Author Topic: Should ITS have a smaller prototype to ease development?  (Read 11363 times)

Offline redliox

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Looking over the ITS plans and comparing them to either Mars Direct or SLS...it's on the verge of insanely ambitious.  Bear in mind I'm not saying it's impossible (indeed I pray it succeeds, moreso ahead of the SLS/Orion mess), but the SLS, STS, and Saturn V all suffered growing pains in their development.  Would it be easier to build a smaller version of ITS first beforehand or not?  Say something either at 1/2 or 2/3 scaled compared to the full ITS.
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Offline Steve G

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Re: Should ITS have a smaller prototype to ease development?
« Reply #1 on: 02/17/2017 03:46 AM »
When I was a kid watching Apollo 11, and 2001: A Space Odyssey, if you asked me back then that in 50 years would Musk's ITS was too large, I would have expected that kind of scale. But I also expected that there would have been moon bases with commercial flights flying there, and man would be on Mars before the end of the 20th century. So back then, looking 50 years ahead, this would make perfect sense. Somehow, we lost the future that looked so promising back then. What ITS does is give us back the future.

HOWEVER

The scale is ludicrous, and there is no business case for it. I understand Musk's rational, to have the economics to go to Mars for less than a quarter million dollars per passenger. But let's put our business hats on. He should build a 1/4 scale lander, focus on orbital space tourism, lunar tourism and even a true space shuttle for space deliveries. The rocket is too large for just about any commercial or government client. Maintain a cash flow while perfecting the technology and let the systems mature. Sure, there will be duplicate costs by building two systems instead of one, but a two pronged approach won't bankrupt him. It reminds me of Howard Hughes' Spruce Goose. Build it and he can only afford one flight with it.

Online MATTBLAK

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Re: Should ITS have a smaller prototype to ease development?
« Reply #2 on: 02/17/2017 04:28 AM »
He's trying to develop the 747 of Mars transports - when nobody has even done a DC-3 for Mars yet. I love, love the overall concept - but I think the vehicle suffers from 'Giantism'. He wants to build a launcher with more than three point five times the thrust of a Saturn V, with 42 engines in the first stage!! To take 100 persons to Mars; to a place where the infrastructure to support them is a distant dream and probably harder to implement and imagine than the I.T.S. itself at this point.

If Elon was building a reusable launcher and Spacecraft with 'only' approximately twice the thrust of a Saturn V, to send crews of about 12 Astronauts to Mars in what amounted to a smaller moldline replica of the ITS - that I feel would still be an enormous technical and logistical challenge, in of itself. With such a vehicle, a decent sized Martian Outpost could be established with this hardware set, including a Freighter version of the 'Mini-ITS'. If this vehicle works well, then it could be scaled up to match Elon's full-sized ambitions. Sort of how Boeing did the 707 first, then super-sized it's ambitions by developing the 747.

But: I'm aware that Musk is trying to cut to the chase and not split the time and relatively scarce money on two separate development projects. Perhaps he's already taken into account that if he runs into major headaches during the ITS development; he could probably downsize the crew size ambition from 100 to 'only' 50 - which would still itself be a dazzling achievement.
« Last Edit: 02/17/2017 04:30 AM by MATTBLAK »
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Offline GWH

I think yes, if it can be made as a reusable upper stage for F9/FH, with the ability to land payloads on planetary surfaces. Provide a commercial lunar or martian lander.

As it sits right now SpaceX hasn't achieved rapid reuse of booster stages, rapid reuse from orbital velocity is going to be a very large challenge if the shuttle is to be used as an example.   What are the challenges there, and the unknowns?  The ITS is very much dependent on this rapid reusability and would be a very steep learning curve depending on the development of a lot of infrastructure to get to the first orbital test.
If they can start testing and refining on a scaled down single raptor upperstage sooner it could prevent a lot of stumbling after.

If the upper stages are reused from previous commercial launches they could be sent on a one way trip to Mars/Moon while maintaining the cost benefits of reuse.

I think a single raptor refuelable upper stage and cargo landers coupled with commercial habitats and Dragon as a crew lander could be quite capable of putting boots on Mars.

Online Lar

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Re: Should ITS have a smaller prototype to ease development?
« Reply #4 on: 02/17/2017 05:14 AM »
no
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Re: Should ITS have a smaller prototype to ease development?
« Reply #5 on: 02/17/2017 05:20 AM »
What I think Lar meant to say was... ;)
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Online Lar

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Re: Should ITS have a smaller prototype to ease development?
« Reply #6 on: 02/17/2017 05:32 AM »
yes

i had surgery today and i came out of the haze to say this.

There have been a lot of threads about this. the conclusion always is that it is a waste of time and money, and actually slows things down. OP should do their homework and link to all of them.  Why is this time different?
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Online Bynaus

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Re: Should ITS have a smaller prototype to ease development?
« Reply #7 on: 02/17/2017 06:16 AM »
Quote
He's trying to develop the 747 of Mars transports - when nobody has even done a DC-3 for Mars yet.

I actually think that a 100 years from now, the ITS, if it is indeed eventually built and flown, will be seen as a spaceflight analogue to the DC-2/DC-3, rather than the 747 (and the "Heart of Gold" will be more like the DC-1). A very-ambitious-before-built, pushing-the-envelope, early-in-its-era machine that establishes the market it was built to serve. Yes, the DC-3 never had 100 passengers, but passenger numbers are beside the point: what you need is a spacecraft which is large enough to plausibly reach the effects you want - full reusability and big enough so it can carry a useful fuel-production facility to Mars. That it can carry 100 pax if crammed full is just a bonus. The 747s of spaceflight will come much later, once flying between Earth and Mars has become commonplace.

Now, to the main point: I can imagine that there will be more scaled test articles along the way (like the scaled Raptor parts and the shortened tank we have seen), but development of the Heart of Gold will always aim for the real thing. There's simply no point in building an extremely expensive reusable upper stage/interplanetary spaceship/Mars lander/Mars return stage which... cannot make it to Mars and back.

Offline dror

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Re: Should ITS have a smaller prototype to ease development?
« Reply #8 on: 02/17/2017 06:38 AM »
It could only be a waste of money if they ever going to build a full size ITS, which I don't think they will.
Since "100 seats, 100 ton" is arbitrary, I see no reason for them to persue the ITS as was presented.
"20 seats 20 tons" makes more sense to me.
I hope they will develope a 9 Raptor SFR with 1 Raptor SFS to replace FH and do all BEO
For F9 I hope they develope the mini raptor reusable 2nd stage sooner rather than later.

Offline redliox

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Re: Should ITS have a smaller prototype to ease development?
« Reply #9 on: 02/17/2017 08:09 AM »
It seems an interesting split between going full-bore with ITS or something smaller. It gives me further fuel for thought....

The true strength of ITS comes from the booster half, whereas the Interplanetary Spaceship requies help via refueling. If something had to be prioritized, it should be the booster, i.e. the workhorse of this pair.  What if the booster was built at full scale but the ship at half? Assuming a Mars Direct style basis and a crew of 4, not 100 or 50, and perhaps even expending the booster during these prototype flights (ala the early tests of Falcon 9 landings) wouldn't that produce some productive flights without derailing Musk's plans?
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Offline Semmel

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Re: Should ITS have a smaller prototype to ease development?
« Reply #10 on: 02/17/2017 09:39 AM »
I think in this thread, as in past threads on the topic, people think a smaller BFR/ITS would be cheaper that the full size one. I respectfully disagree.

The bulk of the money for this launcher at moment is development and infrastructure up front. That includes but is not limited to:
* Design of BFR
* Design of ITS
* Carbon composite tank development
* Analysis and prove of the design
* Refueling capability in orbit
* EDL design development
* Development of re-usability strategy
* Fuel storage in space (on the way to mars and back)
* Fuel production strategy, design and prototype on Mars
* Fuel production plant on Mars
* Engine development
* BFR/ITS Testing and integration
* Tools to manufacture
* BFR/ITS production
* BFR/ITS operation
* Launch pad and GSE design
* Launch pad and GSE construction
* Astronaut training
* Human rating of the vehicle
* Software on all fronts
(And I probably forgot many)

The things that might save money using a smaller vehicle
* Fuel production plant on Mars
* BFR/ITS Testing and integration
* Tools to manufacture
* BFR/ITS production
* BFR/ITS operation
* Launch pad and GSE construction

And I dont think that the savings on these items scale linearly with capability. I think its much less. And that neglects the other items completely.

All in all, I think development, construction and operation of any vehicle that can go to mars and back is only very weakly dependent on its capability in terms of people/cargo.  And once it flies and you are actually putting cargo on Mars, its far far cheaper to have one large vehicle rather than multiple smaller ones. I would even go as far as claiming that one 100T cargo ITS is cheaper after the first flight than 5 20T cargo ITSes.

If you include everything, I think to minimize the cost of BFR/ITS is to go as big as physically possible that does not bankrupt the company.

I think the proper way of approaching the size question of ITS is to argue why its not even bigger.
« Last Edit: 02/17/2017 09:44 AM by Semmel »

Offline KelvinZero

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Re: Should ITS have a smaller prototype to ease development?
« Reply #11 on: 02/17/2017 10:42 AM »
My layman's guess is that shortening the upper stage (which I understand they are developing first) would be sort of like shortening the space shuttle: a totally different vehicle.

I did wonder about shortening the first stage and having less engines. To what extent would that be a whole new vehicle? I suppose you could also not shorten it, but fill it less and have less engines. The saving would be .. less engines. That is a lot of engines on that thing.

There is also that test vehicle. Is it going to be more like the tanker version of the upper stage? From memory that is like 90 tons dry mass instead of 150 and I assume a lot less parts. That is something.

Offline R7

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Re: Should ITS have a smaller prototype to ease development?
« Reply #12 on: 02/17/2017 11:17 AM »
Just build it as planned and lets see what happens then.
Will it be ridiculuously big for the existing launch market? Yes.
Will it be ridiculuously expensive for the existing launch market? Not necessarily if the reusability pans out.
Will smaller vehicle enable the potentially game-changing Mars exodus opening a new market? No.
(At least SLS will become so silly NASA is forced to axe it and concentrate on something more sensible, like designing colonization infrastructure.)
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Online FutureSpaceTourist

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Re: Should ITS have a smaller prototype to ease development?
« Reply #13 on: 02/17/2017 12:03 PM »
Here are a couple of threads that have previously discussed smaller BFRs/ITSs:

Re: Speculation: SFR (mini-BFR) as fully reusable Falcon Heavy replacement
http://forum.nasaspaceflight.com/index.php?topic=36508.0

Re: Full diameter shortened ITS as FH replacement?
http://forum.nasaspaceflight.com/index.php?topic=41357.0

I imagine it's come up in the various discussion threads too (but I don't have the time to track them!)

Offline uhuznaa

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Re: Should ITS have a smaller prototype to ease development?
« Reply #14 on: 02/17/2017 12:27 PM »
Both Musk and many people here think it would be wasted effort. I think it could have the advantage of building something to use as a fully reusable workhorse launcher (replacing the F9), especially since SpaceX is developing a scaled down Raptor engine contracted by USAF anyway.

Then use more generous mass fractions to ease development of both stages -- you don't need 100t payload to LEO for any commercial payloads anyway and if you can go aluminum instead of composites things get much faster and easier. Then you could get something that you can debug and optimize on a smaller scale, while earning money with it.

Personally I think that the span between what SpaceX is actually flying now on one end and ITS on the other end is so big that nobody really is convinced enough to give them the money to go there. And without money SpaceX will never get around to actually build ITS. They need to add a rung more to that ladder so they can climb it.

From a purely engineering point of view ITS is a bit much to eat with one bite. Starting smaller and with more elbow room in terms of mass fractions would make this much more doable.

Offline IRobot

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Re: Should ITS have a smaller prototype to ease development?
« Reply #15 on: 02/17/2017 12:41 PM »

Personally I think that the span between what SpaceX is actually flying now on one end and ITS on the other end is so big that nobody really is convinced enough to give them the money to go there. And without money SpaceX will never get around to actually build ITS.
Musk could personally finance the first few missions. And with a lot of hype, I'm sure he could make an IPO of SpaceX or a specialized Mars colonization company.

I think he is betting on some of the following sources of money:

- SpaceX
- own money
- NASA
- LEO tourism, ex: Bigelow
- asteroid mining companies

If he proves the capability (with SpaceX and own money), he is hoping that some of those potential customers jump in.

Offline DOCinCT

... and if you can go aluminum instead of composites things get much faster and easier...
Is there any research or studies out there that support the idea that building the LH2 tank for SLS was any faster or substantially less expensive than building the LOX test article out of carbon composite?

Offline su27k

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Re: Should ITS have a smaller prototype to ease development?
« Reply #17 on: 02/17/2017 01:37 PM »
smaller prototype

Depends on what you mean by this. It seems most people read this as a mature subscale system that is ready to take human to Mars, which is strange since in my mind a smaller prototype is something like DC-X or X-33, a test vehicle that is never meant for real missions.

I think it's entirely possible they'll do small prototype vehicle which is used for pathfinding and testing, after all the Raptor being tested is already subscale, so in a sense they're already doing it. It is also possible they'll have to abandon the original ITS size and scale it back to say 1/3 of the original size, due to some constraints (funding, launch site availability, etc). What they will not do, in my opinion, is to develop a subscale fully mature ITS then goes on to develop a full scale ITS, it just serves no purpose and waste a lot of time and resources.

Offline uhuznaa

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Re: Should ITS have a smaller prototype to ease development?
« Reply #18 on: 02/17/2017 01:51 PM »
smaller prototype

Depends on what you mean by this. It seems most people read this as a mature subscale system that is ready to take human to Mars, which is strange since in my mind a smaller prototype is something like DC-X or X-33, a test vehicle that is never meant for real missions.

I think it's entirely possible they'll do small prototype vehicle which is used for pathfinding and testing, after all the Raptor being tested is already subscale, so in a sense they're already doing it. It is also possible they'll have to abandon the original ITS size and scale it back to say 1/3 of the original size, due to some constraints (funding, launch site availability, etc). What they will not do, in my opinion, is to develop a subscale fully mature ITS then goes on to develop a full scale ITS, it just serves no purpose and waste a lot of time and resources.

Of course a scaled down ITS with more lenient mass fractions wouldn't be an "Interplanetary Transport System" anymore. It would just be a fully reusable two stage orbital launcher. Useful for earning money by selling launches and also by launching the 4000 satellites SpaceX is talking about. And for learning how to build and operate such a thing before going all the way and building a Mars craft.

And at the moment I just can't see ITS ever happening. Musk talked about $5m that SpaceX will invest in development each year. This is basically nothing. Without a few billions from others ITS will never happen. And without showing others that the concept is valid nobody will invest that kind of money.

Offline uhuznaa

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Re: Should ITS have a smaller prototype to ease development?
« Reply #19 on: 02/17/2017 02:01 PM »
... and if you can go aluminum instead of composites things get much faster and easier...
Is there any research or studies out there that support the idea that building the LH2 tank for SLS was any faster or substantially less expensive than building the LOX test article out of carbon composite?

Using the money spent on SLS as a yardstick is pointless. Fact is that SpaceX is already using aluminum for the Falcon 9 first and second stages all the time and scaling this up for a smaller ITS-like launcher would be much cheaper and easier than using composites, especially for a reusable craft that goes through lots of hard thermal cycles and mechanical loads. The fact that they had a failing small composite tank ruin a rocket and payload and launchpad a few months ago doesn't exactly instill confidence here.

And it doesn't matter anyway what you or me believe: SpaceX will need to convince people to bet billions of dollars on them being able to do this. Right now this is very hard to do. Staying in their comfort-zone as far as possible and proving the concept would be the way to go and if they get an orbital workhorse by doing this, all the better.

Offline RotoSequence

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Re: Should ITS have a smaller prototype to ease development?
« Reply #20 on: 02/17/2017 02:05 PM »
The test ITS tank seems to have failed cryo-testing. No details as yet, but it has definitely broken apart.

https://imgur.com/a/bGHR6

"Should they..." is probably only going to get messier based on the number of tanks they go through in testing.

Offline spacenut

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Re: Should ITS have a smaller prototype to ease development?
« Reply #21 on: 02/17/2017 02:22 PM »
Once the Raptor engine is developed.  Then, I have the following questions.

1. Do you have the manufacturing infrastructure to build ITS?
2. Do you have the transportation infrastructure to get ITS to the launch pad?
3. Do you have the launch facilities to handle 20 million or more lbs of thrust?
4. Do you have the landing facilities, either on land or on a ship for such a rocket to land, or is it going to land back at the launch pad?
5. What about sound and vibration of such a launch for nearby areas?  Does such a launch facility need to be remote?, near the equator?, or such?

As you can see, the infrastructure for such a beast is going to cost a lot.  Probably more than one of the ITS rockets itself. 

Things to consider.  Pads 39a and 39b are capable of 12 million lbs thrust now.  Just some modifications needed for something that size or smaller.  Anything larger than 12 m in diameter cannot fit the existing barge, river and inland waterway transportation system in America, and it is extensive already. 

I think it should be no larger than NASA's old Nova rocket of 12 million lbs thrust to use the existing facilities at the Cape.  Maybe scale it down to 50 people and 50 tons to Mars.  Unless Governments chip in and buy's launches for their colonization efforts to not be left out. 

Offline envy887

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Re: Should ITS have a smaller prototype to ease development?
« Reply #22 on: 02/17/2017 03:14 PM »
Once the Raptor engine is developed.  Then, I have the following questions.

1. Do you have the manufacturing infrastructure to build ITS?
2. Do you have the transportation infrastructure to get ITS to the launch pad?
3. Do you have the launch facilities to handle 20 million or more lbs of thrust?
4. Do you have the landing facilities, either on land or on a ship for such a rocket to land, or is it going to land back at the launch pad?
5. What about sound and vibration of such a launch for nearby areas?  Does such a launch facility need to be remote?, near the equator?, or such?

As you can see, the infrastructure for such a beast is going to cost a lot.  Probably more than one of the ITS rockets itself. 

Things to consider.  Pads 39a and 39b are capable of 12 million lbs thrust now.  Just some modifications needed for something that size or smaller.  Anything larger than 12 m in diameter cannot fit the existing barge, river and inland waterway transportation system in America, and it is extensive already. 

I think it should be no larger than NASA's old Nova rocket of 12 million lbs thrust to use the existing facilities at the Cape.  Maybe scale it down to 50 people and 50 tons to Mars.  Unless Governments chip in and buy's launches for their colonization efforts to not be left out.

Thrust and diameter aren't really related though. They could build a much shorter 12m booster with say 18 engines, keep the same spaceship, and just reduce the payload to orbit to 125 tonnes (160 tonnes for the tanker). It would just take more launches to refill the ship in orbit. Is that worthwhile? I don't know.

For a minimum viable Mars mission, they don't even need the booster. A 6m diameter version of the spaceship launched on FH could put about 50 tonnes and at least 6 or 8 crew to Mars surface.

Offline Nomadd

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Re: Should ITS have a smaller prototype to ease development?
« Reply #23 on: 02/17/2017 03:21 PM »
The test ITS tank seems to have failed cryo-testing. No details as yet, but it has definitely broken apart.

https://imgur.com/a/bGHR6

"Should they..." is probably only going to get messier based on the number of tanks they go through in testing.
You can't assume there's a problem. Stuff like that is often tested to destruction. Being too strong would point to a problem in their model the same as being too weak.
« Last Edit: 02/17/2017 04:05 PM by Nomadd »

Offline envy887

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Re: Should ITS have a smaller prototype to ease development?
« Reply #24 on: 02/17/2017 03:25 PM »
Looking over the ITS plans and comparing them to either Mars Direct or SLS...it's on the verge of insanely ambitious.  Bear in mind I'm not saying it's impossible (indeed I pray it succeeds, moreso ahead of the SLS/Orion mess), but the SLS, STS, and Saturn V all suffered growing pains in their development.  Would it be easier to build a smaller version of ITS first beforehand or not?  Say something either at 1/2 or 2/3 scaled compared to the full ITS.

Are you suggesting 1/2 or 2/3 the diameter? Or 1/2 to 2/3 the mass and volume? There's a big difference since mass and volume scale as diameter cubed.

1/2 scale by diameter could be easily launched on Falcon Heavy, while 1/2 scale by mass/volume would dwarf Saturn V.

Offline john smith 19

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Re: Should ITS have a smaller prototype to ease development?
« Reply #25 on: 02/17/2017 04:58 PM »
The test ITS tank seems to have failed cryo-testing. No details as yet, but it has definitely broken apart.

https://imgur.com/a/bGHR6

"Should they..." is probably only going to get messier based on the number of tanks they go through in testing.
Are we sure this really is a picture of an ITS test tank? I'd expected something "stiffer." This looks like rubber. Also very surprised that is what Hawthorne or Texas looks like.

The tanks seem to be a major part of ITS. Big composites, carrying sub cooled cryogens, multiple cycles of launch/transit/entry/ over decades.

This is not a large soda bottle wrapped in string.  :( It's a long way past the SoA, never mind the common SoP.
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Offline RotoSequence

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Re: Should ITS have a smaller prototype to ease development?
« Reply #26 on: 02/17/2017 05:03 PM »
The test ITS tank seems to have failed cryo-testing. No details as yet, but it has definitely broken apart.

https://imgur.com/a/bGHR6

"Should they..." is probably only going to get messier based on the number of tanks they go through in testing.
Are we sure this really is a picture of an ITS test tank? I'd expected something "stiffer." This looks like rubber. Also very surprised that is what Hawthorne or Texas looks like.

The tanks seem to be a major part of ITS. Big composites, carrying sub cooled cryogens, multiple cycles of launch/transit/entry/ over decades.

This is not a large soda bottle wrapped in string.  :( It's a long way past the SoA, never mind the common SoP.

We're sure it's the tank. The ITS test article was built by Janicki Industries of Sedro-Woolley, Washington; the tank never left the Puget Sound region.

Offline wannamoonbase

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Re: Should ITS have a smaller prototype to ease development?
« Reply #27 on: 02/17/2017 05:16 PM »
Both Musk and many people here think it would be wasted effort. I think it could have the advantage of building something to use as a fully reusable workhorse launcher (replacing the F9), especially since SpaceX is developing a scaled down Raptor engine contracted by USAF anyway.

Then use more generous mass fractions to ease development of both stages -- you don't need 100t payload to LEO for any commercial payloads anyway and if you can go aluminum instead of composites things get much faster and easier. Then you could get something that you can debug and optimize on a smaller scale, while earning money with it.

Personally I think that the span between what SpaceX is actually flying now on one end and ITS on the other end is so big that nobody really is convinced enough to give them the money to go there. And without money SpaceX will never get around to actually build ITS. They need to add a rung more to that ladder so they can climb it.

From a purely engineering point of view ITS is a bit much to eat with one bite. Starting smaller and with more elbow room in terms of mass fractions would make this much more doable.

Completely agree.

ITS, although bold and sexy on a power point slide, is such a huge step its hard to see how a small company with limited resources can develop such a vehicle without decades of time and money.

Developing a raptor powered F9 replacement with a fully reuseable second stage would provide many learning opportunities and allow flight history for Raptor.  Throw more Raptors underneath a SFR than needed, give it lots of margin for commercial payloads and work on reusability and maybe even the very bold plan for landing on a launch mount. 

I think ITS is a fantasy and won't see the light of day for many years, if ever.
I know they don't need it, but Crossfeed would be super cool.

Offline Oli

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Re: Should ITS have a smaller prototype to ease development?
« Reply #28 on: 02/17/2017 06:13 PM »
A typical mid-L/D Mars lander with 40mt payload has the dimensions 30m x 10m.

ITS has the dimensions 50m x 12m. Only ~1/3 of that volume is available for the payload, so it's questionable whether SpaceX can land much more volume on Mars than a typical 40mt lander from NASA. DRM 5.0 needs 2 40mt landers.

Making ITS smaller in terms of volume might not be an option if SpaceX plans to sells Mars flights to NASA.
« Last Edit: 02/17/2017 06:14 PM by Oli »

Offline philw1776

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Re: Should ITS have a smaller prototype to ease development?
« Reply #29 on: 02/17/2017 06:27 PM »
The ITS is built to the wrong scale, it's a fantasy, etc. crowd simply can't get their heads around the proven fact, time and again, that Musk is a paradigm breaking innovator.  OK, he's not good meeting his schedules.
I have an MBA in finance from a good B school plus my engineering degree.  I was aghast at Musk's business plan to merge Solar City with Tesla and I feared disaster.  But if I knew what I was doing I would have bought Tesla stock just a few months ago and would now have a tidy sum as the stock instead of tanking has skyrocketed.  I was with the financial expert crowd underestimating the guy. But I digress.

On topic, the ITS will be tested as Musk outlined in his Powerpoint show.  He can't afford the dollars and more importantly to him personally the TIME wasted in mini-ITS whatevers that do not lead directly to his goal. Per his 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.

« Last Edit: 02/17/2017 06:28 PM by philw1776 »
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Offline MikeAtkinson

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Re: Should ITS have a smaller prototype to ease development?
« Reply #30 on: 02/17/2017 06:29 PM »
A typical mid-L/D Mars lander with 40mt payload has the dimensions 30m x 10m.

ITS has the dimensions 50m x 12m. Only ~1/3 of that volume is available for the payload, so it's questionable whether SpaceX can land much more volume on Mars than a typical 40mt lander from NASA. DRM 5.0 needs 2 40mt landers.

Making ITS smaller in terms of volume might not be an option if SpaceX plans to sells Mars flights to NASA.

So about 1,800 m3 of volume for payload, at CRS payload densities that is over 200 tonnes, SpaceX say that they will land 100 tonnes (maybe more later).

Online guckyfan

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Re: Should ITS have a smaller prototype to ease development?
« Reply #31 on: 02/17/2017 06:54 PM »
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

I like that approach, a lot. As far as I remember, a completely new suggestion that makes a lot of sense to me. But I am not an expert.

Offline envy887

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Re: Should ITS have a smaller prototype to ease development?
« Reply #32 on: 02/17/2017 07:37 PM »
A typical mid-L/D Mars lander with 40mt payload has the dimensions 30m x 10m.

ITS has the dimensions 50m x 12m. Only ~1/3 of that volume is available for the payload, so it's questionable whether SpaceX can land much more volume on Mars than a typical 40mt lander from NASA. DRM 5.0 needs 2 40mt landers.

Making ITS smaller in terms of volume might not be an option if SpaceX plans to sells Mars flights to NASA.

So about 1,800 m3 of volume for payload, at CRS payload densities that is over 200 tonnes, SpaceX say that they will land 100 tonnes (maybe more later).
The IAC presentation says up to 450 tonnes landed. Nominally 300.

Offline MikeAtkinson

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Re: Should ITS have a smaller prototype to ease development?
« Reply #33 on: 02/17/2017 08:10 PM »
A typical mid-L/D Mars lander with 40mt payload has the dimensions 30m x 10m.

ITS has the dimensions 50m x 12m. Only ~1/3 of that volume is available for the payload, so it's questionable whether SpaceX can land much more volume on Mars than a typical 40mt lander from NASA. DRM 5.0 needs 2 40mt landers.

Making ITS smaller in terms of volume might not be an option if SpaceX plans to sells Mars flights to NASA.

Yes, my mistake. Still anything over about 200 tonnes would require a greater density than CRS cargo to the ISS. Not impossible for bulk products (metals/chemicals, dry/frozen foodstuff, etc.)

So about 1,800 m3 of volume for payload, at CRS payload densities that is over 200 tonnes, SpaceX say that they will land 100 tonnes (maybe more later).
The IAC presentation says up to 450 tonnes landed. Nominally 300.

Offline Rei

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Re: Should ITS have a smaller prototype to ease development?
« Reply #34 on: 02/18/2017 01:41 AM »
The test ITS tank seems to have failed cryo-testing. No details as yet, but it has definitely broken apart.

https://imgur.com/a/bGHR6

"Should they..." is probably only going to get messier based on the number of tanks they go through in testing.

And they're only doing the most basic, inert testing right now...

Composites are tough.  Composites with cryogenics, incredibly tough.  I hope they can pull it off.  I really don't know if they can.

I don't recall, is the ultimate plan to have the tank lined or unlined?  At least with lined you can get rid of a lot of the oxygen/CF reaction concerns.

Offline Rei

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Re: Should ITS have a smaller prototype to ease development?
« Reply #35 on: 02/18/2017 01:44 AM »
A typical mid-L/D Mars lander with 40mt payload has the dimensions 30m x 10m.

ITS has the dimensions 50m x 12m. Only ~1/3 of that volume is available for the payload, so it's questionable whether SpaceX can land much more volume on Mars than a typical 40mt lander from NASA. DRM 5.0 needs 2 40mt landers.

Making ITS smaller in terms of volume might not be an option if SpaceX plans to sells Mars flights to NASA.

So about 1,800 m3 of volume for payload, at CRS payload densities that is over 200 tonnes, SpaceX say that they will land 100 tonnes (maybe more later).
The IAC presentation says up to 450 tonnes landed. Nominally 300.

Yeah, they're looking at non-Hohmann transfers.  Which actually is pretty reasonable when you start digging down into the numbers.  You get a lot of trip shortening with that first extra bit of delta-V (it's a case of diminishing returns after that).  And from an economics perspective, they have a lot of sunk costs in that ship doing nothing when it's just drifting through space.  The sooner they can get it back to earth and relaunch, the better their economics work out to be.  So it's worth sacrificing cargo.

Offline envy887

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Re: Should ITS have a smaller prototype to ease development?
« Reply #36 on: 02/18/2017 02:13 AM »
A typical mid-L/D Mars lander with 40mt payload has the dimensions 30m x 10m.

ITS has the dimensions 50m x 12m. Only ~1/3 of that volume is available for the payload, so it's questionable whether SpaceX can land much more volume on Mars than a typical 40mt lander from NASA. DRM 5.0 needs 2 40mt landers.

Making ITS smaller in terms of volume might not be an option if SpaceX plans to sells Mars flights to NASA.

So about 1,800 m3 of volume for payload, at CRS payload densities that is over 200 tonnes, SpaceX say that they will land 100 tonnes (maybe more later).
The IAC presentation says up to 450 tonnes landed. Nominally 300.

Yeah, they're looking at non-Hohmann transfers.  Which actually is pretty reasonable when you start digging down into the numbers.  You get a lot of trip shortening with that first extra bit of delta-V (it's a case of diminishing returns after that).  And from an economics perspective, they have a lot of sunk costs in that ship doing nothing when it's just drifting through space.  The sooner they can get it back to earth and relaunch, the better their economics work out to be.  So it's worth sacrificing cargo.

The transfer windows don't really work out that way. If you get to Mars faster, you just end up having to wait longer to launch back to Earth, and you get back at the same time. Unless you're flying a opposition class mission with a 30-day stay, a return inside the orbit of Venus, and a 15-20 km/s reentry, you always get back too late for the next launch opportunity.

Even a opposition class mission would likely allow ITS to carry 350 to 400 tonnes of cargo, though it's return cargo would likely be limited to less than 50 tonnes.

Offline redliox

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Re: Should ITS have a smaller prototype to ease development?
« Reply #37 on: 02/18/2017 04:51 AM »
Looking over the ITS plans and comparing them to either Mars Direct or SLS...it's on the verge of insanely ambitious.  Bear in mind I'm not saying it's impossible (indeed I pray it succeeds, moreso ahead of the SLS/Orion mess), but the SLS, STS, and Saturn V all suffered growing pains in their development.  Would it be easier to build a smaller version of ITS first beforehand or not?  Say something either at 1/2 or 2/3 scaled compared to the full ITS.

Are you suggesting 1/2 or 2/3 the diameter? Or 1/2 to 2/3 the mass and volume? There's a big difference since mass and volume scale as diameter cubed.

1/2 scale by diameter could be easily launched on Falcon Heavy, while 1/2 scale by mass/volume would dwarf Saturn V.

Specifically mass since that influences a rocket's ability to escape Earth.

Going by some of the statistics the ship and tanker have, the crew ship dry mass is supposed to be 150 (metric I presume) tons and the tanker 90; the difference between the 2 no doubt because of crew needs.  Propellant for each adds 1950 and 2500 tons respectively.  A fully fueled crew spaceship would thus weigh 2100 mt.

Compared to Zubrin's Mars Direct vehicles this is a huge difference; nearly 100 times more massive than the Hab lander's mass of 25mt.  Elon Musk is obviously planning big to accommodate future economics, but even if scaled down this means a smaller version of the ITS ship would be a great asset.  A half-scale prototype would still be 75 mt, or otherwise 3 times the size of Zubrin's vehicles and even larger than some of NASA's plans (which I think I saw as high as 60 mt).  While no cruise ship, this would be more than sufficient for NASA or anyone's needs.  Before I forget, including fuel (also reduced by 50% resulting in 975 mt of methalox) the total mass of a mini-Interplanetary Spaceship comes to 1050 mt.

Doing a few delta-v calculations assuming 2 things:
1) Specific Impulse of 360ISP for methalox
2) Use of a full scale ITS booster while flying a 1/2 scale spaceship atop it

An ITS booster (again at FULL scale and going by SpaceX figures) is 275 mt dry mass with 6700 mt of propellant.  Coupled with 1050 of a mini-ship, the whole thing at launch would be 8025 mt.  The booster would give the ship about 6.3 km/s of delta-v, assuming a full burn and no recovery.  The mini-ship would then have to burn roughly 670 mt of its own fuel to enter solid LEO (which requires better than 9 km/s to hit).

In LEO without any refueling, this mini-ship would weigh a total of 380 mt with 305 of methalox still available.  Assuming 4 km/s to reach and manage a Hohmann transfer orbit, 260 mt would be burned to reach Mars.  The remaining 45 mt of methalox would grant a further 1.6 km/s.  While 1.6 km/s is meager, this would be sufficient to split between orbital capture and landing with aerobraking between the 2.

Someone double-check my figures to be certain; however I think for a smaller mission this could suffice to get the ship to Mars even without the tanker Elon wants in the full version.
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Online OneSpeed

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Re: Should ITS have a smaller prototype to ease development?
« Reply #38 on: 02/18/2017 10:59 AM »
Looking over the ITS plans and comparing them to either Mars Direct or SLS...it's on the verge of insanely ambitious.  Bear in mind I'm not saying it's impossible (indeed I pray it succeeds, moreso ahead of the SLS/Orion mess), but the SLS, STS, and Saturn V all suffered growing pains in their development.  Would it be easier to build a smaller version of ITS first beforehand or not?  Say something either at 1/2 or 2/3 scaled compared to the full ITS.

Are you suggesting 1/2 or 2/3 the diameter? Or 1/2 to 2/3 the mass and volume? There's a big difference since mass and volume scale as diameter cubed.

1/2 scale by diameter could be easily launched on Falcon Heavy, while 1/2 scale by mass/volume would dwarf Saturn V.

...

Someone double-check my figures to be certain; however I think for a smaller mission this could suffice to get the ship to Mars even without the tanker Elon wants in the full version.

Not suggesting there is anything wrong with your ΔV calculations, but when you talk about a scale model, that refers to a linear dimension, not to mass. What you are describing is roughly a 0.8 scale model of the ITS.

Online Lar

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Re: Should ITS have a smaller prototype to ease development?
« Reply #39 on: 02/18/2017 11:11 AM »
Reasons to close this thread
- So much concern trolling
- So little that's not been said in other threads.
- So many incorrect statements
- So much lack of understanding of Musk's plans

Reasons to leave this thread open
- It's a place to send the concern trolls so we can keep them out of other threads.

That one's winning, so far.
"I think it would be great to be born on Earth and to die on Mars. Just hopefully not at the point of impact." -Elon Musk
"We're a little bit like the dog who caught the bus" - Musk after CRS-8 S1 successfully landed on ASDS OCISLY

Offline Rei

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Re: Should ITS have a smaller prototype to ease development?
« Reply #40 on: 02/18/2017 12:50 PM »
Quote
If you get to Mars faster, you just end up having to wait longer to launch back to Earth, and you get back at the same time. Unless you're flying a opposition class mission with a 30-day stay

There is zero stay requirement for ITS, apart from time to offload, reload, and refuel.  ITS is not intended to function as a Martian habitat.  It can fly conjunction and opposition class, with or without Venus assist on opposition.  SpaceX has also put emphasis on non-Mars destinations.  There is additionally a requirement for refurbishment on Earth (they don't give times for it, but they do give a budget - $10M).  All questions of realism of their budget figures directed away from me  ;)
« Last Edit: 02/18/2017 01:07 PM by Rei »

Offline muomega0

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Re: Should ITS have a smaller prototype to ease development?
« Reply #41 on: 02/18/2017 12:57 PM »
The ITS approach showed the world that if you wanted to colonize Mars, one needs the entire architecture and hardware based on reuse with in space refueling.  Innovations further improve the mass fractions/economics.

ITS highlighted the deep flaws of SLS and Ares: completely expendable with no ability to meet #1 Space Grand Challenge Economic Access to Space in the short term nor 'Colonize' Mars in the long term.

The ITS approach showed the world that a part of NASA controlled by Congress only wants to build and operate decades old expensive rotary phone technology to relive Apollo again.

The ITS showed the shuttle derived folks how to approach the future, and that they too can be a part of a great future.  There is so much to do!

2004 VSE
For future, sustainable exploration programs, NASA requires cost-effective vehicles that may be reused, have systems that could be applied to more than one destination, and are highly reliable and need only small ground crews. NASA plans to invest in a number of new approaches to exploration, such as robotic networks, modular systems, pre-positioned propellants, advanced power and propulsion, and in-space assembly, that could enable these kinds of vehicles  without the VSE: 3 Flaws with just a few words

The ITS is built to the wrong scale, it's a fantasy, etc. crowd simply can't get their heads around the proven fact,
In many cases building a component other than full scale ignores 'scalability'--It works at smaller dimensions and not at larger dimensions.

Note however that SLS then is too small for Mars Colonization for the future, and too big for and expendable to cut costs today.  Between a rock and a hard place.

Reasons to close this thread
- So much concern trolling
- So little that's not been said in other threads.
- So many incorrect statements
- So much lack of understanding of Musk's plans

Reasons to leave this thread open
- It's a place to send the concern trolls so we can keep them out of other threads.

That one's winning, so far.
When you have nothing in defense of your poorly laid out plans other than to support the base and the top 1%, the result has been  http://alternativefacts.com  .  Sadly, to support the base requires actions outside of reason  but there our lines not to cross.
« Last Edit: 03/17/2017 11:32 AM by muomega0 »

Offline envy887

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Re: Should ITS have a smaller prototype to ease development?
« Reply #42 on: 02/18/2017 05:45 PM »
Quote
If you get to Mars faster, you just end up having to wait longer to launch back to Earth, and you get back at the same time. Unless you're flying a opposition class mission with a 30-day stay

There is zero stay requirement for ITS, apart from time to offload, reload, and refuel.
It has to wait for a transfer window that's within it's delta-v and other capability limitations. Those aren't clearly defined yet.

Offline RonM

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Re: Should ITS have a smaller prototype to ease development?
« Reply #43 on: 02/18/2017 06:03 PM »
A typical mid-L/D Mars lander with 40mt payload has the dimensions 30m x 10m.

ITS has the dimensions 50m x 12m. Only ~1/3 of that volume is available for the payload, so it's questionable whether SpaceX can land much more volume on Mars than a typical 40mt lander from NASA. DRM 5.0 needs 2 40mt landers.

Making ITS smaller in terms of volume might not be an option if SpaceX plans to sells Mars flights to NASA.

So about 1,800 m3 of volume for payload, at CRS payload densities that is over 200 tonnes, SpaceX say that they will land 100 tonnes (maybe more later).
The IAC presentation says up to 450 tonnes landed. Nominally 300.

DRM 5.0 requires two landers totaling 80 tonnes to the surface. A scaled down ITS capable of landing 100 tonnes would make a great first generation ship. So about 1/3 mass of the full scale ITS.

While the first generation ships are setting up the base and preparing for colonization, the full scaled ITS could be developed.

At 1/3 mass, the first generation ships would be cheaper and not overtax Pad 39A. A full scale ITS is going to take a new pad or a rebuilt 39A, either one an expensive project.

Offline Pipcard

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Re: Should ITS have a smaller prototype to ease development?
« Reply #44 on: 02/18/2017 06:41 PM »
ITS highlighted the deep flaws of SLS and Ares: completely expendable with no ability to meet #1 Space Grand Challenge Economic Access to Space in the short term nor 'Colonize' Mars in the long term.

Do you know why Ares was designed as an expendable vehicle in the first place?

I'm saying this yet again: before SpaceX started designing the MCT/ITS, almost no one thought that there was going to be enough demand to make development of reusable super-heavy lift launch vehicles worthwhile.
« Last Edit: 02/18/2017 06:50 PM by Pipcard »

Offline Robotbeat

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Re: Should ITS have a smaller prototype to ease development?
« Reply #45 on: 02/18/2017 06:42 PM »
Quote
If you get to Mars faster, you just end up having to wait longer to launch back to Earth, and you get back at the same time. Unless you're flying a opposition class mission with a 30-day stay

There is zero stay requirement for ITS, apart from time to offload, reload, and refuel.  ITS is not intended to function as a Martian habitat. ...
That's not true. Musk explicitly said the crew would stay in the ITS while on the surface.
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Offline envy887

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Re: Should ITS have a smaller prototype to ease development?
« Reply #46 on: 02/18/2017 07:33 PM »
ITS highlighted the deep flaws of SLS and Ares: completely expendable with no ability to meet #1 Space Grand Challenge Economic Access to Space in the short term nor 'Colonize' Mars in the long term.

Do you know why Ares was designed as an expendable vehicle in the first place?

I'm saying this yet again: before SpaceX started designing the MCT/ITS, almost no one thought that there was going to be enough demand to make development of reusable super-heavy lift launch vehicles worthwhile.

More because Ares HAD to be Shuttle-derived but without the only economically reusable part of the Shuttle. And being Shuttle-derived it was stuck with an inefficient architecture that made the performance hit from reuse prohibitive.

A prototype ITS flying on reusable Falcon Heavy boosters could attack the problem from the opposite end the Shuttle did: return the easy part (the boosters) and expend the orbiter if necessary. It wouldn't have to fly a lot to learn a great amount, and it could make some money while doing testing after the primary mission, like Falcon boosters do.

Online Lar

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Re: Should ITS have a smaller prototype to ease development?
« Reply #47 on: 02/18/2017 08:57 PM »

Note however that SLS then is too small for Mars Colonization for the future, and too big for and expendable to cut costs today.  Between a rock and a hard place.
show yout work.... i thimk it is just right.
Quote
Reasons to close this thread
- So much concern trolling
- So little that's not been said in other threads.
- So many incorrect statements
- So much lack of understanding of Musk's plans

Reasons to leave this thread open
- It's a place to send the concern trolls so we can keep them out of other threads.

That one's winning, so far.
When you have nothing in defense of your poorly laid out plans other than to support the base and the top 1%, the result has been  http://alternativefacts.com  .  Sadly, to support the base requires actions outside of reason  but their our lines not to cross.
you just described SLS... poorly laid out plans redux...
"I think it would be great to be born on Earth and to die on Mars. Just hopefully not at the point of impact." -Elon Musk
"We're a little bit like the dog who caught the bus" - Musk after CRS-8 S1 successfully landed on ASDS OCISLY

Offline envy887

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Re: Should ITS have a smaller prototype to ease development?
« Reply #48 on: 02/18/2017 10:00 PM »

Note however that SLS then is too small for Mars Colonization for the future, and too big for and expendable to cut costs today.  Between a rock and a hard place.
show yout work.... i thimk it is just right.
Quote
Reasons to close this thread
- So much concern trolling
- So little that's not been said in other threads.
- So many incorrect statements
- So much lack of understanding of Musk's plans

Reasons to leave this thread open
- It's a place to send the concern trolls so we can keep them out of other threads.

That one's winning, so far.
When you have nothing in defense of your poorly laid out plans other than to support the base and the top 1%, the result has been  http://alternativefacts.com  .  Sadly, to support the base requires actions outside of reason  but their our lines not to cross.
you just described SLS... poorly laid out plans redux...

Still a little groggy, Lar? :D

Online Lar

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Re: Should ITS have a smaller prototype to ease development?
« Reply #49 on: 02/18/2017 10:15 PM »
much more alert...
"I think it would be great to be born on Earth and to die on Mars. Just hopefully not at the point of impact." -Elon Musk
"We're a little bit like the dog who caught the bus" - Musk after CRS-8 S1 successfully landed on ASDS OCISLY

Offline Rei

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Re: Should ITS have a smaller prototype to ease development?
« Reply #50 on: 02/19/2017 12:04 AM »
Quote
If you get to Mars faster, you just end up having to wait longer to launch back to Earth, and you get back at the same time. Unless you're flying a opposition class mission with a 30-day stay

There is zero stay requirement for ITS, apart from time to offload, reload, and refuel.  ITS is not intended to function as a Martian habitat. ...
That's not true. Musk explicitly said the crew would stay in the ITS while on the surface.

Is that so?  I need to watch the presentation again then, my understanding was that the idea was for ITS to function as cargo / people delivery, not surface habitation.

Ed: Just rewatched it; I saw nothing about using ITS as a habitat.  Quite to the contrary, it was explicitly stated that they're seeking to avoid having ITS vehicles collect and sit around on the surface of Mars.

Where did you see something stating that ITS would be used as a habitat?
« Last Edit: 02/19/2017 01:49 AM by Rei »

Offline redliox

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Re: Should ITS have a smaller prototype to ease development?
« Reply #51 on: 02/19/2017 03:15 AM »
Interesting mix of responses so far in this thread.  In addition to the voice of Lars-slayer-of-Trolls I notice 3 opinions come up regularly from differing people:

1) Make a smaller ITS for quicker development
2) Make full-scale ITS to avoid complicating development
3) Potential use of ITS as a Martian habitat

The first two are actually equal in merit; a smaller ship might be easier to build, but scaling it up later might generate development problems.  One lesson the STS/shuttle taught us: implementing (significant) vehicle improvements are nearly impossible to do while on a budget, which NASA is likely to be tight on for the foreseeable future.  In the case of the SLS, especially if competition from Blue Origin and SpaceX emerge, it may advance no further than block 1B or forced to settle for a maximum liftoff mass less than the 130 mt intended for 2.  My personal opinion on the matter of a mini-ITS: miniaturize the spaceship/payload component but fly the booster itself at full-scale; that way SpaceX has the workhorse at full strength.

Using the ITS spaceship as a habitat is an interesting thought.  Drawing on Mars Direct for comparison, it's meant to be more like a giant ERV rather than a Hab.  However, especially at full scale, the spaceship may as well be a luxury yacht given it's bigger than the total module volume of the ISS.  All the same, it's a ship not a hotel.

These questions ought to be given to Elon Musk directly if possible.  ITS is his baby, and I'm sure his engineers are trying to prepare its delivery.
"Let the trails lead where they may, I will follow."
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Offline TomH

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Re: Should ITS have a smaller prototype to ease development?
« Reply #52 on: 02/19/2017 03:53 AM »
IF SpaceX did start with a smaller prototype, them segue to the full sized ITS, how feasible would it be for them then to sell the prototype to NASA for use in Lunar exploration?

Offline Space Ghost 1962

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Re: Should ITS have a smaller prototype to ease development?
« Reply #53 on: 02/19/2017 04:45 AM »
Give it up already. No HSF craft ever had a "mini me", no one ever will.  ::)

Online guckyfan

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Re: Should ITS have a smaller prototype to ease development?
« Reply #54 on: 02/19/2017 04:51 AM »
Where did you see something stating that ITS would be used as a habitat?

Elon Musk had said this before. It makes all kind of sense too. We must always differentiate between the long term intended use, that is return after refuelling and specific mission requirements. The first crew arrives and there is no other habitat than the ITS at that time. ITS is plenty big for a crew of 12 to 18. There is likely also no fuel for an immediate return of the ITS.

So they get there, live in the ITS until they have set up fuel ISRU and possibly a habitat. Later missions would arrive and there is a habitat waiting for them and fuel in the tanks. They disembark, unload cargo and the ship goes back. Will they even have a ship on standby? I doubt it.

Offline GWH

IF SpaceX did start with a smaller prototype, them segue to the full sized ITS, how feasible would it be for them then to sell the prototype to NASA for use in Lunar exploration?

Prototype as an F9/FH upper stage coupled with LEO refueling I thinkthat would be very effective and fill in a need that could only be met by one other player (ULA + xues).  Dragon can act as a crew lander.

I think there is a very crucial definition that needs to be made on the mini ITS in this discussion . Which is whether it is an extension on existing systems(New US only, no crew inside) to test tech and prove out feasibility vs a partial scale version of the whole system.

Offline Rei

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Re: Should ITS have a smaller prototype to ease development?
« Reply #56 on: 02/19/2017 11:31 AM »
Where did you see something stating that ITS would be used as a habitat?

Elon Musk had said this before. It makes all kind of sense too. We must always differentiate between the long term intended use, that is return after refuelling and specific mission requirements. The first crew arrives and there is no other habitat than the ITS at that time. ITS is plenty big for a crew of 12 to 18. There is likely also no fuel for an immediate return of the ITS.

So they get there, live in the ITS until they have set up fuel ISRU and possibly a habitat. Later missions would arrive and there is a habitat waiting for them and fuel in the tanks. They disembark, unload cargo and the ship goes back. Will they even have a ship on standby? I doubt it.

I'm trying to find anywhere that he actually said that.  Do you perchance have a link?  What I have is:

https://www.youtube.com/watch?v=H7Uyfqi_TE8?t=801

Re, local propellant production: "Again, if we didn't do this, it would have at least a half order of magnitude increase in the cost of a trip, so 500% increase in the cost of a trip. And it would be pretty absurd to try to build a city on Mars if your spaceships just kept on staying on Mars and not going back to Earth. You would have this, like, massive graveyard of ships.  You would have to, like, do something with them. So it really wouldn't make sense to leave your spaceships on Mars, you really want to build a propellant plant on Mars and send the ships back."

To be fair, this could be interpreted through the lens of "eventually".  There still is the question of what to do in the beginning - whether a propellant plant and tanks would be delivered by Red Dragon, or whether you have to have one ITS sitting around acting as a refuelling tank, with its payload being a propellant plant.  But that describes only a very small number of ships, and still says nothing about using ITS ships as habitats.  I know Zubrin at the very least hasn't interpreted Musk's statements as meaning using the spaceships as habitats - he published an editorial criticizing Musk for that purpose:

http://www.thenewatlantis.com/publications/colonizing-mars

Quote
7. The sending of a large habitat on a roundtrip from Earth to Mars and back. This, too, is a very bad idea, because the habitat will get to be used only one way, once every four years. If we are building a Mars base or colonizing Mars, any large habitat sent to the planet’s surface should stay there so the colonists can use it for living quarters. Going to great expense to send a habitat to Mars only to return it to Earth empty makes no sense. Mars needs houses.

And honestly, they'd make pretty poor long-term habitats.  The design does not call for any sort of heavy radiation shielding (clear from their mass figures, but also their design drawings), and it's surely not rated to bear such added regolith loads - nor would it  be easy to dump regolith over such a thing.

But, if he's said some other things elsewhere, I'd be very curious to hear them.  :)

Online guckyfan

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Re: Should ITS have a smaller prototype to ease development?
« Reply #57 on: 02/19/2017 01:06 PM »
Sorry I don't collect sources, maybe I should. But he definitely said this, earlier, not in his IAC presentation.

Again, this is not a contradiction to his goal of returning the ships to earth for reuse.

Re radiaton, true that an ITS is not the best possible solution for that. They could use barrels or water bags to produce some barrier, if they think it is needed. Piling regolith on top is not a solution with ITS:

Offline DigitalMan

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Re: Should ITS have a smaller prototype to ease development?
« Reply #58 on: 02/19/2017 02:09 PM »
Where did you see something stating that ITS would be used as a habitat?

Elon Musk had said this before. It makes all kind of sense too. We must always differentiate between the long term intended use, that is return after refuelling and specific mission requirements. The first crew arrives and there is no other habitat than the ITS at that time. ITS is plenty big for a crew of 12 to 18. There is likely also no fuel for an immediate return of the ITS.

So they get there, live in the ITS until they have set up fuel ISRU and possibly a habitat. Later missions would arrive and there is a habitat waiting for them and fuel in the tanks. They disembark, unload cargo and the ship goes back. Will they even have a ship on standby? I doubt it.

I'm trying to find anywhere that he actually said that.  Do you perchance have a link?  What I have is:

https://www.youtube.com/watch?v=H7Uyfqi_TE8?t=801

Re, local propellant production: "Again, if we didn't do this, it would have at least a half order of magnitude increase in the cost of a trip, so 500% increase in the cost of a trip. And it would be pretty absurd to try to build a city on Mars if your spaceships just kept on staying on Mars and not going back to Earth. You would have this, like, massive graveyard of ships.  You would have to, like, do something with them. So it really wouldn't make sense to leave your spaceships on Mars, you really want to build a propellant plant on Mars and send the ships back."

To be fair, this could be interpreted through the lens of "eventually".  There still is the question of what to do in the beginning - whether a propellant plant and tanks would be delivered by Red Dragon, or whether you have to have one ITS sitting around acting as a refuelling tank, with its payload being a propellant plant.  But that describes only a very small number of ships, and still says nothing about using ITS ships as habitats.  I know Zubrin at the very least hasn't interpreted Musk's statements as meaning using the spaceships as habitats - he published an editorial criticizing Musk for that purpose:

http://www.thenewatlantis.com/publications/colonizing-mars

Quote
7. The sending of a large habitat on a roundtrip from Earth to Mars and back. This, too, is a very bad idea, because the habitat will get to be used only one way, once every four years. If we are building a Mars base or colonizing Mars, any large habitat sent to the planet’s surface should stay there so the colonists can use it for living quarters. Going to great expense to send a habitat to Mars only to return it to Earth empty makes no sense. Mars needs houses.

And honestly, they'd make pretty poor long-term habitats.  The design does not call for any sort of heavy radiation shielding (clear from their mass figures, but also their design drawings), and it's surely not rated to bear such added regolith loads - nor would it  be easy to dump regolith over such a thing.

But, if he's said some other things elsewhere, I'd be very curious to hear them.  :)

My recollection is he said it afterwards I think in the 2nd Q+A from Reddit.  He definitely said it, also that the 2nd landing with crew would complete the propellant plant.

Offline gin455res

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Re: Should ITS have a smaller prototype to ease development?
« Reply #59 on: 02/19/2017 07:25 PM »
Interesting mix of responses so far in this thread.  In addition to the voice of Lars-slayer-of-Trolls I notice 3 opinions come up regularly from differing people:

1) Make a smaller ITS for quicker development
2) Make full-scale ITS to avoid complicating development
3) Potential use of ITS as a Martian habitat

The first two are actually equal in merit; a smaller ship might be easier to build, but scaling it up later might generate development problems.  One lesson the STS/shuttle taught us: implementing (significant) vehicle improvements are nearly impossible to do while on a budget, which NASA is likely to be tight on for the foreseeable future.  In the case of the SLS, especially if competition from Blue Origin and SpaceX emerge, it may advance no further than block 1B or forced to settle for a maximum liftoff mass less than the 130 mt intended for 2.  My personal opinion on the matter of a mini-ITS: miniaturize the spaceship/payload component but fly the booster itself at full-scale; that way SpaceX has the workhorse at full strength.

Using the ITS spaceship as a habitat is an interesting thought.  Drawing on Mars Direct for comparison, it's meant to be more like a giant ERV rather than a Hab.  However, especially at full scale, the spaceship may as well be a luxury yacht given it's bigger than the total module volume of the ISS.  All the same, it's a ship not a hotel.

These questions ought to be given to Elon Musk directly if possible.  ITS is his baby, and I'm sure his engineers are trying to prepare its delivery.

How about a merlin-based booster (ITS-lite) with 42 Merlins on the bottom?
« Last Edit: 02/19/2017 07:26 PM by gin455res »

Offline RonM

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Re: Should ITS have a smaller prototype to ease development?
« Reply #60 on: 02/19/2017 10:17 PM »
Give it up already. No HSF craft ever had a "mini me", no one ever will.  ::)

There have been scaled prototypes such as the DC-X and X-33 for proof of concept. A prototype might be a good idea instead of dropping billions into the largest rocket ever made. Probably won't happen because Musk is impatient. He wants to go to Mars and doesn't want to waste time, ending up too old to go.

I wish SpaceX success and hope ITS works as planned, but there is a chance this design won't work. Remember Lockheed was confident about the X-33 and it failed before having a test flight.

Online guckyfan

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Re: Should ITS have a smaller prototype to ease development?
« Reply #61 on: 02/20/2017 04:46 AM »
I see smaller test bed vehicles as likely. Calling them subscale prototypes, I don't know if this would be the right description. Smaller versions that initially fly to Mars, I see no way of that happening. Too expensive and too time consuming.

If the smaller vehicle has a development path to something smaller serving the satellite launch market that is fine. Quite possible, but that would be something else than a subscale precursor entirely. It would likely happen parallel, probably later than ITS.

Offline Space Ghost 1962

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Re: Should ITS have a smaller prototype to ease development?
« Reply #62 on: 02/20/2017 06:21 AM »
Give it up already. No HSF craft ever had a "mini me", no one ever will.  ::)

There have been scaled prototypes such as the DC-X and X-33 for proof of concept.

Sure, and I also made small aircraft/rockets as a boy. Not HSF. Enormously costly and time consuming.

Quote
A prototype might be a good idea instead of dropping billions into the largest rocket ever made. Probably won't happen because Musk is impatient. He wants to go to Mars and doesn't want to waste time, ending up too old to go.

Perhaps he might know something. Just maybe.

Quote
I wish SpaceX success and hope ITS works as planned, but there is a chance this design won't work. Remember Lockheed was confident about the X-33 and it failed before having a test flight.

Sure, they did. They told NASA what it would take to fly. Aluminum tanks. NASA said "Tanks, but not thanks" ;)

Smaller versions that initially fly to Mars, I see no way of that happening. Too expensive and too time consuming.
Absolutely. Nothing "useful" as a LV/SC.

Quote
If the smaller vehicle has a development path to something smaller serving the satellite launch market that is fine. Quite possible, but that would be something else than a subscale precursor entirely. It would likely happen parallel, probably later than ITS.
Yes.

The most useful non-ITS Raptor vehicle would be a Raptor US not unlike ACES encapsulated in the lengthened fairing. Perhaps reusable. Musk says he's tempted, but he doesn't want the distraction. If a well paying gig for a much, much, much lower cost to develop, retiring the largest single risk earliest (Raptor at altitude, restarts, duration, recovery, ... landing) ... what in the world makes anyone think he'd do a lesser choice.

ITS itself is an enormous gamble. Like F9/Dragon. You'll note he skipped F5 too. And dropped F1e altogether. Distractions.

F9/FH are good enough for today's requirements. ITS has nothing to do with the market - zip zero nada. ITS "mini me" too. F9RUS would but Musk says that's not enough. Maybe post-ITS, ITS would schlep payloads when not doing its designed "duty", to shift some operating expense. But not what ITS designed for clearly.

Give. It. Up.
« Last Edit: 02/20/2017 06:22 AM by Space Ghost 1962 »

Online QuantumG

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Re: Should ITS have a smaller prototype to ease development?
« Reply #63 on: 02/20/2017 06:33 AM »
Maybe just a Falcon with two liquid propellant side boosters. How long could that take?

When someone is wishing for a pony, there's little to be gained by suggesting a unicorn would be ever better.. ya know, unless it's sarcasm.

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Re: Should ITS have a smaller prototype to ease development?
« Reply #64 on: 02/20/2017 09:33 AM »
Maybe just a Falcon with two liquid propellant side boosters. How long could that take?

Until it is really needed?

Offline Rei

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Re: Should ITS have a smaller prototype to ease development?
« Reply #65 on: 02/20/2017 12:07 PM »
How about a merlin-based booster (ITS-lite) with 42 Merlins on the bottom?

I'd more expect to see the inverse - a Falcon-like methalox vehicle with Raptors.  I expect them to have a lot more trouble with the dual issues of "composites" and "scale" than with the high pressures, new fuel, and full-flow staged combustion.  So maturing the latter on a more humble-sized, aluminum-bodied vehicle while they work on the former would be logical.

Indeed, the more I think about this the more it makes sense.  Because they could also mature their own propellant plant at the same time - starting out by filling with standard pipeline methane and LOX from big steel tanks, and steadily switch to filling with Sabatier methane from electrolysis hydrogen with "permafrost brine" as the water source and "impure dusty CO2" as the CO2 source, with all fluids stored in / produced by flight-intent systems.  They'd need an outer partial-vacuum tank to mimic the low pressure Martian environment and radiative balance, but otherwise...  If they wanted to take it all the way, they could build an ice rink for harvesting the water from, constantly casting new permafrost to be harvested as the old stuff is ripped up, and the team regularly throwing in new curveballs for their harvester to deal with (varying water content, varying dissolved mineral content, various things mixed in (dusts, clays, gravels, boulders), etc.  Fully close the loop.

They'd be able to demonstrate that they can produce it on bulk scales, with non-ideal feedstocks, in a reliable manner, store it densified, fill, and that Raptor can operate on it.  All fundamental requirements.
« Last Edit: 02/20/2017 12:29 PM by Rei »

Offline Rei

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Re: Should ITS have a smaller prototype to ease development?
« Reply #66 on: 02/20/2017 12:17 PM »
My recollection is he said it afterwards I think in the 2nd Q+A from Reddit.  He definitely said it, also that the 2nd landing with crew would complete the propellant plant.

I think this is what you're referring to?

https://www.reddit.com/r/spacex/comments/590wi9/i_am_elon_musk_ask_me_anything_about_becoming_a/

Quote
We are still far from figuring this out in detail, but the current plan is:
Send Dragon scouting missions, initially just to make sure we know how to land without adding a crater and then to figure out the best way to get water for the CH4/O2 Sabatier Reaction.
Heart of Gold spaceship flies to Mars loaded only with equipment to build the propellant plant.
First crewed mission with equipment to build rudimentary base and complete the propellant plant.
Try to double the number of flights with each Earth-Mars orbital rendezvous, which is every 26 months, until the city can grow by itself.

Emphasis mine.  Nothing about the crew living in ITS.  I guess you can read that into it during "base construction time", but it's clear he doesn't want people living in them any longer than needed.

Also... IMHO.... not too comforting that he doesn't plan to have the propellant plant even finished, let alone have propellant stocks onhand, when the first colonists arrive.  They better well hope that nothing goes wrong that requires an evacuation (not an unlikely event), or all of them will be dead.
« Last Edit: 02/20/2017 12:34 PM by Rei »

Offline robert_d

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Re: Should ITS have a smaller prototype to ease development?
« Reply #67 on: 02/20/2017 01:06 PM »

How about a merlin-based booster (ITS-lite) with 42 Merlins on the bottom?

What risk would you be trying to retire with this? Would you build it with composite tanks? What role would it play in the 2020's?


Offline robert_d

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Re: Should ITS have a smaller prototype to ease development?
« Reply #68 on: 02/20/2017 01:38 PM »
Looking over the ITS plans and comparing them to either Mars Direct or SLS...it's on the verge of insanely ambitious. ...  Would it be easier to build a smaller version of ITS first beforehand or not?  Say something either at 1/2 or 2/3 scaled compared to the full ITS.

I think they could retire a lot of risk with something much smaller. But for several reasons, I think a dual core Falcon 9, maturing to a 4 core, would be required to get enough lift to address the goal that I see as doable without huge investment.

That goal is a single full sized Raptor powered reusable carbon composite second stage with some sort of reusable fairing system. Was it Elon Musk or Gwynne Shotwell that said that they want to reuse but don't want to have them land in the water? That means an air capture or maybe something more wild like small wings and engine to try and fly them back. In any case it will add weight. 

The dual core could support an elliptical cross section second stage supporting an elliptical cross section fairing of something like 8 x 5.5 meters. I could imagine a three section fairing where the two large sections would separate and return as they are planning now, with a small third section staying with the stage and payload. This section would act as the  leading edge upon re-entry.

This idea would not require huge heavy new payloads, just something like a lunar lander or maybe Europa mission class payload to justify development. I think lunar development with 1 lunar mission every 26 months in support of 1 SLS launch and 1 Mars mission at that launch window might be enough for NASA to consider contributing to development cost. Especially if SLS got cancelled altogether. By the way 2 dual core Falcon 9's would be nearly perfect SRB replacements for SLS.

If this reusable technology can be demonstrated at this scale, THEN I could see going on to a full scale ITS. It will need tremendous ground support development as has been noted before. Though I still don't see a Mars colony developing for at least 50 - 75 years.
« Last Edit: 02/20/2017 01:44 PM by robert_d »

Offline envy887

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Re: Should ITS have a smaller prototype to ease development?
« Reply #69 on: 02/20/2017 01:45 PM »
Looking over the ITS plans and comparing them to either Mars Direct or SLS...it's on the verge of insanely ambitious. ...  Would it be easier to build a smaller version of ITS first beforehand or not?  Say something either at 1/2 or 2/3 scaled compared to the full ITS.

I think they could retire a lot of risk with something much smaller. But for several reasons, I think a dual core Falcon 9, maturing to a 4 core, would be required to get enough lift to address the goal that I see as doable without huge investment.

That goal is a single full sized Raptor powered reusable carbon composite second stage with some sort of reusable fairing system. Was it Elon Musk or Gwynne Shotwell that said that they want to reuse but don't want to have them land in the water? That means an air capture or maybe something more wild like small wings and engine to try and fly them back. In any case it will add weight. 

The dual core could support an elliptical cross section second stage supporting an elliptical cross section fairing of something like 8 x 5.5 meters. I could imagine a three section fairing where the two large sections would separate and return as they are planning now, with a small third section staying with the stage and payload. This section would act as the  leading edge upon re-entry.

This idea would not require huge heavy new payloads, just something like a lunar lander or maybe Europa mission class payload to justify development. I think lunar development with 1 lunar mission every 26 months in support of 1 SLS launch and 1 Mars mission at that launch window might be enough for NASA to consider contributing to development cost.

If this reusable technology can be demonstrated at this scale, THEN I could see going on to a full scale ITS. It will need tremendous ground support development as has been noted before. Though I still don't see a Mars colony developing for at least 50 - 75 years.

Why would you launch a reuseable spacecraft/entry vehicle in a fairing? It has to take aero loads on return anyway.

And there is absolutely no reason to develop a multi-core Falcon anything other than Heavy. If you can't do it on Heavy it's not worth doing.

Offline DigitalMan

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Re: Should ITS have a smaller prototype to ease development?
« Reply #70 on: 02/20/2017 02:06 PM »
My recollection is he said it afterwards I think in the 2nd Q+A from Reddit.  He definitely said it, also that the 2nd landing with crew would complete the propellant plant.

I think this is what you're referring to?

https://www.reddit.com/r/spacex/comments/590wi9/i_am_elon_musk_ask_me_anything_about_becoming_a/

Quote
We are still far from figuring this out in detail, but the current plan is:
Send Dragon scouting missions, initially just to make sure we know how to land without adding a crater and then to figure out the best way to get water for the CH4/O2 Sabatier Reaction.
Heart of Gold spaceship flies to Mars loaded only with equipment to build the propellant plant.
First crewed mission with equipment to build rudimentary base and complete the propellant plant.
Try to double the number of flights with each Earth-Mars orbital rendezvous, which is every 26 months, until the city can grow by itself.

Emphasis mine.  Nothing about the crew living in ITS.  I guess you can read that into it during "base construction time", but it's clear he doesn't want people living in them any longer than needed.

Also... IMHO.... not too comforting that he doesn't plan to have the propellant plant even finished, let alone have propellant stocks onhand, when the first colonists arrive.  They better well hope that nothing goes wrong that requires an evacuation (not an unlikely event), or all of them will be dead.

No, that is not it. He was specific.  I have a lot to do today I probably will not have time to look for it .

Offline gospacex

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Re: Should ITS have a smaller prototype to ease development?
« Reply #71 on: 02/20/2017 02:14 PM »
With rocket development, changing diameter is a big deal - basically, you need to replace all tooling, and often the buildings too.

But stretch is a "much smaller deal".

Thus, "smaller" ITS can be simply a full-diameter, but very squat ITS, significantly below optimum. With all tooling, buildings, pads built to accommodate a much longer rocket later on.

Offline gin455res

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Re: Should ITS have a smaller prototype to ease development?
« Reply #72 on: 02/20/2017 02:15 PM »

How about a merlin-based booster (ITS-lite) with 42 Merlins on the bottom?

What risk would you be trying to retire with this? Would you build it with composite tanks? What role would it play in the 2020's?



Potentially none, but if desired it could be a tank test-bed.

More, the September presentation gave us all a little more freedom to really play with scale and investigate the benefits that it might offer. Elon clearly has.

It could just be a way of capitalising on the Merlin fully.  One large booster only needs one avionics package.  Return to launch site is pretty much proven now, perhaps road transportability is less important?

An upper*-stage with  4 vacuum merlins and a central sea-level merlin (potentially allowing complete reusability). Cost to orbit?

Might squeeze New Glenn and SLS.


[Later, fly a Raptor-based upper-stage with 2 vacuum raptors and a central sea-level raptor


- what is the minimum number of engines needed to mix sea-level and vacuum engines on an upper stage and enable vertical landing; 3,4,5?]?

*Perhaps this might optimise best as a 2nd stage of a 3-stage system.

Offline robert_d

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Re: Should ITS have a smaller prototype to ease development?
« Reply #73 on: 02/21/2017 02:30 AM »


Why would you launch a reuseable spacecraft/entry vehicle in a fairing? It has to take aero loads on return anyway.

That's not what I meant. I meant that the Raptor powered second stage would be reusable. The payloads would be traditional Moon bound or Mars bound spacecraft or segments of larger vehicles. But Raptor, Composite tanks and TPS could all be validated for multiple uses. 

Quote
And there is absolutely no reason to develop a multi-core Falcon anything other than Heavy. If you can't do it on Heavy it's not worth doing.
The reason is the larger fairing, larger payload and testing proof-of-concept reusable 2nd stage powered by a full sized Raptor.   
Today they have Falcon Heavy with a more limited fairing size and throw-away second stage. For just one core more (the two center cores stay attached and land as a unit) They would have the margins to add weight to the fairings and landing fuel for the second stage. 
« Last Edit: 02/21/2017 02:37 AM by robert_d »

Offline redliox

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Re: Should ITS have a smaller prototype to ease development?
« Reply #74 on: 02/21/2017 02:31 AM »
Someone double-check my figures to be certain; however I think for a smaller mission this could suffice to get the ship to Mars even without the tanker Elon wants in the full version.

Not suggesting there is anything wrong with your ΔV calculations, but when you talk about a scale model, that refers to a linear dimension, not to mass. What you are describing is roughly a 0.8 scale model of the ITS.

Elaborate on scale models.  I'm curious is there's an optimal scale that is best for testing, not to mention whether it's better to scale by volume or by mass.
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Offline Lars-J

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Re: Should ITS have a smaller prototype to ease development?
« Reply #75 on: 02/21/2017 03:23 AM »
Someone double-check my figures to be certain; however I think for a smaller mission this could suffice to get the ship to Mars even without the tanker Elon wants in the full version.

Not suggesting there is anything wrong with your ΔV calculations, but when you talk about a scale model, that refers to a linear dimension, not to mass. What you are describing is roughly a 0.8 scale model of the ITS.

Elaborate on scale models.  I'm curious is there's an optimal scale that is best for testing, not to mention whether it's better to scale by volume or by mass.

Keep in mind that scale models are usually (?) done as proof of concepts. Some of the more successful scale models (DC-X) focus more on specific technologies. Scale models that try to do to much - replicate everything at a smaller scale - like X-33 can run into problems.

So the question is... what specific kinds of challenge technologies do you hope to test and verify using a "small ITS"? And is verifying those really that much more cost-effective using a smaller scale?

I'll start by pointing out three things I see as big challenges:
- ITS reentry shape (scale changes mass properties, for example going from Apollo to Orion was more difficult and costly than imagined *despite* same shape)
- ITS TPS (similar concern as above, scale affects mass and heat loading)
- structural composite cryogenic tanks (this testing can be done all on the ground, no smaller vehicle needed)

I think arguing for a smaller final ITS system because it would be more affordable is one argument that I might agree with. But I don't think creating a smaller pathfinder system is worth it.

Offline MikeAtkinson

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Re: Should ITS have a smaller prototype to ease development?
« Reply #76 on: 02/21/2017 08:53 AM »
An alternative would be to have a full size (dimensions) ITS prototype, but at lower performance.

So lower numbers of lower thrust Raptor on the booster. Only part fill the tanks. Aim for 50 tonnes of payload, rather than 300 tonnes.

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Re: Should ITS have a smaller prototype to ease development?
« Reply #77 on: 02/21/2017 10:11 AM »
Elaborate on scale models.  I'm curious is there's an optimal scale that is best for testing, not to mention whether it's better to scale by volume or by mass.

The engineering choice to model a design is not bound by any single optimal scale. There are many reasons to use, and not to use scale models.

SpaceX has produced scale models of some of their designs as proofs of concept. Falcon 1 was roughly 1/3 the scale of Falcon 9, but they never produced the 1/2 scale Falcon 5 version, and history shows it wasn't necessary for them to test at that scale. 

The Kestrel and Merlin 1A engines in the Falcon 1 were both kerolox, although the Kestrel was pressure fed, and the Merlin has a turbo pump. The Kestrel was about 1/3 the scale of the Merlin 1A, and helped its development. However the Merlin engine was full scale in all three Falcon designs, it was only necessary to vary their number.

More recently, a deliberately scaled model of the Raptor engine was produced for testing, and has so far been successful. However, the test carbon fuel tank was almost full size for the ITS spaceship, and failed in an early test. With the benefit of hindsight, perhaps a smaller scale model would have been a cheaper first iteration?

ArticleSizeMassScale
Falcon 121.3m38.5mT1:3
Falcon 529.0m155.0mT1:2
Falcon 9 1.054.9m333.4mT1:1
Kestrel1.2m52kg1:3
Merlin 1A3.6m470kg1:1
Raptor scaled0.9m?1:2
Raptor 501.8m?1:1
« Last Edit: 02/21/2017 10:19 AM by OneSpeed »

Offline Lars-J

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Re: Should ITS have a smaller prototype to ease development?
« Reply #78 on: 02/21/2017 05:31 PM »
Elaborate on scale models.  I'm curious is there's an optimal scale that is best for testing, not to mention whether it's better to scale by volume or by mass.

The engineering choice to model a design is not bound by any single optimal scale. There are many reasons to use, and not to use scale models.

SpaceX has produced scale models of some of their designs as proofs of concept. Falcon 1 was roughly 1/3 the scale of Falcon 9, but they never produced the 1/2 scale Falcon 5 version, and history shows it wasn't necessary for them to test at that scale. 

It would be incorrect to label Falcon 1 and Falcon 5 as scale models for Falcon 9. Falcon 1 was simply the first orbital launch vehicle they could build. Falcon 5 would have had the same stage diameter as Falcon 9.

Offline Lobo

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Re: Should ITS have a smaller prototype to ease development?
« Reply #79 on: 02/21/2017 06:25 PM »
When I was a kid watching Apollo 11, and 2001: A Space Odyssey, if you asked me back then that in 50 years would Musk's ITS was too large, I would have expected that kind of scale. But I also expected that there would have been moon bases with commercial flights flying there, and man would be on Mars before the end of the 20th century. So back then, looking 50 years ahead, this would make perfect sense. Somehow, we lost the future that looked so promising back then. What ITS does is give us back the future.

HOWEVER

The scale is ludicrous, and there is no business case for it. I understand Musk's rational, to have the economics to go to Mars for less than a quarter million dollars per passenger. But let's put our business hats on. He should build a 1/4 scale lander, focus on orbital space tourism, lunar tourism and even a true space shuttle for space deliveries. The rocket is too large for just about any commercial or government client. Maintain a cash flow while perfecting the technology and let the systems mature. Sure, there will be duplicate costs by building two systems instead of one, but a two pronged approach won't bankrupt him. It reminds me of Howard Hughes' Spruce Goose. Build it and he can only afford one flight with it.

It's scale is huge, sure.
But we need to remember that ITS would be a paradigm shift.  And we have to stand on our heads a bit to account for that. 
It's huge...but fully reusable...with not only booster recovery and reuse, but "return to launch site" recovery and reuse.  Right now  F9-FT is technically much larger than necessary for what it needs to do.  But it's grown larger and more powerful as SpaceX has explored booster reusability.   It uses that extra performance to land the booster on a barge or back on land, depending on payload requirements.  But they've squeezed about as much performance out of the hardare and technology as they can.  If SpaceX could redesign Falcon 9 from scratch today, knowing everything they know now, and if road transportation wasn't a consideration, I think it'd be even larger...and probably methane, which would make it even larger yet as CH4 is less dense than RP-1.    That way they could launch all the commercial sats to GTO and still RTLS the booster...which is ideal.   They may even go larger yet, and get up into EELV-heavy payload range and RTLS the booster, but without the need for the complex tri-core booster.  That way they have just one common single-stick booster for pretty much every potential payload, and it could return the booster to the launch site for all of them.  Now, if you added a reusable upper stage to that, then your scale goes up again to account for that.  But while very oversized, it could still be very economical.
ITS is just really an extension of that.
 
It wouldn't be unlike the Space Shuttle.  STS was of a Saturn V scale of LV, yet it was only capable of launching EELV class payloads to BLEO (with use of an 2nd stage) or EELV-heavy payloads to LEO.  It was about as big and powerful as Saturn V, but could only put about 1/6 the payload into LEO.  And originally, that was deemed acceptable by NASA and USAF.  So why would it be so different for ITS?  Except [hopefully] ITS would correct many of the issues with STS which kept it from realizing it's original cost and time saving ambitions.

Besides, if there were a new lunar program for NASA, that may be a good first business case for it, if SLS and Orion were to be cancelled at some point.



Offline Lobo

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Re: Should ITS have a smaller prototype to ease development?
« Reply #80 on: 02/21/2017 06:53 PM »
Both Musk and many people here think it would be wasted effort. I think it could have the advantage of building something to use as a fully reusable workhorse launcher (replacing the F9), especially since SpaceX is developing a scaled down Raptor engine contracted by USAF anyway.


Yea, this was discussed on a similar thread.

Myself, I don't think there's a case for a mini-ITS.  For the same reason there was no real need for a "Saturn III" between the Saturn 1B and Saturn V.  For going to LEO, the Saturn 1B was fine.  For sending humans BLEO, you need as much capability as you can get, so you wanted the Saturn V (or even bigger, if it has been feasible).  But not much need in between.  Not even as an interim stepping stone.  NASA went right from the Saturn 1 to Saturn V. 
It's similar for SpaceX.  They already have their "Saturn 1" in Falcon, and now they want as much capability as they can possible get in ITS.  No need to have an intermediate LV.  It is nice to work up in scale, but it also costs a lot to have an entirely new and different intermediate LV to pay for development and testing.  Go do what you really -need- and then focus your funds and efforts there.  Rather than an essentially "dead end" LV.

NOTE:  The one scenario it could make sense, is as a fully reusable Falcon replacement.  Something that would handle all commercial and government payloads fully reusably in a single stick LV.  Something that could launch basically a D4H payload to GTO, have the booster RTLS, and have the upper stage deploy the payload in GTO, and then have enough propellants to deorbit itself form GTO, and land back at the launch site. 
The problem with this, is they already have Falcon in place and all of it's development paid for.  It's probably not the LV they'd be flying if they could do a clean sheet design knowing everything they know right now, but as the bumper sticker says, "Don't laugh, it's paid for".  ;-)

They have launch pads being built for Falcon, and infrastructure in place for it.  And a mini-ITS to replace it would have to be built somewhere near the water or at the launch site like ITS since it couldn't be transported by road...which means starting all over again after they've just barely got their final version of Falcon flying, and FH soon to be flying.  So I don't see them scrapping all of that and starting over, just to replicate the capabilities F9/FH will already have...just with an expendable upper stage rather than a reusable one.


Offline Lobo

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Re: Should ITS have a smaller prototype to ease development?
« Reply #81 on: 02/21/2017 07:12 PM »
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

I like that approach, a lot. As far as I remember, a completely new suggestion that makes a lot of sense to me. But I am not an expert.

Yes, I've discussed that before with some folks, I think on the Mini-BFR thread.
The ITS Spacecraft is really it's own SSTO rocket. It will have to get itself off the surface of Mars and get itself all the way back to Earth and land.  It needs help on Earth to get itself all the way over to Mars because of the deeper gravity well, with a usable payload, but without much (or any) payload, it could probably get itself up to LEO on it's own...with some engine modifications as it can't take off with those vacuum nozzles.
And with some tweaking later, it could probably get itself plus some usable payload to LEO.  In which case, it could possibly replace Falcon at some point down the road.  And given how it will be designed to operate on the surface of Mars, it could possibly operate on some large flat pad, or with a simple launch mount, like Redstone or the Early Saturn 1's.  Although they will probably want to direct the thrust in some manner rather than have it go in all directions... and need some sound supression and other things that won't be an issue on Mars.  But you get the idea.  It could really change the whole idea of pad ops to something a little more like an airport.  If not going to Mars, these spacecraft would launch and land themselves in one big flat complex to handle the typical comsat payload or crew shuttle duties to a space station.  And it'd be just a different configuration of the hardware already built for the Mars program.

Offline RonM

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Re: Should ITS have a smaller prototype to ease development?
« Reply #82 on: 02/21/2017 07:15 PM »
Both Musk and many people here think it would be wasted effort. I think it could have the advantage of building something to use as a fully reusable workhorse launcher (replacing the F9), especially since SpaceX is developing a scaled down Raptor engine contracted by USAF anyway.


Yea, this was discussed on a similar thread.

Myself, I don't think there's a case for a mini-ITS.  For the same reason there was no real need for a "Saturn III" between the Saturn 1B and Saturn V.  For going to LEO, the Saturn 1B was fine.  For sending humans BLEO, you need as much capability as you can get, so you wanted the Saturn V (or even bigger, if it has been feasible).  But not much need in between.  Not even as an interim stepping stone.  NASA went right from the Saturn 1 to Saturn V. 
It's similar for SpaceX.  They already have their "Saturn 1" in Falcon, and now they want as much capability as they can possible get in ITS.  No need to have an intermediate LV.  It is nice to work up in scale, but it also costs a lot to have an entirely new and different intermediate LV to pay for development and testing.  Go do what you really -need- and then focus your funds and efforts there.  Rather than an essentially "dead end" LV.

NOTE:  The one scenario it could make sense, is as a fully reusable Falcon replacement.  Something that would handle all commercial and government payloads fully reusably in a single stick LV.  Something that could launch basically a D4H payload to GTO, have the booster RTLS, and have the upper stage deploy the payload in GTO, and then have enough propellants to deorbit itself form GTO, and land back at the launch site. 
The problem with this, is they already have Falcon in place and all of it's development paid for.  It's probably not the LV they'd be flying if they could do a clean sheet design knowing everything they know right now, but as the bumper sticker says, "Don't laugh, it's paid for".  ;-)

They have launch pads being built for Falcon, and infrastructure in place for it.  And a mini-ITS to replace it would have to be built somewhere near the water or at the launch site like ITS since it couldn't be transported by road...which means starting all over again after they've just barely got their final version of Falcon flying, and FH soon to be flying.  So I don't see them scrapping all of that and starting over, just to replicate the capabilities F9/FH will already have...just with an expendable upper stage rather than a reusable one.

Good points, but I see a problem with your comparison.

Saturn 1B and Saturn V are similar rockets as in they used similar construction and fuel. ITS will have composite fuel tanks and use methane instead of RP-1, major changes from F9. That's a bigger leap than going from Saturn 1B to Saturn V. But it looks like Elon is comfortable with making that leap.

Offline Lobo

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Re: Should ITS have a smaller prototype to ease development?
« Reply #83 on: 02/21/2017 07:37 PM »

Good points, but I see a problem with your comparison.

Saturn 1B and Saturn V are similar rockets as in they used similar construction and fuel. ITS will have composite fuel tanks and use methane instead of RP-1, major changes from F9. That's a bigger leap than going from Saturn 1B to Saturn V. But it looks like Elon is comfortable with making that leap.

True, but it was just for the sake of demonstration.  ;-)

Actually, the original Saturn 1 and Saturn V is probably more correctly comparative of Falcon 9 and ITS.  They used similar fuels, but really had nothing else in common, until the switched from the S-IV upper stage to the S-IVB, so they then both had that in common.

Regardless, it's certainly a big jump.  Bigger in most ways than the Jump from the Saturn 1 to the Saturn V.  But, it still comes back to "build what you need", and not to mess around with an LV that you don't need.  If funds dry up, then you could be stuck with this mini-ITS that's really not capable of the Mars program that Elan wants, without the funds to build the full ITS in addition.

Offline wannamoonbase

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Re: Should ITS have a smaller prototype to ease development?
« Reply #84 on: 02/21/2017 08:10 PM »
Saturn 1B and Saturn V are similar rockets as in they used similar construction and fuel. ITS will have composite fuel tanks and use methane instead of RP-1, major changes from F9. That's a bigger leap than going from Saturn 1B to Saturn V. But it looks like Elon is comfortable with making that leap.

Or he doesn't have money to do anything else.

A smaller raptor powered vehicle could have the benefit of doing many more RTLS launches than F9 and fully implementing the reuse lessons they are learning and will continue to learn for years to come.

I still think that F9 to ITS, without every flying raptor, is a massive step, maybe too big of a step.
I know they don't need it, but Crossfeed would be super cool.

Offline hkultala

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Re: Should ITS have a smaller prototype to ease development?
« Reply #85 on: 02/21/2017 08:16 PM »
Saturn 1B and Saturn V are similar rockets as in they used similar construction and fuel. ITS will have composite fuel tanks and use methane instead of RP-1, major changes from F9. That's a bigger leap than going from Saturn 1B to Saturn V. But it looks like Elon is comfortable with making that leap.

Saturn IB and Saturn V had quite different first stage tank structures.

But the engine and fuel types were similar, and even same upper stage was used.

Offline gin455res

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Re: Should ITS have a smaller prototype to ease development?
« Reply #86 on: 02/21/2017 08:41 PM »
Both Musk and many people here think it would be wasted effort. I think it could have the advantage of building something to use as a fully reusable workhorse launcher (replacing the F9), especially since SpaceX is developing a scaled down Raptor engine contracted by USAF anyway.


Yea, this was discussed on a similar thread.

Myself, I don't think there's a case for a mini-ITS.  For the same reason there was no real need for a "Saturn III" between the Saturn 1B and Saturn V.  For going to LEO, the Saturn 1B was fine.  For sending humans BLEO, you need as much capability as you can get, so you wanted the Saturn V (or even bigger, if it has been feasible).  But not much need in between.  Not even as an interim stepping stone.  NASA went right from the Saturn 1 to Saturn V. 
It's similar for SpaceX.  They already have their "Saturn 1" in Falcon, and now they want as much capability as they can possible get in ITS.  No need to have an intermediate LV.  It is nice to work up in scale, but it also costs a lot to have an entirely new and different intermediate LV to pay for development and testing.  Go do what you really -need- and then focus your funds and efforts there.  Rather than an essentially "dead end" LV.

NOTE:  The one scenario it could make sense, is as a fully reusable Falcon replacement.  Something that would handle all commercial and government payloads fully reusably in a single stick LV.  Something that could launch basically a D4H payload to GTO, have the booster RTLS, and have the upper stage deploy the payload in GTO, and then have enough propellants to deorbit itself form GTO, and land back at the launch site. 
The problem with this, is they already have Falcon in place and all of it's development paid for.  It's probably not the LV they'd be flying if they could do a clean sheet design knowing everything they know right now, but as the bumper sticker says, "Don't laugh, it's paid for".  ;-)

They have launch pads being built for Falcon, and infrastructure in place for it.  And a mini-ITS to replace it would have to be built somewhere near the water or at the launch site like ITS since it couldn't be transported by road...which means starting all over again after they've just barely got their final version of Falcon flying, and FH soon to be flying.  So I don't see them scrapping all of that and starting over, just to replicate the capabilities F9/FH will already have...just with an expendable upper stage rather than a reusable one.

Good points, but I see a problem with your comparison.

Saturn 1B and Saturn V are similar rockets as in they used similar construction and fuel. ITS will have composite fuel tanks and use methane instead of RP-1, major changes from F9. That's a bigger leap than going from Saturn 1B to Saturn V. But it looks like Elon is comfortable with making that leap.

How long has it taken the Merlin engine to reach it's current level of maturity?


(Maybe a successful and rich SpaceX will have more funds to accelerate Raptor development compared to the historical Merlin development? but Merlin is here and ready right-now-ish - well, assuming block 5 is not a turkey and inherits some of its predecessors' flight-derivable reliability stats. What is the relative timeline, and risks inherent in Raptor compared to block 5?)

By foregoing an intermediate super-heavy merlin-based system are you missing a trick($$). Namely, a window of several years where it may be possible to further slash the cost to orbit; continue to expand the mass and capability of your orbital comms-network, build new markets and value; squeeze competitors; and get on with the initial mars base building without having to wait an extra 3-5?? years for a mature ITS system.

Just because (say) $10? million per person to Mars may not be sustainable long-term, does it mean there mightn't be buyers at levels significantly above Musk's stated goal of $500,000 for a number of years, while ITS becomes operational?

However, the only items an (initially) merlin-based interim system might prototype is TPS and mixed expansion engines (for vertical landing of the upper-stage.) Raptor upper-stages and composites might be optional.


An interim system might act as a lucrative and risk-reducing bridge between falcon heavy and ITS. And the more ITS might move to the right (a clear risk) the more this might hold.

Offline spacenut

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Re: Should ITS have a smaller prototype to ease development?
« Reply #87 on: 02/21/2017 08:53 PM »
The government (NASA), at that time, had unlimited resources, so they could go straight from Saturn I to Saturn V.  SpaceX doesn't have unlimited resources.  That it why I think a step between F9/FH and ITS should be done by them, to utilize existing infrastructures at the Cape, inland waterways and transportation systems.  This would save them costs to build new infrastructures. 

Offline redliox

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Re: Should ITS have a smaller prototype to ease development?
« Reply #88 on: 02/21/2017 09:52 PM »
Keep in mind that scale models are usually (?) done as proof of concepts. Some of the more successful scale models (DC-X) focus more on specific technologies. Scale models that try to do to much - replicate everything at a smaller scale - like X-33 can run into problems.

So the question is... what specific kinds of challenge technologies do you hope to test and verify using a "small ITS"? And is verifying those really that much more cost-effective using a smaller scale?

I'll start by pointing out three things I see as big challenges:
- ITS reentry shape (scale changes mass properties, for example going from Apollo to Orion was more difficult and costly than imagined *despite* same shape)
- ITS TPS (similar concern as above, scale affects mass and heat loading)
- structural composite cryogenic tanks (this testing can be done all on the ground, no smaller vehicle needed)

I think those both would be good concepts to start with.  Beyond those, it would be a matter of seeing how ISRU on Mars could be done which could be part of a different vehicle, like an experiment on a future Red Dragon for one.  Seeing if the vehicle can reach Mars, retain the majority of its fuel (most likely methalox, although hydrolox may be optional [though not nearly as likely]), and survive EDL is the greatest challenge for HSF engineering.  Life-support and ISRU, by comparison, could be largely lab-tested.

I think arguing for a smaller final ITS system because it would be more affordable is one argument that I might agree with. But I don't think creating a smaller pathfinder system is worth it.

Between the crappy experiences of STS and X-33, you have a painful point that can't be denied.  However, the Mars Pathfinder's designs became the basis for MER and MSL; even the Skycrane could be said to be an evolution of the cable that lowered the probe from its solid-fueled backshell.  All the same, I would agree that any precursor/pathfinder vehicle should be as close as possible to the final vehicle, or barring that as affordable as possible with commonality with the final vehicle; i.e. I'd take your advice 75% to heart with 25% boldness.

In the case of this hypothetical mini-ITS, specifically a mini-Interplanetary Spaceship, it should have raptor engines (just fewer of them), be methalox, fly aboard a full-scale ITS booster, and sit inside a shroud identical to the full IPS so only mass would differ from a future larger spaceship.

It's scale is huge, sure.
But we need to remember that ITS would be a paradigm shift.  And we have to stand on our heads a bit to account for that. 
It's huge...but fully reusable...with not only booster recovery and reuse, but "return to launch site" recovery and reuse.  Right now  F9-FT is technically much larger than necessary for what it needs to do.  But it's grown larger and more powerful as SpaceX has explored booster reusability.   It uses that extra performance to land the booster on a barge or back on land, depending on payload requirements.  But they've squeezed about as much performance out of the hardare and technology as they can.  If SpaceX could redesign Falcon 9 from scratch today, knowing everything they know now, and if road transportation wasn't a consideration, I think it'd be even larger...and probably methane, which would make it even larger yet as CH4 is less dense than RP-1.    That way they could launch all the commercial sats to GTO and still RTLS the booster...which is ideal.   They may even go larger yet, and get up into EELV-heavy payload range and RTLS the booster, but without the need for the complex tri-core booster.  That way they have just one common single-stick booster for pretty much every potential payload, and it could return the booster to the launch site for all of them.  Now, if you added a reusable upper stage to that, then your scale goes up again to account for that.  But while very oversized, it could still be very economical.
ITS is just really an extension of that.

Basically the ITS (especially if you're referring to its booster half) is the supreme evolution of Falcon tech eh?

Yes, I've discussed that before with some folks, I think on the Mini-BFR thread.
The ITS Spacecraft is really it's own SSTO rocket. It will have to get itself off the surface of Mars and get itself all the way back to Earth and land.  It needs help on Earth to get itself all the way over to Mars because of the deeper gravity well, with a usable payload, but without much (or any) payload, it could probably get itself up to LEO on it's own...with some engine modifications as it can't take off with those vacuum nozzles.
And with some tweaking later, it could probably get itself plus some usable payload to LEO.  In which case, it could possibly replace Falcon at some point down the road.  And given how it will be designed to operate on the surface of Mars, it could possibly operate on some large flat pad, or with a simple launch mount, like Redstone or the Early Saturn 1's.  Although they will probably want to direct the thrust in some manner rather than have it go in all directions... and need some sound supression and other things that won't be an issue on Mars.  But you get the idea.  It could really change the whole idea of pad ops to something a little more like an airport.  If not going to Mars, these spacecraft would launch and land themselves in one big flat complex to handle the typical comsat payload or crew shuttle duties to a space station.  And it'd be just a different configuration of the hardware already built for the Mars program.

If you're referring to the spaceship half of the ITS, mini or full, I disagree on re-purposing it for use on Earth.  You may as well be asking the Apollo LEM to do likewise.  The furthest the full-scale could go alone would be to LEO, but not to GTO or Luna so its applications would be limited much as the weight of the space shuttle's wings limited its operations.  At Mars it could indeed a SSTO godsend, but it is going to be some time before Martian manufacturing gets setup.

However, if you're talking about the ITS BOOSTER, you have a far better alley to tread.  It's a beautiful example of what a HLV should be.  The SLS, as an example, has more potential than the STS because it has cargo capacity unseen since Saturn's days; it's main limitations are it's Orion's mule and it is very old-school (since, during the Augustine days, it was viewed that the limited reusability of the shuttle was part of its downfall [since then SpaceX has improved on it heavily]).  The ITS booster is a single rocket doing a superior job compared to either Falcon Heavy or SLS, both of which require setups of multiple rockets.  I wouldn't wish to scale down the ITS booster even for simplicity-sake because it (and perhaps whatever Blue Origin can generate) would be the best rocket ever developed in either the 20th or 21st centuries!

So, while this thread is meant to apply towards both the booster and spaceships halves of ITS, IMPO thus far I think any scaling should be done to the spaceship but not the booster.  The booster is going to be used exclusively at Earth so obviously testing it here is easier whereas the conditions the spaceship encounters are literally on another planet.  Outside of rocket fuel explosions, what precautions should be taken would be with the conditions the spaceship and its crew face on Mars, especially EDL.
« Last Edit: 02/21/2017 10:10 PM by redliox »
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Offline Khadgars

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Re: Should ITS have a smaller prototype to ease development?
« Reply #89 on: 02/21/2017 10:21 PM »
Elaborate on scale models.  I'm curious is there's an optimal scale that is best for testing, not to mention whether it's better to scale by volume or by mass.

More recently, a deliberately scaled model of the Raptor engine was produced for testing, and has so far been successful. However, the test carbon fuel tank was almost full size for the ITS spaceship, and failed in an early test. With the benefit of hindsight, perhaps a smaller scale model would have been a cheaper first iteration?


I had not heard about the failed test.  Can you provide any specifics?

Offline envy887

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Re: Should ITS have a smaller prototype to ease development?
« Reply #90 on: 02/21/2017 10:43 PM »
There are pictures of the remains of the tank in the ITS development thread.

Offline redliox

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Re: Should ITS have a smaller prototype to ease development?
« Reply #91 on: 02/21/2017 10:55 PM »
Not suggesting there is anything wrong with your ΔV calculations, but when you talk about a scale model, that refers to a linear dimension, not to mass. What you are describing is roughly a 0.8 scale model of the ITS.

How is that number, 0.8 generated?  I assume it's not merely implying this instance of a mini-ITS is 80% the linear dimensions of a full-ITS.  Same as a 4:5 ratio?  How would that translate to both dimensions and mass?
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Offline Lars-J

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Re: Should ITS have a smaller prototype to ease development?
« Reply #92 on: 02/21/2017 11:24 PM »
Not suggesting there is anything wrong with your ΔV calculations, but when you talk about a scale model, that refers to a linear dimension, not to mass. What you are describing is roughly a 0.8 scale model of the ITS.

How is that number, 0.8 generated?  I assume it's not merely implying this instance of a mini-ITS is 80% the linear dimensions of a full-ITS.  Same as a 4:5 ratio?  How would that translate to both dimensions and mass?

The 0.8 figure presumably comes from how mass scales with linear dimension change.

For example... If you want an ITS that is half the liftoff weight of a full ITS, then the linear scale change is 0.8.  (0.8 ^ 3 = ~0.5) So it is not going to be as much smaller as you might think.

Offline Lobo

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Re: Should ITS have a smaller prototype to ease development?
« Reply #93 on: 02/21/2017 11:57 PM »

Basically the ITS (especially if you're referring to its booster half) is the supreme evolution of Falcon tech eh?

In a sense, yes.  I don't know for sure, but I bet if you sat Musk and SHotwell down and asked them how they would design a clean sheet sat launcher knowing what they know now, I'm guessing they wouldn't draw up Falcon.  They'd draw up a mini-ITS.  A single stick two-stage system that's fully reusable.  They'd have some method of unmanned payload deployment in the upper stage.  It'd be like a smaller unmanned shuttle with perhaps a dorsal payload bay.  It would deploy sats in GTO, and then circle back close to Earth where it could do a deorbit burn, and then land.  It'd be size to handle the largest expected payload (something D4H-class to GTO) and with that it could RTLS both the booster and upper stage.  That'd be a nice slick, simple and efficient system.
I think ITS is that...but they already have invested heavily in Falcon, and it already works pretty well, and it's paid for, so no need to replace it.  But a new heavy launch system for going to Mars doesn't exist yet, and I think it's just what a clean-sheet Falcon would be...but much bigger.



If you're referring to the spaceship half of the ITS, mini or full, I disagree on re-purposing it for use on Earth.  You may as well be asking the Apollo LEM to do likewise.  The furthest the full-scale could go alone would be to LEO, but not to GTO or Luna so its applications would be limited much as the weight of the space shuttle's wings limited its operations.  At Mars it could indeed a SSTO godsend, but it is going to be some time before Martian manufacturing gets setup.

However, if you're talking about the ITS BOOSTER, you have a far better alley to tread.  It's a beautiful example of what a HLV should be.  The SLS, as an example, has more potential than the STS because it has cargo capacity unseen since Saturn's days; it's main limitations are it's Orion's mule and it is very old-school (since, during the Augustine days, it was viewed that the limited reusability of the shuttle was part of its downfall [since then SpaceX has improved on it heavily]).  The ITS booster is a single rocket doing a superior job compared to either Falcon Heavy or SLS, both of which require setups of multiple rockets.  I wouldn't wish to scale down the ITS booster even for simplicity-sake because it (and perhaps whatever Blue Origin can generate) would be the best rocket ever developed in either the 20th or 21st centuries!

So, while this thread is meant to apply towards both the booster and spaceships halves of ITS, IMPO thus far I think any scaling should be done to the spaceship but not the booster.  The booster is going to be used exclusively at Earth so obviously testing it here is easier whereas the conditions the spaceship encounters are literally on another planet.  Outside of rocket fuel explosions, what precautions should be taken would be with the conditions the spaceship and its crew face on Mars, especially EDL.

I address some of this in my PM back to you.  But I disagree.  Using the ITS spaceship to go to LEO would not be like repurposing the LEM, because it's already designed to launch in an atmosphere, and do EDL in an atmosphere.  Specifically Earth's on it's return trip.  Really it'd just need some engine and MPS tweaking so it has sufficient sea level Raptors that can get it off the ground and high enough to shut them down and light say a pair of Vacuum Raptors.  By that time it'd have burned enough fuel that two should be plenty of thrust.  Now, what could it in LEO?  Well, it could deploy sats with kick stages to get them to GTO, or GSO/GEO.  Or the comsats could be designed with enough on board fuel to get themselves form LEO to GSO/GEO.  (most are already designed to get themselves from GTO to GSO/GEO, so it'd be a matter of giving it sufficient propellant capacity.)
It could also serve as a LEO crew taxi to a space station.  Some folks have done some calculations and figured conservatively, with the correct engine config, it should be able to get itself plus around 20mt of payload to LEO.
But this would only be for a theoretical eventual Falcon replacement.  No real need for it other than that.

Not sure what you mean to do with the ITS booster by itself.  Maybe put an expendable (or smaller reusable) upper stage on it for deploying sats, and then it's propellant load can be taylored for each payload.  It wouldn't need near a full prop load for many sats.
But...if you are going to do that, then just put a version of the Spacecraft on top, set up to deploy unmanned sats in GTO, and then return to the launch site.  The stack should be able to get a stripped down spaceship plus a sat of up to ~13mt (I think is D4H's max capacity.) to GTO easily. 
I could see ITS used for this purpose instead of FH, and FH retired.  And F9 handling all the payloads smaller than that (which would be the vast majority).

Offline redliox

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Re: Should ITS have a smaller prototype to ease development?
« Reply #94 on: 02/22/2017 12:08 AM »
Not suggesting there is anything wrong with your ΔV calculations, but when you talk about a scale model, that refers to a linear dimension, not to mass. What you are describing is roughly a 0.8 scale model of the ITS.

How is that number, 0.8 generated?  I assume it's not merely implying this instance of a mini-ITS is 80% the linear dimensions of a full-ITS.  Same as a 4:5 ratio?  How would that translate to both dimensions and mass?

The 0.8 figure presumably comes from how mass scales with linear dimension change.

For example... If you want an ITS that is half the liftoff weight of a full ITS, then the linear scale change is 0.8.  (0.8 ^ 3 = ~0.5) So it is not going to be as much smaller as you might think.

That actually seems like a good thing.  The mini-ITS in this case would be 80% the same dimensions as its big brother and light enough not to require a tanker to get to Mars.  Handling how the mass would double would become the final issue; given how the test tank blew maybe a slightly smaller tank might be a wise start.
« Last Edit: 02/22/2017 12:15 AM by redliox »
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Offline envy887

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Re: Should ITS have a smaller prototype to ease development?
« Reply #95 on: 02/22/2017 12:23 AM »
The mini-ITS in this case would be 80% the same dimensions as its big brother...

I like how "mini" in this case refers to something nearly twice as powerful as Saturn V.

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Re: Should ITS have a smaller prototype to ease development?
« Reply #96 on: 02/22/2017 01:49 AM »
That actually seems like a good thing.  The mini-ITS in this case would be 80% the same dimensions as its big brother and light enough not to require a tanker to get to Mars.  Handling how the mass would double would become the final issue; given how the test tank blew maybe a slightly smaller tank might be a wise start.

Why would the ship not require a tanker to get to Mars?


Online darkenfast

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Re: Should ITS have a smaller prototype to ease development?
« Reply #97 on: 02/22/2017 03:33 AM »
If a scaled ITS is such a good idea, then why haven't the SpaceX design team (who presumably have done all the trades on this), come out with a proposed smaller prototype?

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Re: Should ITS have a smaller prototype to ease development?
« Reply #98 on: 02/22/2017 03:53 AM »
An alternative would be to have a full size (dimensions) ITS prototype, but at lower performance.

So lower numbers of lower thrust Raptor on the booster. Only part fill the tanks. Aim for 50 tonnes of payload, rather than 300 tonnes.

Finally one I kinda like.

One could argue they did this with F9, actually. Over time it's gotten more payload, more thrust, more tank capacity, etc. Without changing the OML or basic size (much).
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Offline redliox

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Re: Should ITS have a smaller prototype to ease development?
« Reply #99 on: 02/22/2017 04:28 AM »
That actually seems like a good thing.  The mini-ITS in this case would be 80% the same dimensions as its big brother and light enough not to require a tanker to get to Mars.  Handling how the mass would double would become the final issue; given how the test tank blew maybe a slightly smaller tank might be a wise start.

Why would the ship not require a tanker to get to Mars?

A smaller-scale spaceship would be lite enough to fly directly to Mars using a full-scale ITS booster and a bit of its own fuel is why.
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Offline Lars-J

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Re: Should ITS have a smaller prototype to ease development?
« Reply #100 on: 02/22/2017 04:30 AM »
That actually seems like a good thing.  The mini-ITS in this case would be 80% the same dimensions as its big brother and light enough not to require a tanker to get to Mars.  Handling how the mass would double would become the final issue; given how the test tank blew maybe a slightly smaller tank might be a wise start.

Why would the ship not require a tanker to get to Mars?

A smaller-scale spaceship would be lite enough to fly directly to Mars using a full-scale ITS booster and a bit of its own fuel is why.

No, that still doesn't make sense. If anything, scaling up improves the dry mass fraction. Making something smaller does not magically give a design more delta-V.

EDIT: I suppose if you fly a smaller ITS spaceship on top of a full-size ITS booster, you can eke out some more delta-V... But the booster still has to make it back to the launch site, so it can't go too far. So you aren't going to get that much more boost from it. And if you still have to make the ITS booster full-size... What are you doing a smaller ITS spaceship for?  ???
« Last Edit: 02/22/2017 05:55 AM by Lars-J »

Offline Robotbeat

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Re: Should ITS have a smaller prototype to ease development?
« Reply #101 on: 02/22/2017 04:31 AM »
Elaborate on scale models.  I'm curious is there's an optimal scale that is best for testing, not to mention whether it's better to scale by volume or by mass.

More recently, a deliberately scaled model of the Raptor engine was produced for testing, and has so far been successful. However, the test carbon fuel tank was almost full size for the ITS spaceship, and failed in an early test. With the benefit of hindsight, perhaps a smaller scale model would have been a cheaper first iteration?


I had not heard about the failed test.  Can you provide any specifics?
"Failed test" isn't appropriate. From what I can tell, they were doing a test-to-failure, i.e. it was going to end up burst one way or another. So it was a successful test since it did burst. :)
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Offline JamesH65

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Re: Should ITS have a smaller prototype to ease development?
« Reply #102 on: 02/22/2017 10:13 AM »
If a scaled ITS is such a good idea, then why haven't the SpaceX design team (who presumably have done all the trades on this), come out with a proposed smaller prototype?

This is one of the few posts on this thread I agree with. Whilst it's all very well trying to out think SpaceX on what they should do with ITS development, SpaceX are the only people with all the facts, and all the rocket engineers.

And they think the current plan (as we see it of course) is the one to go for.

They have F9B5 which is going to cater to the vast majority of launch requirements out, so there seems little point in a smaller variant of ITS/Booster - it's not going to reduce reuse costs much further than they already will have. The Raptor engines are going to be the same whatever, so the dev path is the same for both. The carbon fibre development/issues are going to be the same, it's just a scaling issue.

Seems SpaceX know what they are doing. Who knew?


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Re: Should ITS have a smaller prototype to ease development?
« Reply #103 on: 02/22/2017 11:57 AM »
Why would the ship not require a tanker to get to Mars?

A smaller-scale spaceship would be lite enough to fly directly to Mars using a full-scale ITS booster and a bit of its own fuel is why.

In https://forum.nasaspaceflight.com/index.php?topic=42336.msg1643553#msg1643553 you suggest that a fully fuelled crew spaceship would mass 1950 + 150 = 2100mT. It appears you are assuming no payload, which SpaceX estimate to be between 200 and 450 mT.

Offline Radical_Ignorant

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Re: Should ITS have a smaller prototype to ease development?
« Reply #104 on: 02/22/2017 01:45 PM »
I see smaller test bed vehicles as likely. Calling them subscale prototypes, I don't know if this would be the right description. Smaller versions that initially fly to Mars, I see no way of that happening. Too expensive and too time consuming.

If the smaller vehicle has a development path to something smaller serving the satellite launch market that is fine. Quite possible, but that would be something else than a subscale precursor entirely. It would likely happen parallel, probably later than ITS.

Yah - I was wondering about that for some time. Raptor based architecture seems to be more advanced and efficient than Merlin based (i.e. allowing second stage reuse), so it makes sense to replace Falcons with something like R7, but watching Musk's comments there is no indication that it will happen before ITS.

Seems current line F9 +  F9H is good enough and his goal is clear, so once development of those are finished (along with crew Dragon) he will go for ITS, no need for "distractions". Even if they make sense he is not "gradatim feriocitier" believer, he want to get there ASAP and updates to current services would definitely delay his Mars dreams.

Offline Lobo

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Re: Should ITS have a smaller prototype to ease development?
« Reply #105 on: 02/22/2017 05:12 PM »
The government (NASA), at that time, had unlimited resources, so they could go straight from Saturn I to Saturn V.  SpaceX doesn't have unlimited resources.  That it why I think a step between F9/FH and ITS should be done by them, to utilize existing infrastructures at the Cape, inland waterways and transportation systems.  This would save them costs to build new infrastructures.

So...if SpaceX has more limited funds, how would it be cheaper to develop two new LV's, rather than just one?
An intermediate sized ITS could share the same engines as the full size one, but it would [presumably] have a different diameter, and thus require different tooling (or different molds if doing composite), launch facilities, processing buildings and equipment, and everything associated produced first, and then done again for the full size. 

Going right to the size you want skips all of that.  You measure twice, cut once.  It would expectedly involve a longer learning curve, and more testing due to the larger leap vs. an intermediate sized LV, but I think it's still going to be cheaper and faster than paying for -two- new LV's rather than just one.  Especially when the first new LV really has little business case because it's too small for Musk's Mars goals, and Falcon is already flying their comsat and government payloads.  You'd be essentially duplicating that, and then you still have to make the full size ITS after that.


Offline Lobo

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Re: Should ITS have a smaller prototype to ease development?
« Reply #106 on: 02/22/2017 05:23 PM »
That actually seems like a good thing.  The mini-ITS in this case would be 80% the same dimensions as its big brother and light enough not to require a tanker to get to Mars.  Handling how the mass would double would become the final issue; given how the test tank blew maybe a slightly smaller tank might be a wise start.

Why would the ship not require a tanker to get to Mars?

A smaller-scale spaceship would be lite enough to fly directly to Mars using a full-scale ITS booster and a bit of its own fuel is why.

No, that still doesn't make sense. If anything, scaling up improves the dry mass fraction. Making something smaller does not magically give a design more delta-V.

EDIT: I suppose if you fly a smaller ITS spaceship on top of a full-size ITS booster, you can eke out some more delta-V... But the booster still has to make it back to the launch site, so it can't go too far. So you aren't going to get that much more boost from it. And if you still have to make the ITS booster full-size... What are you doing a smaller ITS spaceship for?  ???

Agreed.

An intermediate ITS has been mentioned seemingly as a smaller scale ITS to test concepts that would be a little easier to develop than the full one.

But if SpaceX wants to do some small scale testing of the ITS concepts, they could just build some test articles based loosely on the Reusable Falcon Upper Stage concept they had awhile back, but in a biconic shape that mimics the ITS Spacecraft.  The Falcon booster can act as an analog for the ITS booster.  The test article could go to LEO, and then test EDL hardware and techniques.  Advanced testing could involve using a FH to launch a test article into a lofted BLEO, like D4H did for the Orion test article.   If could even send it to Mars to practice EDL there.  If FH can get the Falcon upper stage plus a Red Dragon plus a payload to the surface of Mars, it should be able to get a Falcon Upper Stage test article with no Red Dragon or payload on top to the surface of Mars.  Especially since it'd have a better L/D ratio during Mars EDL so it should need less propellant to land than Red Dragon...theoretically.

Such a reusable test article on a Falcon booster should be a good analog for the ITS stack.  And they can practice different ascent and staging profiles, as well as different EDL profiles.  This would be -much- cheaper and faster to do than development an intermediate ITS, and what they learn from it could then go into their ITS development. 

Online guckyfan

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Re: Should ITS have a smaller prototype to ease development?
« Reply #107 on: 02/22/2017 09:28 PM »
I just relized, one can argue they do start small. They start with the ITS according to their timeline. They leave the giant booster for second. The usual way is building the first stage first.

Offline Rei

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Re: Should ITS have a smaller prototype to ease development?
« Reply #108 on: 02/23/2017 12:54 AM »
I just relized, one can argue they do start small. They start with the ITS according to their timeline. They leave the giant booster for second. The usual way is building the first stage first.

Astute observation.  And they've talked (a very small amount) how there will be differing configurations for the spaceship, cargo vs. crew.  So it's not crazy to think that  the spaceship could come first and function as a booster.  It would require an interstage for whatever sat on top of it (F9 or similar?), but the thing is designed for hauling hundreds of tonnes, that would be a serious first stage in its own right.  It has a heat shield and vertical landing capability, so it can return to the pad.  Really very fitting, actually.
« Last Edit: 02/23/2017 12:55 AM by Rei »

Online MP99

So...if SpaceX has more limited funds, how would it be cheaper to develop two new LV's, rather than just one?
An intermediate sized ITS could share the same engines as the full size one, but it would [presumably] have a different diameter, and thus require different tooling (or different molds if doing composite), launch facilities, processing buildings and equipment, and everything associated produced first, and then done again for the full size. 

Going right to the size you want skips all of that.  You measure twice, cut once.  It would expectedly involve a longer learning curve, and more testing due to the larger leap vs. an intermediate sized LV, but I think it's still going to be cheaper and faster than paying for -two- new LV's rather than just one.  Especially when the first new LV really has little business case because it's too small for Musk's Mars goals, and Falcon is already flying their comsat and government payloads.  You'd be essentially duplicating that, and then you still have to make the full size ITS after that.

So, I'm wondering what the impact is on ITS if not doing something on a smaller scale first?

SpaceX's process is to build an initial "good enough" version (an MVP), then spend years optimising mass fractions, engine thrust, cost, usability, etc.

I see no reason why they would do any different for ITS, so what are the implications for that?

1) possibly start with a "battleship" version, which needs optimisation even to get a small crew (with a lot of cargo) landed on Mars. Various tests in LEO (and Lunar orbit?) first.

2) development timescales could be extended, EG just learning how to make autogenous pressurization work well, manage boil off rates, etc, etc, etc. The question is whether those extended timescales and costs get close to the  extra costs of developing something subscale first.

I still think that a Raptor / composite / autogenous / reusable upperstage for Falcon would retire a lot of risk on the way to ITS. Deployment of the commsat constellation is an ideal opportunity to test reusability, since it is many flights to LEO.

Cheers, Martin




Offline TetraOmni

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Re: Should ITS have a smaller prototype to ease development?
« Reply #110 on: 02/23/2017 01:52 PM »
Hi

So id like to put my proposed idea ( their idea maybes ^.^ ) on this amazing forum! Mods delete if im repeating-.-

Firstly:

Musk has stated that he is tempted...but will not be building a reusable upper stage. Needs to be laser focus on ITS and stuff^.^

Secondly:

* They will build a bare-bones ITS spacecraft
* It will be approximately the final dimensions
* It will have no vacuum engines
* It might have three sub-scale raptors...
* The landing legs will be huge
* It will only be able to reach sub-orbit

Thats it for now

Laters

^.^

Offline MikeAtkinson

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Re: Should ITS have a smaller prototype to ease development?
« Reply #111 on: 02/23/2017 02:29 PM »
I still think that a Raptor / composite / autogenous / reusable upperstage for Falcon would retire a lot of risk on the way to ITS. Deployment of the commsat constellation is an ideal opportunity to test reusability, since it is many flights to LEO.

So do I, but it seems that is not the current SpaceX plan.

Online OneSpeed

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Re: Should ITS have a smaller prototype to ease development?
« Reply #112 on: 02/24/2017 11:20 AM »
I still think that a Raptor / composite / autogenous / reusable upperstage for Falcon would retire a lot of risk on the way to ITS. Deployment of the commsat constellation is an ideal opportunity to test reusability, since it is many flights to LEO.

So do I, but it seems that is not the current SpaceX plan.

Perhaps it depends what you make of the 'Next Steps' slide from IAC Mexico?




Offline redliox

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Re: Should ITS have a smaller prototype to ease development?
« Reply #113 on: 02/24/2017 02:18 PM »
Perhaps it depends what you make of the 'Next Steps' slide from IAC Mexico?

It looks like they have plans for the ITS spaceship before the ITS booster indeed.

That video briefly mentioned 'half scale.'  Previously I was nit-picked about scaling so I'd wish to know if they meant half scale by mass or half scale by volume; the former would be close to the final model's dimensions while the later significantly lighter (which would help on flying via FH).
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Offline Lobo

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Re: Should ITS have a smaller prototype to ease development?
« Reply #114 on: 02/24/2017 05:24 PM »
So...if SpaceX has more limited funds, how would it be cheaper to develop two new LV's, rather than just one?
An intermediate sized ITS could share the same engines as the full size one, but it would [presumably] have a different diameter, and thus require different tooling (or different molds if doing composite), launch facilities, processing buildings and equipment, and everything associated produced first, and then done again for the full size. 

Going right to the size you want skips all of that.  You measure twice, cut once.  It would expectedly involve a longer learning curve, and more testing due to the larger leap vs. an intermediate sized LV, but I think it's still going to be cheaper and faster than paying for -two- new LV's rather than just one.  Especially when the first new LV really has little business case because it's too small for Musk's Mars goals, and Falcon is already flying their comsat and government payloads.  You'd be essentially duplicating that, and then you still have to make the full size ITS after that.

So, I'm wondering what the impact is on ITS if not doing something on a smaller scale first?

SpaceX's process is to build an initial "good enough" version (an MVP), then spend years optimising mass fractions, engine thrust, cost, usability, etc.

I see no reason why they would do any different for ITS, so what are the implications for that?

1) possibly start with a "battleship" version, which needs optimisation even to get a small crew (with a lot of cargo) landed on Mars. Various tests in LEO (and Lunar orbit?) first.

2) development timescales could be extended, EG just learning how to make autogenous pressurization work well, manage boil off rates, etc, etc, etc. The question is whether those extended timescales and costs get close to the  extra costs of developing something subscale first.

I still think that a Raptor / composite / autogenous / reusable upperstage for Falcon would retire a lot of risk on the way to ITS. Deployment of the commsat constellation is an ideal opportunity to test reusability, since it is many flights to LEO.

Cheers, Martin

Martin,

See my post upthread a bit.  They can do something smaller scale, without developing a new intermediate sized ITS.
I think a good small scale step would be to develop some reusable biconic test articles that can be launched on F9 to LEO and a higher velocity eliptical orbit like Orion was on D4H for reentry testing).  This would be a good and inexpensive small scale analog for ITS.   A good first step to start testing proof of concept, IMO.  The test article could be based off their earlier reusable Falcon upper stage concepts, but be more truly biconic like the ITS spacecraft would be.
Launching on FH, a block 2 version of this test article could possibly go to Mars and test the ITS Mars EDL profile after it's been tested for ITS Earth EDL profile.

I think they could gain a lot of testing this way with relatively little investment (at least compared to developing and flying a whole new intermediate size ITS).

After they've learned all they can that way, they could work on producing the first full size test articles for the booster and spacecraft.  With some engine/MPS modifications the test artical spacecraft should be able to launch itself to LEO, and then return to launch site to test ascent and EDL profiles.  A test article booster could launch itself with a weight analog, and then test it's RTLS profile.   They could even do the first test article booster launches with fewer engines and a partial propellant load.  So they could work up the full engine compliment in steps.  Then finally they can try the spacecraft test article with it's proper configuration of vacuum engines on top of the full booster for some additional full up testing.

So there's steps to be taken to work up to the full scale, without needing that intermediate ITS development.
« Last Edit: 02/24/2017 05:30 PM by Lobo »

Offline MikeAtkinson

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Re: Should ITS have a smaller prototype to ease development?
« Reply #115 on: 02/24/2017 08:39 PM »
I still think that a Raptor / composite / autogenous / reusable upperstage for Falcon would retire a lot of risk on the way to ITS. Deployment of the commsat constellation is an ideal opportunity to test reusability, since it is many flights to LEO.

So do I, but it seems that is not the current SpaceX plan.

Perhaps it depends what you make of the 'Next Steps' slide from IAC Mexico?



The above exchange is about a Raptor based Falcon upper stage, a rather different beast than a subscale ITS. It is possible for a F9 + Rator based US to replace FH for the heavier GEO launches and possibly be reusable as well. The differences from a scaled ITS would be a single engine, landing on thrusters not Raptor, probably no payload bay but instead using a fairing and about 120 tonnes of propellant. It is this that I think is unlikely.

SpaceX may do a subscale ITS ship, but half-scale would still be rather big for FH (about 3x the mass of the upper stage). I think that this would be SSTO (or almost so) with little or no payload.  Perhaps they could use a scaled raptor, but getting down to 1/8 the thrust is going not going to be easy. The trick for SpaceX is to make it pay its way, by having customers, as well as acting as a demonstrator. I think this is more likely, but there are lots of potential configurations.

Most likely of all in my opinion is a full size ITS ship, dimension wise) but with lower thrust Raptor and a partial propellant load.

Offline Lars-J

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Re: Should ITS have a smaller prototype to ease development?
« Reply #116 on: 02/24/2017 09:10 PM »
Yes, people don't seem to be grasping the size difference going from F9/FH to ITS. Putting a mini-ITS on a scale that most propose on FH would be like putting a F9 upper stage on a F1 first stage. It is just too big.

Online OneSpeed

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Re: Should ITS have a smaller prototype to ease development?
« Reply #117 on: 02/24/2017 09:28 PM »
Perhaps it depends what you make of the 'Next Steps' slide from IAC Mexico?

It looks like they have plans for the ITS spaceship before the ITS booster indeed.

That video briefly mentioned 'half scale.'  Previously I was nit-picked about scaling so I'd wish to know if they meant half scale by mass or half scale by volume; the former would be close to the final model's dimensions while the later significantly lighter (which would help on flying via FH).

I mean half scale in a single linear dimension. 0.5 ^ 3 = 0.125, so 0.125 of the mass and the volume. As I posted in the video of the simulation, the 18mT ship would have a 37.5mT payload, 244mT of fuel, and could achieve a 300 x 300 km orbit with enough fuel to land the ship. Liftoff thrust gives 1.32 gs of acceleration, close to ideal.

The above exchange is about a Raptor based Falcon upper stage, a rather different beast than a subscale ITS. It is possible for a F9 + Rator based US to replace FH for the heavier GEO launches and possibly be reusable as well. The differences from a scaled ITS would be a single engine, landing on thrusters not Raptor, probably no payload bay but instead using a fairing and about 120 tonnes of propellant. It is this that I think is unlikely.

SpaceX may do a subscale ITS ship, but half-scale would still be rather big for FH (about 3x the mass of the upper stage). I think that this would be SSTO (or almost so) with little or no payload.  Perhaps they could use a scaled raptor, but getting down to 1/8 the thrust is going not going to be easy. The trick for SpaceX is to make it pay its way, by having customers, as well as acting as a demonstrator. I think this is more likely, but there are lots of potential configurations.

Most likely of all in my opinion is a full size ITS ship, dimension wise) but with lower thrust Raptor and a partial propellant load.

The simulation represents a subscale ITS that could also be a Raptor based Falcon upper stage. I've previously tried simulating a half scale ITS with a single engine, but its thrust to weight was very poor, and gravity losses were enormous. I'd suggest it needs a least two Raptor 50s to be efficient, and I agree it would have to land on some vernier thrusters, like the Mini BFS in this sim: https://forum.nasaspaceflight.com/index.php?topic=36508.msg1633432#msg1633432

Offline envy887

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Re: Should ITS have a smaller prototype to ease development?
« Reply #118 on: 02/24/2017 10:35 PM »
Yes, people don't seem to be grasping the size difference going from F9/FH to ITS. Putting a mini-ITS on a scale that most propose on FH would be like putting a F9 upper stage on a F1 first stage. It is just too big.

A version that is 1/6 or 1/8 the mass would work fine on FH. It would be only slightly larger in diameter than the current fairing, but would have much better performance than the current stage.

Offline Lars-J

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Re: Should ITS have a smaller prototype to ease development?
« Reply #119 on: 02/24/2017 11:04 PM »
Yes, people don't seem to be grasping the size difference going from F9/FH to ITS. Putting a mini-ITS on a scale that most propose on FH would be like putting a F9 upper stage on a F1 first stage. It is just too big.

A version that is 1/6 or 1/8 the mass would work fine on FH. It would be only slightly larger in diameter than the current fairing, but would have much better performance than the current stage.

But when you scale something *that* small, it is no longer super helpful beyond verifying the most basic stuff. Scale changes things, it changes how air flows around the vehicle, and it changes how much heat needs to be dissipated, and so on.

Offline Bob Shaw

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Re: Should ITS have a smaller prototype to ease development?
« Reply #120 on: 02/24/2017 11:43 PM »
Yes, people don't seem to be grasping the size difference going from F9/FH to ITS. Putting a mini-ITS on a scale that most propose on FH would be like putting a F9 upper stage on a F1 first stage. It is just too big.

A version that is 1/6 or 1/8 the mass would work fine on FH. It would be only slightly larger in diameter than the current fairing, but would have much better performance than the current stage.

But when you scale something *that* small, it is no longer super helpful beyond verifying the most basic stuff. Scale changes things, it changes how air flows around the vehicle, and it changes how much heat needs to be dissipated, and so on.

The area of a sphere goes goes up as the square of the radius, the volume rises by the cube. Sub-scale models may be of value in terms of technology development, but in areas where basic physics define your spacecraft (like hypersonic retro-propulsion) then the gain is an illusion. A smaller ITS - call it the ITS-SP after the 747-SP - is only of value if it fills a market niche, eg for LEO or Lunar/HEO missions, and it may well be that simply flying a standard ITS half-empty would also fill that niche, and without any unique development or manufacturing costs.

Online OneSpeed

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Re: Should ITS have a smaller prototype to ease development?
« Reply #121 on: 02/25/2017 12:00 AM »
But when you scale something *that* small, it is no longer super helpful beyond verifying the most basic stuff. Scale changes things, it changes how air flows around the vehicle, and it changes how much heat needs to be dissipated, and so on.

That's why engineers use dimensional analysis. There is no reason to suggest that a half scale model is not useful. Wind tunnel tests at much greater differences of scale can be extremely accurate and revealing, especially if the models have dynamic similitude.

Offline Lars-J

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Re: Should ITS have a smaller prototype to ease development?
« Reply #122 on: 02/25/2017 12:13 AM »
But when you scale something *that* small, it is no longer super helpful beyond verifying the most basic stuff. Scale changes things, it changes how air flows around the vehicle, and it changes how much heat needs to be dissipated, and so on.

That's why engineers use dimensional analysis. There is no reason to suggest that a half scale model is not useful. Wind tunnel tests at much greater differences of scale can be extremely accurate and revealing, especially if the models have dynamic similitude.

Of course it is useful. You *will* learn things, but the question is if what you learn from it is worth the added cost, or if it could be learned some other way in a more cost-effective way.
« Last Edit: 02/25/2017 12:14 AM by Lars-J »

Offline corneliussulla

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Re: Should ITS have a smaller prototype to ease development?
« Reply #123 on: 02/25/2017 07:41 AM »
I think there may be no other option for him than to develop a mini ITS architecture. Currently all his revenue comes from being the most cost effective way of getting into LEO and other earth orbits. However Bezos is building what could evolve into a fully reusable system to get into similar orbits based on a raptor like engine. To stop Bezos eating his lunch I would think he needs to look at development of a raptor powered F9 replacement with a reusable upper stage. He could use the falcon heavy with reusable upper stage but hard to see how that would be competitive against Bezos single stick approach

Something similar in shape to ITS would make sense. It could have a cargo and manned version and would be capable of moon missions etc if it's used semi permanent ITS tankers in orbit. Cargo version would be first to meet commercial requirements. But down the track a crewed version would also have much greater crew capacity than the dragon2 if such a requirement was to evolve.

Offline envy887

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Re: Should ITS have a smaller prototype to ease development?
« Reply #124 on: 02/25/2017 04:33 PM »
Yes, people don't seem to be grasping the size difference going from F9/FH to ITS. Putting a mini-ITS on a scale that most propose on FH would be like putting a F9 upper stage on a F1 first stage. It is just too big.

A version that is 1/6 or 1/8 the mass would work fine on FH. It would be only slightly larger in diameter than the current fairing, but would have much better performance than the current stage.

But when you scale something *that* small, it is no longer super helpful beyond verifying the most basic stuff. Scale changes things, it changes how air flows around the vehicle, and it changes how much heat needs to be dissipated, and so on.

Basic stuff like methalox storage and transfer on orbit? Raptor Vac coast and restart?

But the main advantage would be putting similar payload to a better GTO orbit than Ariane 5, with a fully reusable system. And beating DIVH payload to direct GEO insertion if fully expended. Falcon Heavy doesn't have either of those capabilities now, and both could be worthwhile in the current market.

Offline hkultala

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Re: Should ITS have a smaller prototype to ease development?
« Reply #125 on: 02/25/2017 04:51 PM »
I think there may be no other option for him than to develop a mini ITS architecture. Currently all his revenue comes from being the most cost effective way of getting into LEO and other earth orbits. However Bezos is building what could evolve into a fully reusable system to get into similar orbits based on a raptor like engine. To stop Bezos eating his lunch I would think he needs to look at development of a raptor powered F9 replacement with a reusable upper stage. He could use the falcon heavy with reusable upper stage but hard to see how that would be competitive against Bezos single stick approach

New glenn will have only first stage reusable, both second and third stages are expendable.

And it cannot easily and quickly evolve into "fully reusable system".

For example, they do not have practical engines that could land those stages. Second stage is too light to land with one BE-4, and it would be impractical to have multiple fuel types for some smaller engine. And third stage is too light to land with on BE-3.

Offline GWH

Basic stuff like methalox storage and transfer on orbit? Raptor Vac coast and restart?

But the main advantage would be putting similar payload to a better GTO orbit than Ariane 5, with a fully reusable system. And beating DIVH payload to direct GEO insertion if fully expended. Falcon Heavy doesn't have either of those capabilities now, and both could be worthwhile in the current market.

This, also how is a composite construction stage protected by PICA-X going to handle MMOD and re-entry from LEO multiple times with minimal refurbishment?  How will the Raptor perform in the space and re-entry environment repeatedly?  A lot more procedural knowledge to be gained in a complete reusable architecture besides just constructing a prototype, big or small. 


Offline philw1776

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Re: Should ITS have a smaller prototype to ease development?
« Reply #127 on: 02/25/2017 05:21 PM »
An alternative would be to have a full size (dimensions) ITS prototype, but at lower performance.

So lower numbers of lower thrust Raptor on the booster. Only part fill the tanks. Aim for 50 tonnes of payload, rather than 300 tonnes.

Agreed.
Earlier in this thread I had proposed simply flying a fully mfg tooled, partially fueled ITS with initially just 3 seal level Raptors sub-orbitally. Maybe move to an interim all SL Raptor test vehicle or maybe not.

Followed by a fully mfg tooling sized booster stage but partially fueled with just 21 Raptors.  Fly and recover, then next it's enough to launch a SL & vac ITS with close to zero payload into LEO to test re-entry.

I ran some rocket equation #s and this seems to work. 

And so on...

As someone who has developed hardware/software systems with 5 9s reliability goals my view (yes, I know I'm not aerospace experienced) is that sub scaled vehicles will only increase your already expensive tooling costs, delay final schedules and won't give the exact test results that flying your actual base hardware configuration does.  Too many unknown unknowns in scale models.
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Offline philw1776

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Re: Should ITS have a smaller prototype to ease development?
« Reply #128 on: 02/25/2017 05:28 PM »
An alternative would be to have a full size (dimensions) ITS prototype, but at lower performance.

So lower numbers of lower thrust Raptor on the booster. Only part fill the tanks. Aim for 50 tonnes of payload, rather than 300 tonnes.

Agreed.
Earlier in this thread I had proposed simply flying a fully mfg tooled, partially fueled ITS with initially just 3 seal level Raptors sub-orbitally. Maybe move to an interim all SL Raptor test vehicle or maybe not.

Followed by a fully mfg tooling sized booster stage but partially fueled with just 21 Raptors.  Fly and recover, then next it's enough to launch a SL & vac ITS with close to zero payload into LEO to test re-entry.

I ran some rocket equation #s and this seems to work. 

And so on...

As someone who has developed hardware/software systems with 5 9s reliability goals my view (yes, I know I'm not aerospace experienced) is that sub scaled vehicles will only increase your already expensive tooling costs, delay final schedules and won't give the exact test results that flying your actual base hardware configuration does.  Too many unknown unknowns in scale models.

..., the ITS will be tested as Musk outlined in his Powerpoint show.  He can't afford the dollars and more importantly to him personally the TIME wasted in mini-ITS whatevers that do not lead directly to his goal. Per his 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.
« Last Edit: 02/25/2017 05:29 PM by philw1776 »
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Offline spacenut

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Re: Should ITS have a smaller prototype to ease development?
« Reply #129 on: 02/25/2017 06:31 PM »
I still think that because pad 39A is designed for 12 million lbs thrust, this should be the maximum for the BFR, and then scale ITS accordingly.  Also, 12 m or 40' is the widest a river/coastal waterway barge can carry.  Again scale BFR accordingly. 

Otherwise, a new launch pad and facility would have to be built somewhere, and the manufacturing for both BFR and ITS will have to be built at the launch facility.  This is expensive in and of itself. 

There are probably any number of vacant buildings that could be used to manufacture the BFR/ITS along the waterways.  No new manufacturing facility, only new tooling.  Even McCloud, while only manufacturing one SLS per year, could make 6 Saturn V's.  So if BFR/ITS is fully reusable, 3-4 per year could be made there, while not making SLS.  This would keep the work force fully employed and as the BFR/ITS come off the assembly line fully reusable, a fleet of these can be built over several years.  Again taking advantage of existing facilities with a slightly smaller ITS. 

Offline RotoSequence

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Re: Should ITS have a smaller prototype to ease development?
« Reply #130 on: 02/25/2017 07:14 PM »
I think there may be no other option for him than to develop a mini ITS architecture. Currently all his revenue comes from being the most cost effective way of getting into LEO and other earth orbits. However Bezos is building what could evolve into a fully reusable system to get into similar orbits based on a raptor like engine. To stop Bezos eating his lunch I would think he needs to look at development of a raptor powered F9 replacement with a reusable upper stage. He could use the falcon heavy with reusable upper stage but hard to see how that would be competitive against Bezos single stick approach

Something similar in shape to ITS would make sense. It could have a cargo and manned version and would be capable of moon missions etc if it's used semi permanent ITS tankers in orbit. Cargo version would be first to meet commercial requirements. But down the track a crewed version would also have much greater crew capacity than the dragon2 if such a requirement was to evolve.

Or Elon skips this step entirely and uses the absurd mass fraction of the Spaceship as the basis for a SSTO launcher that can service all foreseeable LEO payloads. If you use twelve sea-level raptors, it should be possible to push 60 tons to LEO, including landing fuel.

Online OneSpeed

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Re: Should ITS have a smaller prototype to ease development?
« Reply #131 on: 02/27/2017 10:17 AM »
Yes, people don't seem to be grasping the size difference going from F9/FH to ITS. Putting a mini-ITS on a scale that most propose on FH would be like putting a F9 upper stage on a F1 first stage. It is just too big.

Agreed, here's how a full scale ITS ship would look on top of a FH launcher. It would not perform well.

Offline dror

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Re: Should ITS have a smaller prototype to ease development?
« Reply #132 on: 02/27/2017 11:46 AM »
yes

i had surgery today and i came out of the haze to say this.

There have been a lot of threads about this. the conclusion always is that it is a waste of time and money, and actually slows things down. OP should do their homework and link to all of them.  Why is this time different?
L2 link
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Offline Rei

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Re: Should ITS have a smaller prototype to ease development?
« Reply #133 on: 03/02/2017 10:17 AM »
The area of a sphere goes goes up as the square of the radius, the volume rises by the cube.

Yes, but the thickness of a pressure-bearing spherical shell increases linearly with the radius of the sphere when at constant pressure and stress.

No, things don't scale perfectly, but it's not a squared/cubed difference.  If you scale size as well as CF mass per unit area, you're roughly scaling all properties evenly.
« Last Edit: 03/02/2017 02:50 PM by Rei »

Offline envy887

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Re: Should ITS have a smaller prototype to ease development?
« Reply #134 on: 03/02/2017 01:58 PM »
Yes, people don't seem to be grasping the size difference going from F9/FH to ITS. Putting a mini-ITS on a scale that most propose on FH would be like putting a F9 upper stage on a F1 first stage. It is just too big.

A version that is 1/6 or 1/8 the mass would work fine on FH. It would be only slightly larger in diameter than the current fairing, but would have much better performance than the current stage.

But when you scale something *that* small, it is no longer super helpful beyond verifying the most basic stuff. Scale changes things, it changes how air flows around the vehicle, and it changes how much heat needs to be dissipated, and so on.

The area of a sphere goes goes up as the square of the radius, the volume rises by the cube. Sub-scale models may be of value in terms of technology development, but in areas where basic physics define your spacecraft (like hypersonic retro-propulsion) then the gain is an illusion. A smaller ITS - call it the ITS-SP after the 747-SP - is only of value if it fills a market niche, eg for LEO or Lunar/HEO missions, and it may well be that simply flying a standard ITS half-empty would also fill that niche, and without any unique development or manufacturing costs.

Actually, subscale makes entry easier, because more area and less mass means lower heating rates. It does make launch less efficient, because drag is a function of area, but delta-v a function of mass. As Rei pointed out, pressure vessel mass scales linearly, so the same PMF should be achievable.

The "unique development or manufacturing costs" for ITS are the gigantic booster and 12m infrastructure. A 1/6 volume mini-ITS at ~375 tonnes GLOM for the upper stage + payload and ~6 meter diameter could fly on Falcon Heavy. That means all the existing infrastructure can be used: build in Hawthorne, truck overland, test in McGregor, process in the 39A HIF, launch on 39A with minimal modifications to the TEL and pad.

And the "niche" filled would be 15 tonnes to GTO fully reuseable. Plus demonstrating orbital refueling, high-energy lifting VTOL EDL, and the chance to land 50 tonnes on Mars or the Moon. Basically the entire ITS paradigm without most of the massive infrastructure investment.

Offline Lars-J

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Re: Should ITS have a smaller prototype to ease development?
« Reply #135 on: 03/02/2017 05:34 PM »
The "unique development or manufacturing costs" for ITS are the gigantic booster and 12m infrastructure. A 1/6 volume mini-ITS at ~375 tonnes GLOM for the upper stage + payload and ~6 meter diameter could fly on Falcon Heavy. That means all the existing infrastructure can be used: build in Hawthorne, truck overland, test in McGregor, process in the 39A HIF, launch on 39A with minimal modifications to the TEL and pad.

No, A 6 meter diameter payload is NOT easily truckable. SpaceX settled on a maximum practical diameter of 3.7m for F5/F9 because of highway transport limitations.

Bigger things can be transported, but the roads you can use dwindle fast as the size goes up.
« Last Edit: 03/02/2017 05:35 PM by Lars-J »

Offline JasonAW3

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Re: Should ITS have a smaller prototype to ease development?
« Reply #136 on: 03/02/2017 06:30 PM »
The "unique development or manufacturing costs" for ITS are the gigantic booster and 12m infrastructure. A 1/6 volume mini-ITS at ~375 tonnes GLOM for the upper stage + payload and ~6 meter diameter could fly on Falcon Heavy. That means all the existing infrastructure can be used: build in Hawthorne, truck overland, test in McGregor, process in the 39A HIF, launch on 39A with minimal modifications to the TEL and pad.

No, A 6 meter diameter payload is NOT easily truckable. SpaceX settled on a maximum practical diameter of 3.7m for F5/F9 because of highway transport limitations.

Bigger things can be transported, but the roads you can use dwindle fast as the size goes up.

Sounds like a "Build on site" type of project.

      This wouldn't exactly be such a bad idea, as it would be good training and practice for construction of the final product.
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Offline punder

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Re: Should ITS have a smaller prototype to ease development?
« Reply #137 on: 03/02/2017 06:41 PM »
And the "niche" filled would be 15 tonnes to GTO fully reuseable. Plus demonstrating orbital refueling, high-energy lifting VTOL EDL, and the chance to land 50 tonnes on Mars or the Moon. Basically the entire ITS paradigm without most of the massive infrastructure investment.

I'm not a rocket scientist, so it's not clear to me why the vehicle could only put 15 tonnes in GTO but land 50 tonnes on Mars or the Moon. Could you explain that? Seriously, no snark intended.

Offline envy887

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Re: Should ITS have a smaller prototype to ease development?
« Reply #138 on: 03/02/2017 07:24 PM »
The "unique development or manufacturing costs" for ITS are the gigantic booster and 12m infrastructure. A 1/6 volume mini-ITS at ~375 tonnes GLOM for the upper stage + payload and ~6 meter diameter could fly on Falcon Heavy. That means all the existing infrastructure can be used: build in Hawthorne, truck overland, test in McGregor, process in the 39A HIF, launch on 39A with minimal modifications to the TEL and pad.

No, A 6 meter diameter payload is NOT easily truckable. SpaceX settled on a maximum practical diameter of 3.7m for F5/F9 because of highway transport limitations.

Bigger things can be transported, but the roads you can use dwindle fast as the size goes up.

At 12m they NEED to have facilities on a barge waterway or at the test/launch site, while at 6m trucking, barging, or flying (in a Super Guppy) a upper stage are all options. I didn't say they were easy, but much more so than a 12m beast. It doesn't have to be as quick as moving a F9 because they would only need 2 or 3 per year, with the stages flying back to CCAFS or Vandy after missions.

Offline envy887

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Re: Should ITS have a smaller prototype to ease development?
« Reply #139 on: 03/02/2017 07:25 PM »
And the "niche" filled would be 15 tonnes to GTO fully reuseable. Plus demonstrating orbital refueling, high-energy lifting VTOL EDL, and the chance to land 50 tonnes on Mars or the Moon. Basically the entire ITS paradigm without most of the massive infrastructure investment.

I'm not a rocket scientist, so it's not clear to me why the vehicle could only put 15 tonnes in GTO but land 50 tonnes on Mars or the Moon. Could you explain that? Seriously, no snark intended.

15t to GTO would be a single launch+return, while 50t would take ~6 refueling launches and be one way (unless refueled on Mars)

Offline Lars-J

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Re: Should ITS have a smaller prototype to ease development?
« Reply #140 on: 03/02/2017 08:47 PM »
At 12m they NEED to have facilities on a barge waterway or at the test/launch site, while at 6m trucking, barging, or flying (in a Super Guppy) a upper stage are all options. I didn't say they were easy, but much more so than a 12m beast. It doesn't have to be as quick as moving a F9 because they would only need 2 or 3 per year, with the stages flying back to CCAFS or Vandy after missions.

It has nothing to do with being quick. Either a road (with overpasses and powerlines) can handle a 6m diameter payload, or it can't. And I'm suggesting that trucking a 6m diameter payload from Hawthorne to McGregor and the launch sites might actually be impossible.

Offline spacenut

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Re: Should ITS have a smaller prototype to ease development?
« Reply #141 on: 03/02/2017 09:08 PM »
I was thinking a mini ITS and a booster no larger than 12m to take advantage of the inland waterways.  No way trucking larger than 3.7m dia. is possible via road or even railroad.  On Americas vast inland waterway system 12m dia. is possible.  Any larger than 12 m diameter will either have to go by ship or be built at the launch site only.  Any return ITS or booster will have to be at the launch site only. 

On has to take into consideration existing facilities building ITS.  We do not build planes larger than 747's in America due to the size of existing airports.  Even the large Airbus or Russian transport plane only has a hand full of runways to land and refuel on.  F9/FH can take all of existing land and sea transportation.  At least with our inland waterway system, it opens up a vast area of America one can either launch or land ITS and manufacture the craft and booster if they use the limitations involved. 

Offline envy887

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Re: Should ITS have a smaller prototype to ease development?
« Reply #142 on: 03/02/2017 10:53 PM »
At 12m they NEED to have facilities on a barge waterway or at the test/launch site, while at 6m trucking, barging, or flying (in a Super Guppy) a upper stage are all options. I didn't say they were easy, but much more so than a 12m beast. It doesn't have to be as quick as moving a F9 because they would only need 2 or 3 per year, with the stages flying back to CCAFS or Vandy after missions.

It has nothing to do with being quick. Either a road (with overpasses and powerlines) can handle a 6m diameter payload, or it can't. And I'm suggesting that trucking a 6m diameter payload from Hawthorne to McGregor and the launch sites might actually be impossible.

Yeah, I don't think trucking cross-country like F9 would work well, but a combination of trucking, shipping, and maybe flying should work with existing assets.

I'm thinking more like trucking from Hawthorne to the Marina del Rey (Endeavor and ET-94 did a similar trip), then cargo ship to one of the Texas ports, truck inland to McGregor and back, then cargo ship to Port Canaveral. Or lease a Super Guppy or Beluga from LAX to McGregor to Canaveral.

It's not impossible to move a 6 by 25 meter, 20 tonne stage and utilize SpaceX's existing sites. It's quite impossible with a 12m stage, especially the ITS booster.

Offline punder

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Re: Should ITS have a smaller prototype to ease development?
« Reply #143 on: 03/03/2017 06:21 PM »
15t to GTO would be a single launch+return, while 50t would take ~6 refueling launches and be one way (unless refueled on Mars)

Had the distinct feeling I was missing something obvious. Thanks.

Intelligent arguments on both sides. But obviously this has been hashed out inside SpaceX. So I expect they will go for the home run.

On the other hand, they could be keeping an intermediate design close to the vest for political reasons, not wanting to antagonize NASA with an SLS-killer quite yet. On the gripping hand, they just antagonized the heck out of NASA with the MoonDragon announcement.

I just don't know WHAT to think! (classic movie line)

Offline TomH

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Re: Should ITS have a smaller prototype to ease development?
« Reply #144 on: 03/04/2017 12:18 AM »
On the other hand, they could be keeping an intermediate design close to the vest for political reasons, not wanting to antagonize NASA with an SLS-killer

I am not sure they would antagonize NASA as much as a select group of senators.

Offline watermod

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Re: Should ITS have a smaller prototype to ease development?
« Reply #145 on: 03/04/2017 02:46 AM »
I am thinking ITS full size will be required to launch the full LEO and VLEO sat network that SpaceX desires.

12,000 sats... if FH could put up 100 at time that's still too many for their launch rate at all launch sites.   It's going to  take ITS

Offline Jcc

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Re: Should ITS have a smaller prototype to ease development?
« Reply #146 on: 03/04/2017 02:45 PM »
I am thinking ITS full size will be required to launch the full LEO and VLEO sat network that SpaceX desires.

12,000 sats... if FH could put up 100 at time that's still too many for their launch rate at all launch sites.   It's going to  take ITS

I wonder how they will deploy to different orbital planes if they launch 1000 at a time. Possibly the ITS second stage will have many burns to achieve different orbits and deploy groups of sats.

Offline punder

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Re: Should ITS have a smaller prototype to ease development?
« Reply #147 on: 03/04/2017 07:02 PM »
On the other hand, they could be keeping an intermediate design close to the vest for political reasons, not wanting to antagonize NASA with an SLS-killer

I am not sure they would antagonize NASA as much as a select group of senators.

Yes. Sometimes I say "NASA" when I mean the whole federal bureaucracy/congressional vote-protecting/revolving-door-lobbying/not-invented-here complex.