I would have though an outer door an an inner door would be enough.
Title: Re: ITS Development Updates and Discussion Thread
Post by: Robotbeat on 10/25/2016 09:05 pm
Musk implied the ITS spaceship could be expanded in the future, but the comments were in context of 200 to 400+ passengers in the ITS. I wouldn't imagine it'd be simple, but it wouldn't have to be.
Title: Re: ITS Development Updates and Discussion Thread
Post by: DOCinCT on 10/25/2016 10:57 pm
Well done in putting the effort in, I appreciate it but the ITS will spend most of its time in zero-g this layout is almost 100% designed for gravity. It also if you don't mind me saying it looks a bit grim rather than cruise ship.
Thanks.
I don't really see this as passenger for the first few flights; even then first colonists will need to "rough it" a bit.  If Elon's comments about video game space etc. are not just a bit 'tongue in cheek' then it won't be a cruise ship. 
I designed the layout for a gravity well, but I think it works for zero-g, there is just more up a direction (up-down) than in the ISS.  One of the concerns I raised in supplemental material is the 3-6G's or more during take-off, departure and landing.  I don't know what the "mattress" material might be to deal with that.
Title: Re: ITS Development Updates and Discussion Thread
Post by: Oersted on 10/26/2016 01:06 pm
Weight considerations will be paramount when it comes to the interior design of ITS. The varying gravity environments are also of major importance: single high g vector at lift-off, zero g en route, perpendicular high g vectors at landing, low g on the Martian surface.

Logically these two main considerations - weight and gravity-vector flexibility - point towards a lightweight and highly-configurable interior. Rather than walls, cupboards and beds we will see bags, cloth separations and inflatable furniture. Lightweight ultra-strong textiles, aerogel and mountaineering gear (hooks, ropes, webbing, hammocks, netting, etc) will make for a somewhat alien interior befitting the new environment of interplanetary spaceflight.

I imagine solid storage lockers along the inside of the hull and a big central space criss-crossed by several load carrying beams fitted with lots of attachment points. Netting, cloth barriers and inflatables will be used for the necessary subdivisions according to the needs (privacy, organisation, etc) encountered along the trip. Inflatable couches mounted on solid attachment points will be used for the short high g periods. Walls created with taut netting and inflatables will be constructed for the surface stay.

We have to remember that control panels and dashboards and cockpits are a thing of the past. IST will be controlled from laptops, tablets and VR glasses. Collaboration on-board will happen in a virtual space or in ad-hoc meetings. This will all be well-served by the kind of environment I have sketched. For surface operations these techniques will be very useful as well.

The only true spaceship constructed by humanity so far was the Lunar Module, which could only be operated in zero and one-sixth g. It had no chairs and no beds. Floating/standing up was just fine during daytime operations and hammocks were strung out at night. I imagine something similar for the ITS. Sleeping in a sleeping bag/hammock inside a personal pod made of cloth, with silence ensured by earplugs and noise-cancelling headphones, should be very comfortable in zero and one-third g.
Title: Re: ITS Development Updates and Discussion Thread
Post by: DOCinCT on 10/26/2016 01:43 pm
This architect student has done some very sexy inspiring designs for the ITS internal layout. It has a way to go but it looks like a lot more of a fun design: http://imgur.com/a/SOGnu
I've seen those rendering (I used his/her schematic for dimensions).  The "cabins" remind me of those micro-rooms in Japan.  Given size I would imagine them only being used for sleeping. I think you need space for conversation etc. in the sleeping areas.
I did create a modified version of deck one which has more open space, monitors and portholes (haven't changed wall or fixture colors, decor will help for the 6-7 month trip).
Title: Re: ITS Development Updates and Discussion Thread
Post by: sghill on 10/26/2016 01:46 pm
In the recent reddit Elon was asked: "What level of completion is the interior habitable area layout of ITS at, and when might we expect to see renderings of it?"
His reply was: "Will aim to release details of the habitation section when we have actual live mockups. Maybe in a year or two."
Not willing to wait that long I decided to try my hand at layouts for 3 decks of the habitation section, which I have posted to the the L2 Level: SpaceX F9/FH/ITS Renderings  http://forum.nasaspaceflight.com/index.php?topic=35307.0. 
As that forum is mainly for images rather than extended discussion, I created this post instead (hopefully that's OK to do).

Cool image, but I see an entire crew deck filled with wasted space and mass.  There are more efficient ways of transporting large numbers of people in small spaces.  After your sleep period, you put away your things and the space becomes available to do other activities.
Title: Re: ITS Development Updates and Discussion Thread
Post by: Robotbeat on 10/26/2016 03:06 pm
People will want a permanent private space for sleeping, dressing, computer use, etc. It can be small, but it should be dedicated.
Title: Re: ITS Development Updates and Discussion Thread
Post by: docmordrid on 10/26/2016 03:32 pm
And privacy for couples 'activities.' 3-4 months is a long trip.
Title: Re: ITS Development Updates and Discussion Thread
Post by: Jdeshetler on 10/26/2016 03:52 pm
The Mars Sleeping Quarter could be:
     1) a cross design of ISS sleeping quarter module and first class seat setting. 
           - the padded seat setting can be converted for sleeping, launching/entry and sofa.
           - use as a working/lecture spaces.
           - repositioned to the wall from the floor if the space ship's internal mid-section is rotating to create an artificial mini-gravity.
     
     2) a removable module:
           - so it can be transferred to the Mars habitation to minimizing the shock of transition from the cozy spaceship to cold and barren Mars habitation.
           - assigned to each crew so each module can be personalized to keep their privacy and moral high in the space and/or on the ground.
           - so the spaceship can be lightened up for the returning flight.
     
Title: Re: ITS Development Updates and Discussion Thread
Post by: Terra Incognita on 10/26/2016 03:54 pm
And privacy for couples 'activities.' 3-4 months is a long trip.
Wayyy off topic and a serious question: but I've always wondered if anyone has actually ever done that in space.

Anyone know the answer?
Title: Re: ITS Development Updates and Discussion Thread
Post by: DOCinCT on 10/26/2016 08:39 pm
And privacy for couples 'activities.' 3-4 months is a long trip.
Wayyy off topic and a serious question: but I've always wondered if anyone has actually ever done that in space.

Anyone know the answer?
True it is, but the average trip is 6-7 months lot's of time for mischief.
Title: Re: ITS Development Updates and Discussion Thread
Post by: Craftyatom on 10/26/2016 08:42 pm
And privacy for couples 'activities.' 3-4 months is a long trip.
Wayyy off topic and a serious question: but I've always wondered if anyone has actually ever done that in space.

Anyone know the answer?

Current answer is a definite "no" - so far, all space travelers have been decently-paid astro/cosmo/taikonauts who are "on the clock", and therefore have certain expectations regarding their activities, whether explicit or implicit.  Also, remember the average age of space travelers so far - there have been those who are younger, but on average, they tend towards middle-age (since these people have already completed advanced degrees, worked in their field, flown in the air force, etc).

There are actually a few competing theories on the subject, much like the competing biological theories prior to launching humans into space - sure, we've had test animals, but humans are quite unique, so there's nothing to say that our experience won't differ.  One way or another, nobody's going to pay the money (a few million for a commercial launch or several hundred thousand for ISS research time, even if NASA/ESA/Roscosmos were interested) to validate things either way, so we're going to have to wait until commercial passengers are much more common, at which point there will be many people in space at the same time with significant and un-restricted free time, which might not even happen until ITS.
Title: Re: ITS Development Updates and Discussion Thread
Post by: sghill on 10/27/2016 12:21 pm
People will want a permanent private space for sleeping, dressing, computer use, etc. It can be small, but it should be dedicated.

"Personal space" is a mid-twentieth-century luxury. Most of the world has nothing close to Western concepts of privacy. I'll  put good money the colonists would rather have cartons of tampons and toothpaste available for several years instead of the ability to read a book alone during the flight.
Title: Re: ITS Development Updates and Discussion Thread
Post by: DOCinCT on 10/27/2016 12:44 pm
The Mars Sleeping Quarter could be:
     1) a cross design of ISS sleeping quarter module and first class seat setting. 
           - the padded seat setting can be converted for sleeping, launching/entry and sofa.
           - use as a working/lecture spaces.
           - repositioned to the wall from the floor if the space ship's internal mid-section is rotating to create an artificial mini-gravity.     
 
     2) a removable module:
           - so it can be transferred to the Mars habitation to minimizing the shock of transition from the cozy spaceship to cold and barren Mars habitation.
           - assigned to each crew so each module can be personalized to keep their privacy and moral high in the space and/or on the ground.
           - so the spaceship can be lightened up for the returning flight. 
Anything designed specifically for a zero-G environment won't work on Mars.  Fancy first class seats are OK for a 12 hour flight but I wouldn't want to sleep on one for weeks or months (besides I'm a side sleeper). 
What "cold and barren Mars habitation"?  Floor space is much less of an issue on Mars compared to the ITS-MPT (that's multi-purpose transporter); rooms will look like rooms and not "cabin" space; I wouldn't characterize that space as "cozy" any more than I would the space on a submarine.  It's austere, cramped and tolerable for 4 to 6 months.
Title: Re: ITS Development Updates and Discussion Thread
Post by: DOCinCT on 10/27/2016 12:53 pm
People will want a permanent private space for sleeping, dressing, computer use, etc. It can be small, but it should be dedicated.

"Personal space" is a mid-twentieth-century luxury. Most of the world has nothing close to Western concepts of privacy. I'll  put good money the colonists would rather have cartons of tampons and toothpaste available for several years instead of the ability to read a book alone during the flight.
I think you are wrong and Robotbeat is right.  Personal space is not a luxury.  Even on submarines there are curtains for the berths (bunks).  Newer designs are "L" shaped so that a person can sit upright while reading / texting or using a tablet or laptop.  We are a far cry from vessels like the Mayflower, estimated passenger space 50 feet by 25 feet with a five-foot ceiling for 100 passengers and no privies.
Title: Re: ITS Development Updates and Discussion Thread
Post by: Req on 10/27/2016 07:11 pm
People will want a permanent private space for sleeping, dressing, computer use, etc. It can be small, but it should be dedicated.

"Personal space" is a mid-twentieth-century luxury. Most of the world has nothing close to Western concepts of privacy. I'll  put good money the colonists would rather have cartons of tampons and toothpaste available for several years instead of the ability to read a book alone during the flight.
I think you are wrong and Robotbeat is right.  Personal space is not a luxury.  Even on submarines there are curtains for the berths (bunks).  Newer designs are "L" shaped so that a person can sit upright while reading / texting or using a tablet or laptop.  We are a far cry from vessels like the Mayflower, estimated passenger space 50 feet by 25 feet with a five-foot ceiling for 100 passengers and no privies.

Fact.  Submarines resupply.

Fact. Mars colonists can't (without spending billions on an interplanetary tampon run).

They are going to cram every ounce of the ITS with pots and pans and pillows and trinkets and music instruments and spices and cooking oil and hair brushes and blankets, ad nauseum because they won't be getting any more.  Every cubic centimeter taken up by walls and "cabins" is space that the crew can't move around in while on the trip, and/ or space that's not being used to ship the neccesities of life when they get there- either for themselves, or for trading.  Is it  really that hard to understand there are no Home Depots and grocery stores up there?  You have to get into a developing world refugee/ survivalist frame of mind.  It was a lack of that sort of thinking that nearly doomed the Jamestown colony.

Just so long as you understand that a) they certainly will resupply at least once every synod, b) "billions" is hyperbole(unless you include initial R&D), and c) the following paragraph is directly contradicting what Musk has stated.

It's also an assumption that they would have the mass budget to fill every space with "pots and pans".
Title: Re: ITS Development Updates and Discussion Thread
Post by: Req on 10/27/2016 07:34 pm
Just so long as you understand that a) they certainly will resupply at least once every synod, b) "billions" is hyperbole(unless you include initial R&D), and c) the following paragraph is directly contradicting what Musk has stated.

It's also an assumption that they would have the mass budget to fill every space with "pots and pans".

Fair enough, as long as you also understand Musk's commentary was referencing pricing once a colony reaches town or city sized and fleets of ships- not those early single ships where there will be no supplies waiting- are traveling back and forth each synod from numerous launching facilities around the globe.  By that point, yes, I'll grant you that cabins are possible, and shipping costs lower.  I'll also state that the ITS will be a different system by then.  None of this applies for the present topic though, which is ITS internal design parameters.  The Mayflower was not a TEU ship.

I agree(mostly*), and Musk has stated, that the first trips will have perhaps a dozen(edit - presumably professionally trained) crew and be cargo-heavy.  I didn't divine the apparent context shift from Robotbeat saying "People will want a permanent private space for sleeping, dressing, computer use, etc. It can be small, but it should be dedicated." to the constraint of "those early single ships where there will be no supplies waiting."

*I don't agree that "the ITS will be a different system by then" in absolute terms.  First you have to define "different system", then I'd still replace "will" with "may".  My opinion is that it is likely that the early ships are refit rather than replaced, with a new design getting phased in concurrently.  My impression is that I think they will be flying the 100-passenger ships long before you do.
Title: Re: ITS Development Updates and Discussion Thread
Post by: Hauerg on 10/27/2016 07:39 pm
Just so long as you understand that a) they certainly will resupply at least once every synod, b) "billions" is hyperbole(unless you include initial R&D), and c) the following paragraph is directly contradicting what Musk has stated.

It's also an assumption that they would have the mass budget to fill every space with "pots and pans".

Fair enough, as long as you also understand Musk's commentary was referencing pricing once a colony reaches town or city sized and fleets of ships- not those early single ships where there will be no supplies waiting- are traveling back and forth each synod from numerous launching facilities around the globe.  By that point, yes, I'll grant you that cabins are possible, and shipping costs lower.  I'll also state that the ITS will be a different system by then.  None of this applies for the present topic though, which is ITS internal design parameters.  The Mayflower was not a TEU ship.
"Single" ships? IIRC he used plural even for the initial expeditions.
(Methinks more likely 2 than 10)
Title: Re: ITS Development Updates and Discussion Thread
Post by: AncientU on 10/27/2016 09:08 pm
Just so long as you understand that a) they certainly will resupply at least once every synod, b) "billions" is hyperbole(unless you include initial R&D), and c) the following paragraph is directly contradicting what Musk has stated.

It's also an assumption that they would have the mass budget to fill every space with "pots and pans".

Fair enough, as long as you also understand Musk's commentary was referencing pricing once a colony reaches town or city sized and fleets of ships- not those early single ships where there will be no supplies waiting- are traveling back and forth each synod from numerous launching facilities around the globe.  By that point, yes, I'll grant you that cabins are possible, and shipping costs lower.  I'll also state that the ITS will be a different system by then.  None of this applies for the present topic though, which is ITS internal design parameters.  The Mayflower was not a TEU ship.
"Single" ships? IIRC he used plural even for the initial expeditions.
(Methinks more likely 2 than 10)

At AMA, EM said 'doubling' each window(synod)...assuming 1 in 2018 and 2 in 2020, that will be 8 in 2024 when first crew is supposed to fly, and by 2030s, a small fleet of ships each synod.
Title: Re: ITS Development Updates and Discussion Thread
Post by: RonM on 10/27/2016 09:19 pm
Just so long as you understand that a) they certainly will resupply at least once every synod, b) "billions" is hyperbole(unless you include initial R&D), and c) the following paragraph is directly contradicting what Musk has stated.

It's also an assumption that they would have the mass budget to fill every space with "pots and pans".

Fair enough, as long as you also understand Musk's commentary was referencing pricing once a colony reaches town or city sized and fleets of ships- not those early single ships where there will be no supplies waiting- are traveling back and forth each synod from numerous launching facilities around the globe.  By that point, yes, I'll grant you that cabins are possible, and shipping costs lower.  I'll also state that the ITS will be a different system by then.  None of this applies for the present topic though, which is ITS internal design parameters.  The Mayflower was not a TEU ship.
"Single" ships? IIRC he used plural even for the initial expeditions.
(Methinks more likely 2 than 10)

At AMA, EM said 'doubling' each window(synod)...assuming 1 in 2018 and 2 in 2020, that will be 8 in 2024 when first crew is supposed to fly, and by 2030s, a small fleet of ships each synod.

2018 and 2020 are Red Dragon launch windows, not ITS. First crew flight, whichever synod that would be, might be two ITS ships.
Title: Re: ITS Development Updates and Discussion Thread
Post by: guckyfan on 10/27/2016 09:37 pm
Privacy and space available. I believe giving each individual a space at least similar to a japanese capsule hotel will be very efficient. People will sleep there and they will spend a significant part of their day there. Freeing up communal space for the 1/3 that are out there at any given time.

On submarines people sleep or they are on station. On transfer to Mars they won't havea stations to attend.
Title: Re: ITS Development Updates and Discussion Thread
Post by: eriblo on 10/27/2016 11:18 pm
I believe there will be smaller cabins, preferably personal, for several reasons (in no particular order):

People will need a private space - I've seen mentioned that interpersonal conflicts are the highest stressor for both long duration space flight and antarctic overwintering. Sure, early pioneers managed all bunched together but remember that there are plenty of examples of even high functioning and stable people losing it and even killing each other (don't play chess :( ).

Space effectiveness - some have suggested hot-bunking but people will likely take up more space when not "in bed". As guckyfan mentioned most will not have anything to do but to sleep, study, exercise and socialize, and I think an open space with less than 2m^3 per person will soon feel crowded even in zero g (think 30 astronauts in the Harmony module instead of 13).

Environmental control/safety - Ventilation is a critical part of zero g interior design due to C02 and dust removal as well as fire safety. I think that the interior might be reconfigurable but all configurations will be thoroughly analysed and validated beforehand. Having the ability to throw up a few fabric walls whenever you feel like a change would be nice until the person two bunks over starts suffocating due to the change in airflow...
Title: Re: ITS Development Updates and Discussion Thread
Post by: Herbie on 10/28/2016 01:26 am
Privacy and space available. I believe giving each individual a space at least similar to a japanese capsule hotel will be very efficient. People will sleep there and they will spend a significant part of their day there. Freeing up communal space for the 1/3 that are out there at any given time.

On submarines people sleep or they are on station. On transfer to Mars they won't havea stations to attend.
I think they will be extremely busy. If I were heading to Mars, I'd be studying everything! By the time I reached Mars, I would be able to take apart, clean, repair, and reassemble the ECLSS. Same for the space suit and Mars suits, and any other system that might be key to survival. Building, tunneling, farming, etc. In fact, the transit would be similar to life on a submarine, eating, sleeping, studying, relaxing, and the possibility that passengers will have duties on ship.
Title: Re: ITS Development Updates and Discussion Thread
Post by: biosehnsucht on 10/28/2016 02:24 am
You can't sleep for 8 hours, then work for 16. Studies have shown that even 8 hour workdays are potentially less efficient over time than 6 hour ones, because the human brain has trouble focusing on tasks for so long.

You're going to need to kill a lot of time one way or another, in a way that isn't too mentally taxing (i.e. not study or work).
Title: Re: ITS Development Updates and Discussion Thread
Post by: Herbie on 10/28/2016 03:55 am
You can't sleep for 8 hours, then work for 16. Studies have shown that even 8 hour workdays are potentially less efficient over time than 6 hour ones, because the human brain has trouble focusing on tasks for so long.

You're going to need to kill a lot of time one way or another, in a way that isn't too mentally taxing (i.e. not study or work).
IIRC, submarines are on an 18 hour "day"  (6 on, 6 off, and 6 asleep, although the ordering may be different, and important) The off period was used for both relaxation and study. Much if the study time was devoted to systems on the sub, especially for the officers.

I suspect that most of the initial colonists will be naturally inclined towards learning.

Who is going to want to ship out to Mars along with a ship-load of full-time gamers? Unless they are practicing remote-control of Mars droids, they'll be useless when you reach your new home.
Title: Re: ITS Development Updates and Discussion Thread
Post by: guckyfan on 10/28/2016 07:45 am
I suspect that most of the initial colonists will be naturally inclined towards learning.

A strong argument in favor of a small private space. Perfectly suited for learning as well as watching movies, playing games, reading........
Title: Re: ITS Development Updates and Discussion Thread
Post by: CuddlyRocket on 10/29/2016 12:45 am
People will need a private space - I've seen mentioned that interpersonal conflicts are the highest stressor for both long duration space flight and antarctic overwintering. Sure, early pioneers managed all bunched together but remember that there are plenty of examples of even high functioning and stable people losing it and even killing each other (don't play chess :( ).

Well, not with each other. Postal chess with someone on Earth will probably be OK! :)

Interpersonal conflicts, even if only at the level of personality clashes, are an argument for ensuring that there is more than one communal space on the ITS (and any Mars base or colony). You don't want to find that someone is really irritating you and then realise you've nowhere to get away from them other than your private - and lonely - space.

I'd also suggest that if thought was given to including a big screen for communal viewing purposes that there be more than one of them in separate spaces. Back at the dawn of civilisation when I was a student, I remember the sometime vicious infighting over what channel would be on in the student hall of residence TV room; even though the Students Union building had TV rooms for each channel - all three of them - and was less than five minutes away (people didn't see why they had to walk every week!).
Title: Re: ITS Development Updates and Discussion Thread
Post by: Jim on 11/05/2016 10:25 am

Trucks?  Take it back to the LOX plant.

Rent the LOX for the test; pay for any LOX used and transportation/handling/overhead costs to the LOX producer as negotiated as part of the deal; return the rest back into the supply system to be sold as LOX as usual; cleaned/refined if necessary.

Not feasible.  Nobody will take the LOX back. 
a.  Its quality is unknown.  Don't know what contaminates are in it.
b.  There is likely no way to put in back into the LOX plant
c.  "cleaned/refined" would be by letting it vaporize
Title: Re: ITS Development Updates and Discussion Thread
Post by: Flying Beaver on 11/11/2016 10:24 pm
Test tank sighted! From Reddit user "Death_Cog_Unit"

"Hey guys, greetings from Anacortes, WA.
Thought you might enjoy some pictures I took. Yes, my camera is a potato.
A few years ago one of the large manufacturing buildings in our small town got bought by a bunch of strange suits, supposedly by Boeing for special projects. Extremely tight security.
Even the shipping containers outside had biometric locks on them.
But yesterday they brought this thing out and loaded it onto a barge, supposedly for "destructive testing".
Less than 24 hours later, it has already returned seemingly intact.
They could not have gone very far at all, so everybody around here is pretty curious about what they actually did.
I saw a few man-sized silver tanks that were being moved off the barge as well, which were also venting."

I had a look a marine traffic to track the tug that was pulling the barge, seems like they just went round in circles.
Title: Re: ITS Development Updates and Discussion Thread
Post by: meekGee on 11/11/2016 11:12 pm
I just love finding out how ahead they are.

They took over the building a few years ago. Want to scroll back a few year in the forum and see how many people were still thinking the whole "Mars Thing" is just an overblown fantasy designed to keep the young engineers from noticing they are not getting paid well"?

So now fast-forward to today...  Where is development standing currently?  What does Steve Jurvetson know?

That picture/story made my day...
Title: Re: ITS Development Updates and Discussion Thread
Post by: Raul on 11/11/2016 11:24 pm
Here are more photos (http://imgur.com/a/dQw2U)

And video of unloading...

https://www.youtube.com/watch?v=0NIeNCQFXno
Title: Re: ITS Development Updates and Discussion Thread
Post by: biosehnsucht on 11/11/2016 11:36 pm
To be fair, it may not have been SpaceX who took over the building, but Janicki Industries, and they may actually intend to build stuff for Boeing and others, as well, not simply wait around to build the prototype tank for the ITS.
Title: Re: ITS Development Updates and Discussion Thread
Post by: Robotbeat on 11/12/2016 01:24 am
Interesting. Reddit thread: https://www.reddit.com/r/spacex/comments/5chddp/pictures_of_the_its_lox_testing_tank_being_taken/?st=ivel7t11&sh=83c9f556

by the way, I wonder where this building is? Can we find out?
Title: Re: ITS Development Updates and Discussion Thread
Post by: matthewkantar on 11/12/2016 08:38 am
I suspected the tank was nowhere near SpaceX's usual facilities.
Title: Re: ITS Development Updates and Discussion Thread
Post by: docmordrid on 11/12/2016 09:22 am
They could have taken Rt. 20 from the Janicki shops in Sedro-Woolley to the Anacortes Marina. 23 miles. Done overnight for minimal disruption.

https://goo.gl/maps/SjwuMG3FWNF2
Title: Re: ITS Development Updates and Discussion Thread
Post by: Raul on 11/12/2016 12:55 pm
It turned out (https://www.reddit.com/r/spacex/comments/5chddp/pictures_of_the_its_lox_testing_tank_being_taken/d9x0caf/) that the ITS LOX tank has been built in this large building (https://www.google.com/maps/d/viewer?mid=1wvgFIPuOmI8da9EIB88tHo9vamo&ll=48.504862806622306%2C-122.60536595031641&z=16) - former Pacific Marine Center.
Title: Re: ITS Development Updates and Discussion Thread
Post by: DOCinCT on 11/12/2016 01:24 pm
It turned out (https://www.reddit.com/r/spacex/comments/5chddp/pictures_of_the_its_lox_testing_tank_being_taken/d9x0caf/) that the ITS LOX tank has been built in this large building (https://www.google.com/maps/d/viewer?mid=1wvgFIPuOmI8da9EIB88tHo9vamo&ll=48.504862806622306%2C-122.60536595031641&z=16) - former Pacific Marine Center.
So, if you want to hide something, do it in plain sight.
Title: Re: ITS Development Updates and Discussion Thread
Post by: matthewkantar on 11/12/2016 02:29 pm
A little bit further down the page that Raul linked, a poster named rebootyourbrainstem posted a picture they found on google of the inside of the building. It looks correct.

Matthew
Title: Re: ITS Development Updates and Discussion Thread
Post by: Navier–Stokes on 11/16/2016 03:44 pm
Official confirmation of a successful pressure test:

Quote from: https://twitter.com/SpaceX/status/798929028207886337
SpaceX ‏@SpaceX   

Successfully tested the prototype Mars tank last week. Hit both of our pressure targets – next up will be full cryo testing.

8:41 AM - 16 Nov 2016

Update: Video of tank transport released on Instagram (https://www.instagram.com/p/BM4P6b_g2N9/?hl=en).
Title: Re: ITS Development Updates and Discussion Thread
Post by: TrueBlueWitt on 11/16/2016 05:57 pm
Official confirmation of a successful pressure test:

Quote from: https://twitter.com/SpaceX/status/798929028207886337
SpaceX ‏@SpaceX   

Successfully tested the prototype Mars tank last week. Hit both of our pressure targets – next up will be full cryo testing.

8:41 AM - 16 Nov 2016

Update: Video of tank transport released on Instagram (https://www.instagram.com/p/BM4P6b_g2N9/?hl=en).

Look at the size of the crane at the end they used to lift it onto the barge. You can tell that tank must be pretty light!
Title: Re: ITS Development Updates and Discussion Thread
Post by: The Amazing Catstronaut on 11/16/2016 09:18 pm
Dazzling. There are trial components for a mars spaceship undergoing qualification testing (albeit, the final tank is going to be longer, still).

I'm.... still processing that thought... give me a while....


I wonder how much that tank swings. It's light and huge, the pictures don't truly reveal how huge - might be a bit of a sail in higher winds. I'm not foolhardy enough to be concerned that they'll actually drop the tank moving it from barge to shore however.

Title: Re: ITS Development Updates and Discussion Thread
Post by: meekGee on 11/16/2016 10:15 pm
Dazzling. There are trial components for a mars spaceship undergoing qualification testing (albeit, the final tank is going to be longer, still).

I'm.... still processing that thought... give me a while....


I wonder how much that tank swings. It's light and huge, the pictures don't truly reveal how huge - might be a bit of a sail in higher winds. I'm not foolhardy enough to be concerned that they'll actually drop the tank moving it from barge to shore however.

The video sure shows the size though.
Title: Re: ITS Development Updates and Discussion Thread
Post by: RoboGoofers on 11/17/2016 03:36 pm
It turned out (https://www.reddit.com/r/spacex/comments/5chddp/pictures_of_the_its_lox_testing_tank_being_taken/d9x0caf/) that the ITS LOX tank has been built in this large building (https://www.google.com/maps/d/viewer?mid=1wvgFIPuOmI8da9EIB88tHo9vamo&ll=48.504862806622306%2C-122.60536595031641&z=16) - former Pacific Marine Center.

Where's all the tooling? i'm skeptical that it was built at a marina. It'd be hard to hide when moving it, but nobody was expecting ITS parts to be built in Anacortes, WA, so it might have been observed as nothing more than a regular oversized load.


It also seems odd that they'd take it up to Bellingham bay to do the test instead of just doing it in Samish bay.
Title: Re: ITS Development Updates and Discussion Thread
Post by: JamesH65 on 11/17/2016 04:04 pm
It turned out (https://www.reddit.com/r/spacex/comments/5chddp/pictures_of_the_its_lox_testing_tank_being_taken/d9x0caf/) that the ITS LOX tank has been built in this large building (https://www.google.com/maps/d/viewer?mid=1wvgFIPuOmI8da9EIB88tHo9vamo&ll=48.504862806622306%2C-122.60536595031641&z=16) - former Pacific Marine Center.

Where's all the tooling? i'm skeptical that it was built at a marina. It'd be hard to hide when moving it, but nobody was expecting ITS parts to be built in Anacortes, WA, so it might have been observed as nothing more than a regular oversized load.


It also seems odd that they'd take it up to Bellingham bay to do the test instead of just doing it in Samish bay.

Imagine trying to move this on normal roads....or even abnormal ones.

https://www.youtube.com/watch?v=wXKpZCVytJ0

Title: Re: ITS Development Updates and Discussion Thread
Post by: eriblo on 11/17/2016 04:40 pm
It turned out (https://www.reddit.com/r/spacex/comments/5chddp/pictures_of_the_its_lox_testing_tank_being_taken/d9x0caf/) that the ITS LOX tank has been built in this large building (https://www.google.com/maps/d/viewer?mid=1wvgFIPuOmI8da9EIB88tHo9vamo&ll=48.504862806622306%2C-122.60536595031641&z=16) - former Pacific Marine Center.

Where's all the tooling? i'm skeptical that it was built at a marina. It'd be hard to hide when moving it, but nobody was expecting ITS parts to be built in Anacortes, WA, so it might have been observed as nothing more than a regular oversized load.


It also seems odd that they'd take it up to Bellingham bay to do the test instead of just doing it in Samish bay.

Imagine trying to move this on normal roads....or even abnormal ones.

https://www.youtube.com/watch?v=wXKpZCVytJ0
My guess is that a company that specializes in composites and highlights their ability to make prototypes on site has a set up that can fit in the 3/4 of the building which we haven't seen in pictures (especially if cleaned up for those pictures). It's also unfair to say that it was built at a marina. It was built in a former boat repair and servicing building, an operation likely involving cranes, big loads and some composites, that was allegedly later used by Boeing to test out their 777 tooling. Located at a marina ;)
Title: Re: ITS Development Updates and Discussion Thread
Post by: matthewkantar on 11/17/2016 05:10 pm
I too am skeptical they built the tank in that facility, but how they got it there if it was built at some other site is not that mysterious. It could have come in unnoticed by barge. It would take a real space nut to see that tank prior to the ITS announcement and guess its use. I suppose it could have been flown in by helicopter as well.

I am really curious about the tooling. I imagined a giant turning last with robots laying down mono-directional fiber. The tank looks like is was made in two pieces on a hemispherical mold and then joined together at the equator. The inside looks like a layup of individual squares. Is it possible that no winding was done? Maybe they built the two halfs, put them together and wound fiber over the assembled structure?

Matthew
Title: Re: ITS Development Updates and Discussion Thread
Post by: docmordrid on 11/17/2016 05:20 pm
Standard domes with cylindrical extensions could make some parts usable in both spaceship and booster. The thrust strucure/"domes" would differ, as would the concave methane tank upper dome.
Title: Re: ITS Development Updates and Discussion Thread
Post by: Rei on 11/18/2016 12:13 am
Official confirmation of a successful pressure test:

Quote from: https://twitter.com/SpaceX/status/798929028207886337
SpaceX ‏@SpaceX   

Successfully tested the prototype Mars tank last week. Hit both of our pressure targets – next up will be full cryo testing.

8:41 AM - 16 Nov 2016

Update: Video of tank transport released on Instagram (https://www.instagram.com/p/BM4P6b_g2N9/?hl=en).

Pressurized with what substance?  To what pressure targets, versus what goal?

I'm in the "apprehensively watching" category.  Going from "nobody's ever flown an orbital-intent composite rocket LOX tank at any scale" to "by far the largest rocket in the world relying on them" is a huge leap they're trying to take. Composites and cryogenics, especially LOX, is a seriously challenging task.  I just don't want to see the largest rocket in history turn into the largest rocket explosion in history.  So.... I'm really hoping they can get everything ironed out in the testing.
Title: Re: ITS Development Updates and Discussion Thread
Post by: livingjw on 11/18/2016 12:24 am
I suspect that the initial cryogenic  tests will be done with liquid nitrogen, since it sounded like they didn't have an internal coating yet.
Title: Re: ITS Development Updates and Discussion Thread
Post by: Rei on 11/18/2016 01:21 am
I suspect that the initial cryogenic  tests will be done with liquid nitrogen, since it sounded like they didn't have an internal coating yet.

A very different beast, if so.

But, at least it would show any cracking under loading at cryogenic temperatures.
Title: Re: ITS Development Updates and Discussion Thread
Post by: gongora on 11/18/2016 01:35 am
Someone posted a link on Reddit (https://www.reddit.com/r/spacex/comments/5dcyk8/boeing_previously_did_experimental_work_in/) to this article, which is a nice intro to Janicki Industries.  It's a few years old, so they could have added other buildings since the article was written.

High-Performance Composites: Janicki Industries: Breaking the mold (http://www.compositesworld.com/articles/janicki-industries-breaking-the-mold)
Title: Re: ITS Development Updates and Discussion Thread
Post by: docmordrid on 11/18/2016 03:49 am
This sounds vaguely familiar... ;)

Quote
“If we haven’t thrown anything away in awhile,” quips one manager, “Peter [CEO] will challenge that we’re not pushing boundaries enough.”
Title: Re: ITS Development Updates and Discussion Thread
Post by: JamesH65 on 11/18/2016 01:23 pm
I too am skeptical they built the tank in that facility, but how they got it there if it was built at some other site is not that mysterious. It could have come in unnoticed by barge. It would take a real space nut to see that tank prior to the ITS announcement and guess its use. I suppose it could have been flown in by helicopter as well.

I am really curious about the tooling. I imagined a giant turning last with robots laying down mono-directional fiber. The tank looks like is was made in two pieces on a hemispherical mold and then joined together at the equator. The inside looks like a layup of individual squares. Is it possible that no winding was done? Maybe they built the two halfs, put them together and wound fiber over the assembled structure?

Matthew

Something that big would unlikely go unnoticed...whether barged or helicoptered. Certainly not road transported. Doesn't need a space nut - anyone seeing that would photograph it and ask what the hell it was somewhere that would have been spotted.
Title: Re: ITS Development Updates and Discussion Thread
Post by: JasonAW3 on 11/18/2016 01:40 pm
I too am skeptical they built the tank in that facility, but how they got it there if it was built at some other site is not that mysterious. It could have come in unnoticed by barge. It would take a real space nut to see that tank prior to the ITS announcement and guess its use. I suppose it could have been flown in by helicopter as well.

I am really curious about the tooling. I imagined a giant turning last with robots laying down mono-directional fiber. The tank looks like is was made in two pieces on a hemispherical mold and then joined together at the equator. The inside looks like a layup of individual squares. Is it possible that no winding was done? Maybe they built the two halfs, put them together and wound fiber over the assembled structure?

Matthew

Something that big would unlikely go unnoticed...whether barged or helicoptered. Certainly not road transported. Doesn't need a space nut - anyone seeing that would photograph it and ask what the hell it was somewhere that would have been spotted.

I could have been brought in by helicopter, on an overcast night.  If this location is as isolated or has as much air traffic as I suspect, it is possible that it would have gone unnoticed.
Title: Re: ITS Development Updates and Discussion Thread
Post by: matthewkantar on 11/18/2016 09:31 pm
I often see gigantic oversized loads rolling down the thoroughfare near me. Most people don't give them a second look. I can identify maybe a third of them, but as curious as I am, I don't take pictures and post them all over in an attempt to identify a load. Seeing an obviously rocket shaped thing on the interstate with a SpaceX logo on it is one thing, seeing a giant disembodied tank is another. If I saw that from a distance, I might have thought:"Wow, did not know hey made water tower tanks in one piece." Also, one would have to get really close to notice it was carbon fiber.

Matthew
Title: Re: ITS Development Updates and Discussion Thread
Post by: oldAtlas_Eguy on 11/19/2016 03:09 pm
Someone posted a link on Reddit (https://www.reddit.com/r/spacex/comments/5dcyk8/boeing_previously_did_experimental_work_in/) to this article, which is a nice intro to Janicki Industries.  It's a few years old, so they could have added other buildings since the article was written.

High-Performance Composites: Janicki Industries: Breaking the mold (http://www.compositesworld.com/articles/janicki-industries-breaking-the-mold)
Looking through their news/blog list no mention of anything for SpaceX.
Title: Re: ITS Development Updates and Discussion Thread
Post by: DOCinCT on 12/13/2016 12:26 pm
Came across this article in CompositesWorld; dated from 2013.  Interesting discussion of large scale composite fabrication (in this case a 10meter diameter fairing for the SLS).  Steps involved are in the side bar. Having worked on the LOX tank prototype, I wonder is Janicki will be involved in fabricating the hull for ITS.
http://www.compositesworld.com/articles/tooling-up-for-larger-launch-vehicles 
Title: Re: ITS Development Updates and Discussion Thread
Post by: jpo234 on 02/07/2017 08:33 am
The ITS tank is on the move again in Anacortes:
https://imgur.com/a/nDyLI
Title: Re: ITS Development Updates and Discussion Thread
Post by: docmordrid on 02/07/2017 03:33 pm
The ITS tank is on the move again in Anacortes:
https://imgur.com/a/nDyLI

Boosted the gain a tad. Clearly it snowed and they cleared the lot, an authenticity concern on rediit was a recent snowstorm but no piles seen. Round 2 tests of some kind, and in cold temps. Hmmmmm....

Title: Re: ITS Development Updates and Discussion Thread
Post by: AncientU on 02/07/2017 09:01 pm
The ITS tank is on the move again in Anacortes:
https://imgur.com/a/nDyLI

Boosted the gain a tad. Clearly it snowed and they cleared the lot, an authenticity concern on rediit was a recent snowstorm but no piles seen. Round 2 tests of some kind, and in cold temps. Hmmmmm....

Balmy temps for a cryo tank
Title: Re: ITS Development Updates and Discussion Thread
Post by: Flying Beaver on 02/08/2017 02:56 am
Looks like it is cryo testing. Lots of LOX/water vapor venting around the tank in this pic via Instagram.

https://www.instagram.com/p/BQPFQ52gjfn/?tagged=spacex
Title: Re: ITS Development Updates and Discussion Thread
Post by: docmordrid on 02/08/2017 05:06 am
Looks like it is cryo testing. Lots of LOX/water vapor venting around the tank in this pic via Instagram.

https://www.instagram.com/p/BQPFQ52gjfn/?tagged=spacex

Frost extending half way up? After boosting the brightness it looks so.
Title: Re: ITS Development Updates and Discussion Thread
Post by: ZachF on 02/09/2017 07:21 pm
I wonder if this large tank contains the landing tank inside:

http://i.imgur.com/GsyREf7.png
Title: Re: ITS Development Updates and Discussion Thread
Post by: matthewkantar on 02/09/2017 07:40 pm
From the pictures of the inside of the tank at the IAC talk, there did not appear to be any tank inside it, or any way to get one in there.

Matthew

Edited to add picture from inside of tank.
Title: Re: ITS Development Updates and Discussion Thread
Post by: Oersted on 02/09/2017 10:58 pm
I wonder if this large tank contains the landing tank inside:

I don't think we should consider this tank as anything but a proof-of-concept test article. 
Title: Re: ITS Development Updates and Discussion Thread
Post by: chalz on 02/10/2017 03:06 am
I wonder if this large tank contains the landing tank inside:

I don't think we should consider this tank as anything but a proof-of-concept test article.

The entire ITS program up to the first launch was said to need on the order of $10b. This is bound to be the merest sketch in comparison with what's needed. How much would this test program cost? $1m?
Title: Re: ITS Development Updates and Discussion Thread
Post by: Johnnyhinbos on 02/10/2017 03:13 am
I wonder if this large tank contains the landing tank inside:

I don't think we should consider this tank as anything but a proof-of-concept test article.
Wait, you're telling me that the production tanks won't have crystal chandeliers?


Sent from my iPad using Tapatalk
Title: Re: ITS Development Updates and Discussion Thread
Post by: Bynaus on 02/10/2017 07:48 am
But wouldn't it be a pity to just throw that big tank away once the current test program ends? Why not make use of it in an incremental testing approach: mount it on top of a harness with some first generation full-scale Raptors in it, add another tank (for LNG) on top, add some retractable legs and start launching / landing the thing in a Grasshopper-style fashion? Improve along as you go (e.g., aeroshell, TPS, etc.), until you have a first generation ITS spaceship (or tanker).
Title: Re: ITS Development Updates and Discussion Thread
Post by: vaporcobra on 02/10/2017 08:33 am
But wouldn't it be a pity to just throw that big tank away once the current test program ends? Why not make use of it in an incremental testing approach: mount it on top of a harness with some first generation full-scale Raptors in it, add another tank (for LNG) on top, add some retractable legs and start launching / landing the thing in a Grasshopper-style fashion? Improve along as you go (e.g., aeroshell, TPS, etc.), until you have a first generation ITS spaceship (or tanker).

Severely diminishing returns for something like that. IMHO, SpaceX needs to focus the vast majority of its resources and time on Raptor and carbon composite tank technology until they have both highly stable and dependable. Anything else currently would be a severe waste of time, and there is a good chance that the design of the tanks may change considerably over the course of testing. In that case, it would be exceptionally pointless to further utilize this tank.
Title: Re: ITS Development Updates and Discussion Thread
Post by: AncientU on 02/10/2017 10:35 am
Looks like it is cryo testing. Lots of LOX/water vapor venting around the tank in this pic via Instagram.

https://www.instagram.com/p/BQPFQ52gjfn/?tagged=spacex

Frost extending half way up? After boosting the brightness it looks so.

Interesting that it is being filled/tested in port.  Confidence in the structural integrity must be high -- that's a lot of methane (or Lox or LN2, whatever) close to population.
Title: Re: ITS Development Updates and Discussion Thread
Post by: docmordrid on 02/10/2017 01:14 pm
Initial cryotests are most likely LN2, not a propellant, but yeah...Pretty confident. Pretty far along too given its only about 5+ months after the announcement. Raptors been moving along too, though no videos have been released.
Title: Re: ITS Development Updates and Discussion Thread
Post by: matthewkantar on 02/10/2017 01:35 pm
I would guess they load it with cryogen dockside, then take it out to sea and pressurize it. So the dangerous part is done far from assets and people.

Matthew
Title: Re: ITS Development Updates and Discussion Thread
Post by: jpo234 on 02/10/2017 02:10 pm
Raptors been moving along too, though no videos have been released.
I'm puzzled that there are no news about Raptor since the test fire. Do you have something to share?
Title: Re: ITS Development Updates and Discussion Thread
Post by: Kaputnik on 02/11/2017 08:07 pm
Do we know if this test tank is built to flight-like mass fraction?
Title: Re: ITS Development Updates and Discussion Thread
Post by: Jarnis on 02/17/2017 07:47 am
Tank testing of the first test article appears... finished.

http://imgur.com/a/bGHR6

No idea if the test was intentionally to destruction, or if the test result was a surprise. In any case, seems like they will need a new tank.

Source: https://www.reddit.com/r/spacex/comments/5ul1du/remains_of_the_its_composite_tank_in_anacortes_wa/
Title: Re: ITS Development Updates and Discussion Thread
Post by: Kaputnik on 02/17/2017 10:20 am
I don't want to come over all doom and gloom, but IMHO I'd be very surprised if this was intentional. Off to watch Elon's twitter feed for the rest of the day...
Title: Re: ITS Development Updates and Discussion Thread
Post by: Chris Bergin on 02/17/2017 11:46 am
I'll ask around. But I'm reasonably sure "the plan" was to test it to breaking point....and that's what we're seeing here (the aftermath and I'm sure that's not where the test was conducted, but where they have brought the remains).

RIP Test Tank.
Title: Re: ITS Development Updates and Discussion Thread
Post by: Jarnis on 02/17/2017 12:00 pm
Source thread in Reddit confirms that this is the leftovers - whatever happened, happened out at sea on the barge and these are the bits that were offloaded from it afterwards.
Title: Re: ITS Development Updates and Discussion Thread
Post by: DOCinCT on 02/17/2017 12:16 pm
Is this the carbon fiber composite component or an internal bladder of some sort? 
Aren't the tanks part of the overall structure of the rocket?
Title: Re: ITS Development Updates and Discussion Thread
Post by: Jarnis on 02/17/2017 01:23 pm
Is this the carbon fiber composite component or an internal bladder of some sort? 
Aren't the tanks part of the overall structure of the rocket?

It was a carbon fiber tank. Not a bladder.

This: https://i.redd.it/gd6mlp0gs4ox.png

Except it is now somewhat broken  :'(
Title: Re: ITS Development Updates and Discussion Thread
Post by: matthewkantar on 02/17/2017 01:28 pm
Very much a Humpty Dumpty type situation.

Matthew
Title: Re: ITS Development Updates and Discussion Thread
Post by: robert_d on 02/17/2017 01:37 pm
A full sized Raptor powered carbon composite reusable second stage, with a reusable payload fairing, flown  on a Falcon dual core booster could retire a lot of risk.
Title: Re: ITS Development Updates and Discussion Thread
Post by: guckyfan on 02/17/2017 04:17 pm
A full sized Raptor powered carbon composite reusable second stage, with a reusable payload fairing, flown  on a Falcon dual core booster could retire a lot of risk.

Inventing a new 2 core booster for that purpose? If it  can fly on F9, fine but unlikely. Otherwise use a FH.
Title: Re: ITS Development Updates and Discussion Thread
Post by: philw1776 on 02/17/2017 07:19 pm
A full sized Raptor powered carbon composite reusable second stage, with a reusable payload fairing, flown  on a Falcon dual core booster could retire a lot of risk.

No dual booster exists nor is it needed.
A simpler more direct path for less R&D $ from another thread...

Per Musk's presentation, instead of building & testing the 42 engine booster first, he moves right to the 2nd stage.  Here's one scalable, incremental, direct pathway SX engineers could follow.

Build the simpler to outfit 90 tonne ITS stage 2 Tanker version first.
Equip with just the 3 SL Raptors to flight test them and the stage 2 airframe, TPS & avionics
~700 tonnes of propellant and the 90 tonne craft can get up to ~5 Km/sec (rocket equation)
Fly & recover, testing heat shield and airframe at lower stress and qualifying the avionics


Next build initial booster stage with ~ half the engines, but full sized airframe & tanks (no extra tooling costs)
Maybe equip 2nd stage with some Rvacs, or do so later after 1st flights
Then
Execute orbital tests & re-entry with minimal "payload" to LEO
Proves out landing technique for booster stage & more Raptor engine flight experience

and so on...

I'm convinced SpaceX's engineers will come up with a more clever, lower cost approach than this, an approach that does not divert them from their goal and require non-essential R&D time and money for spacecraft not utilized in the Mars settlement core mission.
Title: Re: ITS Development Updates and Discussion Thread
Post by: ZachF on 02/17/2017 07:30 pm
I don't want to come over all doom and gloom, but IMHO I'd be very surprised if this was intentional. Off to watch Elon's twitter feed for the rest of the day...

Unfortunately I'm in agreement. While it's a given they'll have to test it to failure at some point it seems a bit too early at this stage for that to be the case. I don't know why they'd want to "blow it up" now without performing a few more tests first... But I could be wrong of course.
Title: Re: ITS Development Updates and Discussion Thread
Post by: philw1776 on 02/17/2017 08:03 pm
Sometimes I wonder if all this Mars Colony stuff is a brilliant cover for a billionaire who simply loves to indulge his boyish penchant for blowing stuff up.  Nah!
Title: Re: ITS Development Updates and Discussion Thread
Post by: ZachF on 02/19/2017 12:33 pm
So if all-composite tanks don't pan out (at least for O2 tanks), what kind of weight increase are we talking about?
Title: Re: ITS Development Updates and Discussion Thread
Post by: guckyfan on 02/19/2017 12:37 pm
So if all-composite tanks don't pan out (at least for O2 tanks), what kind of weight increase are we talking about?

That is not going to happen. They will put a liner in. But what happened was with nitrogen. So something general they need to fix if it was indeed not a test to destruction.
Title: Re: ITS Development Updates and Discussion Thread
Post by: envy887 on 02/19/2017 12:47 pm
So if all-composite tanks don't pan out (at least for O2 tanks), what kind of weight increase are we talking about?

Depends how thick the Invar liner needs to be and whether they can use its strength to reduce the weight of the composite.

If it's 1 mm thick over the area of the ship's LOX tank, that only adds about 3 tonnes.
Title: Re: ITS Development Updates and Discussion Thread
Post by: ZachF on 02/19/2017 01:02 pm
So if all-composite tanks don't pan out (at least for O2 tanks), what kind of weight increase are we talking about?

Depends how thick the Invar liner needs to be and whether they can use its strength to reduce the weight of the composite.

If it's 1 mm thick over the area of the ship's LOX tank, that only adds about 3 tonnes.

And triple that roughly for the booster?

If this test was not purposely to destruction (which I am almost certain it wasn't, Elon probably would have tweeted a video of it) they should probably just abandon the linerless route entirely. With all of the problems they have had with LOX submerged COPVs it just seems like it will be a Sisyphean task making it work, and that there will be problems in the future making them last 100-1000 launches with all the various stresses involved.
Title: Re: ITS Development Updates and Discussion Thread
Post by: guckyfan on 02/21/2017 10:07 am
From the CRS-11 discussion thread.

http://forum.nasaspaceflight.com/index.php?topic=42229.msg1645226#msg1645226


https://www.youtube.com/watch?v=O56oBIwEtp0

So much for the impossible ITS solar fan panel.

Edit: I have no idea how this works.
Title: Re: ITS Development Updates and Discussion Thread
Post by: nacnud on 02/21/2017 11:05 am
I think it works like this from roccor (http://www.roccor.com/products/slit-tube-booms/)
Title: Re: ITS Development Updates and Discussion Thread
Post by: Rei on 02/21/2017 12:13 pm
Yes, both videos I posted are from Roccor.  It's a very interesting technology.  I'd been researching collapsible trusses for Venus habitat usage, and there's a good number of designs out there; however, most are still predominantly empty airspace in their packed state .  Roccor's is the only one I've come across that lets you pack a truss or tube down to not much more volume than its bulk density would imply, without a major loss in structural strength.

Also, it's good to pair the above image with the following so that you can see why it doesn't come apart:

(http://www.roccor.com/wp-content/uploads/2013/08/seam-lock.jpg)

They report 50% of the torsional stiffness of a fully closed composite tube, which isn't bad at all.  When it comes to tubes and trusses, you can easily overcome that with just a small increase in diameter because bending of a truss or tube is proportional to its diameter cubed.

More info about the Roccor tech here:

http://www.altius-space.com/wp-content/uploads/2014/08/Roccor_SmallSat_Paper_Final_2014-06-20.pdf
Title: Re: ITS Development Updates and Discussion Thread
Post by: JamesH65 on 02/22/2017 09:25 am
The stored device is hollow AFAICT, which could also provide extra storage for long thin things, or fluids.

Nice tech.
Title: Re: ITS Development Updates and Discussion Thread
Post by: DanielW on 02/22/2017 03:20 pm
I wonder why they don't just put a zipper on the edges. For the case in the video the tube is never completely collapsed so you would not need some fancy way to start the zipper.
Title: Re: ITS Development Updates and Discussion Thread
Post by: Lars-J on 02/23/2017 03:52 am
I wonder why they don't just put a zipper on the edges. For the case in the video the tube is never completely collapsed so you would not need some fancy way to start the zipper.

Surely you have experienced a broken zipper.  :D If the rigidity is sufficient, why add extra failure modes?
Title: Re: ITS Development Updates and Discussion Thread
Post by: DanielW on 02/23/2017 08:08 pm
I wonder why they don't just put a zipper on the edges. For the case in the video the tube is never completely collapsed so you would not need some fancy way to start the zipper.

Surely you have experienced a broken zipper.  :D If the rigidity is sufficient, why add extra failure modes?

Sure broken zippers exist, but they are hardly a common failure mode. I am hard-pressed to think of a more reliable fastener. I don't think I have ever experienced a failure of a well made zipper and that over cycles between the 10's of thousands and millions.
Title: Re: ITS Development Updates and Discussion Thread
Post by: Rei on 02/23/2017 10:54 pm
It really isn't needed, just something extra to jam, and significant extra weight (remember, these are composites - thin, very light for their strength).  There's not a lot of force trying to push together or pull apart the far side of the tube.  When you bend a linear object, you put the near side into compression and the far side into tension, along the axis of that object.  So it's stretching on that edge, but not pushing together / pulling apart.  Torsion can do that, but the fasteners are designed to be good enough to deal with torsion.
Title: Re: ITS Development Updates and Discussion Thread
Post by: jpo234 on 02/24/2017 07:01 am
I'll ask around.

Got any answers?
Title: Re: ITS Development Updates and Discussion Thread
Post by: JamesH65 on 02/24/2017 09:09 am
It really isn't needed, just something extra to jam, and significant extra weight (remember, these are composites - thin, very light for their strength).  There's not a lot of force trying to push together or pull apart the far side of the tube.  When you bend a linear object, you put the near side into compression and the far side into tension, along the axis of that object.  So it's stretching on that edge, but not pushing together / pulling apart.  Torsion can do that, but the fasteners are designed to be good enough to deal with torsion.

Torsion seems to be the only thing that could be improved. I'd be inclined to add a sawtooth pattern on each edge, as it unfurls the sawtooths engage. This would provide extra torsion resistance. Not the same strength as if they were fixed (perhaps a tape over the join would improve things even more), but would be better than straight edges. Almost like a zipper, but without any extra hardware.
Title: Re: ITS Development Updates and Discussion Thread
Post by: Burninate on 02/25/2017 08:17 pm
So if all-composite tanks don't pan out (at least for O2 tanks), what kind of weight increase are we talking about?

Depends how thick the Invar liner needs to be and whether they can use its strength to reduce the weight of the composite.

If it's 1 mm thick over the area of the ship's LOX tank, that only adds about 3 tonnes.

I spent most of a year iterating my way through a projected MCT built of aluminum and moderate-pressure engines.  The case for Mars missions does close, but a few things, like 1-synod reuse, get very difficult.  I also ended up penciling in a system of additional propellant shipments sent to Mars orbit via a long SEP trip.

http://forum.nasaspaceflight.com/index.php?topic=37808.msg1589654#msg1589654

In that analysis, the LOX tank sidewall comes in at 34mm, the CH4 tank & hab sidewall 7.5mm.  Tank skin mass for the interplanetary stage alone is  ~46 tons, hab skin mass is ~8 tons. This is not counting ribs, trusses, heatshields, vacuum insulation, vacuum flask, plumbing, engines, anything.  There's some mild sandbagging in there (in a pessimistic assumed tensile strength for aluminum) to add a margin of error.
Title: Re: ITS Development Updates and Discussion Thread
Post by: envy887 on 02/25/2017 08:51 pm
So if all-composite tanks don't pan out (at least for O2 tanks), what kind of weight increase are we talking about?

Depends how thick the Invar liner needs to be and whether they can use its strength to reduce the weight of the composite.

If it's 1 mm thick over the area of the ship's LOX tank, that only adds about 3 tonnes.

I spent most of a year iterating my way through a projected MCT built of aluminum and moderate-pressure engines.  The case for Mars missions does close, but a few things, like 1-synod reuse, get very difficult.  I also ended up penciling in a system of additional propellant shipments sent to Mars orbit via a long SEP trip.

http://forum.nasaspaceflight.com/index.php?topic=37808.msg1589654#msg1589654

In that analysis, the LOX tank sidewall comes in at 34mm, the CH4 tank & hab sidewall 7.5mm.  Tank skin mass for the interplanetary stage alone is  ~46 tons, hab skin mass is ~8 tons. This is not counting ribs, trusses, heatshields, vacuum insulation, vacuum flask, plumbing, engines, anything.  There's some mild sandbagging in there (in a pessimistic assumed tensile strength for aluminum) to add a margin of error.

That looks remarkably prescient. But why did the LOX tanks end up nearly 5 times thicker? They are pressed to the same flight pressure and see lower dynamic loads.
Title: Re: ITS Development Updates and Discussion Thread
Post by: Chris Bergin on 02/27/2017 05:06 pm
I'll ask around.

Got any answers?

Inconclusive. Some say it was the point of the test. Some say it was a tragic early death of a test tank. Need an official answer on the test.
Title: Re: ITS Development Updates and Discussion Thread
Post by: Burninate on 02/28/2017 05:56 pm
So if all-composite tanks don't pan out (at least for O2 tanks), what kind of weight increase are we talking about?

Depends how thick the Invar liner needs to be and whether they can use its strength to reduce the weight of the composite.

If it's 1 mm thick over the area of the ship's LOX tank, that only adds about 3 tonnes.

I spent most of a year iterating my way through a projected MCT built of aluminum and moderate-pressure engines.  The case for Mars missions does close, but a few things, like 1-synod reuse, get very difficult.  I also ended up penciling in a system of additional propellant shipments sent to Mars orbit via a long SEP trip.

http://forum.nasaspaceflight.com/index.php?topic=37808.msg1589654#msg1589654

In that analysis, the LOX tank sidewall comes in at 34mm, the CH4 tank & hab sidewall 7.5mm.  Tank skin mass for the interplanetary stage alone is  ~46 tons, hab skin mass is ~8 tons. This is not counting ribs, trusses, heatshields, vacuum insulation, vacuum flask, plumbing, engines, anything.  There's some mild sandbagging in there (in a pessimistic assumed tensile strength for aluminum) to add a margin of error.

That looks remarkably prescient. But why did the LOX tanks end up nearly 5 times thicker? They are pressed to the same flight pressure and see lower dynamic loads.
The LOX tanks end up much higher pressure than the CH4 tanks, because LOX boils at a much lower temperature than CH4, and the partial pressure of LOX is higher at the same temperature than the partial pressure of CH4.  A common thermal environment was assumed from the start;  Thermally insulating the CH4 tank from the LOX tank would presumably involve a large amount of extra mass, and maintaining a temperature differential actively...
Title: Re: ITS Development Updates and Discussion Thread
Post by: rsdavis9 on 02/28/2017 07:19 pm
Without calculating it. It doesn't seem more pressure vs insulation is a good trade off for weight. Insulation can be extremely light.
Title: Re: ITS Development Updates and Discussion Thread
Post by: acsawdey on 02/28/2017 07:24 pm
Without calculating it. It doesn't seem more pressure vs insulation is a good trade off for weight. Insulation can be extremely light.

I suspect it isn't so much insulation as the fact that if you want any insulation you need a "between" to put it in, hence you can't have common bulkhead between the tanks. Once you have separate bulkheads then yes multilayer insulation in vacuum won't add much weight at all.
Title: Re: ITS Development Updates and Discussion Thread
Post by: meekGee on 02/28/2017 09:52 pm
Without calculating it. It doesn't seem more pressure vs insulation is a good trade off for weight. Insulation can be extremely light.

I suspect it isn't so much insulation as the fact that if you want any insulation you need a "between" to put it in, hence you can't have common bulkhead between the tanks. Once you have separate bulkheads then yes multilayer insulation in vacuum won't add much weight at all.

Why can't you have non-structural insulation behind a liner at the top of the LOX tank?
Title: Re: ITS Development Updates and Discussion Thread
Post by: envy887 on 03/01/2017 10:51 pm
The vehicle needs active and passive thermal management, both are required for flying people and cryogenic fuels on the same vehicle.

If the vehicle flies with engines pointed at the sun for thermal management, then the CH4 tank will likely be warmer than the LOX tank because it's closer to the engines.

I think that the sidewall area is large enough for radiative cooling to keep both the LOX and CH4 below boiling - or at least limit the thermal energy transfer to a very small amount of boiloff which can be recycled by a small refrigeration system.
Title: Re: ITS Development Updates and Discussion Thread
Post by: Burninate on 03/07/2017 05:15 pm
The vehicle needs active and passive thermal management, both are required for flying people and cryogenic fuels on the same vehicle.

If the vehicle flies with engines pointed at the sun for thermal management, then the CH4 tank will likely be warmer than the LOX tank because it's closer to the engines.

I think that the sidewall area is large enough for radiative cooling to keep both the LOX and CH4 below boiling - or at least limit the thermal energy transfer to a very small amount of boiloff which can be recycled by a small refrigeration system.

Right.  But what is "active and passive thermal management" precisely?

You also don't get to count on position relative to the Sun, necessarily, because you don't get control over that on Mars.
Title: Re: ITS Development Updates and Discussion Thread
Post by: Semmel on 03/10/2017 11:12 am
Not entirely on topi but also not entirely off as well. I want to share a story with you.

First the off-topic part:
Some of my colleges were on a workshop about cryogenic vacuum systems the last days. The workshop was for detector systems operated at cryogenic temperature but most of the stuff they told me applies to all kinds of vacuum systems, cryogenics or not.
For example, if a device contains a ball bearing, the vacuum would evaporate the lubricant, which would lead to a failure of the ball bearing, not to mention a contamination of the vacuum. What you have to do is to (and I kid you not) coat the ball bearing halves with gold and replace the balls with rubies. Gold because it is soft and self-lubricating and rubies because they conduct heat pretty well so that a large temperature differential between the ball bearing halves is prevented. As someone without experience in vacuum systems, stuff like that is utterly unexpected and unpredictable.

Now the on-topic part:
SpaceX will operate its ITS and many Mars-surface machinery in near vacuum. Many of them also in cryogenic environments due to the fuel cooling. After hearing the story above, I realize that there is a whole zoo of knowledge regarding vacuum systems that SpaceX needs to develop and get experience with before they can send their ITS ship to Mars. They dont want to have it fall apart half way to Mars because they overlooked some stuff unique to vacuum systems. Of course, they are professionals and probably have many people with lots of experience in vacuum systems. But still, its some task and knowledge base that I completely underestimated so far. Do they have large vacuum testing and development facilities? I find this quite fascinating to be honest. The ISS Canadarm team must have tons of experience with stuff like that..

PS: please dont see this as concern trolling. Its not, I am generally fascinated by the difficulties concerning vacuum system. Really unexpected!
Title: Re: ITS Development Updates and Discussion Thread
Post by: Rei on 03/10/2017 12:11 pm
Vacuum compatibility of materials is not a secret  :) There's a nice database you can search over here:

http://outgassing.nasa.gov/

I have a lot of hope for ionic liquids in the future (they remain liquid without relevant outgassing even at zero air pressure).  Currently very expensive, but prices are dropping; there's nothing that *fundamentally* renders them expensive, it's just finding good organic synthesis route and getting enough of a market established for bulk production.  They're particularly promising for Venus ISRU; if you do water scrubbing you have to get all of the water vapour back out of the air (if atmospheric constituents ar reaching equilibrium with your water than your water is reaching equilibrium with the atmosphere), but if you scrub with ionic liquids (which are almost universal solvents, you can tune them in endless ways), nothing evaporates to the air stream.
Title: Re: ITS Development Updates and Discussion Thread
Post by: M.E.T. on 03/10/2017 12:41 pm
Just for clarification, in the SpaceX ITS presentation they showed the same ITS booster landing in the cradle and repeatedly taking off in quick succession to fuel the ITS spaceship in orbit. Was that just done to illustrate the refuelling concept, or is the intention truly to have the exact same booster land and take off again with as little as a day turnaround time 5 times in a row?

I fully understand the concept of getting maximum reuse out of the same booster in order to bring the average cost per use down as much as possible, but surely the risk of some malfunction caused by one of the repeated launches and atmospheric re-entries could scupper the entire mission?

Are we realistically perhaps rather looking at 5 separate boosters, each taking off one after another to refuel the spacecraft, and then those 5 boosters getting reused for each new ITS launch? But getting refurbished in-between launches?

Then you are still looking at full reuse, but you have a group of 5 boosters per upper stage, used to launch and fuel it for each Mars trip. And these 5 get reused the next month again, for the next ITS launch, etc.

Surely relying on just ONE booster to repeatedly launch and land at a daily cadence is a somewhat unrealistic goal to aim at or what?
Title: Re: ITS Development Updates and Discussion Thread
Post by: spacenut on 03/10/2017 01:00 pm
Maybe ITS is too big and needs to be scaled down, like some people have said, to say 50 passengers or 50 tons to Mars instead of 100 passengers or 100 tons of cargo.  Yes it will take longer, but scaling down, and developing a large in space SEP tug, much of the cargo can be transported like a "slow boat to China".  Then smaller launchers like FH could launch fuel to a fuel depot weekly or monthly, and build a huge depot.  Multiple ITS can launch, refuel at the depot and go to Mars during the Synod. 

Again, a smaller BFR to launch fuel to a depot, then a 3 core heavy version to launch ITS.  I know this isn't what they are doing, but a single stick BFR can do double duty to the Moon and and refueling a depot.   I would opt for a 9 Raptor engine BFR with a 27 engine Heavy.  Maybe even an 18 engine BFR to use the existing Pad 39A facilities.  Just MHO. 

After all the tests and studies are done, and after Raptor gets a full blown test for both sea level and vacuum versions, they may scale down their Mars vehicle and make it more robust.   Even then with a scaled down ITS, a very large in space transport system could be built like NautilusX, but larger, to ferry between earth and Mars all the time, using ITS to launch components for a transporter for ITS.  Again, that could be continuously refueled for use between synods. 
Title: Re: ITS Development Updates and Discussion Thread
Post by: spacenut on 03/10/2017 01:09 pm
Oh, even with the huge ITS requiring 5 ITS launchings for refueling to go to Mars, this still makes sense to build a huge fuel depot shaded by solar panels.  Multiple launches for the fuel depot can be done in the 18 month time frame.  Even one a month could refuel 3 ITS for them to refuel going to MARS during the 6 month synod.  So Three BFRS for 3 to go to MAR with three BFRS each launching 5-6 times to the depot, could be doable with only 3 ships built.  Over time and as more are built, the fuel depot expanded or have two depots over time for redundancy. 
Title: Re: ITS Development Updates and Discussion Thread
Post by: RonM on 03/10/2017 01:23 pm
Just for clarification, in the SpaceX ITS presentation they showed the same ITS booster landing in the cradle and repeatedly taking off in quick succession to fuel the ITS spaceship in orbit. Was that just done to illustrate the refuelling concept, or is the intention truly to have the exact same booster land and take off again with as little as a day turnaround time 5 times in a row?

I fully understand the concept of getting maximum reuse out of the same booster in order to bring the average cost per use down as much as possible, but surely the risk of some malfunction caused by one of the repeated launches and atmospheric re-entries could scupper the entire mission?

Are we realistically perhaps rather looking at 5 separate boosters, each taking off one after another to refuel the spacecraft, and then those 5 boosters getting reused for each new ITS launch? But getting refurbished in-between launches?

Then you are still looking at full reuse, but you have a group of 5 boosters per upper stage, used to launch and fuel it for each Mars trip. And these 5 get reused the next month again, for the next ITS launch, etc.

Surely relying on just ONE booster to repeatedly launch and land at a daily cadence is a somewhat unrealistic goal to aim at or what?

ITS is landing back at the launch pad for rapid reuse. If SpaceX was going to use different boosters they would have the boosters land somewhere else while another booster was being moved to the pad.
Title: Re: ITS Development Updates and Discussion Thread
Post by: meekGee on 03/10/2017 01:55 pm
Not entirely on topi but also not entirely off as well. I want to share a story with you.

First the off-topic part:
Some of my colleges were on a workshop about cryogenic vacuum systems the last days. The workshop was for detector systems operated at cryogenic temperature but most of the stuff they told me applies to all kinds of vacuum systems, cryogenics or not.
For example, if a device contains a ball bearing, the vacuum would evaporate the lubricant, which would lead to a failure of the ball bearing, not to mention a contamination of the vacuum. What you have to do is to (and I kid you not) coat the ball bearing halves with gold and replace the balls with rubies. Gold because it is soft and self-lubricating and rubies because they conduct heat pretty well so that a large temperature differential between the ball bearing halves is prevented. As someone without experience in vacuum systems, stuff like that is utterly unexpected and unpredictable.

Now the on-topic part:
SpaceX will operate its ITS and many Mars-surface machinery in near vacuum. Many of them also in cryogenic environments due to the fuel cooling. After hearing the story above, I realize that there is a whole zoo of knowledge regarding vacuum systems that SpaceX needs to develop and get experience with before they can send their ITS ship to Mars. They dont want to have it fall apart half way to Mars because they overlooked some stuff unique to vacuum systems. Of course, they are professionals and probably have many people with lots of experience in vacuum systems. But still, its some task and knowledge base that I completely underestimated so far. Do they have large vacuum testing and development facilities? I find this quite fascinating to be honest. The ISS Canadarm team must have tons of experience with stuff like that..

PS: please dont see this as concern trolling. Its not, I am generally fascinated by the difficulties concerning vacuum system. Really unexpected!
:) as folks have said, vacuum compatibility is well known, for example to people designing robotic systems that work in vacuum for the semiconductor industry.

Actually, though, those are "very high vacuum" systems, and the vacuum is higher than that found in space near near a satellite.

The Mars environment, happily, is not even considered low grade vacuum. There's enough atmosphere to prevent cold welding, to keep many lubricants working, to convect...  And, you don't worry about molecular contamination.

This is one of the many reasons Mars colonization is  easier than moon and asteroids. Designing for full vacuum, while understood, is very difficult, and requires a lot of trade offs.
Title: Re: ITS Development Updates and Discussion Thread
Post by: Nathan2go on 03/20/2017 03:49 am
Maybe ITS is too big and needs to be scaled down, like some people have said, to say 50 passengers or 50 tons to Mars instead of 100 passengers or 100 tons of cargo.  ...

That depends on the business/funding source that drives it.  Say NASA wants a commercial launch vehicle to complement the SLS:  SLS can put 130 tons in LEO, or send around 55 tons to the Moon & 45 tons to Mars.  Maybe they would want an alternate source with exactly the same BEO capacity.  For methane-O2, that's about 160 tons to LEO.

Maybe NASA would really like a commercial Earth departure stage that can dock on orbit with 130 ton SLS payloads, and send them to Mars, with no propellant transfer required.  That departure stage would mass around 250 tons in LEO for methane-O2 (182 tons for LH2-O2).

Better yet, it's less threatening to SLS if NASA would to buy LOX from an orbiting tanker to re-fuel an SLS stage (i.e. to replace the nuclear-thermal stage shown in NASA last Mars Design Reference Mission, DRM5).  They'd need about 120 tons to supply a stretched SLS upper stage which arrived with 100 tons of payload and 20 tons of LH2.

Of course SpaceX could offer NASA any of the above services using multiple launches of a smaller rocket, but then there is the added risk of extra on-orbit docking and/or propellant transfers.  Given their history, NASA will want both O2 and LH2 from a depot, so the depot will have even more development required.  Instead, having NASA pay for the development of BFR/ITS would be a better next step.  After the rocket is built, depots can be developed later, and maybe private industry can fund some Mars flights and base building.

Again, a smaller BFR to launch fuel to a depot, then a 3 core heavy version to launch ITS.  I know this isn't what they are doing, but a single stick BFR can do double duty to the Moon and refueling a depot.
With economies of scale, the 3-core heavy version is also a cheaper way to supply the depot (one-big launch is cheaper than 3 little ones).  So the main reason to build a smaller rocket is that you think there is a good sized market for payloads that size.  Remember that the Saturn V (130 tons to LEO) was only barely large enough for Lunar missions (for two person crews).

I think the 300 ton LEO size of ITS is a good choice for base building, but 120-250 tons would compliment SLS better.   I agree that it makes sense to start with a small mission mass and build up.  However, rather than making the rocket much smaller, I think it makes sense to post-pone on-orbit refueling and Mars lander re-use.  Just build a 100 ton capsule-style expendable lander which can be thrown to Mars by a single launch of an ITS (re-usable first stage and expendable 2nd stage, like F9).  Such a capsule would only really have 50 tons of useful payload, but it would be shorter, thus easier to unload on Mars.  Use a dozen or so of those landers to build up the base before starting flights with 300 ton re-usable ITS landers. 

A Mars program that starts with 2-3 flight per year each for SLS and ITS, will be more politically acceptable than one with many more flights for SpaceX and no role for SLS.
Title: Re: ITS Development Updates and Discussion Thread
Post by: Rei on 03/20/2017 07:36 am
The Mars environment, happily, is not even considered low grade vacuum. There's enough atmosphere to prevent cold welding, to keep many lubricants working, to convect...  And, you don't worry about molecular contamination.

This is one of the many reasons Mars colonization is  easier than moon and asteroids. Designing for full vacuum, while understood, is very difficult, and requires a lot of trade offs.

What lubricants which can't tolerate a hard vacuum do well at ~600 Pa?  Curiosity, for example, uses Castrol Braycote 601 EF, which is also used on ISS (hard vacuum tolerant).

Also, I'm not following the logic, because whatever you send to Mars has to spend a long time in hard vacuum in-transit. Unless you send it as pressurized cargo, which comes at a significant mass penalty.
Title: Re: ITS Development Updates and Discussion Thread
Post by: meekGee on 03/20/2017 10:01 am
The Mars environment, happily, is not even considered low grade vacuum. There's enough atmosphere to prevent cold welding, to keep many lubricants working, to convect...  And, you don't worry about molecular contamination.

This is one of the many reasons Mars colonization is  easier than moon and asteroids. Designing for full vacuum, while understood, is very difficult, and requires a lot of trade offs.

What lubricants which can't tolerate a hard vacuum do well at ~600 Pa?  Curiosity, for example, uses Castrol Braycote 601 EF, which is also used on ISS (hard vacuum tolerant).

Also, I'm not following the logic, because whatever you send to Mars has to spend a long time in hard vacuum in-transit. Unless you send it as pressurized cargo, which comes at a significant mass penalty.

In hard vacuum, surfaces lack the normal monolayer(s)  of volatiles, which are sometimes referred to as "lubrication" and which cause materials to behave in "normal" ways.

So when considering hard-vacuum robotics (as you do in semicon applications), things become more difficult.

You can say that "they are well understood", but with the crazy amount of engineering that will have to happen for Mars equipment, it's a problem.

Vacuum lubricants exist, but you don't want to lubricate every two surfaces that may come together, or every surface that might degrade in hard vacuum.

These phenomena don't happen at 600 PA.

For this reason, you'd want to keep the cargo bay at Mars pressure and temperature range. (Which by BFSs design is very easy)
Title: Re: ITS Development Updates and Discussion Thread
Post by: su27k on 03/31/2017 04:42 pm
From robbak's transcript of SES-10 post launch press conference (https://www.reddit.com/r/spacex/comments/62i6m1/recap_of_the_elon_musk_and_martin_halliwell_press/dfnbo83/), "E" is Elon:

Quote
Robinson Manuel , with the New York Observer, Could you give us an update on the development of the Interplanetary Transport System, and what's next in terms of - what's the nex component to be tested following the carbon fuel tank and the Raptor engine?

E: I think we'll provide an update on the design of the Interplanetary Transport System - Interplanetary Transport System also includes the propellant depot on Mars - that's why it's sort of - I actually usually don't like the word 'system', but we can't call it a rocket if it includes a propellant depot. So the Mars planetery transporter or Mars Transporter, ir Interplanetary Transporter - We've come up with a number of desibn refinements, and I hope I'll be ready ot put that on the Website withing a month or so.

RM: Just want a follow-up The timeframe has shifted since Gh, I was wondering if if yuo guys had any updated timeframe of when you think that firstmission will be launched - If I'm correct, the first one is uncrewed amd I right

E: Yes the first one will be uncrewed, I don't want to steal thunder from that announcement. I'm pretty excited about the upgrades strategy since Gh, it makes a lot more sense, it's - we have to not just get it done technically, but figure out how to get this done without going bankrupt. So it's like, our goal is to get people on Mars before we're dead, and the company is dead. So like, either one of that. Ideally, the first. We don't want to take so long that dead by when that happens, and we don't want to kill the company in the process. So we have to figure out not just solve the technical issues, but the economic issues. I think the new approach is going to be able to do that. Hopefully.

Can't wait to see how they address the economic issues, let the speculation begin...
Title: Re: ITS Development Updates and Discussion Thread
Post by: Kansan52 on 03/31/2017 05:00 pm
"Ideally, the first. We don't want to take so long that dead by when that happens, and we don't want to kill the company in the process."

I find comfort in this statement. There are plans for SX to continue after Mars Elon. No pyrrhic victory planned.
Title: Re: ITS Development Updates and Discussion Thread
Post by: M.E.T. on 04/01/2017 06:57 am
From robbak's transcript of SES-10 post launch press conference (https://www.reddit.com/r/spacex/comments/62i6m1/recap_of_the_elon_musk_and_martin_halliwell_press/dfnbo83/), "E" is Elon:

Quote
Robinson Manuel , with the New York Observer, Could you give us an update on the development of the Interplanetary Transport System, and what's next in terms of - what's the nex component to be tested following the carbon fuel tank and the Raptor engine?

E: I think we'll provide an update on the design of the Interplanetary Transport System - Interplanetary Transport System also includes the propellant depot on Mars - that's why it's sort of - I actually usually don't like the word 'system', but we can't call it a rocket if it includes a propellant depot. So the Mars planetery transporter or Mars Transporter, ir Interplanetary Transporter - We've come up with a number of desibn refinements, and I hope I'll be ready ot put that on the Website withing a month or so.

RM: Just want a follow-up The timeframe has shifted since Gh, I was wondering if if yuo guys had any updated timeframe of when you think that firstmission will be launched - If I'm correct, the first one is uncrewed amd I right

E: Yes the first one will be uncrewed, I don't want to steal thunder from that announcement. I'm pretty excited about the upgrades strategy since Gh, it makes a lot more sense, it's - we have to not just get it done technically, but figure out how to get this done without going bankrupt. So it's like, our goal is to get people on Mars before we're dead, and the company is dead. So like, either one of that. Ideally, the first. We don't want to take so long that dead by when that happens, and we don't want to kill the company in the process. So we have to figure out not just solve the technical issues, but the economic issues. I think the new approach is going to be able to do that. Hopefully.

Can't wait to see how they address the economic issues, let the speculation begin...

Elon's statement seems to hint at a shift of the timeline to the right, allowing for the development costs to be spread over a longer period of time - probably so that the satellite network can start generating the necessary cash to fund the ITS program.

So might we see something like a 5 year delay on the original milestone dates?
Title: Re: ITS Development Updates and Discussion Thread
Post by: The Amazing Catstronaut on 04/01/2017 08:24 am
Why? There doesn't appear to be any evidence supporting the idea of a delay. Certainly, delays will occur, but Elon seems to set the goalposts to the right when technical issues occur, rather than economic.

Having a plan doesn't mean 'giving it more time' by inference. Indeed, it infers the opposite, because they now have a working methodology.

Sure, I believe delays will happen to the most ambitious, largest, longest ranged manned flying object ever to be created by humanity, but they'll come later down the pipeline.

And damn, considering everything going on nowadays, why on earth haven't I renewed my L2?
Title: Re: ITS Development Updates and Discussion Thread
Post by: docmordrid on 04/01/2017 08:46 am
One question is; did the original financial concept include updated projected revenues from CommX?, which a few months ago WSJ estimated to be extremely lucrative. What's the SpaceX/Google split? Etc.
Title: Re: ITS Development Updates and Discussion Thread
Post by: M.E.T. on 04/01/2017 09:31 am
Why? There doesn't appear to be any evidence supporting the idea of a delay. Certainly, delays will occur, but Elon seems to set the goalposts to the right when technical issues occur, rather than economic.

Having a plan doesn't mean 'giving it more time' by inference. Indeed, it infers the opposite, because they now have a working methodology.

Sure, I believe delays will happen to the most ambitious, largest, longest ranged manned flying object ever to be created by humanity, but they'll come later down the pipeline.

And damn, considering everything going on nowadays, why on earth haven't I renewed my L2?

Well, Elon's latest statement seemed to provide the two extremes of the timeframe for putting humans on Mars.

The factor influencing the lower limit is that they cannot invest so much money in it that it bankrupts the company. In other words, they have to match the investments in ITS with the cash inflows they receive from elsewhere.

The factor influencing the upper limit of the timeframe is that he wants to still be alive when humans land on Mars. Hence, they cannot reduce the investment in ITS so much that it takes decades to develop.

Therefore, a potential interpretation of his comments is that they have had to become more realistic in their timeline, but that they now feel they have a plan that can reasonably be achieved with the revenue streams they can expect over the timeperiod in question.

Without the satellite network revenue stream, that might have been a decade or more. But, with that source of revenue built in, it might just be a case of waiting for some of those inflows to fund ITS completion.

Hence my guess at maybe a 5 year delay. So let's say 2026 for first Mars flight by ITS, but with some Falcon Heavy flights every launch window before then?
Title: Re: ITS Development Updates and Discussion Thread
Post by: The Amazing Catstronaut on 04/01/2017 01:10 pm
That makes sense, but there will be a continuous revenue ramp-up over that period. You then have to factor additional contract money, flightrate increase, and less development time being spend on the core architecture of FH, and less money being spend on the development of F9 focused infrastructure once they've to the endgame operations for F9 together. They will be able to focus their efforts.

As manpower, technical capability and mission confidence increases, organisational efficiency, if correctly projected, can also increase, rather than decreasing, within the system SpaceX has constructed. Vast swathes of ITS development cost will be axed by the integration of data from the (essential) precursor systems that are feeding into the holistic  development of ITS. This is how they've always developed hardware, and it's enabled them to make comparable jumps.

I'd make a case that F1 to final dev F9 is a comparable jump from F9 to ITS. However, you have lots of sub-steps occurring concurrently which lower the length of the leap - most critically, sub-steps that create revenue. Dragon, F9 and FH are all essential precursor systems which they are earning revenue off. Raptor, whilst being an in-house development, has already earned them external funds and has the potential to earn them considerably more. SpaceX is remarkably good at finding ways to integrate their RnD with profiteering to a point where losses are not only sustainable but recoupable. This counts for time loss as much as it does financial investment.

As for the satellites, they're quietly coming together, furiously. I'm not surprised SpaceX is quiet about them considering the nature of the market and the amount of paperchasing that needs to coincide with hard hardware. I'm very much confident that ITS will come together - and whilst a five year delay is entirely reasonable, I believe finance won't stop test articles (there's already that tank existence), or perhaps even the development of the first ITS itself.
Title: Re: ITS Development Updates and Discussion Thread
Post by: AlexP on 04/01/2017 01:23 pm
I'd assumed a delay myself after first hearing his press conference response, but I'm unsure why he'd be "pretty excited" about this change in strategy. Of course, it's very difficult in general to read correctly into these short replies he gives.
Title: Re: ITS Development Updates and Discussion Thread
Post by: Robotbeat on 04/01/2017 01:27 pm
Why? There doesn't appear to be any evidence supporting the idea of a delay. Certainly, delays will occur, but Elon seems to set the goalposts to the right when technical issues occur, rather than economic.

Having a plan doesn't mean 'giving it more time' by inference. Indeed, it infers the opposite, because they now have a working methodology.

Sure, I believe delays will happen to the most ambitious, largest, longest ranged manned flying object ever to be created by humanity, but they'll come later down the pipeline.

And damn, considering everything going on nowadays, why on earth haven't I renewed my L2?
I bet the plan to make it more economically viable is to use ITS, or at least part of it, for Constellation launch. There are many ways I could see it reducing Constellation launch costs, such as an integrated and recovered deployer/upper stage as another modified version of BFS.

Also, running Raptor initially at lower thrust and/or with fewer engines would make it a LOT easier to find a suitable launch site and should make it cheaper and easier for SpaceX to get to first flight while making a good upgrade path as performance improves, much like Falcon 9 doubled in performance.
Title: Re: ITS Development Updates and Discussion Thread
Post by: M.E.T. on 04/01/2017 01:37 pm
Why? There doesn't appear to be any evidence supporting the idea of a delay. Certainly, delays will occur, but Elon seems to set the goalposts to the right when technical issues occur, rather than economic.

Having a plan doesn't mean 'giving it more time' by inference. Indeed, it infers the opposite, because they now have a working methodology.

Sure, I believe delays will happen to the most ambitious, largest, longest ranged manned flying object ever to be created by humanity, but they'll come later down the pipeline.

And damn, considering everything going on nowadays, why on earth haven't I renewed my L2?
I bet the plan to make it more economically viable is to use ITS, or at least part of it, for Constellation launch. There are many ways I could see it reducing Constellation launch costs, such as an integrated and recovered deployer/upper stage as another modified version of BFS.

Also, running Raptor initially at lower thrust and/or with fewer engines would make it a LOT easier to find a suitable launch site and should make it cheaper and easier for SpaceX to get to first flight while making a good upgrade path as performance improves, much like Falcon 9 doubled in performance.

Could we be looking at a dawning realization that Falcon Heavy - due to some of the "crazy difficult" aspects Elon alluded to - might be less feasible than initially thouht, and therefore might we see an earlier shift to the ITS first stage as a near term replacement for Falcon Heavy?

Allowing both progress on the ITS development path and more competitive launch capabilities for non-Mars related heavy payloads to orbit?

Basically, a speeding up of the ITS first stage for general use, while the dedicated Mars upper stage is pushed out by a few years?
Title: Re: ITS Development Updates and Discussion Thread
Post by: Robotbeat on 04/01/2017 01:44 pm
Yeah, I've thought for a while that Falcon Heavy could soon be replaced. 27 engines is a lot. 3 cores is even worse. If SpaceX could make a version of ITS to replace Falcon Heavy, I think it'd cement their lead in launch technology and cost at the high end.

ITS' concept of operations is, in principle, much less manpower/ma'ampower intensive than Falcon Heavy especially for constellation flights.
Title: Re: ITS Development Updates and Discussion Thread
Post by: tdperk on 04/01/2017 04:03 pm
I'll ask around.

Got any answers?

Inconclusive. Some say it was the point of the test. Some say it was a tragic early death of a test tank. Need an official answer on the test.

I'm very interested in that, and have seen nothing on it.
Title: Re: ITS Development Updates and Discussion Thread
Post by: RonM on 04/01/2017 04:47 pm
Yeah, I've thought for a while that Falcon Heavy could soon be replaced. 27 engines is a lot. 3 cores is even worse. If SpaceX could make a version of ITS to replace Falcon Heavy, I think it'd cement their lead in launch technology and cost at the high end.

ITS' concept of operations is, in principle, much less manpower/ma'ampower intensive than Falcon Heavy especially for constellation flights.

I don't think the number of engines is an issue, ITS booster will have even more engines. Three cores have been done before, but it's probably turning out to be too expensive an option.
Title: Re: ITS Development Updates and Discussion Thread
Post by: Kaputnik on 04/01/2017 04:52 pm
Yeah, I've thought for a while that Falcon Heavy could soon be replaced. 27 engines is a lot. 3 cores is even worse. If SpaceX could make a version of ITS to replace Falcon Heavy, I think it'd cement their lead in launch technology and cost at the high end.

ITS' concept of operations is, in principle, much less manpower/ma'ampower intensive than Falcon Heavy especially for constellation flights.

I don't think the number of engines is an issue, ITS booster will have even more engines. Three cores have been done before, but it's probably turning out to be too expensive an option.


What if ITS turns out to be 'way more difficult than we thought'...?
Title: Re: ITS Development Updates and Discussion Thread
Post by: RonM on 04/01/2017 05:01 pm
Yeah, I've thought for a while that Falcon Heavy could soon be replaced. 27 engines is a lot. 3 cores is even worse. If SpaceX could make a version of ITS to replace Falcon Heavy, I think it'd cement their lead in launch technology and cost at the high end.

ITS' concept of operations is, in principle, much less manpower/ma'ampower intensive than Falcon Heavy especially for constellation flights.

I don't think the number of engines is an issue, ITS booster will have even more engines. Three cores have been done before, but it's probably turning out to be too expensive an option.


What if ITS turns out to be 'way more difficult than we thought'...?

Then it's "Hawthorne, we have a problem."

While I and many others have confidence in SpaceX, we need to be realistic and admit that building ITS is going to be difficult and SpaceX might not succeed.
Title: Re: ITS Development Updates and Discussion Thread
Post by: butters on 04/01/2017 05:37 pm
ITS schedule may also depend on to what extent, if any, the federal government winds up supporting the project via NASA. The Kremlinology (please excuse the unavoidable pun) surrounding the manned EM-1 proposal and Elon's circumlunar mission announcement does not bode well for government funding of SpaceX BEO projects at this time.
Title: Re: ITS Development Updates and Discussion Thread
Post by: Robotbeat on 04/01/2017 06:07 pm
Yeah, I've thought for a while that Falcon Heavy could soon be replaced. 27 engines is a lot. 3 cores is even worse. If SpaceX could make a version of ITS to replace Falcon Heavy, I think it'd cement their lead in launch technology and cost at the high end.

ITS' concept of operations is, in principle, much less manpower/ma'ampower intensive than Falcon Heavy especially for constellation flights.

I don't think the number of engines is an issue, ITS booster will have even more engines. Three cores have been done before, but it's probably turning out to be too expensive an option.
I think it's number of engines combined with number of cores that makes Falcon Heavy especially hard. It was supposed to be just an easy adaption of Falcon 9, but reality is different.

Single stick makes some things easier, although you do need a big clean sheet design.
Title: Re: ITS Development Updates and Discussion Thread
Post by: philw1776 on 04/01/2017 07:01 pm
No reason the "Real" ITS booster and maybe the upper stage can't initially be flown even with the desired ariframe but using less Raptors and of course deliveing fewer hundred tonnes to LEO per reuseable shot.  Less "efficient" but Musk values velocity of innovation over the ultimate pure final configuration, e.g. F9 Block 5, years after "imperfect" F9s with interim rev Merlins flying and generating revenue.
Title: Re: ITS Development Updates and Discussion Thread
Post by: 2552 on 04/02/2017 07:55 am
I wonder if the ITS booster could do a downrange landing on a ship using strakes instead of a reentry burn like New Glenn. With no boostback or reentry burn, the payload should be at least 50% more than with RTLS (given 300t reusable payload and 550t expendable payload), which would mean Mars trips would need 1, maybe 2 less tanker flights, and the ITS spaceship could launch with a full 450 ton cargo load without needing to do in-space cargo transfer. I also wonder if the landing cradle guide fins could be shaped to act as the strakes themselves, so you wouldn't need separate ones. Although, landing in a cradle on a ship would be harder than on land, and landing on a moving ship for stability could be even harder since it would need to do a precision landing in the cradle instead of just landing anywhere on deck.
Title: Re: ITS Development Updates and Discussion Thread
Post by: rsdavis9 on 04/02/2017 01:13 pm
How about DoD thinks being able to land 100 marines anywhere on earth in 45 mins is a strategic capability that they want to pay for.

What was the number for ITS dev? 10bn?

I really don't like the idea of the military being the "owner" of this technology but that is one place where there is very deep pockets.
Title: Re: ITS Development Updates and Discussion Thread
Post by: guckyfan on 04/02/2017 01:18 pm
I wonder if the ITS booster could do a downrange landing on a ship using strakes instead of a reentry burn like New Glenn. With no boostback or reentry burn, the payload should be at least 50% more than with RTLS (given 300t reusable payload and 550t expendable payload), which would mean Mars trips would need 1, maybe 2 less tanker flights, a

Elon Musk said in his presentation that with the very good mass fraction and higher ISP Raptor engines the payload penalty is much smaller for BFR/ITS than for the Falcon family. They really want RTLS for fast turnaround, not operating an ASDS ISDS out there.
Title: Re: ITS Development Updates and Discussion Thread
Post by: su27k on 04/02/2017 03:31 pm
How about DoD thinks being able to land 100 marines anywhere on earth in 45 mins is a strategic capability that they want to pay for.

Many problems with this idea, for example without refueling at destination you couldn't get the Ship back. Also SpaceX is not going to disclose a DoD application on their website. One possibility is civilian sub-orbital point to point transport, but it seems more trouble than its worth, just thinking about the FAA certification it will need makes my head hurt.

If I had to guess, assuming they keep the 12m diameter, I think the big change would be getting rid of the big booster. It's needed to get the super low colonist price, but not necessary for initial expedition to Mars. The booster is too big, it scares people and makes them not taking ITS seriously (x times the thrust of Saturn V, sound effect, blast radius, blah blah, can't believe how many times I read these from ITS critics). To get the Ship to orbit, either they'll do SSTO, or they'll use a smaller booster, maybe based on the Ship structure to streamline manufacturing.
Title: Re: ITS Development Updates and Discussion Thread
Post by: philw1776 on 04/02/2017 06:48 pm
How about DoD thinks being able to land 100 marines anywhere on earth in 45 mins is a strategic capability that they want to pay for.

Many problems with this idea, for example without refueling at destination you couldn't get the Ship back. Also SpaceX is not going to disclose a DoD application on their website. One possibility is civilian sub-orbital point to point transport, but it seems more trouble than its worth, just thinking about the FAA certification it will need makes my head hurt.

If I had to guess, assuming they keep the 12m diameter, I think the big change would be getting rid of the big booster. It's needed to get the super low colonist price, but not necessary for initial expedition to Mars. The booster is too big, it scares people and makes them not taking ITS seriously (x times the thrust of Saturn V, sound effect, blast radius, blah blah, can't believe how many times I read these from ITS critics). To get the Ship to orbit, either they'll do SSTO, or they'll use a smaller booster, maybe based on the Ship structure to streamline manufacturing.

Check out and fly ITS suborbital using all Raptor sea level engines.  RTLS.
Check out ITS orbital by launching with the booster but with just 24 Raptors and of course half the tons of booster propellant.
Ran the #s and this hack gets ITS to LEO plus with over 50 tons of payload.
Reduces the # of Raptors that need to be built & tested before the inevitable flurry of ECOs to make the engines and airframes more robust, more efficient, more economical.
Title: Re: ITS Development Updates and Discussion Thread
Post by: DJPledger on 04/02/2017 08:03 pm
From robbak's transcript of SES-10 post launch press conference (https://www.reddit.com/r/spacex/comments/62i6m1/recap_of_the_elon_musk_and_martin_halliwell_press/dfnbo83/), "E" is Elon:

Quote
Robinson Manuel , with the New York Observer, Could you give us an update on the development of the Interplanetary Transport System, and what's next in terms of - what's the nex component to be tested following the carbon fuel tank and the Raptor engine?

E: I think we'll provide an update on the design of the Interplanetary Transport System - Interplanetary Transport System also includes the propellant depot on Mars - that's why it's sort of - I actually usually don't like the word 'system', but we can't call it a rocket if it includes a propellant depot. So the Mars planetery transporter or Mars Transporter, ir Interplanetary Transporter - We've come up with a number of desibn refinements, and I hope I'll be ready ot put that on the Website withing a month or so.

RM: Just want a follow-up The timeframe has shifted since Gh, I was wondering if if yuo guys had any updated timeframe of when you think that firstmission will be launched - If I'm correct, the first one is uncrewed amd I right

E: Yes the first one will be uncrewed, I don't want to steal thunder from that announcement. I'm pretty excited about the upgrades strategy since Gh, it makes a lot more sense, it's - we have to not just get it done technically, but figure out how to get this done without going bankrupt. So it's like, our goal is to get people on Mars before we're dead, and the company is dead. So like, either one of that. Ideally, the first. We don't want to take so long that dead by when that happens, and we don't want to kill the company in the process. So we have to figure out not just solve the technical issues, but the economic issues. I think the new approach is going to be able to do that. Hopefully.

Can't wait to see how they address the economic issues, let the speculation begin...
Perhaps EM has realized that the ITS booster is too complex due to too many engines and that Raptor can be scaled up in size much more than originally thought. EM may have decided to redesign the ITS booster with fewer larger engines while keeping the original capability. Still have the original sized Raptor for the ITS ship.
Title: Re: ITS Development Updates and Discussion Thread
Post by: Robotbeat on 04/02/2017 09:37 pm
Or maybe same sized Raptor but fewer numbers at first with less initial payload. ITS is oversized by a factor of 5 or 10. So if initially the booster is a little smaller, it'd make almost no difference.
Title: Re: ITS Development Updates and Discussion Thread
Post by: cro-magnon gramps on 04/03/2017 01:19 am
OR!!!
he may have wanted to see what the "Brain Trust" {THINK TANK} at NSF had to say about it and just dropped a few ideas off the top of his head...  ;D :o

Ok just before I get moded, came up with a reasonable idea...

Perhaps Elon has taken his projections from 2016 and sat down with his economic team, and seen a way to make them work... but he has had to be realistic (accountants and spread sheets are notoriously unsympathetic to dreamers; I know, I'm always battling my budgets vs dreams :( ) and has had to amend his technical plans in some way... and it has excited him that he still gets to his goal - timeline, but in a more realistic technical way... as per the two examples above my post... I don't think he will lose time or move to the right much more than a synod or perhaps two...

Gramps

Ps, No, I don't think EM is that cagey, but it was a thought I just had, and speculation is the name of the game  ???

edit to make it mod proof :D
Title: Re: ITS Development Updates and Discussion Thread
Post by: 2552 on 04/03/2017 01:49 am
I wonder if the ITS booster could do a downrange landing on a ship using strakes instead of a reentry burn like New Glenn. With no boostback or reentry burn, the payload should be at least 50% more than with RTLS (given 300t reusable payload and 550t expendable payload), which would mean Mars trips would need 1, maybe 2 less tanker flights, a

Elon Musk said in his presentation that with the very good mass fraction and higher ISP Raptor engines the payload penalty is much smaller for BFR/ITS than for the Falcon family. They really want RTLS for fast turnaround, not operating an ASDS ISDS out there.

Yes, I was thinking they could use Elon's automatic refuel and relaunch from the ship/barge back to launch site idea to still have fast turnaround for the booster. I think it would probably be worth it for the payload increase, but there is the additional cost of the ship and its pad and operations and fuel for relaunch (1/4 to 1/3 of full booster prop load) + more cycles for the booster which increases lifecycle maintenance costs, so I could be wrong.
Title: Re: ITS Development Updates and Discussion Thread
Post by: Elmar Moelzer on 04/03/2017 05:27 am
I think their timeline was too optimistic, which is OK, IMHO. I also think that they need to do a lot of testing of their rocket before they fly people on it, which is why I still think that a SSTO version of the ITS would be an ideal way to gather a lot of experience with the thing quickly (not trying to derail the thread to the SSTO discussion again, which there are other threads for). Is it only me or did it feel like Musk was indicating other uses for the ITS (or LVs based on the basic architecture), once it came online. I mean during the SES 10 press conference, he talking about how the ITS would improve the cost for getting payloads to space a lot over the current architecture.
Title: Re: ITS Development Updates and Discussion Thread
Post by: Rei on 04/03/2017 08:18 am
I think their timeline was too optimistic, which is OK, IMHO. I also think that they need to do a lot of testing of their rocket before they fly people on it, which is why I still think that a SSTO version of the ITS would be an ideal way to gather a lot of experience with the thing quickly (not trying to derail the thread to the SSTO discussion again, which there are other threads for). Is it only me or did it feel like Musk was indicating other uses for the ITS (or LVs based on the basic architecture), once it came online. I mean during the SES 10 press conference, he talking about how the ITS would improve the cost for getting payloads to space a lot over the current architecture.

That was my take as well. Which would be suggestive that there would be a payload-only variant. Which logic would dictate would come first, as it's simpler and validates the system before man-rating it.

Which raises an interesting possibility. The second stage is much smaller and surely much cheaper than the first. They built a test article for the 2nd stage LOX tank as well, but as far as we know haven't made any test articles for the booster. The concept that they'll end up with a 2nd stage spaceship without a booster for it does not seem unrealistic at all.

Your concept is that they'd flight test it as a SSTO. But then it would have a terrible payload fraction. By contrast, if they made an interstage to mount it to a Falcon-based core, they could get a really massive payload, particularly to high orbits. And they'd get to keep using their existing Falcon infrastructure, while building up flight experience with the stage and working on the booster.
Title: Re: ITS Development Updates and Discussion Thread
Post by: M.E.T. on 04/03/2017 09:24 am
I think their timeline was too optimistic, which is OK, IMHO. I also think that they need to do a lot of testing of their rocket before they fly people on it, which is why I still think that a SSTO version of the ITS would be an ideal way to gather a lot of experience with the thing quickly (not trying to derail the thread to the SSTO discussion again, which there are other threads for). Is it only me or did it feel like Musk was indicating other uses for the ITS (or LVs based on the basic architecture), once it came online. I mean during the SES 10 press conference, he talking about how the ITS would improve the cost for getting payloads to space a lot over the current architecture.

That was my take as well. Which would be suggestive that there would be a payload-only variant. Which logic would dictate would come first, as it's simpler and validates the system before man-rating it.

Which raises an interesting possibility. The second stage is much smaller and surely much cheaper than the first. They built a test article for the 2nd stage LOX tank as well, but as far as we know haven't made any test articles for the booster. The concept that they'll end up with a 2nd stage spaceship without a booster for it does not seem unrealistic at all.

Your concept is that they'd flight test it as a SSTO. But then it would have a terrible payload fraction. By contrast, if they made an interstage to mount it to a Falcon-based core, they could get a really massive payload, particularly to high orbits. And they'd get to keep using their existing Falcon infrastructure, while building up flight experience with the stage and working on the booster.

Is it even feasible to put a 17 meter diameter second stage on a 3.6m diameter Falcon 9 booster? Sounds pretty lopsided to me. But then, I'm no expert.

Is the way to diversify the use of ITS not instead to build the booster first, along with a cargo-only upper stage - which is much simpler than the life support requiring Mars ship - and use that as a fully recoverable heavy payload dispenser to replace Falcon Heavy sooner rather than later.

That could allow RTLS and full recovery for all SpaceX missions to orbit.

The downside is that you still need to build the entire booster rocket, which is probably the most expensive part of the endeavour.
Title: Re: ITS Development Updates and Discussion Thread
Post by: Kaputnik on 04/03/2017 10:58 am
Perhaps the suggestion of 'Falcon based core' meant to use Merlins and Al-Li tankage, but not necessarily stick to the current diameter. I think it would need to be wider simply to fit enough engines under it anyway.

IMHO it would be a huge development project to kludge together a rocket stage that would only fly a handful of times and bear no relation to any future development. And we all know that SpaceX try their best not to duplicate what NASA are already doing.
Title: Re: ITS Development Updates and Discussion Thread
Post by: Rei on 04/03/2017 11:55 am
I think their timeline was too optimistic, which is OK, IMHO. I also think that they need to do a lot of testing of their rocket before they fly people on it, which is why I still think that a SSTO version of the ITS would be an ideal way to gather a lot of experience with the thing quickly (not trying to derail the thread to the SSTO discussion again, which there are other threads for). Is it only me or did it feel like Musk was indicating other uses for the ITS (or LVs based on the basic architecture), once it came online. I mean during the SES 10 press conference, he talking about how the ITS would improve the cost for getting payloads to space a lot over the current architecture.

That was my take as well. Which would be suggestive that there would be a payload-only variant. Which logic would dictate would come first, as it's simpler and validates the system before man-rating it.

Which raises an interesting possibility. The second stage is much smaller and surely much cheaper than the first. They built a test article for the 2nd stage LOX tank as well, but as far as we know haven't made any test articles for the booster. The concept that they'll end up with a 2nd stage spaceship without a booster for it does not seem unrealistic at all.

Your concept is that they'd flight test it as a SSTO. But then it would have a terrible payload fraction. By contrast, if they made an interstage to mount it to a Falcon-based core, they could get a really massive payload, particularly to high orbits. And they'd get to keep using their existing Falcon infrastructure, while building up flight experience with the stage and working on the booster.

Is it even feasible to put a 17 meter diameter second stage on a 3.6m diameter Falcon 9 booster?

Backwards.  Falcon core atop ITS s-II.  And given the sort of launch cadence SpaceX wants to maintain and how long it would take to develop ITS s-I, "launch a few times" wouldn't describe the situation at all.

Note that ITS isn't actually 17m diameter - it's 17m with the fins, but the core is 12m. 

The net result would be rather "Russian" in appearance, with a somewhat conical base (ITS s-II, rather than boosters) scaling down (interstage) to a thinner core (3,6m / Falcon). They already have the upper stage (F9). They plan to make ITS s-II regardless. The additional engineering vs. flying ITS s-II as a tiny-payload-fraction SSTO is the interstage.

Technically - although it'd be quite an unusual design, something I can't think of any other examples of - you could have a FH or similar at the top, boosters and all. They'd fit nicely over the core.  Even aiding in stabilization.
Title: Re: ITS Development Updates and Discussion Thread
Post by: rsdavis9 on 04/03/2017 12:50 pm
I think their timeline was too optimistic, which is OK, IMHO. I also think that they need to do a lot of testing of their rocket before they fly people on it, which is why I still think that a SSTO version of the ITS would be an ideal way to gather a lot of experience with the thing quickly (not trying to derail the thread to the SSTO discussion again, which there are other threads for). Is it only me or did it feel like Musk was indicating other uses for the ITS (or LVs based on the basic architecture), once it came online. I mean during the SES 10 press conference, he talking about how the ITS would improve the cost for getting payloads to space a lot over the current architecture.

That was my take as well. Which would be suggestive that there would be a payload-only variant. Which logic would dictate would come first, as it's simpler and validates the system before man-rating it.

Which raises an interesting possibility. The second stage is much smaller and surely much cheaper than the first. They built a test article for the 2nd stage LOX tank as well, but as far as we know haven't made any test articles for the booster. The concept that they'll end up with a 2nd stage spaceship without a booster for it does not seem unrealistic at all.

Your concept is that they'd flight test it as a SSTO. But then it would have a terrible payload fraction. By contrast, if they made an interstage to mount it to a Falcon-based core, they could get a really massive payload, particularly to high orbits. And they'd get to keep using their existing Falcon infrastructure, while building up flight experience with the stage and working on the booster.

Is it even feasible to put a 17 meter diameter second stage on a 3.6m diameter Falcon 9 booster?

Backwards.  Falcon core atop ITS s-II.  And given the sort of launch cadence SpaceX wants to maintain and how long it would take to develop ITS s-I, "launch a few times" wouldn't describe the situation at all.

Note that ITS isn't actually 17m diameter - it's 17m with the fins, but the core is 12m. 

The net result would be rather "Russian" in appearance, with a somewhat conical base (ITS s-II, rather than boosters) scaling down (interstage) to a thinner core (3,6m / Falcon). They already have the upper stage (F9). They plan to make ITS s-II regardless. The additional engineering vs. flying ITS s-II as a tiny-payload-fraction SSTO is the interstage.

Technically - although it'd be quite an unusual design, something I can't think of any other examples of - you could have a FH or similar at the top, boosters and all. They'd fit nicely over the core.  Even aiding in stabilization.

Yes I had the same thought.
Title: Re: ITS Development Updates and Discussion Thread
Post by: AncientU on 04/03/2017 01:15 pm
If I had to get to ITS without going bankrupt, I'd first use the launch facilities currently available (or soon to be available) -- size the booster to use same flame trenches, HIFs, etc. to maximum extent.  The approximately half-scale booster (maybe 10m diameter, 15mlbf thrust) would even possibly be made of Li-Al.  Second stage would be either ITS-like lander (probably Carbon composite) or conventional Li-Al second stage with 10-12m recoverable fairing; payload could still be about 200t.  Landing could be on legs scaled up from Falcon... at existing landing pads.  Later, would test cradle landing at these same landing pads by removing legs, adding triple centering struts, and placing cradle at the landing pad until concept proven.  (Use the over-sized center pad at Cape first.)  TEL could be fitted with different base plate and same pad facilities used.

ITS-like second stages would still refuel from tankers or depots before doing Earth departure -- again proving another aspect of the original concept without going all the way to ITS scale.  MARS EDL WOULD ALSO GET SHAKEN OUT WITH MAYBE 'ONLY' 100T DELIVERIES TO THE SURFACE. A reusable second stage specifically designed for ConnX or other vendor constellations (think DoD dis-aggregation effort...) deliveries could generate early revenue.

A completely new factory and much expensive tooling will be needed for ITS.  That alone will stretch the R&D budget... but it could be made to accommodate a half-scale version with scaleability to full planned into the machinery and facilities without adding huge costs.

Biggest issue -- in this new age of getting the manifest launched as prime focus -- is to not disrupt existing manifest deliveries.  New and unique launch facilities for ITS can follow in good time.

Putting off ITS development for five years will not save money nor will it further the motivating plans for Mars development.  Musk wouldn't be 'excited' about a (planned) delay.

Quote
E: Yes the first one will be uncrewed, I don't want to steal thunder from that announcement. I'm pretty excited about the upgrades* strategy since Gh, it makes a lot more sense, it's - we have to not just get it done technically, but figure out how to get this done without going bankrupt.
Emphasis, * mine

* upgrades is plural

Edit: added EM quote

Title: Re: ITS Development Updates and Discussion Thread
Post by: Kaputnik on 04/03/2017 01:30 pm
There must be a limit on how much landing thrust a cocnrete pad can take.
But on the whole, I am one of those in the 'subscale demo would be nice' camp.
Perhaps once F9 design is frozen at block 5, they will unveil an eventual replacement that uses the key technologies from ITS on a smaller and fully recoverable vehicle.
Title: Re: ITS Development Updates and Discussion Thread
Post by: Rei on 04/03/2017 02:05 pm
Yes I had the same thought.

It also occurred to me that  you wouldn't have to scrap the design when ITS s-I came online.  You could keep it around for when you want very high dV launches of heavy payloads - aka ITS s-I + ITS s-II + Fx.    For example, if NASA wanted to launch a Cassini-sized craft to "Planet 9" or whatnot. Indeed, you could stack a Centaur on the top of the Falcon, and a Cassini-sized vehicle on top the Centaur.  That would be some bloody insane dV.  Also available for when you need very fast transfers of payloads to Mars (such as emergency supplies).

Now, if they ended up using Falcon as a third stage a lot it'd make sense to start work on a higher impulse replacement designed for storable propellant. But so long as they have it, and have a system powerful enough to launch it...
Title: Re: ITS Development Updates and Discussion Thread
Post by: rsdavis9 on 04/03/2017 03:11 pm
Yes I had the same thought.

It also occurred to me that  you wouldn't have to scrap the design when ITS s-I came online.  You could keep it around for when you want very high dV launches of heavy payloads - aka ITS s-I + ITS s-II + Fx.    For example, if NASA wanted to launch a Cassini-sized craft to "Planet 9" or whatnot. Indeed, you could stack a Centaur on the top of the Falcon, and a Cassini-sized vehicle on top the Centaur.  That would be some bloody insane dV.  Also available for when you need very fast transfers of payloads to Mars (such as emergency supplies).

Now, if they ended up using Falcon as a third stage a lot it'd make sense to start work on a higher impulse replacement designed for storable propellant. But so long as they have it, and have a system powerful enough to launch it...

The questions are:
1. ITS s2 is optimized for upper atmosphere. So some loss of performance here.
2. How much damage to the design(extra work) does fitting a interstage to the top of ITS s2 do?
3. obviously interstage is extra work.

Goal is to minimize extra work which takes you off the ELON path.
Title: Re: ITS Development Updates and Discussion Thread
Post by: philw1776 on 04/03/2017 03:42 pm
IF Elon is concerned about funding to develop ITS, the colonial version with massive colonial payloads, then the R&D to develop a sub-scale ITS adds R&D cost AND delays the "real" colonial capable ITS if only for the reason that generating the the sub-scale R&D funds delay funds for "real" ITS.

Early flights of ITS do NOT need to have all engines, all subsystems like ECLSS, etc.  Plenty of opportunity to gain much needed flight experience with less expensive under equipped ITS and then later, the under equipped booster.  Fits the way SpaceX engineers, build something, fly it, up-rev the design closer to desired full spec, fly some more and then finally arrive at F9 FT Block 5 or whatever.

Did SpaceX build the Falcon 5 before building the Falcon 9?  No.
Would that additional tooling expense, R&D expense, misc expense have cut into F9 R&D expense? Yes.
Title: Re: ITS Development Updates and Discussion Thread
Post by: uhuznaa on 04/03/2017 04:03 pm
The best way to build ITS without bankrupting the company would be to turn it into a business i.e. to make money with it. And not only when it goes to Mars, because until then you're basically bleeding money for a decade or so.

So I think they should scale the thing down and use more generous mass fractions to end up with maybe 50t to LEO to get a fully reusable workhorse launcher to replace the F9 and FH with something cheaper (due to full and rapid reuse). Use 1/3 scale Raptors and aluminum tanks and airframes instead of composites. This would be enough to serve the satellite business just perfectly (with using a kicker stage for GTO missions). Then build the full thing with the money you can earn with that and with the experiences you gather while building the smaller and less demanding first iteration.

And I don't think building that monster launcher from scratch is a good idea anyway. It's a bit as if SpaceX would have left out the Falcon 1 and went straight for a reusable Falcon 9 from nothing. I bet they will crash and burn more than just one ITS prototype and it's much cheaper to fail with a smaller version. It's also easier to get something up and flying with more generous margins and only then shave off mass than going straight to crazy mass fractions with full reusability. They need to add a rung to that ladder to be able to climb it.

But of course this would delay the Mars plan, so if Elon finds a better way, great. It's just that I don't see the realistic near-future business case for ITS; selling cargo flights to Mars is just too far away to find someone handing over tens of billions for making it happen NOW. Even the SpaceX satellite constellation plan seems impossible to do with the Falcon 9 (or Heavy). You would already need a fully and rapidly reusable launcher for that.
Title: Re: ITS Development Updates and Discussion Thread
Post by: AncientU on 04/03/2017 04:43 pm
The thing is, it wouldn't delay the Mars plan.
A sub-scale version would be built quicker and it could start Mars deliveries as soon as it is ready.  The full colony-mode vehicle will be needed for the full colony development, not the first efforts to prove the technology (carbon composite tankage, belly-first atmospheric reentry, fully reusable tankers, on-orbit refueling, Mars EDL with 100t payloads (mankind has done almost one tonne so far), refueling on Mars (!!!), return from Mars, Earth EDL at Mars return speeds, etc.).  This phase is easily ten years (more realistically twenty) from first flight until hundreds of passengers/colonists would board first vehicle.

Hard to understand why a 200t payload vehicle wouldn't be just the thing to lay groundwork for massive colonial payloads.

This is similar to the argument about a full-up New Glenn on Blue's first orbital flight -- except at a scale in several dimensions of parameter space never before built in history, for missions never before attempted. 
Won't happen.

Good news -- we won't have to wait long for the new plan.
Quote
Musk says SpaceX will have an update on the design of their Interplanetary Transport System posted on their website in about a month.
Tweet from Jeff Foust
Title: Re: ITS Development Updates and Discussion Thread
Post by: DanielW on 04/03/2017 05:04 pm
I don't think there is any merit in trying to resize the ITS to serve existing markets. Those markets are either met or not, SpaceX would only lose money by cannibalizing the Falcon market. You have to size it for a market you are trying to create.

The big limitation is the pad. SpaceX can't magically make one big enough appear. So I suspect the BFR will get resized to a reasonable thrust level for 39A and or Boca Chica.

The rest of the system will shrink accordingly. Any loss in capability to Mars will be made up on volume. More refueling flights or even early flights use a fleet.
Title: Re: ITS Development Updates and Discussion Thread
Post by: uhuznaa on 04/03/2017 05:45 pm
You have to size it for a market you are trying to create.

But exactly this is the economic problem here. You need to spend lots and lots of money first to create a market (like "300 tons of cargo to Mars") that doesn't exist yet and that you can't guarantee will ever exist. If you HAVE that kind of money, Ok. Just do it, and then win or not.

But if you don't have it and need someone to give 10 billion or so to you to create it, you need to convince him that a) you can do it and b) it's a good investment. Both are pretty hard sells from where SpaceX stands right now.

I mean, you may think otherwise, but that's irrelevant because probably you don't have $10B to give to SpaceX anyway. Elon said that ITS will cost at least ten billion and SpaceX will invest 5 million a year now. This way ITS will not be build any time soon. They need to convince someone to give them the money and one way to do it would be to build something along that lines to demonstrate they can do it and the only way they can do this is by building something that has a market now and on Earth. Not in 10 years on Mars.

If you see the business case with ITS, tell me. Right now it's a dream, not a plan. That's why I talked about a ladder: Something with a rung on the bottom (Falcon) and one on the top (ITS) is not a ladder. You need to add rungs in between to climb it even if your actual goal is on the top. Just liking the top rung very much is not going to help you getting there.
Title: Re: ITS Development Updates and Discussion Thread
Post by: DanielW on 04/03/2017 07:46 pm
You have to size it for a market you are trying to create.

But exactly this is the economic problem here. You need to spend lots and lots of money first to create a market (like "300 tons of cargo to Mars") that doesn't exist yet and that you can't guarantee will ever exist. If you HAVE that kind of money, Ok. Just do it, and then win or not.

But if you don't have it and need someone to give 10 billion or so to you to create it, you need to convince him that a) you can do it and b) it's a good investment. Both are pretty hard sells from where SpaceX stands right now.

I mean, you may think otherwise, but that's irrelevant because probably you don't have $10B to give to SpaceX anyway. Elon said that ITS will cost at least ten billion and SpaceX will invest 5 million a year now. This way ITS will not be build any time soon. They need to convince someone to give them the money and one way to do it would be to build something along that lines to demonstrate they can do it and the only way they can do this is by building something that has a market now and on Earth. Not in 10 years on Mars.

If you see the business case with ITS, tell me. Right now it's a dream, not a plan. That's why I talked about a ladder: Something with a rung on the bottom (Falcon) and one on the top (ITS) is not a ladder. You need to add rungs in between to climb it even if your actual goal is on the top. Just liking the top rung very much is not going to help you getting there.

Having the ITS launch payloads that the falcon family can handle does not get you any extra money. SpaceX is already capturing the available revenue from those existing markets. It can't double capture it by building ITS to perform the same missions. One way or another Falcon needs to pay for ITS. It makes sense to build the ITS to strictly address a different market, even if that market is a pipe dream.

SpaceX knows that they aren't going anywhere without better revenue streams. So while they are hoping that one day NASA will be tasked with buying SpaceX trips to Mars, they are betting that falcon can loft a true cash cow in the form of commX. It is a long bet, and they need falcon to take them there.
Title: Re: ITS Development Updates and Discussion Thread
Post by: DanielW on 04/03/2017 08:02 pm
In terms of a business case for ITS, I think that is coming clearer in interesting ways. Look at Red Dragon and the Circumlunar mission. There is definitely interest in turnkey solutions. It is not a full blown market yet because the technology is not demonstrated. Currently Nasa would not mind at all getting some payloads and Data out of Red Dragon As long as it fits existing budgets, and wealthy individuals are taking notice of the BEO opportunities on Dragon.

Elon Noted in his talk that a Mars and back capable system ends up being basically an anywhere capable system. Thus if they can nail the Mars design, they suddenly have markets of opportunity wherever anyone wants to go. Perhaps it will never be the optimal solution for robotic missions, but if a system suddenly exists (proven) that can do anywhere in cis-lunar space, NEO's Lagrange points, Mars, etc. Suddenly you are the baseline for every proposed BEO human mission. (studies by Lockheed trying to necessitate Orion very much withstanding).

I think SpaceX may very well end up a Moon First company just because they can't say no to the money that wants to go there.
Title: Re: ITS Development Updates and Discussion Thread
Post by: rsdavis9 on 04/03/2017 08:10 pm


If you see the business case with ITS, tell me. Right now it's a dream, not a plan. That's why I talked about a ladder: Something with a rung on the bottom (Falcon) and one on the top (ITS) is not a ladder. You need to add rungs in between to climb it even if your actual goal is on the top. Just liking the top rung very much is not going to help you getting there.

It all boils down to whether Elon can bypass the middle rungs of the ladder and thereby save some cheese(dollars).

Is f9 family enough to test out all the concepts of reusability he needs for ITS?
Is the team he has now assembled capable of designing ITS from scratch in one iteration?
Does he have the chutzpah to go the quick and gutsy approach?

Knowing Musk I think he might try.

The new ideas that need to be tried out are:
1. composite cryogenic tanks.
A. He has some intimate experience with composites and cryogenics  :)

2. FFSC engine.
A. He knows about designing engines.

3. Does he need to fly with this new tech to prove it out?
A. Look at BO. They seem have done just fine designing without flying.

Once ITS is flying there will be ready sources of income for near earth missions. Without having to redesign for a different vehicle.
Title: Re: ITS Development Updates and Discussion Thread
Post by: uhuznaa on 04/03/2017 08:18 pm
You have to size it for a market you are trying to create.

But exactly this is the economic problem here. You need to spend lots and lots of money first to create a market (like "300 tons of cargo to Mars") that doesn't exist yet and that you can't guarantee will ever exist. If you HAVE that kind of money, Ok. Just do it, and then win or not.

But if you don't have it and need someone to give 10 billion or so to you to create it, you need to convince him that a) you can do it and b) it's a good investment. Both are pretty hard sells from where SpaceX stands right now.

I mean, you may think otherwise, but that's irrelevant because probably you don't have $10B to give to SpaceX anyway. Elon said that ITS will cost at least ten billion and SpaceX will invest 5 million a year now. This way ITS will not be build any time soon. They need to convince someone to give them the money and one way to do it would be to build something along that lines to demonstrate they can do it and the only way they can do this is by building something that has a market now and on Earth. Not in 10 years on Mars.

If you see the business case with ITS, tell me. Right now it's a dream, not a plan. That's why I talked about a ladder: Something with a rung on the bottom (Falcon) and one on the top (ITS) is not a ladder. You need to add rungs in between to climb it even if your actual goal is on the top. Just liking the top rung very much is not going to help you getting there.

Having the ITS launch payloads that the falcon family can handle does not get you any extra money. SpaceX is already capturing the available revenue from those existing markets. It can't double capture it by building ITS to perform the same missions. One way or another Falcon needs to pay for ITS. It makes sense to build the ITS to strictly address a different market, even if that market is a pipe dream.

SpaceX knows that they aren't going anywhere without better revenue streams. So while they are hoping that one day NASA will be tasked with buying SpaceX trips to Mars, they are betting that falcon can loft a true cash cow in the form of commX. It is a long bet, and they need falcon to take them there.

You need a cheaper way to launch these 4000 satellites than Falcon 9. Even if you can launch 10 of them with one launch this means 400 launches.

And I do NOT mean ITS to launch payloads that the falcon family can handle. I mean a fully and rapidly reusable launcher build along the same ideas as ITS. Smaller and with more conservative mass fractions, serving the same market as the F9 and FH.

Both the Falcon 9 and Falcon Heavy are already hitting their limits. Falcon 9 has an expendable LEO payload of 18t, but there is no way to put such a payload on it, it is already volume limited. This is even worse with the theoretical 50t to LEO of the Falcon Heavy. Where do you put 50t of stuff on that skinny thing? It will never launch 50t to LEO.

Falcon is great if you want to conquer the existing market for launches in its payload class. But for nothing else and this is a very limited market even with lower prices. Even if SpaceX makes 10 million per launch, it would need to launch it 1000 times to get the 10 billion to build ITS and THEN convince people to buy payloads to Mars.

But I don't need to convince anyone here. I have one thing learned about Elon Musk: He knows what he needs to do to be able to do what he wants. He will try to make ITS interesting enough to find someone who throws money at him and if he doesn't find that he will try to earn the money with SpaceX. And this will mean he will build an ITS-like craft to replace F9 and FH and conquer LEO before Mars. It's just the sensible and logical thing to do for SpaceX. The F9 and FH will just be one rung on the ladder to Mars and there will be more than one rung between here and there.
Title: Re: ITS Development Updates and Discussion Thread
Post by: rsdavis9 on 04/03/2017 08:23 pm
But I don't need to convince anyone here. I have one thing learned about Elon Musk: He knows what he needs to do to be able to do what he wants. He will try to make ITS interesting enough to find someone who throws money at him and if he doesn't find that he will try to earn the money with SpaceX. And this will mean he will build an ITS-like craft to replace F9 and FH and conquer LEO before Mars. It's just the sensible and logical thing to do for SpaceX. The F9 and FH will just be one rung on the ladder to Mars and there will be more than one rung between here and there.

And he will probably surprise both of us by doing something outrageous and completely different.
Title: Re: ITS Development Updates and Discussion Thread
Post by: uhuznaa on 04/03/2017 08:31 pm
But I don't need to convince anyone here. I have one thing learned about Elon Musk: He knows what he needs to do to be able to do what he wants. He will try to make ITS interesting enough to find someone who throws money at him and if he doesn't find that he will try to earn the money with SpaceX. And this will mean he will build an ITS-like craft to replace F9 and FH and conquer LEO before Mars. It's just the sensible and logical thing to do for SpaceX. The F9 and FH will just be one rung on the ladder to Mars and there will be more than one rung between here and there.

And he will probably surprise both of us by doing something outrageous and completely different.

Yeah, being outrageously sensible is the most outrageous way of being outrageous ;-)

I have always found that nothing what he does is in any way crazy. It's logical and sane and sensible and it only seems to be crazy because being logical and sane and sensible is so extremely rare.

Title: Re: ITS Development Updates and Discussion Thread
Post by: MikeAtkinson on 04/03/2017 09:32 pm
Outfitted as a space station on the ground, the ITS ship would make a fine medium size space station. It could be deorbited after a few years for refurbishment and updating with new equipment and experiments. Could have more than one in various orbits.

With refuelling, this ITS space station could self ferry anywhere in cis-lunar space or beyond.

Advantage for SpaceX, is that it maintains the highly profitable commercial cargo and crew business, and it develops an entirely new business in space stations.
Title: Re: ITS Development Updates and Discussion Thread
Post by: DanielW on 04/03/2017 09:42 pm
Outfitted as a space station on the ground, the ITS ship would make a fine medium size space station. It could be deorbited after a few years for refurbishment and updating with new equipment and experiments. Could have more than one in various orbits.

With refuelling, this ITS space station could self ferry anywhere in cis-lunar space or beyond.

Advantage for SpaceX, is that it maintains the highly profitable commercial cargo and crew business, and it develops an entirely new business in space stations.

I am pretty sure this has been covered before. ITS would not make a great space station for all the reasons that mobile homes don't make great houses. Far too much compromise since the design criteria have only a little overlap.
Title: Re: ITS Development Updates and Discussion Thread
Post by: uhuznaa on 04/03/2017 09:44 pm
Outfitted as a space station on the ground, the ITS ship would make a fine medium size space station. It could be deorbited after a few years for refurbishment and updating with new equipment and experiments. Could have more than one in various orbits.

With refuelling, this ITS space station could self ferry anywhere in cis-lunar space or beyond.

Advantage for SpaceX, is that it maintains the highly profitable commercial cargo and crew business, and it develops an entirely new business in space stations.

It would make a great short-time luxury space hotel for a few weeks (then return, clean and resupply/redecorate), but you still would need a dedicated launcher for the guests, because you're not going to launch paying customers without a launch escape system.
Title: Re: ITS Development Updates and Discussion Thread
Post by: DanielW on 04/03/2017 10:00 pm
Outfitted as a space station on the ground, the ITS ship would make a fine medium size space station. It could be deorbited after a few years for refurbishment and updating with new equipment and experiments. Could have more than one in various orbits.

With refuelling, this ITS space station could self ferry anywhere in cis-lunar space or beyond.

Advantage for SpaceX, is that it maintains the highly profitable commercial cargo and crew business, and it develops an entirely new business in space stations.

It would make a great short-time luxury space hotel for a few weeks (then return, clean and resupply/redecorate), but you still would need a dedicated launcher for the guests, because you're not going to launch paying customers without a launch escape system.

Why is it returning? Even if mass to orbit was free, it's time would be better monetized by having it work continually. Dedicated in-space structures will always be superior. Structures that stay put don't need to have killer mass fractions and are not constrained on volume or shape. That allows you to put more effort into robustness, safety margins, utility, and luxuries.

For instance, a giant expandable habitat with a full meter of water in the outer wall is something that we can entertain as a possibility for radiation protection. It would just take lots of flights to fill it. For an EDL capable spaceship we can't propose the same with a straight face.
Title: Re: ITS Development Updates and Discussion Thread
Post by: Robotbeat on 04/04/2017 01:50 am
I should point out that the difference between Falcon Heavy and ITS are not that great. Falcon Heavy gets a max of 25MN, while the ITS booster is 138MN, less than a factor of 6 different. 42 engines for the booster isn't much more than 27 for FH. The single-stick design is simpler. Red Dragon and BFS are also similar. Both use supersonic retro propulsion for landing, use a lifting trajectory, are shielded by PICA-X, and have landing legs. ITS is integrated with its upperstage and would land similar to a Falcon booster.

All in all, the step between Dragon2/RedDragon/FalconHeavy and ITS is probably smaller in some respects than from Falcon 1 and Falcon9+Dragon, which had a factor of 9 difference in thrust, an order of magnitude more engines, have to deal with orbital entry and on-orbit operations, etc.

And the difference between New Shepard and New Glenn is 35x in thrust, and far more complicated due to multiple stages, orbital operations, etc.
Title: Re: ITS Development Updates and Discussion Thread
Post by: AncientU on 04/05/2017 12:41 am
I should point out that the difference between Falcon Heavy and ITS are not that great. Falcon Heavy gets a max of 25MN, while the ITS booster is 138MN, less than a factor of 6 different. 42 engines for the booster isn't much more than 27 for FH. The single-stick design is simpler. Red Dragon and BFS are also similar. Both use supersonic retro propulsion for landing, use a lifting trajectory, are shielded by PICA-X, and have landing legs. ITS is integrated with its upperstage and would land similar to a Falcon booster.

All in all, the step between Dragon2/RedDragon/FalconHeavy and ITS is probably smaller in some respects than from Falcon 1 and Falcon9+Dragon, which had a factor of 9 difference in thrust, an order of magnitude more engines, have to deal with orbital entry and on-orbit operations, etc.

And the difference between New Shepard and New Glenn is 35x in thrust, and far more complicated due to multiple stages, orbital operations, etc.

Made the same comparison a while back.
NG is a huge leap for Blue -- a factor of 35x in thrust and an orbital launcher vs. NS -- yet doable by seeming consensus here.  (BTW, I'm part of that consensus.)

Comparing huge leaps, ITS is also a leap for SpaceX over F9(or FH) -- a factor of 20x(or 6x) in thrust, without the complication of adding orbital tech, but with the unknown of carbon composite construction.

They are interestingly on roughly the same timeline.  They are neck and neck on engine development; both are testing engines that are much more complicated than any produced in house to date and using methane/LNG, a new propellant for each as well as the industry.  Cash flow could be the deciding factor, but that aside (assume sufficient cash flows to each), which company has the greater technical challenge ahead?


That said, building the booster should be the easiest part.

Where there is a 'bit' of a challenge...

Refueling a thousand tonnes of deep cryogen onto second stage (hopefully without incident)
...in LEO (1)
Landing second stage of a few hundred tonnes
...on Mars(2)
Refueling SSTO vehicle
...with fuel made on Mars (3)
Reflying second stage
...from Mars to Earth(4)


(1) Zero cryogenic transfers yet in history
(2) 2.5 orders of magnitude more massive than anything yet landed
(3) This is really hard
(4) Mars sample return (few 100 grams) will be multi-billion dollar NASA mission, some day -- this is 5-6 orders of magnitude more mass than that
Title: Re: ITS Development Updates and Discussion Thread
Post by: Robotbeat on 04/05/2017 02:15 am
The Mars side IS really hard. To fully refuel one ITS in 26 months takes about 1 Megawatt of average power, i.e. about 4MW of solar plus batteries. About 100tons conventionally, with cleverness perhaps more like 20-50 tons. And then you also have to find the water to feed the ISRU plant.
Title: Re: ITS Development Updates and Discussion Thread
Post by: mikelepage on 04/05/2017 05:14 am
Maybe I've missed something, but I'm wondering about where the development of Falcon Heavy centre core fits in all this.  Last I heard, they're not doing cross-feed between the boosters and centre core, and I gather the centre core is also needing to be redesigned/reinforced to properly handle the thrust of each of the boosters.

So, since the commonality between centre cores and boosters is becoming increasingly divergent, what is keeping SpaceX from developing the centre core of Falcon Heavy into something more "ITS-like"? Maybe a larger diameter centre core with raptors, plus reused F9 boosters, would be capable of launching a first generation ITS-spaceship?

I know hybrid-fueled RP1-LOX lower stage(s) + MethaLox upper stage systems have been ruled out before, but is there any intrinsic reason why it can't be done? or just the added complications at the launch site?
Title: Re: ITS Development Updates and Discussion Thread
Post by: colbourne on 04/05/2017 06:02 am
The Mars side IS really hard. To fully refuel one ITS in 26 months takes about 1 Megawatt of average power, i.e. about 4MW of solar plus batteries. About 100tons conventionally, with cleverness perhaps more like 20-50 tons. And then you also have to find the water to feed the ISRU plant.
Would it not  be best to build the  base using many one way trips initially and leave the re-fuelling plant until we have many people on Mars and a large base. The ITS craft would be useful for their raw materials as well as being living quarters etc.
It seems a waste to me to ship so many tonnes of valuable processed metal to Mars to then send it immediately back to Earth when  the purpose of the mission is to build a sustainable Mars base. There is most certainly going to be a shortage of power anyway, so spending 4MW on refueling seems excessive in the early stages when survival and exploration should be the priority.
Could it be for political reasons that a return craft is being considered so early in the mission.
Title: Re: ITS Development Updates and Discussion Thread
Post by: Lumina on 04/05/2017 07:11 am
By the time ITS is ready to fly, the reusable Falcon 9 will be a cash cow, quickly recovering some of the past investment in F9 development and funding some of the ITS development and NRE costs. The first launch customers for ITS will effectively fund ITS the rest of the way to its first flight.
Title: Re: ITS Development Updates and Discussion Thread
Post by: AncientU on 04/05/2017 10:44 am
The Mars side IS really hard. To fully refuel one ITS in 26 months takes about 1 Megawatt of average power, i.e. about 4MW of solar plus batteries. About 100tons conventionally, with cleverness perhaps more like 20-50 tons. And then you also have to find the water to feed the ISRU plant.
Would it not  be best to build the  base using many one way trips initially and leave the re-fuelling plant until we have many people on Mars and a large base. The ITS craft would be useful for their raw materials as well as being living quarters etc.
It seems a waste to me to ship so many tonnes of valuable processed metal to Mars to then send it immediately back to Earth when  the purpose of the mission is to build a sustainable Mars base. There is most certainly going to be a shortage of power anyway, so spending 4MW on refueling seems excessive in the early stages when survival and exploration should be the priority.
Could it be for political reasons that a return craft is being considered so early in the mission.

I believe the plan is to send hardware shipments to Mars first -- the ISRU facilities, including water processing and storage -- and possibly not return the ship(s) that delivered them... old discussion, so sorry for retriggering it.  But setting up an early return demonstration is as important, because you need to be able to get the people and expensive ship back.  One way to Mars isn't the plan.
Title: Re: ITS Development Updates and Discussion Thread
Post by: rsdavis9 on 04/05/2017 12:23 pm
The Mars side IS really hard. To fully refuel one ITS in 26 months takes about 1 Megawatt of average power, i.e. about 4MW of solar plus batteries. About 100tons conventionally, with cleverness perhaps more like 20-50 tons. And then you also have to find the water to feed the ISRU plant.

Shouldn't need batteries for ISRU plant. The plant should be able to run when the sun shines.(?)
Batteries for other things though but not nearly the size that the ISRU would need.

I guess this is assuming the ISRU can be turned off and on easily without any loss of performance.

Sort of the same problem here on earth. Use batteries to even load or just adjust demand during the day.
Examples:
Electricity for aluminum production should be able to be turned off and on.
Lime cooking for concrete. Maybe.
Etc.
Title: Re: ITS Development Updates and Discussion Thread
Post by: Robotbeat on 04/05/2017 12:29 pm
Whether batteries are the way to go or not depends on the specific power of the ISRU plant, too. If the ISRU plant is heavy, it still might make sense to use batteries so it can operate during the night, too. Or perhaps the electrolyzer could run during the day only while the rest operates continuously. Hard to tell without knowing the specific power of the ISRU plant vs batteries.

Also, battery technology continues to improve. Lithium-sulfur is potentially twice as good as current state of the art lithium ion. And there are even more sophisticated battery chemistries that are on the horizon.
Title: Re: ITS Development Updates and Discussion Thread
Post by: uhuznaa on 04/05/2017 07:59 pm
I should point out that the difference between Falcon Heavy and ITS are not that great. Falcon Heavy gets a max of 25MN, while the ITS booster is 138MN, less than a factor of 6 different. 42 engines for the booster isn't much more than 27 for FH. The single-stick design is simpler. Red Dragon and BFS are also similar. Both use supersonic retro propulsion for landing, use a lifting trajectory, are shielded by PICA-X, and have landing legs. ITS is integrated with its upperstage and would land similar to a Falcon booster.

All in all, the step between Dragon2/RedDragon/FalconHeavy and ITS is probably smaller in some respects than from Falcon 1 and Falcon9+Dragon, which had a factor of 9 difference in thrust, an order of magnitude more engines, have to deal with orbital entry and on-orbit operations, etc.

And the difference between New Shepard and New Glenn is 35x in thrust, and far more complicated due to multiple stages, orbital operations, etc.


The ITS first stage, yes. The second stage (the Mars ship), no. Everything around it is just without comparison to anything. It is planned to have only a slightly worse mass fraction (without payload) than the current F9 second stage, despite being a full, reusable spacecraft with heat shield and cargo hold and landing legs and everything to Mars and back. It's like making the F9 second stage reusable while integrating the fairing as a cargo hold. This is a major undertaking with no examples to follow and it will not succeed at the first try.

The current F9 second stage has a mass fraction of 96.1%. The ITS second stage one of 92.3%. This would still be quite good for a boring second stage without nothing else (while the F9 second stage mass fraction is quite a record for second stages anyway). The ITS tanker is planned to have a mass fraction of 96.5%, that is BETTER than the current second stage while being fully reusable, including legs and heat shield and everything. Nobody did anything like that before even remotely. It would be the second stage with the best mass fraction of all times while being fully reusable at the same time.

Is it impossible? No, the laws of physics would be perfectly fine with it. Is is hard and never been done before? Yes. By far. Nobody did anything like that before. And they WILL crash more than one prototype before they get it done and therefore they would be wise to do that with a cheaper version and one they earn money with by delivering a payload before it has to land again. Just as they did it with Falcon 9.

And Elon will know that very well and will in a year or two nail another rung onto that ladder to Mars because he will have to, as much as he wants to get there in one step. Give me an upvote then if you like.
Title: Re: ITS Development Updates and Discussion Thread
Post by: DanielW on 04/05/2017 08:21 pm
I should point out that the difference between Falcon Heavy and ITS are not that great. Falcon Heavy gets a max of 25MN, while the ITS booster is 138MN, less than a factor of 6 different. 42 engines for the booster isn't much more than 27 for FH. The single-stick design is simpler. Red Dragon and BFS are also similar. Both use supersonic retro propulsion for landing, use a lifting trajectory, are shielded by PICA-X, and have landing legs. ITS is integrated with its upperstage and would land similar to a Falcon booster.

All in all, the step between Dragon2/RedDragon/FalconHeavy and ITS is probably smaller in some respects than from Falcon 1 and Falcon9+Dragon, which had a factor of 9 difference in thrust, an order of magnitude more engines, have to deal with orbital entry and on-orbit operations, etc.

And the difference between New Shepard and New Glenn is 35x in thrust, and far more complicated due to multiple stages, orbital operations, etc.


The ITS first stage, yes. The second stage (the Mars ship), no. Everything around it is just without comparison to anything. It is planned to have only a slightly worse mass fraction (without payload) than the current F9 second stage, despite being a full, reusable spacecraft with heat shield and cargo hold and landing legs and everything to Mars and back. It's like making the F9 second stage reusable while integrating the fairing as a cargo hold. This is a major undertaking with no examples to follow and it will not succeed at the first try.

The current F9 second stage has a mass fraction of 96.1%. The ITS second stage one of 92.3%. This would still be quite good for a boring second stage without nothing else (while the F9 second stage mass fraction is quite a record for second stages anyway). The ITS tanker is planned to have a mass fraction of 96.5%, that is BETTER than the current second stage while being fully reusable, including legs and heat shield and everything. Nobody did anything like that before even remotely. It would be the second stage with the best mass fraction of all times while being fully reusable at the same time.

Is it impossible? No, the laws of physics would be perfectly fine with it. Is is hard and never been done before? Yes. By far. Nobody did anything like that before. And they WILL crash more than one prototype before they get it done and therefore they would be wise to do that with a cheaper version and one they earn money with by delivering a payload before it has to land again. Just as they did it with Falcon 9.

And Elon will know that very well and will in a year or two nail another rung onto that ladder to Mars because he will have to, as much as he wants to get there in one step. Give me an upvote then if you like.

Yes their plans are ambitious, but using the numbers you provided. Mass fractions of 96% for Falcon9 upper versus 92% for the spaceship. This is not "only slightly worse mass fraction" It is half the mass fraction. As musk noted in his talk any performance shortfall will be met with more refueling flights.

I suspect the new architecture will be slightly smaller just to gain price advantages in every corner of the program. However, I think adding a rung will mostly just equate to more flights until they can get the mass and performance under control.
Title: Re: ITS Development Updates and Discussion Thread
Post by: tdperk on 04/05/2017 08:56 pm
Tank testing of the first test article appears... finished.

http://imgur.com/a/bGHR6

No idea if the test was intentionally to destruction, or if the test result was a surprise. In any case, seems like they will need a new tank.

Source: https://www.reddit.com/r/spacex/comments/5ul1du/remains_of_the_its_composite_tank_in_anacortes_wa/

I read all through that Reddit, thank you for that.  Anyone else know of anything about the failure of that tank?
Title: Re: ITS Development Updates and Discussion Thread
Post by: uhuznaa on 04/05/2017 09:06 pm
I should point out that the difference between Falcon Heavy and ITS are not that great. Falcon Heavy gets a max of 25MN, while the ITS booster is 138MN, less than a factor of 6 different. 42 engines for the booster isn't much more than 27 for FH. The single-stick design is simpler. Red Dragon and BFS are also similar. Both use supersonic retro propulsion for landing, use a lifting trajectory, are shielded by PICA-X, and have landing legs. ITS is integrated with its upperstage and would land similar to a Falcon booster.

All in all, the step between Dragon2/RedDragon/FalconHeavy and ITS is probably smaller in some respects than from Falcon 1 and Falcon9+Dragon, which had a factor of 9 difference in thrust, an order of magnitude more engines, have to deal with orbital entry and on-orbit operations, etc.

And the difference between New Shepard and New Glenn is 35x in thrust, and far more complicated due to multiple stages, orbital operations, etc.


The ITS first stage, yes. The second stage (the Mars ship), no. Everything around it is just without comparison to anything. It is planned to have only a slightly worse mass fraction (without payload) than the current F9 second stage, despite being a full, reusable spacecraft with heat shield and cargo hold and landing legs and everything to Mars and back. It's like making the F9 second stage reusable while integrating the fairing as a cargo hold. This is a major undertaking with no examples to follow and it will not succeed at the first try.

The current F9 second stage has a mass fraction of 96.1%. The ITS second stage one of 92.3%. This would still be quite good for a boring second stage without nothing else (while the F9 second stage mass fraction is quite a record for second stages anyway). The ITS tanker is planned to have a mass fraction of 96.5%, that is BETTER than the current second stage while being fully reusable, including legs and heat shield and everything. Nobody did anything like that before even remotely. It would be the second stage with the best mass fraction of all times while being fully reusable at the same time.

Is it impossible? No, the laws of physics would be perfectly fine with it. Is is hard and never been done before? Yes. By far. Nobody did anything like that before. And they WILL crash more than one prototype before they get it done and therefore they would be wise to do that with a cheaper version and one they earn money with by delivering a payload before it has to land again. Just as they did it with Falcon 9.

And Elon will know that very well and will in a year or two nail another rung onto that ladder to Mars because he will have to, as much as he wants to get there in one step. Give me an upvote then if you like.

Yes their plans are ambitious, but using the numbers you provided. Mass fractions of 96% for Falcon9 upper versus 92% for the spaceship. This is not "only slightly worse mass fraction" It is half the mass fraction. As musk noted in his talk any performance shortfall will be met with more refueling flights.

I suspect the new architecture will be slightly smaller just to gain price advantages in every corner of the program. However, I think adding a rung will mostly just equate to more flights until they can get the mass and performance under control.

Hey, this "half the mass fraction" includes sitting on Mars fully fuelled and launching from it without a launchpad. The legs holding up nearly 2000 tons of fuel there alone will be a true challenge within that mass fraction. This is not just a second stage that quietly dies once in orbit, it's a full space ship meant to be able to land on Mars, hold up against the other 92% in propellants while being tanked and then launch again from those legs on the sands of Mars and land on Earth.

Nobody did anything close to that before. You don't do that in one step. The difference between a dream and a  plan is that the plan also cares for the steps to get where you want to end up.
Title: Re: ITS Development Updates and Discussion Thread
Post by: Robotbeat on 04/05/2017 11:40 pm
I should point out that the difference between Falcon Heavy and ITS are not that great. Falcon Heavy gets a max of 25MN, while the ITS booster is 138MN, less than a factor of 6 different. 42 engines for the booster isn't much more than 27 for FH. The single-stick design is simpler. Red Dragon and BFS are also similar. Both use supersonic retro propulsion for landing, use a lifting trajectory, are shielded by PICA-X, and have landing legs. ITS is integrated with its upperstage and would land similar to a Falcon booster.

All in all, the step between Dragon2/RedDragon/FalconHeavy and ITS is probably smaller in some respects than from Falcon 1 and Falcon9+Dragon, which had a factor of 9 difference in thrust, an order of magnitude more engines, have to deal with orbital entry and on-orbit operations, etc.

And the difference between New Shepard and New Glenn is 35x in thrust, and far more complicated due to multiple stages, orbital operations, etc.


The ITS first stage, yes. The second stage (the Mars ship), no. Everything around it is just without comparison to anything. It is planned to have only a slightly worse mass fraction (without payload) than the current F9 second stage, despite being a full, reusable spacecraft with heat shield and cargo hold and landing legs and everything to Mars and back. It's like making the F9 second stage reusable while integrating the fairing as a cargo hold. This is a major undertaking with no examples to follow and it will not succeed at the first try.

The current F9 second stage has a mass fraction of 96.1%. The ITS second stage one of 92.3%. This would still be quite good for a boring second stage without nothing else (while the F9 second stage mass fraction is quite a record for second stages anyway). The ITS tanker is planned to have a mass fraction of 96.5%, that is BETTER than the current second stage while being fully reusable, including legs and heat shield and everything. Nobody did anything like that before even remotely. It would be the second stage with the best mass fraction of all times while being fully reusable at the same time.

Is it impossible? No, the laws of physics would be perfectly fine with it. Is is hard and never been done before? Yes. By far. Nobody did anything like that before. And they WILL crash more than one prototype before they get it done and therefore they would be wise to do that with a cheaper version and one they earn money with by delivering a payload before it has to land again. Just as they did it with Falcon 9.

And Elon will know that very well and will in a year or two nail another rung onto that ladder to Mars because he will have to, as much as he wants to get there in one step. Give me an upvote then if you like.

BFS isn't completely unprecedented. In terms of dry mass, on-board propulsion, on-board crew cabin, payload section, flaps, dimensions, significant lift, and, of course reentry, ITS Spaceship is really most like Shuttle Orbiter.
Title: Re: ITS Development Updates and Discussion Thread
Post by: Robotbeat on 04/06/2017 03:03 am
Also, who says that SpaceX doesn't have intermediate development vehicles, aka Grasshopper? Why do we assume that the people who just did a landing on a drone ship using a rocket that had been to space twice are too stupid to have a workable development approach?
Title: Re: ITS Development Updates and Discussion Thread
Post by: guckyfan on 04/06/2017 08:15 am

Hey, this "half the mass fraction" includes sitting on Mars fully fuelled and launching from it without a launchpad. The legs holding up nearly 2000 tons of fuel there alone will be a true challenge within that mass fraction

Source? How do you know that they not use some kind of jack stands to support the liftoff weight, get it a meter or two more off the ground and at least place some flame deflectors?
Title: Re: ITS Development Updates and Discussion Thread
Post by: Robotbeat on 04/06/2017 12:32 pm
I think SpaceX attempting upper stage recovery on the Falcon Heavy demo is a way to buy down risk and provide experience with reentry of a large cylindrical vehicle in order to feed into the ITS design. They'll probably add some sort of rudimentary body flaps and /maybe/ some landing thrusters.

The only other big question mark (other than issues of raw scale) for the ITS stack is the launch cradle, which I expect to be resolved by some sort of Grasshopper-like subscale testing.

There are other things which will need some work, like in-orbit refueling, the pressurization system, and getting Raptor to work at full pressure which will need work, too, but I'm pretty confident those will be resolved with similar tests. If you have the full reuse part working, then the inflight refueling can be done without needing an even partially expendable launch. (And, of course, that demo flight of Falcon Heavy will be hopefully fully reusable, too.)

By the way, it's possible SpaceX has been trolling us a bit and Falcon Heavy will be demo launching with a Raptor-based subscale version of the BFS. Unlikely but possible.
Title: Re: ITS Development Updates and Discussion Thread
Post by: rpapo on 04/06/2017 12:58 pm
By the way, it's possible SpaceX has been trolling us a bit and Falcon Heavy will be demo launching with a Raptor-based subscale version of the BFS. Unlikely but possible.
Very unlikely.  AFAIK, they haven't moved to full scale testing of the Raptor yet, let alone built a prototype (even subscale) BFS to mount it on.

What has been physically done so far for BFS, even in prototyping?  AFAIK, they have a half-scale Raptor, and had a full scale composite fuel tank (RIP).  What else has been built?
Title: Re: ITS Development Updates and Discussion Thread
Post by: envy887 on 04/06/2017 01:38 pm
By the way, it's possible SpaceX has been trolling us a bit and Falcon Heavy will be demo launching with a Raptor-based subscale version of the BFS. Unlikely but possible.
Very unlikely.  AFAIK, they haven't moved to full scale testing of the Raptor yet, let alone built a prototype (even subscale) BFS to mount it on.

What has been physically done so far for BFS, even in prototyping?  AFAIK, they have a half-scale Raptor, and had a full scale composite fuel tank (RIP).  What else has been built?

Nothing, that we know of. But we didn't know a Raptor had been built until Shotwell announced that it had shipped to McGregor for test firing. And we didn't know about the tank until the IAC announcement.

It's quite possible, even probable, that they have built a lot more hardware in the last 8 months.
Title: Re: ITS Development Updates and Discussion Thread
Post by: Nathan2go on 04/06/2017 01:43 pm
...
By the way, it's possible SpaceX has been trolling us a bit and Falcon Heavy will be demo launching with a Raptor-based subscale version of the BFS. Unlikely but possible.
I see two question: 1) will Falcon Heavy upper stage use Raptor, and 2) will it use composite tanks.

I'm expecting the new Raptor engine to debut on the Falcon Heavy; if not on  the Heavy's first flight, then within the next year or so.  The thing about the Heavy is that Musk keeps saying all three first stages will fly back to the launch site. 

If they don't scale up the size (and thrust) of the Heavy's upper stage, then the upper stage has to be ignited at a much higher speed than on the Falcon 9, which means that the center first stage is going too fast and is too far downrange to return to the launch site.

If they just stretch the length of the metal upper stage, the whole stack gets pretty tall and skinny.  Maybe that's ok, or maybe it's better to make the bigger tank shorter and fatter (and composite).  I'm betting on a simple stretch.
Title: Re: ITS Development Updates and Discussion Thread
Post by: envy887 on 04/06/2017 01:54 pm
...
By the way, it's possible SpaceX has been trolling us a bit and Falcon Heavy will be demo launching with a Raptor-based subscale version of the BFS. Unlikely but possible.
I see two question: 1) will Falcon Heavy upper stage use Raptor, and 2) will it use composite tanks.

I'm expecting the new Raptor engine to debut on the Falcon Heavy; if not on  the Heavy's first flight, then within the next year or so.  The thing about the Heavy is that Musk keeps saying all three first stages will fly back to the launch site. 

If they don't scale up the size (and thrust) of the Heavy's upper stage, then the upper stage has to be ignited at a much higher speed than on the Falcon 9, which means that the center first stage is going too fast and is too far downrange to return to the launch site.

If they just stretch the length of the metal upper stage, the whole stack gets pretty tall and skinny.  Maybe that's ok, or maybe it's better to make the bigger tank shorter and fatter (and composite).  I'm betting on a simple stretch.

No, Raptor isn't required for FH 3-core RTLS. For the US to get 8t to GEO-1800 (quoted price $90M), it has to stage at ~2,500 m/s. The FH core can get to that staging velocity with some 100t of fuel remaining, enough to null the downrange component and boostback (80t), and still have 75 engine-seconds (20t) of fuel for entry and landing.

Raptor does allow for much easier booster recovery after launching larger payloads.
Title: Re: ITS Development Updates and Discussion Thread
Post by: mark_m on 04/06/2017 06:00 pm
Hey, this "half the mass fraction" includes sitting on Mars fully fuelled and launching from it without a launchpad. The legs holding up nearly 2000 tons of fuel there alone will be a true challenge within that mass fraction. This is not just a second stage that quietly dies once in orbit, it's a full space ship meant to be able to land on Mars, hold up against the other 92% in propellants while being tanked and then launch again from those legs on the sands of Mars and land on Earth.

Just curious, is that 2000 tons in Mars gravity?
Title: Re: ITS Development Updates and Discussion Thread
Post by: envy887 on 04/06/2017 06:11 pm
Hey, this "half the mass fraction" includes sitting on Mars fully fuelled and launching from it without a launchpad. The legs holding up nearly 2000 tons of fuel there alone will be a true challenge within that mass fraction. This is not just a second stage that quietly dies once in orbit, it's a full space ship meant to be able to land on Mars, hold up against the other 92% in propellants while being tanked and then launch again from those legs on the sands of Mars and land on Earth.

Just curious, is that 2000 tons in Mars gravity?

2000 tonnes is 2000 tonnes no matter where you put it.

But it would only weigh 7.4 MN, instead of 19.6 MN like it would on Earth.
Title: Re: ITS Development Updates and Discussion Thread
Post by: guckyfan on 04/06/2017 06:54 pm
You need to accelerate the mass. But the legs would only have to support the weight, which is only 38% of that on earth.
Title: Re: ITS Development Updates and Discussion Thread
Post by: mark_m on 04/06/2017 09:20 pm
Hey, this "half the mass fraction" includes sitting on Mars fully fuelled and launching from it without a launchpad. The legs holding up nearly 2000 tons of fuel there alone will be a true challenge within that mass fraction. This is not just a second stage that quietly dies once in orbit, it's a full space ship meant to be able to land on Mars, hold up against the other 92% in propellants while being tanked and then launch again from those legs on the sands of Mars and land on Earth.

Just curious, is that 2000 tons in Mars gravity?

2000 tonnes is 2000 tonnes no matter where you put it.

But it would only weigh 7.4 MN, instead of 19.6 MN like it would on Earth.

Hmmm, but, unlike tonnes or metric tons, 2000 tons isn't 2000 tons everywhere, at least not in common US usage. And that would make a difference, since the legs would only have to support a full fuel load on Mars, not on Earth, and it would be the force, not the mass, that would be relevant.
Title: Re: ITS Development Updates and Discussion Thread
Post by: envy887 on 04/06/2017 10:14 pm
Hey, this "half the mass fraction" includes sitting on Mars fully fuelled and launching from it without a launchpad. The legs holding up nearly 2000 tons of fuel there alone will be a true challenge within that mass fraction. This is not just a second stage that quietly dies once in orbit, it's a full space ship meant to be able to land on Mars, hold up against the other 92% in propellants while being tanked and then launch again from those legs on the sands of Mars and land on Earth.

Just curious, is that 2000 tons in Mars gravity?

2000 tonnes is 2000 tonnes no matter where you put it.

But it would only weigh 7.4 MN, instead of 19.6 MN like it would on Earth.

Hmmm, but, unlike tonnes or metric tons, 2000 tons isn't 2000 tons everywhere, at least not in common US usage. And that would make a difference, since the legs would only have to support a full fuel load on Mars, not on Earth, and it would be the force, not the mass, that would be relevant.

A ton in this context is a unit of mass, with the corresponding unit of force being the ton-force, equal to the weight of a ton under standard gravity. So, yes, a ton is also a ton no matter where you put it, but also yes, it's common usage to say tons when meaning tons-force.

Unit pedantry aside, the dynamic load during landing is almost certainly the critical factor here. Dynamic accelerations can easily exceed several g if the hoverslam just barely misses zeroing altitude and velocity simultaneously. So the 450 ton landing vehicle could potentially generate well over 1000 tons-force of momentary load on the legs, considerably more than the 770 tons-force of a static 2100 ton vehicle under .37 g.
Title: Re: ITS Development Updates and Discussion Thread
Post by: Robotbeat on 04/06/2017 11:48 pm
By the way, it's possible SpaceX has been trolling us a bit and Falcon Heavy will be demo launching with a Raptor-based subscale version of the BFS. Unlikely but possible.
Very unlikely.  AFAIK, they haven't moved to full scale testing of the Raptor yet, let alone built a prototype (even subscale) BFS to mount it on.

What has been physically done so far for BFS, even in prototyping?  AFAIK, they have a half-scale Raptor, and had a full scale composite fuel tank (RIP).  What else has been built?
I don't know what SpaceX will be doing.
But I don't think you would expect to know everything SpaceX is building before it's announced. SpaceX has become relatively secretive on secret projects.

Second: I question the "subscale" claim. Was it actually subscale in physical dimensions or operated at lower pressure and thus lower thrust? The latter seems much more likely to me, as the primary hard thing about Raptor isn't its physical dimensions but the very high pressures. And Raptor will need to be able to throttle down anyway. Also, "subscale," although often repeated, has not been sufficiently well-sourced to convince me.


But anyway. They could still use the upper stage as a subscale version of BFS even if they use neither Raptor nor carbon fiber tanks. A similar outer mold line, legs, control surfaces, and reentry/flight regime as BFS would go a very long way in validating the design assumptions & requirements of BFS. It could operate much as the F9 upper stage in the classic reuse video, using Superdracos to land, but modified with a bit different outermoldline, BFS-style legs and body flaps.

Or it could dispense with the legs and the Superdracos and just do parachute-splashdown recovery while still validating a BFS-like reentry path. After all, the F9 2nd stage reuse video shows a system very similar to BFS.
Title: Re: ITS Development Updates and Discussion Thread
Post by: Nathan2go on 04/07/2017 04:14 am
No, Raptor isn't required for FH 3-core RTLS. For the US to get 8t to GEO-1800 (quoted price $90M), it has to stage at ~2,500 m/s. The FH core can get to that staging velocity with some 100t of fuel remaining, enough to null the downrange component and boostback (80t), and still have 75 engine-seconds (20t) of fuel for entry and landing.

Raptor does allow for much easier booster recovery after launching larger payloads.

Good point.  8 tons to GTO is in the ballpark with the Atlas V 551's 8.9 ton.  It does fall short though, compared to the Delta IV Heavy's 13.8 tons, an expected New Glenn 13 tons, and an expendable Falcon Heavy 22 tons.
Title: Re: ITS Development Updates and Discussion Thread
Post by: OneSpeed on 04/07/2017 04:25 am
... I question the "subscale" claim. Was it actually subscale in physical dimensions or operated at lower pressure and thus lower thrust? The latter seems much more likely to me, as the primary hard thing about Raptor isn't its physical dimensions but the very high pressures. And Raptor will need to be able to throttle down anyway. Also, "subscale," although often repeated, has not been sufficiently well-sourced to convince me.

Let's assume the guardrail is the standard 42" in height. If the plume is about the same diameter as the test raptor nozzle, I measure it as 32" or 0.81mØ. From the ITS Mexico renderings, I measure the BFR engine as 1.51mØ and the BFS as 1.78mØ. So, even allowing for parallax errors, about half scale.
Title: Re: ITS Development Updates and Discussion Thread
Post by: Robotbeat on 04/07/2017 08:43 am
Not convinced. As far as you know, they just didn't put the full nozzle on it.
Title: Re: ITS Development Updates and Discussion Thread
Post by: MikeAtkinson on 04/07/2017 08:57 am
Not convinced. As far as you know, they just didn't put the full nozzle on it.

Neither am I. Smaller nozzle might mean lower thrust, smaller size, both or neither. I think the most likely explanation is full size engine (other than nozzle), but lower thrust. I don't see the point of SpaceX producing an engine that has smaller dimensions, unless they had a use for that smaller engine, as they would still have to redo the design and manufacturing at full size.
Title: Re: ITS Development Updates and Discussion Thread
Post by: OneSpeed on 04/07/2017 10:59 am
Not convinced. As far as you know, they just didn't put the full nozzle on it.

Then the plume would have kept expanding.

... I don't see the point of SpaceX producing an engine that has smaller dimensions, unless they had a use for that smaller engine, as they would still have to redo the design and manufacturing at full size.

It might be useful on a half scale BFS ;)
Title: Re: ITS Development Updates and Discussion Thread
Post by: Robotbeat on 04/07/2017 12:22 pm
Not convinced. As far as you know, they just didn't put the full nozzle on it.

Then the plume would have kept expanding.
...
Not if it was operated at lower chamber pressure, which again I think is most likely.
Title: Re: ITS Development Updates and Discussion Thread
Post by: envy887 on 04/07/2017 01:22 pm
Is there a higher-resolution version of the attached image available (in L2 or anywhere)?

The surest way to tell if it's subscale or not is by throat diameter. In this image it looks full-scale, but it's hard to tell for sure at this resolution.
Title: Re: ITS Development Updates and Discussion Thread
Post by: livingjw on 04/07/2017 02:40 pm
This is the best one that I have ever seen. I originally thought it was full size but after seeing the nozzle, I now believe it is not a full size engine.
Title: Re: ITS Development Updates and Discussion Thread
Post by: JamesH65 on 04/07/2017 04:26 pm
In order to use a Rapter, the US will need modifications to the GSE to provide the new fuel to the stage, which means mods to the TEL, and also more storage tanks at the launch site for the Methane.

None of this has been seen and would take some months to build.

I seriously doubt there will be a raptor upper stage in the near future if for no other reason than the lack of any modification to the launch site.
Title: Re: ITS Development Updates and Discussion Thread
Post by: RotoSequence on 04/08/2017 10:33 pm
If SpaceX can't make the multi-piece composite tanks strong enough at the seams, is it possible to build and utilize an Autoclave that would exclusively fit, seal, and set the seams of the composite ITS tanks?
Title: Re: ITS Development Updates and Discussion Thread
Post by: Robotbeat on 04/09/2017 12:36 am
In order to use a Rapter, the US will need modifications to the GSE to provide the new fuel to the stage, which means mods to the TEL, and also more storage tanks at the launch site for the Methane.

None of this has been seen and would take some months to build.

I seriously doubt there will be a raptor upper stage in the near future if for no other reason than the lack of any modification to the launch site.
...the launch site will need modifications for Falcon Heavy anyway and Falcon Heavy's inaugural launch is many months away.

Again, as I said at first, it's unlikely but not impossible. And anyway, the Falcon Heavy reusable upper stage could operate as a subscale BFS test in every way but propulsion (Raptor and new thrusters vs Merlin and Superdracos) and structure (carbon fiber vs aluminum). That's basically what is shown in the famous Falcon 9 reuse video (except I'd expect more of a side-reentry and body flaps). If they land the FH reusable upper stage propulsively, it'll essentially be a pathfinder for ITS BFS in any case.
Title: Re: ITS Development Updates and Discussion Thread
Post by: tdperk on 04/09/2017 01:43 am
If SpaceX can't make the multi-piece composite tanks strong enough at the seams, is it possible to build and utilize an Autoclave that would exclusively fit, seal, and set the seams of the composite ITS tanks?

Yes.

It's just bigger oven.
Title: Re: ITS Development Updates and Discussion Thread
Post by: Oersted on 04/09/2017 12:03 pm
I had a thought which doesn't fit into the above discussion.

Over its various development iterations the Falcon 9 and its Merlin engines have amassed huge efficiency increases, so that the payload now is much bigger than originally intended.

I wonder if SpaceX is "factoring in" similar developments for the BFR, the ITS and the Raptor engines. The Falcon 9 second stage could quite easily be lengthened. It won't be so straightforward to "lengthen" the ITS given its more complex mold line, yet it would also be sad to have a non-optimized launch system due to not envisaging the final efficiency of the Raptors.

So, how to design your way out of the problem?

Maybe design the whole stack for "125%" efficiency Raptors and then - in the early years when you only have "95%" efficiency Raptors available - fly it with a smaller payload. Certainly that would be better than ending up in the opposite situation, where you would only need 35 instead of 42 Raptors in the first stage.

You could always say "just add more payload" but the ITS should be optimally configured for any given final payload, and not "crammed to the hilt".

Any thoughts on this? 
Title: Re: ITS Development Updates and Discussion Thread
Post by: guckyfan on 04/09/2017 12:29 pm
I have stumbled over one item in the post SES-10 press conference when Elon Musk was asked about the future plans for ITS and if the first mission would be unmanned.

His reply was

Quote
yeah the first ones will be uncrewed.

I saw it first in the reddit transcript but watched the press conference again to confirm. He clearly said "the first ones".

This implies several unmanned landings before the first manned flight. I guess this could mean more than one ITS on the first launch window or the second launch window has one unmanned landing first and then the manned ship.

Or I am reading just too much into his use of the plural. But I think he let slip one detail of the coming announcement.
Title: Re: ITS Development Updates and Discussion Thread
Post by: FishInferno on 04/09/2017 01:02 pm
I have stumbled over one item in the post SES-10 press conference when Elon Musk was asked about the future plans for ITS and if the first mission would be unmanned.

His reply was

Quote
yeah the first ones will be uncrewed.

I saw it first in the reddit transcript but watched the press conference again to confirm. He clearly said "the first ones".

This implies several unmanned landings before the first manned flight. I guess this could mean more than one ITS on the first launch window or the second launch window has one unmanned landing first and then the manned ship.

Or I am reading just too much into his use of the plural. But I think he let slip one detail of the coming announcement.

"The first ones" could include LEO tests and the like, but I would not be surprised if they do send multiple ships to Mars before any humans go.
Title: Re: ITS Development Updates and Discussion Thread
Post by: MikeAtkinson on 04/09/2017 01:07 pm
Or I am reading just too much into his use of the plural. But I think he let slip one detail of the coming announcement.

Probably reading too much into the plural. There were to be extensive tests in LEO (and lunar missions?) in the old plans, probably also some short unmanned missions in the new plans (whatever they are).

So multiple missions before the first one to Mars, then possibly multiple missions to Mars before the first manned one.
Title: Re: ITS Development Updates and Discussion Thread
Post by: guckyfan on 04/09/2017 02:11 pm
Or I am reading just too much into his use of the plural. But I think he let slip one detail of the coming announcement.

Probably reading too much into the plural. There were to be extensive tests in LEO (and lunar missions?) in the old plans, probably also some short unmanned missions in the new plans (whatever they are).

So multiple missions before the first one to Mars, then possibly multiple missions to Mars before the first manned one.

Well, obviously there needs to be a test program in cislunar space. They may need to do more than the old timetable gave time for.

I see Elons statement as Mars related, so more than 1 unmanned landing, before the first manned mission seems likely.
Title: Re: ITS Development Updates and Discussion Thread
Post by: MP99 on 04/09/2017 03:09 pm


Outfitted as a space station on the ground, the ITS ship would make a fine medium size space station. It could be deorbited after a few years for refurbishment and updating with new equipment and experiments. Could have more than one in various orbits.

With refuelling, this ITS space station could self ferry anywhere in cis-lunar space or beyond.

Advantage for SpaceX, is that it maintains the highly profitable commercial cargo and crew business, and it develops an entirely new business in space stations.

I am pretty sure this has been covered before. ITS would not make a great space station for all the reasons that mobile homes don't make great houses. Far too much compromise since the design criteria have only a little overlap.

I suspect that a better analogy here is "for all the reasons that yaghts don't make great houses". Maybe a small superyaght, since the masses (and volumes?) are more comparable.

Cheers, Martin
Title: Re: ITS Development Updates and Discussion Thread
Post by: MikeAtkinson on 04/09/2017 03:56 pm


Outfitted as a space station on the ground, the ITS ship would make a fine medium size space station. It could be deorbited after a few years for refurbishment and updating with new equipment and experiments. Could have more than one in various orbits.

With refuelling, this ITS space station could self ferry anywhere in cis-lunar space or beyond.

Advantage for SpaceX, is that it maintains the highly profitable commercial cargo and crew business, and it develops an entirely new business in space stations.

I am pretty sure this has been covered before. ITS would not make a great space station for all the reasons that mobile homes don't make great houses. Far too much compromise since the design criteria have only a little overlap.

I suspect that a better analogy here is "for all the reasons that yaghts don't make great houses". Maybe a small superyaght, since the masses (and volumes?) are more comparable.

Cheers, Martin

But small/medium size boats make great labs for oceanography. Which is a closer analogy. I'm not suggesting that it be used as a house, rather than as a  replacement for the ISS. It might be even better than the ISS for research, because it could be landed every few years and upgraded and can be adapted to changing research needs much more easily.
Title: Re: ITS Development Updates and Discussion Thread
Post by: vandersons on 04/17/2017 09:19 am
Saw this comparison in Instagram today. That thing is going to be one heck of a beast! The ISS looks almost small in that rendering.

https://www.instagram.com/p/BS9m_T2FZk5/

P.S. If this has been posted before please remove, hadn't seen it myself before.
Title: Re: ITS Development Updates and Discussion Thread
Post by: testguy on 04/18/2017 01:22 am
Yes I know Elon has stated that the Spacex web would update the ITS plan forward in about a month.  However, if there is any chance in hell of meeting his early mission plans, shouldn't we have learned by now of his plans for fabrication of the launch vehicle and space craft. Specifically what land will be used at the Cape for the factory, what the factory will look like, and how the assemblies will be transported to 39A. 

Look at the progress Blue has made on there factory already.  Blues schedule for 2020 appears realistic from a facilities viewpoint.  I am a Spacex supporter, and not trying to be a naysayer,  just would like to feel more confident of the plan.
Title: Re: ITS Development Updates and Discussion Thread
Post by: testguy on 04/18/2017 01:34 am
We know that 39A will be used for early ITS's flights.  Has there been any discussion on how modify the launch site without taking it down for a long period of time.  I was thing that a pad could be constructed ajacent to the existing pad.  That way Falcon 9  and  FH could continue to fly from 39A, although they would slow down construction. 

It would also be interesting to see over pressure isobars for 39A in the event of a catastrophic ITS event.  What would it do to the existing Hif? 

Would appreciate feedback on both thoughts

Title: Re: ITS Development Updates and Discussion Thread
Post by: TomH on 04/18/2017 09:50 am
The Falcon 9 second stage could quite easily be lengthened.

From what I've read in other threads, F9 is as long as it can get in relation to its width due to bending loads. If the S2 were lengthened, the S1 would have to be shortened. Again, this is what I have read here by some who know much more than I.
Title: Re: ITS Development Updates and Discussion Thread
Post by: RoboGoofers on 04/18/2017 04:01 pm
Yes I know Elon has stated that the Spacex web would update the ITS plan forward in about a month.  However, if there is any chance in hell of meeting his early mission plans, shouldn't we have learned by now of his plans for fabrication of the launch vehicle and space craft. Specifically what land will be used at the Cape for the factory, what the factory will look like, and how the assemblies will be transported to 39A. 

Look at the progress Blue has made on there factory already.  Blues schedule for 2020 appears realistic from a facilities viewpoint.  I am a Spacex supporter, and not trying to be a naysayer,  just would like to feel more confident of the plan.

It's still early days. They're still testing their manufacturing processes for the CF tanks, if the test tank is anything to go by. They think the ITS tanks are possible, and they think Raptor is possible, but are obviously not ready to break ground on a factory yet.
Title: Re: ITS Development Updates and Discussion Thread
Post by: testguy on 04/18/2017 06:22 pm
I agree it is early but not too early.  They must be beyond an internal PDR, otherwise Elon would not have given the presentation last December.  Im sure would have expected the Raptor and composite tanks to have been beyond pie in the sky.  Good project management should have included back up plans so my guess is the should have a factory concept by now, certainly including square footage and enough information to go forward with an environmental plan. To do that the real estate has to be identified and we have not learned where that is.  That is why I'm concerned that the proposed schedule is slipping.  I hope not but would like to see more or any information on the factory.  I keep going back to the progress we are seeing at Blue.

it would be great if Spacex management took this as throwing brown the gauntlet.





Title: Re: ITS Development Updates and Discussion Thread
Post by: chalz on 04/18/2017 06:46 pm
I agree it is early but not too early.  They must be beyond an internal PDR, otherwise Elon would not have given the presentation last December.  Im sure would have expected the Raptor and composite tanks to have been beyond pie in the sky.  Good project management should have included back up plans so my guess is the should have a factory concept by now, certainly including square footage and enough information to go forward with an environmental plan. To do that the real estate has to be identified and we have not learned where that is.  That is why I'm concerned that the proposed schedule is slipping.  I hope not but would like to see more or any information on the factory.  I keep going back to the progress we are seeing at Blue.

it would be great if Spacex management took this as throwing brown the gauntlet.
The problem is surely lack of money. They are a solvent company but have other commitments for that cash - Crew Dragon and final F9 iteration being high on the list. The estimate of ITS development was $10bn, that is why they are pursuing the satellite constellation, it is the only thing that could conceivably produce the money. Until that happens or an angel investor arrives the only news is going to be plans and iterations on existing work.
Title: Re: ITS Development Updates and Discussion Thread
Post by: Falcon H on 04/19/2017 03:49 pm
I've heard some speculation about SpaceX using ITS to launch it's satellite constellation. I'm a little out of the loop here...has SpaceX ever hinted at a cargo variant?  I imagine this would require be an entirely new upper stage, having little in common with the passenger and tanker variants.
Title: Re: ITS Development Updates and Discussion Thread
Post by: RonM on 04/19/2017 04:04 pm
I've heard some speculation about SpaceX using ITS to launch it's satellite constellation. I'm a little out of the loop here...has SpaceX ever hinted at a cargo variant?  I imagine this would require be an entirely new upper stage, having little in common with the passenger and tanker variants.

No, SpaceX has not hinted at a cargo variant. It's pure speculation, but technically feasible. A cargo variant would not need an entirely new spacecraft. There's plenty of room in the ITS ship design for cargo.
Title: Re: ITS Development Updates and Discussion Thread
Post by: dror on 04/19/2017 04:30 pm
Yes I know Elon has stated that the Spacex web would update the ITS plan forward in about a month.  However, if there is any chance in hell of meeting his early mission plans, shouldn't we have learned by now of his plans for fabrication of the launch vehicle and space craft. Specifically what land will be used at the Cape for the factory, what the factory will look like, and how the assemblies will be transported to 39A. 

Look at the progress Blue has made on there factory already.  Blues schedule for 2020 appears realistic from a facilities viewpoint.  I am a Spacex supporter, and not trying to be a naysayer,  just would like to feel more confident of the plan.

They're too busy stealing underpants
Title: Re: ITS Development Updates and Discussion Thread
Post by: Navier–Stokes on 04/29/2017 06:33 pm
A brief mention of ITS from Elon Musk at TED 2017:
Quote from: http://blog.ted.com/what-will-the-future-look-like-elon-musk-speaks-at-ted2017/
Showing plans for a massive rocket that’s the size of a 40-story building, Musk talks about what it’ll take to get to Mars. “The thrust level for this configuration is about four times the thrust of a Saturn V moon rocket,” the biggest rocket humanity has ever created, he says. “In units of 747s, this would be the thrust equivalent of 120 747s with all engines blazing.” The rocket is so massive that it could take a fully-loaded 747 as cargo. While it may seem large now, “future spacecraft will make this look like a rowboat,” Musk says.

And when can we can hope to see it? Musk thinks the Interplanetary Transport System SpaceX revealed earlier this year will take 8-10 years to build. “Our internal targets are more aggressive,” he says.

“There have to be reasons that you get up in the morning and you want to live. Why do you want to live? What’s the point? What inspires you? What do you love about the future? If the future does not include being out there among the stars and being a multi-planet species, I find that incredibly depressing,” Musk says.
Note: emphasis mine.
Title: Re: ITS Development Updates and Discussion Thread
Post by: AncientU on 04/29/2017 06:44 pm
Interplanetary Transport System includes the propellant ISRU on Mars and refueling capability both on Mars and Earth orbit.  Musk says he hates to call it a system -- everything is a system -- but when it includes ISRU, it is more than a rocket. (Sorry for the paraphrase, cannot locate the exact quote.)

This statement you've bolded does not mean we'll see the first BFR launch in 8-10 years.  The 6-year target is first launch to Mars (in 2022) which was called 'optimistic' by EM.
Title: Re: ITS Development Updates and Discussion Thread
Post by: AncientU on 04/29/2017 06:55 pm
Yes I know Elon has stated that the Spacex web would update the ITS plan forward in about a month.  However, if there is any chance in hell of meeting his early mission plans, shouldn't we have learned by now of his plans for fabrication of the launch vehicle and space craft. Specifically what land will be used at the Cape for the factory, what the factory will look like, and how the assemblies will be transported to 39A. 

Look at the progress Blue has made on there factory already.  Blues schedule for 2020 appears realistic from a facilities viewpoint.  I am a Spacex supporter, and not trying to be a naysayer,  just would like to feel more confident of the plan.

Patience Young Grasshopper...
I want to know, too, but us not knowing doesn't equate to there being no plans.
Title: Re: ITS Development Updates and Discussion Thread
Post by: testguy on 04/29/2017 09:19 pm
By the way, I'll bet you a beer I have witnessed more sunsets than you.  That is probably the reason for any impatients.  Liked the grasshopper comment though, I too have used it on past protégés.

Ha, just checked I was correct.  Got four years on you.  How is this for a meaningless post?  I swear I will stop.


 
Title: Re: ITS Development Updates and Discussion Thread
Post by: HMXHMX on 04/29/2017 09:28 pm
I agree it is early but not too early.  They must be beyond an internal PDR, otherwise Elon would not have given the presentation last December.  Im sure would have expected the Raptor and composite tanks to have been beyond pie in the sky.  Good project management should have included back up plans so my guess is the should have a factory concept by now, certainly including square footage and enough information to go forward with an environmental plan. To do that the real estate has to be identified and we have not learned where that is.  That is why I'm concerned that the proposed schedule is slipping.  I hope not but would like to see more or any information on the factory.  I keep going back to the progress we are seeing at Blue.

it would be great if Spacex management took this as throwing brown the gauntlet.
The problem is surely lack of money. They are a solvent company but have other commitments for that cash - Crew Dragon and final F9 iteration being high on the list. The estimate of ITS development was $10bn, that is why they are pursuing the satellite constellation, it is the only thing that could conceivably produce the money. Until that happens or an angel investor arrives the only news is going to be plans and iterations on existing work.


They could always do a private equity raise.
Title: Re: ITS Development Updates and Discussion Thread
Post by: Space Ghost 1962 on 04/29/2017 11:57 pm
I agree it is early but not too early.  They must be beyond an internal PDR, otherwise Elon would not have given the presentation last December.  Im sure would have expected the Raptor and composite tanks to have been beyond pie in the sky.  Good project management should have included back up plans so my guess is the should have a factory concept by now, certainly including square footage and enough information to go forward with an environmental plan. To do that the real estate has to be identified and we have not learned where that is.  That is why I'm concerned that the proposed schedule is slipping.  I hope not but would like to see more or any information on the factory.  I keep going back to the progress we are seeing at Blue.

it would be great if Spacex management took this as throwing brown the gauntlet.
The problem is surely lack of money. They are a solvent company but have other commitments for that cash - Crew Dragon and final F9 iteration being high on the list. The estimate of ITS development was $10bn, that is why they are pursuing the satellite constellation, it is the only thing that could conceivably produce the money. Until that happens or an angel investor arrives the only news is going to be plans and iterations on existing work.


They could always do a private equity raise.

Unlikely given the timing on returns being many decades.
Title: Re: ITS Development Updates and Discussion Thread
Post by: pippin on 04/30/2017 01:38 am

This statement you've bolded does not mean we'll see the first BFR launch in 8-10 years.  The 6-year target is first launch to Mars (in 2022) which was called 'optimistic' by EM.
Yes, because you do of course have to take the Elon time dilation factor into account meaning in normal years it's likely going to be something like 12-15
Title: Re: ITS Development Updates and Discussion Thread
Post by: HMXHMX on 04/30/2017 03:10 am
I agree it is early but not too early.  They must be beyond an internal PDR, otherwise Elon would not have given the presentation last December.  Im sure would have expected the Raptor and composite tanks to have been beyond pie in the sky.  Good project management should have included back up plans so my guess is the should have a factory concept by now, certainly including square footage and enough information to go forward with an environmental plan. To do that the real estate has to be identified and we have not learned where that is.  That is why I'm concerned that the proposed schedule is slipping.  I hope not but would like to see more or any information on the factory.  I keep going back to the progress we are seeing at Blue.

it would be great if Spacex management took this as throwing brown the gauntlet.
The problem is surely lack of money. They are a solvent company but have other commitments for that cash - Crew Dragon and final F9 iteration being high on the list. The estimate of ITS development was $10bn, that is why they are pursuing the satellite constellation, it is the only thing that could conceivably produce the money. Until that happens or an angel investor arrives the only news is going to be plans and iterations on existing work.


They could always do a private equity raise.

Unlikely given the timing on returns being many decades.

Would you like to make a friendly wager on that?  :)
Title: Re: ITS Development Updates and Discussion Thread
Post by: Space Ghost 1962 on 04/30/2017 04:47 am
I agree it is early but not too early.  They must be beyond an internal PDR, otherwise Elon would not have given the presentation last December.  Im sure would have expected the Raptor and composite tanks to have been beyond pie in the sky.  Good project management should have included back up plans so my guess is the should have a factory concept by now, certainly including square footage and enough information to go forward with an environmental plan. To do that the real estate has to be identified and we have not learned where that is.  That is why I'm concerned that the proposed schedule is slipping.  I hope not but would like to see more or any information on the factory.  I keep going back to the progress we are seeing at Blue.

it would be great if Spacex management took this as throwing brown the gauntlet.
The problem is surely lack of money. They are a solvent company but have other commitments for that cash - Crew Dragon and final F9 iteration being high on the list. The estimate of ITS development was $10bn, that is why they are pursuing the satellite constellation, it is the only thing that could conceivably produce the money. Until that happens or an angel investor arrives the only news is going to be plans and iterations on existing work.


They could always do a private equity raise.

Unlikely given the timing on returns being many decades.

Would you like to make a friendly wager on that?  :)

No, unless the terms include the entire absence of any government contract or other funds.

Yes, I know of the efforts underway to begin this too. However, there are other necessary components for the full realization of this to happen.

So its unfair to characterize this solely in terms of private equity "bought and sold". And unwise to bet on anything this early in the process.
Title: Re: ITS Development Updates and Discussion Thread
Post by: AncientU on 04/30/2017 11:02 am

This statement you've bolded does not mean we'll see the first BFR launch in 8-10 years.  The 6-year target is first launch to Mars (in 2022) which was called 'optimistic' by EM.
Yes, because you do of course have to take the Elon time dilation factor into account meaning in normal years it's likely going to be something like 12-15

The ConnX was proposed about two years ago with initial operability forecast for 2020.  That will be a good calibrator for the current time dilation factor.  Do not assume it is a constant.

Note: 12-15 years to build a 5x SLS-1B carbon composite booster that is reusable and sports 42 of the most advanced rocket engine ever built, a nine engine, two million kilogram spaceship with several times the habitable volume of the ISS that can land either on Mars or Earth, on-orbit refueling capability, and ISRU on Mars with refueling capability -- all for the price and schedule of the Orion 'exploration' capsule -- would be fine with me.
Title: Re: ITS Development Updates and Discussion Thread
Post by: pippin on 04/30/2017 05:02 pm
Definitely. Never wanted to suggest what SpaceX does isn't incredible.
But there are enough amazing peoples here who take SpaceX's schedules and then seem to expect them to do stuff even faster which isn't particularly realistic.
Title: Re: ITS Development Updates and Discussion Thread
Post by: FutureSpaceTourist on 05/01/2017 12:49 pm
Not surprisingly Elon's timeline for IFS update has moved right:

Quote
I really enjoyed watching it! Can we expect an update on the ITS soon? Curious to learn more about the architecture and new developments.

https://twitter.com/voltzcoreaudio/status/858905881445974017 (https://twitter.com/voltzcoreaudio/status/858905881445974017)

Quote
Yeah, will probably publish an update in six weeks or so

https://twitter.com/elonmusk/status/858908487018926080 (https://twitter.com/elonmusk/status/858908487018926080)
Title: Re: ITS Development Updates and Discussion Thread
Post by: spacenut on 05/01/2017 01:28 pm
Would the cost of a mini-ITS system have been less than the estimated 8-10 years?  Say 4-5 years.  Still get you to Mars, but with more launches.  Say a 12m booster but shorter and fewer engines.  Also a mini-ITS on top.  Later a stretched booster with more engines and a full sized ITS on top.  Again, a smaller system using reusable Mars landers, LEO refueling, and SEP tugs to take a lot of the goods and equipment to Mars more slowly but less expensively.  Use the booster to launch satellites in the mean time for revenue.  During the 18 month synod when Mars is further away, use that time with the smaller booster to launch SEP tugs, fuel, and cargo for a trip to Mars orbit.  Launch Mini-ITS to Mars during the 6 month synods with a skeleton crew to dock and off load supplies from the SEP tugs and land the equipment on Mars.  SEP tugs could then fly back to Earth, say an L2 station for reloading of supplies and propellant.  Eventually SEP tugs could be refueled with argon manufactured on Mars. 

Seems like a scaled down version would be more practical if getting NASA on board, along with some SEP tug manufacturers, in space habs, fuel and propellant depots, etc. 

Then again, maybe the huge ITS is the way to go, faster, less infrastructure docking events, etc. 

Also, when is a Mars 24 hour communication system to earth going to be installed?  Mars satellite system, maybe a laser system for faster communication times?  To me this is one of the first things needed. 
Title: Re: ITS Development Updates and Discussion Thread
Post by: Bynaus on 05/01/2017 01:50 pm
In the TED 2017 interview (https://www.ted.com/talks/elon_musk_the_future_we_re_building_and_boring), I noticed that Elon said of the ITS shown: "this configuration has about 4 times the thrust of the Saturn V" (at about 32:50). So, there might indeed not be a single (even less final) configuration of ITS, but several different configurations being developed and / or considered, perhaps optimized for different funding environments and other external constraints. So, I imagine, if SpaceX needs to do this on its own, the configuration might be different from the configuration which would be used if the US government would provide much of the funding, etc.
Title: Re: ITS Development Updates and Discussion Thread
Post by: docmordrid on 05/01/2017 02:27 pm
In the TED 2017 interview (https://www.ted.com/talks/elon_musk_the_future_we_re_building_and_boring), I noticed that Elon said of the ITS shown: "this configuration has about 4 times the thrust of the Saturn V" (at about 32:50).

Hmmmmm...

Saturn V: 35.1 MN
ITS (IAC slide): 128 MN

A 3.647:1 thrust ratio, not 4:1.

Has the ER40 Raptor been eating Wheaties? Or is Musk rounding off?
Title: Re: ITS Development Updates and Discussion Thread
Post by: sevenperforce on 05/01/2017 02:57 pm
Would the cost of a mini-ITS system have been less than the estimated 8-10 years?  Say 4-5 years.  Still get you to Mars, but with more launches.  Say a 12m booster but shorter and fewer engines.  Also a mini-ITS on top.
More likely that they'd do a mini-ITS sized to launch on F9 or FH.
Title: Re: ITS Development Updates and Discussion Thread
Post by: redliox on 05/01/2017 03:39 pm
Not surprisingly Elon's timeline for IFS update has moved right:

Quote
I really enjoyed watching it! Can we expect an update on the ITS soon? Curious to learn more about the architecture and new developments.

https://twitter.com/voltzcoreaudio/status/858905881445974017 (https://twitter.com/voltzcoreaudio/status/858905881445974017)

Quote
Yeah, will probably publish an update in six weeks or so

https://twitter.com/elonmusk/status/858908487018926080 (https://twitter.com/elonmusk/status/858908487018926080)

We're all itching for updates.  I wouldn't expect SpaceX to spill all its (ITS?) beans but it hasn't run as silently as Blue Origins' program either.

Specifically I'd like to learn which is going to be the chicken and the egg: the spaceship or the booster.  Neither is going to be a small effort and either would find a health niche in the launcher economy here on Earth.
Title: Re: ITS Development Updates and Discussion Thread
Post by: sevenperforce on 05/01/2017 04:44 pm
We're all itching for updates.  I wouldn't expect SpaceX to spill all its (ITS?) beans but it hasn't run as silently as Blue Origins' program either.

Specifically I'd like to learn which is going to be the chicken and the egg: the spaceship or the booster.  Neither is going to be a small effort and either would find a health niche in the launcher economy here on Earth.
Elon's presentation was very clear that the spaceship would come first, followed by the booster.

Falcon Heavy can, in theory, lift an upper stage with a gross mass of anything up to 400 tonnes or so; any development stage smaller than that will be able to launch on FH for testing.
Title: Re: ITS Development Updates and Discussion Thread
Post by: Toast on 05/01/2017 04:55 pm
Hmmmmm...

Saturn V: 35.1 MN
ITS (IAC slide): 128 MN

A 3.647:1 thrust ratio, not 4:1.

Has the ER40 Raptor been eating Wheaties? Or is Musk rounding off?

My guess is rounding off. Elon is speaking to an audience of (mostly) laymen, right before he made this comparison he compared it to 747's. It looked like he was doing a bit of the math in his head as he was saying it, so I'd imagine they're just pretty rough estimates.
Title: Re: ITS Development Updates and Discussion Thread
Post by: CriX on 05/01/2017 09:20 pm
Future spacecraft will make the ITS look like a row-boat, he says!  This is incredible.  ITS is rated for 100 passengers plus cargo.  Is he talking 1000 passengers ships?  Maybe this is what would be necessary to make space access affordable.   The Wright Brother's aircraft compared to a 747.  Maybe it is just the natural trajectory now that reusability has been "solved" or at least has crossed a major hurdle.   The Nina, Pinta, and Santa Maria compared to the Queen Elizabeth.  Crap I hope he gives us a peek at this monstrosity in 6 weeks.
Title: Re: ITS Development Updates and Discussion Thread
Post by: Kaputnik on 05/01/2017 09:40 pm
We're all itching for updates.  I wouldn't expect SpaceX to spill all its (ITS?) beans but it hasn't run as silently as Blue Origins' program either.

Specifically I'd like to learn which is going to be the chicken and the egg: the spaceship or the booster.  Neither is going to be a small effort and either would find a health niche in the launcher economy here on Earth.
Elon's presentation was very clear that the spaceship would come first, followed by the booster.

Falcon Heavy can, in theory, lift an upper stage with a gross mass of anything up to 400 tonnes or so; any development stage smaller than that will be able to launch on FH for testing.

But don't underestimate the effort, cost, and impact upon launch revenue from modifying FH and its facilities to carry a one-off test payload.
Title: Re: ITS Development Updates and Discussion Thread
Post by: docmordrid on 05/02/2017 04:27 am
If the Spaceship can self-launch from Mars who's to say for initial hop or suborital tests it couldn't be filled from trucks and do the same from a prepared plain pad?
Title: Re: ITS Development Updates and Discussion Thread
Post by: Bynaus on 05/02/2017 04:53 am
That row-boat comment also raised my eyebrow. But I think this does not necessarily apply to the rockets launched - you could have a massive, say, 10k people carrying, SEP or fusion powered ship built in orbit, which would then fly to its destination (say, Mars) and be serviced at both ends by ITS spaceships. Like in the ships of old, which were anchored off-shore and from which you had to take a rowing boat to get through the surf. The surf in this case being the orbit to surface distance, of course...
Title: Re: ITS Development Updates and Discussion Thread
Post by: corneliussulla on 05/02/2017 09:13 am
I thought I heard Musk say at the press conference after the first reusable launch that we could expect more details on ITS in a month or so. Well I think it's been about a month since that conference so maybe we will get a few more details soon.
Title: Re: ITS Development Updates and Discussion Thread
Post by: corneliussulla on 05/02/2017 09:23 am
Oops I just noticed that Elon has tweeted another 6 weeks...Elon time slippage effect. In fact we are actually moving backwards from the event as normal time moves forward ...LOL
Title: Re: ITS Development Updates and Discussion Thread
Post by: redliox on 05/02/2017 10:46 am
We're all itching for updates.  I wouldn't expect SpaceX to spill all its (ITS?) beans but it hasn't run as silently as Blue Origins' program either.

Specifically I'd like to learn which is going to be the chicken and the egg: the spaceship or the booster.  Neither is going to be a small effort and either would find a health niche in the launcher economy here on Earth.
Elon's presentation was very clear that the spaceship would come first, followed by the booster.

Is there any clear advantage in developing the spaceship as opposed to the booster first?  Obviously it's Elon's plan and reasoning, but that should be a question given to Mr. Musk I think when the chance arises.
Title: Re: ITS Development Updates and Discussion Thread
Post by: corneliussulla on 05/02/2017 11:30 am
Well I tend to think the spaceship is more complicated with all the systems required to support up to 100 people for 5 months plus and they have never done it before. BFR is really just an increase in scale from something they have already built. So there is more likely to be a learning curve on the spaceship.
Title: Re: ITS Development Updates and Discussion Thread
Post by: rsdavis9 on 05/02/2017 11:33 am
Wouldn't the mixture of SL raptors and MVAC raptors allow more flight regimes to be explored?
The BFS has the mixture of the 2 the BFR has just SL raptors. (Yes?)
Title: Re: ITS Development Updates and Discussion Thread
Post by: M.E.T. on 05/02/2017 12:15 pm
Well I tend to think the spaceship is more complicated with all the systems required to support up to 100 people for 5 months plus and they have never done it before. BFR is really just an increase in scale from something they have already built. So there is more likely to be a learning curve on the spaceship.

Yes, building the booster first makes even more sense if you build a pure cargo version of the ITS before the crew version, without the complexity of life support systems and crew quarters for a multi year Mars trip.
Title: Re: ITS Development Updates and Discussion Thread
Post by: dror on 05/02/2017 02:05 pm
Would the cost of a mini-ITS system have been less than the estimated 8-10 years?  Say 4-5 years.  Still get you to Mars, but with more launches.  Say a 12m booster but shorter and fewer engines. Also a mini-ITS on top.  Later a stretched booster with more engines and a full sized ITS on top.  Again, a smaller system using reusable Mars landers, LEO refueling, and SEP tugs to take a lot of the goods and equipment to Mars more slowly but less expensively.  Use the booster to launch satellites in the mean time for revenue.  During the 18 month synod when Mars is further away, use that time with the smaller booster to launch SEP tugs, fuel, and cargo for a trip to Mars orbit.  Launch Mini-ITS to Mars during the 6 month synods with a skeleton crew to dock and off load supplies from the SEP tugs and land the equipment on Mars.  SEP tugs could then fly back to Earth, say an L2 station for reloading of supplies and propellant.  Eventually SEP tugs could be refueled with argon manufactured on Mars. 

Seems like a scaled down version would be more practical if getting NASA on board, along with some SEP tug manufacturers, in space habs, fuel and propellant depots, etc. 


I think keeping the 12 m diameter looses most of the advantage of making an intermediate size vehicle.
It's basically the same vehicle, with all of the same difficulties.
IMO, an advantageous intermediate vehicle needs to be much smaller to be both compatible with existing infrastructure and near future needs, and be easier to develope the composite structure, which may be the biggest hurdle on the path.
Title: Re: ITS Development Updates and Discussion Thread
Post by: gospacex on 05/02/2017 02:17 pm
Would the cost of a mini-ITS system have been less than the estimated 8-10 years?  Say 4-5 years.  Still get you to Mars, but with more launches.  Say a 12m booster but shorter and fewer engines. Also a mini-ITS on top.  Later a stretched booster with more engines and a full sized ITS on top.  Again, a smaller system using reusable Mars landers, LEO refueling, and SEP tugs to take a lot of the goods and equipment to Mars more slowly but less expensively.  Use the booster to launch satellites in the mean time for revenue.  During the 18 month synod when Mars is further away, use that time with the smaller booster to launch SEP tugs, fuel, and cargo for a trip to Mars orbit.  Launch Mini-ITS to Mars during the 6 month synods with a skeleton crew to dock and off load supplies from the SEP tugs and land the equipment on Mars.  SEP tugs could then fly back to Earth, say an L2 station for reloading of supplies and propellant.  Eventually SEP tugs could be refueled with argon manufactured on Mars. 

Seems like a scaled down version would be more practical if getting NASA on board, along with some SEP tug manufacturers, in space habs, fuel and propellant depots, etc. 


I think keeping the 12 m diameter looses most of the advantage of making an intermediate size vehicle.
It's basically the same vehicle, with all of the same difficulties.
IMO, an advantageous intermediate vehicle needs to be much smaller to be both compatible with existing infrastructure and near future needs, and be easier to develope the composite structure, which may be the biggest hurdle on the path.

And you end up with three (count them!) diameters for your vehicles - F9, "intermediate size vehicle" and finally, 12m ITS.
Why?
Is there a huge market waiting to be served by this "intermediate size vehicle"? Empatically, no! F9/FH is more than enough for all current and near-term planned missions. Later, a modest evolution of FH (say, larger diameter methane upper stage) can cover payloads to what, ~80ton LEO?

"Intermediate size vehicle" is not necessary.

I'm in the "build a short version of 12m ITS, then stretch" camp.
Title: Re: ITS Development Updates and Discussion Thread
Post by: sevenperforce on 05/02/2017 03:03 pm
Elon's presentation was very clear that the spaceship would come first, followed by the booster.

Falcon Heavy can, in theory, lift an upper stage with a gross mass of anything up to 400 tonnes or so; any development stage smaller than that will be able to launch on FH for testing.

But don't underestimate the effort, cost, and impact upon launch revenue from modifying FH and its facilities to carry a one-off test payload.
Depends on size. If it's a 4-5 meter upper stage, all the vehicle modification you need is a custom interstage for FH (or even F9, if the upper stage isn't as heavy). Launch facility changes can't be as bad as adapting F9 stands for FH.

And it's not a one-off test payload, either; the intermediate version could become the standard upper stage, since it would enable upper-stage reuse in a way that F9US simply cannot.

I think keeping the 12 m diameter looses most of the advantage of making an intermediate size vehicle.
It's basically the same vehicle, with all of the same difficulties.
IMO, an advantageous intermediate vehicle needs to be much smaller to be both compatible with existing infrastructure and near future needs, and be easier to develope the composite structure, which may be the biggest hurdle on the path.
I agree. Any intermediate-size vehicles (like the promised AF methalox upper stage) would need to be able to launch on F9 or FH.

And you end up with three (count them!) diameters for your vehicles - F9, "intermediate size vehicle" and finally, 12m ITS.
Why?
Is there a huge market waiting to be served by this "intermediate size vehicle"? Empatically, no! F9/FH is more than enough for all current and near-term planned missions. Later, a modest evolution of FH (say, larger diameter methane upper stage) can cover payloads to what, ~80ton LEO?

"Intermediate size vehicle" is not necessary.
An intermediate-diameter booster is not necessary.

Title: Re: ITS Development Updates and Discussion Thread
Post by: RonM on 05/02/2017 03:30 pm
That row-boat comment also raised my eyebrow. But I think this does not necessarily apply to the rockets launched - you could have a massive, say, 10k people carrying, SEP or fusion powered ship built in orbit, which would then fly to its destination (say, Mars) and be serviced at both ends by ITS spaceships. Like in the ships of old, which were anchored off-shore and from which you had to take a rowing boat to get through the surf. The surf in this case being the orbit to surface distance, of course...

Good point. The planet to orbit vehicle doesn't have to be larger than ITS. A cargo ITS spaceship could ferry cargo modules or fuel tanks. A passenger ITS spacecraft could ferry several hundred passengers at a time.
Title: Re: ITS Development Updates and Discussion Thread
Post by: CriX on 05/02/2017 05:49 pm
That row-boat comment also raised my eyebrow. But I think this does not necessarily apply to the rockets launched - you could have a massive, say, 10k people carrying, SEP or fusion powered ship built in orbit, which would then fly to its destination (say, Mars) and be serviced at both ends by ITS spaceships. Like in the ships of old, which were anchored off-shore and from which you had to take a rowing boat to get through the surf. The surf in this case being the orbit to surface distance, of course...

I rewatched the scene, @34minutes, and his wording changes as he speaks... here, I just typed it up verbatim:

(Elon looking at a video of the ITS first stage boosting) "Well, this vehicle seems quite large and is large by comparison to other rockets. I think the future spacecraft will make this look like a rowboat.  The future spaceships will be truly enormous."

You may be right about him referring solely to the spaceships which may live in space permanently.  What would be the reasoning for making spaceships "truly enormous" when larger size also means more mass?  Maybe it is just a matter of comfort.  A very large spaceship would be able to transport 100 people to Mars much more comfortably.  Maybe more similarly to the comforts of current very large cruise ships. 


Though the first way I considered his comment was in asking myself, "Do we really have to rethink everything about boosters, even the shape, when you assume from the start that the whole system will be fully reusable?"  If the costs of fuel are the main costs per launch (the cost of the vehicle is amortized over 1000 launches say) then could you, for example build a 50m diameter, 50m tall squat-shaped booster which maximizes launchable volume while throwing fuel efficiency out the window?  Who cares if you burn an extra million dollars of fuel to get to orbit if you have get 10x volume to LEO.   Would future boosters inherently maintain the same basic shape of boosters of present?  I think it's an interesting question.
Title: Re: ITS Development Updates and Discussion Thread
Post by: sevenperforce on 05/02/2017 06:10 pm
Though the first way I considered his comment was in asking myself, "Do we really have to rethink everything about boosters, even the shape, when you assume from the start that the whole system will be fully reusable?"  If the costs of fuel are the main costs per launch (the cost of the vehicle is amortized over 1000 launches say) then could you, for example build a 50m diameter, 50m tall squat-shaped booster which maximizes launchable volume while throwing fuel efficiency out the window?  Who cares if you burn an extra million dollars of fuel to get to orbit if you have get 10x volume to LEO.   Would future boosters inherently maintain the same basic shape of boosters of present?  I think it's an interesting question.
Chrysler called...

(https://history.nasa.gov/SP-4221/p266.jpg)

Title: Re: ITS Development Updates and Discussion Thread
Post by: Kansan52 on 05/02/2017 06:34 pm
Now that using the 'way back machine'! Totally forgot about that.
Title: Re: ITS Development Updates and Discussion Thread
Post by: AncientU on 05/02/2017 10:20 pm
Well I tend to think the spaceship is more complicated with all the systems required to support up to 100 people for 5 months plus and they have never done it before. BFR is really just an increase in scale from something they have already built. So there is more likely to be a learning curve on the spaceship.

I agree that the learning curve is much steeper on spaceship, with control during EDL the greatest unknown.  (ECLSS and the like are just scaled like BFR booster flight vs Falcon 9.)  The reason I've advocated for an intermediate-sized vehicle is because testing a full-up version using the F9 approach would cost a few very expensive ships.  But maybe the F9 route is the way to go, just at the F9 scale.  The Hail Mary on FH debut may be a test of a return vehicle of approximately same geometry as BFS... this could be a huge step forward for ITS development.

It would also eliminate the need for initial testing on an intermediate sized (but still huge) vehicle, though I still think ITS will be a two-step.
Title: Re: ITS Development Updates and Discussion Thread
Post by: Robotbeat on 05/02/2017 11:47 pm
Stage recovery for FH is likely to be closer to BFS geometry than Dragon geometry.

Spaceship development first makes most sense. At least a scaled version could perhaps be launched on FH. It also is more sophisticated and may be harder overall, so makes sense to start on it first. But the booster isn't useful without the BFS.
Title: Re: ITS Development Updates and Discussion Thread
Post by: su27k on 05/03/2017 03:23 am
Well I tend to think the spaceship is more complicated with all the systems required to support up to 100 people for 5 months plus and they have never done it before. BFR is really just an increase in scale from something they have already built. So there is more likely to be a learning curve on the spaceship.

Seems to me the learning curve is exactly why you want to do it first, it takes longer so starting early makes sense. Also you want to retire the biggest development risk first, since the last thing you want to do is having invested billions in booster then finding out the spaceship doesn't work. Having worked out the most difficult parts also make it easy to convince potential investors.

(And for the life support system, they don't need to reach 100 people for 5 months in the first try, they only need 12 people for 5 months first, they can iterate later just like what they're doing with F9)
Title: Re: ITS Development Updates and Discussion Thread
Post by: jpo234 on 05/03/2017 07:09 am
Well I tend to think the spaceship is more complicated with all the systems required to support up to 100 people for 5 months plus and they have never done it before.

I highly doubt that the space ships of the first two decades will carry anything near 100 people. The first years will be heavily skewed to fright instead of passengers.
Title: Re: ITS Development Updates and Discussion Thread
Post by: JamesH65 on 05/03/2017 11:50 am
I agree. Any intermediate-size vehicles (like the promised AF methalox upper stage) would need to be able to launch on F9 or FH.

There is no promised AF methalox upper stage. The AF contract was for an engine, not a stage.

Not to say SpaceX will never make on. But right now, there is no evidence they are making one.

Unless someone can point me at some evidence.
Title: Re: ITS Development Updates and Discussion Thread
Post by: guckyfan on 05/03/2017 03:54 pm
I highly doubt that the space ships of the first two decades will carry anything near 100 people. The first years will be heavily skewed to fright instead of passengers.

The first manned landing will no doubt be frightful. I hope it gets better quickly.
Title: Re: ITS Development Updates and Discussion Thread
Post by: jpo234 on 05/03/2017 05:37 pm
I highly doubt that the space ships of the first two decades will carry anything near 100 people. The first years will be heavily skewed to fright instead of passengers.

The first manned landing will no doubt be frightful. I hope it gets better quickly.
Sorry, I blame this on SwiftKey.
Title: Re: ITS Development Updates and Discussion Thread
Post by: Jim on 05/03/2017 05:43 pm

Depends on size. If it's a 4-5 meter upper stage, all the vehicle modification you need is a custom interstage for FH (or even F9, if the upper stage isn't as heavy). Launch facility changes can't be as bad as adapting F9 stands for FH.



New hangar, new TEL and pad mods.  New production line, new method of transport.
Title: Re: ITS Development Updates and Discussion Thread
Post by: Jim on 05/03/2017 05:45 pm

An intermediate-diameter booster is not necessary.


Yes, it is.  By default, Spacex is not going to use mixed fueled vehicles.
Title: Re: ITS Development Updates and Discussion Thread
Post by: sevenperforce on 05/03/2017 08:05 pm

An intermediate-diameter booster is not necessary.


Yes, it is.  By default, Spacex is not going to use mixed fueled vehicles.
As much as I trust you on something like this, I don't know what to make of this January 13, 2016 Air Force press release (https://www.defense.gov/News/Contracts/Contract-View/Article/642983/) which seems to say something very different:

Quote
Space Exploration Technologies, Corp. (SpaceX), Hawthorne, California, has been awarded a $33,660,254 other transaction agreement for the development of the Raptor rocket propulsion system prototype for the Evolved Expendable Launch Vehicle (EELV) program. This agreement implements Section 1604 of the Fiscal Year 2015 National Defense Authorization Act, which requires the development of a next-generation rocket propulsion system that will transition away from the use of the Russian-supplied RD-180 engine to a domestic alternative for National Security Space launches. An other transaction agreement was used in lieu of a standard procurement contract in order to leverage on-going investment by industry in rocket propulsion systems. This other transaction agreement requires shared cost investment with SpaceX for the development of a prototype of the Raptor engine for the upper stage of the Falcon 9 and Falcon Heavy launch vehicles.

To me, this says specifically that the money from the Air Force went expressly to the development of a Raptor or Raptor derivative to be used for an upper stage for F9/FH. Am I missing something?
Title: Re: ITS Development Updates and Discussion Thread
Post by: rakaydos on 05/03/2017 08:56 pm

An intermediate-diameter booster is not necessary.


Yes, it is.  By default, Spacex is not going to use mixed fueled vehicles.
As much as I trust you on something like this, I don't know what to make of this January 13, 2016 Air Force press release (https://www.defense.gov/News/Contracts/Contract-View/Article/642983/) which seems to say something very different:

Quote
Space Exploration Technologies, Corp. (SpaceX), Hawthorne, California, has been awarded a $33,660,254 other transaction agreement for the development of the Raptor rocket propulsion system prototype for the Evolved Expendable Launch Vehicle (EELV) program. This agreement implements Section 1604 of the Fiscal Year 2015 National Defense Authorization Act, which requires the development of a next-generation rocket propulsion system that will transition away from the use of the Russian-supplied RD-180 engine to a domestic alternative for National Security Space launches. An other transaction agreement was used in lieu of a standard procurement contract in order to leverage on-going investment by industry in rocket propulsion systems. This other transaction agreement requires shared cost investment with SpaceX for the development of a prototype of the Raptor engine for the upper stage of the Falcon 9 and Falcon Heavy launch vehicles.

To me, this says specifically that the money from the Air Force went expressly to the development of a Raptor or Raptor derivative to be used for an upper stage for F9/FH. Am I missing something?
Jim said "By default, SpaceX..."

Goverment demands dumb stuff all the time. SpaceX filled that contract enough to get paid, then ignored the followup "suggestions". A lesson george lucas's staff could have learned for episodes 1-3.
Title: Re: ITS Development Updates and Discussion Thread
Post by: Kaputnik on 05/04/2017 06:52 am
We're all itching for updates.  I wouldn't expect SpaceX to spill all its (ITS?) beans but it hasn't run as silently as Blue Origins' program either.

Specifically I'd like to learn which is going to be the chicken and the egg: the spaceship or the booster.  Neither is going to be a small effort and either would find a health niche in the launcher economy here on Earth.
Elon's presentation was very clear that the spaceship would come first, followed by the booster.

Is there any clear advantage in developing the spaceship as opposed to the booster first?  Obviously it's Elon's plan and reasoning, but that should be a question given to Mr. Musk I think when the chance arises.

Look at how long Boca Chica is taking. Look how long rebuilding LC40 is taking. Ground facilities are a big, costly, and difficult part of LV development.

The ITS spaceship needs a launch pad that can handle the thrust of seven Raptors. The booster has 42, and the cradle system. So just the pad for the booster is a monumental project, whereas the ship's pad is going to be comparatively straightforward.

Build the ship first, in cargo/tanker version, even as an overbuilt boilerplate version, and get flight experience with the Raptors and composites, to make building the booster easier.
Title: Re: ITS Development Updates and Discussion Thread
Post by: Lars-J on 05/04/2017 06:02 pm
Right. You can't flight test the booster without the ship without creating a high fidelity mock-up of the spaceship to place on top. The booster will also require massive ground infrastructure changes.

But you can flight test the spaceship without the booster. And the spaceship can be tested without taking 39A out of service first.

Clearly development will overlap. But it is clear what makes sense to finish first.
Title: Re: ITS Development Updates and Discussion Thread
Post by: M.E.T. on 05/04/2017 07:05 pm
Right. You can't flight test the booster without the ship without creating a high fidelity mock-up of the spaceship to place on top. The booster will also require massive ground infrastructure changes.

But you can flight test the spaceship without the booster. And the spaceship can be tested without taking 39A out of service first.

Clearly development will overlap. But it is clear what makes sense to finish first.

Can you elobarate on how this would work? I thought Elon said the spaceship can almost, but not quite make it to LEO on its own. So would you flight test it in Grasshopper style or something? Or do you suggest that the full size ship, minus a lot of the heavy internal life support hardware, can somehow be fitted on top of a FH booster stack and launched into space?
Title: Re: ITS Development Updates and Discussion Thread
Post by: Lars-J on 05/04/2017 07:20 pm
Right. You can't flight test the booster without the ship without creating a high fidelity mock-up of the spaceship to place on top. The booster will also require massive ground infrastructure changes.

But you can flight test the spaceship without the booster. And the spaceship can be tested without taking 39A out of service first.

Clearly development will overlap. But it is clear what makes sense to finish first.

Can you elobarate on how this would work? I thought Elon said the spaceship can almost, but not quite make it to LEO on its own. So would you flight test it in Grasshopper style or something? Or do you suggest that the full size ship, minus a lot of the heavy internal life support hardware, can somehow be fitted on top of a FH booster stack and launched into space?

No, not launched on FH.

But you could do everything from Grasshopper style short jumps to high suborbital with RTLS. (Just like F9 first stages - and what the ITS booster will use)

You probably need to limit yourself to tests that return to launch site, since transporting a 17m max diameter spaceship is tricky. Now that I think of it, the ITS spaceship will be very close in size to the Saturn V first stage (S-IC) - So imagine something like this, but ... wider :) being trucked around.
Title: Re: ITS Development Updates and Discussion Thread
Post by: M.E.T. on 05/04/2017 07:26 pm
Right. You can't flight test the booster without the ship without creating a high fidelity mock-up of the spaceship to place on top. The booster will also require massive ground infrastructure changes.

But you can flight test the spaceship without the booster. And the spaceship can be tested without taking 39A out of service first.

Clearly development will overlap. But it is clear what makes sense to finish first.

Can you elobarate on how this would work? I thought Elon said the spaceship can almost, but not quite make it to LEO on its own. So would you flight test it in Grasshopper style or something? Or do you suggest that the full size ship, minus a lot of the heavy internal life support hardware, can somehow be fitted on top of a FH booster stack and launched into space?

No, not launched on FH.

But you could do everything from Grasshopper style short jumps to high suborbital with RTLS. (Just like F9 first stages - and what the ITS booster will use) You probably need to limit yourself to tests that return to launch site, since transporting a 17m max diameter spaceship is tricky.

OK, I understand.

To me the pity is that they can't develop an ITS that can serve an orbital cargo purpose as an intermediate step to building one that can go to Mars. But I'm not sure how that can be achieved.
Title: Re: ITS Development Updates and Discussion Thread
Post by: Lars-J on 05/04/2017 09:04 pm
To me the pity is that they can't develop an ITS that can serve an orbital cargo purpose as an intermediate step to building one that can go to Mars. But I'm not sure how that can be achieved.

I see it as inevitable that they will develop a LEO/GTO cargo version of the ITS spaceship... It may even fly first. What else are they going to do to with all the missions they need to fly to gain confidence in the designs ability to launch, re-enter and land - before they put lots of people on it?
Title: Re: ITS Development Updates and Discussion Thread
Post by: Kaputnik on 05/05/2017 09:06 am
IIRC, Elon said that the Spaceship would be able to reach LEO but not have enough fuel to get back again. However the tanker is probably a different matter, and I think some of our resident number crunchers have calculated that it is likely that a tanker version could do SSTO and back again- if they hit their dry mass targets.

(See the 'what ITS hardware will fly first' thread for some of this discussion)
Title: Re: ITS Development Updates and Discussion Thread
Post by: JamesH65 on 05/05/2017 01:52 pm
Right. You can't flight test the booster without the ship without creating a high fidelity mock-up of the spaceship to place on top. The booster will also require massive ground infrastructure changes.

But you can flight test the spaceship without the booster. And the spaceship can be tested without taking 39A out of service first.

Clearly development will overlap. But it is clear what makes sense to finish first.

Massive ground infrastructure changes will be needed for the spaceship anyway. Booster could be flown without a mockup - Grasshopper style.

You can flight test both without the other. But you cannot go to Mars without both.

Flight testing of the booster needs to be complete at the same time as flight testing of the Spaceship needs to be complete.  That probably means flight testing of the Spaceships needs to start first, as it is more complex.
Title: Re: ITS Development Updates and Discussion Thread
Post by: docmordrid on 05/05/2017 02:45 pm
The ITS development timeline presented at IAC showed Spaceship tests starting about 6 months before Booster tests, and finishing first.
Title: Re: ITS Development Updates and Discussion Thread
Post by: Johnnyhinbos on 05/05/2017 03:33 pm
I would shift everything on that graph by two years to realign the red dragon flight (and add in a tiny bit of reality)
Title: Re: ITS Development Updates and Discussion Thread
Post by: MP99 on 05/06/2017 11:32 am


IIRC, Elon said that the Spaceship would be able to reach LEO but not have enough fuel to get back again.

Maybe they could strap an external tank on the side to give an extra prop load?

Would probably need to also add some FH-type boosters on the side to lift the extra weight and balance out the thrust.

:-)

Cheers, Martin
Title: Re: ITS Development Updates and Discussion Thread
Post by: AncientU on 05/07/2017 12:21 am


IIRC, Elon said that the Spaceship would be able to reach LEO but not have enough fuel to get back again.

Maybe they could strap an external tank on the side to give an extra prop load?

Would probably need to also add some FH-type boosters on the side to lift the extra weight and balance out the thrust.

:-)

Cheers, Martin

Naaah... no one would build such a chimera. ;)
Title: Re: ITS Development Updates and Discussion Thread
Post by: redliox on 05/07/2017 12:58 am
I would shift everything on that graph by two years to realign the red dragon flight (and add in a tiny bit of reality)

That is a good factor to consider; however even if the Red Dragon is critical for gathering reentry and retropropulsion data it and ITS are different beasts.  The Raptor engine would be more critical for instance, the orbital testing done around Earth would still be applicable, and the fact both the Falcon and ITS boosters would be doing powered, non-parachute descents another way of getting work done independently of R.D.

Look at how long Boca Chica is taking. Look how long rebuilding LC40 is taking. Ground facilities are a big, costly, and difficult part of LV development.

The ITS spaceship needs a launch pad that can handle the thrust of seven Raptors. The booster has 42, and the cradle system. So just the pad for the booster is a monumental project, whereas the ship's pad is going to be comparatively straightforward.

In other words, developing a launch pad that can handle a blank-ton of heat...which as you point out isn't to be underestimated.
Title: Re: ITS Development Updates and Discussion Thread
Post by: rory on 05/22/2017 02:15 am
ITS update now delayed to 'a few months':

Quote
@elonmusk Eta on the ITS/BFR/MCT architecture changes?

https://twitter.com/RITSPEX/status/866470494203203584

Quote
Almost there. Probably in a few months.

https://twitter.com/elonmusk/status/866471370418339840

Sign of real progress being made? Or maybe the long pole is finding a better name...
Title: Re: ITS Development Updates and Discussion Thread
Post by: jpo234 on 05/22/2017 07:42 am
The name of ITS is now back to BFR? (this is from the 2016 (http://www.spacex.com/gallery/2016-0#slide-5) section of the new gallery)
Title: Re: ITS Development Updates and Discussion Thread
Post by: envy887 on 05/22/2017 01:20 pm
ITS update now delayed to 'a few months':

Quote
@elonmusk Eta on the ITS/BFR/MCT architecture changes?

https://twitter.com/RITSPEX/status/866470494203203584

Quote
Almost there. Probably in a few months.

https://twitter.com/elonmusk/status/866471370418339840

Sign of real progress being made? Or maybe the long pole is finding a better name...

The timeline is not just pacing real time, it's accelerating to the right :D
Title: Re: ITS Development Updates and Discussion Thread
Post by: Eerie on 05/22/2017 01:28 pm
Sign of real progress being made? Or maybe the long pole is finding a better name...

Maybe they just have better things to do? ITS was unveiled in September 2016. How about waiting a year before the update? It's not like ITS is coming any time soon, anyway.
Title: Re: ITS Development Updates and Discussion Thread
Post by: Robotbeat on 05/22/2017 02:58 pm
Sign of real progress being made? Or maybe the long pole is finding a better name...

Maybe they just have better things to do? ITS was unveiled in September 2016. How about waiting a year before the update? It's not like ITS is coming any time soon, anyway.
I think the opposite is true. Musk said they found ways for ITS to be more economical (for development), meaning they're probably going to fly earlier, since they won't be waiting on external funding or for the constellation to be in full deployment.

My guess: they want some new hardware to show off before another unveiling.
Title: Re: ITS Development Updates and Discussion Thread
Post by: docmordrid on 05/22/2017 03:29 pm
ISTM more economical = being involved with "CommX"'s rollout. Mass constellation dispensing, and not just SpaceX's, could be a cash cow.
Title: Re: ITS Development Updates and Discussion Thread
Post by: Eerie on 05/22/2017 03:41 pm
I think the opposite is true. Musk said they found ways for ITS to be more economical (for development), meaning they're probably going to fly earlier, since they won't be waiting on external funding or for the constellation to be in full deployment.
My guess: they want some new hardware to show off before another unveiling.

Do you have the quote for that? I remember him saying that they are working on it, not that they actually found a way already, but I can't find the exact quote.
Title: Re: ITS Development Updates and Discussion Thread
Post by: rory on 05/22/2017 04:41 pm
I think the opposite is true. Musk said they found ways for ITS to be more economical (for development), meaning they're probably going to fly earlier, since they won't be waiting on external funding or for the constellation to be in full deployment.
My guess: they want some new hardware to show off before another unveiling.

Do you have the quote for that? I remember him saying that they are working on it, not that they actually found a way already, but I can't find the exact quote.

It's from the SES-10 press conference:

Quote
RM: Just one follow-up, The time frame has kind of shifted since Guadalajara, I was wondering if if you guys had any updated time frame of when you think that first mission will be launched - If I'm correct, the first one is uncrewed, correct?

E: Yeah the first ones will be uncrewed. I don't want to steal thunder from that announcement. I'm pretty excited about the updated strategy since Guadalajara, it makes a lot more sense, it's  - we have to not just get it done technically, but figure out how to get this done without going bankrupt. So it's like, our goal is to get people on Mars before we're dead, and the company is dead. So like, neither one can die. Ideally, because we don't want to take so long that we're dead by when that happens, and we don't want to kill the company in the process. So we have to figure out not just solve the technical issues, but the economic issues. And I think the new approach is going to be able to do that. Hopefully.
https://github.com/robbak/SES10-post-launch-conference/blob/master/SES10-press-transcript.txt
Title: Re: ITS Development Updates and Discussion Thread
Post by: philw1776 on 05/22/2017 05:41 pm
The easiest and most accurate prediction I made here and on reddit on pre-reveal BFR threads was that the BFR to be revealed at IAC September 2016 would be revised considerably before flight.  I believe this to be accurate.  And similar to predicting "Sun to rise in East tomorrow", I say that the BFR update sometime later this year will be somewhat different from real orbital flight BFRs.

Until engine testing is well along and until tooling $ is spent for airframe, etc., I expect that this innovative stretching state of the art transportation system's configuration will continue to evolve.
Title: Re: ITS Development Updates and Discussion Thread
Post by: Robotbeat on 05/22/2017 05:42 pm
The easiest and most accurate prediction I made here and on reddit on pre-reveal BFR threads was that the BFR to be revealed at IAC September 2016 would be revised considerably before flight.  I believe this to be accurate.  And similar to predicting "Sun to rise in East tomorrow", I say that the BFR update sometime later this year will be somewhat different from real orbital flight BFRs.

Until engine testing is well along and until tooling $ is spent for airframe, etc., I expect that this innovative stretching state of the art transportation system's configuration will continue to evolve.
It's possible that part of the delay in the current announcement is to get some hardware to show off.
Title: Re: ITS Development Updates and Discussion Thread
Post by: DJPledger on 05/22/2017 05:49 pm
ITS update now delayed to 'a few months':

Quote
@elonmusk Eta on the ITS/BFR/MCT architecture changes?

https://twitter.com/RITSPEX/status/866470494203203584

Quote
Almost there. Probably in a few months.

https://twitter.com/elonmusk/status/866471370418339840

Sign of real progress being made? Or maybe the long pole is finding a better name...
The timeline is not just pacing real time, it's accelerating to the right :D
Perhaps SpaceX may be making major changes to the ITS system which is the reason for repeatedly delaying the ITS update announcement. Perhaps EM now says that 42 engines on the booster is too many and that Raptor can be scaled comfortably through a wide range of sizes due to a large percentage of it being additive manufactured. Larger Raptor for ITS booster can cut down no. of engines on ITS booster by at least half while keeping or maybe even increasing capability. Keep the 3.5MN vac. Raptor for the ITS ship. 9 is the right no. for the ITS ship.
Title: Re: ITS Development Updates and Discussion Thread
Post by: Robotbeat on 05/22/2017 05:55 pm
Might be a good question to ask in L2.
Title: Re: ITS Development Updates and Discussion Thread
Post by: Kaputnik on 05/22/2017 05:56 pm
It's obviously not impossible that they will decide to build two different sizes of methalox engine. But there are already extensive discussions on here explaining why scaling an engine is essentially the same as designing and qualifying a new engine. This is in part because certain things scale linearly, squared, cubed, etc.

I wish people would stop treating 3D printing as if it makes all things possible.

Title: Re: ITS Development Updates and Discussion Thread
Post by: Eerie on 05/22/2017 06:05 pm
I think the opposite is true. Musk said they found ways for ITS to be more economical (for development), meaning they're probably going to fly earlier, since they won't be waiting on external funding or for the constellation to be in full deployment.
My guess: they want some new hardware to show off before another unveiling.

Do you have the quote for that? I remember him saying that they are working on it, not that they actually found a way already, but I can't find the exact quote.

It's from the SES-10 press conference:

Quote
RM: Just one follow-up, The time frame has kind of shifted since Guadalajara, I was wondering if if you guys had any updated time frame of when you think that first mission will be launched - If I'm correct, the first one is uncrewed, correct?

E: Yeah the first ones will be uncrewed. I don't want to steal thunder from that announcement. I'm pretty excited about the updated strategy since Guadalajara, it makes a lot more sense, it's  - we have to not just get it done technically, but figure out how to get this done without going bankrupt. So it's like, our goal is to get people on Mars before we're dead, and the company is dead. So like, neither one can die. Ideally, because we don't want to take so long that we're dead by when that happens, and we don't want to kill the company in the process. So we have to figure out not just solve the technical issues, but the economic issues. And I think the new approach is going to be able to do that. Hopefully.
https://github.com/robbak/SES10-post-launch-conference/blob/master/SES10-press-transcript.txt

It says nowhere that this "updated strategy" actually involves using ITS. It could be just "build the CommX constellation first, and use the money from that to finance ITS".
Title: Re: ITS Development Updates and Discussion Thread
Post by: Robotbeat on 05/22/2017 06:07 pm
I think the opposite is true. Musk said they found ways for ITS to be more economical (for development), meaning they're probably going to fly earlier, since they won't be waiting on external funding or for the constellation to be in full deployment.
My guess: they want some new hardware to show off before another unveiling.

Do you have the quote for that? I remember him saying that they are working on it, not that they actually found a way already, but I can't find the exact quote.

It's from the SES-10 press conference:

Quote
RM: Just one follow-up, The time frame has kind of shifted since Guadalajara, I was wondering if if you guys had any updated time frame of when you think that first mission will be launched - If I'm correct, the first one is uncrewed, correct?

E: Yeah the first ones will be uncrewed. I don't want to steal thunder from that announcement. I'm pretty excited about the updated strategy since Guadalajara, it makes a lot more sense, it's  - we have to not just get it done technically, but figure out how to get this done without going bankrupt. So it's like, our goal is to get people on Mars before we're dead, and the company is dead. So like, neither one can die. Ideally, because we don't want to take so long that we're dead by when that happens, and we don't want to kill the company in the process. So we have to figure out not just solve the technical issues, but the economic issues. And I think the new approach is going to be able to do that. Hopefully.
https://github.com/robbak/SES10-post-launch-conference/blob/master/SES10-press-transcript.txt

It says nowhere that this "updated strategy" actually involves using ITS. It could be just "build the CommX constellation first, and use the money from that to finance ITS".
I mean sure, but that sounds like a dumb idea and not at all SpaceX-y.
Title: Re: ITS Development Updates and Discussion Thread
Post by: dror on 05/22/2017 06:07 pm
The easiest and most accurate prediction I made here and on reddit on pre-reveal BFR threads was that the BFR to be revealed at IAC September 2016 would be revised considerably before flight.  I believe this to be accurate.  And similar to predicting "Sun to rise in East tomorrow", I say that the BFR update sometime later this year will be somewhat different from real orbital flight BFRs.

Until engine testing is well along and until tooling $ is spent for airframe, etc., I expect that this innovative stretching state of the art transportation system's configuration will continue to evolve.
It's possible that part of the delay in the current announcement is to get some hardware to show off.
What  hardware would you expect them to reveal?
What would be worth the wait while expected in six_weaks_to_few_monthes?
Title: Re: ITS Development Updates and Discussion Thread
Post by: DJPledger on 05/22/2017 06:20 pm
It's obviously not impossible that they will decide to build two different sizes of methalox engine. But there are already extensive discussions on here explaining why scaling an engine is essentially the same as designing and qualifying a new engine. This is in part because certain things scale linearly, squared, cubed, etc.

I wish people would stop treating 3D printing as if it makes all things possible.


SpaceX will be building 2 diff. sizes of Raptor, the dev. 1MN engine and the 3.05MN SL full size version. So SpaceX will gain experience of scaling the Raptor up by a factor of about 3 from the prototype to the full production engine. Then it will be well within the bounds that SpaceX can further scale up Raptor for the ITS booster by about 2-3 to simplify the ITS booster MPS.
Title: Re: ITS Development Updates and Discussion Thread
Post by: DJPledger on 05/22/2017 06:23 pm
What  hardware would you expect them to reveal?
What would be worth the wait while expected in six_weaks_to_few_monthes?
Possibly some complete Raptor prototype engines and another Raptor test firing video. Maybe a new ITS tank.
Title: Re: ITS Development Updates and Discussion Thread
Post by: docmordrid on 05/22/2017 06:26 pm
Even though Musk tweeted a few months, what are the odds he'll do a reveal in his keynote for the ISS R&D conference in July?
Title: Re: ITS Development Updates and Discussion Thread
Post by: DJPledger on 05/22/2017 06:28 pm
Even though Musk tweeted a few months, what are the odds he'll do a reveal in his keynote for the ISS R&D conference in July?
Sounds quite plausible to me.
Title: Re: ITS Development Updates and Discussion Thread
Post by: oldAtlas_Eguy on 05/22/2017 08:54 pm
Even though Musk tweeted a few months, what are the odds he'll do a reveal in his keynote for the ISS R&D conference in July?
Sounds quite plausible to me.
The plausible range in the definition of "a few months" is 2 or more but less than 6. Valid values are 2,3,4, and 5. 5 would put it exactly 1 year later from initial reveal (Sept).

It is in the possibility that SpaceX could give 1 yearly update every September.
Title: Re: ITS Development Updates and Discussion Thread
Post by: Lars-J on 05/22/2017 09:08 pm
I don't know why people are so upset about this "delay". This is just a delay of releasing more/updated information. This is a separate things from a hardware/launch delay.

But then again this should be expected when people don't believe that SpaceX is working on something unless they see it.  ::) ;)
Title: Re: ITS Development Updates and Discussion Thread
Post by: Kansan52 on 05/22/2017 09:31 pm
I don't know why people are so upset about this "delay".

Think how bad is was for Chris when he had to 'sit' on the ITS info he had before the 'Big Reveal'! (definition, to 'sit' on information is to not reveal the information)
Title: Re: ITS Development Updates and Discussion Thread
Post by: JamesH65 on 05/23/2017 10:50 am
I don't know why people are so upset about this "delay".

Think how bad is was for Chris when he had to 'sit' on the ITS info he had before the 'Big Reveal'! (definition, to 'sit' on information is to not reveal the information)

Not too bad, just like any insider knowledge of product release. Happens all the time. I've got lots of insider knowledge of my companies releases for the next X years.  I don't feel bad sitting on it, and there is always lot of pressure from the community for new information.
Title: Re: ITS Development Updates and Discussion Thread
Post by: philw1776 on 05/23/2017 11:55 am
The easiest and most accurate prediction I made here and on reddit on pre-reveal BFR threads was that the BFR to be revealed at IAC September 2016 would be revised considerably before flight.  I believe this to be accurate.  And similar to predicting "Sun to rise in East tomorrow", I say that the BFR update sometime later this year will be somewhat different from real orbital flight BFRs.

Until engine testing is well along and until tooling $ is spent for airframe, etc., I expect that this innovative stretching state of the art transportation system's configuration will continue to evolve.
It's possible that part of the delay in the current announcement is to get some hardware to show off.

Yes
Unless I missed something, I have not read anything about more raptor engine tests.  Long duration, etc.
Title: Re: ITS Development Updates and Discussion Thread
Post by: oldAtlas_Eguy on 05/25/2017 02:27 pm
With Electron's successful use of an all carbon composite stage with carbon composite LOX tanks, SpaceX's use in their ITS design of carbon composite LOX tanks does not look quite so crazy.
Title: Re: ITS Development Updates and Discussion Thread
Post by: biosehnsucht on 05/25/2017 10:19 pm
Are Electron's tanks similarly pure composite or do they use a liner?
Title: Re: ITS Development Updates and Discussion Thread
Post by: jpo234 on 05/25/2017 10:29 pm
Well, about Electron and ITS.
Electron is supposed to cost 5 million dollars per launch for a payload of up to 225 kilograms. According to the Mars presentation all six launches of the ITS booster are supposed to cost 11 million dollars or less than 2 million dollars per launch. The five launches of the tanker are supposed to cost 8 million dollars or 1.6 million dollars per launch. The tanker is supposed to have a capacity for 380 tonnes of fuel.
Taking all of this together, SpaceX plans to launch more than 1000x the payload of the Electron rocket for about the same price.
Am I wrong?
Title: Re: ITS Development Updates and Discussion Thread
Post by: Robotbeat on 05/25/2017 10:35 pm
No, you aren't wrong. This is what scale and rapid reuse give you.
Title: Re: ITS Development Updates and Discussion Thread
Post by: Robotbeat on 05/25/2017 10:36 pm
What is the pressurized volume of ITS? How about unpressurized volume?
Title: Re: ITS Development Updates and Discussion Thread
Post by: whitelancer64 on 05/25/2017 11:05 pm
Well, about Electron and ITS.
Electron is supposed to cost 5 million dollars per launch for a payload of up to 225 kilograms. According to the Mars presentation all six launches of the ITS booster are supposed to cost 11 million dollars or less than 2 million dollars per launch. The five launches of the tanker are supposed to cost 8 million dollars or 1.6 million dollars per launch. The tanker is supposed to have a capacity for 380 tonnes of fuel.
Taking all of this together, SpaceX plans to launch more than 1000x the payload of the Electron rocket for about the same price.
Am I wrong?

Per that Mars presentation slide, the projected amortized cost is $62 million per ITS trip to Mars.

It also estimates the booster's fabrication costs as $230 million, the tanker's fabrication costs as $130 million, and the spaceship's fabrication cost as $200 million.

The $11 million (for boosters) and $8 million (for tankers) cost-per-Mars-trip assumes there will be 1,000 launches of each booster and 100 launches of each tanker. That's only getting fuel into LEO, by the way, there's no actual payload until the spaceship is sent to Mars. The slide gives the amortized (assuming 12 launches) cost per launch of the spaceship as $43 million.

So yes, you're wrong, in that the cost required to launch the payload (the spaceship) is much greater.

The slide does not give us an un-amortized estimate of the cost to launch a generic payload to LEO, so there's no way to directly compare the cost per launch with the Electron.
Title: Re: ITS Development Updates and Discussion Thread
Post by: Robotbeat on 05/25/2017 11:11 pm
Don't use spaceship costs as the spaceship can only be used one cycle every 26 months. Tanker is more representative. Use 100 times.
Title: Re: ITS Development Updates and Discussion Thread
Post by: hkultala on 05/27/2017 03:23 pm
It's obviously not impossible that they will decide to build two different sizes of methalox engine. But there are already extensive discussions on here explaining why scaling an engine is essentially the same as designing and qualifying a new engine. This is in part because certain things scale linearly, squared, cubed, etc.

I wish people would stop treating 3D printing as if it makes all things possible.


SpaceX will be building 2 diff. sizes of Raptor, the dev. 1MN engine and the 3.05MN SL full size version. So SpaceX will gain experience of scaling the Raptor up by a factor of about 3 from the prototype to the full production engine. Then it will be well within the bounds that SpaceX can further scale up Raptor for the ITS booster by about 2-3 to simplify the ITS booster MPS.

Does not work that way, and your idea is really bad.

Engine with 3 times more thrust in one chamber does not weight 3 times more. It weights considerably MORE than 3 times more due the thrust being linearry propotional to throat AREA but nozzle size throat area to power of 1.5.

Raptor is sized to be the sweet spot where good T/W can still be achieved, but also relatively high thrust can be achieved. Originally they were considering much bigger engines (F1A class) but ended up with the much smaller raptor due the better T/W.

And they do not want to build bigger engine that would only be used by the booster and completely separate engine for the spacecraft. They want to use same engines, to maximize the benefits of mass manufacturing.
Title: Re: ITS Development Updates and Discussion Thread
Post by: Robotbeat on 05/27/2017 07:09 pm
Smaller engines than the Merlin 1D don't have better thrust to weight ratio.
Title: Re: ITS Development Updates and Discussion Thread
Post by: livingjw on 05/28/2017 04:38 pm
Rocket engines scale pretty much linearly with thrust over large thrust ranges. This means that engine thrust to weight ratios are nearly constant over large thrust ranges. For a given level of technology thrust to weight has more to do with, cycle selection, propellant selection and operational considerations.

John
Title: Re: ITS Development Updates and Discussion Thread
Post by: gongora on 05/28/2017 07:26 pm
A Reddit user (https://www.reddit.com/r/spacex/comments/6duct2/gerald_r_everett_on_twitter_2_spacex_guys_i_have/) posted this interesting tweet from Gerald R Everett: (https://twitter.com/GREverett66/status/868777583579680768)
Quote
@SciGuySpace 2 SpaceX guys I have breakfast with say EM Sep. update is more about the money than tech. De-scope, make it pay for it'self.

follow-up tweet:
Quote
Elon Musk @ the IAC meeting 9/25 - 27,
Title: Re: ITS Development Updates and Discussion Thread
Post by: Robotbeat on 05/28/2017 07:42 pm
Rocket engines scale pretty much linearly with thrust over large thrust ranges. This means that engine thrust to weight ratios are nearly constant over large thrust ranges. For a given level of technology thrust to weight has more to do with, cycle selection, propellant selection and operational considerations.

John
T/W being constant over a range of thrusts is a sign you're near an optimum. Near an optimum, the value doesn't change much.
Title: Re: ITS Development Updates and Discussion Thread
Post by: Star One on 05/28/2017 07:43 pm
A Reddit user posted this interesting tweet (https://www.reddit.com/r/spacex/comments/6duct2/gerald_r_everett_on_twitter_2_spacex_guys_i_have/):

Direct link to tweet from Gerald R Everett (https://twitter.com/GREverett66/status/868777583579680768)
Quote
@SciGuySpace 2 SpaceX guys I have breakfast with say EM Sep. update is more about the money than tech. De-scope, make it pay for it'self.

Half the people are asking in that thread for a translation of what that somewhat cryptic Tweet actually means.
Title: Re: ITS Development Updates and Discussion Thread
Post by: AncientU on 05/28/2017 10:53 pm
September update fits the few months timeline we've discussed.
About finances -- check.
Descope -- check.
Pay for itself -- that's a bit further than make it affordable.  Paying for itself means tapping a revenue stream... maybe ConnX, but that is internal.  Maybe NASA joint ops???
Title: Re: ITS Development Updates and Discussion Thread
Post by: Robotbeat on 05/29/2017 12:17 am
Full replacement of F9 & H. Full reuse of all sub-SLS launches. That, combined with increased launch rate from the constellation, would cause it to easily pay for itself. Since it will fully replace the Falcons, that will obviously mean launching NASA payloads, too.

I would bet a whole bunch of money there's not some sort of special agreement with NASA for "joint ops," though. NASA barely believes Falcon 9 is really reusable, let alone ITS.
Title: Re: ITS Development Updates and Discussion Thread
Post by: docmordrid on 05/29/2017 02:57 am
>
 Paying for itself means tapping a revenue stream... maybe ConnX, but that is internal.  Maybe NASA joint ops???

A very large sat count constellation deployer? Mostly pay for launching CommX by launching other constellations.
Title: Re: ITS Development Updates and Discussion Thread
Post by: Robotbeat on 05/29/2017 03:58 am
Remember, if SpaceX is relying on this ITS variant for deploying the Constellation, that means they can tap outside Constellation investment to help pay for it (think Google, etc).
Title: Re: ITS Development Updates and Discussion Thread
Post by: woods170 on 05/29/2017 06:43 am
Full replacement of F9 & H. Full reuse of all sub-SLS launches. That, combined with increased launch rate from the constellation, would cause it to easily pay for itself. Since it will fully replace the Falcons, that will obviously mean launching NASA payloads, too.

I would bet a whole bunch of money there's not some sort of special agreement with NASA for "joint ops," though. NASA barely believes Falcon 9 is really reusable, let alone ITS.
My take on this:
Elon is Agile. SpaceX is agile. NASA is NOT agile. Joint ops is not gonna happen IMO given that it goes against everything SpaceX stands for. Also: SpaceX and Elon don't need NASA to get mini-ITS flying. The commercial backlog will pay for that.
Title: Re: ITS Development Updates and Discussion Thread
Post by: jpo234 on 05/29/2017 06:52 am
Full reuse of all sub-SLS launches.

Why sub-SLS? BFR (it seems we are back to this name) would outclass SLS when it starts to fly.
Title: Re: ITS Development Updates and Discussion Thread
Post by: jpo234 on 05/29/2017 06:58 am
A Reddit user (https://www.reddit.com/r/spacex/comments/6duct2/gerald_r_everett_on_twitter_2_spacex_guys_i_have/) posted this interesting tweet from Gerald R Everett: (https://twitter.com/GREverett66/status/868777583579680768)
Quote
@SciGuySpace 2 SpaceX guys I have breakfast with say EM Sep. update is more about the money than tech. De-scope, make it pay for it'self.

follow-up tweet:
Quote
Elon Musk @ the IAC meeting 9/25 - 27,

This is consistent with Musks remarks in the SES-10 press conference:
Quote
I'm pretty excited about the updated strategy since Guadalajara, it makes a lot more sense, it's - we have to not just get it done technically, but figure out how to get this done without going bankrupt. So it's like, our goal is to get people on Mars before we're dead, and the company is dead. So like, neither one can die. Ideally, because we don't want to take so long that we're dead by when that happens, and we don't want to kill the company in the process. So we have to figure out not just solve the technical issues, but the economic issues. And I think the new approach is going to be able to do that. Hopefully.
Title: Re: ITS Development Updates and Discussion Thread
Post by: AncientU on 05/29/2017 10:30 am
IAC 2017:
Quote
Elon Musk will likely reveal more details about the Interplanetary Transport system on the one year anniversary of the first announcement at the 2016 International Astronautical conference. IAC2017, hosted by the Space Industry Association of Australia (SIAA) will take place in Adelaide, Australia from 25 29 September 2017.

http://www.prometheism.net/elon-will-likely-reveal-more-details-on-his-big-mars-colonization-rocket-at-iac-2017-sept-25-29-2017-next-big-future/

New thread:
Topic: IAC 2017 -- ITS v0.2 
https://forum.nasaspaceflight.com/index.php?topic=43035.msg1683981#msg1683981
Title: Re: ITS Development Updates and Discussion Thread
Post by: Robotbeat on 05/29/2017 07:46 pm
Full reuse of all sub-SLS launches.

Why sub-SLS? BFR (it seems we are back to this name) would outclass SLS when it starts to fly.
We're talking a "descoped" BFR, not the IAC one. Because it's a big challenge for a two stage methane rocket with small enough thrust to launch from LC39a to do direct launch to escape with a payload matching SLS 1b or 2 while maintaining full reuse. But that hardly matters, as such NASA launches will be so rare that a few expended upper stages would be fine. Also, full BFR could be built by then, but in the meantime it'd allow SpaceX to bid on such launches with just the descoped BFR (which could have a decent flight history by the time any of this matters), then transition those payloads to fully reusable operations.

Interestingly, SpaceX could compete with even the MARGINAL cost of an SLS, even if they have to go for an expendable launch.
Title: Re: ITS Development Updates and Discussion Thread
Post by: envy887 on 05/29/2017 08:15 pm
Full reuse of all sub-SLS launches.

Why sub-SLS? BFR (it seems we are back to this name) would outclass SLS when it starts to fly.
We're talking a "descoped" BFR, not the IAC one. Because it's a big challenge for a two stage methane rocket with small enough thrust to launch from LC39a to do direct launch to escape with a payload matching SLS 1b or 2 while maintaining full reuse. But that hardly matters, as such NASA launches will be so rare that a few expended upper stages would be fine. Also, full BFR could be built by then, but in the meantime it'd allow SpaceX to bid on such launches with just the descoped BFR (which could have a decent flight history by the time any of this matters), then transition those payloads to fully reusable operations.

Interestingly, SpaceX could compete with even the MARGINAL cost of an SLS, even if they have to go for an expendable launch.
So don't do direct launch to escape. FH with a refuelable upper stage can send far more payload to escape than SLS can, while maintaining full reuse. It just needs a few fueling launches.
Title: Re: ITS Development Updates and Discussion Thread
Post by: Robotbeat on 05/29/2017 08:29 pm
Full reuse of all sub-SLS launches.

Why sub-SLS? BFR (it seems we are back to this name) would outclass SLS when it starts to fly.
We're talking a "descoped" BFR, not the IAC one. Because it's a big challenge for a two stage methane rocket with small enough thrust to launch from LC39a to do direct launch to escape with a payload matching SLS 1b or 2 while maintaining full reuse. But that hardly matters, as such NASA launches will be so rare that a few expended upper stages would be fine. Also, full BFR could be built by then, but in the meantime it'd allow SpaceX to bid on such launches with just the descoped BFR (which could have a decent flight history by the time any of this matters), then transition those payloads to fully reusable operations.

Interestingly, SpaceX could compete with even the MARGINAL cost of an SLS, even if they have to go for an expendable launch.
So don't do direct launch to escape. FH with a refuelable upper stage can send far more payload to escape than SLS can, while maintaining full reuse. It just needs a few fueling launches.
Of course that's possible. Nothing bigger than Falcon Heavy has ever been required for what NASA has planned. I'm just referring to a descoped ITS (which could handle an SLS-sized fairing just fine as well).

A descoped ITS could match SLS's capabilities one-to-one without more staging or refueling events. When you're arguing for the right to service those payloads, it helps not to have any asterisks. (EDIT: See my signature: To the maximum extent practicable, the Federal Government shall plan missions to accommodate the space transportation services capabilities of United States commercial providers. US law http://goo.gl/YZYNt0 )
Title: Re: ITS Development Updates and Discussion Thread
Post by: envy887 on 05/29/2017 09:16 pm
I'm not aware of any funded or even seriously proposed SLS payloads that could justify building and testing a dedicated expendable stage or even a fairing that size.

SpaceX has to prove orbital fueling anyway, and once proven it will be an asset, not an asterisk.
Title: Re: ITS Development Updates and Discussion Thread
Post by: Robotbeat on 05/29/2017 09:43 pm
I'm not aware of any funded or even seriously proposed SLS payloads that could justify building and testing a dedicated expendable stage or even a fairing that size.

SpaceX has to prove orbital fueling anyway, and once proven it will be an asset, not an asterisk.
They don't need to do anything special to make it expendable except not put recovery equipment on it and use up all the landing propellant for mission delta-v instead.

Potential payloads are few and far between, however they include gateway elements, and Europa Clipper.

The point is that parts of Congress want NASA to have (notional) payloads that only SLS can handle, even if the excuses are lame. This would mean SpaceX could potentially capture even those payloads designed to only fly on SLS, without any excuses.
Title: Re: ITS Development Updates and Discussion Thread
Post by: Norm38 on 05/30/2017 07:11 pm
Could "de-scope" mean something as simple as what we've all been assuming?  That the initial ITS won't carry 100 people, maybe just 10?  That lots of other requirements are scaled back?
It doesn't necessarily mean changes to the outer dimensions.  (Though it could mean the booster is shorter and gets stretched later, as others have suggested).
Title: Re: ITS Development Updates and Discussion Thread
Post by: FishInferno on 05/30/2017 07:32 pm
Could "de-scope" mean something as simple as what we've all been assuming?  That the initial ITS won't carry 100 people, maybe just 10?  That lots of other requirements are scaled back?
It doesn't necessarily mean changes to the outer dimensions.  (Though it could mean the booster is shorter and gets stretched later, as others have suggested).

Elon has already said that the first crew will carry around 10 (may have been 12) people. 

A shorter booster doesn't make much sense to me, as you still have to go through all of the same RnD processes as a larger booster, and the money you save by not having to build a bigger booster would possibly be outweighed by the further testing done for the upgrade to a larger booster. 
Title: Re: ITS Development Updates and Discussion Thread
Post by: envy887 on 05/30/2017 09:09 pm
Could "de-scope" mean something as simple as what we've all been assuming?  That the initial ITS won't carry 100 people, maybe just 10?  That lots of other requirements are scaled back?
It doesn't necessarily mean changes to the outer dimensions.  (Though it could mean the booster is shorter and gets stretched later, as others have suggested).

Elon has already said that the first crew will carry around 10 (may have been 12) people. 

A shorter booster doesn't make much sense to me, as you still have to go through all of the same RnD processes as a larger booster, and the money you save by not having to build a bigger booster would possibly be outweighed by the further testing done for the upgrade to a larger booster.

R&D for a shorter booster is a lot easier since they can derate the Raptor. Even just bringing it down to RD-180 territory should make it a lot easier to flight qualify initially. Then delta-qual later for more thrust, just like Merlin.

Ground handling a short booster is also a lot easier. As is RTLS since it stages much lower and slower and closer to the launch site. So the reuse penalty is much lower even with landing legs (which are also easier to make since the booster is much lighter).

11.5 mlbf is 21 Raptors derated by 20%. It's also just under the oft-quoted thrust limit of 39A, and exactly the thrust you need to liftoff a full spaceship with 150t payload atop a booster with the exact same tanks as the spaceship

A TWR of 1.2 and GLOM of 4300 tonnes (150t payload, 150t ship, 1950t prop, 100t booster, 1950t booster prop) puts 145t to 185 km circular orbit with the ship, or 195t with the tanker + return margin, even with derated Raptors. With 5 tanker launches it can still do a ~120 day transit and land 145t payload on Mars.
Title: Re: ITS Development Updates and Discussion Thread
Post by: Ionmars on 05/31/2017 08:17 pm
...
...
Why sub-SLS? BFR (it seems we are back to this name) would outclass SLS when it starts to fly.
May I suggest the name Intermediate ITS (IITS)?
The problem with Sub-scale BFR, ITS Junior, or Mini-ITS is their negative connotations. As if we began with something big and gorgeous and now we have to scale back. But if we are on a journey from the present rocket size toward something giant, then the half-way point is, well, Intermediate.

Title: Re: ITS Development Updates and Discussion Thread
Post by: MP99 on 06/02/2017 07:59 am
I am wondering about transport of ITS booster or the scaled back version via airship.

Obviously, this would be a heavy payload for an airship.

How much would the weight of the stage be reduced if the tanks were filled with helium at atmospheric pressure?

Would there be any mileage in making a custom version of one of the airships which is currently in development, but have it use the stage as a structural member? Of course, that would need to deal with issues when flying back empty.

Cheers, Martin
Title: Re: ITS Development Updates and Discussion Thread
Post by: Bynaus on 06/02/2017 09:10 am
Interesting idea. The lifting power of a He-filled stage is about 1 kg / m3 (~the density of air). A stage with 10 m diameter and 90 m length could thus carry a weight of (Pi * 25m^2 * 90 m =) 2250 kg, so only about 2 metric tons - presumably much less than its own weight.
Title: Re: ITS Development Updates and Discussion Thread
Post by: launchwatcher on 06/02/2017 02:54 pm
Interesting idea. The lifting power of a He-filled stage is about 1 kg / m3 (~the density of air). A stage with 10 m diameter and 90 m length could thus carry a weight of (Pi * 25m^2 * 90 m =) 2250 kg, so only about 2 metric tons - presumably much less than its own weight.
I get about 7 tons.   You forgot to multiply by pi. 
Title: Re: ITS Development Updates and Discussion Thread
Post by: rsdavis9 on 06/02/2017 03:09 pm
pi*5^2*90*(1.225-.179)=7393kg
1.225 density of air at stp
.179 density of helium at stp
Title: Re: ITS Development Updates and Discussion Thread
Post by: RoboGoofers on 06/02/2017 07:11 pm
the ITS presentation slides say the dry weight of the BFR is 275t. assuming metric and a 40m diameter (~ same as the Hindenburg), you'd need about 209m length. Hindenburg was 245m, but was not a cylinder, or completely full of helium.

I was initially thinking it'd be crazy big, but that's not unreasonable, considering something that large was built in the 1930s.

The picture below is from wikipedia (https://upload.wikimedia.org/wikipedia/commons/e/ee/Giant_Aircraft_Comparison.svg). the planes shows are roughly comparable to the BFR length.

also the slides say length is 77.5m and 12m diameter. where does 90m and 10m come from? should be 9168 kg.
Title: Re: ITS Development Updates and Discussion Thread
Post by: Kenp51d on 06/02/2017 07:21 pm
The Hindenburg used hydrogen, not hellium. Hydrogen has more lifting capacity Tha helium. Don't know how much more, but likely enough defferince to change your numbers.
Title: Re: ITS Development Updates and Discussion Thread
Post by: RoboGoofers on 06/02/2017 07:31 pm
The Hindenburg used hydrogen, not hellium. Hydrogen has more lifting capacity Tha helium. Don't know how much more, but likely enough defferince to change your numbers.

 ::) That's why I used the formula given by rsdavis9:
pi*5^2*90*(1.225-.179)=7393kg
1.225 density of air at stp
.179 density of helium at stp
Title: Re: ITS Development Updates and Discussion Thread
Post by: TrueBlueWitt on 06/02/2017 07:40 pm
pi*5^2*90*(1.225-.179)=7393kg
1.225 density of air at stp
.179 density of helium at stp


Time to remember a few things..

STP is only at Sea Level.. Air gets less dense quickly going up, so less lift.

Helium in the tanks is definitely NOT at STP.. as it's used to pressurize the tank. Not sure what the pressure is, but probably many times more dense at that pressure than at STP. 
Total mass of the Helium, as loaded in F9 S1 or S2, divided by the corresponding S1/S2 tank's empty volume would be a good estimate for density to use.

Title: Re: ITS Development Updates and Discussion Thread
Post by: RoboGoofers on 06/02/2017 07:50 pm
pi*5^2*90*(1.225-.179)=7393kg
1.225 density of air at stp
.179 density of helium at stp


Time to remember a few things..

STP is only at Sea Level.. Air gets less dense quickly going up, so less lift.

Helium in the tanks is definitely NOT at STP.. as it's used to pressurize the tank. Not sure what the pressure is, but probably many times more dense at that pressure than at STP. 
Total mass of the Helium, as loaded in F9 S1 or S2, divided by the corresponding S1/S2 tank's empty volume would be a good estimate for density to use.

Sorry, but i was digressing to how much helium you'd need to transport a BFR tank, not the idea of floating the tank alone. that's clearly impossible even with hydrogen.

here's an interesting article. http://www.airships.net/helium-hydrogen-airships/

gives the dead weight of Hindenburg as 118,000 kg and lifting capacity at 190,509 kg with helium. so, nowhere near enough to lift BFR. of course that's with 1930's tech, but even so a modern airship transport for BFR would  need to be larger than the Hindenburg.

so instead of just building the factory next to the launch site, they'd need to embark on an airship development and manufacturing program, and they'd still need a factory for the BFR.
Title: Re: ITS Development Updates and Discussion Thread
Post by: RedLineTrain on 06/02/2017 08:16 pm
The airship as BFR transport thing does seem a little remote, but as stated in another thread, I've had fun thinking about it.  Sergey Brin is building an airship that probably could carry a subscale ITS.  And he has the facilities to build an airship that could lift some 500 tons.

Quote from: Radio program in 2013
Alan Weston [Now CEO of Brin's airship company]: You’ve characterised it very well. Yes, the project that you’re describing uses compression of helium to control buoyancy. And so the way that works is that the helium in the main envelope is taken and stored in bags inside the airship at a slightly higher pressure. As you do that, air is taken in from the outside into essentially like lungs that are attached in the side of the vehicle. So the analogy of breathing is a good one. And the overall lift of the vehicle is equal to the weight of the air that is being displaced by the helium. And as you change that, you can control the amount of buoyancy that the vehicle has.

This turns out to be a critical factor in the operability of these new airships, because it means that you can on-load and offload payloads up to, as I said earlier, 500 tons, without using ballast. And, as you can imagine, when you start thinking about very large payloads, moving 500 tons of ballast on and off an airship becomes very difficult.

Radio program transcript (http://www.abc.net.au/radionational/programs/futuretense/the-airship27s-second-coming/4687934#transcript)
Title: Re: ITS Development Updates and Discussion Thread
Post by: Kenp51d on 06/02/2017 09:51 pm
Would you need to lift anything basically more than the ITS shell and it's internal tankage? The heavy bits (engines and various other hardware) could be sent separately on a tractor trailer.
Or so it seems to me. No clue if that gets the wieght down enough.
Downside is you still need a considerable effort and facility near launch site.
Be dang cool to see flying overhead. For sure an Email ticket. (Well that dates me, but good).

Sent from my XT1565 using Tapatalk

Title: Re: ITS Development Updates and Discussion Thread
Post by: TomH on 06/03/2017 01:37 am
If they decided not to put the factory adjacent to the launch site, it would be a whole lot simpler and cheaper to put the factory on an existing waterway and buy/rent/modify an old barge in contrast to designing and building a new world record dirigible. K...I...S...S....  There is a big reason for all the sea going freight in the world and the non-existence of dirigible/B-limp cargo. And that reason has nothing to do with Hydrogen. It has everything to do with efficiency and cost.
Title: Re: ITS Development Updates and Discussion Thread
Post by: rsdavis9 on 06/03/2017 10:12 am
It was still fun talking about balloons!  :)
Every kid loves balloons.
Title: Re: ITS Development Updates and Discussion Thread
Post by: Kenp51d on 06/03/2017 08:48 pm
It was still fun talking about balloons!  :)
Every kid loves balloons.

It will be even better to to be able to spot the spaceship in orbit at night like you can ISS.

Sent from my XT1565 using Tapatalk

Title: Re: ITS Development Updates and Discussion Thread
Post by: Joris on 06/04/2017 10:21 pm
In the eyes of you experts, what would be a realistic timeline for ITS?

When could we reasonably expect a first launch of this thing?

I don't think this thing is gonna be in orbit in 3 years.
Title: Re: ITS Development Updates and Discussion Thread
Post by: jpo234 on 06/04/2017 10:43 pm
In the eyes of you experts, what would be a realistic timeline for ITS?

When could we reasonably expect a first launch of this thing?

I don't think this thing is gonna be in orbit in 3 years.
The time line from the ITS presentation still seems to be on. Paul Wooster (SpaceX head of Technical Development Mars Architecture and Vehicles) recently said, that there is a realistic chance to get a manned mission to Mars in the mid 2020s.
Title: Re: ITS Development Updates and Discussion Thread
Post by: TomH on 06/04/2017 11:01 pm
It was still fun talking about balloons!  :)
Every kid loves balloons.

It will be even better to to be able to spot the spaceship in orbit at night like you can ISS.

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And this site is certainly not one for children.........nor for childishness on the part of adults.
Title: Re: ITS Development Updates and Discussion Thread
Post by: FutureSpaceTourist on 06/09/2017 10:47 pm
Quote
Martijn Meijering‏ @mmeijeri 1h1 hour ago

Hello @elonmusk, how come you're not burning a hole in your landing pads like @ID_AA_Carmack used to do?
https://twitter.com/mmeijeri/status/873290378702721026 (https://twitter.com/mmeijeri/status/873290378702721026)

Quote
John Carmack‏ Verified account @ID_AA_Carmack 23m23 minutes ago

SpaceX lands Really Fast.  Frighteningly so.  They never come to a stop, they are still decelerating as the landing gear is touching down.

Quote
Elon Musk ‏Verified account @elonmusk
Replying to @ID_AA_Carmack @mmeijeri

The faster, the better. Gravity losses.

Quote
RITSpaceExploration‏ @RITSPEX 13m13 minutes ago
Replying to @elonmusk @ID_AA_Carmack @mmeijeri

Will ITS use a suicide burn to minimize gravity losses or hover to land in the launch mount more accurately?

Quote
Elon Musk‏Verified account @elonmusk 12m12 minutes ago

Slow at first, then very fast. Def not hover.
https://twitter.com/elonmusk/status/873306583983247360 (https://twitter.com/elonmusk/status/873306583983247360)
Title: Re: ITS Development Updates and Discussion Thread
Post by: Norm38 on 06/10/2017 03:32 am
At idle, the left over exhaust gasses are vented overboard.  So there is a constant ullage thrust (very low). This keeps the propellants settled, which reduces the boil off a factor of 2 or more.

This is from the ULA Vulcan discussion, it's a factor I wasn't aware of, though it makes sense.  Settled fuel has less surface area, less heat absorption, less boil off.
So does this argue for some sort of electric / other low thrust propulsion during the cruise phase?  Even if it's not significant from a course/navigation standpoint, but just enough to keep the fuel settled?

As a bonus, the same thrust would settle dust/debris in the crew cabin, making housekeeping for passengers/crew a lot easier.
Title: Re: ITS Development Updates and Discussion Thread
Post by: guckyfan on 06/10/2017 07:23 am
SpaceX solves that problem by having separate tanks for the landing propellant inside the main tanks. That puts the landing propellant where it is best for balance during EDL.
Title: Re: ITS Development Updates and Discussion Thread
Post by: AncientU on 06/10/2017 10:15 am

Quote
RITSpaceExploration‏ @RITSPEX 13m13 minutes ago
Replying to @elonmusk @ID_AA_Carmack @mmeijeri

Will ITS use a suicide burn to minimize gravity losses or hover to land in the launch mount more accurately?

Quote
Elon Musk‏Verified account @elonmusk 12m12 minutes ago

Slow at first, then very fast. Def not hover.
https://twitter.com/elonmusk/status/873306583983247360 (https://twitter.com/elonmusk/status/873306583983247360)

Counterintuitive, but will be great to witness!
Title: Re: ITS Development Updates and Discussion Thread
Post by: guckyfan on 06/10/2017 10:33 am

Counterintuitive, but will be great to witness!

I read this as the first landings will be slow for safety and precision. With experience they speed up landing to a more propellant economic fast landing.
Title: Re: ITS Development Updates and Discussion Thread
Post by: rsdavis9 on 06/10/2017 11:22 am

Counterintuitive, but will be great to witness!

I read this as the first landings will be slow for safety and precision. With experience they speed up landing to a more propellant economic fast landing.

I think he means at some distance above the mount slow down and line up but then drop very quickly.
Once again there is more than one way to parse elon words.
Title: Re: ITS Development Updates and Discussion Thread
Post by: Robotbeat on 06/10/2017 01:34 pm

Counterintuitive, but will be great to witness!

I read this as the first landings will be slow for safety and precision. With experience they speed up landing to a more propellant economic fast landing.

I think he means at some distance above the mount slow down and line up but then drop very quickly.
Once again there is more than one way to parse elon words.
There are always multiple /wrong/ ways to parse his words... Yours doesn't make sense in context, i.e. with respect to gravity losses.
Title: Re: ITS Development Updates and Discussion Thread
Post by: oldAtlas_Eguy on 06/10/2017 02:49 pm

Counterintuitive, but will be great to witness!

I read this as the first landings will be slow for safety and precision. With experience they speed up landing to a more propellant economic fast landing.

I think he means at some distance above the mount slow down and line up but then drop very quickly.
Once again there is more than one way to parse elon words.
There are always multiple /wrong/ ways to parse his words... Yours doesn't make sense in context, i.e. with respect to gravity losses.
An alternate parse is he is talking about thrust levels. Low thrust at first then high at landing to reduce the last bit of velocity. This enables the use of aero surfaces for high level of control because of the velocity. Then switching to cold gas or similar type of thrusters at the end for the the lower velocity and low effectiveness of the aero surfaces (grid fins?).
Title: Re: ITS Development Updates and Discussion Thread
Post by: livingjw on 06/10/2017 03:26 pm
Intuitive. The higher the thrust > the higher the deceleration > the lower the time > the lower the gravity losses > the less fuel is needed, but timing is more critical. So, start with lower thrust to get your timing just right, then start upping the thrust to reduce your losses.
Title: Re: ITS Development Updates and Discussion Thread
Post by: ThereIWas3 on 06/10/2017 03:33 pm
You also do not want to get blown sideways once you are lined up, so lingering over the pad any more than necessary is not a good idea.
Title: Re: ITS Development Updates and Discussion Thread
Post by: meekGee on 06/10/2017 08:28 pm

Counterintuitive, but will be great to witness!

I read this as the first landings will be slow for safety and precision. With experience they speed up landing to a more propellant economic fast landing.


Slow != precise.

Hovering just gives more time for things to go wrong.

In X-Y, the most "precise" ,ethod is to never slow down and just crash into the 0,0 point...

Sadly that's not conducive to reusability, and so they'll try to crash as fast as possible while still landing. Hence Hover-slam.

They might try to land slow at first (with BFS) - basically tuning the Z-axis precision while allowing off-center landing, and then once Z is dialed in, go for X-Y precision.
Title: Re: ITS Development Updates and Discussion Thread
Post by: zack on 06/10/2017 08:44 pm
Quote
We are developing the interplanetary rocket and spaceship to allow anyone to travel to the moon, Mars & beyond, regardless of nationality
-Elon Musk
https://twitter.com/elonmusk/status/873629817895133184 (https://twitter.com/elonmusk/status/873629817895133184)

Mhmm, is that the first time Elon confirmed that ITS will go to the moon?
Title: Re: ITS Development Updates and Discussion Thread
Post by: MikeAtkinson on 06/10/2017 09:02 pm
Quote
We are developing the interplanetary rocket and spaceship to allow anyone to travel to the moon, Mars & beyond, regardless of nationality
-Elon Musk
https://twitter.com/elonmusk/status/873629817895133184 (https://twitter.com/elonmusk/status/873629817895133184)

Mhmm, is that the first time Elon confirmed that ITS will go to the moon?

Almost. He said " I don't think the Moon is a necessary step, but I think if you've got a rocket and spacecraft capable of going to Mars, you might as well go to the Moon as well - it's along the way. That's like crossing the English Channel, relative to Mars. So, it's like, if you have these ships that could cross the Atlantic, would you cross the English Channel? Probably. It's definitely not necessary, but you'd probably end up having a Moon base just because, like, why not, ya know."  http://shitelonsays.com/transcript/elon-musk-at-mits-aeroastro-centennial-part-2-of-6-2014-10-24

That was before ITS was announced.
Title: Re: ITS Development Updates and Discussion Thread
Post by: SweetWater on 06/10/2017 09:09 pm
Quote
We are developing the interplanetary rocket and spaceship to allow anyone to travel to the moon, Mars & beyond, regardless of nationality
-Elon Musk
https://twitter.com/elonmusk/status/873629817895133184 (https://twitter.com/elonmusk/status/873629817895133184)

Mhmm, is that the first time Elon confirmed that ITS will go to the moon?

Practicing Kremlinology with respect to Elon's statements can be a dubious prospect at best; however, it certainly does seem to imply that ITS will be ABLE to go to the Moon, if a customer wishes to purchase/charter/lease one to do so. I've never heard/read Musk express much interest in the moon himself; however, if a government or organization is willing to cut a big enough check, I'm sure he'd be more than happy to help enable them to go there.
Title: Re: ITS Development Updates and Discussion Thread
Post by: oldAtlas_Eguy on 06/11/2017 02:18 am
Considering that the ITS is itself significantly larger than any near term Moonbase anyone has mentioned. 100's mt or 100's of personnel for one vehicle landing. It would not take many flights and not a lot of funding to build a very large base. With possible initial Moon flights price of $500M and then later as the flight rate is much higher and costs are much lower with possible <$100M per flight prices or even a lot less than that <$20M is possible.

So yes someone like a mining company could purchase a flight probably cheaper than doing things piecemeal using other rockets with also delivering more equipment and personnel to setup the base and mining operations in a single operation. All that mining company would need is an investor that provides $1B in funds to purchase $500M in mining hardware (most of the money here is spent on developing this hardware) and the other $500M to deliver the hardware and personnel to the Moon surface. This would not be a small prototype operation but a full scale production mine. Initially just the cost of launch even at $100M for 200mt would make anything mined valued at $500/kg even plain sand. So once large scale BEO operations start mining will be a profitable business because using cheaper local supplied materials vs shipping from Earth will be a significant business opportunity.

Ok now back to ITS development.
The ITS having the ability to land and takeoff from Mars would have the inherent capability to land on and takeoff from the the Moon. Now the question is how much payload can it land on the Moon when it refuels just in LEO and still be able to takeoff and return to Earth and then land on Earth?
Title: Re: ITS Development Updates and Discussion Thread
Post by: Norm38 on 06/11/2017 02:46 am
SpaceX solves that problem by having separate tanks for the landing propellant inside the main tanks. That puts the landing propellant where it is best for balance during EDL.

Does the landing propellant include the propellant to brake into Mars orbit? (Unless the plan is direct entry into aerobraking without a burn)
If there is no main tank use at Mars, are the main tanks to be vented after the Earth departure burn to turn them into giant thermos bottles? Otherwise, wouldn't settling the landing tanks still be beneficial?
Title: Re: ITS Development Updates and Discussion Thread
Post by: envy887 on 06/11/2017 02:53 am
SpaceX solves that problem by having separate tanks for the landing propellant inside the main tanks. That puts the landing propellant where it is best for balance during EDL.

Does the landing propellant include the propellant to brake into Mars orbit? (Unless the plan is direct entry into aerobraking without a burn)
If there is no main tank use at Mars, are the main tanks to be vented after the Earth departure burn to turn them into giant thermos bottles? Otherwise, wouldn't settling the landing tanks still be beneficial?
Direct entry only. And I'm sure the main tanks will be vented... Pressurizing them wastes mass.
Title: Re: ITS Development Updates and Discussion Thread
Post by: RotoSequence on 06/11/2017 03:42 am
SpaceX solves that problem by having separate tanks for the landing propellant inside the main tanks. That puts the landing propellant where it is best for balance during EDL.

Does the landing propellant include the propellant to brake into Mars orbit? (Unless the plan is direct entry into aerobraking without a burn)
If there is no main tank use at Mars, are the main tanks to be vented after the Earth departure burn to turn them into giant thermos bottles? Otherwise, wouldn't settling the landing tanks still be beneficial?
Direct entry only. And I'm sure the main tanks will be vented... Pressurizing them wastes mass.

If they're evacuated during the trip, pressurizing them for atmospheric entry will be an interesting engineering challenge.
Title: Re: ITS Development Updates and Discussion Thread
Post by: Robotbeat on 06/11/2017 05:09 am
I really doubt they'd have the tanks at vacuum during any significant acceleration. Pressurizing the tanks reduces the structural mass needed.
Title: Re: ITS Development Updates and Discussion Thread
Post by: TrevorMonty on 06/11/2017 10:48 am




Ok now back to ITS development.
The ITS having the ability to land and takeoff from Mars would have the inherent capability to land on and takeoff from the the Moon. Now the question is how much payload can it land on the Moon when it refuels just in LEO and still be able to takeoff and return to Earth and then land on Earth?

There are discussions/ threads devoted to ITS moon landing performance. Not sure what conclusion was at end. I think it is around 8-9km/s round trip from LEO -moon- earth.


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Title: Re: ITS Development Updates and Discussion Thread
Post by: oldAtlas_Eguy on 06/11/2017 05:47 pm




Ok now back to ITS development.
The ITS having the ability to land and takeoff from Mars would have the inherent capability to land on and takeoff from the the Moon. Now the question is how much payload can it land on the Moon when it refuels just in LEO and still be able to takeoff and return to Earth and then land on Earth?

There are discussions/ threads devoted to ITS moon landing performance. Not sure what conclusion was at end. I think it is around 8-9km/s round trip from LEO -moon- earth.


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Thanks.
That would put the payload delivery to the Moon surface at >50% but <80% of the Mars max load.

The most interesting item here is there is no infrastructure requirements for the Moon for this to work. No prop plants required, no power farms, ... nothing. If later these infrastructure is built up so that the ITS can be refueled on the Lunar surface then the payload delivery would go to the vehicle max capability. An incentive for a third party to mine and produce propellant.

The most significant item here for the ITS design is that it would only require some analysis and software updates for payload organization (CG location optimization) and flight profile for landing and takeoff from the Moon. Should not require any hardware modifications.
Title: Re: ITS Development Updates and Discussion Thread
Post by: envy887 on 06/12/2017 01:46 am
I really doubt they'd have the tanks at vacuum during any significant acceleration. Pressurizing the tanks reduces the structural mass needed.
This is also very true. I'm a bit torn on this point. If you rely on pressure for structural​ support, them a loss of pressure could leave the crew SOL if something punctures the tank in transit.

The tanks will probably need MMOD protection anyway, but needing to pressurize them for landing might require a higher level of protection. That might eat any structural mass savings...

For transit I'm sure they will be at vacuum, though. It's safer if they are de-energized, and vacuum is better for keeping the cryo props in the landing tanks cold.
Title: Re: ITS Development Updates and Discussion Thread
Post by: wannamoonbase on 06/12/2017 02:58 am
The ITS having the ability to land and takeoff from Mars would have the inherent capability to land on and takeoff from the the Moon. Now the question is how much payload can it land on the Moon when it refuels just in LEO and still be able to takeoff and return to Earth and then land on Earth?

A LOx plant on the moon would go a very long way to helping maximize payload to the lunar surface.
Title: Re: ITS Development Updates and Discussion Thread
Post by: Lar on 06/12/2017 04:35 am
For transit I'm sure they will be at vacuum, though. It's safer if they are de-energized, and vacuum is better for keeping the cryo props in the landing tanks cold.
I'm having a lot of trouble seeing this, I would think they'd want pressurized tanks, and would want the ability to repair any MMOD damage enroute to keep them pressurized.
Title: Re: ITS Development Updates and Discussion Thread
Post by: Semmel on 06/12/2017 05:38 am
I'm having a lot of trouble seeing this, I would think they'd want pressurized tanks, and would want the ability to repair any MMOD damage enroute to keep them pressurized.

How is this supposed to work? I mean repair of holes in a tank in space..
Title: Re: ITS Development Updates and Discussion Thread
Post by: jpo234 on 06/12/2017 06:53 am
How is this supposed to work? I mean repair of holes in a tank in space..

Maybe a remote on the inside? Having one for inspections would probably be a good idea...
Title: Re: ITS Development Updates and Discussion Thread
Post by: Robotbeat on 06/12/2017 07:02 am
MMOD is far rarer in deep space than in LEO. Also, ITS will be covered in TPS, not just a big tank.
Title: Re: ITS Development Updates and Discussion Thread
Post by: guckyfan on 06/12/2017 07:23 am
I think they can do Mars landing without pressurization. Which would mean they can do repair of a tank when necessary, on the surface. It should be really rare. Reparing a hit in the pressurized area would be much easier with crew on board.
Title: Re: ITS Development Updates and Discussion Thread
Post by: livingjw on 06/12/2017 11:30 am
Rockets are designed to barely stand themselves upright in 1 g unpressurized. Flight loads of any kind will require pressurization to some level.

John
Title: Re: ITS Development Updates and Discussion Thread
Post by: guckyfan on 06/12/2017 11:54 am
Rockets are designed to barely stand themselves upright in 1 g unpressurized. Flight loads of any kind will require pressurization to some level.

John

I was probably wrong.
Title: Re: ITS Development Updates and Discussion Thread
Post by: dror on 06/12/2017 12:09 pm
The ITS having the ability to land and takeoff from Mars would have the inherent capability to land on and takeoff from the the Moon. Now the question is how much payload can it land on the Moon when it refuels just in LEO and still be able to takeoff and return to Earth and then land on Earth?

A LOx plant on the moon would go a very long way to helping maximize payload to the lunar surface.
Wouldn't it be easier to refuel at EML1 or on LLO then to build mines and factories on the moon?
Title: Re: ITS Development Updates and Discussion Thread
Post by: spacenut on 06/12/2017 12:24 pm
Yes, if they can make LOX on the moon's surface, ITS will only have to carry extra liquid methane when going to and from the moon.  However, if they can find enough lunar ice, they may be able to make liquid methane also, but carbon would be needed from somewhere. 
Title: Re: ITS Development Updates and Discussion Thread
Post by: guckyfan on 06/12/2017 01:04 pm
Yes, if they can make LOX on the moon's surface, ITS will only have to carry extra liquid methane when going to and from the moon.  However, if they can find enough lunar ice, they may be able to make liquid methane also, but carbon would be needed from somewhere.

The cold traps at the poles are supposed to contain CO and CO2. So methane production would be possible.

I have seen, that there is development for producing oxygen from SiO2. That source would be inexhaustible and available anywhere on the moon. It works by heating the SiO2 with a solar concentrator, then using electrolysis for splitting, if I understand correctly. That would require bringing the methane but LOX is by far the bigger share of propellant by weight. Maybe one day the Si could be used too.
Title: Re: ITS Development Updates and Discussion Thread
Post by: envy887 on 06/12/2017 01:12 pm
MMOD is far rarer in deep space than in LEO. Also, ITS will be covered in TPS, not just a big tank.

ITS won't just be operating in deep space, though. See Elon's grand plans for staging hundreds of them in Earth orbit between synods, etc. Some MMOD protection will be necessary to do that.

Small punctures in a low-pressure vessel aren't necessarily a huge deal for entry, as long as the TPS isn't significatly damaged. The tank can be pressurized shortly before entry, and the leak rate through a small hole is nowhere near enough to depressurize the ITS tanks in a few minutes.

They are a big deal for a tank that has to operate with pressure for months, though.
Title: Re: ITS Development Updates and Discussion Thread
Post by: JasonAW3 on 06/12/2017 03:58 pm
How is this supposed to work? I mean repair of holes in a tank in space..

Maybe a remote on the inside? Having one for inspections would probably be a good idea...

Possibly like some sort of hole sealing roomba?
Title: Re: ITS Development Updates and Discussion Thread
Post by: jpo234 on 06/12/2017 04:31 pm
Rockets are designed to barely stand themselves upright in 1 g unpressurized. Flight loads of any kind will require pressurization to some level.

John

I understand this. But: Does this really apply to the ITS space ship?
It has to survive reentry from interplanetary speeds, so it has to have some significant structural strength, doesn't it? Shouldn't we compare it to the STS Orbiter?
Title: Re: ITS Development Updates and Discussion Thread
Post by: Robotbeat on 06/12/2017 04:55 pm
Yes, if they can make LOX on the moon's surface, ITS will only have to carry extra liquid methane when going to and from the moon.  However, if they can find enough lunar ice, they may be able to make liquid methane also, but carbon would be needed from somewhere.
Not necessary, though. If fully refueled in LEO, ITS can fly to the Moon's surface and back to Earth (though not with much margin). Works even better if you refuel at a higher orbit.
Title: Re: ITS Development Updates and Discussion Thread
Post by: Robotbeat on 06/12/2017 04:57 pm
Rockets are designed to barely stand themselves upright in 1 g unpressurized. Flight loads of any kind will require pressurization to some level.

John

I understand this. But: Does this really apply to the ITS space ship?
It has to survive reentry from interplanetary speeds, so it has to have some significant structural strength, doesn't it? Shouldn't we compare it to the STS Orbiter?
And unlike Shuttle, it'd get a significant proportion of its structural strength from pressurization.
Title: Re: ITS Development Updates and Discussion Thread
Post by: matthewkantar on 06/12/2017 05:43 pm
I often think of the Shuttle's weight when trying to grasp ITS. ITS cannot be anywhere near as dense as the Shuttle, that was one heavy space ship.  Rentry it what is essentially a ballon seems dangerous. I guess they have been doing reentry light with Falcon stages pressurized, but the heat loads for an ITS returning from Mars would be off the charts.

Matthew
Title: Re: ITS Development Updates and Discussion Thread
Post by: Kansan52 on 06/12/2017 05:50 pm
Maybe bots that work outs ide like in 'Silent Running'?
Title: Re: ITS Development Updates and Discussion Thread
Post by: hkultala on 06/12/2017 06:14 pm
Rockets are designed to barely stand themselves upright in 1 g unpressurized. Flight loads of any kind will require pressurization to some level.

John

I understand this. But: Does this really apply to the ITS space ship?
It has to survive reentry from interplanetary speeds, so it has to have some significant structural strength, doesn't it?

The g-loads should not be very high, and the structural loads should be much smaller on re-entry than liftoff because the total weight of the craft is much less, tanks are almost empty, carrying only the fuel needed for landing.

Though thermal loads should be very high, but PICA-X seems to be quite good heat shield material.

Title: Re: ITS Development Updates and Discussion Thread
Post by: livingjw on 06/12/2017 07:08 pm
Rockets are designed to barely stand themselves upright in 1 g unpressurized. Flight loads of any kind will require pressurization to some level.

John

I understand this. But: Does this really apply to the ITS space ship?
It has to survive reentry from interplanetary speeds, so it has to have some significant structural strength, doesn't it? Shouldn't we compare it to the STS Orbiter?

It does apply to the ITS space ship since a pressure stabilized tank structure is lighter than one that is not pressurized. Here I am talking about just enough pressure to avoid structural buckling.  The Falcon 9 S1 is pressurized for a couple of reasons. 1) so the engines can light, and 2) to provide structural stability for reentry. ITS will only be different in that it will be covered with TPS to survive reentry.

John
Title: Re: ITS Development Updates and Discussion Thread
Post by: M.E.T. on 06/12/2017 09:53 pm
Yes, if they can make LOX on the moon's surface, ITS will only have to carry extra liquid methane when going to and from the moon.  However, if they can find enough lunar ice, they may be able to make liquid methane also, but carbon would be needed from somewhere.
Not necessary, though. If fully refueled in LEO, ITS can fly to the Moon's surface and back to Earth (though not with much margin). Works even better if you refuel at a higher orbit.

How about flying an ITS tanker along for a Moon trip? Would a single tanker help with the margins at all? My thinking is you refuel in Earth orbit, then send both ships to land on the Moon. The tanker filled with fuel and the spaceship with people and equipment.

Would the tanker have enough fuel to get both ships back to Earth, on top of the fuel left in each ship's tanks?
Title: Re: ITS Development Updates and Discussion Thread
Post by: Kenp51d on 06/12/2017 10:07 pm
Would be better to leave the tanker in lunar orbit.

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Title: Re: ITS Development Updates and Discussion Thread
Post by: M.E.T. on 06/12/2017 10:11 pm
Would be better to leave the tanker in lunar orbit.

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Ah yes. So then the tanker need not expend any fuel landing and taking off again. But that still requires the crew spaceship to land and take off with only the fuel it had on board. But at least it could refuel in Moon orbit for the trip back, and for the landing on Earth.

And presumably, should they somehow have a fuel emergency while on the surface of the Moon, they could always land the tanker and transfer more fuel from it if necessary. Even if the empty tanker has to remain behind until a future tanker can be sent to refuel and recover it.

I'm just not sure how much fuel would be required to launch from the Moon, and whether a single tanker can carry enough to achieve that.
Title: Re: ITS Development Updates and Discussion Thread
Post by: envy887 on 06/13/2017 01:19 am
Don't need the tanker, it's probably not designed for extended operation in deep space or high velocity entry anyway.

Two refueled ITS ships departing LEO can rendezvous in lunar orbit, transfer some fuel, allowing one to land and leave 300 tonnes of cargo. After it launches to another LOR, both can proceed empty to direct Earth entry.

Title: Re: ITS Development Updates and Discussion Thread
Post by: DanielW on 06/13/2017 01:47 am
Don't need the tanker, it's probably not designed for extended operation in deep space or high velocity entry anyway.

The tanker will be nearly identical externally. You just move the bulkheads to take up more space. Also the tanker is part of the ITS System. If you want the "go anywhere" ability that was advertised then your tankers need to go anywhere as well.
Title: Re: ITS Development Updates and Discussion Thread
Post by: envy887 on 06/13/2017 02:04 am
Don't need the tanker, it's probably not designed for extended operation in deep space or high velocity entry anyway.

The tanker will be nearly identical externally. You just move the bulkheads to take up more space. Also the tanker is part of the ITS System. If you want the "go anywhere" ability that was advertised then your tankers need to go anywhere as well.
LEO is halfway to anywhere, that's as far as the tankers need to go. Past that, it's cheaper to send the interplanetary ship in a tanker role.
Title: Re: ITS Development Updates and Discussion Thread
Post by: jpo234 on 06/13/2017 07:06 am
The tanker will be nearly identical externally. You just move the bulkheads to take up more space. Also the tanker is part of the ITS System. If you want the "go anywhere" ability that was advertised then your tankers need to go anywhere as well.

I thought the engine arrangements differ. Am I wrong?
Title: Re: ITS Development Updates and Discussion Thread
Post by: livingjw on 06/13/2017 11:18 am
The tanker will be nearly identical externally. You just move the bulkheads to take up more space. Also the tanker is part of the ITS System. If you want the "go anywhere" ability that was advertised then your tankers need to go anywhere as well.

I thought the engine arrangements differ. Am I wrong?

The engine arrangements are the same.

John
Title: Re: ITS Development Updates and Discussion Thread
Post by: DanielW on 06/13/2017 02:22 pm
Don't need the tanker, it's probably not designed for extended operation in deep space or high velocity entry anyway.

The tanker will be nearly identical externally. You just move the bulkheads to take up more space. Also the tanker is part of the ITS System. If you want the "go anywhere" ability that was advertised then your tankers need to go anywhere as well.
LEO is halfway to anywhere, that's as far as the tankers need to go. Past that, it's cheaper to send the interplanetary ship in a tanker role.

It is a fun saying, but I don't think it is true. If this chart is correct. http://i.imgur.com/SqdzxzF.png (http://i.imgur.com/SqdzxzF.png) then the surface of Europa is 17.5 Km/s away from LEO. You will want tankers based there along with a propellant plant to help bring you in.
Title: Re: ITS Development Updates and Discussion Thread
Post by: TheKutKu on 06/13/2017 02:30 pm
If you can manage to do some aerobraking with multiple passes (either with a larger heat shield or with a magnetic heat shield) you can go to europa with about 14.5 km/s of dV.
Title: Re: ITS Development Updates and Discussion Thread
Post by: envy887 on 06/13/2017 03:33 pm
Don't need the tanker, it's probably not designed for extended operation in deep space or high velocity entry anyway.

The tanker will be nearly identical externally. You just move the bulkheads to take up more space. Also the tanker is part of the ITS System. If you want the "go anywhere" ability that was advertised then your tankers need to go anywhere as well.
LEO is halfway to anywhere, that's as far as the tankers need to go. Past that, it's cheaper to send the interplanetary ship in a tanker role.

It is a fun saying, but I don't think it is true. If this chart is correct. http://i.imgur.com/SqdzxzF.png (http://i.imgur.com/SqdzxzF.png) then the surface of Europa is 17.5 Km/s away from LEO. You will want tankers based there along with a propellant plant to help bring you in.

Since they have to push the tanker through 94 km/s total delta-v just to refuel 1 ITS ship, SpaceX will mass-optimize that thing to the bone. MMOD shields, solar panels, interplanetary entry heatshields, etc are all useless dead mass if your primary mission only requires about 24 hours in LEO before landing. Think F9 upper stage on a bigger scale: that's the paradigm for the tanker.

If they have BLEO missions that require extra propellant, the easiest thing to do is send additional ITS ships. Maybe they will eventually do a deep-space version of the tanker, but it's not a priority from anything I've seen.
Title: Re: ITS Development Updates and Discussion Thread
Post by: M.E.T. on 06/13/2017 05:02 pm
Don't need the tanker, it's probably not designed for extended operation in deep space or high velocity entry anyway.

The tanker will be nearly identical externally. You just move the bulkheads to take up more space. Also the tanker is part of the ITS System. If you want the "go anywhere" ability that was advertised then your tankers need to go anywhere as well.
LEO is halfway to anywhere, that's as far as the tankers need to go. Past that, it's cheaper to send the interplanetary ship in a tanker role.

It is a fun saying, but I don't think it is true. If this chart is correct. http://i.imgur.com/SqdzxzF.png (http://i.imgur.com/SqdzxzF.png) then the surface of Europa is 17.5 Km/s away from LEO. You will want tankers based there along with a propellant plant to help bring you in.

Since they have to push the tanker through 94 km/s total delta-v just to refuel 1 ITS ship, SpaceX will mass-optimize that thing to the bone. MMOD shields, solar panels, interplanetary entry heatshields, etc are all useless dead mass if your primary mission only requires about 24 hours in LEO before landing. Think F9 upper stage on a bigger scale: that's the paradigm for the tanker.

If they have BLEO missions that require extra propellant, the easiest thing to do is send additional ITS ships. Maybe they will eventually do a deep-space version of the tanker, but it's not a priority from anything I've seen.

How would an additional ITS ship transport excess fuel? Would part of its interior storage be converted into tanks or something along those lines?
Title: Re: ITS Development Updates and Discussion Thread
Post by: envy887 on 06/13/2017 05:49 pm
How would an additional ITS ship transport excess fuel? Would part of its interior storage be converted into tanks or something along those lines?

Probably in the main propellant tanks. If it's not carrying any payload (i.e. dedicated to the tanker role) it can use less propellant to burn through the same delta-v, leaving excess propellant to share with the ship that is carrying payload.
Title: Re: ITS Development Updates and Discussion Thread
Post by: guckyfan on 06/13/2017 05:55 pm
How would an additional ITS ship transport excess fuel? Would part of its interior storage be converted into tanks or something along those lines?

Probably in the main propellant tanks. If it's not carrying any payload (i.e. dedicated to the tanker role) it can use less propellant to burn through the same delta-v, leaving excess propellant to share with the ship that is carrying payload.

I can not see how this could be more efficient than a slightly modified tanker for BLEO operations.
Title: Re: ITS Development Updates and Discussion Thread
Post by: rsdavis9 on 06/13/2017 07:02 pm
How would an additional ITS ship transport excess fuel? Would part of its interior storage be converted into tanks or something along those lines?

Probably in the main propellant tanks. If it's not carrying any payload (i.e. dedicated to the tanker role) it can use less propellant to burn through the same delta-v, leaving excess propellant to share with the ship that is carrying payload.


I can not see how this could be more efficient than a slightly modified tanker for BLEO operations.

Well if you eliminate the payload and associated baggage the extra performance would translate to excess fuel. But without knowing:
1. dry weight
2. fuel load
3. isp of engines

we have no way of knowing if the ITS could carry more fuel if they stretch the tanks or put extra tanks where the payload was.

But my WAG based on numbers thrown around here is that they could carry extra fuel in either stretched tanks of extra tanks.

Title: Re: ITS Development Updates and Discussion Thread
Post by: Robotbeat on 06/13/2017 07:21 pm
You don't need to go all the way to lunar orbit. Just a somewhat higher-than-LEO elliptical orbit would be plenty. A tanker could do that no problem.
Title: Re: ITS Development Updates and Discussion Thread
Post by: livingjw on 06/13/2017 08:04 pm
I don't understand this discussion of the ITS and its Tanker Variant. From what we have been told, their outer mold lines will be identical. TPS will probably be very similar if not the same as will propulsion. So , I take it, you guys are arguing over the interior layout of the tanks and whether any additional propellant temperature management will be needed for long term storage?

John
Title: Re: ITS Development Updates and Discussion Thread
Post by: envy887 on 06/13/2017 08:26 pm
You don't need to go all the way to lunar orbit. Just a somewhat higher-than-LEO elliptical orbit would be plenty. A tanker could do that no problem.

Hmm, that is actually plenty. Refueling at about LEO+1700 m/s allows the ITS ship to deliver 300 tonnes on the moon and return empty. Not sending the tanker through TLI, LOI, and TEI saves 2 ITS launches and ups the per-launch payload delivered from 27.3t to 33.3t. The tanker has to aerobrake from 9450 m/s instead of 7750 m/s, but that probably just shortens the life of the heat shield, and it can do multiple passes if the heating rate is too high.

I wonder if the Ship and Tanker can cross-feed for part of TLI? :D
Title: Re: ITS Development Updates and Discussion Thread
Post by: M.E.T. on 06/13/2017 08:37 pm
You don't need to go all the way to lunar orbit. Just a somewhat higher-than-LEO elliptical orbit would be plenty. A tanker could do that no problem.

Hmm, that is actually plenty. Refueling at about LEO+1700 m/s allows the ITS ship to deliver 300 tonnes on the moon and return empty. Not sending the tanker through TLI, LOI, and TEI saves 2 ITS launches and ups the per-launch payload delivered from 27.3t to 33.3t. The tanker has to aerobrake from 9450 m/s instead of 7750 m/s, but that probably just shortens the life of the heat shield, and it can do multiple passes if the heating rate is too high.

I wonder if the Ship and Tanker can cross-feed for part of TLI? :D

Envy887

Always appreciate your posts. I've learnt so much from your contributions.

In this case, are you agreeing or disagreeing with Robotbeat? Also, when you say "refuelling at LEO+1700m/s", do you mean just 1 tanker's worth of refuelling, or the full refuelling as for the Mars trip where 5 tankers are required?

Also, what do you mean by the 33.3t payload per launch when you also said that the payload to the Moon is 300t?
Title: Re: ITS Development Updates and Discussion Thread
Post by: envy887 on 06/13/2017 08:50 pm
You don't need to go all the way to lunar orbit. Just a somewhat higher-than-LEO elliptical orbit would be plenty. A tanker could do that no problem.

Hmm, that is actually plenty. Refueling at about LEO+1700 m/s allows the ITS ship to deliver 300 tonnes on the moon and return empty. Not sending the tanker through TLI, LOI, and TEI saves 2 ITS launches and ups the per-launch payload delivered from 27.3t to 33.3t. The tanker has to aerobrake from 9450 m/s instead of 7750 m/s, but that probably just shortens the life of the heat shield, and it can do multiple passes if the heating rate is too high.

I wonder if the Ship and Tanker can cross-feed for part of TLI? :D

Envy887

Always appreciate your posts. I've learnt so much from your contributions.

In this case, are you agreeing or disagreeing with Robotbeat?
Agreeing

Quote
Also, when you say "refuelling at LEO+1700m/s", do you mean just 1 tanker's worth of refuelling, or the full refuelling as for the Mars trip where 5 tankers are required?
More like "topping off" the Ship's tanks. It will burn ~915 tonnes of prop to get to LEO+1700 m/s, so the Tanker needs to bring that much along. From there the Ship can proceed with full tanks through the rest of TLI while the Tanker reenters a couple hours later at the next perigee.
Quote

Also, what do you mean by the 33.3t payload per launch when you also said that the payload to the Moon is 300t?
The Ship needs to be launched and then fully refueled in LEO, which requires 6 launches, plus the Tanker needs to be launched and partially fueled in LEO requiring 4 more launches... so actually that should be 10 launches per 300 tonnes delivered, or 30t per launch. This is still pretty efficient: Saturn V only delivered 1 to 2 tonnes or so per launch, depending what you count as "delivered" payload (crew, science packages, lunar rover, etc).
Title: Re: ITS Development Updates and Discussion Thread
Post by: M.E.T. on 06/13/2017 08:58 pm
You don't need to go all the way to lunar orbit. Just a somewhat higher-than-LEO elliptical orbit would be plenty. A tanker could do that no problem.

Hmm, that is actually plenty. Refueling at about LEO+1700 m/s allows the ITS ship to deliver 300 tonnes on the moon and return empty. Not sending the tanker through TLI, LOI, and TEI saves 2 ITS launches and ups the per-launch payload delivered from 27.3t to 33.3t. The tanker has to aerobrake from 9450 m/s instead of 7750 m/s, but that probably just shortens the life of the heat shield, and it can do multiple passes if the heating rate is too high.

I wonder if the Ship and Tanker can cross-feed for part of TLI? :D

Envy887

Always appreciate your posts. I've learnt so much from your contributions.

In this case, are you agreeing or disagreeing with Robotbeat?
Agreeing

Quote
Also, when you say "refuelling at LEO+1700m/s", do you mean just 1 tanker's worth of refuelling, or the full refuelling as for the Mars trip where 5 tankers are required?
More like "topping off" the Ship's tanks. It will burn ~915 tonnes of prop to get to LEO+1700 m/s, so the Tanker needs to bring that much along. From there the Ship can proceed with full tanks through the rest of TLI while the Tanker reenters a couple hours later at the next perigee.
Quote

Also, what do you mean by the 33.3t payload per launch when you also said that the payload to the Moon is 300t?
The Ship needs to be launched and then fully refueled in LEO, which requires 6 launches, plus the Tanker needs to be launched and partially fueled in LEO requiring 4 more launches... so actually that should be 10 launches per 300 tonnes delivered, or 30t per launch. This is still pretty efficient: Saturn V only delivered 1 to 2 tonnes or so per launch, depending what you count as "delivered" payload (crew, science packages, lunar rover, etc).

And are these 10 launches for 300 tons delivered to the Moon then more efficient than just 6 launches required for refuelling in LEO? (edit for clarification) As in the case of the Mars voyage, which presumably refuels at a lower orbit, but only requires 6 launches.                                                                                                           
Title: Re: ITS Development Updates and Discussion Thread
Post by: envy887 on 06/13/2017 09:09 pm
And are these 10 launches for 300 tons delivered to the Moon then more efficient than just 6 launches required for refuelling in LEO?                                                                                                           

Yes. If you only launch 6 times (Ship +5 refueling tankers), the delivered payload is more like 10 tonnes, or 0.6 tonnes per launch. This is because a fully fueled ship in LEO (2100 tonnes) just barely has enough delta-v to go to the surface of the Moon and back with no payload (I use 10,000 m/s to account for margins and Earth EDL).

Using the tanker lets it "stage" well above LEO, and staging really helps efficiency when it needs this much delta-v.

Sitting down with a delta-v map and calculator and working through these scenarios can be enlightening:

http://i.imgur.com/SqdzxzF.png
http://www.strout.net/info/science/delta-v/

As in the case of the Mars voyage, which presumably refuels at a lower orbit, but only requires 6 launches.                                                                                                           

The Mars surface is in practice only ~4500 m/s away from LEO. Moon-and-back is much, much harder.
Title: Re: ITS Development Updates and Discussion Thread
Post by: RoboGoofers on 06/13/2017 09:09 pm
Rockets are designed to barely stand themselves upright in 1 g unpressurized. Flight loads of any kind will require pressurization to some level.

John

Entry loads are obliquely lateral  and concentrated at the front of the ship, which will of course be pressurized because of the passengers. there are also a number of floor bulkheads in the front 40% to stiffen up that part. In the image below you can also see stays or spokes used to hold the landing tanks and pipes in the center. Perhaps the slosh baffles also add lateral rigidity. (i'm not sure if they're typically used that way)

i'm not saying you're wrong but just pointing out what might be other structural features incorporated into the design.
Title: Re: ITS Development Updates and Discussion Thread
Post by: M.E.T. on 06/13/2017 09:20 pm
And are these 10 launches for 300 tons delivered to the Moon then more efficient than just 6 launches required for refuelling in LEO?                                                                                                           

Yes. If you only launch 6 times (Ship +5 refueling tankers), the delivered payload is more like 10 tonnes, or 0.6 tonnes per launch. This is because a fully fueled ship in LEO (2100 tonnes) just barely has enough delta-v to go to the surface of the Moon and back with no payload (I use 10,000 m/s to account for margins and Earth EDL).

Using the tanker lets it "stage" well above LEO, and staging really helps efficiency when it needs this much delta-v.

Sitting down with a delta-v map and calculator and working through these scenarios can be enlightening:

http://i.imgur.com/SqdzxzF.png
http://www.strout.net/info/science/delta-v/

As in the case of the Mars voyage, which presumably refuels at a lower orbit, but only requires 6 launches.                                                                                                           

The Mars surface is in practice only ~4500 m/s away from LEO. Moon-and-back is much, much harder.

Ok, thanks. So, for the cost of 10 ITS launches a 300-ton Moon base could be delivered to the lunar surface. And with every 10 launches thereafter 300 tons of additional supplies could be delivered to expand and support the base.

I can't recall the exact cost per launch of the ITS, but from the above it would seem that a permanent human presence on the Moon would become quite feasible once the ITS is in operation. And probably not at a cost much greater than that of the ISS at the moment.
Title: Re: ITS Development Updates and Discussion Thread
Post by: Kenp51d on 06/13/2017 09:40 pm
How would the tanker requirements be affected if the base after a few resupply missions to it could the supply at least the lox?

Sent from my XT1565 using Tapatalk

Title: Re: ITS Development Updates and Discussion Thread
Post by: envy887 on 06/13/2017 10:22 pm
How would the tanker requirements be affected if the base after a few resupply missions to it could the supply at least the lox?
Then it can deliver 240t with no refueling past LEO. 40t delivered per launch, instead of 30t. Or 50t per launch, if you can make methane too...
Title: Re: ITS Development Updates and Discussion Thread
Post by: guckyfan on 06/14/2017 10:02 am
It is going to be an interesting choice, more tanker flights vs. local propellant production. I think tanker will win until they need a lot of cargo to the moon.
Title: Re: ITS Development Updates and Discussion Thread
Post by: Bynaus on 06/14/2017 03:45 pm
Elon Musk's Mars vision as a text-document, freely available until July 5th.

http://online.liebertpub.com/doi/10.1089/space.2017.29009.emu
Title: Re: ITS Development Updates and Discussion Thread
Post by: oldAtlas_Eguy on 06/14/2017 03:57 pm
It is going to be an interesting choice, more tanker flights vs. local propellant production. I think tanker will win until they need a lot of cargo to the moon.
Until flight rates get very high >50 per year, the costs (no profit added) per launch of tankers ~$50M and the ITS ~$100M the cost of getting 300mt to the surface of the Moon would be around $600M or $2,000/kg. Compared to current lowest costs of $50,000/kg that is a big reduction in the cost of the establishment of a Moon base. Transportation becomes <10% of the costs and most is operations and the hardware development and manufacturing of the hardware being sent to the Moon.

At higher flight rates the costs nearly drop in half to around $300M per 300mt or $1,000/kg. What is shown here is that being able to refuel just LOX on the Moon could decrease the costs significantly if you could produce the LOX at $500/kg then it would be competitive to the use of tankers even at high flight rates. The less flights used for tankers means the more flights that actually deliver payloads to the surface for the same number of launches. At some point in high flight rates the Earth ground infrastructure will become strained at being able to increase its flight rate rate without high capital investments for additional launch/landing sites. By reducing the number of required flights to deliver the payload this then will effectively double the efficiency of the transportation system allowing twice the payload delivered for a given set of Earth infrastructure and assets (pads/BFRs/Tankers/ITSs).

Having Lunar made propellants available at competitive prices could reduce the number of tanker flights even for Mars trips. This would then increase the number of Mars trips per synod and also reduce the costs per trip. The Moon could be a very lucrative business case for mining and some manufacturing/refining of bulk material.

Added: A BTW 300mt at $50,000/kg is $15B.
Title: Re: ITS Development Updates and Discussion Thread
Post by: jpo234 on 06/14/2017 04:11 pm
I would really like to see Janicki's "real Area 51 stuff".

http://www.goskagit.com/news/business/janicki-industries-busy-with-wide-variety-of-projects/article_40d5f91a-3abc-5071-947c-ae792fe79036.html

ITS or SpaceX isn't even mentioned, but they built the ITS tank we know about.
Title: Re: ITS Development Updates and Discussion Thread
Post by: oldAtlas_Eguy on 06/14/2017 04:48 pm
Elon Musk's Mars vision as a text-document, freely available until July 5th.

http://online.liebertpub.com/doi/10.1089/space.2017.29009.emu
Thanks for the document.

There are two interesting items to make note about.

One is the statement that LC39A has a max thrust capability of design >26Mlbf when NASA first designed and built the pad in the 1960's. That is quite an eye opener and negates all the speculation on need of a smaller vehicle in order to fly from LC39A.

The second is the costs at high flight rates data that would suggest what the 11 flight scenario for a 0 Lunar infrastructure Moon delivery of 300+mt would cost.
This is $43M for the ITS launch and another $40M for all the Tankers. That is a total of $83M or just under $300/kg to the surface of the Moon. But the caveat is that this would be significantly later than the initial flights.
My estimates are very conservative for this system vs the ones supplied by SpaceX/Musk. I do not doubt that SpaceX will eventually reach their goals on costs but the problem is how long will take once ITS is flying to get there.
Title: Re: ITS Development Updates and Discussion Thread
Post by: Blackstar on 06/14/2017 04:55 pm
Elon Musk's Mars vision as a text-document, freely available until July 5th.

http://online.liebertpub.com/doi/10.1089/space.2017.29009.emu

Here is the document, attached.
Title: Re: ITS Development Updates and Discussion Thread
Post by: envy887 on 06/14/2017 05:23 pm
Elon Musk's Mars vision as a text-document, freely available until July 5th.

http://online.liebertpub.com/doi/10.1089/space.2017.29009.emu
Thanks for the document.

There are two interesting items to make note about.

One is the statement that LC39A has a max thrust capability of design >26Mlbf when NASA first designed and built the pad in the 1960's. That is quite an eye opener and negates all the speculation on need of a smaller vehicle in order to fly from LC39A.

The second is the costs at high flight rates data that would suggest what the 11 flight scenario for a 0 Lunar infrastructure Moon delivery of 300+mt would cost.
This is $43M for the ITS launch and another $40M for all the Tankers. That is a total of $83M or just under $300/kg to the surface of the Moon. But the caveat is that this would be significantly later than the initial flights.
My estimates are very conservative for this system vs the ones supplied by SpaceX/Musk. I do not doubt that SpaceX will eventually reach their goals on costs but the problem is how long will take once ITS is flying to get there.

The quote on thrust max for LC-39A:

Quote
Figure 9 gives you a more direct comparison. The thrust level
is enormous. We are talking about a lift-off thrust of 13,000
tons, so it will be quite tectonic when it takes off. However, it
does fit on Pad 39A, which NASA has been kind enough to allow
us to use because they oversized the pad in doing Saturn V. As a
result, we can use a much larger vehicle on that same launchpad.

In the future, we expect to add additional launch locations,
probably adding one on the south coast of Texas, but this gives
you a sense of the relative capability
Title: Re: ITS Development Updates and Discussion Thread
Post by: TomH on 06/16/2017 03:17 am
Newsweek article re. the paper:
http://www.newsweek.com/elon-musk-mars-spacex-martian-city-625994
Title: Re: ITS Development Updates and Discussion Thread
Post by: Robotbeat on 06/16/2017 03:21 am
Nothing new here, but both seem to have been released today:

Released by EM, summary of last year's presentation:
http://online.liebertpub.com/doi/10.1089/space.2017.29009.emu

Newsweek article re. above paper:
http://www.newsweek.com/elon-musk-mars-spacex-martian-city-625994
Indeed, that journal article was already posted multiple times in this thread, including the post immediately before yours...
Title: Re: ITS Development Updates and Discussion Thread
Post by: Patchouli on 06/16/2017 06:22 am


The Mars surface is in practice only ~4500 m/s away from LEO. Moon-and-back is much, much harder.


ITS is to use fast transfer trajectory vs the typical Hohmann transfer and since it doesn't use parachutes it has decelerate propulsively from mach 2+ after reentry.
Title: Re: ITS Development Updates and Discussion Thread
Post by: envy887 on 06/16/2017 01:59 pm


The Mars surface is in practice only ~4500 m/s away from LEO. Moon-and-back is much, much harder.


ITS is to use fast transfer trajectory vs the typical Hohmann transfer and since it doesn't use parachutes it has decelerate propulsively from mach 2+ after reentry.
I was comparing minimum energy trajectories for Moon and Mars, with propulsive landing. Even a fast transit to Mars with landing is much easier than a MOON landing and return.

Edit: spelling
Title: Re: ITS Development Updates and Discussion Thread
Post by: Kenp51d on 06/16/2017 04:32 pm


The Mars surface is in practice only ~4500 m/s away from LEO. Moon-and-back is much, much harder.


ITS is to use fast transfer trajectory vs the typical Hohmann transfer and since it doesn't use parachutes it has decelerate propulsively from mach 2+ after reentry.
I was comparing minimum energy trajectories for Moon and Mars, with propulsive landing. Even a fast transit to Mars with landing is much easier than a Month landing and return.
Is Mars easier because of making return fuel on Mars but not on the moon (at least not right away)?
If you make fuel on both or not on either does that change which is easier?

Sent from my XT1565 using Tapatalk

Title: Re: ITS Development Updates and Discussion Thread
Post by: M.E.T. on 06/16/2017 04:44 pm


The Mars surface is in practice only ~4500 m/s away from LEO. Moon-and-back is much, much harder.


ITS is to use fast transfer trajectory vs the typical Hohmann transfer and since it doesn't use parachutes it has decelerate propulsively from mach 2+ after reentry.
I was comparing minimum energy trajectories for Moon and Mars, with propulsive landing. Even a fast transit to Mars with landing is much easier than a Month landing and return.
Is Mars easier because of making return fuel on Mars but not on the moon (at least not right away)?
If you make fuel on both or not on either does that change which is easier?

Sent from my XT1565 using Tapatalk

Mars is easier because it has an atmosphere which takes care of a portion of the required deceleration during landing, while the Moon has very little atmosphere, meaning you need to carry more fuel for deceleration and landing.

There may be other factors which make the Moon more difficult, but this is the main issue I'm aware of.
Title: Re: ITS Development Updates and Discussion Thread
Post by: Navier–Stokes on 06/16/2017 05:43 pm
Quote from: https://twitter.com/elonmusk/status/875770056323420160
Elon Musk‏ @elonmusk 

Mars V2 plan coming soon, which I think addresses the most fundamental flaw in V1: how to pay for development & operation of giant rockets

Quote from: https://twitter.com/sciam/status/875756138121310208
Scientific American @sciam
Elon Musk publishes plans for colonizing Mars http://bit.ly/2rE8DSJ 
10:40 AM - 16 Jun 2017
Title: Re: ITS Development Updates and Discussion Thread
Post by: Johnnyhinbos on 06/16/2017 05:44 pm
Musk's new tweet on the subject...

"Mars V2 plan coming soon, which I think addresses the most fundamental flaw in V1: how to pay for development & operation of giant rockets "

https://twitter.com/elonmusk/status/875770056323420160

EDIT: Ninja'd!
Title: Re: ITS Development Updates and Discussion Thread
Post by: oldAtlas_Eguy on 06/16/2017 07:06 pm
I think this update on details of ITS funding is a outgrowth of the actual costs that reusability of F9/FH is working out to be. Also these costs for reusable F9/FH also feed into the cost of deployment of the 'CommX" constellation and the possible profits from the constellation.

Then the final item is what funding is needed for what tasks during the development detailing how much funds are needed and when.
Title: Re: ITS Development Updates and Discussion Thread
Post by: AncientU on 06/16/2017 07:21 pm
IMO, it is an outgrowth of their needing to go it alone for several more years due to the entrenched interests in SLS/Orion.  Having a couple launch failures and lengthy stand downs, plus covering the tab for rebuilding LC-40, finishing LC-39A, building Boca Chica, and developing reusable rocket technology has made cash flow a central management issue, judging on how often they (EM and GS) have mentioned it since the AMOS failure.

They need to show that the Mars effort is real, not fantasy, which means making/launching something big soonest.  Once a Saturn V/SLS Block 2 class reusable vehicle is flying, NASA and the world will see an exploration path that is more affordable and capable than anything SLS/Orion will ever offer.  A public-private partnership may finally result -- if not, then they will be strategically positioned to continue going it alone.
Title: Re: ITS Development Updates and Discussion Thread
Post by: M.E.T. on 06/16/2017 08:12 pm
IMO, it is an outgrowth of their needing to go it alone for several more years due to the entrenched interests in SLS/Orion.  Having a couple launch failures and lengthy stand downs, plus covering the tab for rebuilding LC-40, finishing LC-39A, building Boca Chica, and developing reusable rocket technology has made cash flow a central management issue, judging on how often they (EM and GS) have mentioned it since the AMOS failure.

They need to show that the Mars effort is real, not fantasy, which means making/launching something big soonest.  Once a Saturn V/SLS Block 2 class reusable vehicle is flying, NASA and the world will see an exploration path that is more affordable and capable than anything SLS/Orion will ever offer.  A public-private partnership may finally result -- if not, then they will be strategically positioned to continue going it alone.

Ok, so in practice, does that involve an intermediate SLS class SpaceX rocket being developed first, with ITS being pushed out another 10 years?
Title: Re: ITS Development Updates and Discussion Thread
Post by: RonM on 06/16/2017 08:17 pm
IMO, it is an outgrowth of their needing to go it alone for several more years due to the entrenched interests in SLS/Orion.  Having a couple launch failures and lengthy stand downs, plus covering the tab for rebuilding LC-40, finishing LC-39A, building Boca Chica, and developing reusable rocket technology has made cash flow a central management issue, judging on how often they (EM and GS) have mentioned it since the AMOS failure.

They need to show that the Mars effort is real, not fantasy, which means making/launching something big soonest.  Once a Saturn V/SLS Block 2 class reusable vehicle is flying, NASA and the world will see an exploration path that is more affordable and capable than anything SLS/Orion will ever offer.  A public-private partnership may finally result -- if not, then they will be strategically positioned to continue going it alone.

Ok, so in practice, does that involve an intermediate SLS class SpaceX rocket being developed first, with ITS being pushed out another 10 years?

Think of it as a first generation ITS geared towards exploration missions. The full-sized ITS can come later when colonization begins.
Title: Re: ITS Development Updates and Discussion Thread
Post by: Ludus on 06/16/2017 10:56 pm
IMO, it is an outgrowth of their needing to go it alone for several more years due to the entrenched interests in SLS/Orion.  Having a couple launch failures and lengthy stand downs, plus covering the tab for rebuilding LC-40, finishing LC-39A, building Boca Chica, and developing reusable rocket technology has made cash flow a central management issue, judging on how often they (EM and GS) have mentioned it since the AMOS failure.

They need to show that the Mars effort is real, not fantasy, which means making/launching something big soonest.  Once a Saturn V/SLS Block 2 class reusable vehicle is flying, NASA and the world will see an exploration path that is more affordable and capable than anything SLS/Orion will ever offer.  A public-private partnership may finally result -- if not, then they will be strategically positioned to continue going it alone.

Ok, so in practice, does that involve an intermediate SLS class SpaceX rocket being developed first, with ITS being pushed out another 10 years?

In the recent paper, Musk makes it clear that the ITS Spaceship will be built first and tested on suborbital flights on its own. The Booster is regarded as much like a big version of an F9 and easier. The spaceship is also mentioned as effectively a transcontinental hypersonic transport on its own. It's mentioned that other than from earth which requires the Booster, the spaceship is capable of SSTO performance on Mars and most other destinations in the Solar System. I don't think they have any interest in anything smaller. Given the design with a lot of engines, just using fewer engines or somewhat smaller tanks doesn't really save much cost.
Title: Re: ITS Development Updates and Discussion Thread
Post by: Robotbeat on 06/16/2017 11:16 pm
IMO, it is an outgrowth of their needing to go it alone for several more years due to the entrenched interests in SLS/Orion.  Having a couple launch failures and lengthy stand downs, plus covering the tab for rebuilding LC-40, finishing LC-39A, building Boca Chica, and developing reusable rocket technology has made cash flow a central management issue, judging on how often they (EM and GS) have mentioned it since the AMOS failure.

They need to show that the Mars effort is real, not fantasy, which means making/launching something big soonest.  Once a Saturn V/SLS Block 2 class reusable vehicle is flying, NASA and the world will see an exploration path that is more affordable and capable than anything SLS/Orion will ever offer.  A public-private partnership may finally result -- if not, then they will be strategically positioned to continue going it alone.

Ok, so in practice, does that involve an intermediate SLS class SpaceX rocket being developed first, with ITS being pushed out another 10 years?

In the recent paper, Musk makes it clear that the ITS Spaceship will be built first and tested on suborbital flights on its own. The Booster is regarded as much like a big version of an F9 and easier. The spaceship is also mentioned as effectively a transcontinental hypersonic transport on its own. It's mentioned that other than from earth which requires the Booster, the spaceship is capable of SSTO performance on Mars and most other destinations in the Solar System. I don't think they have any interest in anything smaller. Given the design with a lot of engines, just using fewer engines or somewhat smaller tanks doesn't really save much cost.
The content of the paper is almost a year old. It doesn't include any of the newer thinking.
Title: Re: ITS Development Updates and Discussion Thread
Post by: Ludus on 06/17/2017 04:03 pm
IMO, it is an outgrowth of their needing to go it alone for several more years due to the entrenched interests in SLS/Orion.  Having a couple launch failures and lengthy stand downs, plus covering the tab for rebuilding LC-40, finishing LC-39A, building Boca Chica, and developing reusable rocket technology has made cash flow a central management issue, judging on how often they (EM and GS) have mentioned it since the AMOS failure.

They need to show that the Mars effort is real, not fantasy, which means making/launching something big soonest.  Once a Saturn V/SLS Block 2 class reusable vehicle is flying, NASA and the world will see an exploration path that is more affordable and capable than anything SLS/Orion will ever offer.  A public-private partnership may finally result -- if not, then they will be strategically positioned to continue going it alone.

Ok, so in practice, does that involve an intermediate SLS class SpaceX rocket being developed first, with ITS being pushed out another 10 years?

In the recent paper, Musk makes it clear that the ITS Spaceship will be built first and tested on suborbital flights on its own. The Booster is regarded as much like a big version of an F9 and easier. The spaceship is also mentioned as effectively a transcontinental hypersonic transport on its own. It's mentioned that other than from earth which requires the Booster, the spaceship is capable of SSTO performance on Mars and most other destinations in the Solar System. I don't think they have any interest in anything smaller. Given the design with a lot of engines, just using fewer engines or somewhat smaller tanks doesn't really save much cost.
The content of the paper is almost a year old. It doesn't include any of the newer thinking.

Is there any newer thinking by SpaceX out in the last year? I know Musk is promising an update.
Title: Re: ITS Development Updates and Discussion Thread
Post by: Long EZ on 06/17/2017 04:58 pm
A thought that I had the other day was how to fix holes in the ITS spacecraft. How about a quad-copter type of device inside of the LOX and methane tanks. If there is a leak it could quickly fly to the spot and apply some kind of patch on the inside. Patches could be either a tapered spike or a flat patch. Have some way to have some glue on them. This would be used during coast so the copter would be flying in zero-g. You would need a docking station inside the tank for it to stay at when not in use. This would secure it during acceleration. The holes that I am thinking of would be due to meteorites, but maybe those are rare enough that this would not be needed. I hope this is a new idea!
Title: Re: ITS Development Updates and Discussion Thread
Post by: flyright on 06/17/2017 05:07 pm
A thought that I had the other day was how to fix holes in the ITS spacecraft. How about a quad-copter type of device inside of the LOX and methane tanks. If there is a leak it could quickly fly to the spot and apply some kind of patch on the inside. Patches could be either a tapered spike or a flat patch. Have some way to have some glue on them. This would be used during coast so the copter would be flying in zero-g. You would need a docking station inside the tank for it to stay at when not in use. This would secure it during acceleration. The holes that I am thinking of would be due to meteorites, but maybe those are rare enough that this would not be needed. I hope this is a new idea!

Interesting idea. Such a device might look more like the SPHERES experiments on the ISS rather than like a quad-copter. Probably could be used outside the ITS during cruise for TPS inspection and possibly very minor repairs.
Title: Re: ITS Development Updates and Discussion Thread
Post by: Ictogan on 06/17/2017 06:04 pm
A thought that I had the other day was how to fix holes in the ITS spacecraft. How about a quad-copter type of device inside of the LOX and methane tanks. If there is a leak it could quickly fly to the spot and apply some kind of patch on the inside. Patches could be either a tapered spike or a flat patch. Have some way to have some glue on them. This would be used during coast so the copter would be flying in zero-g. You would need a docking station inside the tank for it to stay at when not in use. This would secure it during acceleration. The holes that I am thinking of would be due to meteorites, but maybe those are rare enough that this would not be needed. I hope this is a new idea!
Nice idea, but it has a lot of engineering challenges and risks attached to it. First thing I can think of, what happens if the fixing device fails? I imagine that you really wouldn't want something just floating around loosely inside your methane/lox tanks when you are igniting the engines.
Title: Re: ITS Development Updates and Discussion Thread
Post by: flyright on 06/17/2017 06:26 pm
A thought that I had the other day was how to fix holes in the ITS spacecraft. How about a quad-copter type of device inside of the LOX and methane tanks. If there is a leak it could quickly fly to the spot and apply some kind of patch on the inside. Patches could be either a tapered spike or a flat patch. Have some way to have some glue on them. This would be used during coast so the copter would be flying in zero-g. You would need a docking station inside the tank for it to stay at when not in use. This would secure it during acceleration. The holes that I am thinking of would be due to meteorites, but maybe those are rare enough that this would not be needed. I hope this is a new idea!
Nice idea, but it has a lot of engineering challenges and risks attached to it. First thing I can think of, what happens if the fixing device fails? I imagine that you really wouldn't want something just floating around loosely inside your methane/lox tanks when you are igniting the engines.

Another risk is that the fixing device might create debris. Of course, it might also be able to find and collect debris in the tank.

Like Long EZ said, maybe having holes punched in the tank by meteoroids are rare and this would not be needed.
Title: Re: ITS Development Updates and Discussion Thread
Post by: Robotbeat on 06/17/2017 06:40 pm
It's super rare. Not worth it.
Title: Re: ITS Development Updates and Discussion Thread
Post by: oldAtlas_Eguy on 06/17/2017 06:47 pm
A thought that I had the other day was how to fix holes in the ITS spacecraft. How about a quad-copter type of device inside of the LOX and methane tanks. If there is a leak it could quickly fly to the spot and apply some kind of patch on the inside. Patches could be either a tapered spike or a flat patch. Have some way to have some glue on them. This would be used during coast so the copter would be flying in zero-g. You would need a docking station inside the tank for it to stay at when not in use. This would secure it during acceleration. The holes that I am thinking of would be due to meteorites, but maybe those are rare enough that this would not be needed. I hope this is a new idea!

Interesting idea. Such a device might look more like the SPHERES experiments on the ISS rather than like a quad-copter. Probably could be used outside the ITS during cruise for TPS inspection and possibly very minor repairs.
Because of 2 things: ignition source and heat source. These repair robots would be used when the tanks are at vacuum and are introduced into the tanks through an access port. Also two different robots would be needed. One that used compressed GO2 for propulsion and the other compressed GCH4.

But there is one item that is a positive. Once some partial pressure is introduce by the manuvering cold gass thrusters to position the robot in a centralized location in the tank. The "hole" will cause the robot when it is then put in drift mode will drift to the location of the hole to be repaired.
Title: Re: ITS Development Updates and Discussion Thread
Post by: Robotbeat on 06/17/2017 06:53 pm
This is an off topic idea. Make a new thread for it.
Title: Re: ITS Development Updates and Discussion Thread
Post by: oldAtlas_Eguy on 06/18/2017 03:51 pm
This is an off topic idea. Make a new thread for it.
Created new thread for this type of discussion.
http://forum.nasaspaceflight.com/index.php?topic=43168.new#new (http://forum.nasaspaceflight.com/index.php?topic=43168.new#new)
Title: Re: ITS Development Updates and Discussion Thread
Post by: Ludus on 06/18/2017 05:36 pm
How much of the volume of an ITS Tanker is actually occupied by propellant tanks? It just occurred to me that maybe the Tanker itself is already also a Cargo Variant.

I know that AirForce Tankers actually look pretty much like cargo planes in terms of volume on the inside and can function like that if they weren't in greater demand for their specialized capability. They just can't get off the ground with more fuel than can be contained in space that doesn't impact cargo volume much.

Given the numbers SpaceX provided for how much propellant the Tanker is supposed to deliver, how much cargo volume is left? Since it takes at least 4 loads to fill the tanks I'd assume 25% larger tanks is an upper bound. That ought to leave quite a bit of cargo volume.
Title: Re: ITS Development Updates and Discussion Thread
Post by: Ludus on 06/18/2017 05:56 pm
SpaceX didn't release any detailed renderings of the inside of the Tanker, but presumably it's just like the Heart of Gold but with tanks stretched to whatever the calculated extra propellant load is and a big empty space in the forward area left over.

Wouldn't this Tanker/Cargo ship actually also be the preferred variant for any uncrewed mission like to the outer Solar System that benefits from more propellant? No mention was made of Tankers loading other Tankers in earth orbit before departing for Jupiter but doesn't that make sense?
Title: Re: ITS Development Updates and Discussion Thread
Post by: docmordrid on 06/18/2017 07:08 pm
How much of the volume of an ITS Tanker is actually occupied by propellant tanks? It just occurred to me that maybe the Tanker itself is already also a Cargo Variant.
>

The presentation shows a cargo/propellant split of 300t ship vs 380t for the tanker, so ISTM all or part of the tankers cargo bay has extra tanks.
Title: Re: ITS Development Updates and Discussion Thread
Post by: Ludus on 06/19/2017 03:03 am
How much of the volume of an ITS Tanker is actually occupied by propellant tanks? It just occurred to me that maybe the Tanker itself is already also a Cargo Variant.
>

The presentation shows a cargo/propellant split of 300t ship vs 380t for the tanker, so ISTM all or part of the tankers cargo bay has extra tanks.

In AF Tankers the extra fuel is necessarily in different tanks in the fuselage vs the main wing tanks but in the ITS Tanker I'm assuming for simplicity that they just stretch the two big propellant tanks.

So we know the Tanker carries about 25% more propellant mass than the ship. I'd assume that means all in the two tanks are each about 25% larger. The total of about 500t more propellant (and simpler structure with lower dry mass)results in 80t more of net payload to orbit (as extra propellant).

Visually the tanks are about 50% of the ship volume. So roughly in the Tanker I'd expect them to be 62.5% of the volume if they're stretched 25%.

So I'd expect the rendering of the Tanker to show an empty volume in the forward section of 37.5% or an open cargo space of about a third of the Tanker. So the cargo bay might be a bit shorter or the same as in the space shuttle at say 17m vs 18.5m but much wider, multiple times the volume and many times the potential payload mass. If payload bay doors were depicted on the Tanker they'd open over roughly the same area that has windows in the forward third of the ship.

Of course just like an airborne refueling Tanker ITS Tankers couldn't carry any cargo if they were acting as a Tanker. The forward cargo volume would have to be empty on launch just like the AF Tanker full of fuel. To be used as a cargo variant it would have to be launched with less propellant than its tanks would hold, but then it could carry at least 300t of anything that fits the pretty cavernous forward bay.

Or at least this is what it seems like to me at the moment. I used to assume as you suggest that most of the Tanker volume would be used up. Im interested in understanding where this gets it wrong if it does. It would be kinda cool if SpaceX just needed one Tanker/Cargo type.
Title: Re: ITS Development Updates and Discussion Thread
Post by: AncientU on 06/19/2017 12:04 pm
Could use shorter version for tanker.  Same stretched tanks as you've indicated, but nose section shortened to eliminate empty space.  Same kind of fabrication change as stretching the tanks... Don't need same ballistic coeff as for Mars EDL.  Or windows.
Title: Re: ITS Development Updates and Discussion Thread
Post by: Ludus on 06/19/2017 01:08 pm
Could use shorter version for tanker.  Same stretched tanks as you've indicated, but nose section shortened to eliminate empty space.  Same kind of fabrication change as stretching the tanks... Don't need same ballistic coeff as for Mars EDL.  Or windows.

Yep. But it would give up what seems like a major advantage of a a single type that's both a cargo transport and a tanker,  that could be mass produced. This would be the simple version produced first and represent 90% plus of ITS ships. Unlike with AF Tankers though, it seems like a possible modification.
Title: Re: ITS Development Updates and Discussion Thread
Post by: AncientU on 06/19/2017 05:28 pm
Could use shorter version for tanker.  Same stretched tanks as you've indicated, but nose section shortened to eliminate empty space.  Same kind of fabrication change as stretching the tanks... Don't need same ballistic coeff as for Mars EDL.  Or windows.

Yep. But it would give up what seems like a major advantage of a a single type that's both a cargo transport and a tanker,  that could be mass produced. This would be the simple version produced first and represent 90% plus of ITS ships. Unlike with AF Tankers though, it seems like a possible modification.

Cargo transport and tanker have many different needs, in addition to the larger tankage of the latter.  Since the tankage changes the hull design of the tanker, shortening the bow section and eliminating windows, etc. that are creature comforts, should not be an issue.  Are you suggesting that all vehicles have the oversized tankage so that they are common across the board, but only fly with tanks partially filled?
Title: Re: ITS Development Updates and Discussion Thread
Post by: Kenp51d on 06/19/2017 05:51 pm
Unused tankage would be dead wight.
Don't have a clue how you'd change the ship's profile easely during layup of the CF ship. Different instructions in the machinery that does the work?
Could be simple to build one ship or another ship (profile) on the same production line and machinery. But tend to think it would be real migraine.


Sent from my XT1565 using Tapatalk

Title: Re: ITS Development Updates and Discussion Thread
Post by: Oersted on 06/19/2017 09:21 pm
The whole credo and philosophy behind the ITS is commonality of elements. SpaceX in their published material has shown an absolutely identical hull shape between the tanker and spaceship versions. This simplifies both design, production and certification of the ships. I'm 99% sure there won't be any different hull shape for the tanker version. They'll just send it up a bit more often if needed. After all, the whole concept is based on cheap and trouble-free re-use.
Title: Re: ITS Development Updates and Discussion Thread
Post by: Kenp51d on 06/19/2017 09:43 pm
I don't see them doing but one hull either. Just utilizing internal volume differently. May not be the most efficient, but it is the most economical method.
Good enough to get the job done.

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Title: Re: ITS Development Updates and Discussion Thread
Post by: Kaputnik on 06/19/2017 10:18 pm
It's not currently the norm to short-fuel launch vehicles- I recall something to do with fuel level sensors being one reason why. I would assume that short-fuelling the ITS tanker would be relatively straightforward, but are there any 'gotchas' lurking that could make this trickier than it appears?
Title: Re: ITS Development Updates and Discussion Thread
Post by: Ludus on 06/19/2017 10:33 pm
Could use shorter version for tanker.  Same stretched tanks as you've indicated, but nose section shortened to eliminate empty space.  Same kind of fabrication change as stretching the tanks... Don't need same ballistic coeff as for Mars EDL.  Or windows.

Yep. But it would give up what seems like a major advantage of a a single type that's both a cargo transport and a tanker,  that could be mass produced. This would be the simple version produced first and represent 90% plus of ITS ships. Unlike with AF Tankers though, it seems like a possible modification.

Cargo transport and tanker have many different needs, in addition to the larger tankage of the latter.  Since the tankage changes the hull design of the tanker, shortening the bow section and eliminating windows, etc. that are creature comforts, should not be an issue.  Are you suggesting that all vehicles have the oversized tankage so that they are common across the board, but only fly with tanks partially filled?

I don't think the larger tanks add an important amount of dry mass. I'm not really questioning the pretty cool and romantic design of the "Heart of Gold". I get that it's kind of iconic.

I'm exploring the idea that maybe SpaceX really can get away with just one standard spaceship design, the Tanker/Cargo.

Tanker: leaves the cargo bay empty, fills the propellant tanks.
Cargo: fills the propellant tanks as needed, loads the cargo bay.
Passenger: Drops a BA 2100 (or other self contained life support) and support gear in the cargo bay as appropriate.

SpaceX just needs to build a ship with 6 Raptor engines and 2 carbon composite tanks plus a skin.

Yes. The same Tanker/Cargo ship could flexibly be re tasked to any ITS function. It's just engines and tanks with a cargo bay, a heat shield and landing legs. It would fly with tanks partially filled in the function of earth launch Cargo.
Title: Re: ITS Development Updates and Discussion Thread
Post by: Ludus on 06/19/2017 10:43 pm
Unused tankage would be dead wight.
Don't have a clue how you'd change the ship's profile easely during layup of the CF ship. Different instructions in the machinery that does the work?
Could be simple to build one ship or another ship (profile) on the same production line and machinery. But tend to think it would be real migraine.


Sent from my XT1565 using Tapatalk

The unused tanks would represent a small fraction of 1% of mass at launch, perhaps not worth influencing the rest of the design.

Flexibility to repurpose has a value.
Title: Re: ITS Development Updates and Discussion Thread
Post by: Kenp51d on 06/20/2017 01:09 am
Less than 1%. Wow would never have thought so little.
1%, just let it go with partial filled tanks for such a low penalty. Passenger jets do that all the time.

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Title: Re: ITS Development Updates and Discussion Thread
Post by: Ludus on 06/20/2017 02:36 am
Less than 1%. Wow would never have thought so little.
1%, just let it go with partial filled tanks for such a low penalty. Passenger jets do that all the time.

Sent from my XT1565 using Tapatalk

The dry mass of the entire Tanker is 90t. The propellant at launch is 2500t. At issue is a 25% fraction of Carbon Composite tanks that are themselves a small fraction of the 90t.
Title: Re: ITS Development Updates and Discussion Thread
Post by: guckyfan on 06/20/2017 07:22 am
Increased tank volume may not constitute a major mass penalty. It would take up inner volume that would be very useful for cargo and even more so for passengers. I think they would move bulkheads for increased tank volume.

I also believe what was presented is the first edition. What can be done with minimal development effort. When production volume justifies it, like 5 or more produced per year there is lots of room for some improvements.

A tanker that is 100% tank volume in its body.

Dedicated cargo carriers with large payload doors for infrastructure payloads.

Larger volume ITS that can launch from earth only with minimal or no payload but will be filled by cargo flights and LEO cargo transfer that can land even much larger payload mass on Mars and can come back empty. It could house many more passengers in a passenger version. It could still use the same booster and propulsion unit of ITS.
Title: Re: ITS Development Updates and Discussion Thread
Post by: Ludus on 06/20/2017 03:58 pm
There is something to be said for a more DC-3 like approach. Standardize the design around a basic model and build a lot of them. The Tanker as SpaceX describes it could be a basis for that. It seems like it already is a cargo ship with a huge bay. Just add doors and don't fill the propellant tanks all the way. For most purposes it might be simpler to skip the Fan of extending Solar PV and just put the PV on the whole surface that's not heat shield, similar to Dragon 2.

Unless I'm misunderstanding, the bay would be almost big enough to hold an inflated BA-2100, or a couple deflated. A Tanker could be reloaded in orbit by other Tankers and obviously have more capability than the Heart of Gold since it can carry more propellant.

Most of its uses would be uncrewed but any of them could be converted to passenger carrier by dropping in a Hab like a BA module and whatever else is needed. I'd think there would be major advantages to keeping the designs of life support separate from rockets. As far as Mars, it lets passenger ships to Mars unload and leave all the life support structures before they return. It would be useful in a lot of ways to use the same modules mass produced, iterated and proven for passenger spaceships that go to Mars and space stations in NEO. The experience gained close to home wouldn't just be similar, it would be directly transferred.

My two questions are:

1. Does the Tanker Design as described by SpaceX actually have a large open volume in the forward area that amounts to a ready cargo bay? If so what dimensions?

2. Is this a great opportunity or something to be corrected? Is this flexible multiuse design or inefficiency?

I'd been commenting since Elon's presentation in Mexico that they seemed to be missing a Cargo Variant that was in general utility, the most important if not the sexiest version. It just seemed very cool to me if it had been there all along because the Tanker WAS the Cargo Variant too. It's also likely the first part of the ITS system to be built and fly, before the BFR Booster needed to get it into orbit.
Title: Re: ITS Development Updates and Discussion Thread
Post by: jtrame on 06/20/2017 04:20 pm
A shorter tanker version would still be built on the same line using the same tooling so commonality would still be there.  A short 737 vs. a stretched 737.
Title: Re: ITS Development Updates and Discussion Thread
Post by: guckyfan on 06/20/2017 04:48 pm
There was no description of the tanker. Only data.

Tanker dry mass 90t

Propellant mass, Ship    1950t Cargo 300t
Propellant mass, Tanker 2500t Cargo 380t propellant
Title: Re: ITS Development Updates and Discussion Thread
Post by: Oersted on 06/20/2017 07:55 pm
There was no description of the tanker. Only data.

It was shown attached to the spaceship in the video, which according to Elon was based on actual CAD files of hardware. 
Title: Re: ITS Development Updates and Discussion Thread
Post by: guckyfan on 06/20/2017 08:30 pm
There was no description of the tanker. Only data.

It was shown attached to the spaceship in the video, which according to Elon was based on actual CAD files of hardware.

Yes, but that is only the outer mold line. Not how it looks inside, the tanks.
Title: Re: ITS Development Updates and Discussion Thread
Post by: docmordrid on 06/21/2017 12:19 am
ISTM, if they want to max out commonality they'd empty out the crew hardware and add conformal/inflatable cryotanks (ThinRedLine Aerospace) to the cargo bays & other spaces. Pressurize the compartment to push out the fluids.

https://sbir.gsfc.nasa.gov/SBIR/abstracts/10/sbir/phase1/SBIR-10-1-X5.03-8613.html
Title: Re: ITS Development Updates and Discussion Thread
Post by: Lar on 06/21/2017 02:15 am
Elon Musk's Mars vision as a text-document, freely available until July 5th.

http://online.liebertpub.com/doi/10.1089/space.2017.29009.emu

I missed why it pumpkinizes on the 6th. It reads like a transcript of his talk. I am certainly eager to hear the next update.

A shorter tanker version would still be built on the same line using the same tooling so commonality would still be there.  A short 737 vs. a stretched 737.

It's not the same fuselage shape (that is, it's not like a stretch limo where you just add something with exactly the same cross section of various lengths to give you a mild stretch or a really ridiculous stretch) for a 737, and it surely would not be for ITS. So the outer mold line tooling would NOT be the same, nor would the tankage and I think that's a lot of cost...
Title: Re: ITS Development Updates and Discussion Thread
Post by: livingjw on 06/21/2017 12:43 pm
I don't think they would change the OML shape, just the scale. Even small OML changes can have large effects on aerodynamics. Extensive aerodynamic analysis and testing is required for any OML change.

John
Title: Re: ITS Development Updates and Discussion Thread
Post by: Ludus on 06/21/2017 02:50 pm
There was no description of the tanker. Only data.

Tanker dry mass 90t

Propellant mass, Ship    1950t Cargo 300t
Propellant mass, Tanker 2500t Cargo 380t propellant

Well, if they'd shown detailed CAD of the Tanker and talked about it there wouldn't be any issue. My comments were just that between showing images of the Tanker looking just like the Heart of Gold spaceship and performance data, they strongly imply some interesting things about it's design. To me the possibility of the Tanker being the same thing as a Cargo Variant seems like a brilliant multiuse design.
Title: Re: ITS Development Updates and Discussion Thread
Post by: guckyfan on 06/21/2017 03:24 pm
To me both being the same looks like hugely inefficient. The tanker needs that extra tank volume for 550t of propellant more. Making tanks for tanker and ship the same wastes a lot of volume, maybe more important for passengers than for cargo. Also we have the tank size for the ship and it does not look like it allows for another 550t propellant.
Title: Re: ITS Development Updates and Discussion Thread
Post by: AncientU on 06/21/2017 04:09 pm
There was no description of the tanker. Only data.

Tanker dry mass 90t

Propellant mass, Ship    1950t Cargo 300t
Propellant mass, Tanker 2500t Cargo 380t propellant

Well, if they'd shown detailed CAD of the Tanker and talked about it there wouldn't be any issue. My comments were just that between showing images of the Tanker looking just like the Heart of Gold spaceship and performance data, they strongly imply some interesting things about it's design. To me the possibility of the Tanker being the same thing as a Cargo Variant seems like a brilliant multiuse design.

The video released at IAC 2016 showed the tanker and spaceship side by side during LEO refueling.  Just re-viewed that segment and the tanker has no windows (of course) and is exactly the same size/OML as the spaceship.  Could be artistic license, but that's the only side-by-side comparison we have... and it is definitive.
Title: Re: ITS Development Updates and Discussion Thread
Post by: guckyfan on 06/21/2017 04:16 pm
The video released at IAC 2016 showed the tanker and spaceship side by side during LEO refueling.  Just re-viewed that segment and the tanker has no windows (of course) and is exactly the same size/OML as the spaceship.  Could be artistic license, but that's the only side-by-side comparison we have... and it is definitive.

We have been through that already.
Title: Re: ITS Development Updates and Discussion Thread
Post by: envy887 on 06/21/2017 04:16 pm
To me both being the same looks like hugely inefficient. The tanker needs that extra tank volume for 550t of propellant more. Making tanks for tanker and ship the same wastes a lot of volume, maybe more important for passengers than for cargo. Also we have the tank size for the ship and it does not look like it allows for another 550t propellant.

Keeping the OML the same and pushing the tank bulkheads forward in the tanker is most efficient. As John noted, there are significant aerodynamics issues with changing the OML.

The tanker only needs tanks 5.3 meters longer than the crewed ship. Based on the cutaway views, it looks like they can get all the volume they need simply by stretching the tanks into the space occupied by the unpressurized cargo section on the crew ship.
Title: Re: ITS Development Updates and Discussion Thread
Post by: guckyfan on 06/21/2017 04:22 pm
Keeping the OML the same and pushing the tank bulkheads forward in the tanker is most efficient. As John noted, there are significant aerodynamics issues with changing the OML.

The tanker only needs tanks 5.3 meters longer than the crewed ship. Based on the cutaway views, it looks like they can get all the volume they need simply by stretching the tanks into the space occupied by the unpressurized cargo section on the crew ship.

That's how I see it. At least initially. Given time and a sufficient number of tankers needed they may one day develop an optimized tanker that would be shorter. Or maybe slightly more thrust out of improved Raptor and fill the existing volume with tanks.
Title: Re: ITS Development Updates and Discussion Thread
Post by: rsdavis9 on 06/21/2017 04:24 pm
To me both being the same looks like hugely inefficient. The tanker needs that extra tank volume for 550t of propellant more. Making tanks for tanker and ship the same wastes a lot of volume, maybe more important for passengers than for cargo. Also we have the tank size for the ship and it does not look like it allows for another 550t propellant.

Keeping the OML the same and pushing the tank bulkheads forward in the tanker is most efficient. As John noted, there are significant aerodynamics issues with changing the OML.

The tanker only needs tanks 5.3 meters longer than the crewed ship. Based on the cutaway views, it looks like they can get all the volume they need simply by stretching the tanks into the space occupied by the unpressurized cargo section on the crew ship.

I think you not only have to keep the OML the same but you have to keep the CG the same. Unless you have some compensation mechanism for different CG's. And of course the CG is only really important on reentry.
Title: Re: ITS Development Updates and Discussion Thread
Post by: envy887 on 06/21/2017 08:04 pm
They can mount the landing prop tanks in a different location to move the CG as needed.
Title: Re: ITS Development Updates and Discussion Thread
Post by: Ludus on 06/21/2017 08:14 pm
To me both being the same looks like hugely inefficient. The tanker needs that extra tank volume for 550t of propellant more. Making tanks for tanker and ship the same wastes a lot of volume, maybe more important for passengers than for cargo. Also we have the tank size for the ship and it does not look like it allows for another 550t propellant.

The 550t of extra propellant it can carry represents about 25% more tank volume. Since the total dry mass is only about 3.6% of the propellant mass at launch, the tanks mass is just a fraction of that 3.6% and the excess is just 25% of that, the "waste" is a fraction of 1%. For that small penalty, you get standardization and great multiuse flexibility.

Exactly, the tank size for the "ship" doesn't allow the extra 550t. That's the difference with the Tanker (implied but never depicted). The question is how much bigger do the tanks have to be to hold an extra 550t. About 25%. That means there is still a lot of empty volume forward. I don' see this as a bug, to me it's an important feature.
Title: Re: ITS Development Updates and Discussion Thread
Post by: guckyfan on 06/21/2017 08:25 pm
I am not sure we are talking about the same. I will try to make my position clear once more.

There was the suggestion that both the tanker and the ship have the same size tank volume. Which would be more than needed for the ship. I agree it would not be much in mass. But it would be valuable volume, especially for crew that would be unusable. For cargo the available volume may be enough. But there can be large bulky pieces of infrastructure that would not fit. I don't think wasting the tank volume for 550t of propellant is a good idea just for identical production.
Title: Re: ITS Development Updates and Discussion Thread
Post by: Ludus on 06/21/2017 08:26 pm
To me both being the same looks like hugely inefficient. The tanker needs that extra tank volume for 550t of propellant more. Making tanks for tanker and ship the same wastes a lot of volume, maybe more important for passengers than for cargo. Also we have the tank size for the ship and it does not look like it allows for another 550t propellant.

Keeping the OML the same and pushing the tank bulkheads forward in the tanker is most efficient. As John noted, there are significant aerodynamics issues with changing the OML.

The tanker only needs tanks 5.3 meters longer than the crewed ship. Based on the cutaway views, it looks like they can get all the volume they need simply by stretching the tanks into the space occupied by the unpressurized cargo section on the crew ship.

That's what I meant by just stretching the tanks 25%. Yes it would roughly extend them through the small cargo section in the Heart of Gold ship design. Since the Tanker doesn't have any of that internal stuff for crew it's easy to picture as just the tanks stretched through that cargo space and an empty volume forward of it. This is what suggests that it IS a Cargo Variant also. Just add doors and that's a cargo bay much larger than the SpaceShuttle Orbiter's that can be used simply by not filling the stretched tanks completely with propellant at launch. In effect some of the LOX and Methane in a "Tanker" launch is propellant and some is payload. In a Cargo launch of the same ship you dial back the propellant that's payload and add your Cargo.
Title: Re: ITS Development Updates and Discussion Thread
Post by: Ludus on 06/21/2017 08:33 pm
I am not sure we are talking about the same. I will try to make my position clear once more.

There was the suggestion that both the tanker and the ship have the same size tank volume. Which would be more than needed for the ship. I agree it would not be much in mass. But it would be valuable volume, especially for crew that would be unusable. For cargo the available volume may be enough. But there can be large bulky pieces of infrastructure that would not fit. I don't think wasting the tank volume for 550t of propellant is a good idea just for identical production.

Perhaps the problem is I'm not talking about the "ship" at all except as it's referred to in the SpaceX info as a basis for discussion. I'm suggesting that the Tanker IS already a Cargo Variant. That no special Cargo Variant may be needed. The Tanker doesn't have the same tank volume as the ship. It's whole payload is just excess Methane and LOX.
Title: Re: ITS Development Updates and Discussion Thread
Post by: Ludus on 06/21/2017 08:46 pm
I'm definitely not communicating something well. SpaceX gave numbers and depictions of a Ship (Heart of Gold Class) and a Tanker. I've always thought they implied a Third type that could be called a Cargo Variant that's just exactly like a Ship except it lacks any of the crew structures and is just a big payload bay in that space.

What I've been asking about/explaining is the possibility that the Tanker (which necessarily has Tanks about 25% larger than the Ship given the specs) IS already also the Cargo Variant. The Tanker has a lot of space for Cargo if used in that mode. When I wrote any reference to the Ship, it was just to illustrate points about the Tanker/Cargo Variant since SpaceX didn't illustrate internals of the Tanker or anything but the Ship.

I can see that since there are only 2 types shown by SpaceX, my answers could easily lead to misunderstandings.
Title: Re: ITS Development Updates and Discussion Thread
Post by: AncientU on 06/21/2017 09:53 pm
One important consideration is that the tanker never needs to do EDL at Mars or EDL with a several hundred tonne payload.  Earth EDL by a fluffy tanker, with completely different mass distribution than a loaded spaceship, could easily have a lower ballistic coefficient even if it was tanks only and 50-60% of the cross-sectional area. 

Maintaining the OML for 'operational' purposes doesn't make sense because of this... and for ease of production, even less.  The tankers will outnumber the spaceships (cargo and crew versions) by a large factor, so a unique OML is definitely a benefit, not a liability.
Title: Re: ITS Development Updates and Discussion Thread
Post by: livingjw on 06/22/2017 12:58 am
One important consideration is that the tanker never needs to do EDL at Mars or EDL with a several hundred tonne payload.  Earth EDL by a fluffy tanker, with completely different mass distribution than a loaded spaceship, could easily have a lower ballistic coefficient even if it was tanks only and 50-60% of the cross-sectional area. 

Maintaining the OML for 'operational' purposes doesn't make sense because of this... and for ease of production, even less.  The tankers will outnumber the spaceships (cargo and crew versions) by a large factor, so a unique OML is definitely a benefit, not a liability.

Respectively disagree. First, maintaining the ITS S2 OML is not for operational purposes. It is to reduce developmental costs. The CG will have to be maintained and should be achievable. Also, a lower ballistic coefficient will be easier on the TPS, and probably reduce its maintenance. The largest ITS S2 maintenance cost will most probably be its TPS.

John

John
Title: Re: ITS Development Updates and Discussion Thread
Post by: livingjw on 06/22/2017 01:05 am
I'm definitely not communicating something well. SpaceX gave numbers and depictions of a Ship (Heart of Gold Class) and a Tanker. I've always thought they implied a Third type that could be called a Cargo Variant that's just exactly like a Ship except it lacks any of the crew structures and is just a big payload bay in that space.

What I've been asking about/explaining is the possibility that the Tanker (which necessarily has Tanks about 25% larger than the Ship given the specs) IS already also the Cargo Variant. The Tanker has a lot of space for Cargo if used in that mode. When I wrote any reference to the Ship, it was just to illustrate points about the Tanker/Cargo Variant since SpaceX didn't illustrate internals of the Tanker or anything but the Ship.

I can see that since there are only 2 types shown by SpaceX, my answers could easily lead to misunderstandings.

I get it. A tanker with slightly reduced cargo capacity due to the larger than needed tanks. It also might be just the thing to provide for more delta V for some missions.

John
Title: Re: ITS Development Updates and Discussion Thread
Post by: GORDAP on 06/22/2017 03:06 pm
Apologies if this has already been mentioned, but why not simply put a set of tanks in the cargo bay of the 'cargo' version, and this is now your 'tanker'.  In essence a tanker is a cargo ship, its just that its cargo happens to be fuel.

I know this is not quite as mass efficient as making the main propellant tanks larger, but I'd be surprised if the penalty is all that great.

And it keeps all the commonality of design, manufacturing, etc.
Title: Re: ITS Development Updates and Discussion Thread
Post by: Ludus on 06/22/2017 05:44 pm
Apologies if this has already been mentioned, but why not simply put a set of tanks in the cargo bay of the 'cargo' version, and this is now your 'tanker'.  In essence a tanker is a cargo ship, its just that its cargo happens to be fuel.

I know this is not quite as mass efficient as making the main propellant tanks larger, but I'd be surprised if the penalty is all that great.

And it keeps all the commonality of design, manufacturing, etc.

First cuz SpaceX hasn't announced any Cargo Version, that's purely speculation on my part, but they have shown and given data on a Tanker version. The Tanker is an integral part of the system. The Cargo Version is something some people think is missing and useful.

A Tanker is definitely part of the plan.

So the discussion is Is the Tanker already a Cargo Version cuz it has empty cargo space anyway, not can you adapt a Cargo Version to be a Tanker, which has it backwards. You could, but given that the Tanker is already part of the plan and Cargo is not, it makes no sense (as well as being less efficient in adding new tanks).

Title: Re: ITS Development Updates and Discussion Thread
Post by: Ludus on 06/22/2017 05:51 pm
One important consideration is that the tanker never needs to do EDL at Mars or EDL with a several hundred tonne payload.  Earth EDL by a fluffy tanker, with completely different mass distribution than a loaded spaceship, could easily have a lower ballistic coefficient even if it was tanks only and 50-60% of the cross-sectional area. 

Maintaining the OML for 'operational' purposes doesn't make sense because of this... and for ease of production, even less.  The tankers will outnumber the spaceships (cargo and crew versions) by a large factor, so a unique OML is definitely a benefit, not a liability.

Help me out. OML is outer mold line? EDL? Tankers per se wouldn't outnumber Spaceships. In fact unless they follow the pattern of being identical with Cargo Ships, they'd be a minor niche variant. Their cycle time is shorter than any any other Ship by far. So there would be fewer of them than anything but Boosters, which are back on the pad in 20 minutes.
Title: Re: ITS Development Updates and Discussion Thread
Post by: guckyfan on 06/22/2017 06:49 pm
You still need more tankers than boosters. Given the number of reuses as 1000 for the booster and 100 for the orbital tanker. If these numbers turn out to be correct.
Title: Re: ITS Development Updates and Discussion Thread
Post by: fthomassy on 06/22/2017 07:10 pm
Help me out. OML is outer mold line?
Yes.
EDL?
Entry, Descent, and Landing
Title: Re: ITS Development Updates and Discussion Thread
Post by: Oersted on 06/22/2017 08:50 pm
Maintaining the OML for 'operational' purposes doesn't make sense because of this... and for ease of production, even less.  The tankers will outnumber the spaceships (cargo and crew versions) by a large factor, so a unique OML is definitely a benefit, not a liability.

It seems that you are pre-supposing that the tanker design is a modified spaceship design. Why would it be? - The two ships are being developed concurrently. Surely the design of the unique OML is suitable for both tankers and spaceships.

I believe there will be a specific set of tanks for the tankers. Of course they will mirror the spaceship tanks in most aspects, so there is maximum commonality in the design. However, to my mind it would only create more complexity (tubing, etc) to have separate additional tanks in the "cargo and crew" area. Surely bigger, but similar, tanks for the tanker version are optimal for just a small extra development cost. 
Title: Re: ITS Development Updates and Discussion Thread
Post by: 2552 on 06/23/2017 01:24 am
I think the reason ITS doesn't have full LAS functionality is because a parachute splashdown wouldn't work for such a large vehicle, and the mass penalty of taking it to Mars and back is too great. I wonder if a way to solve both problems is to have a dedicated crew launch to LEO variant of the main ITS spacecraft.

This variant would have a separable crew section, and an LAS consisting of a ring of 30 to 40 of the 10 ton pressure-fed methane/LOX RCS thrusters around the outside of the crew section, fuel tanks where the cargo section would be, and a heatshield on the bottom, under the tanks. During abort, it wouldn't use all of its fuel to get away from the rocket, but would save some for a propulsive landing in the ocean.

A Mars trip would then be: launch main ITS with cargo, fuel with 3 to 5 tanker flights, launch crew and transfer to main ITS, go to Mars. This way, the LAS isn't taken to Mars with the main ITS. The crew launch to LEO variant would also be reused up to 100 times like the tanker since it isn't going to Mars, so would only add a small cost to the mission.

Is there a reason this wouldn't work?
Title: Re: ITS Development Updates and Discussion Thread
Post by: Robotbeat on 06/23/2017 01:46 am
But you've only then solved abort for half the trip. Still haven't solved it at Mars for landing or ascent.
Title: Re: ITS Development Updates and Discussion Thread
Post by: su27k on 06/23/2017 02:13 am
But you've only then solved abort for half the trip. Still haven't solved it at Mars for landing or ascent.

Primary user of LAS is manned flights in cis-lunar space, giving Mars colonists a safer ride off Earth is a bonus.
Title: Re: ITS Development Updates and Discussion Thread
Post by: Robotbeat on 06/23/2017 03:21 am
But you've only then solved abort for half the trip. Still haven't solved it at Mars for landing or ascent.

Primary user of LAS is manned flights in cis-lunar space, giving Mars colonists a safer ride off Earth is a bonus.
You really think there will be more people shuttling around cislunar space than going to Mars? If so, could make sense to develop a safer (heavier) variant of ITS just for them.

And I do believe I remember Musk mentioning possibility of crew arriving via another vehicle in certain circumstances.
Title: Re: ITS Development Updates and Discussion Thread
Post by: Lars-J on 06/23/2017 03:47 am
But you've only then solved abort for half the trip. Still haven't solved it at Mars for landing or ascent.

Where do you expect to abort to in those situations? You provide added safety by redundancy. Because any separated module would have to be its own mini-ITS, otherwise it does the passengers no good.

But this has been discussed back and forth here ad nauseum. Some believe we will never outgrow abort capsules. Others do.
Title: Re: ITS Development Updates and Discussion Thread
Post by: Robotbeat on 06/23/2017 03:51 am
Mars surface is perfect safe for the crew to hang out in space suits in the hour or two it takes to dispatch a hopper (or propositioned down-range assets), which any respectable settlement would have available.

The idea that there's no point in aborting to the surface is an obsolete notion from back when we were assuming absolutely minimalist bases, if not just flags and footprints. But people still keep it as an assumption in the back of their minds.
Title: Re: ITS Development Updates and Discussion Thread
Post by: Lars-J on 06/23/2017 03:56 am
Mars surface is perfect safe for the crew to hang out in space suits in the hour or two it takes to dispatch a hopper (or propositioned down-range assets), which any respectable settlement would have available.

The idea that there's no point in aborting to the surface is an obsolete notion from back when we were assuming absolutely minimalist bases, if not just flags and footprints. But people still keep it as an assumption in the back of their minds.

Sigh. Your abort capsule still needs to have multiple km/s of delta-V, and landing gear plus all other systems. It will be a beast, and frankly not practical.

As we leave the cradle of Earth space we will need to accept that we cannot have abort modes for every scenario, and certainly not have abort capsules that are capable of independent flight. It just wont work. But that I'm clearly not going to convince anyone, so this is the last I will post about it for a while.
Title: Re: ITS Development Updates and Discussion Thread
Post by: Lar on 06/23/2017 03:57 am
I read it as that if there's an issue preventing reaching orbit, the vehicle just lands again, wherever it can. All of it, not an abort capsule. That won't always work, of course.

I could be misreading Robotbeat though
Title: Re: ITS Development Updates and Discussion Thread
Post by: Robotbeat on 06/23/2017 04:00 am
*Sigh* There are ways to do it. And there are ways to simplify it so it doesn't need legs, etc.

It also definitely doesn't need multiple km/s.

But you don't have to do abort. Redundancy and robustness in the primary vehicle is a legitimate alternative approach. I just kind of get mad when people make false claims about there being nowhere to abort to or needing multiple km/s, etc...
Title: Re: ITS Development Updates and Discussion Thread
Post by: kraisee on 06/23/2017 05:45 am
The question of whether to include an abort system to be able to escape the ITS upper stage is an existential one.

Just imagine - from a business perspective - what happens in the days and weeks following a cat-1 failure of an ITS upper stage carrying 100+ HNWI's...

The resulting class action lawsuit filed by the rich estates of all those dead HNWI's would certainly be able to claim "why wasn't there a separate abort system?   Dragon 2 needed one - so why did you delete that important safety feature for ITS?"

There isn't really any good argument against that point.

Unfortunately, the true reason for making that particular choice is to be able to send more stuff towards Mars on each flight at a slightly better price.   Thing is, choosing to reduce safety in order to make things cost less does NOT work as an argument in a court that is considering multiple deaths.

Perhaps even more critical for SpaceX - if they were to ever kill 100 HNWI's because they failed to provide a fairly common type of emergency safety system, just how many customers would continue to fly with them after that?

Faced with those two combined results at the same time as losing a damned expensive vehicle (look at how much the AMOS-6 blow-up cost them) and probably grounding their entire fleet for at least a year, the company's entire future would be dangerously threatened, if not outright destroyed.

It might be just me, but losing say 20% performance to Mars doesn't seem like that bad a trade if it would prevent such an existential threat from occurring.   YMMV.

Ross.
Title: Re: ITS Development Updates and Discussion Thread
Post by: Robotbeat on 06/23/2017 06:02 am
The issue isn't the payload hit but development cost, I'd wager. Dragon could've been flying people years ago without an abort system.
Title: Re: ITS Development Updates and Discussion Thread
Post by: kraisee on 06/23/2017 06:21 am
The issue isn't the payload hit but development cost, I'd wager. Dragon could've been flying people years ago without an abort system.

Not saying you're wrong, but isn't that a bit like saying a car manufacturer could delete their crumple zones, side impact protection, airbags and seat belts - i.e. the primary emergency safety equipment - just because they'd prefer to develop the car 6 months faster (with resulting cost savings) without them?

I suspect that the marketplace would have something to say about such a decision.   And I think I'll just sidestep the whole regulatory thing in this particular metaphor :)

In the end though, it all comes down to tort law.   And in there SpX has an obligation to use all reasonable methods to prevent harm.   In this hypothetical case about deaths caused by an upper stage ITS failure, do you think SpX could successfully argue that a separate abort system is not a "reasonable method"?

I don't think that's likely.   In fact, I think that deliberately choosing not to install such a system could probably be argued to be negligent.

A judgement going that way would be for an astonishingly large amount of money considering the lifetime earning potential of 100 deceased HNWI's and the pain and hurt caused to their remaining families.

Risking the company's future and the future of the whole Mars colony enterprise on that?   Call me crazy, but I just don't think that's a smart move.

Ross.
Title: Re: ITS Development Updates and Discussion Thread
Post by: Robotbeat on 06/23/2017 06:58 am
It's like saying airliners delete ejection seats and parachutes for the passengers. The cost would be far higher and fewer people would be able to fly, potentially meaning actually lower safety.
Title: Re: ITS Development Updates and Discussion Thread
Post by: kraisee on 06/23/2017 07:15 am
Yeah, but how many trillions of flight hours of understanding have we built up for the airliner industry in order to enable that degree of reliability with that class of system?

Its going to take a really long time before rocket launches can reach even just 1% of 1% (0.0001%) of that equivalent experience base, and its made even more difficult given that most launches only last about 8-10 minutes :)

I'd definitely like to see an orbital rocket system in my lifetime that achieves sufficiently high reliability that it doesn't require abort systems, or even pressure suits.

I just don't think ITS is it.   I don't think any rocket in service, or currently announced, could realistically hope to achieve that yet.   Actually fly the thing at least 1,000 times without an accident, and lets talk again.

BTW, that'll still be only ~133 launch hours on the clock :)

Ross.
Title: Re: ITS Development Updates and Discussion Thread
Post by: rsdavis9 on 06/23/2017 12:33 pm
There has been thousands of people killed in airline crashes. Why hasn't the tort system sued the airline industry for not providing escape systems? In most crashes(?) there is a time when they know they are going to crash and have time to activate something to get away.
Title: Re: ITS Development Updates and Discussion Thread
Post by: Robotbeat on 06/23/2017 12:42 pm
Yeah, but how many trillions of flight hours of understanding have we built up for the airliner industry in order to enable that degree of reliability with that class of system?

Its going to take a really long time before rocket launches can reach even just 1% of 1% (0.0001%) of that equivalent experience base, and its made even more difficult given that most launches only last about 8-10 minutes :)

I'd definitely like to see an orbital rocket system in my lifetime that achieves sufficiently high reliability that it doesn't require abort systems, or even pressure suits.

I just don't think ITS is it.   I don't think any rocket in service, or currently announced, could realistically hope to achieve that yet.   Actually fly the thing at least 1,000 times without an accident, and lets talk again.

BTW, that'll still be only ~133 launch hours on the clock :)

Ross.
I think 1000 successful flights in a row is a good benchmark.
Title: Re: ITS Development Updates and Discussion Thread
Post by: RocketmanUS on 06/23/2017 05:48 pm
Yeah, but how many trillions of flight hours of understanding have we built up for the airliner industry in order to enable that degree of reliability with that class of system?

Its going to take a really long time before rocket launches can reach even just 1% of 1% (0.0001%) of that equivalent experience base, and its made even more difficult given that most launches only last about 8-10 minutes :)

I'd definitely like to see an orbital rocket system in my lifetime that achieves sufficiently high reliability that it doesn't require abort systems, or even pressure suits.

I just don't think ITS is it.   I don't think any rocket in service, or currently announced, could realistically hope to achieve that yet.   Actually fly the thing at least 1,000 times without an accident, and lets talk again.

BTW, that'll still be only ~133 launch hours on the clock :)

Ross.
I think 1000 successful flights in a row is a good benchmark.
When it is your Kid(s) on board then you would insist on an abort system.  :)  I would.
Title: Re: ITS Development Updates and Discussion Thread
Post by: spacenut on 06/23/2017 06:10 pm
A while back, they said they needed 10 cargo flights for every 100 passengers on a passenger flight.  Why not just have 10 people on each flight.  Less humans per flight.  OR as others have said, have F9, or others bring up people. 
Title: Re: ITS Development Updates and Discussion Thread
Post by: rsdavis9 on 06/23/2017 06:16 pm
Yeah, but how many trillions of flight hours of understanding have we built up for the airliner industry in order to enable that degree of reliability with that class of system?

Its going to take a really long time before rocket launches can reach even just 1% of 1% (0.0001%) of that equivalent experience base, and its made even more difficult given that most launches only last about 8-10 minutes :)

I'd definitely like to see an orbital rocket system in my lifetime that achieves sufficiently high reliability that it doesn't require abort systems, or even pressure suits.

I just don't think ITS is it.   I don't think any rocket in service, or currently announced, could realistically hope to achieve that yet.   Actually fly the thing at least 1,000 times without an accident, and lets talk again.

BTW, that'll still be only ~133 launch hours on the clock :)

Ross.
I think 1000 successful flights in a row is a good benchmark.
When it is your Kid(s) on board then you would insist on an abort system.  :)  I would.

I don't insist on a ejection seat and parachute when my kids fly on airlines...

EDIT: I am from NH and our motto is "live free and die"  :)
Title: Re: ITS Development Updates and Discussion Thread
Post by: matthewkantar on 06/23/2017 06:35 pm
When it is your Kid(s) on board then you would insist on an abort system.  :)  I would.

Tens of thousands of people die every year in automobiles, should we insist on ejection seats? Do you let your children ride in cars? Risk should be abated when feasible, but risk should not be allowed to make progress impossible. The passengers will be familiar with the risks, and they will go none the less.

Matthew
Title: Re: ITS Development Updates and Discussion Thread
Post by: jpo234 on 06/23/2017 06:38 pm


When it is your Kid(s) on board then you would insist on an abort system.  :)  I would.

Or you can make the informed decision not to get aboard.

 Initially there won't be passengers, but spaceflight participants. I read somewhere that there is a difference. A spaceflight participant is somebody who is aware of the associated risks and choses to accept them.
Title: Re: ITS Development Updates and Discussion Thread
Post by: RocketmanUS on 06/23/2017 07:12 pm
When it is your Kid(s) on board then you would insist on an abort system.  :)  I would.

Tens of thousands of people die every year in automobiles, should we insist on ejection seats? Do you let your children ride in cars? Risk should be abated when feasible, but risk should not be allowed to make progress impossible. The passengers will be familiar with the risks, and they will go none the less.

Matthew
Adding in an escape system does not  make progress impossible. They will be launching CST-100 and Dragon 2 with escape systems.
First crew flights could use Dragon 2 to LEO for safety.  Kids do not know the risks ( colony ). Better to be safe than sorry.

There would be losses , but we do not need to add to them by not having an escape system for crewed flights. cargo and crew should be separate. Cargo flights don't need the added mass of the escape system.

If there ever will be that many people going to Mars there has already been a better way to send crew for safety.

Edit:
Passengers over 18 will decide for them selves to launch without an escape system, however they would need to sign a forum that they know the risks and would not sue if there was a failure. But public out cry would still be load!
Title: Re: ITS Development Updates and Discussion Thread
Post by: JasonAW3 on 06/23/2017 07:39 pm
For the blocks 1 and 2 designs, I can see the use of an escape system as a good option, but for later, passenger designs, I just can't see it being either reasonable nor possible, other than to launch the entire ITS off of the booster for a ground landing.

Essentially, we'll be left with the same options as Columbia had when she first flew.
Title: Re: ITS Development Updates and Discussion Thread
Post by: Darkseraph on 06/23/2017 07:54 pm
When it is your Kid(s) on board then you would insist on an abort system.  :)  I would.

Tens of thousands of people die every year in automobiles, should we insist on ejection seats? Do you let your children ride in cars? Risk should be abated when feasible, but risk should not be allowed to make progress impossible. The passengers will be familiar with the risks, and they will go none the less.

Matthew

People might insist on ejection seats if one in every hundred car journeys resulted in their car catastrophically exploding. Thankfully, automobiles are no where near that lethal, although we do insist on using such progress-killing technologies as seatbelts and airbags.


Rather than inhibiting progress, meeting high safety standards will likely increase the pool of people willing to participate in space travel while driving technological advances that higher safety requires.
Title: Re: ITS Development Updates and Discussion Thread
Post by: Ludus on 06/23/2017 08:39 pm
For ITS, human safety is an easy issue to postpone for a decade. In the early years of Mars settlement or Lunar flights or any plausible use of ITS, Dragon2 will be quite sufficient to get people into orbit safely. It's very expensive and simply pointless to actually build ITS to carry people into orbit, despite what's shown in the SpaceX pitch video. If everything goes perfectly with the SpaceX plan, there will still be plenty of time to work out the details of moving hundreds of people at a time into orbit. ITS doesn't need to be initially bothered by human safety requirements.
Title: Re: ITS Development Updates and Discussion Thread
Post by: Robotbeat on 06/23/2017 11:37 pm
I say 1000 successful flights in a row is a good benchmark because it'd be equivalent to today's most stringent achievable standards.

Launch vehicles today are only about 99% reliable at best. Launch abort systems are supposed to improve this survivability by about a factor of 10 (although only during launch...). So 1000 successful full flights (including recovery) in a row would demonstrate at least the same reliability as we'd expect for commercial crew.
Title: Re: ITS Development Updates and Discussion Thread
Post by: Negan on 06/24/2017 02:52 am
When it is your Kid(s) on board then you would insist on an abort system.  :)  I would.

There will be no kids on ITS from Earth. The affects of microgravity and radiation already make that a nonstarter.
Title: Re: ITS Development Updates and Discussion Thread
Post by: TomH on 06/24/2017 04:01 am
People might insist on ejection seats if one in every hundred car journeys resulted in their car catastrophically exploding. Thankfully, automobiles are no where near that lethal, although we do insist on using such progress-killing technologies as seatbelts and airbags.

Along with crumple zone kinetic absorption engineering, telescoping steering columns, anti-lock brakes, steering assist, steel belted radial tires, radar avoidance, and dozens of other improvements. When I was a kid, someone we knew died in an auto crash about once per month. People DID insist on improvements, and they got improvements much safer than ejection seats. Ejection seats are a lot safer than sitting in an exploding rocket, but hardly the best automobile safety device for anyone other than James Bond.

Appropriate improvements DID come to fruition for automobiles and it is qualified engineers who will continue to make spacecraft safer, not armchair internet speculators like us.
Title: Re: ITS Development Updates and Discussion Thread
Post by: Robotbeat on 06/24/2017 04:32 am
When it is your Kid(s) on board then you would insist on an abort system.  :)  I would.

There will be no kids on ITS from Earth. The affects of microgravity and radiation already make that a nonstarter.
There's radiation in airplanes.
Title: Re: ITS Development Updates and Discussion Thread
Post by: Ictogan on 06/24/2017 07:33 am
When it is your Kid(s) on board then you would insist on an abort system.  :)  I would.

There will be no kids on ITS from Earth. The affects of microgravity and radiation already make that a nonstarter.
There's radiation in airplanes.
Not as much or for as long a duration as in ITS.
Title: Re: ITS Development Updates and Discussion Thread
Post by: Welsh Dragon on 06/24/2017 08:39 am
When it is your Kid(s) on board then you would insist on an abort system.  :)  I would.

There will be no kids on ITS from Earth. The affects of microgravity and radiation already make that a nonstarter.
There's radiation in airplanes.
Are you seriously comparing upper atmosphere radiation to interplanetary radiation? There are vast quantitative and qualitative differences.
Title: Re: ITS Development Updates and Discussion Thread
Post by: MP99 on 06/24/2017 08:48 am
To me both being the same looks like hugely inefficient. The tanker needs that extra tank volume for 550t of propellant more. Making tanks for tanker and ship the same wastes a lot of volume, maybe more important for passengers than for cargo. Also we have the tank size for the ship and it does not look like it allows for another 550t propellant.

The 550t of extra propellant it can carry represents about 25% more tank volume. Since the total dry mass is only about 3.6% of the propellant mass at launch, the tanks mass is just a fraction of that 3.6% and the excess is just 25% of that, the "waste" is a fraction of 1%. For that small penalty, you get standardization and great multiuse flexibility.

Exactly, the tank size for the "ship" doesn't allow the extra 550t. That's the difference with the Tanker (implied but never depicted). The question is how much bigger do the tanks have to be to hold an extra 550t. About 25%. That means there is still a lot of empty volume forward. I don' see this as a bug, to me it's an important feature.
Larger tanks will increase the surface area, which may make reentry easier, and possibly make a small saving in the mass of heat shield per square metre?

Cheers, Martin
Title: Re: ITS Development Updates and Discussion Thread
Post by: TomH on 06/24/2017 09:17 am
When it is your Kid(s) on board then you would insist on an abort system.  :)  I would.

There will be no kids on ITS from Earth. The affects of microgravity and radiation already make that a nonstarter.
There's radiation in airplanes.

Of course there is. There is also radiation at sea level. Just go lay on the beach for a full day.
Title: Re: ITS Development Updates and Discussion Thread
Post by: guckyfan on 06/24/2017 09:44 am
To me both being the same looks like hugely inefficient. The tanker needs that extra tank volume for 550t of propellant more. Making tanks for tanker and ship the same wastes a lot of volume, maybe more important for passengers than for cargo. Also we have the tank size for the ship and it does not look like it allows for another 550t propellant.

The 550t of extra propellant it can carry represents about 25% more tank volume. Since the total dry mass is only about 3.6% of the propellant mass at launch, the tanks mass is just a fraction of that 3.6% and the excess is just 25% of that, the "waste" is a fraction of 1%. For that small penalty, you get standardization and great multiuse flexibility.

Exactly, the tank size for the "ship" doesn't allow the extra 550t. That's the difference with the Tanker (implied but never depicted). The question is how much bigger do the tanks have to be to hold an extra 550t. About 25%. That means there is still a lot of empty volume forward. I don' see this as a bug, to me it's an important feature.
Larger tanks will increase the surface area, which may make reentry easier, and possibly make a small saving in the mass of heat shield per square metre?

Cheers, Martin

You are now suggesting changing the outer mold line where the whole argument before was keeping it.
Title: Re: ITS Development Updates and Discussion Thread
Post by: su27k on 06/24/2017 10:04 am
I say 1000 successful flights in a row is a good benchmark because it'd be equivalent to today's most stringent achievable standards.

Launch vehicles today are only about 99% reliable at best. Launch abort systems are supposed to improve this survivability by about a factor of 10 (although only during launch...). So 1000 successful full flights (including recovery) in a row would demonstrate at least the same reliability as we'd expect for commercial crew.

But it's pretty risky to rely on having 1000 successful flights in a row to man-rate ITS, no? Even with constellation launches, it takes a long time (10 years?) to rack up 1000 flights, what if there's an accident in the middle? Wait another 10 years? A LAS may be expensive but its schedule has a lot more certainty.
Title: Re: ITS Development Updates and Discussion Thread
Post by: dror on 06/24/2017 10:35 am
I say 1000 successful flights in a row is a good benchmark because it'd be equivalent to today's most stringent achievable standards.

Launch vehicles today are only about 99% reliable at best. Launch abort systems are supposed to improve this survivability by about a factor of 10 (although only during launch...). So 1000 successful full flights (including recovery) in a row would demonstrate at least the same reliability as we'd expect for commercial crew.
Isn't there's a safty factor in that every single ITS vehicle will be 'flight proven' before it will take a crewed flight?
Title: Re: ITS Development Updates and Discussion Thread
Post by: zodiacchris on 06/24/2017 11:07 am
Yawn, to the last page, I can't believe we are discussing the lack of abort system again! Wake me up when something interesting is happening...
Title: Re: ITS Development Updates and Discussion Thread
Post by: Torbjorn Larsson, OM on 06/25/2017 04:14 am
Yawn, to the last page, I can't believe we are discussing the lack of abort system again! Wake me up when something interesting is happening...

It is odd, since a putative once in a lifetime choice do not compare with frequent transportation like walking. (Which in European cities are more risky per traveled distance than cars, yet no one argues for portable LAS systems.)

If you choose, like now 50 % of the global population has, to move into a city, you decrease your life expectancy with 10 % according to current statistics. That is the standard which we could, and perhaps objectively should, judge a 1 % launch and a 5 % (cancer effect) transit life reduction expectancy against.

Musk could reasonably argue that you should transit to a Mars colonial city with his system, in order to increase your life expectancy while still benefiting from the social upshot that cities give. Which of course do not argue against reasonably diminishing risks.
Title: Re: ITS Development Updates and Discussion Thread
Post by: TomH on 06/25/2017 07:15 am
If you choose, like now 50 % of the global population has, to move into a city, you decrease your life expectancy with 10 % according to current statistics.

Cite a reputable source if you can. I highly doubt it. People who live in cities have access to more and higher quality health care. They also usually have higher income and standard of living.
Title: Re: ITS Development Updates and Discussion Thread
Post by: The Amazing Catstronaut on 06/25/2017 07:43 am
Equally important is that kids shouldn't have the life decision to move to Mars made for them - not till there's an equal number of opportunities on Mars. Same way a kid on Mars shouldn't be forced to have to go to Earth - nobody is going to realise how massively different life will be in every regard.

I could go and live in Mongolia with no-to-superficial knowledge of Mongolian customs, language, or sociological traditions - eventually, I would adjust, as would most people, because Humans have hundreds of thousands of years of preconditioning which renders us able to integrate into new societies and social groups. Now imagine if I was used to living in a habitat, surrounded by fairly nearby walls, in a state of relative sterility, used to the association that if I see the sky through something other than a layer of glass, I will die, horribly, rapidly, painfully. That's going to be a huge awareness gap for a lot of people.  Imagine never seeing plants again that didn't serve a life support function, or touching an ocean. People from Earth would likely get claustrophobia and become snappish. People from Mars would have problems leaving their house. Adults can adjust to that less traumatically than children.


Children, of course, would eventually adapt - it's what children do. Yet I do get the impression that this should be a decision that shouldn't get made for children for at least another a hundred years. Going to Mars, or going from Mars to Earth, with young family members should give people pause.  I hope to go to Mars, eventually, if the barest of opportunities ever makes it my way, but I wouldn't do it with kids.
Title: Re: ITS Development Updates and Discussion Thread
Post by: guckyfan on 06/25/2017 08:32 am
Children, of course, would eventually adapt - it's what children do.

You got that right.

Yet I do get the impression that this should be a decision that shouldn't get made for children for at least another a hundred years.

Parents make choices for their children all the time. Children will often reject moving to another town or suburb. They adjust.

Assuming that families will not move to Mars before the conditions are right should be obvious. But do you get to decide when the conditions are right for others? That is what I deeply resent.
Title: Re: ITS Development Updates and Discussion Thread
Post by: biosehnsucht on 06/25/2017 08:44 am
Assuming that families will not move to Mars before the conditions are right should be obvious.

At least until 'Rocket Man' is no longer an accurate depiction of Mars, hopefully it won't always be :)

Quote from: Elton John
Mars ain't the kind of place to raise your kids
In fact it's cold as hell
And there's no one there to raise them if you did
Title: Re: ITS Development Updates and Discussion Thread
Post by: spacenut on 06/25/2017 12:22 pm
I think to begin with, people going to Mars will be like the military.  They will go for a "tour of duty" for a minimum of 2 years up to 8 or 10.  Then the will return to earth to have families or retire.  Many of the first people may be just past raising their children on earth.  Say their kids will be college age or young adults, they will be in their 40's or 50's stay on Mars and help build the colony then return to earth after 60 something to retire. 

When the colony is self sufficient, and has plenty of space, excess production of raw materials and food, then families could be raised on Mars.  They may need centrifuges built to condition kids and also keep adults conditioned to earths gravity on a daily basis as well as daily exercise for possible trip to earth at any time or sometime in their lifetimes. 

Living on Mars will be more like colonies in America, distant from Europe, but not a big culture change.  I believe they will be "westernized" like most of East Asia today.  Japan, Korea, and China have their unique culture, but their people can easily live in a westernized culture.  They will be well educated for sure. 

With a fleet of ITS, people could fairly easily travel back and forth.  By then ITS will probably not be the only way to get to and from Mars. 
Title: Re: ITS Development Updates and Discussion Thread
Post by: Kaputnik on 06/25/2017 12:49 pm
Off topic: why don't I have the option to 'like' posts in this topic?
Title: Re: ITS Development Updates and Discussion Thread
Post by: MickQ on 06/25/2017 08:35 pm
Off topic: why don't I have the option to 'like' posts in this topic?

Yeah.  Me too.
Title: Re: ITS Development Updates and Discussion Thread
Post by: RocketmanUS on 06/26/2017 05:38 am
When it is your Kid(s) on board then you would insist on an abort system.  :)  I would.

There will be no kids on ITS from Earth. The affects of microgravity and radiation already make that a nonstarter.
Why would people not return from mars back to Earth, including kids with their parents?
The BFS is a round trip spaceship.
Why would micro gravity be anymore of an issue with kids compared to adults?
SX is looking at trip time as short as 39 days. I figure that would be in the time from for colonist, not the exploration missions.

It is not that hard to add in an escape system to the BFS. The hard is more likely having it work for ascent , descent and for both Earth and Mars.

The block I BFS would most likely not carry more than 24 crew ( adult exploration crew ). So less of an issue adding in the escape system ( less crew mass and volume ).

Hopefully we will get new info by the end of September on the BFS.

Keep in mind families here on Earth travel from one country to another. Kids have been sent from county to another country by plane without their parents. If a plane looses their engines it can glide back to Earth unlike a rocket, or other issues.
Title: Re: ITS Development Updates and Discussion Thread
Post by: hkultala on 06/26/2017 11:30 am
It is not that hard to add in an escape system to the BFS. The hard is more likely having it work for ascent , descent and for both Earth and Mars.

It is not hard to claim something without thinking at all how it would be made.

Dragon capsule is something like 6 tonnes.

ITS at full fuel load is 2100 tonnes.

When the 1st stage is about to explode and the escape system needs to quickly lift ITS away from the first stage,
the escape system would have to be 350 times more powerful than the escape system of Dragon v2. It would simply be too big and too heavy so that it would very seriously hinder the performance of the craft.

Then, the issue of problem with the second stage. The crew is in the same stage as the engines and fuel, it is not splittable. Cannot escape second stage explosion/problem when taking of from mars.
Title: Re: ITS Development Updates and Discussion Thread
Post by: envy887 on 06/26/2017 11:46 am
It is not that hard to add in an escape system to the BFS. The hard is more likely having it work for ascent , descent and for both Earth and Mars.

It is not hard to claim something without thinking at all how it would be made.

Dragon capsule is something like 6 tonnes.

ITS at full fuel load is 2100 tonnes.

When the 1st stage is about to explode and the escape system needs to quickly lift ITS away from the first stage,
the escape system would have to be 350 times more powerful than the escape system of Dragon v2. It would simply be too big and too heavy so that it would very seriously hinder the performance of the craft.

Then, the issue of problem with the second stage. The crew is in the same stage as the engines and fuel, it is not splittable. Cannot escape second stage explosion/problem when taking of from mars.

All of which can be solved by separating the crew section from the tanks/cargo section. Mass goes down to about 20x Dragon.
Title: Re: ITS Development Updates and Discussion Thread
Post by: rsdavis9 on 06/26/2017 11:52 am
For an escape system. How about individual pods mounted along the outside circumference. Very small with tps and chute. Would they also need rcs and/or landing rockets? Sort of like star trek.

Title: Re: ITS Development Updates and Discussion Thread
Post by: docmordrid on 06/26/2017 11:54 am
It is not that hard to add in an escape system to the BFS. The hard is more likely having it work for ascent , descent and for both Earth and Mars.

It is not hard to claim something without thinking at all how it would be made.
>
When the 1st stage is about to explode and the escape system needs to quickly lift ITS away from the first stage,
the escape system would have to be 350 times more powerful than the escape system of Dragon v2. It would simply be too big and too heavy so that it would very seriously hinder the performance of the craft.
>

With all the cautions about promotional graphics in mind, there is a very obvious seam in the Spaceships exterior which seems a natural location for it to break away from the propulsion and cargo module. No abort thrusters are shown, but then adding the SuperDraco thruster pods to the exterior of Dragon didn't seem to be a showstopper either.

Crawling even further out on the limb, an ITS ship based satellite launcher could replace the crew module with non-jettisoned clamshell fairing halves partially covered with a re-entry TPS. 
Title: Re: ITS Development Updates and Discussion Thread
Post by: hkultala on 06/26/2017 12:03 pm
It is not that hard to add in an escape system to the BFS. The hard is more likely having it work for ascent , descent and for both Earth and Mars.

It is not hard to claim something without thinking at all how it would be made.
>
When the 1st stage is about to explode and the escape system needs to quickly lift ITS away from the first stage,
the escape system would have to be 350 times more powerful than the escape system of Dragon v2. It would simply be too big and too heavy so that it would very seriously hinder the performance of the craft.
>

With all the cautions about promotional graphics in mind, there is a very obvious seam in the Spaceships exterior which seems a natural location for it to break away from the propulsion and cargo module. No abort thrusters are shown, but then adding the SuperDraco thruster pods to the exterior of Dragon didn't seem to be a showstopper either.

Superdraco pods are not lego parts. They would need to have huge number of those superdracoes, and in addition to the weight, they would also have quite big aerodynamic effect. And making the ship splittable would make quite many things more complex. 

Abort from the second stage burn would mean that heat shield would be needed at the bottom of the crew compartment. But still the cargo area would have to be accessed through this heat shield.

This solution is possible, but it's far from easy and quite expensive.
Title: Re: ITS Development Updates and Discussion Thread
Post by: docmordrid on 06/26/2017 12:22 pm
It is not that hard to add in an escape system to the BFS. The hard is more likely having it work for ascent , descent and for both Earth and Mars.

It is not hard to claim something without thinking at all how it would be made.
>
When the 1st stage is about to explode and the escape system needs to quickly lift ITS away from the first stage,
the escape system would have to be 350 times more powerful than the escape system of Dragon v2. It would simply be too big and too heavy so that it would very seriously hinder the performance of the craft.
>

With all the cautions about promotional graphics in mind, there is a very obvious seam in the Spaceships exterior which seems a natural location for it to break away from the propulsion and cargo module. No abort thrusters are shown, but then adding the SuperDraco thruster pods to the exterior of Dragon didn't seem to be a showstopper either.

Superdraco pods are not lego parts. They would need to have huge number of those superdracoes,

I only mentioned them in the context of adding pods to Dragon. Obviously, adding any such thrusters would be a new part, perhaps leveraging or based on the 10 tonne thrusters to be used to center the Booster over the landing cradle.

Quote
...and in addition to the weight, they would also have quite big aerodynamic effect. And making the ship splittable would make quite many things more complex. 

In the spirit of KISS, the seam may already be there and explosive bolts are cheap and proven.

WRT splitting modules, adding pods and fairings, a chute etc. this all depends on if you're going to use the aircraft model (no escape) or the existing crewed spacecraft model, in which case you do the necessary R&D and get on with laying out carbon/cutting metal. At some point regulators may not give you the option.
Title: Re: ITS Development Updates and Discussion Thread
Post by: envy887 on 06/26/2017 12:30 pm
It is not that hard to add in an escape system to the BFS. The hard is more likely having it work for ascent , descent and for both Earth and Mars.

It is not hard to claim something without thinking at all how it would be made.
>
When the 1st stage is about to explode and the escape system needs to quickly lift ITS away from the first stage,
the escape system would have to be 350 times more powerful than the escape system of Dragon v2. It would simply be too big and too heavy so that it would very seriously hinder the performance of the craft.
>

With all the cautions about promotional graphics in mind, there is a very obvious seam in the Spaceships exterior which seems a natural location for it to break away from the propulsion and cargo module. No abort thrusters are shown, but then adding the SuperDraco thruster pods to the exterior of Dragon didn't seem to be a showstopper either.

Superdraco pods are not lego parts. They would need to have huge number of those superdracoes, and in addition to the weight, they would also have quite big aerodynamic effect. And making the ship splittable would make quite many things more complex. 

Abort from the second stage burn would mean that heat shield would be needed at the bottom of the crew compartment. But still the cargo area would have to be accessed through this heat shield.

This solution is possible, but it's far from easy and quite expensive.

It's not easy, but it FAR easier than aborting a 2000 prop tank and 200 tonnes of unpressurized cargo away...

I would definitely put the abort thrusters inside, at the top of the cargo section. And I would probably use the 10-tonne gaseous methalox thrusters SpaceX is supposed to be developing, rather than SDs. About 40 of them would probably be sufficient.

I'm not sure that a "real" heatshield would be needed on the bulkhead between the crew and cargo compartments. The CG of the separable compartment would be managed so that the exterior heatshield takes any entry heating, so the bulkhead only sees backshell heating - a fairly thin layer of SPAM would be sufficient. Dragon has a hatch though the backshell, so this is clearly not that difficult.

There's been a lot of research into splitting structural walls quickly and cleanly at very specific locations. Either a frangible joint or redundant shaped charge (like FTS) could work. Interior plumbing and wiring would need a disconnect  like Dragon does with it's trunk.

Landing would likely need to be a propulsively-braked splashdown. Could add a few drogues in the nose to ensure proper orientation for the landing burn, and to help reduce terminal velocity a bit.
Title: Re: ITS Development Updates and Discussion Thread
Post by: Chris Bergin on 06/26/2017 01:09 pm
Off topic: why don't I have the option to 'like' posts in this topic?

Yeah.  Me too.

Strange. This one section had lost its "likes" permissions. Got it back, so all is good again. Now.....Mars.
Title: Re: ITS Development Updates and Discussion Thread
Post by: Arb on 06/26/2017 01:53 pm
From a safety perspective the ITS is neither a ship nor an airliner though it has "similarities" to both.

According to Wikipedia (https://en.wikipedia.org/wiki/Aviation_safety#Statistics), the CAA's global fatal accident review for 2013 calculated 5.39 fatalities per one million air travel departures.

According to the BBC (http://www.bbc.com/travel/story/20120127-travelwise-what-is-the-safest-mode-of-travel), the Cruise Lines International Association (CLIA) said that from 2005 to 2011 only 16 people died in cruise accidents, out of 100 million passengers, putting the odds of death over that period at one in 6.25 million.

It will be a long time before BFR/BFS can match these figures. Yet the people using it will mainly be celebrities and/or the wealthy (think Concord). Any loss of life is most certainly going to be noticed; big time.

So sooner or later all passenger carrying rockets and space craft (ITS included) will have launch escape systems and lifeboats; by law. The only question is how many lives have first to be lost.

YMMV
Title: Re: ITS Development Updates and Discussion Thread
Post by: Negan on 06/26/2017 04:52 pm
Why would micro gravity be anymore of an issue with kids compared to adults?

Why would the harmful affects of microgravity be any less for a child than an adult? Why would the countermeasures for an adult be just as effective for a child? Why would a society that is more than willing to make laws that error on the side of caution to protect a child's welfare suddenly change it's mind when it comes to shuttling kids to Mars? Child welfare advocates far outnumber Mars advocates. It's not like a law banning children going to Mars would be hard to enforce, and that's even if SpaceX would allow it which I doubt.

This is all OT for an initial version of ITS anyway which I thought this thread was about. There will be no consideration for children given to its design so pointing to children as a reason for a LAS is not logical.

Edit: and I specifically said from Earth
Title: Re: ITS Development Updates and Discussion Thread
Post by: Jim on 06/26/2017 05:11 pm

Why would micro gravity be anymore of an issue with kids compared to adults?


It is obvious.  There would be growth development issues.
Title: Re: ITS Development Updates and Discussion Thread
Post by: Nomadd on 06/26/2017 05:53 pm

Why would micro gravity be anymore of an issue with kids compared to adults?


It is obvious.  There would be growth development issues.
It seems unlikely that anyone who's born in space at partial G or grows up there will ever be able to return to Earth. I've always thought that's the time we really become a multi world species.
Title: Re: ITS Development Updates and Discussion Thread
Post by: TheKutKu on 06/26/2017 06:08 pm
Why not just make some kind of scaled up dragon-like capsule (with life support for a few days and more cramped than a dragon, you may reach something like 70 or so tons to send 100 people into LEO) and put it on top of ONE tanker, it is known that the additional fuel tank for the tanker doesn't take all of the top of the ITS and that there's a lot of empty space there, i wonder if they could just send the crew with the last tanker mission, the fuel payload penalty wouldn't be huge (only 1880 tons instead of 1950 tons) and it seems worth it to me.

The capsule would stay on top of the ITS in a normal flight and reenter on top of it like in any other ITS flight, and when there's an anomaly it would escape and the ITS Tanker would be destroyed.
Title: Re: ITS Development Updates and Discussion Thread
Post by: Lars-J on 06/26/2017 07:13 pm
Why not just make some kind of scaled up dragon-like capsule (with life support for a few days and more cramped than a dragon, you may reach something like 70 or so tons to send 100 people into LEO) and put it on top of ONE tanker, it is known that the additional fuel tank for the tanker doesn't take all of the top of the ITS and that there's a lot of empty space there, i wonder if they could just send the crew with the last tanker mission, the fuel payload penalty wouldn't be huge (only 1880 tons instead of 1950 tons) and it seems worth it to me.

The capsule would stay on top of the ITS in a normal flight and reenter on top of it like in any other ITS flight, and when there's an anomaly it would escape and the ITS Tanker would be destroyed.

Abort capsules scale up very poorly. It is physics. And it isn't just the propellant needed, once you reach a certain point parachutes become impractical and beyond that even impossible. So in addition you need landing propellant as well. And the whole thing enters an engineering death spiral...
Title: Re: ITS Development Updates and Discussion Thread
Post by: RocketmanUS on 06/26/2017 07:16 pm
It is not that hard to add in an escape system to the BFS. The hard is more likely having it work for ascent , descent and for both Earth and Mars.

It is not hard to claim something without thinking at all how it would be made.

Dragon capsule is something like 6 tonnes.

ITS at full fuel load is 2100 tonnes.

When the 1st stage is about to explode and the escape system needs to quickly lift ITS away from the first stage,
the escape system would have to be 350 times more powerful than the escape system of Dragon v2. It would simply be too big and too heavy so that it would very seriously hinder the performance of the craft.

Then, the issue of problem with the second stage. The crew is in the same stage as the engines and fuel, it is not splittable. Cannot escape second stage explosion/problem when taking of from mars.
In the early flights ( exploration ) there would more likely only be 12 to 24 crew per BFS. I was looking at having crew seated on the top part of the BFS were that part could separate from the rest of the BFS. Much less mass than the whole BFS ( even for 100 crew ) and might save crew if the BFS had an issue.

Why would micro gravity be anymore of an issue with kids compared to adults?

Why would the harmful affects of microgravity be any less for a child than an adult? Why would the countermeasures for an adult be just as effective for a child? Why would a society that is more than willing to make laws that error on the side of caution to protect a child's welfare suddenly change it's mind when it comes to shuttling kids to Mars? Child welfare advocates far outnumber Mars advocates. It's not like a law banning children going to Mars would be hard to enforce, and that's even if SpaceX would allow it which I doubt.

This is all OT for an initial version of ITS anyway which I thought this thread was about. There will be no consideration for children given to its design so pointing to children as a reason for a LAS is not logical.

Edit: and I specifically said from Earth


Why would micro gravity be anymore of an issue with kids compared to adults?


It is obvious.  There would be growth development issues.
If we could not go between Earth and Mars, what is the point in having a colony on Mars if we could not return to Earth?
Why not then just have space stations with 1 g ?

Not obvious ( development issues ) , but good point that would need to be looked into.

And SX might have added an escape system to their BFS concept since last September.
Title: Re: ITS Development Updates and Discussion Thread
Post by: rsdavis9 on 06/26/2017 07:42 pm
Why not just make some kind of scaled up dragon-like capsule (with life support for a few days and more cramped than a dragon, you may reach something like 70 or so tons to send 100 people into LEO) and put it on top of ONE tanker, it is known that the additional fuel tank for the tanker doesn't take all of the top of the ITS and that there's a lot of empty space there, i wonder if they could just send the crew with the last tanker mission, the fuel payload penalty wouldn't be huge (only 1880 tons instead of 1950 tons) and it seems worth it to me.

The capsule would stay on top of the ITS in a normal flight and reenter on top of it like in any other ITS flight, and when there's an anomaly it would escape and the ITS Tanker would be destroyed.

Abort capsules scale up very poorly. It is physics. And it isn't just the propellant needed, once you reach a certain point parachutes become impractical and beyond that even impossible. So in addition you need landing propellant as well. And the whole thing enters an engineering death spiral...

So this is a really interesting point. What is the optimal size for weight and volume of a small escape vessel.
What do you need on an escape vessel?
Parachute.
Reentry shield.
Landing rockets(same as escape rockets?)
Either a pressure vessel or a space suit.

For that matter are all 100 people going to be wearing space suits at launch?
Title: Re: ITS Development Updates and Discussion Thread
Post by: Torbjorn Larsson, OM on 06/26/2017 09:27 pm
From a safety perspective the ITS is neither a ship nor an airliner though it has "similarities" to both.

According to Wikipedia (https://en.wikipedia.org/wiki/Aviation_safety#Statistics), the CAA's global fatal accident review for 2013 calculated 5.39 fatalities per one million air travel departures.

According to the BBC (http://www.bbc.com/travel/story/20120127-travelwise-what-is-the-safest-mode-of-travel), the Cruise Lines International Association (CLIA) said that from 2005 to 2011 only 16 people died in cruise accidents, out of 100 million passengers, putting the odds of death over that period at one in 6.25 million.

It will be a long time before BFR/BFS can match these figures. Yet the people using it will mainly be celebrities and/or the wealthy (think Concord). Any loss of life is most certainly going to be noticed; big time.

So sooner or later all passenger carrying rockets and space craft (ITS included) will have launch escape systems and lifeboats; by law. The only question is how many lives have first to be lost.

YMMV

By that analysis one can ask why planes or cars, or again bikes and people city walking, do not have mandated escape systems and lifeboats. [And again, the man years lost is dominated by cancers - who cannot be mandated away - and the man years gained factors - due to no Earth city life - are dominating even that.]


Why would micro gravity be anymore of an issue with kids compared to adults?


It is obvious.  There would be growth development issues.

It seems unlikely that anyone who's born in space at partial G or grows up there will ever be able to return to Earth. I've always thought that's the time we really become a multi world species.

I do not see why it would be unlikely that martians could visit or migrate to Earth. Presumably they will use the same atmosphere or at least oxygen partial pressure, making development not an issue as such. C.f. how tetrapods settled land despite the lineage initially evolved in partial acceleration of water support. Fetuses would develop the same, and if they exert the same extremal body forces after birth their development should be much the same.

If they would tend to slack off, sure. But that does not seem likely in playing kids, unruly adolescents or working adults in early colonization build up. Possibly there would be issues, but drastic differences seem unlikely.

Space colonies, on the other hand ... Ouch. "These results suggest for the first time that fertilization can occur normally under µG environment in a mammal, but normal preimplantation embryo development might require 1G." [ http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0006753 ]

EDIT: Language.
Title: Re: ITS Development Updates and Discussion Thread
Post by: TomH on 06/27/2017 04:19 am
...the man years gained factors - due to no Earth city life...

There you go again. We get it....you don't like cities. But these continued assertions that cities are detrimental to humanity and that they shorten the human lifespan are not only unscientific, they are downright wrong. Go disseminate this unsubstantiated opinion somewhere else; it is unrelated to the purpose of this site. If you want to make any serious assertions, I say again, cite a reputable source.
Title: Re: ITS Development Updates and Discussion Thread
Post by: JamesH65 on 06/27/2017 10:11 am
...the man years gained factors - due to no Earth city life...

There you go again. We get it....you don't like cities. But these continued assertions that cities are detrimental to humanity and that they shorten the human lifespan are not only unscientific, they are downright wrong. Go disseminate this unsubstantiated opinion somewhere else; it is unrelated to the purpose of this site. If you want to make any serious assertions, I say again, cite a reputable source.

Seems to be the other way round

http://www.medicaldaily.com/life-expectancy-gap-between-city-and-country-folk-widens-how-access-health-care-plays-part-267929

https://www.wsj.com/articles/SB10001424052702304793504576434442652581806

Or is it...(sorry about the Daily Mail link, scum the lot of them)

http://www.dailymail.co.uk/health/article-1281623/Village-dwellers-likely-live-longer-city-slickers-report-finds.html

Found nothing official in  a quick search though.
Title: Re: ITS Development Updates and Discussion Thread
Post by: Oersted on 06/27/2017 04:38 pm
What a tedious discussion. SpaceX has made no suggestion of an escape system. If we are supposed to discuss ITS development in this thread then we should build on the SpaceX plans already published.
Title: Re: ITS Development Updates and Discussion Thread
Post by: original_mds on 07/11/2017 12:39 pm
Apologies if this has already been mentioned, but why not simply put a set of tanks in the cargo bay of the 'cargo' version, and this is now your 'tanker'.  In essence a tanker is a cargo ship, its just that its cargo happens to be fuel.

I know this is not quite as mass efficient as making the main propellant tanks larger, but I'd be surprised if the penalty is all that great.

And it keeps all the commonality of design, manufacturing, etc.

I realize this thread has drifted elsewhere, but this comment got me thinking:  why not add "pusher" interfaces on the front and rear (placed strategically between the rocket bells).

This would allow for a modular approach to constructing transit "trains" capable of moving integrated structures or other outsize payloads  (e.g. habs integrated in LEO) to BEO by crewed or uncrewed systems.  Establishing a homogeneous standard interface would also allow disabled vehicles to be captured and manouvered.  Future capabilities could also take advantage of such an interface (e.g. add-on nuclear or solar electric propulsion systems could hook up to the rear of a train/stack to reduce transit time, or a ship could push a "drop" tank for instantiating an instant fuel depot at the destination.

Obviously, there would be bennefits to also having a preasurized connection for personnel transfer and other capabilities like power orfluid transfer, but some of these may be infeasible due to the ITS boilerplate design.

Am I on to something, or has this been hashed out elsewhere?  (In the context of the ITS)
Title: Re: ITS Development Updates and Discussion Thread
Post by: Ludus on 07/11/2017 03:00 pm
What a tedious discussion. SpaceX has made no suggestion of an escape system. If we are supposed to discuss ITS development in this thread then we should build on the SpaceX plans already published.

The IAC video showed passengers boarding the ITS ship on the launch pad. There are three alternatives. Either SpaceX puts large numbers of people at risk during launch, or they have some launch abort system, or the depiction of boarding passengers is just artistic license and they really don't intend to launch ITS with people aboard in any real current plans. I favor the third. Launching people on ITS doesn't make much sense for Mars or other uses. Dragon 2 is sufficient for any early flights. If they need to actually get 100 passengers onboard eventually they can develop a Dragon 3 with 50 seats that could also service the larger space stations of that era. FHR could probably lift it. There isn't much reason to have people aboard when you launch or waiting for propellant Tankers and/or cargo transfer.


Title: Re: ITS Development Updates and Discussion Thread
Post by: JasonAW3 on 07/11/2017 03:48 pm

I realize this thread has drifted elsewhere, but this comment got me thinking:  why not add "pusher" interfaces on the front and rear (placed strategically between the rocket bells).

This would allow for a modular approach to constructing transit "trains" capable of moving integrated structures or other outsize payloads  (e.g. habs integrated in LEO) to BEO by crewed or uncrewed systems.  Establishing a homogeneous standard interface would also allow disabled vehicles to be captured and manouvered.  Future capabilities could also take advantage of such an interface (e.g. add-on nuclear or solar electric propulsion systems could hook up to the rear of a train/stack to reduce transit time, or a ship could push a "drop" tank for instantiating an instant fuel depot at the destination.

Obviously, there would be bennefits to also having a preasurized connection for personnel transfer and other capabilities like power orfluid transfer, but some of these may be infeasible due to the ITS boilerplate design.

Am I on to something, or has this been hashed out elsewhere?  (In the context of the ITS)

While on the surface, this would seem a fair idea, the mass and redesign of the ITS lander itself, would make this a non-starter from the get go.  Structural loads would have to be accommodated somehow, and this would add mass.

      I, personally, am of the modular space infrastructure camp, but that would require a way of bringing craft back into orbit with only minimal aerobraking at best.  Other alternatives would require months of deceleration  orbits so a rendezvous can be made, or a LOT more fuel to slow down sufficiently to enter orbit.
Title: Re: ITS Development Updates and Discussion Thread
Post by: original_mds on 07/11/2017 05:26 pm

I realize this thread has drifted elsewhere, but this comment got me thinking:  why not add "pusher" interfaces on the front and rear (placed strategically between the rocket bells).

This would allow for a modular approach to constructing transit "trains" capable of moving integrated structures or other outsize payloads  (e.g. habs integrated in LEO) to BEO by crewed or uncrewed systems.  Establishing a homogeneous standard interface would also allow disabled vehicles to be captured and manouvered.  Future capabilities could also take advantage of such an interface (e.g. add-on nuclear or solar electric propulsion systems could hook up to the rear of a train/stack to reduce transit time, or a ship could push a "drop" tank for instantiating an instant fuel depot at the destination.

Obviously, there would be bennefits to also having a preasurized connection for personnel transfer and other capabilities like power orfluid transfer, but some of these may be infeasible due to the ITS boilerplate design.

Am I on to something, or has this been hashed out elsewhere?  (In the context of the ITS)

While on the surface, this would seem a fair idea, the mass and redesign of the ITS lander itself, would make this a non-starter from the get go.  Structural loads would have to be accommodated somehow, and this would add mass.

      I, personally, am of the modular space infrastructure camp, but that would require a way of bringing craft back into orbit with only minimal aerobraking at best.  Other alternatives would require months of deceleration  orbits so a rendezvous can be made, or a LOT more fuel to slow down sufficiently to enter orbit.

I'm thinking loading forces would be significantly reduced relative to launch loads to allow for structures designed for zero-g applications.  Moving such payloads may not be suitable for missions involving rentry of the whole stack, so a retroburn would also be needed, thus requiring more fuel.  If there are interior modifications anyway for the tankers to enlarge the tanks, they may be able to deal with front loading at the same time in the tanker variant (e.g. via superpreassurization of part of the structure).

After all, we tend to see a lot of examples of towed payloads in every other transportation mode.  This would be far more extendable than a one (or two or three) size fits all approach accross the expected lifetime of a given vehicle.
Title: Re: ITS Development Updates and Discussion Thread
Post by: rsdavis9 on 07/11/2017 07:04 pm
I would think when we get to the point of connecting multiple rockets together for transport. It will be much more efficient to have dedicated space craft. Meaning craft optimized for in space work. No aero loads, no high G. Therefore the structure can be much lighter. Rocket engines don't need to be so powerful because there is no gravity loss. Lighter engines, lighter structure and you get much better mass fraction. 
Title: Re: ITS Development Updates and Discussion Thread
Post by: oldAtlas_Eguy on 07/13/2017 02:03 pm
I would think when we get to the point of connecting multiple rockets together for transport. It will be much more efficient to have dedicated space craft. Meaning craft optimized for in space work. No aero loads, no high G. Therefore the structure can be much lighter. Rocket engines don't need to be so powerful because there is no gravity loss. Lighter engines, lighter structure and you get much better mass fraction.
Yes, even Musk has mentioned this. But this is something he alludes to happening decades after ITS is operational. In this scenario where very large interplanetary only spacecraft that transport people or cargo or both on the order of several thousand people or several thousand mt of cargo (probably more like in the 10s of thousands) per trip the ITS remains but only as a local vehicle at Earth and Mars as the surface to orbit shuttle. It would no longer be used as the trip vehicle between Earth and Mars. But the ITS could still be used for other planets and moon exploration in which a combination of the in-space only carrier is teamed up with several ITS for these long journey missions.

Just saw this thread for this discussion of what comes after ITS. http://forum.nasaspaceflight.com/index.php?topic=43302.0 (http://forum.nasaspaceflight.com/index.php?topic=43302.0)
Title: Re: ITS Development Updates and Discussion Thread
Post by: su27k on 07/14/2017 05:31 pm
https://arstechnica.com/science/2017/07/spacex-urges-lawmakers-to-commercialize-deep-space-exploration/

Quote
On Thursday during a hearing before the US Senate's Subcommittee on Space, Science, and Competitiveness, SpaceX formally called upon the US government to support public-private partnerships in deep space. Tim Hughes, SpaceX's senior vice president for global business and government affairs, testified. "The principles applied in past programs for low Earth orbit capability can and should be applied to deep space exploration," Hughes said. He referred to NASA's Commercial Orbital Transportation Services, or COTS program.

NASA, Hughes said, should now consider funding a COTS-like program to run "in parallel" to NASA's Space Launch System and Orion spacecraft for deep space exploration. "There's a program of record right now that is NASA's central focus for deep space exploration," Hughes said in response to a Senator's question. "But I think it can be readily supplemented with public-private partnerships to allow us to sustain a permanent presence in space."

As examples, Hughes said NASA could set "high level requirements" for companies, such as demonstrating the vertical takeoff and landing of rockets from the lunar surface, delivering large amounts of cargo to the surface of Mars, or building a more reliable communications network between Earth and Mars. All of these projects, he said, would enable the United States to establish a permanent presence in space, rather than fly one-off missions.

This seems significant, even though it may fall on deaf ears, this looks to me like a major declaration of intent from SpaceX that basically outlines the plan of cooperation with NASA on the path to Mars. I listened to the hearing too, Hughes made it very clear that:
1. It would be a supplement, not challenging the program of record
2. Use COTS model and public-private partnership
3. While he mentioned lunar activity and Mars telecommunication as example, it sounds like heavy cargo transport to Mars surface is the preferred program.
Title: Re: ITS Development Updates and Discussion Thread
Post by: Khadgars on 07/14/2017 05:36 pm
https://arstechnica.com/science/2017/07/spacex-urges-lawmakers-to-commercialize-deep-space-exploration/

Quote
On Thursday during a hearing before the US Senate's Subcommittee on Space, Science, and Competitiveness, SpaceX formally called upon the US government to support public-private partnerships in deep space. Tim Hughes, SpaceX's senior vice president for global business and government affairs, testified. "The principles applied in past programs for low Earth orbit capability can and should be applied to deep space exploration," Hughes said. He referred to NASA's Commercial Orbital Transportation Services, or COTS program.

NASA, Hughes said, should now consider funding a COTS-like program to run "in parallel" to NASA's Space Launch System and Orion spacecraft for deep space exploration. "There's a program of record right now that is NASA's central focus for deep space exploration," Hughes said in response to a Senator's question. "But I think it can be readily supplemented with public-private partnerships to allow us to sustain a permanent presence in space."

As examples, Hughes said NASA could set "high level requirements" for companies, such as demonstrating the vertical takeoff and landing of rockets from the lunar surface, delivering large amounts of cargo to the surface of Mars, or building a more reliable communications network between Earth and Mars. All of these projects, he said, would enable the United States to establish a permanent presence in space, rather than fly one-off missions.

This seems significant, even though it may fall on deaf ears, this looks to me like a major declaration of intent from SpaceX that basically outlines the plan of cooperation with NASA on the path to Mars. I listened to the hearing too, Hughes made it very clear that:
1. It would be a supplement, not challenging the program of record
2. Use COTS model and public-private partnership
3. While he mentioned lunar activity and Mars telecommunication as example, it sounds like heavy cargo transport to Mars surface is the preferred program.

I have never expected ITS to come to fruition for reasons I won't go into here, but I do believe SpaceX has an important role to play getting us to Mars.  A "Deep Space" COTS program is a perfect way to accomplish this.   
Title: Re: ITS Development Updates and Discussion Thread
Post by: Robotbeat on 07/14/2017 09:52 pm
Nobody but SpaceX is doing serious work on a Mars lander. That's the obvious role.

And that is the hardest part of ITS.
Title: Re: ITS Development Updates and Discussion Thread
Post by: RonM on 07/14/2017 10:01 pm
Actually, the hardest part of ITS might be funding. Very ambitious program, especially for a private company. Some COTS money would help.
Title: Re: ITS Development Updates and Discussion Thread
Post by: Robotbeat on 07/14/2017 10:04 pm
Actually, the hardest part of ITS might be funding. Very ambitious program, especially for a private company. Some COTS money would help.
Obviously I was referring to technical difficulties. #actually
Title: Re: ITS Development Updates and Discussion Thread
Post by: Eerie on 07/15/2017 03:25 pm
Nobody but SpaceX is doing serious work on a Mars lander. That's the obvious role.

And that is the hardest part of ITS.

Erm...

NASA did a lot of serious work on Mars landers. And actually landed seven.
Title: Re: ITS Development Updates and Discussion Thread
Post by: M.E.T. on 07/15/2017 03:29 pm
Nobody but SpaceX is doing serious work on a Mars lander. That's the obvious role.

And that is the hardest part of ITS.

Erm...

NASA did a lot of serious work on Mars landers. And actually landed seven.

The issue is heavy landers. Multiple tons of cargo. No one seems to be any work on that other than SpaceX.
Title: Re: ITS Development Updates and Discussion Thread
Post by: Robotbeat on 07/15/2017 04:27 pm
Nobody but SpaceX is doing serious work on a Mars lander. That's the obvious role.

And that is the hardest part of ITS.

Erm...

NASA did a lot of serious work on Mars landers. And actually landed seven.
...none of which scales beyond a ton or so. Of course you know that. You also knew what I was referring to.

NASA HSF spends all their money on things other than the one thing needed for Moon or Mars: a lander.
Title: Re: ITS Development Updates and Discussion Thread
Post by: Negan on 07/15/2017 05:07 pm
Nobody but SpaceX is doing serious work on a Mars lander. That's the obvious role.

And that is the hardest part of ITS.

Erm...

NASA did a lot of serious work on Mars landers. And actually landed seven.
...none of which scales beyond a ton or so. Of course you know that. You also knew what I was referring to.

NASA HSF spends all their money on things other than the one thing needed for Moon or Mars: a lander.

I thought the reason why NASA was working on hypersonic inflatable aerodynamic decelerator technology as well as supporting the Red Dragon mission was to support heavier payloads.
Title: Re: ITS Development Updates and Discussion Thread
Post by: original_mds on 07/17/2017 06:19 pm
I thought the reason why NASA was working on hypersonic inflatable aerodynamic decelerator technology as well as supporting the Red Dragon mission was to support heavier payloads.
Maybe.  But it also has implications for landing non-aerodynamic shapes and potential adaptation to an inflatable escape pod/(re)entry vehicle, similar to the MOOS concept.
Title: Re: ITS Development Updates and Discussion Thread
Post by: Ionmars on 07/18/2017 03:21 pm
...
...
I thought the reason why NASA was working on hypersonic inflatable aerodynamic decelerator technology as well as supporting the Red Dragon mission was to support heavier payloads.
Heavier, yes. But when the lander is greater than 40 tonnes, HIAD will not do the job.  Other systems will be required, such as supersonic retropulsion and biconic shells.
https://solarsystem.nasa.gov/docs/IPPW-8_Short_Course_SRP_Edquist_Final.pdf
Title: Re: ITS Development Updates and Discussion Thread
Post by: JasonAW3 on 07/18/2017 03:41 pm
...
...
I thought the reason why NASA was working on hypersonic inflatable aerodynamic decelerator technology as well as supporting the Red Dragon mission was to support heavier payloads.
Heavier, yes. But when the lander is greater than 40 tonnes, HIAD will not do the job.  Other systems will be required, such as supersonic retropulsion and biconic shells.
https://solarsystem.nasa.gov/docs/IPPW-8_Short_Course_SRP_Edquist_Final.pdf

I have to wonder if HIAD could help and by how much with deceleration.  If we're talking about 10% or less, it likely wouldn't really be worth the extra mass it would add.
Title: Re: ITS Development Updates and Discussion Thread
Post by: Ictogan on 07/18/2017 03:45 pm
...
...
I thought the reason why NASA was working on hypersonic inflatable aerodynamic decelerator technology as well as supporting the Red Dragon mission was to support heavier payloads.
Heavier, yes. But when the lander is greater than 40 tonnes, HIAD will not do the job.  Other systems will be required, such as supersonic retropulsion and biconic shells.
https://solarsystem.nasa.gov/docs/IPPW-8_Short_Course_SRP_Edquist_Final.pdf
40 tons is still a huge Mars lander compared to anything that has been landed there so far.
Title: Re: ITS Development Updates and Discussion Thread
Post by: RonM on 07/18/2017 04:13 pm
...
...
I thought the reason why NASA was working on hypersonic inflatable aerodynamic decelerator technology as well as supporting the Red Dragon mission was to support heavier payloads.
Heavier, yes. But when the lander is greater than 40 tonnes, HIAD will not do the job.  Other systems will be required, such as supersonic retropulsion and biconic shells.
https://solarsystem.nasa.gov/docs/IPPW-8_Short_Course_SRP_Edquist_Final.pdf
40 tons is still a huge Mars lander compared to anything that has been landed there so far.

The NASA DRA 5.0 largest lander was 40 tons, so HIAD can handle what NASA was planning.
Title: Re: ITS Development Updates and Discussion Thread
Post by: ChrML on 07/18/2017 04:24 pm
I'm sure that anyone volunteering for the first flights will be very well aware of the huge risks of the mission. I seriously doubt any launch abort system is planned for the first decade.


Even if it was, I'm not sure adding complexity is the best way of dealing with this. Complexity is a risk by itself, and could even be the cause of the catastrophic failure it was going to prevent.

I think the best way would be a more passive approach to increase survivability in the event of RUD. For example instead of a lunch system, you could design the capsule in a way that an engine/tank explosion would "shoot" the capsule out like a bullet from a gun. Requires reinforceing the walls below and the torpedo wall between. Then add chutes for the landing.
Title: Re: ITS Development Updates and Discussion Thread
Post by: Robotbeat on 07/19/2017 02:31 am
...
...
I thought the reason why NASA was working on hypersonic inflatable aerodynamic decelerator technology as well as supporting the Red Dragon mission was to support heavier payloads.
Heavier, yes. But when the lander is greater than 40 tonnes, HIAD will not do the job.  Other systems will be required, such as supersonic retropulsion and biconic shells.
https://solarsystem.nasa.gov/docs/IPPW-8_Short_Course_SRP_Edquist_Final.pdf
40 tons is still a huge Mars lander compared to anything that has been landed there so far.

The NASA DRA 5.0 largest lander was 40 tons, so HIAD can handle what NASA was planning.
...but not alone. Many concepts propose also using SRP.

All of NASA's human lander designs now baseline SRP thanks to SpaceX.

The point is that none of those lander concepts are being seriously funded by NASA. HIAD is ultimately just a drag device, nothing even remotely close to a full lander.
Title: Re: ITS Development Updates and Discussion Thread
Post by: Jim on 07/19/2017 02:48 am
I'm sure that anyone volunteering for the first flights will be very well aware of the huge risks of the mission. I seriously doubt any launch abort system is planned for the first decade.


Even if it was, I'm not sure adding complexity is the best way of dealing with this. Complexity is a risk by itself, and could even be the cause of the catastrophic failure it was going to prevent.

I think the best way would be a more passive approach to increase survivability in the event of RUD. For example instead of a lunch system, you could design the capsule in a way that an engine/tank explosion would "shoot" the capsule out like a bullet from a gun. Requires reinforceing the walls below and the torpedo wall between. Then add chutes for the landing.

That is not workable.
Title: Re: ITS Development Updates and Discussion Thread
Post by: TomH on 07/19/2017 03:26 am
I think the best way would be a more passive approach to increase survivability in the event of RUD. For example instead of a lunch system, you could design the capsule in a way that an engine/tank explosion would "shoot" the capsule out like a bullet from a gun. Requires reinforceing the walls below and the torpedo wall between. Then add chutes for the landing.

This would require making the tank walls hundreds or even thousands of times thicker. The rocket would be many times heavier than the engines could lift from the ground.

Also, the hundreds to thousands of G-forces would pancake the capsule as well as the astronauts' bodies, killing them instantly.
Title: Re: ITS Development Updates and Discussion Thread
Post by: RonM on 07/19/2017 04:05 am
...
...
I thought the reason why NASA was working on hypersonic inflatable aerodynamic decelerator technology as well as supporting the Red Dragon mission was to support heavier payloads.
Heavier, yes. But when the lander is greater than 40 tonnes, HIAD will not do the job.  Other systems will be required, such as supersonic retropulsion and biconic shells.
https://solarsystem.nasa.gov/docs/IPPW-8_Short_Course_SRP_Edquist_Final.pdf
40 tons is still a huge Mars lander compared to anything that has been landed there so far.

The NASA DRA 5.0 largest lander was 40 tons, so HIAD can handle what NASA was planning.
...but not alone. Many concepts propose also using SRP.

All of NASA's human lander designs now baseline SRP thanks to SpaceX.

The point is that none of those lander concepts are being seriously funded by NASA. HIAD is ultimately just a drag device, nothing even remotely close to a full lander.

Yes, SpaceX SRP is a better method. NASA isn't seriously working on any manned spaceflight other than SLS/Orion. No lunar or Mars landers at all. DSG could be useful, but it's just talk unless Congress funds it. That's a good reason to get back on topic. SpaceX is serious about ITS.
Title: Re: ITS Development Updates and Discussion Thread
Post by: Robotbeat on 07/19/2017 05:06 am
Right. ITS is the only serious large Mars lander project in existence (a point which people disagreed with which is why we had that discussion about HIAD, which is just a drag device) and once Falcon 9 block 5 is finished, it should get a lot more serious.
Title: Re: ITS Development Updates and Discussion Thread
Post by: ChrML on 07/19/2017 09:29 am
Quote from: TomH
This would require making the tank walls hundreds or even thousands of times thicker. The rocket would be many times heavier than the engines could lift from the ground.

Also, the hundreds to thousands of G-forces would pancake the capsule as well as the astronauts' bodies, killing them instantly.

Even if you design it weak at strategic places so that just 1% of the force pushes the craft up?
Title: Re: ITS Development Updates and Discussion Thread
Post by: envy887 on 07/19/2017 01:05 pm
Quote from: TomH
This would require making the tank walls hundreds or even thousands of times thicker. The rocket would be many times heavier than the engines could lift from the ground.

Also, the hundreds to thousands of G-forces would pancake the capsule as well as the astronauts' bodies, killing them instantly.

Even if you design it weak at strategic places so that just 1% of the force pushes the craft up?

You really don't wan't to use an uncontrolled explosion to move a spacecraft around. Not only would the spacecraft have to be reinforced against the worst case blast/penetration scenario (which means lots of mass), it has to be be able to be strong (and heavy) enough to take uncontrolled aerodynamic loads at high speeds in dense atmosphere.

For example, it wasn't the disintegrating external tank that destroyed Challenger. The loss of control authority resulted in excessive angle of attack, and then aerodynamic forces broke up the orbiter.

It's much better to use a propulsion system that has control over both acceleration and attitude for escape.
Title: Re: ITS Development Updates and Discussion Thread
Post by: jpo234 on 07/19/2017 01:57 pm
I think the best way would be a more passive approach to increase survivability in the event of RUD. For example instead of a lunch system, you could design the capsule in a way that an engine/tank explosion would "shoot" the capsule out like a bullet from a gun. Requires reinforceing the walls below and the torpedo wall between. Then add chutes for the landing.

Project Orion (https://en.wikipedia.org/wiki/Project_Orion_(nuclear_propulsion)) as a LAS  :o

https://www.youtube.com/watch?v=Q8Sv5y6iHUM
Title: Re: ITS Development Updates and Discussion Thread
Post by: TomH on 07/19/2017 05:27 pm
Quote from: TomH
This would require making the tank walls hundreds or even thousands of times thicker. The rocket would be many times heavier than the engines could lift from the ground.

Also, the hundreds to thousands of G-forces would pancake the capsule as well as the astronauts' bodies, killing them instantly.

Even if you design it weak at strategic places so that just 1% of the force pushes the craft up?

You really don't wan't to use an uncontrolled explosion to move a spacecraft around. Not only would the spacecraft have to be reinforced against the worst case blast/penetration scenario (which means lots of mass), it has to be be able to be strong (and heavy) enough to take uncontrolled aerodynamic loads at high speeds in dense atmosphere.

For example, it wasn't the disintegrating external tank that destroyed Challenger. The loss of control authority resulted in excessive angle of attack, and then aerodynamic forces broke up the orbiter.

It's much better to use a propulsion system that has control over both acceleration and attitude for escape.

This is correct. An engine on an X-15 once exploded during a static test. The rocket plane was bolted down and the total energy release was minuscule in contrast to what we are talking about here. The airframe was subjected to a 50 G surge which lasted probably less than a millisecond. The craft was severely damaged, although pilot Scott Crossfield, once again, miraculously was uninjured.

When a launch abort system pulls or pushes a capsule away from an explosion, the energy applied to acceleration is expended during several seconds rather than all in a millisecond. Think of it this way. You need to go to the store to grab something. The store is a mile away and your motorcycle is out of gas. As an alternative to putting more gas in the tank, you notice there is a 300' high crane next to your house with a 20,000 lb wrecking ball on the end. You arrange to have the wrecking ball swung such that it hits the motorcycle (with you on it) and simply knocks your bike (like an immense croquet mallet) flying through the air to land at the store. That's pretty much analogous to what you have proposed with the rocket.
Title: Re: ITS Development Updates and Discussion Thread
Post by: Robotbeat on 07/22/2017 06:48 pm
I vote a new update thread focusing explicitly on the 9m diameter BFR/BFS.




...

https://twitter.com/elonmusk/status/888813713800785923

Quote from: Elon Musk
A 9m diameter vehicle fits in our existing factories ...
Title: Re: ITS Development Updates and Discussion Thread
Post by: DJPledger on 07/22/2017 07:51 pm
Looks like 21 full size Raptors in 1+6+14 configuration will fit under a 9m dia. core. So basically IAC2016 ITS booster minus the outer ring of Raptors. Raptor thrust will have to be a bit lower than IAC2016 figure if new ITS booster has 21 Raptors to keep within 12Mlbf limit of LC-39A. We will have to wait until IAC2017 to find out how many Raptors the new smaller ITS booster will have.
Title: Re: ITS Development Updates and Discussion Thread
Post by: vaporcobra on 07/22/2017 08:06 pm
I vote a new update thread focusing explicitly on the 9m diameter BFR/BFS.




...

https://twitter.com/elonmusk/status/888813713800785923

Quote from: Elon Musk
A 9m diameter vehicle fits in our existing factories ...

Agreed. New focused thread would be worthwhile. Before a mod actually creates one, I went ahead.

http://forum.nasaspaceflight.com/index.php?topic=43427.0 (http://forum.nasaspaceflight.com/index.php?topic=43427.0)
Title: Re: ITS Development Updates and Discussion Thread
Post by: MikeAtkinson on 07/22/2017 08:27 pm
Looks like 21 full size Raptors in 1+6+14 configuration will fit under a 9m dia. core. So basically IAC2016 ITS booster minus the outer ring of Raptors. Raptor thrust will have to be a bit lower than IAC2016 figure if new ITS booster has 21 Raptors to keep within 12Mlbf limit of LC-39A. We will have to wait until IAC2017 to find out how many Raptors the new smaller ITS booster will have.

If you take the original design and scale it to use the subscale Raptor (1 MN) instead of the full size Raptor (3 MN) then the dimensions scale by cubed root of three. So the 12 m diameter of the full size would scale to 8.4 m.

Suggest that 42 subscale Raptor are used on 1st stage and that they hope to increase thrust to a bit more than 1 MN.
Title: Re: ITS Development Updates and Discussion Thread
Post by: M.E.T. on 07/22/2017 08:29 pm
Looks like 21 full size Raptors in 1+6+14 configuration will fit under a 9m dia. core. So basically IAC2016 ITS booster minus the outer ring of Raptors. Raptor thrust will have to be a bit lower than IAC2016 figure if new ITS booster has 21 Raptors to keep within 12Mlbf limit of LC-39A. We will have to wait until IAC2017 to find out how many Raptors the new smaller ITS booster will have.

If you take the original design and scale it to use the subscale Raptor (1 MN) instead of the full size Raptor (3 MN) then the dimensions scale by cubed root of three. So the 12 m diameter of the full size would scale to 8.4 m.

Suggest that 42 subscale Raptor are used on 1st stage and that they hope to increase thrust to a bit more than 1 MN.

A new thread has been created for the 9m rocket. But just to respond, surely fewer engines provide a reduced risk compared to more engines. Why would they stick to the subscale Raptor?
Title: Re: ITS Development Updates and Discussion Thread
Post by: DJPledger on 07/22/2017 08:48 pm
Looks like 21 full size Raptors in 1+6+14 configuration will fit under a 9m dia. core. So basically IAC2016 ITS booster minus the outer ring of Raptors. Raptor thrust will have to be a bit lower than IAC2016 figure if new ITS booster has 21 Raptors to keep within 12Mlbf limit of LC-39A. We will have to wait until IAC2017 to find out how many Raptors the new smaller ITS booster will have.

If you take the original design and scale it to use the subscale Raptor (1 MN) instead of the full size Raptor (3 MN) then the dimensions scale by cubed root of three. So the 12 m diameter of the full size would scale to 8.4 m.

Suggest that 42 subscale Raptor are used on 1st stage and that they hope to increase thrust to a bit more than 1 MN.

A new thread has been created for the 9m rocket. But just to respond, surely fewer engines provide a reduced risk compared to more engines. Why would they stick to the subscale Raptor?
Perhaps use the subscale Raptor for the 9m dia. ITS ship to keep it's engine out capability and use the full size Raptor for the 9m dia. ITS booster to keep engine no. to not more than 21 which is still pushing it for engine no. for my liking. 42 engines is far too many and EM has already admitted that even 27 engines lighting up at once is a serious cause for concern.
Title: Re: ITS Development Updates and Discussion Thread
Post by: MikeAtkinson on 07/22/2017 09:19 pm
A new thread has been created for the 9m rocket. But just to respond, surely fewer engines provide a reduced risk compared to more engines. Why would they stick to the subscale Raptor?

Full scale Raptor is probably 2-3 years behind the subscale one.
Title: Re: ITS Development Updates and Discussion Thread
Post by: MikeAtkinson on 07/22/2017 09:23 pm
42 engines is far too many and EM has already admitted that even 27 engines lighting up at once is a serious cause for concern.

My understanding is that the reasons that 27 engines is a concern is to do with having 3 cores
Title: Re: ITS Development Updates and Discussion Thread
Post by: Exastro on 07/22/2017 10:12 pm
42 engines is far too many and EM has already admitted that even 27 engines lighting up at once is a serious cause for concern.

My understanding is that the reasons that 27 engines is a concern is to do with having 3 cores

Not an expert here, but from EM's ISS interview I had the impression that the issue had more to do with the acoustic environment than with the raw engine count.  Acoustic power ought to scale with total thrust.
Title: Re: ITS Development Updates and Discussion Thread
Post by: envy887 on 07/23/2017 01:27 am
42 engines is far too many and EM has already admitted that even 27 engines lighting up at once is a serious cause for concern.

My understanding is that the reasons that 27 engines is a concern is to do with having 3 cores

Not an expert here, but from EM's ISS interview I had the impression that the issue had more to do with the acoustic environment than with the raw engine count.  Acoustic power ought to scale with total thrust.

More like the connections between the boosters are nowhere near as strong as the internal connections in the octoweb. They really don't want one booster to try flying off without the other two...
Title: Re: ITS Development Updates and Discussion Thread
Post by: Exastro on 07/23/2017 03:08 am
42 engines is far too many and EM has already admitted that even 27 engines lighting up at once is a serious cause for concern.

My understanding is that the reasons that 27 engines is a concern is to do with having 3 cores

Not an expert here, but from EM's ISS interview I had the impression that the issue had more to do with the acoustic environment than with the raw engine count.  Acoustic power ought to scale with total thrust.

More like the connections between the boosters are nowhere near as strong as the internal connections in the octoweb. They really don't want one booster to try flying off without the other two...


Is that really true?  It seems to me SpaceX has already demonstrated pretty fine control over the booster trajectory during powered landings, so there shouldn't be large undesired thrust vector components in flight.  And on the ground where you'd worry about startup transients all the cores are being held down.

The two things I'd be worried about are differential buffeting (probably worst near max-Q) and engine failures.  The first has nothing to do with large engine count and second is probably mitigated by it.

What am I missing here?
Title: Re: ITS Development Updates and Discussion Thread
Post by: octavo on 07/23/2017 08:23 am
IANARS, but I don't think you can ever rely on the engines starting exactly simultaneously and there are probably scenarios where microsecond differentials in the wrong engines could cause just enough torque to strain the inter-booster connections.

Out of an abundance of caution, is probably safer to start then in symmetric groups a few tens of milliseconds apart to even out any torquing
Title: Re: ITS Development Updates and Discussion Thread
Post by: Oli on 07/23/2017 01:44 pm
IANARS, but I don't think you can ever rely on the engines starting exactly simultaneously and there are probably scenarios where microsecond differentials in the wrong engines could cause just enough torque to strain the inter-booster connections.

To my knowledge the boosters are being held down until thrust has built up.
Title: Re: ITS Development Updates and Discussion Thread
Post by: Lars-J on 07/23/2017 07:37 pm
A new thread has been created for the 9m rocket. But just to respond, surely fewer engines provide a reduced risk compared to more engines. Why would they stick to the subscale Raptor?

Full scale Raptor is probably 2-3 years behind the subscale one.

Hardly. Full scale raptor is the real thing end product. The subscale one is just a temporary development tool. They spent a lot of time figuring out the optimal engine size. (Scale matters)
Title: Re: ITS Development Updates and Discussion Thread
Post by: Robotbeat on 07/24/2017 01:58 am
A new thread has been created for the 9m rocket. But just to respond, surely fewer engines provide a reduced risk compared to more engines. Why would they stick to the subscale Raptor?

Full scale Raptor is probably 2-3 years behind the subscale one.

Hardly. Full scale raptor is the real thing end product. The subscale one is just a temporary development tool. They spent a lot of time figuring out the optimal engine size. (Scale matters)
I don't think you know all that for a fact.

Merlin increased in thrust by a factor of 3 from the original. SpaceX may be planning to do the same thing with Raptor.
Title: Re: ITS Development Updates and Discussion Thread
Post by: Lars-J on 07/24/2017 02:31 am
A new thread has been created for the 9m rocket. But just to respond, surely fewer engines provide a reduced risk compared to more engines. Why would they stick to the subscale Raptor?

Full scale Raptor is probably 2-3 years behind the subscale one.

Hardly. Full scale raptor is the real thing end product. The subscale one is just a temporary development tool. They spent a lot of time figuring out the optimal engine size. (Scale matters)
I don't think you know all that for a fact.

Merlin increased in thrust by a factor of 3 from the original. SpaceX may be planning to do the same thing with Raptor.

Anything is theoretically possible I suppose (quantum physics and all that) ;), but that doesn't make it likely. And SpaceX has a LOT more experience now, compared to what they knew when starting Merlin work. Don't expect the first (real) Raptor to be the equivalent of Merlin 1A.

Again, engines can't just be scaled down or up without massive work. If you *really* think that when scaling down a LV with 42(!!!) engines, the most logical choice is for them to just use 42 smaller engines instead of reducing complexity by having a more reasonable number of engines of the original size... Then by all means, believe that. I'll gladly make a bet with you that the new, smaller ITS/BFR booster will have far fewer engines than 42.
Title: Re: ITS Development Updates and Discussion Thread
Post by: Robotbeat on 07/24/2017 11:07 am
No, I don't think it's just automatically the most logical choice. But it is a real possibility.
Title: Re: ITS Development Updates and Discussion Thread
Post by: Lars-J on 07/24/2017 03:07 pm
No, I don't think it's just automatically the most logical choice. But it is a real possibility.

Perhaps. We'll have to wait and see! (never boring with SpaceX!)  ;D
Title: Re: ITS Development Updates and Discussion Thread
Post by: DOCinCT on 07/24/2017 03:47 pm
Is the sub-scale Raptor engine a smaller version or just one operating way below maximum capability?
Title: Re: ITS Development Updates and Discussion Thread
Post by: Peter.Colin on 07/24/2017 06:03 pm
A new thread has been created for the 9m rocket. But just to respond, surely fewer engines provide a reduced risk compared to more engines. Why would they stick to the subscale Raptor?

Full scale Raptor is probably 2-3 years behind the subscale one.

Hardly. Full scale raptor is the real thing end product. The subscale one is just a temporary development tool. They spent a lot of time figuring out the optimal engine size. (Scale matters)
I don't think you know all that for a fact.

Merlin increased in thrust by a factor of 3 from the original. SpaceX may be planning to do the same thing with Raptor.

Anything is theoretically possible I suppose (quantum physics and all that) ;), but that doesn't make it likely. And SpaceX has a LOT more experience now, compared to what they knew when starting Merlin work. Don't expect the first (real) Raptor to be the equivalent of Merlin 1A.

Again, engines can't just be scaled down or up without massive work. If you *really* think that when scaling down a LV with 42(!!!) engines, the most logical choice is for them to just use 42 smaller engines instead of reducing complexity by having a more reasonable number of engines of the original size... Then by all means, believe that. I'll gladly make a bet with you that the new, smaller ITS/BFR booster will have far fewer engines than 42.

I also believe the mini-BFR could contain 42 sub-scale Raptor engines.
How much do you want to bet, $50 ?  :)

For testing the landing in a cradle they could use 7 real Raptors and 35 dummy engines first.
Load it with much less fuel so it can take off, hover and land, later on more engines can be added.
21 real raptors and 21 dummies half fueled could be done to reach orbit without payload, and practice cradle landing from there.

Title: Re: ITS Development Updates and Discussion Thread
Post by: Lars-J on 07/24/2017 07:45 pm
You are willing to bet on a scaled down ITS having exactly 42 engines? (as if SpaceX main design goal was 42 engines instead of a result of what could fit in 12m diameter) A bet with that level of specificity feels like taking candy from a baby.
Title: Re: ITS Development Updates and Discussion Thread
Post by: Jim on 07/24/2017 07:46 pm

I also believe the mini-BFR could contain 42 sub-scale Raptor engines.
How much do you want to bet, $50 ?  :)


What make you think that sub-scale Raptor engines are going to be used for flight?
Title: Re: ITS Development Updates and Discussion Thread
Post by: Peter.Colin on 07/24/2017 09:18 pm
You are willing to bet on a scaled down ITS having exactly 42 engines? (as if SpaceX main design goal was 42 engines instead of a result of what could fit in 12m diameter) A bet with that level of specificity feels like taking candy from a baby.

Yes exactly 42 engines, easy money right?  ;)
I'm not 100% sure but see it as the most likely option.

I do believe it is more logical to first design an optimal engine layout, and then make it fitting. So 42 engines was the primary design spec and the 12 meter diameter the secondary.
So first design an engine layout this results in an 1/6/14/21 layout (sum = "42"), than extrapolate the diameter of the core out of the engine diameter.

The real reason for going to 9 meter instead of 12 meter might be that the optimal engine diameter is less than anticipated, and not that 12 meter is more expensive.
Making the updated design more economically viable might relate only to the spaceship being capable of launching hundreds of satellites at once, and not the reduced size of the rocket.
Title: Re: ITS Development Updates and Discussion Thread
Post by: philw1776 on 07/24/2017 09:24 pm
You are willing to bet on a scaled down ITS having exactly 42 engines? (as if SpaceX main design goal was 42 engines instead of a result of what could fit in 12m diameter) A bet with that level of specificity feels like taking candy from a baby.

Yes exactly 42 engines.
I'm not fully sure but willing to bet because I see it as the most likely option.

Conversely, I would be absolutely shocked were that the case.
Title: Re: ITS Development Updates and Discussion Thread
Post by: Lars-J on 07/24/2017 09:30 pm
You are willing to bet on a scaled down ITS having exactly 42 engines? (as if SpaceX main design goal was 42 engines instead of a result of what could fit in 12m diameter) A bet with that level of specificity feels like taking candy from a baby.

Yes exactly 42 engines.
I'm not fully sure but willing to bet because I see it as the most likely option.

Ok... How about a $10 bet, then? My bet is that the "new ITS design", to be revealed in September by Elon, does not have 42 engines on the first stage. If it has 42 engines, you win. Otherwise I win. Deal?
Title: Re: ITS Development Updates and Discussion Thread
Post by: wannamoonbase on 07/24/2017 09:37 pm
You are willing to bet on a scaled down ITS having exactly 42 engines? (as if SpaceX main design goal was 42 engines instead of a result of what could fit in 12m diameter) A bet with that level of specificity feels like taking candy from a baby.

Yes exactly 42 engines.
I'm not fully sure but willing to bet because I see it as the most likely option.

Conversely, I would be absolutely shocked were that the case.

I agree, there is far more value in flying the final engines and gaining flight experience than fitting the same number of engines.  Build what you ultimately need and fly them.

This 'scaled' could ultimately last decades.  Why handicap yourself to the idea of a rocket that:
A) May never get built
B) Could change from it's intended design before it ever got built.
Title: Re: ITS Development Updates and Discussion Thread
Post by: scienceguy on 07/24/2017 09:38 pm
Don't forget, Elon has a sense of humor. He flew a piece of cheese. I wouldn't be surprised if he liked the number 42 for some reason regarding the universe and everything.
Title: Re: ITS Development Updates and Discussion Thread
Post by: spacenut on 07/24/2017 09:39 pm
The current prototype is 225,000 lbs thrust.  That is about 9,450,000 lbs thrust.  12 milliion is the max for the launch pad. 

The full Raptor is to be about 685,000 lbs thrust, that would equate to 17.5 Raptors for the new design to keep under 12 million.  It will probably be somewhere between 15-21 Raptors.  Probably closer to 21, because it can throttle down at launch and up after lift off or to have some play for engine out.  42 would be a heck of a lot of plumbing that may not be necessary.  It all depends on how many full thrust Raptors they can get under a 9m core.

Another limitation on engines is how many would be needed on the booster to launch a 9m diameter ITS.  The ITS weight fully fueled to make LEO with at least 100 tons of cargo.   
Title: Re: ITS Development Updates and Discussion Thread
Post by: Peter.Colin on 07/24/2017 10:02 pm
You are willing to bet on a scaled down ITS having exactly 42 engines? (as if SpaceX main design goal was 42 engines instead of a result of what could fit in 12m diameter) A bet with that level of specificity feels like taking candy from a baby.

Yes exactly 42 engines.
I'm not fully sure but willing to bet because I see it as the most likely option.

Ok... How about a $10 bet, then? My bet is that the "new ITS design", to be revealed in September by Elon, does not have 42 engines on the first stage. If it has 42 engines, you win. Otherwise I win. Deal?

I agree!

(And open for anyone who wants to make the same bet)
Title: Re: ITS Development Updates and Discussion Thread
Post by: Peter.Colin on 07/24/2017 10:04 pm
Don't forget, Elon has a sense of humor. He flew a piece of cheese. I wouldn't be surprised if he liked the number 42 for some reason regarding the universe and everything.

Spot on! :)
Title: Re: ITS Development Updates and Discussion Thread
Post by: original_mds on 07/24/2017 11:20 pm
Don't forget, Elon has a sense of humor. He flew a piece of cheese. I wouldn't be surprised if he liked the number 42 for some reason regarding the universe and everything.
Well, he is at least 1/8th British, so he might have inherited a liking for British literature.
Title: Re: ITS Development Updates and Discussion Thread
Post by: envy887 on 07/25/2017 03:14 pm
IANARS, but I don't think you can ever rely on the engines starting exactly simultaneously and there are probably scenarios where microsecond differentials in the wrong engines could cause just enough torque to strain the inter-booster connections.

To my knowledge the boosters are being held down until thrust has built up.

The STS stack was held down, but that didn't stop it from twisting when the SSMEs lit off... and they were also lit sequentially.
Title: Re: ITS Development Updates and Discussion Thread
Post by: Zed_Noir on 07/26/2017 04:50 am
You are willing to bet on a scaled down ITS having exactly 42 engines? (as if SpaceX main design goal was 42 engines instead of a result of what could fit in 12m diameter) A bet with that level of specificity feels like taking candy from a baby.

Yes exactly 42 engines.
I'm not fully sure but willing to bet because I see it as the most likely option.

Ok... How about a $10 bet, then? My bet is that the "new ITS design", to be revealed in September by Elon, does not have 42 engines on the first stage. If it has 42 engines, you win. Otherwise I win. Deal?

@Lars-J
A Reminder that Elon have already name the first crewed BFS planted on Mars as the "Heart of Gold". So the answer to the ultimate question of how many Raptord the ITSy have is 42.  ;D
Title: Re: ITS Development Updates and Discussion Thread
Post by: Lars-J on 07/26/2017 04:30 pm
@Lars-J
A Reminder that Elon have already name the first crewed BFS planted on Mars as the "Heart of Gold". So the answer to the ultimate question of how many Raptord the ITSy have is 42.  ;D

Geez, you people. What do you think came first? That name or the presentation of 42 engines? (Hint, check twitter timelines) You *really* think that SpaceX makes engineering decisions based primarily on Douglas Adams writings?
Do you want to take this bet too? Because this is the easiest money I will ever make.  8)
Title: Re: ITS Development Updates and Discussion Thread
Post by: spacenut on 07/26/2017 06:09 pm
Unless there are major roadblocks to go from the 225k lb thrust engine to full thrust on Raptor, I can't see the need for 42 engines.  I looked at 9m circle, and you could have 21 engines, 8 around 1 like on F9, then add 12 on the outside.  You can go 6 around 1 and 12 on the outside for for 19 engines.  42 might fit if they are exactly the same size as Merlins.  I just don't see that happening.  Center engine could be used for landing and maybe a couple of others, and not have to throttle them down much. 

I just wonder what will be the final thrust of the engine.  I'm sure Musk wants to get as close to 12 million lbs and not go over the flame trench limitations.  That would give him a lot more flexibility for the ITS spacecraft.  Too few and too little thrust, doesn't give the ITS spacecraft enough weight and payload capability.  Too many little ones could be a problem with a new rocket. 
Title: Re: ITS Development Updates and Discussion Thread
Post by: rsdavis9 on 07/26/2017 06:16 pm
@Lars-J
A Reminder that Elon have already name the first crewed BFS planted on Mars as the "Heart of Gold". So the answer to the ultimate question of how many Raptord the ITSy have is 42.  ;D

Geez, you people. What do you think came first? That name or the presentation of 42 engines? (Hint, check twitter timelines) You *really* think that SpaceX makes engineering decisions based primarily on Douglas Adams writings?
Do you want to take this bet too? Because this is the easiest money I will ever make.  8)

I think the chief engineer can specify whatever he wants for a paper rocket design. And knowing musk's humor I think he would do it.
Title: Re: ITS Development Updates and Discussion Thread
Post by: Peter.Colin on 07/26/2017 06:23 pm
Unless there are major roadblocks to go from the 225k lb thrust engine to full thrust on Raptor, I can't see the need for 42 engines.  I looked at 9m circle, and you could have 21 engines, 8 around 1 like on F9, then add 12 on the outside.  You can go 6 around 1 and 12 on the outside for for 19 engines.  42 might fit if they are exactly the same size as Merlins.  I just don't see that happening.  Center engine could be used for landing and maybe a couple of others, and not have to throttle them down much. 

I just wonder what will be the final thrust of the engine.  I'm sure Musk wants to get as close to 12 million lbs and not go over the flame trench limitations.  That would give him a lot more flexibility for the ITS spacecraft.  Too few and too little thrust, doesn't give the ITS spacecraft enough weight and payload capability.  Too many little ones could be a problem with a new rocket.




Exact scaling of the 9 meter design would result in (9/12)^3 = 0,42 times the mass of the original.

Scaling the thrust with the same mass factor results in: 685k Lbs *0,42 = 288k Lbs of thrust

288 X 42 coincidently equals your 12 million flame trench limit 8)
Title: Re: ITS Development Updates and Discussion Thread
Post by: original_mds on 07/26/2017 06:40 pm
Unless there are major roadblocks to go from the 225k lb thrust engine to full thrust on Raptor, I can't see the need for 42 engines.  I looked at 9m circle, and you could have 21 engines, 8 around 1 like on F9, then add 12 on the outside.  You can go 6 around 1 and 12 on the outside for for 19 engines.  42 might fit if they are exactly the same size as Merlins.  I just don't see that happening.  Center engine could be used for landing and maybe a couple of others, and not have to throttle them down much. 

I just wonder what will be the final thrust of the engine.  I'm sure Musk wants to get as close to 12 million lbs and not go over the flame trench limitations.  That would give him a lot more flexibility for the ITS spacecraft.  Too few and too little thrust, doesn't give the ITS spacecraft enough weight and payload capability.  Too many little ones could be a problem with a new rocket.




Exact scaling of the 9 meter design would result in (9/12)^3 = 0,42 times the mass of the original.

Scaling the thrust with the same mass factor results in: 685k Lbs *0,42 = 288k Lbs of thrust

288 X 42 coincidently equals your 12 million flame trench limit 8)

Is there a configuration that easily facilitates dropping 1-3 engines?  Performance improvements that are typical as a design matures could result in a desire to shed some of the engines rather than throttle down durring lift off (to stay within the flame trench limits and structural margins of the booster).
Title: Re: ITS Development Updates and Discussion Thread
Post by: Peter.Colin on 07/26/2017 07:07 pm
Unless there are major roadblocks to go from the 225k lb thrust engine to full thrust on Raptor, I can't see the need for 42 engines.  I looked at 9m circle, and you could have 21 engines, 8 around 1 like on F9, then add 12 on the outside.  You can go 6 around 1 and 12 on the outside for for 19 engines.  42 might fit if they are exactly the same size as Merlins.  I just don't see that happening.  Center engine could be used for landing and maybe a couple of others, and not have to throttle them down much. 

I just wonder what will be the final thrust of the engine.  I'm sure Musk wants to get as close to 12 million lbs and not go over the flame trench limitations.  That would give him a lot more flexibility for the ITS spacecraft.  Too few and too little thrust, doesn't give the ITS spacecraft enough weight and payload capability.  Too many little ones could be a problem with a new rocket.




Exact scaling of the 9 meter design would result in (9/12)^3 = 0,42 times the mass of the original.

Scaling the thrust with the same mass factor results in: 685k Lbs *0,42 = 288k Lbs of thrust

288 X 42 coincidently equals your 12 million flame trench limit 8)

Is there a configuration that easily facilitates dropping 1-3 engines?  Performance improvements that are typical as a design matures could result in a desire to shed some of the engines rather than throttle down durring lift off (to stay within the flame trench limits and structural margins of the booster).


The original configuration faciilitates dropping a few engines and still continue the mission normally.
So the exact scaled configuration would probably be capable of the same.
Shutting down or removing these redundant engines is less safe.
Throttle down during take-off is a valid option.

Because SpaceX can now land rockets, the mini-BFR could be tested with an incremental number of engines.
This is less costly when the booster fails and saves time because you don't need the 42 engines to be produced before test flights can begin.
They could test cradle landings first with only 7 engines and 35 dummy engines. (Less fuel = less weight)
And then reach orbit with let's say 21 engines without payload, to practice re-entry and landing.
42 engines can be installed to test the full system.

Title: Re: ITS Development Updates and Discussion Thread
Post by: wannamoonbase on 07/26/2017 08:05 pm
I think there is far more value in flying the final engine and getting history with that than flying sub-scale engines that don't make the final vehicle.

Title: Re: ITS Development Updates and Discussion Thread
Post by: rsdavis9 on 07/26/2017 08:12 pm
The goal is to get launching large payloads to LEO and GEO FAST. Reusable both stages as soon as possible.
A good goal before fully reusable might be to just have the booster reusable. You would still be getting things to orbit and getting paid.

I think they may temporarily drop:
1. Cradle landing for 1st stage
2. composite tanks
3. 2nd stage landing. Leave off heat shield, flaps, COG balancer.

As they achieve orbit and delivery start finishing them in reverse order.
1. 2nd stage landing. Add back missing stuff
2. change what wasn't composite from first run to all composite.
3. Any other fancy add ons like cradle landing.

Title: Re: ITS Development Updates and Discussion Thread
Post by: Peter.Colin on 07/26/2017 08:13 pm
I think there is far more value in flying the final engine and getting history with that than flying sub-scale engines that don't make the final vehicle.

The 288k lbs Raptor engine might be the final engine!
The 12 meter BFR might need around 100 engines.

42 engines /0,42 scaling factor = 100 engines.

Title: Re: ITS Development Updates and Discussion Thread
Post by: Nomadd on 07/26/2017 08:32 pm
 They could always do it like the Merlin. Start out small and wind up getting 2 1/2 times the thrust in the final version. Remember when the goal was 125,000 lbs?
Title: Re: ITS Development Updates and Discussion Thread
Post by: spacenut on 07/26/2017 08:56 pm
I think that is what Musk has in mind.  They have the small engine at 225k lbs now, and I am assuming it is operating at the Merlin pressures.  Musk said the pressure for the full thrust Raptor will be several times the Merlin or 685k lbs for the maximum designed thrust.  Nozzles and the throat of the engine would probably have to change.  Theory has it with 685k engine from 19-21 engines would be used in a 1-6-12 ring or 1-8-12 ring.  This would seem to be easier and less costly by just improving the engine to full thrust before rocket construction begins.  Less engines = less cost, if they use almost the same components of the 225k engine.  The engine is not much bigger than Merlin.

Now, Musk may have developed the 225k engine first because of the Air Force money to develop and upper stage metholox engine, which they basically have except for the larger engine bell.  Also, a smaller engine may be needed on the ITS upper stage/Mars lander vehicle.  Mars gravity is lighter and they may not need bigger engines, but they would need a sea level engine to land back on earth.  ITS would be lighter when landing on earth and vacuum engine would not be needed to land on earth. 

I see them going to the more powerful engine with more thrust than using 42 engines because of shear cost of the engines.  Merlin cost about $1 million each.  The 225K engine probably about the same.  $42 million just for engines?  Now, an upgraded engine to 685k lbs thrust may cost $1.5 million, so that would be about $22 million for around 20 engines.  Half the price.  Then when and if they build the 12 meter BFR/ITS, they can add an outer ring of 21 engines for 42 engines and use the same plumbing scheme for the inner engines of the 12m rocket.  Yes, it may be 20 years before the huge rocket is built, but they are on the right track. 
Title: Re: ITS Development Updates and Discussion Thread
Post by: guckyfan on 07/26/2017 09:04 pm
I think it was said the Stennis test stand does not support full scale components. The subscale Raptor may be in line with what they could test at Stennis.
Title: Re: ITS Development Updates and Discussion Thread
Post by: hkultala on 07/26/2017 09:14 pm
I think that is what Musk has in mind.  They have the small engine at 225k lbs now, and I am assuming it is operating at the Merlin pressures.

I don't see much point of making staged combustion engine and only running it at gas generator-level pressures. The isp increase over gas generator engine would be quit small, but staged combustion engine is still much more complex to design and manufacture.

Quote
Musk said the pressure for the full thrust Raptor will be several times the Merlin or 685k lbs for the maximum designed thrust.  Nozzles and the throat of the engine would probably have to change.  Theory has it with 685k engine from 19-21 engines would be used in a 1-6-12 ring or 1-8-12 ring.  This would seem to be easier and less costly by just improving the engine to full thrust before rocket construction begins.  Less engines = less cost, if they use almost the same components of the 225k engine.  The engine is not much bigger than Merlin.

Now, Musk may have developed the 225k engine first because of the Air Force money to develop and upper stage metholox engine, which they basically have except for the larger engine bell.  Also, a smaller engine may be needed on the ITS upper stage/Mars lander vehicle.  Mars gravity is lighter and they may not need bigger engines, but they would need a sea level engine to land back on earth.  ITS would be lighter when landing on earth and vacuum engine would not be needed to land on earth. 

I see them going to the more powerful engine with more thrust than using 42 engines because of shear cost of the engines.  Merlin cost about $1 million each.  The 225K engine probably about the same.

Full flow staged combustion is much more complex than simple gas generator engine so it will also be much more expensive to make. Compare the price difference of RS-25 and RS-68, RS-68 is even much more powerful than RS-25 but still much cheaper, and RS-25 is not even full flow but fuel rich.
Title: Re: ITS Development Updates and Discussion Thread
Post by: spacenut on 07/26/2017 11:36 pm
So is the sub-scale Raptor staged combustion or gas generator? 
Title: Re: ITS Development Updates and Discussion Thread
Post by: Robotbeat on 07/26/2017 11:42 pm
So is the sub-scale Raptor staged combustion or gas generator?
Staged combustion.
Title: Re: ITS Development Updates and Discussion Thread
Post by: spacenut on 07/26/2017 11:48 pm
So, it can increase in thrust as is right?  If the engine is designed to handle the increase?
Title: Re: ITS Development Updates and Discussion Thread
Post by: livingjw on 07/27/2017 02:04 am
So, it can increase in thrust as is right?  If the engine is designed to handle the increase?

It will be a scaled up version of the small one and will need to go through its own development process. This will be a 2 to 4 year process, depending on how Murphy is feeling.

John
Title: Re: ITS Development Updates and Discussion Thread
Post by: spacenut on 07/27/2017 02:17 am
Hopefully it will be 2 years.  I've been waiting for us to go to Mars since we went to the moon.  I was 16 when they landed on the moon.  Von Braun said we could get to Mars by 1986 using large Saturn V modules assembled in Space, if we continued producing Saturn V's.  From what I read back then, we were going to upgrade Saturn V to 11 million Lbs thrust.  The F-1 engines were to be upgraded to 1.8 or 1.9 million lbs thrust.  The J-2 engines were going to be upgraded from 200k lbs thrust to 250k lbs thrust.  Then a 10m 3rd stage assembled with others with habitat units, a lander, etc. and then off to Mars. 

Of course you know the history.  Cuts, and abandoning Saturn and building shuttle. 

It was also suggested landing the Saturn V booster in the ocean with parachutes to make it reusable.  Lots of Saturn based ideas back then. 

SpaceX is the only one keeping hopes alive for us space nuts of going to Mars and reusable rockets. 
Title: Re: ITS Development Updates and Discussion Thread
Post by: Robotbeat on 07/27/2017 02:19 am
Or they could decide to use the Raptors as they are and just stretch the BFR as thrust is increased.

Just like Falcon 9.
Title: Re: ITS Development Updates and Discussion Thread
Post by: livingjw on 07/27/2017 02:42 am
Or they could decide to use the Raptors as they are and just stretch the BFR as thrust is increased.

Just like Falcon 9.

The Raptor as it is now is 1/3rd the needed size. You are going to need the full size Raptor.

John
Title: Re: ITS Development Updates and Discussion Thread
Post by: Robotbeat on 07/27/2017 03:21 am
Or they could decide to use the Raptors as they are and just stretch the BFR as thrust is increased.

Just like Falcon 9.

The Raptor as it is now is 1/3rd the needed size. You are going to need the full size Raptor.

John
Merlin 1D is now capable of 3x the thrust of the original Merlin engine.
Title: Re: ITS Development Updates and Discussion Thread
Post by: livingjw on 07/27/2017 03:44 am
Or they could decide to use the Raptors as they are and just stretch the BFR as thrust is increased.

Just like Falcon 9.

The Raptor as it is now is 1/3rd the needed size. You are going to need the full size Raptor.

John
Merlin 1D is now capable of 3x the thrust of the original Merlin engine.

Should have said the Raptor is at 1/3 the needed thrust. Will need about 3 times that much. My impression is that the current demo Raptor was already at pretty high pressure. They will have to grow the engine. That's all.

John
Title: Re: ITS Development Updates and Discussion Thread
Post by: Peter.Colin on 07/27/2017 05:48 am
Suppose a half thrust Raptor engine is already at optimal performance. (Maximum impulse per mass fuel burnt)

What would justify making a bigger engine if it was already at optimal performance?
Wouldn't it be far better to use more Raptor engines instead of larger version Raptor engines ?

Wouldn't the engines become disproportionally heavy? (Thrust to engine weight ratio drops?)
Also would a larger than optimal size Raptor engine not also put more stress on the engine material itself?

Probably a smaller engine is easier to mass produce, and thus cheaper per thrust unit of the rocket.

A bigger Raptor engine isn't automatically a more efficient engine, there is an optimal size.
It wouldn't surprise me that the optimal size of a Raptor engine is around half the size of a Merlin engine.
Title: Re: ITS Development Updates and Discussion Thread
Post by: Lars-J on 07/27/2017 06:01 am
A lot of supposition and logic steps based on "what-if" there. Following your logic, they should just keep shrinking them. The smaller, the better, right? What about 420 engines!

We know that SpaceX is targeting a optimal engine size ( https://twitter.com/elonmusk/status/780280440401764353?lang=en ), weighing factors such as T/W ratio, development cost, and integration complexity. See his Reddit AMA comment from two years ago... (so a year before ITS reveal): https://www.reddit.com/r/IAmA/comments/2rgsan/i_am_elon_musk_ceocto_of_a_rocket_company_ama/cnfpuwi/
Quote
Thrust to weight is optimizing for a surprisingly low thrust level, even when accounting for the added mass of plumbing and structure for many engines. Looks like a little over 230 metric tons (~500 klbf) of thrust per engine, but we will have a lot of them :)
(so this is from before ITS, but this still was a larger engine than the subscale development engine)

But nothing is going to convince you, so what's the point? You are just hunting for justifications for your belief in the holy number of 42...
Title: Re: ITS Development Updates and Discussion Thread
Post by: hkultala on 07/27/2017 06:27 am
Or they could decide to use the Raptors as they are and just stretch the BFR as thrust is increased.

Just like Falcon 9.

The Raptor as it is now is 1/3rd the needed size. You are going to need the full size Raptor.

John
Merlin 1D is now capable of 3x the thrust of the original Merlin engine.

2.6 times, not 3 times, and the original merlin 1A was engine made and developed very cheaply, just to get _something_ running for the falcon 1, and the original merlin 1A used a very low chamber pressure. When you start from very low, there is lots of space to go higher.

Most rocket engines have gained something like only 10-15% thrust increases during their >20 year lifespans.
Title: Re: ITS Development Updates and Discussion Thread
Post by: Peter.Colin on 07/27/2017 06:38 am
A lot of supposition and logic steps based on "what-if" there. Following your logic, they should just keep shrinking them. The smaller, the better, right? What about 420 engines!

We know that SpaceX is targeting a optimal engine size ( https://twitter.com/elonmusk/status/780280440401764353?lang=en ), weighing factors such as T/W ratio, development cost, and integration complexity. See his Reddit AMA comment from two years ago... (so a year before ITS reveal): https://www.reddit.com/r/IAmA/comments/2rgsan/i_am_elon_musk_ceocto_of_a_rocket_company_ama/cnfpuwi/
Quote
Thrust to weight is optimizing for a surprisingly low thrust level, even when accounting for the added mass of plumbing and structure for many engines. Looks like a little over 230 metric tons (~500 klbf) of thrust per engine, but we will have a lot of them :)
(so this is from before ITS, but this still was a larger engine than the subscale development engine)

But nothing is going to convince you, so what's the point? You are just hunting for justifications for your belief in the holy number of 42...

I can imagine you falling off your chair in September when seeing 42 Raptor engines in the 9 meter BFR. :)
I said I'm not 100% sure there's 42 engines, its somewhere between 20 and 43 I think.
And it all depends on the optimal size of the engine.

How much engines do you think are there in the 9 meter BFR?

Title: Re: ITS Development Updates and Discussion Thread
Post by: livingjw on 07/27/2017 11:58 am
A lot of supposition and logic steps based on "what-if" there. Following your logic, they should just keep shrinking them. The smaller, the better, right? What about 420 engines!

We know that SpaceX is targeting a optimal engine size ( https://twitter.com/elonmusk/status/780280440401764353?lang=en ), weighing factors such as T/W ratio, development cost, and integration complexity. See his Reddit AMA comment from two years ago... (so a year before ITS reveal): https://www.reddit.com/r/IAmA/comments/2rgsan/i_am_elon_musk_ceocto_of_a_rocket_company_ama/cnfpuwi/
Quote
Thrust to weight is optimizing for a surprisingly low thrust level, even when accounting for the added mass of plumbing and structure for many engines. Looks like a little over 230 metric tons (~500 klbf) of thrust per engine, but we will have a lot of them :)
(so this is from before ITS, but this still was a larger engine than the subscale development engine)

But nothing is going to convince you, so what's the point? You are just hunting for justifications for your belief in the holy number of 42...

I can imagine you falling off your chair in September when seeing 42 Raptor engines in the 9 meter BFR. :)
I said I'm not 100% sure there's 42 engines, its somewhere between 20 and 43 I think.
And it all depends on the optimal size of the engine.

How much engines do you think are there in the 9 meter BFR?

- Rocket engine performance and thrust to weight are very insensitive to size. They can be scaled up and down within reason (.5-2). Just takes money and time.
- I believe Elon's comment relates to trying to use the same engine on both stages while providing for engine out capability for the second stage. It may also relate to their manufacturing limitations.

John
Title: Re: ITS Development Updates and Discussion Thread
Post by: MATTBLAK on 07/27/2017 12:28 pm
A lot of supposition and logic steps based on "what-if" there. Following your logic, they should just keep shrinking them. The smaller, the better, right? What about 420 engines!

We know that SpaceX is targeting a optimal engine size ( https://twitter.com/elonmusk/status/780280440401764353?lang=en ), weighing factors such as T/W ratio, development cost, and integration complexity. See his Reddit AMA comment from two years ago... (so a year before ITS reveal): https://www.reddit.com/r/IAmA/comments/2rgsan/i_am_elon_musk_ceocto_of_a_rocket_company_ama/cnfpuwi/
Quote
Thrust to weight is optimizing for a surprisingly low thrust level, even when accounting for the added mass of plumbing and structure for many engines. Looks like a little over 230 metric tons (~500 klbf) of thrust per engine, but we will have a lot of them :)
(so this is from before ITS, but this still was a larger engine than the subscale development engine)

But nothing is going to convince you, so what's the point? You are just hunting for justifications for your belief in the holy number of 42...

I can imagine you falling off your chair in September when seeing 42 Raptor engines in the 9 meter BFR. :)
I said I'm not 100% sure there's 42 engines, its somewhere between 20 and 43 I think.
And it all depends on the optimal size of the engine.

How much engines do you think are there in the 9 meter BFR?


I'm guessing 30 engines - e.g. Soviet N-1 :)  But I think with eminently more reliability. People round here 'dummy up' these notional configurations all the time with their fancy software. Can someone do a provisional 'drawing' of the 9 meter end-on view, using the known dimensions of the Merlin 1D as a rule of thumb to get an approximate number of engines? What's the nozzle diameter of the latest Merlins; about 1 meter? Darned if I know...

EDIT: Just did a good old-fashioned pen and paper scale drawing - the circle is 90mm (9cm) or 1/100 scale. The size of a sub scale Raptor is not fully known, but we could say roughly the same as the Merlin 1D nozzle diameter which googling tells me is about 1 meter. In 1/100th scale that would be a 'AAA' scale battery diameter of 10mm. I hedged my bets and used a 'AA' sized battery which is 14mm in diameter. The drawing and placement of the 'nozzle circles is a bit crude and imperfect; but I get 22x engines. That is if the subscale Raptor or Merlin 1D is used on the 9 meter booster.

It could be that because of the inaccuracies in my guesses - it may very well be that actually between 22 and 30 engines could fit there. I doubt 30, though - there needs to be clearance for nozzle swivelling etc, so 22x or very close to that may be the limit. The subscale Raptor apparently puts out about 225,000 pounds thrust (1 meganewton) and 22x of those is slightly less than 5 million pounds at sea level (22 meganewtons). If they use full scale Raptors in this 9 meter stage I'm not sure if they'd get more than about 9 engines on there - assuming they're more than twice the diameter of Merlin 1Ds. This implies a liftoff thrust of about 6.3 million pounds or 28 meganewtons. If I'm wrong about the diameter and fit of the Raptors and up to 16x fit on there - then thats about 11 million pounds of thrust, which sounds about right.
Title: Re: ITS Development Updates and Discussion Thread
Post by: Robotbeat on 07/27/2017 12:40 pm
I kind of suspect something less than Falcon Heavy's 27 engines. Musk already mentioned how much anxiety Falcon Heavy's 27 engines gives him, I kind of suspect that will mean the initial BFR will have fewer engines.

That means that BFR will initially get lower performance if they use subscale Raptor. And I suspect that at least for the first tests, they'll be using somewhat lower thrust Raptors.

I think Falcon Heavy will get away with using that many engines because Merlin 1D has demonstrated very high reliability. But Raptor will be new and thus having that many engines will be a real big challenge.
Title: Re: ITS Development Updates and Discussion Thread
Post by: envy887 on 07/27/2017 01:01 pm
Or they could decide to use the Raptors as they are and just stretch the BFR as thrust is increased.

Just like Falcon 9.

The Raptor as it is now is 1/3rd the needed size. You are going to need the full size Raptor.

John
Merlin 1D is now capable of 3x the thrust of the original Merlin engine.

Should have said the Raptor is at 1/3 the needed thrust. Will need about 3 times that much. My impression is that the current demo Raptor was already at pretty high pressure. They will have to grow the engine. That's all.

John

We don't know if it has reached very high pressure, but we know it was certainly intended to reach very high pressure - as that's the only way to operate a 150:1 nozzle at SL.
Title: Re: ITS Development Updates and Discussion Thread
Post by: DJPledger on 07/27/2017 02:14 pm
I kind of suspect something less than Falcon Heavy's 27 engines. Musk already mentioned how much anxiety Falcon Heavy's 27 engines gives him, I kind of suspect that will mean the initial BFR will have fewer engines.

That means that BFR will initially get lower performance if they use subscale Raptor. And I suspect that at least for the first tests, they'll be using somewhat lower thrust Raptors.

I think Falcon Heavy will get away with using that many engines because Merlin 1D has demonstrated very high reliability. But Raptor will be new and thus having that many engines will be a real big challenge.
I guess initial BFR will have 19 (1+6+12) or 21 (1+6+14) full size Raptors as EM has recently got nervous over using too many engines. The full size BFR will be many years off which gives SpaceX plenty of time to dev. a larger version of Raptor maybe ~7-9MN at SL to keep engine no. same as initial BFR. Once full size Raptor is completed then all they have to do is scale up Raptor by around a factor of 3 for the full size BFR.

I think EM's original idea of 42 Raptors on ITS booster was because he currently has limited funding and it costs a lot of money to dev. an F-1 class or bigger engine to bring engine no. down. Costs a lot less to dev. smaller engine. Once the initial ITS system is launching and SpaceX's sat. constellation is bringing in the revenue then they will be able to afford dev. of a scaled up Raptor of at least F-1 class thrust. So basically ITS system design announced at IAC2016 is a classic example of a funding limited design for a large launch system.
Title: Re: ITS Development Updates and Discussion Thread
Post by: Lars-J on 07/27/2017 03:23 pm
I can imagine you falling off your chair in September when seeing 42 Raptor engines in the 9 meter BFR. :)
I said I'm not 100% sure there's 42 engines, its somewhere between 20 and 43 I think.
And it all depends on the optimal size of the engine.

How much engines do you think are there in the 9 meter BFR?

My guess: 22 or 19 makes the most sense, if they stick with trilateral symmetry. So in the 22-19 range.
Title: Re: ITS Development Updates and Discussion Thread
Post by: Peter.Colin on 07/27/2017 04:38 pm
Here's something interesting Gwynne Shotwell recently said about optimal Raptor engine size:

http://www.thespaceshow.com/show/22-jun-2017/broadcast-2934-ms.-gwynne-shotwell

(At 40:50)

They won't be so big as presented in September 2016.
But around twice as big as the demo engine.

Hearing this, I maybe rethinking my 42 engine count more towards in the middle between 21 and 42....
Altough 42 is still possible.

Title: Re: ITS Development Updates and Discussion Thread
Post by: Lars-J on 07/27/2017 04:52 pm
Here's something interesting Gwynne Shotwell recently said about optimal Raptor engine size:

http://www.thespaceshow.com/show/22-jun-2017/broadcast-2934-ms.-gwynne-shotwell

(At 40:50)

They won't be so big as presented in September 2016

You must have heard her differently than I did - at ~41:30-42:00 she expects the Raptor engine to be between 2 - 3 times as powerful  as the one they are testing. (the subscale one that has 100ton thrust) And if it is 3x as much, that matches the September 2016 presentation. "It will be bigger than the one we are firing now"
Title: Re: ITS Development Updates and Discussion Thread
Post by: Peter.Colin on 07/27/2017 05:00 pm
She seems more confident about 2 times than 3 times as powerful

If the mini ITS scales exactly it would be 2/3 of the original number of engines.
Title: Re: ITS Development Updates and Discussion Thread
Post by: spacenut on 07/27/2017 07:57 pm
The engines may not scale the same as the diameter of the rocket.  If the prototype engine is >2 meters and if the large Raptor is around 3m in diameter, you can only fit so many in a 9m diameter.  The 12m original ITS is 355 sq. meters, the 9m proposed version is 202 sq. meters in area.  That is why most think there will not be a lot of engines, probably between 19 and 21. 
Title: Re: ITS Development Updates and Discussion Thread
Post by: KelvinZero on 07/27/2017 11:47 pm
I kind of suspect something less than Falcon Heavy's 27 engines. Musk already mentioned how much anxiety Falcon Heavy's 27 engines gives him, I kind of suspect that will mean the initial BFR will have fewer engines.
I don't have much to contribute. My only interest really is how small this can start, given 9m.

I would love to see this at least as small as the FH. Stubby. Suboptimal but lots of margins. Lots of room to grow by stretching and adding more engines. Im guessing that would mean a lot less engines than FH to start with.

For BEO, this thing is just enormous. You can't compare it to Apollo. The part of that that actually landed on another world was it's 4th stage. the bit that returned to orbit was its 5th stage. Any BEO mission with this 9m monster is probably landing something the size of it's 2nd stage.
Title: Re: ITS Development Updates and Discussion Thread
Post by: oldAtlas_Eguy on 07/28/2017 04:44 am
Even though the ITSy possible 9m size would have only at best 100mt of cargo/payload capability, it has one major advantage over that of SLS or any other vehicle of similar size including Apollo and that is that the "US" spacecraft is capable of refueling such that the 100mt can then be pushed out to BEO and even all the way to and landing on Mars. Its this large size married to on-orbit refueling that extends this system so significantly. ULA has known this fact but has never been able to entice the funding to do it until recently with advent of the Vulcan ACES as a competitive maneuver against the F9/FH picing. But with two such vehicles with this "distributed launch" on-orbit refueling becomes operational then others not providing on-orbit refueling of their US will be left behind when it comes to BEO.

The other item is that keeping the timeline basically the same as that of the full size ITS presented last year the reduction in size could represent only having to fund at 60% level per year as that of the full 12m size ITS. That could be very significant in order to move forward such that instead of trying to fund as an example $1B /yr SpaceX needs only $600M/yr. The question becomes just how much or how little in funding is needed for the ITSy 9m per year. If the initail funding for the first 3 years is <$300M/yr with this smaller scale vehicle then SpaceX's ability to fund the work ihas little restrictions in that profits from operations/yr garnered in 2017 and 2018 at 20 to 25 flight rates of $250 to $300M could fund this project completely. With some matching investment funds, another $300M would allow the simultaneous development and deployment of the LEO constellation project. In other words instead of the $10B to accomplish the goals and timeline the smaller vehicle would need just $6B over the same period to accomplish the same goals but at a 50% scale.

I recognize that the estimates of costs for the development of the 9m relative to the 12m is based solely on the estimate of the difference in surface area of the two vehicles where as the payload is related to the volume. But also to note that costs of manufacturing equipment is nonlinear in relationship to the vehicle diameter. Such that the costs could be less than 60% that of the full size.

But the other item is that because of fixed costs on a launch regardless of size the $/kg price of the 9m will be ~2X that of 12m. This doubles the operational costs and double costs for the same level of colonization effort when using this 9m vehicle vs the 12m one.
Title: Re: ITS Development Updates and Discussion Thread
Post by: redliox on 07/28/2017 05:58 am
If the initail funding for the first 3 years is <$300M/yr with this smaller scale vehicle then SpaceX's ability to fund the work ihas little restrictions in that profits from operations/yr garnered in 2017 and 2018 at 20 to 25 flight rates of $250 to $300M could fund this project completely. With some matching investment funds, another $300M would allow the simultaneous development and deployment of the LEO constellation project. In other words instead of the $10B to accomplish the goals and timeline the smaller vehicle would need just $6B over the same period to accomplish the same goals but at a 50% scale.

I recognize that the estimates of costs for the development of the 9m relative to the 12m is based solely on the estimate of the difference in surface area of the two vehicles where as the payload is related to the volume. But also to note that costs of manufacturing equipment is nonlinear in relationship to the vehicle diameter. Such that the costs could be less than 60% that of the full size.

But the other item is that because of fixed costs on a launch regardless of size the $/kg price of the 9m will be ~2X that of 12m. This doubles the operational costs and double costs for the same level of colonization effort when using this 9m vehicle vs the 12m one.

I remember being warned how new vehicles, even if modeled after old ones (STS v.s. SLS i.e.) still will be expensive.  I'm assuming the 9m mini-ITS is going to be more of a test article/prototype rather than full-on working vehicle; building a small one with limited abilities will be cheaper but to an extent.  The 12m (assuming it will indeed be built) will require its own tests and another set of expenses; granted though if the 9 and 12 meter models are similar it should help.  It would definitely be as much an exercise in management as engineering.
Title: Re: ITS Development Updates and Discussion Thread
Post by: TomH on 07/28/2017 06:37 am
You can't compare it to Apollo. The part of that that actually landed on another world was it's 4th stage. the bit that returned to orbit was its 5th stage.

I would say SM was 4th and 7th stages. Descent stage of LM 5th, ascent stage LM 6th.

Any BEO mission with this 9m monster is probably landing something the size of it's 2nd stage.

But this would not be possible without multiple additional tanker launches to re-prop that stage, so it's an apples to oranges comparison.
Title: Re: ITS Development Updates and Discussion Thread
Post by: TomH on 07/28/2017 06:47 am
I'm assuming the 9m mini-ITS is going to be more of a test article/prototype rather than full-on working vehicle; building a small one with limited abilities will be cheaper but to an extent.  The 12m (assuming it will indeed be built) will require its own tests and another set of expenses; granted though if the 9 and 12 meter models are similar it should help.  It would definitely be as much an exercise in management as engineering.

Assuming everything plays out this way, once the full sized ship is flying, perhaps the still usable ITSy hardware can be used in some type of lunar exploration. Maybe SX sells or leases it to NASA, a tour company, or such.
Title: Re: ITS Development Updates and Discussion Thread
Post by: KelvinZero on 07/28/2017 08:25 am
But this would not be possible without multiple additional tanker launches to re-prop that stage, so it's an apples to oranges comparison.
A tiny apple to a really big orange comparison  8)

There are two things you can compare side by side:
(1) The size of your lander (ITSy US compared to Luna Module)
(2) The kg/cost of getting it to it's destination.

The number of flights is the thing that is really apples to oranges. What you would really want to compare is complexity or just cost/kg, which is very poorly related to number of flights due to all the differences between a Saturn 5 launching moon missions and a two stage unmanned reusable tanker flight.
Title: Re: ITS Development Updates and Discussion Thread
Post by: philw1776 on 07/28/2017 05:00 pm
I'm guessing 30 engines - e.g. Soviet N-1 :)  But I think with eminently more reliability. People round here 'dummy up' these notional configurations all the time with their fancy software. Can someone do a provisional 'drawing' of the 9 meter end-on view, using the known dimensions of the Merlin 1D as a rule of thumb to get an approximate number of engines? What's the nozzle diameter of the latest Merlins; about 1 meter? Darned if I know...

EDIT: Just did a good old-fashioned pen and paper scale drawing - the circle is 90mm (9cm) or 1/100 scale. The size of a sub scale Raptor is not fully known, but we could say roughly the same as the Merlin 1D nozzle diameter which googling tells me is about 1 meter. In 1/100th scale that would be a 'AAA' scale battery diameter of 10mm. I hedged my bets and used a 'AA' sized battery which is 14mm in diameter. The drawing and placement of the 'nozzle circles is a bit crude and imperfect; but I get 22x engines. That is if the subscale Raptor or Merlin 1D is used on the 9 meter booster.

It could be that because of the inaccuracies in my guesses - it may very well be that actually between 22 and 30 engines could fit there. I doubt 30, though - there needs to be clearance for nozzle swivelling etc, so 22x or very close to that may be the limit. The subscale Raptor apparently puts out about 225,000 pounds thrust (1 meganewton) and 22x of those is slightly less than 5 million pounds at sea level (22 meganewtons). If they use full scale Raptors in this 9 meter stage I'm not sure if they'd get more than about 9 engines on there - assuming they're more than twice the diameter of Merlin 1Ds. This implies a liftoff thrust of about 6.3 million pounds or 28 meganewtons. If I'm wrong about the diameter and fit of the Raptors and up to 16x fit on there - then thats about 11 million pounds of thrust, which sounds about right.

I don't think your assumption of ~2m diameter is valid.  The September 2016 ITS SL Raptor was ~1.6m max.
I can see a 12:6:1  19 engine ITSy at something like 12 million LBS thrust and maybe up to 21 engines.

The Rvac was specified as 3.8m.  I expect smaller Rvac expansion to fit the 9m upper stage. Stage 2 is where a subscale Raptor makes most sense.

As always, I say the initial booster flights will be with far fewer early prototype Raptors with rapid, repeated engine design upgrades and additions as the vehicle(s) work up to design goal payload orbital boosters.
Title: Re: ITS Development Updates and Discussion Thread
Post by: Norm38 on 07/29/2017 09:17 pm
Does the 12m necessarily replace the 9m?  They might complement each other, like a 737 and 747. There'd be a lot of systems comonality.  Maybe the 9m is the right size for LEO commercial stations, tourism, etc while the 12m is for BEO?
Title: Re: ITS Development Updates and Discussion Thread
Post by: redliox on 07/29/2017 09:41 pm
Does the 12m necessarily replace the 9m?  They might complement each other, like a 737 and 747. There'd be a lot of systems comonality.  Maybe the 9m is the right size for LEO commercial stations, tourism, etc while the 12m is for BEO?

Hard to say.  It isn't exactly often you see spacecraft upgrade in like fashion.  A 9 meter mini-ITS would be 75% the dimensions of the intended 12 meter and, assuming scaling, a bit over 40% the mass.  The biggest difference will likely be in engine configuration and after that modeling reentry and landings.  Not impossible but SpaceX would have to do some double-checking if it intended to go from 9 to 12.
Title: Re: ITS Development Updates and Discussion Thread
Post by: AncientU on 07/29/2017 10:23 pm
Does the 12m necessarily replace the 9m?  They might complement each other, like a 737 and 747. There'd be a lot of systems comonality.  Maybe the 9m is the right size for LEO commercial stations, tourism, etc while the 12m is for BEO?

I suspect that the 9m will develop a manifest in the Cis-Lunar space -- LEO to the Lunar vicinity -- as well as starting the Mars infrastructure build-up.  (At least SpaceX seems to think so...)  As such, the 12m could replace the Mars part of the launch load, while the smaller version continues services to Cis-Lunar.

A discriminator would be if the 12m was to use upgraded LC-39A/B instead of new launch sites -- new seems most likely to me.  That would allow 9m to keep flying while 12m ramped up, making their parallel operations more likely.
Title: Re: ITS Development Updates and Discussion Thread
Post by: KelvinZero on 07/29/2017 10:50 pm
IMO it is all about how business takes off. Imagine a future where ITSy is launching regularly and furthermore the factories to build more are running over time, and Elon Musk is regretfully saying he wished he had aimed a little bigger. A different world from today.

A lot of people paint Elon as like Noah, building a massive boat in a desert: a huge leap of faith. I think it all revolves around reusables changing how business works on earth, very little ITS development will not be around being profitable, and by the time he makes a real investment that has no earthly use there will be a fleet of these things and competitors with similar technology and it won't seem like such a big leap at all.
Title: Re: ITS Development Updates and Discussion Thread
Post by: Robotbeat on 07/29/2017 11:43 pm
Does the 12m necessarily replace the 9m?  They might complement each other, like a 737 and 747. There'd be a lot of systems comonality.  Maybe the 9m is the right size for LEO commercial stations, tourism, etc while the 12m is for BEO?
Musk consistently talks about yet larger ITSes. I fully expect a vehicle even larger than last year's ITS to be at least hinted at.

So I think 9m may actually replace the 12m version. With the next step being, say 15m.
Title: Re: ITS Development Updates and Discussion Thread
Post by: spacenut on 07/29/2017 11:58 pm
Yes, if 9m pans out, works as a flags and footprints Mars craft, cis-lunar, and multiple satellite launcher, a bigger one may end up being necessary.  So if a new factory and a new launch site are needed, why stop at 12m, go as big as possible. 

I foresee, if they get this 9m version going, NASA may hitch rides and help fund a Mars or Lunar base, thus SpaceX will make some more money with this 9m version.  It may very well be the SLS killer. 
Title: Re: ITS Development Updates and Discussion Thread
Post by: Peter.Colin on 07/30/2017 07:09 am
Does the 12m necessarily replace the 9m?  They might complement each other, like a 737 and 747. There'd be a lot of systems comonality.  Maybe the 9m is the right size for LEO commercial stations, tourism, etc while the 12m is for BEO?
Musk consistently talks about yet larger ITSes. I fully expect a vehicle even larger than last year's ITS to be at least hinted at.

So I think 9m may actually replace the 12m version. With the next step being, say 15m.

I also expect a 15 meter version, but it might be a too big step going from 9 meter.
If the 9 meter version has exactly 42 scalled engines, I expect the 12 meter version to have around 100 engines.

The 15 meter version could have also have 100 larger engines or even more engines.
In the computer age, a large number of relatively smaller engines seems easier to scale up to bigger rockets than scaling up the engines themselves, because of the non-scaling material properties of the engine.
Title: Re: ITS Development Updates and Discussion Thread
Post by: TomH on 07/30/2017 07:39 am
In the computer age, a large number of relatively smaller engines seems easier to scale up to bigger rockets than scaling up the engines themselves, because of the non-scaling material properties of the engine.

I wonder if they might do what they did with Merlin: incremental increases in chamber pressure and thrust with only tweaks to the engine itself. Possibly they might do that and simply increase the nozzle size. I have to wonder whether they may be starting with lower pressure than they think is ultimately possible so they can titrate up carefully over time as the engine develops a track record.
Title: Re: ITS Development Updates and Discussion Thread
Post by: AncientU on 07/30/2017 11:13 am
Yes, if 9m pans out, works as a flags and footprints Mars craft, cis-lunar, and multiple satellite launcher, a bigger one may end up being necessary.  So if a new factory and a new launch site are needed, why stop at 12m, go as big as possible. 

I foresee, if they get this 9m version going, NASA may hitch rides and help fund a Mars or Lunar base, thus SpaceX will make some more money with this 9m version.  It may very well be the SLS killer.

This and the string of 9m vs 12m vs 15m comments miss the point.  This vehicle will be reusable/refuelable!

Only building the orbital refueling capability (and existing, conventionally-sized rockets to use it) could get us beyond LEO very nicely.  Building a NOVA-sized, REUSABLE rocket provides 1-2 orders of magnitude greater capability than the SLS/Orion project -- if allowed to proceed to its logical end point -- will have by 2040.
Title: Re: ITS Development Updates and Discussion Thread
Post by: spacenut on 07/30/2017 12:16 pm
Didn't Merlin start out at about 80k lbs thrust, then incremental upgrades and pressure increases got it to the current 190k lbs thrust.  They have ran tests to 240k lbs thrust.  So, if the sub-scale Raptor started at 225k lbs thrust.  Hmmm, that means it may be able to more than double soon.   Building the whole engine slightly larger, definately makes it up to the proposed 685k thrust engine.  Hope they have the facilities to max out the pressure, even exploding some, to find out what it can do reliably.   
Title: Re: ITS Development Updates and Discussion Thread
Post by: Lar on 07/30/2017 03:20 pm
Yes, if 9m pans out, works as a flags and footprints Mars craft, cis-lunar, and multiple satellite launcher, a bigger one may end up being necessary.  So if a new factory and a new launch site are needed, why stop at 12m, go as big as possible. 

I foresee, if they get this 9m version going, NASA may hitch rides and help fund a Mars or Lunar base, thus SpaceX will make some more money with this 9m version.  It may very well be the SLS killer. 

9m enables a lot more on Mars than flags and footprints. But 12 or 15m would really scale things up a lot.
Title: Re: ITS Development Updates and Discussion Thread
Post by: philw1776 on 07/30/2017 04:11 pm
A 9m ITS style craft could transport robust ISRU prototype tech plus its needed power systems, presumably solar, to Mars for validation of concept and suggestions for iterative design improvement well before a base or a colony begins.  Even more so, it could enable better orbital and ground truth validation of potential base, then colony site alternatives.  9m or whatever its diameter, etc. ITSy is far more suited for this task than Red Dragon could have become.

Given that the proposed internet constellation deployment justifies ITSy development it is a win to go direct to ITSy re-purposing the couple hundred million $ of SpaceX internal funds that development and launch of a couple RD missions would have cost just assuming 2 in 2020.
Title: Re: ITS Development Updates and Discussion Thread
Post by: Nomadd on 07/30/2017 06:16 pm

2.6 times, not 3 times, and the original merlin 1A was engine made and developed very cheaply, just to get _something_ running for the falcon 1, and the original merlin 1A used a very low chamber pressure. When you start from very low, there is lots of space to go higher.

Most rocket engines have gained something like only 10-15% thrust increases during their >20 year lifespans.

It's hard to really say the exact ratio. You're comparing what the newest model is capable of to what the original was used at. Unless you know the maximum the original was tested at, it's fuzzy.
Title: Re: ITS Development Updates and Discussion Thread
Post by: DJPledger on 07/30/2017 07:19 pm
Does the 12m necessarily replace the 9m?  They might complement each other, like a 737 and 747. There'd be a lot of systems comonality.  Maybe the 9m is the right size for LEO commercial stations, tourism, etc while the 12m is for BEO?
Musk consistently talks about yet larger ITSes. I fully expect a vehicle even larger than last year's ITS to be at least hinted at.

So I think 9m may actually replace the 12m version. With the next step being, say 15m.

I also expect a 15 meter version, but it might be a too big step going from 9 meter.
If the 9 meter version has exactly 42 scalled engines, I expect the 12 meter version to have around 100 engines.

The 15 meter version could have also have 100 larger engines or even more engines.
In the computer age, a large number of relatively smaller engines seems easier to scale up to bigger rockets than scaling up the engines themselves, because of the non-scaling material properties of the engine.

Any no. of engines above around 20 is too many and even around that is still rather dicey. For 12m or 15m dia. ITS system booster expect a larger version of Raptor to be dev. too keep engine no. to the same as 9m ITS system booster. SpaceX will likely have plenty of money from their sat. constellation for dev. a larger version of Raptor by the time they start bending metal on a larger ITS system. Once 9m ITS system design is frozen why change it when dev. a larger version? Just scale everything up keeping the same overall design when going from 9m to 12m or 15m. 9m ITS system booster should have no more than 21 engines which is still pushing it IMO.

The optimum no. of engines on a booster is 7-9. More than that increases the risk of a catastrophic engine failure destroying the LV.

EM needs to learn the lesson from the N-1 and not to go overboard with the engine no. on 9m ITS and future larger ITS systems. If EM had at least another $10 billion to play with I am sure he would have decided to dev. a much larger booster engine to keep engine no. on ITS booster to the optimum value. This was the original plan with 9 F-1 class Raptors before EM scaled Raptor down. This was likely because EM could not afford to dev. an F-1 class Raptor.
Title: Re: ITS Development Updates and Discussion Thread
Post by: hkultala on 07/30/2017 08:06 pm
The optimum no. of engines on a booster is 7-9. More than that increases the risk of a catastrophic engine failure destroying the LV.

No, if there is such armour between engines than turbopump failure does not break the adjacent engines.

Quote
EM needs to learn the lesson from the N-1 and not to go overboard with the engine no. on 9m ITS and future larger ITS systems.

He has learned all the lessons from N-1.

BFR/ITS does not use differential throttle steering like N-1 used, it uses gimbaling engines.

And spaceX does static fire testing. Static fire testing would have caught some of the N-1 problems

Quote
If EM had at least another $10 billion to play with I am sure he would have decided to dev. a much larger booster engine to keep engine no. on ITS booster to the optimum value. This was the original plan with 9 F-1 class Raptors before EM scaled Raptor down. This was likely because EM could not afford to dev. an F-1 class Raptor.

Wrong.

Raptor was scaled down to
1) have better performance (better T/W ratio), and
2) to allow same engines to be used in both BFR and ITS.

Title: Re: ITS Development Updates and Discussion Thread
Post by: DJPledger on 07/30/2017 08:21 pm
Wrong.

Raptor was scaled down to
1) have better performance (better T/W ratio), and
2) to allow same engines to be used in both BFR and ITS.
All a booster engine has to do is to push the booster and the ship/US out of the Earth's atm. Does not need the absolute every last scrap of TWR and ISP to do the job. Just make the booster slightly larger to compensate. It's your US that needs the best possible ISP and TWR from your engines. Dev. optimum TWR and ISP engines for the ITS ship and high thrust engines for ITS booster so it has no more than 9.

SpaceX's announced ITS system design only uses the same engine throughout due to funding limitations. High thrust engines are optimal for boosters while smaller high ISP engines are optimal for upper stages.
Title: Re: ITS Development Updates and Discussion Thread
Post by: M.E.T. on 07/30/2017 09:33 pm
A 9m ITS style craft could transport robust ISRU prototype tech plus its needed power systems, presumably solar, to Mars for validation of concept and suggestions for iterative design improvement well before a base or a colony begins.  Even more so, it could enable better orbital and ground truth validation of potential base, then colony site alternatives.  9m or whatever its diameter, etc. ITSy is far more suited for this task than Red Dragon could have become.

Given that the proposed internet constellation deployment justifies ITSy development it is a win to go direct to ITSy re-purposing the couple hundred million $ of SpaceX internal funds that development and launch of a couple RD missions would have cost just assuming 2 in 2020.

This is a good point. SpaceX's cost for Red Dragon was stated to be around $300m. If they ended up sending two or more, that took it up to $600m. Money that can get them well on their way to developing ITSy instead.
Title: Re: ITS Development Updates and Discussion Thread
Post by: spacenut on 07/30/2017 09:35 pm
12 million lbs thrust is the maximum the flame trenches at Pads 39A and 39B can handle.  12 million / 685,000 lbs the maximum of the full scale Raptor is 17.5 engines.  Keeping it under maximum pressure slightly, I predict 19 engines.  6 around a center engine with 12 on the outside ring = 19. As someone said, the nozzle diameter will probably be 1.6m so they would fit.  The original 12m version was the maximum diameter for most barge, river, and the cape infrastructure could handle.  12m was to be the NOVA class rocket that was larger than Saturn V and had 8 F-1 engines instead of 5. 

Unless a completely new location, pad, etc is built I don't think a 15m ITS would be built within the next 40 years.  It will likely be a 12m in about 20 years. 
Title: Re: ITS Development Updates and Discussion Thread
Post by: Robotbeat on 07/30/2017 09:48 pm
*handle without major modification.
Title: Re: ITS Development Updates and Discussion Thread
Post by: docmordrid on 07/31/2017 01:48 am
12 million lbs thrust is the maximum the flame trenches at Pads 39A and 39B can handle. 
>

IF they use the 39A dual launch mount concept Chris Bergin wrote about here,

https://www.nasaspaceflight.com/2017/07/installation-flame-deflector-sls-begins-39b/

Quote
Updated information has allowed for a preliminary envisioning process (via L2 Envisioning) with pad engineers and experts evaluating a second, larger, Horizontal Integration Facility (HIF) outside the pad perimeter, allowing the subscale BFR to roll to an additional mount along the same trench at 39A. An article on this 39A option will follow in the coming weeks.

...would the pressure and acoustic environments necessarily be the same? ISTM the ITSy mount, being so close to the open portion of the trench, would have a slightly higher thrust capacity.

Simplified version of the concept in Chris' article attached.
Title: Re: ITS Development Updates and Discussion Thread
Post by: tvg98 on 07/31/2017 02:25 am
Not sure whether I should put this here or on the old thread, but if this reddit comment is to be believed (https://www.reddit.com/r/spacex/comments/6kw70z/rspacex_discusses_july_2017_34/dkxtc8r/) (http://(https://www.reddit.com/r/spacex/comments/6kw70z/rspacex_discusses_july_2017_34/dkxtc8r/)), ITSy may be significantly smaller than what we are expecting.

Quote
One more thing: I just remembered that during my tour of SpaceX our guide told us about how they were getting ready to unveil a rocket the Falcon XX at the IAC in September. They said that the vehicle would be around 20ft in diameter and would be "substantially taller than the Falcon 9". I believe this is the sub-scale BFR that has been in the works lately although I have never heard it referred to with that particular name (which dates back to F9 1.0 days).
Title: Re: ITS Development Updates and Discussion Thread
Post by: Semmel on 07/31/2017 09:28 am
Does the 12m necessarily replace the 9m?  They might complement each other, like a 737 and 747. There'd be a lot of systems comonality.  Maybe the 9m is the right size for LEO commercial stations, tourism, etc while the 12m is for BEO?
Musk consistently talks about yet larger ITSes. I fully expect a vehicle even larger than last year's ITS to be at least hinted at.

So I think 9m may actually replace the 12m version. With the next step being, say 15m.

I think the same. The 12m version is ginormous in today’s standards. But I also think for the stated goal of colonizing Mars, the 12m ITS is too small. Why? Because the majority of the cost over the lifetime of the booster and ship will be operating it. i.e. ground support, on board crew, control centers, maintenance and simply coordinating the whole show once it starts flying. All this scales with the number of craft, not so much with the size of the individual ships. Also, the larger the cargo hold, the easier it will be to transport large machines which are needed for building the colony. A larger ship will save money on the colony side. And once a standard is established, it is hard to change it, see for instance tunnels for railways. Its always possible to do something special but the bulk part of the cost comes from the standard goods. And if these are cheaper, the colony wins. Development. R&D and launch cost for a 12m or 15m version are probably similar. 9m is cheaper because of existing facilities that can be used (factories, 39A and 39B). But once the booster goes beyond the thrust these facilities can handle, the bigger the cheaper.
Title: Re: ITS Development Updates and Discussion Thread
Post by: stcks on 07/31/2017 12:46 pm
Not sure whether I should put this here or on the old thread, but if this reddit comment is to be believed (https://www.reddit.com/r/spacex/comments/6kw70z/rspacex_discusses_july_2017_34/dkxtc8r/) (http://www.reddit.com/r/spacex/comments/6kw70z/rspacex_discusses_july_2017_34/dkxtc8r/), ITSy may be significantly smaller than what we are expecting.

Quote
One more thing: I just remembered that during my tour of SpaceX our guide told us about how they were getting ready to unveil a rocket the Falcon XX at the IAC in September. They said that the vehicle would be around 20ft in diameter and would be "substantially taller than the Falcon 9". I believe this is the sub-scale BFR that has been in the works lately although I have never heard it referred to with that particular name (which dates back to F9 1.0 days).

Thanks for posting that, it is very interesting. Keep in mind this is, of course, a rumor from only one person.

A 6 meter rocket is a much better fit for the current commercial and military launch market. It would very likely enable second stage reuse on all of the missions that we see launched today. However, a 6 meter rocket is a very poor fit for Musk's humans to Mars goals and also doesn't really feel like it matches Mueller's comments earlier this year.

Edit: fixed tvg98's link
Title: Re: ITS Development Updates and Discussion Thread
Post by: rsdavis9 on 07/31/2017 02:20 pm
Possibly instead of 9m to 15m.
By the time the jump is necessary we will see the change over to dedicated ships for earth to LEO, transit to mars, mars orbit to surface.
At some point the bigger craft don't get you anything. Just improving the reusability and flight frequency of the smaller existing craft will get you more bang for the buck.

The only exception is what people consider the largest THING that people consider transporting. This means it has to be something that is better left as whole instead of broken down into pieces.

So is a boring machine size and weight transportable to mars with ITSy?
Can it be broken down into pieces easily?


Title: Re: ITS Development Updates and Discussion Thread
Post by: guckyfan on 07/31/2017 02:21 pm
A 6m rocket should be able to launch on all existing launch sites. Making phasing out of the Falcon family possible without needing the launch capability for the 9m ITS which would be a major challenge in Vandenberg. 9m robably too large for Boca Chica.
Title: Re: ITS Development Updates and Discussion Thread
Post by: original_mds on 07/31/2017 02:34 pm
A 6 meter rocket is a much better fit for the current commercial and military launch market. It would very likely enable second stage reuse on all of the missions that we see launched today. However, a 6 meter rocket is a very poor fit for Musk's humans to Mars goals and also doesn't really feel like it matches Mueller's comments earlier this year
Was Mueller clearly talking about barrel diameter?  I.e was it possible the 9 m sources refer to max diameter with leg/fins or a potential flare for the nozzles and the 6 m source is the barrel diameter?  This would allow for a 1.5 m wider skirt, which could accomodate more engines.
Title: Re: ITS Development Updates and Discussion Thread
Post by: rsdavis9 on 07/31/2017 02:35 pm
A 6m rocket should be able to launch on all existing launch sites. Making phasing out of the Falcon family possible without needing the launch capability for the 9m ITS which would be a major challenge in Vandenberg. 9m robably too large for Boca Chica.

I thought they almost did a shuttle launch from vandenberg? Wouldn't that pad be big enough?
Title: Re: ITS Development Updates and Discussion Thread
Post by: guckyfan on 07/31/2017 02:43 pm
A 6m rocket should be able to launch on all existing launch sites. Making phasing out of the Falcon family possible without needing the launch capability for the 9m ITS which would be a major challenge in Vandenberg. 9m robably too large for Boca Chica.

I thought they almost did a shuttle launch from vandenberg? Wouldn't that pad be big enough?


ITS 9m could be up to NOVA class. Exceeding Saturn 5 and the Shuttle. The Florida pads were oversized because they thought they may need NOVA class rockets.
Title: Re: ITS Development Updates and Discussion Thread
Post by: JasonAW3 on 07/31/2017 03:02 pm
A 6m rocket should be able to launch on all existing launch sites. Making phasing out of the Falcon family possible without needing the launch capability for the 9m ITS which would be a major challenge in Vandenberg. 9m robably too large for Boca Chica.

I thought they almost did a shuttle launch from vandenberg? Wouldn't that pad be big enough?

As I understood it, there were design issues with that pad that made it impossible to be used to launch the Shuttle from.  I think that has been torn down since then, but I could be mistaken on that.
Title: Re: ITS Development Updates and Discussion Thread
Post by: spacenut on 07/31/2017 03:06 pm
Don't forget, liquid methane is less dense than kerosene.  So the volume of the rocket would have to take that into consideration.  a 6m or 7m rocket would have to be excessively long, almost like F9 which is maxed out on length.  Also, the larger the diameter and the longer the rocket, the harder it is to fit transportation infrastructure. 

For methane, the diameter is going to be as wide as possible.  You also must get the right amount of engines under the booster to be able to land.  A 6m rocket can only get about 7 Raptors on the booster and only one or two vacuum engines for second stage or ITS.  This would have less capability than Falcon Heavy.  Not realistic.  A 7m rocket wouldn't be much better, maybe match Blue Origins New Glenn.  Probably not going there.  8 would be better, but not much better than New Glenn and probably wouldn't match SLS.  So, at least 8.4, but more than likely 9m as EM said. 

9m would also allow building the mini-ITS or ITSy.  Get around 120-150 tons to LEO, allow for Mars trips, allow for cis-lunar, and get the Constellation satellites up.  Anything smaller is only competing with what is soon to be available. 
Title: Re: ITS Development Updates and Discussion Thread
Post by: Welsh Dragon on 07/31/2017 03:16 pm
A 6m rocket should be able to launch on all existing launch sites. Making phasing out of the Falcon family possible without needing the launch capability for the 9m ITS which would be a major challenge in Vandenberg. 9m robably too large for Boca Chica.

I thought they almost did a shuttle launch from vandenberg? Wouldn't that pad be big enough?

As I understood it, there were design issues with that pad that made it impossible to be used to launch the Shuttle from.  I think that has been torn down since then, but I could be mistaken on that.
SLC-6 is now used for Delta IV launches (for the time being).
Title: Re: ITS Development Updates and Discussion Thread
Post by: wannamoonbase on 07/31/2017 03:20 pm
Don't forget, liquid methane is less dense than kerosene.  So the volume of the rocket would have to take that into consideration.  a 6m or 7m rocket would have to be excessively long, almost like F9 which is maxed out on length.  Also, the larger the diameter and the longer the rocket, the harder it is to fit transportation infrastructure. 

For methane, the diameter is going to be as wide as possible....

Also, with sub-cooled fuel and oxidizer, the closer the tank shapes approach the ideal minimum heat transfer shape - spherical.

Once the diameter of the vehicle is too big to ship on the highway system then may as well go for ideal shape, short and fat.
Title: Re: ITS Development Updates and Discussion Thread
Post by: stcks on 07/31/2017 03:36 pm
A 6m rocket can only get about 7 Raptors on the booster and only one or two vacuum engines for second stage or ITS.  This would have less capability than Falcon Heavy.  Not realistic.

Just want to point out that a 6m diameter would fit 9 1.6m Raptors in the same octoweb configuration as F9. That configuration would likely be a bit more thrust than FH (possibly up to 27 MN depending on the thrust of the Raptor).
Title: Re: ITS Development Updates and Discussion Thread
Post by: gin455res on 07/31/2017 03:53 pm

For methane, the diameter is going to be as wide as possible.  You also must get the right amount of engines under the booster to be able to land.  A 6m rocket can only get about 7 Raptors on the booster and only one or two vacuum engines for second stage or ITS.




Might a 7 or 9 Raptor booster profitably loft a 3 merlin* ITSy?


* 2 dual-bell vacuum merlins,  either side of 1 sea-level merlin (for launch, and landing)
Title: Re: ITS Development Updates and Discussion Thread
Post by: envy887 on 07/31/2017 04:55 pm

For methane, the diameter is going to be as wide as possible.  You also must get the right amount of engines under the booster to be able to land.  A 6m rocket can only get about 7 Raptors on the booster and only one or two vacuum engines for second stage or ITS.




Might a 7 or 9 Raptor booster profitably loft a 3 merlin* ITSy?


* 2 dual-bell vacuum merlins,  either side of 1 sea-level merlin (for launch, and landing)

No. SpaceX isn't going to go to all the effort to build a Raptor booster just to put a Merlin upper stage on it.
Title: Re: ITS Development Updates and Discussion Thread
Post by: BretShooter on 07/31/2017 05:07 pm
At what altitude would the 12 Million Ft/lb trench limit be moot?  Until they had a facility that could handle the full initial thrust of the ITSy booster, couldn't they start at 75% (or what ever value made sense) and then ramp to full thrust as soon as they are a safe distance from the pad?  I know it wouldn't be ideal, but it certainly would allow launches without a dedicated pad initially.

Edited to add y to ITS
Title: Re: ITS Development Updates and Discussion Thread
Post by: spacenut on 07/31/2017 06:33 pm
12 million should be enough to do almost anything and not have to throttle up.  17-21 is going to max out the diameter anyway based on the proposed nozzle size.  So approaching 12 million is about all they can do with a 9m core. 

Later going to a 12m core could get another ring of engines to approach 42 engines that they were originally going to do, so it scales easily to double the future payload.  I don't see that until the 9m core gets real busy. 
Title: Re: ITS Development Updates and Discussion Thread
Post by: gin455res on 07/31/2017 10:50 pm

For methane, the diameter is going to be as wide as possible.  You also must get the right amount of engines under the booster to be able to land.  A 6m rocket can only get about 7 Raptors on the booster and only one or two vacuum engines for second stage or ITS.




Might a 7 or 9 Raptor booster profitably loft a 3 merlin* ITSy?


* 2 dual-bell vacuum merlins,  either side of 1 sea-level merlin (for launch, and landing)

No. SpaceX isn't going to go to all the effort to build a Raptor booster just to put a Merlin upper stage on it.


Will the market be there for anything larger?
Title: Re: ITS Development Updates and Discussion Thread
Post by: Robotbeat on 07/31/2017 10:56 pm

For methane, the diameter is going to be as wide as possible.  You also must get the right amount of engines under the booster to be able to land.  A 6m rocket can only get about 7 Raptors on the booster and only one or two vacuum engines for second stage or ITS.




Might a 7 or 9 Raptor booster profitably loft a 3 merlin* ITSy?


* 2 dual-bell vacuum merlins,  either side of 1 sea-level merlin (for launch, and landing)

No. SpaceX isn't going to go to all the effort to build a Raptor booster just to put a Merlin upper stage on it.


Will the market be there for anything larger?
Irrelevant. Methane is better for reuse and they'll want both stages to use the same fuel.
Title: Re: ITS Development Updates and Discussion Thread
Post by: gin455res on 07/31/2017 11:10 pm

For methane, the diameter is going to be as wide as possible.  You also must get the right amount of engines under the booster to be able to land.  A 6m rocket can only get about 7 Raptors on the booster and only one or two vacuum engines for second stage or ITS.




Might a 7 or 9 Raptor booster profitably loft a 3 merlin* ITSy?


* 2 dual-bell vacuum merlins,  either side of 1 sea-level merlin (for launch, and landing)

No. SpaceX isn't going to go to all the effort to build a Raptor booster just to put a Merlin upper stage on it.


Will the market be there for anything larger?
Irrelevant. Methane is better for reuse and they'll want both stages to use the same fuel.


How many falcon 9s have there been so far? Has the merlin reached its final version yet? No. Would a smaller vehicle fly more frequently and allow the tech to mature more quickly? What if the first 2-3 blow up, how much will that cost?
Can such a high pressure engine be contained so effectively if it explodes, and so can we assume more engines is more redundancy, or more chance of one malfunction ripping through the entire vehicle?
Title: Re: ITS Development Updates and Discussion Thread
Post by: Stan-1967 on 07/31/2017 11:51 pm
Can such a high pressure engine be contained so effectively if it explodes, and so can we assume more engines is more redundancy, or more chance of one malfunction ripping through the entire vehicle?

I too am doubting the assumption of engine out capability with Raptor powered vehicles.  With Falcon, it was always touted as a benefit of the Merlin.  On what basis is "engine out" capability for Raptor/ITS or smaller derivatives still touted without any evidence?

The argument for large numbers of engines has two dependent sides:
1.  Build a high number of smaller engines, and you can increase reliability by better statistical understanding of the failure modes and probabilities.
2.  The high T/W, yet moderate ( to low) chamber pressure of the Merlin engines, minimized the penalty of shielding/armoring each engine pod against a RUD.  ( See CRS-1 ) 


Raptor powered vehicles may well enjoy the benefits of point #1, as well as high T/W of #2, however low chamber pressure is not a feature of the Raptor.  If that engine RUD's, does anyone here think a weight efficient shielding of each engine pod within the thrust frame is possible?

Title: Re: ITS Development Updates and Discussion Thread
Post by: docmordrid on 08/01/2017 12:37 am
Can such a high pressure engine be contained so effectively if it explodes, and so can we assume more engines is more redundancy, or more chance of one malfunction ripping through the entire vehicle?

I too am doubting the assumption of engine out capability with Raptor powered vehicles. 
>
If that engine RUD's, does anyone here think a weight efficient shielding of each engine pod within the thrust frame is possible?

Perhaps it has conformal armor which balloons with pressure, but doesn't allow a pressure wave or bits to pass.

ISTM if the lower attachment of this "armor" were designed to fail first it would channel the escaping gases down, past the nozzle and out of the engine bay.
Title: Re: ITS Development Updates and Discussion Thread
Post by: envy887 on 08/01/2017 03:26 am

For methane, the diameter is going to be as wide as possible.  You also must get the right amount of engines under the booster to be able to land.  A 6m rocket can only get about 7 Raptors on the booster and only one or two vacuum engines for second stage or ITS.




Might a 7 or 9 Raptor booster profitably loft a 3 merlin* ITSy?


* 2 dual-bell vacuum merlins,  either side of 1 sea-level merlin (for launch, and landing)

No. SpaceX isn't going to go to all the effort to build a Raptor booster just to put a Merlin upper stage on it.


Will the market be there for anything larger?
Irrelevant. Methane is better for reuse and they'll want both stages to use the same fuel.


How many falcon 9s have there been so far? Has the merlin reached its final version yet? No. Would a smaller vehicle fly more frequently and allow the tech to mature more quickly? What if the first 2-3 blow up, how much will that cost?
Can such a high pressure engine be contained so effectively if it explodes, and so can we assume more engines is more redundancy, or more chance of one malfunction ripping through the entire vehicle?

None of this is a reason to put a Merlin US on a Raptor booster.

And yes, containment mass and engine thrust both scale roughly linearly with chamber pressure, so containing Raptor should be about the same as Merlin on a mass per unit thrust basis.
Title: Re: ITS Development Updates and Discussion Thread
Post by: Stan-1967 on 08/01/2017 03:37 am

ISTM if the lower attachment of this "armor" were designed to fail first it would channel the escaping gases down, past the nozzle and out of the engine bay.

Not necessarily if the gas expansion is supersonic/compressible flow.   
 
It will be interesting to see what SpaceX comes up with to manage this risk.
1.  Beefier armor vs. Falcon
2.  More engine testing & improved reliability negating the need for armor.
3.  Active systems? 
Title: Re: ITS Development Updates and Discussion Thread
Post by: Stan-1967 on 08/01/2017 04:47 am
And yes, containment mass and engine thrust both scale roughly linearly with chamber pressure, so containing Raptor should be about the same as Merlin on a mass per unit thrust basis.

I'm not so sure the failure modes operate in a linear manner between a GG cycle vs. FFSC. 

What is the proper way to compare the energy contained in the GG preburner flow plus both fuel/oxidizer sides to the energy in the FFSC where props are gassified and at higher pressure?  I ask because I do not know what is best.  What is best maybe depends on the likely failure modes?

It seems like the GG cycle has low upstream energetic liability, & all the energy is focused in the main combustion chamber.  Whereas FFSC distributes much more energy into the propellant before it enters the combustion chamber.  Basically the FFSC cascades any failure into the whole system, whereas GG can isolate upstream RUD's.

As an example, I look at CRS-1, all that was really stated regarding the cause was that a failure occurred and the engine was shut off.  For that to happen, it suggest the engine controllers & valves were still operational.  Speculatively, it was the GG that came apart in CRS-1.  Having RUD in the GG pre-burner =/= RUD in any section of a FFSC engine. 
Title: Re: ITS Development Updates and Discussion Thread
Post by: TomH on 08/01/2017 06:14 am
How many falcon 9s have there been so far? Has the merlin reached its final version yet? No.

Yes, it has.

Might a 7 or 9 Raptor booster profitably loft a 3 merlin* ITSy?

RP-1 is a very poor fuel for an upper stage due to its low ISP. The current upper stage on Falcon is its weak link and you can find endless threads here re. replacing it with a better US.

RP-1 is a good fuel for a first stage due to its high IPS Density.  Let's compare hydrogen to RP-1 (highly refined kerosene). Given an equal volume of RP-1 and hydrogen, the RP-1 has far more energy. But given equal mass of RP-1 and hydrogen, the hydrogen has far more energy. Hydrogen is really lightweight stuff. As a generalization, it takes a lot of it volume wise, but not much of it weight wise. First stages require so much raw energy that the use of RP-1 allows the first stage to be not so enormous in size. Volume is what matters in an S1. With an upper stage, mass is what matters; you want the greatest amount of energy possible for a given mass. Saturn V had a good balance with RP-1 fueled S1 and hydrogen fueled upper stages. RP-1 is a poor fuel for upper stages. Hydrogen is a good fuel for upper stages.

RP-1 is not a good fuel for reusable engines due to coking which is caused by the large hydrocarbon molecules. Hydrogen burned with with oxygen produces nothing more than steam (water) and does not coke.

Methane has an ISP between RP-1 and hydrogen as well as an ISP Density between RP-1 and hydrogen. It is a good compromise fuel. Methane also is a light hydrocarbon and does not coke; this makes it good for reusable engines. The magical thing about methane, however, is that it can be produced using In Situ Resource Utilization (ISRU). In other words, you can make the stuff on Mars. You don't have to haul your return fuel to Mars, you can make it there and use the same engines that brought you there.

Musk wants to get to all methane eventually. Once he has developed working methane engines, he is not going to use RP-1 on an upper stage. There was much speculation that SX would first develop a reusable methane upper stage for Falcon while still launching it on the RP-1 S1. But that was not worth the R&D in the long term.

One thing that absolutely will not ever happen is developing a methane booster then putting an RP-1 powered upper stage on top of it. It would be an absolutely ridiculous thing to do because once you have working methane engines, it would tremendously limit the rocket's overall performance to then put the kerosene engines on the US, rather than using the now extant methane engines up there instead. You will NEVER see a methane first stage with a kerosene upper stage. That would be like using a golf cart to tow a pickup to the golf course, then using the pickup to drive around the golf course.
Title: Re: ITS Development Updates and Discussion Thread
Post by: gin455res on 08/01/2017 02:21 pm
Do Block 4 and 5 leave the merlin unchanged?


If the iteration period is shortened (with higher flight rates), can a smaller vehicle be fielded and matured faster?


I get all the stuff about isp, coking, density, but I'm wondering if programmatically there is an opportunity cost of taking bigger slower steps. And, also added risks. 


What about lost revenue derived from more capable in-space hardware (like constellations, space stations, ..) that would be enabled by an earlier, but less dramatic, reduction in cost/lb to orbit that intermediate steps might offer.
Title: Re: ITS Development Updates and Discussion Thread
Post by: GORDAP on 08/01/2017 02:37 pm
Do Block 4 and 5 leave the merlin unchanged?


If the iteration period is shortened (with higher flight rates), can a smaller vehicle be fielded and matured faster?


I get all the stuff about isp, coking, density, but I'm wondering if programmatically there is an opportunity cost of taking bigger slower steps. And, also added risks. 


What about lost revenue derived from more capable in-space hardware (like constellations, space stations, ..) that would be enabled by an earlier, but less dramatic, reduction in cost/lb to orbit that intermediate steps might offer.

Yes, there might be a rationale for taking a 'halfway' step to increased performance while not impacting operations and infrastructure very much, but the only one that makes sense is the opposite of what you've proposed.  That is, a new Raptor based ITS-like upper stage atop a Falcon Heavy.   This at least puts the ISP/Density fuel tradeoff in the right stages.  But I no longer think this is anywhere in their plans.  I expect an 8+ meter 'ITSy' full bore.  A Merlin based upper stage atop an ITSy booster is a non-starter, for all the reasons above.
Title: Re: ITS Development Updates and Discussion Thread
Post by: spacenut on 08/01/2017 03:09 pm
Why 8m if the booster is going to be 9m?  9m would be the core barrel for ITSy.  Then add return shielding, legs, etc to the core.  Same width barrels, same tooling. 
Title: Re: ITS Development Updates and Discussion Thread
Post by: speedevil on 08/01/2017 03:28 pm
The optimum no. of engines on a booster is 7-9. More than that increases the risk of a catastrophic engine failure destroying the LV.

If you can mitigate failures such that the worst possible failure is contained to one engine, and design your craft appropriately, it is in principle possible to run your engines at a thrust where they risk failure in use, but complete the mission entirely nominally.

More engines make this easier.
This does depend on well understood engines, but can open up some interesting trades in the maintenance/reliability design space.
Title: Re: ITS Development Updates and Discussion Thread
Post by: GORDAP on 08/01/2017 03:32 pm
I say "8+" for both booster and upper stage (I think they'll be the same)  as I don't think Elon committed to exactly 9, just said the present factory could accommodate up to 9.  It would be unsurprising to me if the ITSy design settled on, say, 8.4 or 8.7 meters for other logistical reasons we don't currently have insight into. 
Title: Re: ITS Development Updates and Discussion Thread
Post by: wannamoonbase on 08/01/2017 03:39 pm
...If the iteration period is shortened (with higher flight rates), can a smaller vehicle be fielded and matured faster?


I don't think SpaceX will need to iterate as much as they have in the past.  They have way more experience and existing technologies (i.e. Vertical landing and reuse tech on the Block 5).

A new Raptor powered vehicle will have a new air-frame, which is an understood science and the Raptor engine which they have time to develop and test extensively.  Since they have all their Merlin experience and are starting with sub-cooled propellants the first Raptor will be much closer to the final version than Merlin.

It would be fun to see them work on US recovery with the F9/FH family.  But resource wise it's likely more efficient to move onto the next vehicles.

Get the Block 5's flying and ramp up second stage production.  Fly the manifest, book revenue and gain re-use experience. 
Title: Re: ITS Development Updates and Discussion Thread
Post by: gin455res on 08/01/2017 03:42 pm
Do Block 4 and 5 leave the merlin unchanged?


If the iteration period is shortened (with higher flight rates), can a smaller vehicle be fielded and matured faster?


I get all the stuff about isp, coking, density, but I'm wondering if programmatically there is an opportunity cost of taking bigger slower steps. And, also added risks. 


What about lost revenue derived from more capable in-space hardware (like constellations, space stations, ..) that would be enabled by an earlier, but less dramatic, reduction in cost/lb to orbit that intermediate steps might offer.

Yes, there might be a rationale for taking a 'halfway' step to increased performance while not impacting operations and infrastructure very much, but the only one that makes sense is the opposite of what you've proposed.  That is, a new Raptor based ITS-like upper stage atop a Falcon Heavy.   This at least puts the ISP/Density fuel tradeoff in the right stages.  But I no longer think this is anywhere in their plans.  I expect an 8+ meter 'ITSy' full bore.  A Merlin based upper stage atop an ITSy booster is a non-starter, for all the reasons above.



Falcon Heavy hasn't flown yet and is much more complicated.

How would this upper-stage land with only one vacuum optimised engine?


If system performance is a function of payload AND no. of reuses; might it be better to make the booster more reusable with Raptors?  It is 70% of the cost of an F9. A single stick Raptor-7 or Raptor-9 booster that requires reduced maintenance and can be reused 100 times could be a money saver.



And if constellations are the primary payload, does their lower orbit counter-act some of the advantage that is gained from methane's improved vacuum isp?


Sea-Level -> Vacuum ISP (from Wikipedia)
Raptor: 334 -> 361
Merlin:  282 -> 311
18%-> 16% difference


Vacuum
Raptor: 382
Merlin: 348
10% difference - improved mass fraction for merlin
Title: Re: ITS Development Updates and Discussion Thread
Post by: rakaydos on 08/01/2017 04:15 pm
Do Block 4 and 5 leave the merlin unchanged?


If the iteration period is shortened (with higher flight rates), can a smaller vehicle be fielded and matured faster?


I get all the stuff about isp, coking, density, but I'm wondering if programmatically there is an opportunity cost of taking bigger slower steps. And, also added risks. 


What about lost revenue derived from more capable in-space hardware (like constellations, space stations, ..) that would be enabled by an earlier, but less dramatic, reduction in cost/lb to orbit that intermediate steps might offer.

Yes, there might be a rationale for taking a 'halfway' step to increased performance while not impacting operations and infrastructure very much, but the only one that makes sense is the opposite of what you've proposed.  That is, a new Raptor based ITS-like upper stage atop a Falcon Heavy.   This at least puts the ISP/Density fuel tradeoff in the right stages.  But I no longer think this is anywhere in their plans.  I expect an 8+ meter 'ITSy' full bore.  A Merlin based upper stage atop an ITSy booster is a non-starter, for all the reasons above.



Falcon Heavy hasn't flown yet and is much more complicated.

How would this upper-stage land with only one vacuum optimised engine?
Falcon heavy is complicated because it's trying to be a "Lego Rocket"- Saving costs by reusing an already functional component in a different context. It's complicated because they cant solve problems with falcon heavy by making changes to the heavy boosters, because those heavy boosters must remain Falcon 9 cores. So there's a lot of issues in the 3 core problem that they cannot fix "correctly", and have to cobble together a solution to a problem with the booster by modifying the core.

As for the upper stage, you need to cut into your payload capacity, and glue a modified Dragon 2 to it's nose. Heat shield, landing legs, propulsive landing, hypergolic fuel for GTO orbit stability, independant long-duration electronics, all of which move the CG foreward so it's stable nose first, AND all of which is an optional, though common, module than can be left off an any mission that needs disposable performance.
Title: Re: ITS Development Updates and Discussion Thread
Post by: spacenut on 08/01/2017 04:37 pm
The problems with FH gives a reusable metholox upper stage more reason to develop as a way forward to ITSy. 

landing a second stage could be just the addition of the Super Dracos, enough hypergolic fuel, and landing legs.  The increased capability of a the sub-scale Raptor might keep payloads the same, and with an expendable upper stage based Raptor and expendable first stage, may make FH unnecessary.  Someone figured about 28 tons to LEO with this.  GEO would be reachable with a 8+ ton satellite in expendable mode.   Again no need for FH. 

They are going to have to put liquid methane facility in place before the ITS or ITSY can fly anyway.  This could be used to load fuel for a methane upper stage designed like a mini-ITSy.  At least to test components before the full blown ITS or the 9m ITSy is built.   
Title: Re: ITS Development Updates and Discussion Thread
Post by: envy887 on 08/01/2017 05:26 pm
Do Block 4 and 5 leave the merlin unchanged?


If the iteration period is shortened (with higher flight rates), can a smaller vehicle be fielded and matured faster?


I get all the stuff about isp, coking, density, but I'm wondering if programmatically there is an opportunity cost of taking bigger slower steps. And, also added risks. 


What about lost revenue derived from more capable in-space hardware (like constellations, space stations, ..) that would be enabled by an earlier, but less dramatic, reduction in cost/lb to orbit that intermediate steps might offer.

Yes, there might be a rationale for taking a 'halfway' step to increased performance while not impacting operations and infrastructure very much, but the only one that makes sense is the opposite of what you've proposed.  That is, a new Raptor based ITS-like upper stage atop a Falcon Heavy.   This at least puts the ISP/Density fuel tradeoff in the right stages.  But I no longer think this is anywhere in their plans.  I expect an 8+ meter 'ITSy' full bore.  A Merlin based upper stage atop an ITSy booster is a non-starter, for all the reasons above.



Falcon Heavy hasn't flown yet and is much more complicated.

How would this upper-stage land with only one vacuum optimised engine?


If system performance is a function of payload AND no. of reuses; might it be better to make the booster more reusable with Raptors?  It is 70% of the cost of an F9. A single stick Raptor-7 or Raptor-9 booster that requires reduced maintenance and can be reused 100 times could be a money saver.



And if constellations are the primary payload, does their lower orbit counter-act some of the advantage that is gained from methane's improved vacuum isp?


Sea-Level -> Vacuum ISP (from Wikipedia)
Raptor: 334 -> 361
Merlin:  282 -> 311
18%-> 16% difference


Vacuum
Raptor: 382
Merlin: 348
10% difference - improved mass fraction for merlin

Most of that difference in ISP is due to chamber pressure and larger expansion ratio, not fuel type. Higher chamber pressure engines are more efficient at sea level because of the greater difference between nozzle exit pressure and atmospheric pressure.

In vacuum, the chamber pressure becomes more or less irrelevant and only expansion ratio and fuel type matter.

A single-engine upper stage will most likely land like the fairings (either midair catch or into a floating airbag). But ITS upper stages will land propulsively; the 9m version can land on 1 Raptor, as it is nearly a 1/3 mass and thrust scale model of the 12m version. Or it can land on multiple smaller (~1,000 kN) Raptors.
Title: Re: ITS Development Updates and Discussion Thread
Post by: Lar on 08/01/2017 06:56 pm
Raptor upper stage has its own thread and is off-topic for this one. Please consider that thanks.
Title: Re: ITS Development Updates and Discussion Thread
Post by: TomH on 08/01/2017 08:22 pm
Raptor upper stage has its own thread and is off-topic for this one. Please consider that thanks.

Not only is it off topic, we know it is not going to happen. Thus it is totally moot and needs to become mute as well.
Title: Re: ITS Development Updates and Discussion Thread
Post by: TomH on 08/01/2017 08:37 pm
Do Block 4 and 5 leave the merlin unchanged?

This is a different question from the one above where you stated:

Has the merlin reached its final version yet? No.

This is a matter of semantics. Just because Block 5 has not flown does not mean the Merlin has not reached its final iteration. It has. All the engineering is done. The rocket just has not flown yet.