Author Topic: Deep Space Gateway Power/Propulsion RFI  (Read 65403 times)

Offline TrevorMonty

Re: Deep Space Gateway Power/Propulsion RFI
« Reply #80 on: 01/20/2018 11:05 pm »
Orion does not have enough propulsive capability to enter and return from LLO.

I actually requested more information on the Orion delta-v front in another thread, the discussion on which starts here.
This is from memory havn't confirmed it, Orion is about 1800m/s.
« Last Edit: 01/20/2018 11:09 pm by TrevorMonty »

Offline Steven Pietrobon

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Re: Deep Space Gateway Power/Propulsion RFI
« Reply #81 on: 01/21/2018 12:16 am »
Orion does not have enough propulsive capability to enter and return from LLO.

Yes, that's true. It does have enough delta-V to leave LLO though. An EUS designed to last the three day journey to the Moon could do LLO insertion with Orion (as well as an LM on a separate mission).
« Last Edit: 01/21/2018 12:17 am by Steven Pietrobon »
Akin's Laws of Spacecraft Design #1:  Engineering is done with numbers.  Analysis without numbers is only an opinion.

Offline Steven Pietrobon

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Re: Deep Space Gateway Power/Propulsion RFI
« Reply #82 on: 01/21/2018 12:19 am »
This is from memory havn't confirmed it, Orion is about 1800m/s.

Its less than that. I calculated 1227 m/s.
Akin's Laws of Spacecraft Design #1:  Engineering is done with numbers.  Analysis without numbers is only an opinion.

Offline Proponent

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Re: Deep Space Gateway Power/Propulsion RFI
« Reply #83 on: 01/22/2018 01:02 pm »
The attached NASAfacts sheet from 2011 indicates a delta-V of 4920 ft/s, i.e., 1500 m/s.

The mass to orbit is quoted as 50,231 lbm, while the SM's propellant load is 17,433 lbm, giving a mass ratio of 1.5315, assuming negligible propellant residuals.  The delta-V of 1500 m/s then in turn implies an effective exhaust velocity of 3518.9 m/s, i.e., a specific impulse of 359 s, which seems unlikely for storable propellants.

I think what's missing in this analysis is that some propellant is burned on the way to orbit, since SLS places Orion only into a transfer orbit with a very low perigee.

EDIT:  The last sentence obviously applies only for some mission profiles.  It would not apply for a cislunar mission launched on a Block 1B SLS.  Since the spec sheet is so old, I wonder whether it may refer to an LEO mission launched by Ares I.
« Last Edit: 01/22/2018 03:59 pm by Proponent »

Offline hektor

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Re: Deep Space Gateway Power/Propulsion RFI
« Reply #84 on: 01/22/2018 01:26 pm »
The attached NASAfacts sheet from 2011 indicates a delta-V of 4920 ft/s, i.e., 1500 m/s.

The mass to orbit is quoted as 50,231 lbm, while the SM's propellant load is 17,433 lbm, giving a mass ratio of 1.5315, assuming negligible propellant residuals.  The delta-V of 1500 m/s then in turn implies an effective exhaust velocity of 3518.9 m/s, i.e., a specific impulse of 359 s, which seems unlikely for storable propellants.

I think what's missing in this analysis is that some propellant is burned on the way to orbit, since SLS places Orion only into a transfer orbit with a very low perigee.

Wikipedia gives 316 s for the OMS Engine, if this figure is correct it would be closer to 1200 m/s as indicated above
« Last Edit: 01/22/2018 01:28 pm by hektor »

Offline MaxTeranous

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Re: Deep Space Gateway Power/Propulsion RFI
« Reply #85 on: 01/22/2018 01:27 pm »
The attached NASAfacts sheet from 2011 indicates a delta-V of 4920 ft/s, i.e., 1500 m/s.

The mass to orbit is quoted as 50,231 lbm, while the SM's propellant load is 17,433 lbm, giving a mass ratio of 1.5315, assuming negligible propellant residuals.  The delta-V of 1500 m/s then in turn implies an effective exhaust velocity of 3518.9 m/s, i.e., a specific impulse of 359 s, which seems unlikely for storable propellants.

I think what's missing in this analysis is that some propellant is burned on the way to orbit, since SLS places Orion only into a transfer orbit with a very low perigee.

How on earth does SLS not have the juice to put Orion into a decent orbit?

Offline Proponent

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Re: Deep Space Gateway Power/Propulsion RFI
« Reply #86 on: 01/22/2018 02:16 pm »
SLS has the juice.  The idea is that you don't want SLS itself going into orbit, because then you don't know where it will re-enter.  That's why Orion has to provide a bit of its own delta-V to reach a stable orbit.

Offline brickmack

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Re: Deep Space Gateway Power/Propulsion RFI
« Reply #87 on: 01/22/2018 04:31 pm »
You're confusing the SLS Core stage with iCPS/EUS. The former stages slightly suborbital, the latter reaches a circular parking orbit first and then performs TLI, and then completes a disposal burn afterwards

Offline Proponent

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Re: Deep Space Gateway Power/Propulsion RFI
« Reply #88 on: 01/23/2018 02:07 am »
You're confusing the SLS Core stage with iCPS/EUS. The former stages slightly suborbital, the latter reaches a circular parking orbit first and then performs TLI, and then completes a disposal burn afterwards

Yes, indeed, I am.  Thank you.

Offline speedevil

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Re: Deep Space Gateway Power/Propulsion RFI
« Reply #89 on: 02/24/2018 01:09 am »
DSG - if you squint a little, looks moderately like a modern high power GEO comsat with a little more fuel and engines.
« Last Edit: 02/24/2018 03:51 am by speedevil »

Offline Toast

Re: Deep Space Gateway Power/Propulsion RFI
« Reply #90 on: 02/26/2018 11:27 pm »
Looks like in the budget proposal from a couple weeks back the Deep Space Gateway has been renamed the "Lunar Orbital Platform", the propulsion module now has funding attached to it ($504 million next year, $2.7 billion over five years), and the targeted launch date is actually being moved up to 2022. It is also now is planned for launch on a commercial vehicle instead of on the EM-2 SLS flight.

Offline mike robel

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Re: Deep Space Gateway Power/Propulsion RFI
« Reply #91 on: 02/27/2018 12:33 am »
I see no benefit to sending what seems to be a sporadically inhabited outpost to the moon to do something that less expensive unmanned satellites could accomplish with less cost and greater coverage.

In my limited view, a more valid course of action would be to craft a spacecraft designed to last say 24 months in orbit to simulate a 6 month trip  to mars, 12 month  surface mission, and 6 month return, by a crew of 6 to 8 without resupply from Earth.  If things go wrong, they are minutes/hours from home and we could easily have a launch on need Falcon 9/Dragon or Atlas 5/CST booster on short notice for launch as well as an escape craft with the spacecraft.

Offline Space Ghost 1962

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Re: Deep Space Gateway Power/Propulsion RFI
« Reply #92 on: 02/27/2018 03:05 am »
Suggest that the rationale for DSG/LOS is more about the missions/vehicles that would be passing through said way station than the way station itself. (The fact that it's being called a Lunar Orbital Station dooms it - doesn't need a DST, and there's no lander, so its just a "dead end" for NASA contractors to build, play with, and abandon, like ISS. Stillborn again.)

Otherwise why have a way station at all.

Like the original EM 1/2 missions for SLS, it is an unworthy gesture of the grand gesture of a national/international space program.

But then it says more about who and what we are, as a species, that we dither in such a silly way.

Plan your DST or lander or base (or all) as a complete vision. If it needs a way station, that follows out of the mission requirements and architecture. And only as much as is needed, so it doesn't become a "dead end".

There is no real commitment, just a show?

Offline AncientU

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Re: Deep Space Gateway Power/Propulsion RFI
« Reply #93 on: 02/27/2018 10:55 am »
Looks like in the budget proposal from a couple weeks back the Deep Space Gateway has been renamed the "Lunar Orbital Platform", the propulsion module now has funding attached to it ($504 million next year, $2.7 billion over five years), and the targeted launch date is actually being moved up to 2022. It is also now is planned for launch on a commercial vehicle instead of on the EM-2 SLS flight.

That's a steep 'initial' price tag for an SEP tug.
What part of the technology is so expensive?
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Offline woods170

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Re: Deep Space Gateway Power/Propulsion RFI
« Reply #94 on: 02/27/2018 11:06 am »
Looks like in the budget proposal from a couple weeks back the Deep Space Gateway has been renamed the "Lunar Orbital Platform", the propulsion module now has funding attached to it ($504 million next year, $2.7 billion over five years), and the targeted launch date is actually being moved up to 2022. It is also now is planned for launch on a commercial vehicle instead of on the EM-2 SLS flight.

That's a steep 'initial' price tag for an SEP tug.
What part of the technology is so expensive?

No part. It's just that it will be done "NASA-style", much like SLS and Orion.
Remember: gravy train...
« Last Edit: 02/27/2018 11:07 am by woods170 »

Offline AncientU

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Re: Deep Space Gateway Power/Propulsion RFI
« Reply #95 on: 02/27/2018 11:31 am »
Looks like in the budget proposal from a couple weeks back the Deep Space Gateway has been renamed the "Lunar Orbital Platform", the propulsion module now has funding attached to it ($504 million next year, $2.7 billion over five years), and the targeted launch date is actually being moved up to 2022. It is also now is planned for launch on a commercial vehicle instead of on the EM-2 SLS flight.

That's a steep 'initial' price tag for an SEP tug.
What part of the technology is so expensive?

No part. It's just that it will be done "NASA-style", much like SLS and Orion.
Remember: gravy train...

That kind of a price tag sure negates all the arguments about using SEP tugs to move bulk stuff around the Solar System.  Cannot imagine what 'bulk' commodities could afford a $2.7B* push.  Going so slow also implies each tug gets one (or maybe two) Mars payloads in its lifetime...

* Plus 'inflation'
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Offline brickmack

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Re: Deep Space Gateway Power/Propulsion RFI
« Reply #96 on: 02/27/2018 06:07 pm »
Being that most of the PPE options being bid are heavily derived from existing commercial comsats, with a lot of publicly available information on their pricing, it'll be interesting to see how they spin this as a sane expenditure

Offline Toast

Re: Deep Space Gateway Power/Propulsion RFI
« Reply #97 on: 02/27/2018 06:30 pm »
Looks like in the budget proposal from a couple weeks back the Deep Space Gateway has been renamed the "Lunar Orbital Platform", the propulsion module now has funding attached to it ($504 million next year, $2.7 billion over five years), and the targeted launch date is actually being moved up to 2022. It is also now is planned for launch on a commercial vehicle instead of on the EM-2 SLS flight.

That's a steep 'initial' price tag for an SEP tug.
What part of the technology is so expensive?

Good question. NASA wants a really big system (50 kW), but that's still a pretty insane price tag. We should find out more soon, since NASA requested studies from five companies back in November that should be due to wrap up by March.

Offline DreamyPickle

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Re: Deep Space Gateway Power/Propulsion RFI
« Reply #98 on: 02/27/2018 07:25 pm »
You're confusing the SLS Core stage with iCPS/EUS. The former stages slightly suborbital, the latter reaches a circular parking orbit first and then performs TLI, and then completes a disposal burn afterwards

The SLS upper stage is hydrolox, isn't it impossible for it to last 3 days and relight for lunar orbit insertion? I know ULA's ACES claims to be able to do it but that's only after they develop IVF.

I also remember reading that NRHO was picked partly because of limited Orion delta-v, is that true?

On a related note, isn't it also very difficult to bring a SEP craft to lunar orbit Moon using only its own power? Switching the PPE to a commercial launch brings many new issues.
« Last Edit: 02/27/2018 11:35 pm by DreamyPickle »

Offline brickmack

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Re: Deep Space Gateway Power/Propulsion RFI
« Reply #99 on: 02/27/2018 08:25 pm »
The SLS upper stage is hydrolox, isn't it impossible for it to last 3 days and relight for orbit insertion? I know ULA's ACES claims to be able to do it but that's only after they develop IVF.

I also remember reading that NRHO was picked partly because of limited Orion delta-v, is that true?

On a related note, isn't it also very difficult to bring a SEP craft to lunar orbit Moon using only its own power? Switching the PPE to a commercial launch brings many new issues.

It wouldn't have to, TLI would be just a couple hours after LEO insertion. Orion does all later propulsion. There was a proposal for a Cryogenic Propulsion Stage (hence the name of Block 1's upper stage as the interim CPS) which would operate for weeks and could directly insert Orion and payload into LLO, but it fizzled. But even without ACES, ULA claims DCSS and Centaur could survive more than a week with only minor changes (namely a deployable solar shield). Its just that nobody has bought one, but it is advertised as a growth option in the payload planners guides (like Atlas V Heavy)

Difficult, but not impossible. SNC's PPE bid would include a close derivative used as a LEO-cislunar-LEO cargo vehicle, apparently using SEP for everything

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