Author Topic: IAC 2017 -- BFR v0.2 - DISCUSSION THREAD 1 (Pre-and-During Speech)  (Read 112734 times)

Online AncientU

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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.

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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: 09/29/2017 01:41 PM by Chris Bergin »
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Online 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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Online 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.



Offline 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 »
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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 »

Online 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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Online 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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Offline 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

Online 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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Offline 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 »
You want to be inspired by things. You want to wake up in the morning and think the future is going to be great. That's what being a spacefaring civilization is all about. It's about believing in the future and believing the future will be better than the past. And I can't think of anything more exciting than being out there among the stars.

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 »

Online 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.

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