Author Topic: IAC 2017 -- ITS v0.2  (Read 18044 times)

Offline AncientU

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IAC 2017 -- ITS v0.2
« on: 05/29/2017 10:50 AM »
Quote
Elon Musk will likely reveal more details about the Interplanetary Transport system on the one year anniversary of the first announcement at the 2016 International Astronautical conference. IAC2017, hosted by the Space Industry Association of Australia (SIAA) will take place in Adelaide, Australia from 25 29 September 2017.

Quote
Robert Zubrin, Longtime Mars Colonization advocate, gave a Critique of the SpaceX Interplanetary Transport System.

Zubrin was struck by many good and powerful ideas in the Musk plan. However, Musks plan assembled some of those good ideas in an extremely suboptimal way, making the proposed system impractical. Still, with some corrections, a system using the core concepts Musk laid out could be made attractive not just as an imaginative concept for the colonization of Mars, but as a means of meeting the nearer-at-hand challenge of enabling human expeditions to the planet.
bold mine
http://www.prometheism.net/elon-will-likely-reveal-more-details-on-his-big-mars-colonization-rocket-at-iac-2017-sept-25-29-2017-next-big-future/

Many new spins on original IAC design by RZ.

What will EM present this year?
« Last Edit: 05/29/2017 11:38 AM by AncientU »
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Offline AncientU

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Re: IAC 2017 -- ITS v0.2
« Reply #1 on: 05/29/2017 10:59 AM »
IMO, this year's presentation will be the development path to establish a foothold on Mars.

Red Dragon missions will be discussed along with all contributions planned for the Falcon family.

ITS jr. will be (may be) presented as pioneering the technology and establishing the original expeditionary outposts.  Surface infrastructure will be outlined, including surface power, water collection, propellant ISRU.  Scale and timeline of program will be detailed.
« Last Edit: 05/29/2017 11:35 AM by AncientU »
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Offline su27k

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Offline AncientU

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Re: IAC 2017 -- ITS v0.2
« Reply #3 on: 05/29/2017 11:32 AM »
Old, but consistent with rethinking the v0.1 design from IAC 2016.

Many here believed single step to 4x Saturn V was not feasible (or wise).
« Last Edit: 05/29/2017 11:32 AM by AncientU »
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Offline hkultala

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Re: IAC 2017 -- ITS v0.2
« Reply #4 on: 05/29/2017 11:40 AM »
Old, but consistent with rethinking the v0.1 design from IAC 2016.

Many here believed single step to 4x Saturn V was not feasible (or wise).

About the criticism of the "too big BFR/ITS":

I've heard mostly arguments:

1) "LC-39 is not build for such thrust and completely new launch site is needed."
This seems to be a valid argument, though not a showstopper.

2) "Too many engines, look what happened to N-1". This is not a very good argument, as the steering system of BRF is different than ITS, BFR cannot fail because roll control engine fails because there are no dedicated roll control engines, and BRF has much better redundancy as N-1.



Online jpo234

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Re: IAC 2017 -- ITS v0.2
« Reply #5 on: 05/29/2017 11:54 AM »
2) "Too many engines, look what happened to N-1". This is not a very good argument, as the steering system of BRF is different than ITS, BFR cannot fail because roll control engine fails because there are no dedicated roll control engines, and BRF has much better redundancy as N-1.

Not to mention that they can actually test fire the engines before flight.
« Last Edit: 05/29/2017 11:55 AM by jpo234 »

Offline Star One

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IAC 2017 -- ITS v0.2
« Reply #6 on: 05/29/2017 01:51 PM »
http://www.prometheism.net/elon-will-likely-reveal-more-details-on-his-big-mars-colonization-rocket-at-iac-2017-sept-25-29-2017-next-big-future/

Original article is from nextbigfuture (not the most reputable news source on the Internet...): http://www.nextbigfuture.com/2017/05/elon-will-likely-reveal-more-details-on-his-big-mars-colonization-rocket-at-iac-2017-sept-25-29-2017.html

Zubrin's critics was from last year, pretty old.

Not sure why EM should adapt his plans just because of one person's critique. The whole thing by Zubrin smacks of I know best.
« Last Edit: 05/29/2017 01:52 PM by Star One »

Offline AncientU

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Re: IAC 2017 -- ITS v0.2
« Reply #7 on: 05/29/2017 02:44 PM »
Zubrin's idea about a different 'flavor' of reuse -- using the spaceship as a hab once on the surface instead of returning empty -- has interesting applications for early expeditions to Mars.  (I have suggested stripping out most of the ECLSS before sending the vehicle back to Earth, for use on Mars and to lighten the return load.)  This stems from his concept of a three-stage vehicle, where the second stage would boost the spaceship toward Mars, and then return to Earth (via a Lunar swing-by) so that it could be used multiple times per synod.  Interesting spin on ITS... YMMV.

He does pretty much nail the giant leap from today to a 4x Saturn V, though.
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Offline AncientU

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Re: IAC 2017 -- ITS v0.2
« Reply #8 on: 05/29/2017 02:53 PM »
Old, but consistent with rethinking the v0.1 design from IAC 2016.

Many here believed single step to 4x Saturn V was not feasible (or wise).

About the criticism of the "too big BFR/ITS":

I've heard mostly arguments:

1) "LC-39 is not build for such thrust and completely new launch site is needed."
This seems to be a valid argument, though not a showstopper.

2) "Too many engines, look what happened to N-1". This is not a very good argument, as the steering system of BRF is different than ITS, BFR cannot fail because roll control engine fails because there are no dedicated roll control engines, and BRF has much better redundancy as N-1.

I agree with your take on #2.

Suggest a #3 heard frequently:
3. "Scale is too large for test and demonstration phase."  Too much risk to test EDL at Mars, for instance, with full-scale spaceship.  Booster testing in landing cradle another challenge, but significantly easier.  Refueling demonstrations (early attempts) would be crazy with two full-scale spaceships, one tanker and one cargo.

Lots of vociferous opposition on forum to anything intermediate scale, though.
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Online GWH

Re: IAC 2017 -- ITS v0.2
« Reply #9 on: 05/29/2017 03:42 PM »
I really hope that this information can be trickled out in advance this time rather than a big dump all at once.
It would be nice to see some more properly prepared questions from the audience. I don't think all the secrecy followed by splashy presentations is doing well to get official buy in on the ITS.

Offline Star One

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Re: IAC 2017 -- ITS v0.2
« Reply #10 on: 05/29/2017 04:12 PM »
I really hope that this information can be trickled out in advance this time rather than a big dump all at once.
It would be nice to see some more properly prepared questions from the audience. I don't think all the secrecy followed by splashy presentations is doing well to get official buy in on the ITS.
Some of questions last year he got asked were awful and you certainly don't want a repeat of that, so any idea that will avoid this seems a good idea to me.

Offline Nathan2go

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Re: IAC 2017 -- ITS v0.2
« Reply #11 on: 05/29/2017 04:46 PM »
What will EM present this year?
I think the original ITS presentation was a very compelling display of how, with modest technology improvements to chemical rockets, affordable transportation between Earth and an established Mars space port becomes plausible.

It did not show a roadmap of how such a space port could be built, which is likely what put-off critics like Zubrin.  Hopefully that will be the focus of the next ITS talk.

A more plausible scale-up would use a 12 m diameter landing capsule, which could be sent to Mars by a single launch of a 200-300 ton-to-LEO rocket.  Trans-Mars mass would be around 60-90 t (to stay in the 0.8t/m^2 range that is talked about), and the surface payload about half that.  This would align with Zubrin's suggestion that the initial trans-Mars habitat should stay on Mars as crew housing.  This also allows stockpiling supplies on Mars prior to crew arrival, to make the Mars base the "second safest place in the solar system" (to quote an old Zubrin statement).  A crew capsule also allows implementation of a launch escape system.

With a capsule-based architecture, the first stage could be the full scale (or somewhat shorter & lighter, but full 12m width) reusable ITS booster (e.g. 34-42 Raptor engines).  Making an interim expendable second stage would reduce the development cost to get the first capsules launched.  A sea barge landing of the booster reduces the size and cost of the expendable second stage (e.g. 4-6 Raptor engines).  When available, the reusable tanker second stage could also carry the landing capsule, but it would require 2 launches and an LEO re-fueling (or 1 launch and an expendable 3rd stage).

With the upcoming debut of the Falcon Heavy, there is also a chance that SpaceX will start with a smaller 3-core ITS variant, to allow a set of 9.5 m diameter cores to loft the same 300 tons-LEO (90-100t to Mars).  This suggestion would make Zubrin happier, but a 9.5 m dia upper-stage ship is not as well suited to landing 300 tons on Mars (tall & skinny is less desirable for broadside entry and vertical landing).  So maybe the 3-core variant has to fly an expendable 2nd stage (and capsules for 1-way transport) until the 12m re-usable 2nd stage is ready.  A 12 m capsule might get built in a small factory, but a 12m 2nd stage needs a factory large enough to build a full 12 m booster.  So why spend the money building a factory/infrastructure for 9.5 m boosters?

I think the initial ITS will be a 12 m diameter, reusable booster, expendable 2nd stage, capsule lander (perhaps with derated Raptor thrust and stack mass, for 160-250t LEO); that path has a good balance of "not too far beyond Falcon" and "leads to the full ITS", and reduces the amount of "starting over" between steps.  The expendable 2nd stage also provides the versatility for more SLS missions.
« Last Edit: 05/29/2017 07:33 PM by Nathan2go »

Offline Nathan2go

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Re: IAC 2017 -- ITS v0.2
« Reply #12 on: 05/29/2017 05:12 PM »
Robert Zubrin, Longtime Mars Colonization advocate, gave a Critique of the SpaceX Interplanetary Transport System.
...
Many new spins on original IAC design by RZ.
One aspect of the ITS pitch that Zubrin completely missed was the significance of the 115 day Mars transit time.  Zubrin has often (rightly in my opinion) argued that when NASA pitches research into advanced technologies which will reduce Mars transit time, they are mainly using it as an excuse for failure to launch crewed Mars missions. 

Zubrin makes the argument that transit faster than 180 days is a waste of propulsion resources which is better spent on increasing payload.  This is convincing for expendable rockets.

However careful examination of SpaceX's cost analysis shows that because the ITS booster and tanker are fully reusable and fly frequently, they dramatically reduce the cost of LEO propellant.  The mission cost is dominated by the construction cost of the 2nd stage ship, and its slow 4-year reuse cycle (& likely lifetime of 5-8 round trips).  Having the ship depart LEO with tanks half-full simply doesn't save much money compared to leaving with full tanks for a speedier transit.

That said, I think that certainly all cargo flights and some of the passenger flights will make slower transits, to save on propellant cost, as Zubrin suggests.  And NASA's impressive work on solar electric propulsion may someday be the best way to do cargo.  But the flagship (carrying the wealthy passengers) will go fast and will use chemical propulsion.
« Last Edit: 05/29/2017 07:29 PM by Nathan2go »

Offline matthewkantar

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Re: IAC 2017 -- ITS v0.2
« Reply #13 on: 05/29/2017 05:20 PM »
Improving the performance of 55 year old tech by a factor of four should be trivial. Getting the cost of doing so anywhere near the target Musk has set is a much bigger mountain to climb.

Matthew

Offline AncientU

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Re: IAC 2017 -- ITS v0.2
« Reply #14 on: 05/29/2017 05:34 PM »
The fast transit times enables a round-trip each synod per EM.
This is the primary driver. 

Side benefits of a quick transfer are:
Reduced radiation exposure
Smaller consumables loading, thus more payload or larger number of travelers accommodated
Less deterioration of health/strength of travelers who arrive fit to work instead of needing care
Reduced psychological burden on travelers from long-duration spaceflight

Whatever the final size of the early vehicles, on-orbit refueling and fast transfers will (hopefully) remain.
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Online jpo234

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Re: IAC 2017 -- ITS v0.2
« Reply #15 on: 05/29/2017 06:25 PM »
My take:
De-scope in this context doesn't mean "make ITS smaller" but "make it more versatile". The booster would become a generic launcher with a reusable cargo stage in addition to the spaceship and the tanker. The cargo stage would be used for bread and butter satellite launches ("make it pay for itself ") including the SpaceX constellation.

Remember: Tom Mueller said that the Mars rocket would be the revolutionary one and Paul Wooster said that getting people to Mars by the mid 2020th is achievable.
« Last Edit: 05/29/2017 06:27 PM by jpo234 »

Offline spacenut

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Re: IAC 2017 -- ITS v0.2
« Reply #16 on: 05/29/2017 06:41 PM »
A short squat 12m booster with 16 engines and a reusable second stage/spacecraft with say 2 vacuum Raptors and one sea level Raptor for landing would be a useful start.  It may only get 100 tons to LEO, but with refueling, and complete reusability can test all features from pad 39A. 

Then as the system is proven (like Falcon 9 v1), the tanks can be stretched, more engines installed, and the second stage/spacecraft could also be stretched to become a full ITS.

Testing and working out problems on the smaller version can be done while building a new launch pad and facilities. 

Falcon 9 was changed from F5 to F9, then as the engines increased in power, stretched for more fuel and fuel for landing.

Same can be done with the 12 m ITS jr to as big as you can make it. 

Offline Nathan2go

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Re: IAC 2017 -- ITS v0.2
« Reply #17 on: 05/29/2017 07:03 PM »
The fast transit times enables a round-trip each synod per EM.
...
Whatever the final size of the early vehicles, on-orbit refueling and fast transfers will (hopefully) remain.
Round-trip each synod could be very important for economics of a fully reusable lander/return-ship (I have not seen the numbers to back this up though).  But like I said, I think the first trips should be one-way, on a landing capsule, with a launch escape system.

Zubrin dismisses the importance of reducing radiation exposure, and says the recovery from zero-gravity will be quick (he cites astronauts playing tennis a few days after landing here).  I agree.

If you're flying to a place without a spaceport (i.e. you're first), there's no one to pick you up if you land off-target; you have to carry all of your consumables anyway (for transit and surface stay); faster transit means longer surface stay, so there's no savings in consumables.

The more you can do without adding technology-beyond-Falcon, the more plausible the whole thing becomes.  I think fast transits have to wait.

On-orbit refueling?  It's a great way to avoid building a 3rd stage while allowing re-use of the 2nd stage.  For the 300 ton-to-LEO rocket size though, on-orbit refueling makes the trans-Mars payload too big for a capsule landing (100t is about the max viable).  So I think on-orbit refueling only makes sense for the ITS architecture (i.e. 2nd stage is the reusable Mars landing/Earth-return vehicle).  This only makes sense for ITS or min-ITS; mini-ITS is too small for colonization, yet will require mastery of all of the ITS technology, so I think the 300t size rocket with expendable 2nd stage and capsule (and no on-orbit refueling) is a better next step.

A short squat 12m booster with 16 engines and a reusable second stage/spacecraft ...
If the initial application is launching LEO comsats, then sure, a reusable 2nd stage would be great (and a big 2nd stage & LEO destination avoids the needs for sea landing). To start Mars landings or if NASA shakes loose a few billion$ for commercial launches to the Deep Space Gateway, an expendable 2nd stage is simpler (avoids on-orbit refueling or a 3rd stage).
« Last Edit: 05/29/2017 07:22 PM by Nathan2go »

Offline Robotbeat

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Re: IAC 2017 -- ITS v0.2
« Reply #18 on: 05/29/2017 07:05 PM »
Why a landing capsule? Sounds like a really bad idea. Really expensive & inefficient vehicle for just one-way. Has to be two way so you can reuse it.
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Offline envy887

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Re: IAC 2017 -- ITS v0.2
« Reply #19 on: 05/29/2017 07:46 PM »
What will EM present this year?
I think the original ITS presentation was a very compelling display of how, with modest technology improvements to chemical rockets, affordable transportation between Earth and an established Mars space port becomes plausible.
The required technology improvements are still:

1) Full and rapid reuse
2) orbital refueling
3) Mars ISRU for methalox
4) lifting entry and hypersonic retropropulsion

Quote
It did not show a roadmap of how such a space port could be built, which is likely what put-off critics like Zubrin.  Hopefully that will be the focus of the next ITS talk.

A more plausible scale-up would use a 12 m diameter landing capsule, which could be sent to Mars by a single launch of a 200-300 ton-to-LEO rocket.  Trans-Mars mass would be around 60-90 t (to stay in the 0.8t/m^2 range that is talked about), and the surface payload about half that.  This would align with Zubrin's suggestion that the initial trans-Mars habitat should stay on Mars as crew housing.  This also allows stockpiling supplies on Mars prior to crew arrival, to make the Mars base the "second safest place in the solar system" (to quote an old Zubrin statement).  A crew capsule also allows implementation of a launch escape system.

I don't think a large capsule is all that plausible. Capsules don't scale very well, and don't have a lot of room for return fuel. I can't see SpaceX spending that much effort on an expendable cargo vehicle, or building a crew vehicle with no future application for ITS.

Quote
With a capsule-based architecture, the first stage could be the full scale (or somewhat shorter & lighter, but full 12m width) reusable ITS booster (e.g. 34 Raptor engines).  Making an interim expendable second stage would reduce the development cost to get the first capsules launched.  A sea barge landing of the booster reduces the size and cost of the expendable second stage (e.g. 4 Raptor engines).  When available, the reusable tanker second stage could also carry the landing capsule, but it would require 2 launches and an LEO re-fueling (or 1 launch and an expendable 3rd stage).

I can't see SpaceX developing another expendable stage with that kind of performance. Orbital refueling is much, much better for payload to TMI. With orbital refueling and a single Raptor upper stage, Falcon Heavy can send 60-90 tonnes to the Mars surface. Why build a booster that dwarfs Saturn V just to do that?

Quote
With the upcoming debut of the Falcon Heavy, there is also a chance that SpaceX will start with a smaller 3-core ITS variant, to allow a set of 9.5 m diameter cores to loft the same 300 tons-LEO (90-100t to Mars).  This suggestion would make Zubrin happier, but a 9.5 m dia upper-stage ship is not as well suited to landing 300 tons on Mars (tall & skinny is less desirable for broadside entry and vertical landing).  So maybe the 3-core variant has to fly an expendable 2nd stage (and capsules for 1-way transport) until the 12m re-usable 2nd stage is ready.  A 12 m capsule might get built in a small factory, but a 12m 2nd stage needs a factory large enough to build a full 12 m booster.  So why spend the money building a factory/infrastructure for 9.5 m boosters?

I think the initial ITS will be 12 m diameter, reusable booster, expendable 2nd stage, capsule lander (perhaps with derated Raptor thrust and stack mass, for 160-250t LEO); that path has a good balance of "not too far beyond Falcon" and "leads to the full ITS", and reduces the amount of "starting over" between steps.  The expendable 2nd stage also provides the versatility for more SLS missions.

After the experience gained from building FH, it sounds very unlikely that SpaceX will try another triple-core booster.

They will almost certainly start with a diameter that they want to fly long term (likely 12m) and simply shorten the booster if they need to ... they can always make it longer later like F9.

Online Lars-J

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Re: IAC 2017 -- ITS v0.2
« Reply #20 on: 05/29/2017 08:05 PM »
A more plausible scale-up would use a 12 m diameter landing capsule, which could be sent to Mars by a single launch of a 200-300 ton-to-LEO rocket.  Trans-Mars mass would be around 60-90 t (to stay in the 0.8t/m^2 range that is talked about), and the surface payload about half that.  This would align with Zubrin's suggestion that the initial trans-Mars habitat should stay on Mars as crew housing.  This also allows stockpiling supplies on Mars prior to crew arrival, to make the Mars base the "second safest place in the solar system" (to quote an old Zubrin statement).  A crew capsule also allows implementation of a launch escape system.

So... You think the intermediate step should be something completely different?  ???

Yeah, I get that people don't like the ITS system as described. But going from there to wishfully thinking that Elon will make a 180 turn to your own dream architecture...  :o

A crew capsule also allows implementation of a launch escape system.

A 12 m crew capsule abort system. Good luck with that.  :o  Apollo architecture and capsules in general do not scale well. Orion is finding this out, and that is for a minor scale up of 3.9m to 5m. A 12m capsule... Does not compute.

With the upcoming debut of the Falcon Heavy, there is also a chance that SpaceX will start with a smaller 3-core ITS variant, to allow a set of 9.5 m diameter cores to loft the same 300 tons-LEO (90-100t to Mars).  This suggestion would make Zubrin happier

3 core ITS? Nope. They are having hard enough time with FH.

No one at SpaceX cares about making Zubrin happy. (thankfully)
« Last Edit: 05/29/2017 08:37 PM by Lars-J »

Online Kenp51d

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Re: IAC 2017 -- ITS v0.2
« Reply #21 on: 05/29/2017 08:12 PM »

I would add 1 more required technology improvement to the list.
5) Long term storage of deep cryogenic propellants

1) Full and rapid reuse
2) orbital refueling
3) Mars ISRU for methalox
4) lifting entry and hypersonic retropropulsion

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Offline Robotbeat

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Re: IAC 2017 -- ITS v0.2
« Reply #22 on: 05/29/2017 08:16 PM »
The ITS as described at IAC 2016 is awesome. The only two things I think you could reasonably object to are the raw size (impracticality large thrust for LC39a and Brownsville), the ambitious landing tech, and maybe the lack of abort.

A descoped ITS could resolve the first two issues, giving them time to develop some other launch site for the full ITS and test out the landing cradle concept. I have a feeling that Block 5 Falcon 9 is giving them other ideas for how to improve turnaround time other than the launch cradle (although the launch cradle could still be an upgrade option). Crew abort could be addressed on a customer by customer basis, perhaps partially resolved by just having a very solid launch history (since the vast majority of launches will be uncrewed).
« Last Edit: 05/29/2017 08:20 PM by Robotbeat »
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Offline Robotbeat

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Re: IAC 2017 -- ITS v0.2
« Reply #23 on: 05/29/2017 08:25 PM »
But the basic idea behind ITS just kicks most architectures' butts so hard that I don't think people have yet realized how much better this approach is. Just two stages, with a couple variants of the upper stage, is all the vehicle you need. That's dramatically simpler than anything else (only exception would be, say, Delta Clipper doing SSTO and refueling... This is very similar to ITS but SSTO), and frankly makes a lot of other approaches look like a complex waste of time and money.

I mean look at Lockheed's Mars orbital basecamp idea. You have multiple SLS launches, which is 3 different stages (all expended), plus Orion and the orbital base thing and the in-space propulsion. But you're stuck in Mars orbit. Lockheed's lander concept will get you flag and footprints but no lasting presence anywhere on the surface. It looks enormously expensive for a tiny fraction of the capability. Being in Mars orbit makes you exposed to microgravity and deep space radiation the whole time, so it's much worse for astronaut health.
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Offline Robotbeat

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Re: IAC 2017 -- ITS v0.2
« Reply #24 on: 05/29/2017 08:26 PM »

I would add 1 more required technology improvement to the list.
5) Long term storage of deep cryogenic propellants

1) Full and rapid reuse
2) orbital refueling
3) Mars ISRU for methalox
4) lifting entry and hypersonic retropropulsion

Sent from my XT1565 using Tapatalk
Methane isn't a deep cryogen. It's relatively easy to get zero boil off passively with methane.
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To the maximum extent practicable, the Federal Government shall plan missions to accommodate the space transportation services capabilities of United States commercial providers. US law http://goo.gl/YZYNt0

Online Kenp51d

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Re: IAC 2017 -- ITS v0.2
« Reply #25 on: 05/29/2017 08:42 PM »
Is LOX? Kinda need some of that too.
Cislunar shouldn't​ be defficult, but Mars would be more demanding.
Shading, and insulation are part of the answer.


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Offline envy887

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Re: IAC 2017 -- ITS v0.2
« Reply #26 on: 05/29/2017 08:45 PM »
Storing a small amount of methalox in what are basically Dewars inside the main tanks should be pretty straightforward.

If SpaceX were trying to store methalox in the main tanks, I would say that's pretty low TRL. But storage in small vacuum lined tanks has been proven in operational flight systems.

Both Shuttle and Apollo demonstrated LOX storage for weeks on orbit. Shuttle even demonstrated cryo LH2 storage for up to about a month at -420 degrees F for the fuel cells.
« Last Edit: 05/29/2017 08:46 PM by envy887 »

Offline spacenut

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Re: IAC 2017 -- ITS v0.2
« Reply #27 on: 05/29/2017 09:26 PM »
LOX and liquid methane are only about 20 degrees apart.  Storage would be the same.  Liquid Hydrogen is deep cryogen, and much harder to keep cool.   

I like the idea of refueling FH 2nd stage for larger payloads to Mars or even the moon.  Therefore a lot of equipment could be sent to Mars before ITS or a Mini-ITS.  Same with the moon. 

Offline scienceguy

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Re: IAC 2017 -- ITS v0.2
« Reply #28 on: 05/29/2017 09:29 PM »
methane is a bigger molecule than hydrogen
e^(pi)i = -1

Offline Robotbeat

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Re: IAC 2017 -- ITS v0.2
« Reply #29 on: 05/29/2017 09:45 PM »
Is LOX? Kinda need some of that too.
Cislunar shouldn't​ be defficult, but Mars would be more demanding.
Shading, and insulation are part of the answer.


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No. LOx is not a deep cryogen. Deep cryogens are basically just liquid hydrogen and helium.
« Last Edit: 05/29/2017 10:03 PM by Robotbeat »
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Online Kenp51d

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Re: IAC 2017 -- ITS v0.2
« Reply #30 on: 05/29/2017 09:51 PM »
Thanks, did not research definitions before posting.


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Offline AncientU

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Re: IAC 2017 -- ITS v0.2
« Reply #31 on: 05/29/2017 10:57 PM »
Storing a small amount of methalox in what are basically Dewars inside the main tanks should be pretty straightforward.

If SpaceX were trying to store methalox in the main tanks, I would say that's pretty low TRL. But storage in small vacuum lined tanks has been proven in operational flight systems.

Both Shuttle and Apollo demonstrated LOX storage for weeks on orbit. Shuttle even demonstrated cryo LH2 storage for up to about a month at -420 degrees F for the fuel cells.

Interesting how rarely TRL* comes up in SpaceX discussions...
What TRL was supersonic retro-propulsion when they did it?
3D printed engines and engine parts?
Red Dragon's EDL profile?
Pusher abort system?
Landing legs on an orbital-class booster?
ASDS?
Full flow staged combustion engines? ...using methlox?
Refueling cryogens on orbit?
Landing the whole thing?
ISRU... on Mars?
Don't see much in the way of entire phases being devoted to 'risk reduction' during their development cycle either.

They aren't afraid to do new things if they need to be done -- maybe ignoring TRL is their key to success. 

Kinda OT for this discussion, but IAC v0.1 didn't dwell on low TRL as a barrier and expect neither will v0.2.


* Has Elon Musk ever actually said 'technology readiness level' in public?  (He'd not say TRL because he hates acronyms.)
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Re: IAC 2017 -- ITS v0.2
« Reply #32 on: 05/29/2017 11:21 PM »
Storing a small amount of methalox in what are basically Dewars inside the main tanks should be pretty straightforward.

If SpaceX were trying to store methalox in the main tanks, I would say that's pretty low TRL. But storage in small vacuum lined tanks has been proven in operational flight systems.

Both Shuttle and Apollo demonstrated LOX storage for weeks on orbit. Shuttle even demonstrated cryo LH2 storage for up to about a month at -420 degrees F for the fuel cells.

Interesting how rarely TRL* comes up in SpaceX discussions...
What TRL was supersonic retro-propulsion when they did it?
3D printed engines and engine parts?
Red Dragon's EDL profile?
Pusher abort system?
Landing legs on an orbital-class booster?
ASDS?
Full flow staged combustion engines? ...using methlox?
Refueling cryogens on orbit?
Landing the whole thing?
ISRU... on Mars?
Don't see much in the way of entire phases being devoted to 'risk reduction' during their development cycle either.

They aren't afraid to do new things if they need to be done -- maybe ignoring TRL is their key to success. 

Kinda OT for this discussion, but IAC v0.1 didn't dwell on low TRL as a barrier and expect neither will v0.2.


* Has Elon Musk ever actually said 'technology readiness level' in public?  (He'd not say TRL because he hates acronyms.)

I think you misunderstand what TRL means. SpaceX isn't ignoring it. They are simply choosing to develop some of these technologies where other are too cautious. Ignoring TRL doesn't make things easier, it is just a way to express how far from the current state of the art something is.

Offline Robotbeat

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Re: IAC 2017 -- ITS v0.2
« Reply #33 on: 05/29/2017 11:25 PM »
I do think there's some unnecessary ritual in the whole concept of the Technology Readiness Level formalism. It seems primarily a tool for getting multiple stakeholders to agree on whether a certain technology is mature enough for some application, whereas SpaceX is free to just try something.
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Offline envy887

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Re: IAC 2017 -- ITS v0.2
« Reply #34 on: 05/29/2017 11:31 PM »
Technology development is SpaceX's key competency, so current readiness probably weights lower in their trades when evaluating what options to pursue.

But they definitely factor it in, and they definitely do not develop low readiness technologies unless they deem them critical to a larger objective.

I don't expect development of long term on orbit main tank cryo storage because it's not critical to ITS.

Offline Robotbeat

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Re: IAC 2017 -- ITS v0.2
« Reply #35 on: 05/29/2017 11:33 PM »
Of course SpaceX considers how practical some technology is. But I doubt the TRL formalism is as commonly used as it is at a place like NASA.
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Offline stcks

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Re: IAC 2017 -- ITS v0.2
« Reply #36 on: 05/29/2017 11:36 PM »
I don't expect development of long term on orbit main tank cryo storage because it's not critical to ITS.

It is though, for varying definitions of long term. ITS will need to be refueled over a handful of tanker flights which could take a bit of time

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Re: IAC 2017 -- ITS v0.2
« Reply #37 on: 05/30/2017 12:05 AM »
I don't expect development of long term on orbit main tank cryo storage because it's not critical to ITS.

It is though, for varying definitions of long term. ITS will need to be refueled over a handful of tanker flights which could take a bit of time

Not if you can live with the boil-off losses during the fueling campaign. The trade-off is between developing long-term, main tank cryo management, and launching a bit more fuel during the refueling campaign. If the fuel needed for the Mars ship is not an exact multiple of the tanker capacity, you already have some 'free' excess fuel that can go toward making up for the boil-off.
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Offline Robotbeat

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Re: IAC 2017 -- ITS v0.2
« Reply #38 on: 05/30/2017 12:07 AM »
All propellant would be used for speeding the transit (or for slowing down). There wouldn't be extra except for safety margin.
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Offline TripD

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Re: IAC 2017 -- ITS v0.2
« Reply #39 on: 05/30/2017 02:42 AM »
I think RobW was talking about the tanker.

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Re: IAC 2017 -- ITS v0.2
« Reply #40 on: 05/30/2017 02:58 AM »
I think RobW was talking about the tanker.
He was, thanks.

My thought was that, in normal use, the last tanker will have some fractional amount of prop left over after topping off the spaceship. If the spaceship had some amount of boil-off, you would just load more of the tanker's excess prop to compensate.

Having said that, if you have more than one spaceship in the same orbit, you don't really have any fractional/spare prop, because whatever is left over from tanking one spaceship can then be used in the next.

But either way, the question is: do you want to develop zero-boil-off main tanks, or can you live with (marginally) more tanker flights instead. That depends where the $ fall out in the trade.
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Offline Robotbeat

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Re: IAC 2017 -- ITS v0.2
« Reply #41 on: 05/30/2017 03:10 AM »
If you know you're going to have an extra half a tank, you can set your rendezvous orbit to a slightly higher apogee so as not to use exactly so many tanker flights to their fullest extent.
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Re: IAC 2017 -- ITS v0.2
« Reply #42 on: 05/30/2017 03:56 AM »
That's a really elegant way to get the most out of your tanker flights. Deliver exactly the right amount of [edited to correct a bad habit of saying fuel when I really mean] propellant, using any excess performance of the tanker's to go to a more energetic rendezvous orbit.

I understand now why there'd be no 'free' propellant to compensate for boil-off in the spaceship. Even though the spaceship always performs its departure burn with full tanks, any boil-off prior to leaving, while it waits in orbit with a partial prop load for more tanker flights, still translates to a longer transit time to Mars vs the same spaceship with zero-boil-off tanks.

The TANSTAAFL principle holds :). No free lunches and no free prop to compensate for boil-off either.
« Last Edit: 05/30/2017 04:00 AM by RobW »
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Offline su27k

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Re: IAC 2017 -- ITS v0.2
« Reply #43 on: 05/30/2017 04:23 AM »
Here's my idea of ITS v0.2, basically replacing the booster with another Ship:
1. The ship structure will need to be strengthened, but can reuse the tank tooling.
2. Each of the 6 vacuum engines is replaced by a cluster of 3 sea-level engines, result in 21 engines
3. The sea level thrust is 63MN, T/W at lift off is about 1.2. The thrust level is close to Nova C8 and I assume is acceptable for LC-39 flame trench.
(edit) 4. Can also reuse the Ship landing legs and get rid of the launch/landing mount concept.

Guesstimate for the Ship/Booster:
Length: ~30m
Diameter: 12m
Dry Mass: ~120t
Propellant Mass: 2500t
Raptor Engines: 21
Sea Level Thrust: 63MN

Plugin the numbers to  http://silverbirdastronautics.com/LVperform.html:
1st stage
Dry Mass: 120000
Propellent: 2500000
Thrust: 63000
Isp: 334

2nd stage
Dry Mass: 150000
Propellent: 1950000
Thrust: 31000
Isp: 382

Gives expendable performance:
Launch Site:     Cape Canaveral / KSC
Destination Orbit:     200 x 200 km, 28 deg
Estimated Payload:     193412 kg
95% Confidence Interval:     140753 - 256049 kg
« Last Edit: 05/30/2017 05:29 AM by su27k »

Offline Nathan2go

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Re: IAC 2017 -- ITS v0.2
« Reply #44 on: 05/30/2017 05:08 AM »
The ITS as described at IAC 2016 is awesome. The only two things I think you could reasonably object to are the raw size (impracticality large thrust for LC39a and Brownsville), the ambitious landing tech, and maybe the lack of abort.
...
But the basic idea behind ITS just kicks most architectures' butts so hard that I don't think people have yet realized how much better this approach is. Just two stages, with a couple variants of the upper stage, is all the vehicle you need.
Yes, I agree that ITS is awesome, and of all the options we've seen thus far, is by far the most likely to dominate in a future with daily rocket launches and off-world colonies.

The issues of large size and landing tech don't worry me.  If needed, build an off-shore launch platform.  If the landing cradle doesn't work out, use proven F9 style legs instead (although the F9 landing accuracy is already good enough to straddle a flame trench); 2-stage-to-orbit rockets are not overly sensitive to a weight increase of any one piece.

I suspect the launch abort system though, will be necessary for the first couple hundred crewed flights.  Rocket explosions are just too visually compelling to be ignored by the general public, and I don't think 97% demonstrated success rate (i.e what you prove with dozens of successes) is high enough to forgo a launch abort system.

A launch abort system does not have to fundamentally change the architecture, it's just a weight/cost/complexity/testing addition.  I don't think it degrades the design too badly if the passenger section of the ITS ships is designed to separate during a launch abort, it's already a separate pressure vessel.  The unused propellant for the liquid fuel abort engines can be transferred in flight to the main propellant tanks just before MECO.

I suppose it still remains to be seen whether the ITS ship landing system will have comparable safety during entry/decent/landing as would a capsule.

Offline WBY1984

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Re: IAC 2017 -- ITS v0.2
« Reply #45 on: 05/30/2017 05:59 AM »
Why can't the entire ITS serve as an escape system? It's certainly got a lot of engines at the back to escape a failing booster?

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Re: IAC 2017 -- ITS v0.2
« Reply #46 on: 05/30/2017 06:09 AM »
Why can't the entire ITS serve as an escape system? It's certainly got a lot of engines at the back to escape a failing booster?
Not enough TWR to escape an explosion booster and engines don't ignite fast enough.

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Re: IAC 2017 -- ITS v0.2
« Reply #47 on: 05/30/2017 06:12 AM »
Carrying a LES all the way to Mars and back will cost a lot of performance. If it is deemed necessary there could be a version of tanker and a kind of capsule for up to 100 passengers crammed in for a few hours at the top. It could deliver the passengers last and top off any boiloff from the waiting time in LEO. It is one more launch per Mars flight but it would not degrade Mars performance and another LEO launch is not a very large share of the total flight cost. It would be mostly development cost for this variant.

I don't think it will be really necessary. Before large crews fly there would be hundreds of launches, not dozens and the reliability proven, hopefully.

Offline AncientU

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Re: IAC 2017 -- ITS v0.2
« Reply #48 on: 05/30/2017 10:20 AM »
I don't expect development of long term on orbit main tank cryo storage because it's not critical to ITS.

It is though, for varying definitions of long term. ITS will need to be refueled over a handful of tanker flights which could take a bit of time

Not if you can live with the boil-off losses during the fueling campaign. The trade-off is between developing long-term, main tank cryo management, and launching a bit more fuel during the refueling campaign. If the fuel needed for the Mars ship is not an exact multiple of the tanker capacity, you already have some 'free' excess fuel that can go toward making up for the boil-off.

They'll need something approaching ZBO tankage.  Recall that they are discussing assembling a 'fleet' of vessels which will all depart together.  Cannot have the first fueled suffer significant boil-off while waiting for the rest. 

Assembling in a high orbit (EML-1/2) would help greatly as the Earth's heat load would be reduced to a couple percent of what it was in LEO.

Also, when fueling on Mars, there must be some high insulating value in the spaceship tankage to avoid becoming a carbon dioxide ice block.  (Lox and liquid methane are at temps below the carbon dioxide freezing point.)
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Online Kaputnik

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Re: IAC 2017 -- ITS v0.2
« Reply #49 on: 05/30/2017 11:09 AM »
How feasible would active cooling be, using the 200kw of solar power available on the ITS?
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Offline pippin

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Re: IAC 2017 -- ITS v0.2
« Reply #50 on: 05/30/2017 12:14 PM »
How feasible would active cooling be, using the 200kw of solar power available on the ITS?
What is this "active cooling" using power? Any power you use needs to be radiated off, too, otherwise it's rather heating than cooling.

Offline stcks

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Re: IAC 2017 -- ITS v0.2
« Reply #51 on: 05/30/2017 12:32 PM »
Not if you can live with the boil-off losses during the fueling campaign. The trade-off is between developing long-term, main tank cryo management, and launching a bit more fuel during the refueling campaign.

That's a good point, but it presumes a quick enough launch cadence for refueling to be able to even make the trade. Will be interesting to see how (if) it is done

Offline envy887

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Re: IAC 2017 -- ITS v0.2
« Reply #52 on: 05/30/2017 12:50 PM »
How feasible would active cooling be, using the 200kw of solar power available on the ITS?
What is this "active cooling" using power? Any power you use needs to be radiated off, too, otherwise it's rather heating than cooling.

Refrigeration. Of course the process generates extra heat has to be radiated away.

Offline pippin

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IAC 2017 -- ITS v0.2
« Reply #53 on: 05/30/2017 12:59 PM »
How feasible would active cooling be, using the 200kw of solar power available on the ITS?
What is this "active cooling" using power? Any power you use needs to be radiated off, too, otherwise it's rather heating than cooling.

Refrigeration. Of course the process generates extra heat has to be radiated away.
Refrigeration requires a heat sink.
No such thing in space.
Yes, you can increase the temperature differential to radiators by using some high-temperature cycle to increase radiation but that increases the heat load on parts of your system quite a bit.
Even radiating away these 200kW of power is no small feat.

The one really feasible way to cool stuff in space is by shedding heated material (fuel) but that requires exactly the boiloff you want to prevent. Ok, you could make the process a bit more efficient by shedding hotter gas but I doubt that will have a lot of effect. You'd have to increase temperature quite a lot.
Let's not forget all these temperature differentials are in Kelvin so you need a lot of change to get a big result, heating up your shredded gas to hundreds or even >1000 degrees just to cool other parts, not sure that's very practical.
« Last Edit: 05/30/2017 01:00 PM by pippin »

Offline Robotbeat

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Re: IAC 2017 -- ITS v0.2
« Reply #54 on: 05/30/2017 01:09 PM »
Space is a heat sink, just an inefficient one since you have to radiate. So refrigeration is still most certainly possible.
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Offline pippin

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Re: IAC 2017 -- ITS v0.2
« Reply #55 on: 05/30/2017 01:10 PM »
Well, yes, possible, but veeeery inefficient

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Re: IAC 2017 -- ITS v0.2
« Reply #56 on: 05/30/2017 01:13 PM »
Well, yes, possible, but veeeery inefficient
Not sure what your point is. It's certainly possible to refrigerate a cryogen to liquification, especially if it's not hydrogen or helium.
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Re: IAC 2017 -- ITS v0.2
« Reply #57 on: 05/30/2017 01:15 PM »
Yea, if you've got a square kilometer of radiation surface or it's small volume or you're willing to shed a lot of gas in exchange. All as I said above.

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Re: IAC 2017 -- ITS v0.2
« Reply #58 on: 05/30/2017 01:16 PM »
Yea, if you've got a square kilometer of radiation surface or it's small volume or you're willing to shed a lot of gas in exchange. All as I said above.
No, that's hyperbole.
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Offline pippin

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IAC 2017 -- ITS v0.2
« Reply #59 on: 05/30/2017 01:19 PM »
No, it's not. ITS as shown in the early drafts was clearly already lacking radiator surface area even without trying to shed enough heat load for a phase change.
If you use tens of kW of power for refrigeration, radiating off that heat will require increasing the radiation surface area significantly- or to beef up the temperature differential with all the problems involved (use of different fluids and all)
« Last Edit: 05/30/2017 01:22 PM by pippin »

Offline Robotbeat

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Re: IAC 2017 -- ITS v0.2
« Reply #60 on: 05/30/2017 01:22 PM »
You might not need that much. If you have low heat leak (say tens or hundreds of watts), a few kilowatts would be fine. And even 10s of kilowatts is small compared to the 200kW of heat ITS already has to radiate.
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Offline john smith 19

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Re: IAC 2017 -- ITS v0.2
« Reply #61 on: 05/30/2017 01:22 PM »
A few notes.

We know SX and Musk will revise their plans as they learn more about their feasibility but they don't make wholesale changes to them based on comments by outsiders.

Zubrin's estimate of $10Bn for ITS is presumably using the US space industry cost model. That has been shown to be 6x to 10x higher than the actual cost of development for all SX work up to and including the first F9 launch . However the switch to composite tanks (unknown for reuse and at this scale) drives up the potential for "unknown unknowns" to surface

Propellant settling can be done with as little as 10 micro g of acceleration and can cut boil off by 50%. It can also facilitate phase separation and hence pumping.

The big issue is the idea of a "fleet" of ships. Without a huge number of launch pads (given each ITS to Mars needs about 4-6 tanker launches) even with fast turnaround this is going to take a substantial amount of time for  propellant loading in LEO (BTW will all the passengers be on board already for that?)

So boil off will be a serious issue for the first ones to have their propellant loaded. Settling thrust and proper orientation wrt to the Sun and the Earth can definitely help. The work on high emissivity coatings by NASA, which could let the cryo tanks radiate down to below the freezing point of both propellants is a possibility, as is an MLI "shroud" deployed while they are waiting to leave.

However I think people are forgetting that SX has historically ramped up its operations. My guess is the first ITS flight to Mars will be a very different beast than the final version, just as the F9 FT is a very different beast from the F9 that launched in 2010. 

So I'm expecting Musk to flesh out the details of SX's plans and maybe revise them in the light of the years more planning and testing they've been able to do on Red Dragon, Raptor, the big composite tanks, ECLSS and how they are going to power ISRU, but the broad architecture will remain what it is.

BTW Have people factored in the size of the fleet when scaling the ISRU hardware? Either you will need a lot of tankage on Mars or that ISRU system is going to need a lot of capacity in order to refill all those tanks from the time they touch down until the launch window back to Earth opens.

[EDIT To put radiators in perspective the ISS ones run around 60c and emit 47w/m^2 OTOH emission improves at T^4 but T is in Kelvins, not c, so running fluid through them at 120c does not raise emitted power 16x. 

I think the new high emissivity coatings that have been worked out under NASA grant will have a big role to play. They are passive and radically lower the temperature at which a body will start to absorb, rather than emit, heat

Thinking about the ConOps for a fleet of ITS suggests time is quite an important factor, for passengers, crew and propellant. I'm wondering if, rather than a whole mass of ships, they launch pairs of ITS at a time throughout the launch window. This avoids the single point failure of a lone vehicle but avoids the "traffic jam" in space of X number of ITS's, with maybe 5x that number of tankers docking and loading propellant ]
« Last Edit: 05/30/2017 01:37 PM by john smith 19 »
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Offline pippin

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IAC 2017 -- ITS v0.2
« Reply #62 on: 05/30/2017 01:26 PM »
You might not need that much. If you have low heat leak (say tens or hundreds of watts), a few kilowatts would be fine. And even 10s of kilowatts is small compared to the 200kW of heat ITS already has to radiate.
If the heat leak is that small it's not worth it. You can shed a lot of heat by simply dumping the boiloff because the boiling itself consumes so much heat.
It's only worth it if you are leaking a lot and then you have to shed all that additional heat, too  and it's not only about the heat load for the temperature differential to the condensation temperature but it's the phase change energy, too (which is probably much higher).
« Last Edit: 05/30/2017 01:28 PM by pippin »

Offline Robotbeat

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Re: IAC 2017 -- ITS v0.2
« Reply #63 on: 05/30/2017 01:35 PM »
Sounds like a hand-wavey assertion to me. If you're using trade study results from hydrogen and expecting them to apply to methane/LOx, you're likely off by at least an order of magnitude. Methane and oxygen have a much lower heat capacity per kilogram than hydrogen does, plus it takes a lot less energy to pump heat from the much warmer soft cryogen temperatures. So on both sides of the equation, you're being pushed toward active boil off mitigation being feasible for methane/LOx.
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Offline Robotbeat

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Re: IAC 2017 -- ITS v0.2
« Reply #64 on: 05/30/2017 01:36 PM »
The phase change is included in the heat leak, you shouldn't double count it.
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Offline pippin

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Re: IAC 2017 -- ITS v0.2
« Reply #65 on: 05/30/2017 01:37 PM »
Doesn't really make much difference. Because at the same time it means you lose less fuel through boiloff.
Why so complicated? Just carry some more of the stuff and you've got a nice heat sink.

Offline pippin

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Re: IAC 2017 -- ITS v0.2
« Reply #66 on: 05/30/2017 01:37 PM »
The phase change is included in the heat leak, you shouldn't double count it.
The discussion was about re-liquefying the boiloff, im not double-counting it.

Offline Robotbeat

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Re: IAC 2017 -- ITS v0.2
« Reply #67 on: 05/30/2017 01:42 PM »
The phase change is included in the heat leak, you shouldn't double count it.
The discussion was about re-liquefying the boiloff, im not double-counting it.
Yeah you are, or rather it's not worth mentioning because it's already accounted for. We're starting with a constant heat leak. That's all that needs to be considered. Phase change will take care of itself as part of the process of countering that heat leak through active measures.
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Offline pippin

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Re: IAC 2017 -- ITS v0.2
« Reply #68 on: 05/30/2017 01:46 PM »
Ok, from an energy-balance POV you are right (if it's not e.g. about re-liquefying gas for use in engines etc).
But my point still stands: if the loss is so small, why not just carry some more fuel? Why create a complex and heavy refrigeration and then have to radiate off that heat?
For small losses it's not needed, for big losses it's not practical

Offline envy887

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Re: IAC 2017 -- ITS v0.2
« Reply #69 on: 05/30/2017 02:17 PM »
ITS is going to be a low dry mass, fuel rich, low launch cost architecture. That drives the tradeoffs towards using main tank boiloff rather than re-liquefying it while waiting for tanker, at least for a while. Dragging the dry mass of liquefying hardware to Mars and back isn't ideal.

Boiloff can be used to fuel the gaseous RCS thrusters, both for attitude control and to slowly raise the staging orbit. The ship could start in a very low Earth orbit (something like 180 km) and slowly raise itself so that the fuel isn't entirely wasted.

They will need liquefying hardware at Mars, but that won't be coming back, and probably won't be designed for on-orbit operations though it will be similar. Once there are enough ships on orbit to require depots, then on-orbit ZBO cryo management will be required but can be done by dedicated hardware.

Offline matthewkantar

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Re: IAC 2017 -- ITS v0.2
« Reply #70 on: 05/30/2017 05:12 PM »
Most of the problem with boil off will be on the surface of Mars or in Earth orbit. The landing propellant load will be small and in a tank inside of a tank, therefore easier to deal with. Without going to full blown propellant depot architecture, an on-orbit refrigeration bot could be built that hangs out with ITS while in Earth orbit. The bot could be used many times. On Mars, as mentioned above, keeping the propellant conditioned will be a big job, but the weight of the gear that handles refrigeration is not as big a deal, as it will stay on Mars once it gets there.

Matthew

Offline pippin

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Re: IAC 2017 -- ITS v0.2
« Reply #71 on: 05/30/2017 05:15 PM »
And on Mars you have an atmosphere and a cold ground to use as a heat sink.

Offline Norm38

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Re: IAC 2017 -- ITS v0.2
« Reply #72 on: 05/30/2017 07:08 PM »
Without going to full blown propellant depot architecture, an on-orbit refrigeration bot could be built that hangs out with ITS while in Earth orbit. The bot could be used many times.

I had the same thought, some kind of tender that can be big (sunshade, radiators) because it doesn't have to move much.  It can keep itself fueled by tapping off the boiloff such that no dedicated tanker flights are needed for it once it's launched.
That tender could even capture any extra fuel a tanker would have left over and transfer it to another ship.

Lots of different ways to handle the problem.  And like the life support systems, I doubt ZBO hardware is needed for any of the early flights.

Online Kaputnik

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Re: IAC 2017 -- ITS v0.2
« Reply #73 on: 05/30/2017 07:11 PM »
Most of the problem with boil off will be on the surface of Mars or in Earth orbit. The landing propellant load will be small and in a tank inside of a tank, therefore easier to deal with. Without going to full blown propellant depot architecture, an on-orbit refrigeration bot could be built that hangs out with ITS while in Earth orbit. The bot could be used many times. On Mars, as mentioned above, keeping the propellant conditioned will be a big job, but the weight of the gear that handles refrigeration is not as big a deal, as it will stay on Mars once it gets there.

Matthew

Rather than a fridge-bot, perhaps a free flying mylar sunshade?
Waiting for joy and raptor

Offline john smith 19

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Re: IAC 2017 -- ITS v0.2
« Reply #74 on: 05/30/2017 08:07 PM »
Rather than a fridge-bot, perhaps a free flying mylar sunshade?
Remember though this situation has to scale.

That would be 1 sunshade per ITS to Mars.  Hence my suggestion that they launch in pairs throughout the launch window.
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Offline Ludus

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Re: IAC 2017 -- ITS v0.2
« Reply #75 on: 05/30/2017 08:30 PM »
Reading Zubrin's critique over again, he's praising Musk for everything that's similar to Mars Direct and offering suggestions on how to change everything else so it's more like Zubrin's plans.

Zubrin's plans are a pitch to NASA. Musk's are a commercial enterprise. NASA likes budgets that develop lots of specialized vehicles, it's similar to what they've always done. Musk wants both reusability and mass production of standardized designs. He wants this to rapidly scale and serve multiple purposes.

Part of what seems like a disconnect to me is that SpaceX has never shown plans for an uncrewed cargo variant of ITS, despite the implications in their plans that they'd be building 10X as many of those as anything else. That's what would launch Internet Constellation 2.0, land on Europa or move the 10:1 cargo to human ratio to Mars.

If it was clear that most of the ITS ships that land on Mars have no use whatever as habitats because they're just tanks and engines and payload farings, Zubrin wouldn't try so hard to rework the system to leave them on Mars. He's trying for something like Mars Direct's accumulation of Tuna Can habitats on Mars when that's just not the same sort of approach.

My hope for an ITS update would be some details about uncrewed cargo variants.
« Last Edit: 05/30/2017 08:37 PM by Ludus »

Offline envy887

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Re: IAC 2017 -- ITS v0.2
« Reply #76 on: 05/30/2017 09:17 PM »
Reading Zubrin's critique over again, he's praising Musk for everything that's similar to Mars Direct and offering suggestions on how to change everything else so it's more like Zubrin's plans.

Zubrin's plans are a pitch to NASA. Musk's are a commercial enterprise. NASA likes budgets that develop lots of specialized vehicles, it's similar to what they've always done. Musk wants both reusability and mass production of standardized designs. He wants this to rapidly scale and serve multiple purposes.

Part of what seems like a disconnect to me is that SpaceX has never shown plans for an uncrewed cargo variant of ITS, despite the implications in their plans that they'd be building 10X as many of those as anything else. That's what would launch Internet Constellation 2.0, land on Europa or move the 10:1 cargo to human ratio to Mars.

If it was clear that most of the ITS ships that land on Mars have no use whatever as habitats because they're just tanks and engines and payload farings, Zubrin wouldn't try so hard to rework the system to leave them on Mars. He's trying for something like Mars Direct's accumulation of Tuna Can habitats on Mars when that's just not the same sort of approach.

My hope for an ITS update would be some details about uncrewed cargo variants.

Agreed. Excellent post. Combine Tom Mueller statements that ITS will obsolete every other rocket with Elon's statement that it has to make sense economically, means that there has to be a cargo upper stage variant in the works. I can't imagine a easy way to launch free-flying satellites from the two proposed spacecraft.

It likely wasn't proposed last year because it isn't obviously critical to getting humans to Mars (although it absolutely is once you look at the whole system closer), and it competes even more directly with SLS.

Offline Norm38

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Re: IAC 2017 -- ITS v0.2
« Reply #77 on: 05/30/2017 09:27 PM »
Part of what seems like a disconnect to me is that SpaceX has never shown plans for an uncrewed cargo variant of ITS, despite the implications in their plans that they'd be building 10X as many of those as anything else. That's what would launch Internet Constellation 2.0, land on Europa or move the 10:1 cargo to human ratio to Mars.

What they've shown of ITS so far is basically just a big hollow ship with very few interior details. Manned or unmanned it's flown by computer.  So really except for replacing the big windows with big doors, how is what has been shown not a cargo hauler?

I expect something close to a 747, where the passenger and cargo models don't look much different from the outside.

Online Lars-J

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Re: IAC 2017 -- ITS v0.2
« Reply #78 on: 05/30/2017 09:51 PM »
Part of what seems like a disconnect to me is that SpaceX has never shown plans for an uncrewed cargo variant of ITS, despite the implications in their plans that they'd be building 10X as many of those as anything else. That's what would launch Internet Constellation 2.0, land on Europa or move the 10:1 cargo to human ratio to Mars.

What they've shown of ITS so far is basically just a big hollow ship with very few interior details. Manned or unmanned it's flown by computer.  So really except for replacing the big windows with big doors, how is what has been shown not a cargo hauler?

I expect something close to a 747, where the passenger and cargo models don't look much different from the outside.

Exactly. A full on cargo cargo version won't look much different than a passenger ITS. A big cargo bay that replaces the pressurized crew section, and you're done.

Online jpo234

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Re: IAC 2017 -- ITS v0.2
« Reply #79 on: 05/30/2017 10:15 PM »
Part of what seems like a disconnect to me is that SpaceX has never shown plans for an uncrewed cargo variant of ITS, despite the implications in their plans that they'd be building 10X as many of those as anything else. That's what would launch Internet Constellation 2.0, land on Europa or move the 10:1 cargo to human ratio to Mars.

What they've shown of ITS so far is basically just a big hollow ship with very few interior details. Manned or unmanned it's flown by computer.  So really except for replacing the big windows with big doors, how is what has been shown not a cargo hauler?

I expect something close to a 747, where the passenger and cargo models don't look much different from the outside.
That's basically what I thought as well. However, I suspect that there will be an additional component: a reusable tug that can move satellites from LEO to GTO. The tug remains in orbit and can be fueled by the cargo launcher.

Offline Robotbeat

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Re: IAC 2017 -- ITS v0.2
« Reply #80 on: 05/30/2017 10:29 PM »
Part of what seems like a disconnect to me is that SpaceX has never shown plans for an uncrewed cargo variant of ITS, despite the implications in their plans that they'd be building 10X as many of those as anything else. That's what would launch Internet Constellation 2.0, land on Europa or move the 10:1 cargo to human ratio to Mars.

What they've shown of ITS so far is basically just a big hollow ship with very few interior details. Manned or unmanned it's flown by computer.  So really except for replacing the big windows with big doors, how is what has been shown not a cargo hauler?

I expect something close to a 747, where the passenger and cargo models don't look much different from the outside.
That's basically what I thought as well. However, I suspect that there will be an additional component: a reusable tug that can move satellites from LEO to GTO. The tug remains in orbit and can be fueled by the cargo launcher.
Not needed, as ITS or some intermediate version could launch directly to GTO reusably.
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Online RobW

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Re: IAC 2017 -- ITS v0.2
« Reply #81 on: 05/30/2017 10:34 PM »
Part of what seems like a disconnect to me is that SpaceX has never shown plans for an uncrewed cargo variant of ITS, despite the implications in their plans that they'd be building 10X as many of those as anything else. That's what would launch Internet Constellation 2.0, land on Europa or move the 10:1 cargo to human ratio to Mars.

What they've shown of ITS so far is basically just a big hollow ship with very few interior details. Manned or unmanned it's flown by computer.  So really except for replacing the big windows with big doors, how is what has been shown not a cargo hauler?

I expect something close to a 747, where the passenger and cargo models don't look much different from the outside.
That's basically what I thought as well. However, I suspect that there will be an additional component: a reusable tug that can move satellites from LEO to GTO. The tug remains in orbit and can be fueled by the cargo launcher.


A tug like that would certainly let you squeeze extra performance out of the system, but in the early years would you have enough GTO traffic to need that? Our ITS-150 (150-ish metric tons to LEO, Tiny is a great name, but not TITS :) ) would have a lot of excess capacity, I think, to put itself and a GEOsat or two into a geostationary transfer orbit. And, since it's designed to return from Mars, landing from a GTO shouldn't be much of a challenge.

EDIT: Robot beat me to it :) But I still put forward ITS-150 as a name for mini/junior/tiny ITS.
« Last Edit: 05/30/2017 10:37 PM by RobW »
Science fiction writer, spaceflight blogger, and unrepentant technological optimist.

Offline Nathan2go

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Re: IAC 2017 -- ITS v0.2
« Reply #82 on: 05/31/2017 03:05 AM »
Exactly. A full on cargo cargo version won't look much different than a passenger ITS. A big cargo bay that replaces the pressurized crew section, and you're done.
Umm, remember the McDonnell Douglas Delta Clipper SSTO proposal?  Like the ITS ship, it was supposed to do a nose-first (or broad-side) entry, followed by rotation and tail-first landing.  As a result, it needed the payload sandwiched between the two propellant tanks for cg control.   Similarly, the ITS ship shows "densely packed cargo" in between the tanks and the loosely filled passenger area.  It has to do the rotation maneuver with full payload at Mars, and nearly empty back at Earth, so cg control is very crucial.

I think that the ITS upper passenger volume is not usable during entry; likely all passengers will be strapped into seats at the very bottom of the passenger volume, and all luggage will be moved out of the upper area too; any room dividers or bathroom fixtures up top will be very lightweight too. 

So for the cargo version, most of that upper cargo volume will also be limited to extremely lightweight items or empty space.

 see http://www.astronautix.com/d/deltaclipper.html
« Last Edit: 05/31/2017 03:07 AM by Nathan2go »

Offline Nathan2go

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Re: IAC 2017 -- ITS v0.2
« Reply #83 on: 05/31/2017 03:38 AM »
The big issue is the idea of a "fleet" of ships. Without a huge number of launch pads (given each ITS to Mars needs about 4-6 tanker launches) even with fast turnaround this is going to take a substantial amount of time for  propellant loading in LEO ...
So boil off will be a serious issue for the first ones to have their propellant loaded.
I think the cargo launches (and tanker launches for said cargo ships) will spread out over the 2 year launch interval.   While waiting for the trans-Mars departure window to open, instead of loitering in LEO, they'll park in high orbits.  For example, in NASA's recent SEP papers, they assume their Solar Electric Propulsion vehicle will park in a Lunar-Distance Highly-elliptical Earth Orbit for a short time, or in a Distant Lunar Retro Orbit for longer periods  (this high & rounds Lunar orbit needs very little station-keeping fuel, avoids the Van Allen belts, still allows a low Earth flyby departure w/ Oberth burn, but takes several weeks to efficiently get in or out of).   The Deep Space Gateway will also park in a DLRO to support Mars missions.

So if launches occur every day, the propellant from the tankers only sits in LEO for a few days before a ships takes it in (and they can transfer from tanker to tanker, so only one must wait on orbit for the ship).  The multi-month waits will all be way far out from Earth, where pointing away from the sun solves most of the boil-off problem.  I suspect some large doors will open to expose radiators, like on the Shuttle (not the kind of detail the general public would like to hear from SpaceX at this point).

When the passenger launches become so numerous that you can't pack them and their tanker launches into the departure window (a few weeks long), you can either let some of the passenger ships park a few weeks in LDHEOs, or launch a propellant depot to LEO, so the propellant launches before the window, and all passengers launch during the window.
« Last Edit: 05/31/2017 03:48 AM by Nathan2go »

Offline cuddihy

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Re: IAC 2017 -- ITS v0.2
« Reply #84 on: 06/01/2017 04:51 AM »
I think the biggest technical uncertainty about ITS is largely being handwaved here when there's no evidence that it's actually solveable. That's the use of large carbon fiber LOX tanks. They are critical to the design closing, and so far the evidence is very discouraging about how resilient they actually are.

Despite some happy talk about how the two F9 US failures and the reported early demise of the large carbon fiber LOX tank are all unrelated and not indicative of anything inherently failure prone in carbon fiber structures and LOX, it has to be recognized that not all technical problems are actually reasonably solveable.

There is every possibility that even if Raptor is a complete success ITS design will fail to close due to inability to overcome susceptibility of carbon fiber structures to failure when surrounded by or holding LOX. Unlike with Shuttle's design issues, in all likelihood there would be recognition and a new course charted by SpaceX early on. So that's good. But let's not blithely assume the design actually closes given such a glaring and fundamental risk area.

Zubrin doesn't go there, but the end result may bee closer to his vision than Musk's if they are unable to overcome this major technical hurdle.

Online jpo234

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Re: IAC 2017 -- ITS v0.2
« Reply #85 on: 06/01/2017 05:36 AM »


There is every possibility that even if Raptor is a complete success ITS design will fail to close due to inability to overcome susceptibility of carbon fiber structures to failure when surrounded by or holding LOX.

From http://www.spaceflightinsider.com/missions/commercial/rocket-lab-electron-rutherford-peter-beck-started-first-place/
Quote

the carbon composite tanks were specially designed in order to be compatible with the liquid oxygen.

So it has already been done on a smaller scale.


Offline rsdavis9

Re: IAC 2017 -- ITS v0.2
« Reply #86 on: 06/01/2017 01:59 PM »
I think the biggest technical uncertainty about ITS is largely being handwaved here when there's no evidence that it's actually solveable. That's the use of large carbon fiber LOX tanks. They are critical to the design closing, and so far the evidence is very discouraging about how resilient they actually are.

Despite some happy talk about how the two F9 US failures and the reported early demise of the large carbon fiber LOX tank are all unrelated and not indicative of anything inherently failure prone in carbon fiber structures and LOX, it has to be recognized that not all technical problems are actually reasonably solveable.

There is every possibility that even if Raptor is a complete success ITS design will fail to close due to inability to overcome susceptibility of carbon fiber structures to failure when surrounded by or holding LOX. Unlike with Shuttle's design issues, in all likelihood there would be recognition and a new course charted by SpaceX early on. So that's good. But let's not blithely assume the design actually closes given such a glaring and fundamental risk area.

Zubrin doesn't go there, but the end result may bee closer to his vision than Musk's if they are unable to overcome this major technical hurdle.

There was also a thread just for carbon fiber problems and whether it could be solved for ITS.
bob

Offline rsdavis9

Re: IAC 2017 -- ITS v0.2
« Reply #87 on: 06/01/2017 02:05 PM »
In my mind the size, etc are not the big questions.
Sure being able to use an existing launch site is important to get it done sooner.
Sure if you lose prototypes size may matter.
But here is my list of the major technical problems to implement and get right.

1. CH4-LOX raptor engine.
2. autogenous pressurization.
3. composite structure.
4. Combined fairing/US/reentry craft

-----

2. Has been done on other spacecraft but spacex has not.
4. Has an example of the shuttle.
1. Has never been done by anybody for actual flight and especially with the aggressive design of spacex. and is therefore been given the largest leadtime. They seem to have been working on it for a while.
3. Elon has stated that if composite tanks and LOX don't agree with each other they may line the tank with metal. That would obviously impact performance but maybe not that much.

bob

Online guckyfan

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Re: IAC 2017 -- ITS v0.2
« Reply #88 on: 06/01/2017 04:03 PM »
1. Has never been done by anybody for actual flight and especially with the aggressive design of spacex. and is therefore been given the largest leadtime. They seem to have been working on it for a while.

The test stand in Stennis was handed over to SpaceX operational in April 2014 and has been used for component tests since then.

3. Elon has stated that if composite tanks and LOX don't agree with each other they may line the tank with metal. That would obviously impact performance but maybe not that much.

LOX is not the problem. Using hot gaseous oxygen for pressurization is.

Offline envy887

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Re: IAC 2017 -- ITS v0.2
« Reply #89 on: 06/01/2017 05:02 PM »
3. Elon has stated that if composite tanks and LOX don't agree with each other they may line the tank with metal. That would obviously impact performance but maybe not that much.
LOX is not the problem. Using hot gaseous oxygen for pressurization is.

What does Electron use for LOX tank pressurization?

Offline ethan829

Re: IAC 2017 -- ITS v0.2
« Reply #90 on: 06/01/2017 05:18 PM »
3. Elon has stated that if composite tanks and LOX don't agree with each other they may line the tank with metal. That would obviously impact performance but maybe not that much.
LOX is not the problem. Using hot gaseous oxygen for pressurization is.

What does Electron use for LOX tank pressurization?


Helium

Offline john smith 19

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Re: IAC 2017 -- ITS v0.2
« Reply #91 on: 06/01/2017 07:38 PM »
I think the biggest technical uncertainty about ITS is largely being handwaved here when there's no evidence that it's actually solveable. That's the use of large carbon fiber LOX tanks. They are critical to the design closing, and so far the evidence is very discouraging about how resilient they actually are.
Actually HMX mentioned that composite LOX tanks were tested more than 25 years ago.
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Offline DJPledger

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Re: IAC 2017 -- ITS v0.2
« Reply #92 on: 06/01/2017 08:00 PM »
I think the biggest technical uncertainty about ITS is largely being handwaved here when there's no evidence that it's actually solveable. That's the use of large carbon fiber LOX tanks. They are critical to the design closing, and so far the evidence is very discouraging about how resilient they actually are.
Perhaps SpaceX should go to tried and tested Al-Li to build the tanks for ITS out of and up the Raptor thrust a little to compensate for higher tank mass. At least Al-Li tanks should allow ITS design to close out a lot easier.

Offline cuddihy

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Re: IAC 2017 -- ITS v0.2
« Reply #93 on: 06/01/2017 08:32 PM »

There was also a thread just for carbon fiber problems and whether it could be solved for ITS.

Please point to that thread.

Offline JasonAW3

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Re: IAC 2017 -- ITS v0.2
« Reply #94 on: 06/01/2017 09:19 PM »
I think the biggest technical uncertainty about ITS is largely being handwaved here when there's no evidence that it's actually solveable. That's the use of large carbon fiber LOX tanks. They are critical to the design closing, and so far the evidence is very discouraging about how resilient they actually are.
Perhaps SpaceX should go to tried and tested Al-Li to build the tanks for ITS out of and up the Raptor thrust a little to compensate for higher tank mass. At least Al-Li tanks should allow ITS design to close out a lot easier.

DJ, to quote Jim; "Rockets aren't Legos".

     Increase the mass in one thing, to keep the same payload, you have to increase the mass of EVERYTHING.  More mass equals more fuel needed for a longer flight, which requires bigger tanks, which requires more fuel, etc and so forth.

     The idea is to reach a happy medium between how much mass you're putting into orbit, versus how much mass you have to actually boost.  When you get to truly monster sized rockets like the ITS or Sea Dragon, this ratio isn't quite as critical, but it IS still a factor to be considered.
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Offline rsdavis9

Re: IAC 2017 -- ITS v0.2
« Reply #95 on: 06/02/2017 11:49 AM »

There was also a thread just for carbon fiber problems and whether it could be solved for ITS.

Please point to that thread.

https://forum.nasaspaceflight.com/index.php?topic=42826.0
bob

Offline Robotbeat

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Re: IAC 2017 -- ITS v0.2
« Reply #96 on: 06/02/2017 01:40 PM »
All these carbon fiber questions are solvable. There are solutions for each and every problem.

A metal liner, as Musk mentioned, would solve the oxygen compatibility problem.
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Offline Ludus

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Re: IAC 2017 -- ITS v0.2
« Reply #97 on: 06/03/2017 08:59 PM »
Part of what seems like a disconnect to me is that SpaceX has never shown plans for an uncrewed cargo variant of ITS, despite the implications in their plans that they'd be building 10X as many of those as anything else. That's what would launch Internet Constellation 2.0, land on Europa or move the 10:1 cargo to human ratio to Mars.

What they've shown of ITS so far is basically just a big hollow ship with very few interior details. Manned or unmanned it's flown by computer.  So really except for replacing the big windows with big doors, how is what has been shown not a cargo hauler?

I expect something close to a 747, where the passenger and cargo models don't look much different from the outside.

Exactly. A full on cargo cargo version won't look much different than a passenger ITS. A big cargo bay that replaces the pressurized crew section, and you're done.

If that simpler cargo variant is the default, the crewed "Heart of Gold" might just involve replacing cargo modules with self contained habitat modules. Zubrin's concerns about the waste of hauling all that lifesupport back to earth when it's more useful on Mars could then be easily addressed. You'd just leave all or some of the habitat modules on Mars depending on the need for return passengers.

Having the life support divided into several redundant self sufficient sections is appropriate anyway. They'd be like a stack of Zubrin's tuna cans. The internal layout could vary as needed but it wouldn't be a bad thing to have a standardized mass producible plug and play habitat module.

I don't know how the big bay window works with this but if it's important it can probably be done.

Offline RonM

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Re: IAC 2017 -- ITS v0.2
« Reply #98 on: 06/04/2017 04:35 PM »
Part of what seems like a disconnect to me is that SpaceX has never shown plans for an uncrewed cargo variant of ITS, despite the implications in their plans that they'd be building 10X as many of those as anything else. That's what would launch Internet Constellation 2.0, land on Europa or move the 10:1 cargo to human ratio to Mars.

What they've shown of ITS so far is basically just a big hollow ship with very few interior details. Manned or unmanned it's flown by computer.  So really except for replacing the big windows with big doors, how is what has been shown not a cargo hauler?

I expect something close to a 747, where the passenger and cargo models don't look much different from the outside.

Exactly. A full on cargo cargo version won't look much different than a passenger ITS. A big cargo bay that replaces the pressurized crew section, and you're done.

If that simpler cargo variant is the default, the crewed "Heart of Gold" might just involve replacing cargo modules with self contained habitat modules. Zubrin's concerns about the waste of hauling all that lifesupport back to earth when it's more useful on Mars could then be easily addressed. You'd just leave all or some of the habitat modules on Mars depending on the need for return passengers.

Having the life support divided into several redundant self sufficient sections is appropriate anyway. They'd be like a stack of Zubrin's tuna cans. The internal layout could vary as needed but it wouldn't be a bad thing to have a standardized mass producible plug and play habitat module.

Good idea.

I don't know how the big bay window works with this but if it's important it can probably be done.

The nose of the spacecraft can keep the windows and be the habitat for a minimal flight crew. Its ogive shape makes loading large cargo awkward. Could be used for exploration missions with say about a dozen crew. Then everything else is in cargo modules.

Offline UberNobody

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Re: IAC 2017 -- ITS v0.2
« Reply #99 on: 06/07/2017 07:17 AM »
There are several things that need to be considered when considering what route to take for ITS development:

First, what is the optimal size for long term Mars colonization?

Digging into Musk's thought process a bit, I'd say he already has an eye on larger rockets than what was shown off in September.  We've heard 200 passengers from him and even 1000 passengers (on the wait but why blog).  Something more than just a stretch can provide.  Such gigantic rockets are out of the question for initial development.

This tells us something important: the first ITS will not be the "final" rocket that reaches the goal of 1M people on Mars.

Knowing this, what can be developed quickly, while still meeting the requirements for the first 8-10 years of colonization?

Not only does Elon want to move fast getting to Mars, he wants to move fast on the economics as well.  This is why we saw a 12m, 120m tall rocket at IAC.  For a long time, we heard about 100 tons to Mars as the goal, but then he showed off 300 tons.  There must be significant gains to be had going from 100 to 300.  If the first rocket is smaller than what was shown, it won't be smaller than 100mt to the surface of Mars.

On the time scale Musk wants, 39A is the only option for launching the first ITS.  The time/effort required to beef up 39A has to be considered for anything beyond about 12mlbf.  It may prove to be the long-pole of development if the initial rocket exceeds that thrust.

Once you've figured out the size of your initial rocket, how can you affordably build up a flight history to work out the kinks before sending humans to Mars?

A few orbital test flights and 1 unmanned trip to Mars may not be enough to prove out the reliability to where you are comfortable sending people.  That is where launching the global satellite internet constellation comes in.  It's the only real demand that can be met by such a large rocket in the near-term.


Putting it all together, this is the development timeline I see:

1: A somewhat squat BFR is developed with a slightly oversized spaceship/2nd stage.  It has a lift-off thrust slightly less than 12mlbf, and a payload to LEO/Mars of 100mt-150mt.  It will start by launching the satellite constellation to gain confidence in the design.  The first humans to land on Mars will use this rocket.

2: A few years after the first manned landing, as upgrades are made to 39A, the booster is stretched until you are volume-limited on the spaceship or run out of room for more engines.  180mt-240mt payload.

3: Several years after that, a new launch facility is constructed, along with the factory and infrastructure for truly huge BFRs.  Closer to being the 747s of space, these mega-rockets (450mt+) will get us to a 1M person colony on Mars.


Offline DJPledger

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Re: IAC 2017 -- ITS v0.2
« Reply #100 on: 06/07/2017 08:04 AM »
Future versions of the ITS system larger than the one announced at IAC2016 will need a larger version of Raptor to keep the engine nos. of 42 on booster and 9 on ship. 42 engines on a booster is already pushing it and I just can't imagine a rocket with ~100 FFSC engines on the bottom of it. Just far too many highly stressed parts to go wrong. Also EM likes the no. 42. SpaceX will have the funds to dev. a larger version of Raptor once the initial ITS system is in service and their sat. constellation is bringing in revenue.

Once you have the design for ITS closed out just scale it up for future larger versions.

Online rakaydos

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Re: IAC 2017 -- ITS v0.2
« Reply #101 on: 06/08/2017 07:05 AM »
Future versions of the ITS system larger than the one announced at IAC2016 will need a larger version of Raptor to keep the engine nos. of 42 on booster and 9 on ship. 42 engines on a booster is already pushing it and I just can't imagine a rocket with ~100 FFSC engines on the bottom of it. Just far too many highly stressed parts to go wrong. Also EM likes the no. 42. SpaceX will have the funds to dev. a larger version of Raptor once the initial ITS system is in service and their sat. constellation is bringing in revenue.

Once you have the design for ITS closed out just scale it up for future larger versions.
42 engines isnt THAT much.

It's only about 2 of these strapped together:
« Last Edit: 06/08/2017 07:07 AM by rakaydos »

Online Ictogan

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Re: IAC 2017 -- ITS v0.2
« Reply #102 on: 06/08/2017 07:17 AM »
Future versions of the ITS system larger than the one announced at IAC2016 will need a larger version of Raptor to keep the engine nos. of 42 on booster and 9 on ship. 42 engines on a booster is already pushing it and I just can't imagine a rocket with ~100 FFSC engines on the bottom of it. Just far too many highly stressed parts to go wrong. Also EM likes the no. 42. SpaceX will have the funds to dev. a larger version of Raptor once the initial ITS system is in service and their sat. constellation is bringing in revenue.

Once you have the design for ITS closed out just scale it up for future larger versions.
42 engines isnt THAT much.

It's only about 2 of these strapped together:

Only if you either count single four-chamber engines as four engines or if you count the Verniers. Otherwise there is only one engine per R7/Soyuz first stage/booster.

Online GWH

Re: IAC 2017 -- ITS v0.2
« Reply #103 on: 06/08/2017 04:07 PM »
Future versions of the ITS system larger than the one announced at IAC2016 will need a larger version of Raptor to keep the engine nos. of 42 on booster and 9 on ship. 42 engines on a booster is already pushing it and I just can't imagine a rocket with ~100 FFSC engines on the bottom of it. Just far too many highly stressed parts to go wrong. Also EM likes the no. 42. SpaceX will have the funds to dev. a larger version of Raptor once the initial ITS system is in service and their sat. constellation is bringing in revenue.

Once you have the design for ITS closed out just scale it up for future larger versions.

I have a really hard time seeing the booster needing to be larger.  Consider 1 booster per pad, 2 flights per week (100 per year) gives a 10 year life of each booster for 1000 flights in that 10 year period, requiring 1 replacement tanker per year.  That would be enough for a total of 33 ITS ships to Mars per synod (2 year period), 63,460mT of propellant in LEO, & 9,900mT cargo.
That would put production frequency of boosters & tankers would be at a very low level, but a strain on producing enough ITS ships, although the intent is 12 Mars trips per lifetime (24 years). Booster use however would be at a pretty ideal point of frequency of use vs life duration.

So the limiting factor here wouldn't be booster and tanker size IMO, but rather the Mars transport size, frequency of crew transfer vehicles and number of uses. In space construction of gigantic in space only transport and shuttle craft to and from surface would probably be much more cost effective then going to a larger booster.

« Last Edit: 06/08/2017 05:57 PM by GWH »

Offline Robotbeat

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Re: IAC 2017 -- ITS v0.2
« Reply #104 on: 06/08/2017 05:02 PM »
They could just build a bigger spaceship (that can still be orbited in one piece) and require more refueling flights.
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Offline matthewkantar

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Re: IAC 2017 -- ITS v0.2
« Reply #105 on: 06/08/2017 05:57 PM »
9,900 metric tons, so half of the capacity of one modern container ship.

Matthew

Edit: more like a quarter of the capacity.
« Last Edit: 06/08/2017 06:03 PM by matthewkantar »

Offline JasonAW3

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Re: IAC 2017 -- ITS v0.2
« Reply #106 on: 06/08/2017 10:02 PM »
9,900 metric tons, so half of the capacity of one modern container ship.

Matthew

Edit: more like a quarter of the capacity.

Personally, I rather liked the picture someone did a year or so ago, of rockets on their sides being loaded with conex containers. 

That's sort of how I envision the cargo variant to be loaded anyway.
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Offline Robotbeat

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Re: IAC 2017 -- ITS v0.2
« Reply #107 on: 06/09/2017 12:56 AM »
I susp XY they'd still use something like the standard aluminum containers used for air freight.
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Offline ChrisWilson68

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Re: IAC 2017 -- ITS v0.2
« Reply #108 on: 06/09/2017 04:03 AM »
Exactly. A full on cargo cargo version won't look much different than a passenger ITS. A big cargo bay that replaces the pressurized crew section, and you're done.
Umm, remember the McDonnell Douglas Delta Clipper SSTO proposal?  Like the ITS ship, it was supposed to do a nose-first (or broad-side) entry, followed by rotation and tail-first landing.  As a result, it needed the payload sandwiched between the two propellant tanks for cg control.   Similarly, the ITS ship shows "densely packed cargo" in between the tanks and the loosely filled passenger area.  It has to do the rotation maneuver with full payload at Mars, and nearly empty back at Earth, so cg control is very crucial.

I think that the ITS upper passenger volume is not usable during entry; likely all passengers will be strapped into seats at the very bottom of the passenger volume, and all luggage will be moved out of the upper area too; any room dividers or bathroom fixtures up top will be very lightweight too. 

So for the cargo version, most of that upper cargo volume will also be limited to extremely lightweight items or empty space.

 see http://www.astronautix.com/d/deltaclipper.html

That only applies to downmass cargo.  Cargo being taken from the surface of Earth to orbit (i.e. 99% of all commercial space business today) has no CG issues.

Offline oldAtlas_Eguy

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Re: IAC 2017 -- ITS v0.2
« Reply #109 on: 06/09/2017 04:47 PM »
There is actually a thread that discussed all of the pro and con arguments about standardized containers for use not only with ITS but also touched on usage on any LV.

http://forum.nasaspaceflight.com/index.php?topic=40454.0

The general consensus is that packing the containers to a standard CG and moment arm characterization and to a certain weight category allowed for a load and go without any new analysis work with regard to the LV's flight control and aerodynamics of flight.

This was identified as the superior reason for standardized containerizing payloads to greatly reduce costs, flexibility and increased flight rates. Even when the standardized containers added some parasitic weight, up to 10% or more, to the payload. This was because the cost of launch was so low that any additional manpower for handling or analyzing a custom payload swamped the costs of launch of $/kg. Making it far cheaper to stuff it into a container even if it added 20% to the weight than to try to handle it as a custom payload which ended as more than doubling the $/kg for the payload.

Offline DAZ

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Re: IAC 2017 -- ITS v0.2
« Reply #110 on: 06/09/2017 09:49 PM »
Exactly. A full on cargo cargo version won't look much different than a passenger ITS. A big cargo bay that replaces the pressurized crew section, and you're done.
Umm, remember the McDonnell Douglas Delta Clipper SSTO proposal?  Like the ITS ship, it was supposed to do a nose-first (or broad-side) entry, followed by rotation and tail-first landing.  As a result, it needed the payload sandwiched between the two propellant tanks for cg control.   Similarly, the ITS ship shows "densely packed cargo" in between the tanks and the loosely filled passenger area.  It has to do the rotation maneuver with full payload at Mars, and nearly empty back at Earth, so cg control is very crucial.

I think that the ITS upper passenger volume is not usable during entry; likely all passengers will be strapped into seats at the very bottom of the passenger volume, and all luggage will be moved out of the upper area too; any room dividers or bathroom fixtures up top will be very lightweight too. 

So for the cargo version, most of that upper cargo volume will also be limited to extremely lightweight items or empty space.

 see http://www.astronautix.com/d/deltaclipper.html

That only applies to downmass cargo.  Cargo being taken from the surface of Earth to orbit (i.e. 99% of all commercial space business today) has no CG issues.

Iím not so sure about this only applying to down mass cargo.  If you donít take CG and cargo mass into account you could end up with no viable abort situations on an inherently reusable vehicle.  This is kind of the equivalent of a plane taking off with more gross weight than it can land with.  If you are willing to use your reusable vehicle in this manner then so be it.

Offline Lumina

Re: IAC 2017 -- ITS v0.2
« Reply #111 on: 06/17/2017 06:15 AM »
No, it's not. ITS as shown in the early drafts was clearly already lacking radiator surface area even without trying to shed enough heat load for a phase change.
.....

If you are referring to the IAC 2016 version of ITS, what's stopping that design from using most of the backside of the solar panels as radiators?

Offline colbourne

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Re: IAC 2017 -- ITS v0.2
« Reply #112 on: 06/17/2017 07:29 AM »
There is actually a thread that discussed all of the pro and con arguments about standardized containers for use not only with ITS but also touched on usage on any LV.

http://forum.nasaspaceflight.com/index.php?topic=40454.0

The general consensus is that packing the containers to a standard CG and moment arm characterization and to a certain weight category allowed for a load and go without any new analysis work with regard to the LV's flight control and aerodynamics of flight.

This was identified as the superior reason for standardized containerizing payloads to greatly reduce costs, flexibility and increased flight rates. Even when the standardized containers added some parasitic weight, up to 10% or more, to the payload. This was because the cost of launch was so low that any additional manpower for handling or analyzing a custom payload swamped the costs of launch of $/kg. Making it far cheaper to stuff it into a container even if it added 20% to the weight than to try to handle it as a custom payload which ended as more than doubling the $/kg for the payload.
I don't think we need to consider the container as wasted weight. They will be very valuable on Mars as raw materials or  used for construction of the base in their original format.

Offline Jcc

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Re: IAC 2017 -- ITS v0.2
« Reply #113 on: 06/17/2017 04:24 PM »
No, it's not. ITS as shown in the early drafts was clearly already lacking radiator surface area even without trying to shed enough heat load for a phase change.
.....

If you are referring to the IAC 2016 version of ITS, what's stopping that design from using most of the backside of the solar panels as radiators?

The solar panels shown seem to deploy by rolling out from a very compact volume. It is not clear to me how radiators would attach to the back of those, but maybe others would know how to do that.

Offline Nomadd

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Re: IAC 2017 -- ITS v0.2
« Reply #114 on: 06/17/2017 04:35 PM »
There is actually a thread that discussed all of the pro and con arguments about standardized containers for use not only with ITS but also touched on usage on any LV.

http://forum.nasaspaceflight.com/index.php?topic=40454.0

The general consensus is that packing the containers to a standard CG and moment arm characterization and to a certain weight category allowed for a load and go without any new analysis work with regard to the LV's flight control and aerodynamics of flight.

This was identified as the superior reason for standardized containerizing payloads to greatly reduce costs, flexibility and increased flight rates. Even when the standardized containers added some parasitic weight, up to 10% or more, to the payload. This was because the cost of launch was so low that any additional manpower for handling or analyzing a custom payload swamped the costs of launch of $/kg. Making it far cheaper to stuff it into a container even if it added 20% to the weight than to try to handle it as a custom payload which ended as more than doubling the $/kg for the payload.
I don't think we need to consider the container as wasted weight. They will be very valuable on Mars as raw materials or  used for construction of the base in their original format.
I' not sure about raw materials, but I could see containers made from dis-assemblable panels that could be used for other structures. Maybe Lego could produce them. Make Lar happy.

Offline oldAtlas_Eguy

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Re: IAC 2017 -- ITS v0.2
« Reply #115 on: 06/17/2017 07:08 PM »
There is actually a thread that discussed all of the pro and con arguments about standardized containers for use not only with ITS but also touched on usage on any LV.

http://forum.nasaspaceflight.com/index.php?topic=40454.0

The general consensus is that packing the containers to a standard CG and moment arm characterization and to a certain weight category allowed for a load and go without any new analysis work with regard to the LV's flight control and aerodynamics of flight.

This was identified as the superior reason for standardized containerizing payloads to greatly reduce costs, flexibility and increased flight rates. Even when the standardized containers added some parasitic weight, up to 10% or more, to the payload. This was because the cost of launch was so low that any additional manpower for handling or analyzing a custom payload swamped the costs of launch of $/kg. Making it far cheaper to stuff it into a container even if it added 20% to the weight than to try to handle it as a custom payload which ended as more than doubling the $/kg for the payload.
I don't think we need to consider the container as wasted weight. They will be very valuable on Mars as raw materials or  used for construction of the base in their original format.
I' not sure about raw materials, but I could see containers made from dis-assemblable panels that could be used for other structures. Maybe Lego could produce them. Make Lar happy.
See the discussion on standardized containers and the usability of these containers at Mars.
http://forum.nasaspaceflight.com/index.php?topic=40454.0

Also it discusses features that would be extremely useful especially for self contained pressurized containers to minimize supplies offloading, etc at Mars. Using a CBM like port the triangle pie piece shaped containers would be connected to the habitat one at a time creating a complete pie so that if the supplies are organized correctly they are removed as needed by the colonists. Thus the containers also function asd the storage space once at Mars. Once all the containers are empty the result is more habitation space for colonists. Each Pie of containers adds 400m^3 of volume to the colony. There are ~ three layers of containers in each ITS. But not all layers would be pressurized containers.

Offline gongora

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Re: IAC 2017 -- ITS v0.2
« Reply #116 on: 06/17/2017 08:46 PM »
Quick question...do we have a reputable source actually saying Elon is going to speak at IAC, or is everyone assuming that based on the approximate timing for his update?

Offline oldAtlas_Eguy

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Re: IAC 2017 -- ITS v0.2
« Reply #117 on: 06/17/2017 11:43 PM »
Quick question...do we have a reputable source actually saying Elon is going to speak at IAC, or is everyone assuming that based on the approximate timing for his update?
The only item that points to the, IAC is the statement that he would have an update in 3 or 4 months which would put it at about the IAC plus it would be 1 year point and a good place to give an update. But no, I don not think there has been any substantial statement saying exactly when or what venue.

Online russianhalo117

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Re: IAC 2017 -- ITS v0.2
« Reply #118 on: 06/17/2017 11:53 PM »
Quick question...do we have a reputable source actually saying Elon is going to speak at IAC, or is everyone assuming that based on the approximate timing for his update?
The only item that points to the, IAC is the statement that he would have an update in 3 or 4 months which would put it at about the IAC plus it would be 1 year point and a good place to give an update. But no, I don not think there has been any substantial statement saying exactly when or what venue.
his name and presentation abstract is not in the latest version of the IAC schedules.
Only unassgined slot is the 0830-0930 Friday slot for Late Breaking News before closing ceremony events later that day.

Online jpo234

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Re: IAC 2017 -- ITS v0.2
« Reply #119 on: 07/11/2017 07:29 AM »
https://twitter.com/elonmusk/status/884664723429498880

Quote
Quote
I know some of us sound like a broken record by now, but can we get a real estimate on when the big Mars update will be?
Maybe the upcoming IAC in Adelaide
« Last Edit: 07/11/2017 10:50 AM by jpo234 »

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