Author Topic: 30 tonnes to TLI, L2 rendezvous  (Read 9911 times)

Offline kraisee

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Re: 30 tonnes to TLI, L2 rendezvous
« Reply #20 on: 12/14/2008 06:10 PM »
I haven't got a lot of time to do a more comprehensive review, but a couple of points stand out on first glance:

1) 5-seg SRB's still need to be developed.   Adds to cost and schedule.

2) 10m tanking requires extensive changes at MAF and KSC to support.   Adds to cost and schedule.

3) Totally new tanking configuration (common bulkhead and SRB mount above all tanking) will be a noticeably larger design challenge than current Ares-V Core or Jupiter Core.   Adds to cost and schedule.

4) RS-68A won't be available until 2012 for USAF.   Only at that point NASA can start qualifying it for human use.   Don't expect that before 2016 at the earliest.   If the initial vehicle requires them, the gap will be no shorter than Ares-I.   Adds to cost and schedule.


Together these are not going to reduce the budget by much.   You really only save the costs of developing one stage and a second SRB config.   That's going to mean the schedule doesn't change a lot either.

In return, you've halved the performance of the Lander.

It's too early to say for certain (I'd have to run a lot of numbers and I just don't have the time right now), but my initial reaction is this isn't going to be a very effective compromise.   Needs more study though.

Ross.
« Last Edit: 12/14/2008 06:11 PM by kraisee »
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Offline simonbp

Re: 30 tonnes to TLI, L2 rendezvous
« Reply #21 on: 12/16/2008 03:22 AM »
Thanks for your comments Ross, but you know I'm going to disagree... ;)

1) 5-seg SRB's still need to be developed.   Adds to cost and schedule.

No, 5-seg RSRM is already developed and paid for, and will be static fired in spring 2009. It would be wasting money not to use it.

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2) 10m tanking requires extensive changes at MAF and KSC to support.   Adds to cost and schedule.

3) Totally new tanking configuration (common bulkhead and SRB mount above all tanking) will be a noticeably larger design challenge than current Ares-V Core or Jupiter Core.   Adds to cost and schedule.

Not totally new (S-II had a 10-m LOX/LH2 common bulkhead 40 years ago!), and _any_ core stage is going to require significant redesign. Direct will require a lot of structural compromises to shoehorn a new use into an old design, just like the Ares I first stage. Money and time will be saved in the long run by by designing a proper stage from scratch. Besides, the 10-m, common bulkhead stage is about the same size as the S-IC, the stage MAF and the VAB were built around.

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4) RS-68A won't be available until 2012 for USAF.   Only at that point NASA can start qualifying it for human use.   Don't expect that before 2016 at the earliest.   If the initial vehicle requires them, the gap will be no shorter than Ares-I.   Adds to cost and schedule.

Ares Dual Launch is explicitly a beyond-LEO architecture, relying on commercial operators for LEO operations. Since Altair won't be ready before 2018 by any stretch of the imagination, the rockets aren't needed until 2016 anyway. (Besides, you could probably get away with using basic RS-68s, but if the USAF already has the new ones...)

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In return, you've halved the performance of the Lander.

What? No I haven't, it just has a smaller propellant load because of the delta V bonus from the lunar flyby, and not having to LOI the Orion. I actually bumped up the dry mass of both the ascent and descent stages by a tonne each to account for the longer transit times. Even then, it has ~4 tonnes of cargo/EVA allocation/margin. The upper stage is purposely the smallest it can be, so bumping up its mass by 10-20 tonnes should add even more margin (and still have no gravity losses).

In short, Ares Dual Launch is cheaper than the baseline (no ridiculously large Ares V and support equipment), and more optimised than Direct.

Simon ;)
« Last Edit: 12/16/2008 03:27 AM by simonbp »

Offline Steven Pietrobon

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Re: 30 tonnes to TLI, L2 rendezvous
« Reply #22 on: 12/16/2008 06:03 AM »
Can you show what's behind the fairings?
Akin's Laws of Spacecraft Design #1:  Engineering is done with numbers.  Analysis without numbers is only an opinion.

Offline PaulL

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Re: 30 tonnes to TLI, L2 rendezvous
« Reply #23 on: 12/16/2008 09:47 AM »
Would the CLV version really require an upper stage to get Orion to LEO?  That seems odd, considering that the J-120 can put Orion + 23 mT into LEO without an upper stage.

No, no, you're missing the whole point of the architecture. The basic con-ops plan would be:

1) First launch with hypergolic lander directly injects it to TLI.
2) After a lunar swingby, the lander arrives at L2.
3) If everything is OK with the lander, the crew is launched on the second rocket to a ~120 nm orbit.
4) If everything checks out on the Orion, the upper stage reignites and sends the crew to TLI.
5) The crew also do a lunar swingby, and the Orion performs the ~0.3 km/s L2OI burn.
6) The Orion rendezvous and docks with the lander, and the crew transfer over.
7) The lander uses its descent stage to first go to ~100 nm LLO, and then to the lunar surface.
8) SCIENCE!!!
9) The ascent stage launches first to ~100 nm LLO, and then to L2.
10) The ascent stage rendezvous and docks with the Orion, and the crew transfer.
11) The Orion performs the ~0.3 km/s TEI burn, followed by a lunar swingby.
12) Orion reenters the Earth's atmosphere. Champagne is uncorked.

Point being, no multi-day LEO loitering, no loitering anywhere with cryogenics, and no thrusts while docked. (Unlike both CxP baseline and Direct)

Oh, if really wanted to launch an Orion to ISS with an Ares DL, take off the SRBs and offload ~40% of the propellant. But just buying a Dragon/Falcon 9 would probably be cheaper...

Simon ;)

Simon, what are your transit times:

Cargo flight from LEO to L2?
CEV flight from LEO to L2?
LSAM from L2 to lunar surface?
Ascent stage from lunar surface to L2?
CEV from L2 to earth surface?

Offline simonbp

Re: 30 tonnes to TLI, L2 rendezvous
« Reply #24 on: 12/16/2008 07:02 PM »
Can you show what's behind the fairings?

Same EDS, but with a lander.

Simon, what are your transit times:

Cargo flight from LEO to L2?
CEV flight from LEO to L2?
LSAM from L2 to lunar surface?
Ascent stage from lunar surface to L2?
CEV from L2 to earth surface?

It depends on the particular profile you use; L1 lunar swingby has shorter transit times, but large delta V, and isn't as useful for trans-Mars injection than L2. Also, you can get to L2 quicker if you directly fly to it with a swingby, but the Orion SM would have to be enlarged in order to do the direct both ways (though Ares DL would still easily be able to inject it). So, here's both that and the upper limit, L2 swingby:

LEO -> L2 swingby:212 hr3.47 km/s TLI+L2OI
LEO -> L2 direct:96 hr4.38 km/s TLI+L2OI
L2 -> LLO (and visa versa):72 hr0.78 km/s
48 hr0.87 km/s
24 hr1.33 km/s
L2 -> Rentry:96 hr1.23 km/s TEI
212 hr0.33 km/s TEI

So, for the crew the max is ascent/checkout (~3 hr), L2 swingby (212 hr), low-energy transfer to LLO (72 hr), and descent (~7 hr), for a total of about 12 days from launch to walking on the moon. A more likely path is direct to L2 and 48 hr transit to LLO takes 6.4 days, surface-to-surface...

Simon ;)

Offline renclod

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Re: 30 tonnes to TLI, L2 rendezvous
« Reply #25 on: 12/17/2008 08:23 AM »
Simon,

What are the options if, after the TLI burn, Orion suffers a failure of its main propulsion ?
(Altair is far away, at L2. No lifeboat.)

With AUX thrusters only (say 8 x 150 lbf):

- continue nominal to swingby and L2 insertion, etc. ?
- change trajectory to free return around the moon a la Apollo 13 ?
- other options ?


Offline simonbp

Re: 30 tonnes to TLI, L2 rendezvous
« Reply #26 on: 12/17/2008 05:05 PM »
Simon,

What are the options if, after the TLI burn, Orion suffers a failure of its main propulsion ?
(Altair is far away, at L2. No lifeboat.)

With AUX thrusters only (say 8 x 150 lbf):

- continue nominal to swingby and L2 insertion, etc. ?
- change trajectory to free return around the moon a la Apollo 13 ?
- other options ?

Well, the direct L2 trajectory is a free-return (with maybe a few TCMs along the way), so no worries there. If you're on the swingby and don't make the burn at perilune (just ~150 m/s, so easy for the thrusters), then thing get "interesting", as you're on track to go heliocentric! In that case, the lander would be lifeboat/tugboat, as it would need to be remotely flown into rendezvous with the Orion, dock with it, and perform a TEI thrust.

Incidentally, the Orion in the current baseline can get in a similar jam post docking with the ascent stage; I believe the plan is then to ues the thrusters as the SPS for TEI (they have a common prop tank).

Simon ;)
« Last Edit: 12/17/2008 05:06 PM by simonbp »

Offline simonbp

Re: 30 tonnes to TLI, L2 rendezvous
« Reply #27 on: 01/07/2009 07:30 PM »
I think I'm leaning towards this direction now: Separated bulkheads on Core Stage (to assuage any doubts), 10m upper stage (less faring mass with Altair), for a total of ~35,000 kg to TLI. I'm also leaning to L1 rendezvous, with Orion on a free-return trajectory...

Simon ;)

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