Author Topic: Shuttle Mission to Moon?  (Read 6182 times)

Offline Spacely

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Shuttle Mission to Moon?
« on: 11/14/2005 07:29 am »
From what I understand, the Shuttle can not fly outside of earth orbit due to A. Lack of fuel and B. Thermal protection and wings are rated for reentry at 17,500 mph, rather than the 25,000+ experienced on a return from Lunar orbit.

However...

Would it be possible to send a Shuttle up to LEO, and then have it dock with an external fuel tank that has been sent up seperately?

The shuttle could then fire its SSMEs for Lunar rendevous, and fire them again for Lunar Orbit Insertion. Once there, the Shuttle could open its payload doors and release a lunar lander.

For the return to Earth, the shuttle could fire the SSMEs again, and then a final time once near Earth to slow down to 17,500.

Has any study ever been done for a mission like this?

Online Chris Bergin

RE: Shuttle Mission to Moon?
« Reply #1 on: 11/14/2005 07:53 am »
I believe Orbiters get 'very ill' if they stay out in space for more than about a month, so I think this is a non-starter. :( I read once they lose integrity (maybe one of the engineers on here could elaborate).
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Offline Terry Rocket

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RE: Shuttle Mission to Moon?
« Reply #2 on: 11/14/2005 10:42 am »
The problem that stands out for me is you'd be taking a space plane with wings to the Moon. Seems like you'd be taking a lot of unnessasary hardware with you, especially as it won't be coming back I take it?

Offline Rocket Ronnie

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RE: Shuttle Mission to Moon?
« Reply #3 on: 11/14/2005 11:00 am »
What about a Shuttle C, or is that a bit pointless too?

Offline nethegauner

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RE: Shuttle Mission to Moon?
« Reply #4 on: 11/14/2005 11:01 am »
A shuttle entering lunar orbit? Uh, that's ... unusual ...

Actually, there were design studies in the 90s regarding a lunar mission employing the shuttle. It would have been used to deploy hardware like rocket stages in LEO which would have been assembled into a lunar vehicle. But of course, this never materialized. There was an articel in AW&ST with details. Does anyone remember that?

Offline CuddlyRocket

RE: Shuttle Mission to Moon?
« Reply #5 on: 11/14/2005 12:08 pm »
Quote
Chris Bergin - 14/11/2005  8:53 AM

I believe Orbiters get 'very ill' if they stay out in space for more than about a month.
The limit relates to the Orbiter's fuel cells, which only have enough LOX/LH2 for about 18 days. This is why there is a rush every time they go to the ISS. There are some proposals to take on power from the ISS to extend this by a bit, but there's a minimum rating for the cells - they can't be switched off. You'd need to totally redesign them, and probably have to equip the orbiter with solar cells.

I also don't think that the OMS engines have enough power to get the Shuttle out of LEO. (Strictly speaking, they'd have to be run for a period in excess of their design limits.) You could use the main engines, if there was another source of propellant. However, refuelling has never been attempted, could be dangerous, and would need new equipment.

I suspect you might need to replace the Shuttle's computers as well. I doubt they could handle the additional programming for a lunar mission as well as what they need for landing etc.

Finally, the speed of return from a lunar mission would exceed the Shuttle's design tolerances. You would therefore need some method of slowing down the Shuttle once it returned to the Earth, which adds to the weight and expense.

All in all, it's almost certainly cheaper to design and build the CEV, which will also be far more efficient as it doesn't have to carry extraneous structural and other equipment (such as the wings).

Online Chris Bergin

RE: Shuttle Mission to Moon?
« Reply #6 on: 11/14/2005 12:18 pm »
Quote
CuddlyRocket - 14/11/2005  1:08 PM

 There are some proposals to take on power from the ISS to extend this by a bit

Yep, already a reality.

Station-Shuttle Power Transfer System (SSPTS) - will be flying with Discovery on STS-121.
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Offline nethegauner

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RE: Shuttle Mission to Moon?
« Reply #7 on: 11/14/2005 12:27 pm »
Quote
Chris Bergin - 14/11/2005  2:18 PM

Quote
CuddlyRocket - 14/11/2005  1:08 PM

 There are some proposals to take on power from the ISS to extend this by a bit

Yep, already a reality.

Station-Shuttle Power Transfer System (SSPTS) - will be flying with Discovery on STS-121.
I thought we would see its premiere on STS-119?

Offline Spacely

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RE: Shuttle Mission to Moon?
« Reply #8 on: 11/14/2005 03:54 pm »
Well, if we're talking about Apollo-style lunar stays, I don't see how the Shuttle's 12-18 day mission limit would really affect a lunar mission that only lasts 6-10 days total.

And yeah, I understand the wings are ridiculous when you get to the moon, but the wings are ridiculous everywhere (except for the Earth's atmosphere, of course.)

I hadn't thought of the computer programming issue. Or the fact that the SSMEs aren't designed for several firings, let-alone mid-space refuelings. Those now strike me as the deal breakers.

Offline CuddlyRocket

RE: Shuttle Mission to Moon?
« Reply #9 on: 11/14/2005 04:29 pm »
Quote
Spacely - 14/11/2005  4:54 PM

I don't see how the Shuttle's 12-18 day mission limit would really affect a lunar mission that only lasts 6-10 days total.
True. I was thinking of the VSE planned six month long missions.

Offline t walker

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RE: Shuttle Mission to Moon?
« Reply #10 on: 11/14/2005 04:46 pm »
Quote
Spacely - 14/11/2005  8:29 AM


Would it be possible to send a Shuttle up to LEO, and then have it dock with an external fuel tank that has been sent up seperately?

The shuttle could then fire its SSMEs for Lunar rendevous, and fire them again for Lunar Orbit Insertion. Once there, the Shuttle could open its payload doors and release a lunar lander.



I dont think SSMEs sould be used twice on the same flight. They get burnt out or something, and might explode or something if you try to use them again without maintanence.

Offline Stardust9906

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RE: Shuttle Mission to Moon?
« Reply #11 on: 11/14/2005 10:01 pm »
At present they can't be restarted although a redesign seems likely for the CEV launcher which would allow restarts.  A bigger problem with Spacely's idea would be attaching the Orbiter to the second fuel tank which I don't think would be possible.

Offline Avron

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RE: Shuttle Mission to Moon?
« Reply #12 on: 11/15/2005 03:50 am »
Quote
Stardust9906 - 14/11/2005  6:01 PM

At present they can't be restarted although a redesign seems likely for the CEV launcher which would allow restarts.  A bigger problem with Spacely's idea would be attaching the Orbiter to the second fuel tank which I don't think would be possible.

Question, what is needed in the SSME design for restart? Or is that restart limited to air/orbit?

Offline darkenfast

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RE: Shuttle Mission to Moon?
« Reply #13 on: 11/15/2005 03:54 am »
Neither the CEV launcher nor the SDLV will have SSME's re-start (as far as I know).  The CEV launcher won't need it for missions to LEO, and the SDLV will use the J-2S for the upper stage, which will have re-start capability.
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Offline lmike

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RE: Shuttle Mission to Moon?
« Reply #14 on: 11/15/2005 06:14 am »
For one thing, I think, a redesign of the fuel turbopump, as it requires a specific pressure in the fuel lines for the spin-up.  Or some sort ullage re-pressurizing system for the LH2 tank.

Offline Stardust9906

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RE: Shuttle Mission to Moon?
« Reply #15 on: 11/15/2005 12:18 pm »
Quote
darkenfast - 15/11/2005  4:54 AM

Neither the CEV launcher nor the SDLV will have SSME's re-start (as far as I know).  The CEV launcher won't need it for missions to LEO, and the SDLV will use the J-2S for the upper stage, which will have re-start capability.

I'm no expert on orbital mechanics but from what I understand the second stage will need to burn a second time to achieve a stable orbit.

There's a diagram at http://forum.nasaspaceflight.com/forums/thread-view.asp?tid=310&start=1

Granted this is using the J2 engine so things may have changed for the SSME.

Offline nacnud

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RE: Shuttle Mission to Moon?
« Reply #16 on: 11/15/2005 12:45 pm »
Are you refering to the second stage of the CLV?

The CEV OMS might provide the thrust for this, as on the STS.

Offline Stardust9906

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RE: Shuttle Mission to Moon?
« Reply #17 on: 11/15/2005 07:07 pm »
Yes it's the CLV I was talking about.

Offline simcosmos

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RE: Shuttle Mission to Moon?
« Reply #18 on: 11/16/2005 04:13 pm »
Quote
Stardust9906 - 15/11/2005  1:18 PM

Quote
darkenfast - 15/11/2005  4:54 AM

Neither the CEV launcher nor the SDLV will have SSME's re-start (as far as I know).  The CEV launcher won't need it for missions to LEO, and the SDLV will use the J-2S for the upper stage, which will have re-start capability.

I'm no expert on orbital mechanics but from what I understand the second stage will need to burn a second time to achieve a stable orbit.

There's a diagram at http://forum.nasaspaceflight.com/forums/thread-view.asp?tid=310&start=1

Granted this is using the J2 engine so things may have changed for the SSME.

Hello

What started being about taking the Shuttle to the Moon (and back) is now about engines for the CLV, hehe

There are several ways of placing something in orbit and they depend of:
- launch vehicle
- payload
- other constraints (such as launch windows, specific mission objectives, etc)


For a typical ISS mission (cargo transport or crew rotation), several sources (links to some of those documents are available in these forums), have already suggested two mission profiles:


From here and using my limited point of view, it seems that the CLV (SRB launcher) might place the CEV (manned or cargo version) or an ATV concept / other payload in a sub-orbital trajectory: in this case, this means that the highest point of the orbit should be near the target (ISS) altitude and, the lowest point, inside Earth's denser atmosphere.

Such trajectory would make the CLV's second stage reenter and disintegrate (similar to what happens with the ET in STS flights). Of course that the CEV / ATV / payload will have to make an engine burn on that highest orbital point in order to bring its lowest point above the denser atmosphere, in order to start the synchronization with ISS and by, on a given moment, doing a burn for the final transfer and rendezvous manoeuvre.


By the way: my humble opinion is that using a modified version of the SSME is perhaps too much "overkill" for an upper CLV stage... Perhaps it would be better to keep the J-2S (if it will be used in fact) for upper stages and an expendable / simplified  SSME just for the ET core of the heavy lifter, do not know... It seems that NASA plans to use too many engines when fewer choices would probably bring advantages from the point of "mass production"... This argument could also have another extreme point of view, for example, would it be an advantage to invest just in SSME variants for all stages (ET core, CLV upper, heavy lifter upper...)?

Anyway, like written above, for a nominal LEO mission there "should not strictly" exist the need of using the CLV's second stage engine more than once: stable orbital insertion and orbital manoeuvres can be done with the "payload's" engine(s). This assuming that the second stage's engine is non-restartable.  

However, at least in the space simulator, it is a little tempting to make the CLV's upper stage engine capable of being used more than once… This would allow for a kind of temporary space tug saving the “fuel”/ resources of the payload (CEV, ATV, etc) for more demanding missions given that stable orbital insertion and alignment errors would then be handled by the second stage, hummmm… And there have been some talks here and in other discussion places about RCS in the CLV / new launch vehicle upper stages… hummm :)

The big question is: will or will not the CLV's second stage engine (whatever it is... for the latest news it seems that it will be a modified SSME... but who knows?) capable of multiple starts? The answer to that question will automatically hint about possible mission profiles.




To end: dear readers, if this all (orbital mechanics) seems confusing to you, there is a very easy way to see (I mean really see!) how these things work: I could organize a live space mission and transmit it to my LivePics page (see my site's top right side or see the Orbiter section – left menu – then Live Mission – top menu).

I would use a space simulator ( www.orbitersim.com ) and  transmit, to my Live Mission page, images (each 10s) showing the SRB Launcher (CLV) putting some payload into Earth's orbit (ATV concept or a CEV concept) and then would do the required operations necessary to rendezvous and dock with ISS. And if people are inclined I could also use a voice software such as Ventrilo ( www.ventrilo.com ) to explain, step by step what was going on and people would also be able to make questions… Just presenting again this suggestion ;)

António
my pics @ flickr

Offline Stardust9906

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RE: Shuttle Mission to Moon?
« Reply #19 on: 11/16/2005 10:10 pm »
Chris posted a diagram a while back, the link is in my previous post, which had the second burn performed by the upper stage, and a third burn  after separation of the CEV to deorbit the stage.  Although I understand the basic principle of how all of this works, I'm very much in awe of the folks who do the maths for these trajectories.

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