Author Topic: Boeing discusses use of SLS for robust lunar program  (Read 36023 times)

Offline JohnFornaro

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Re: Boeing discusses use of SLS for robust lunar program
« Reply #80 on: 01/29/2013 12:15 am »
"Lunar COTS petition"?  I take it that this is your informal label? 'Cause I'm not aware of any such a formal petition.

No and yes.

No, Lunar COTS petition is real -- See LunarCOTS.com.  ...

Well, thanks for pointing that out.  I had read their paper before, perhaps even on this forum.  Their centrifugal gravity swinger thingy is kinda weird, but the heart of their proposal is in the right place.

I did not sign it.

Thanks again for pointing out their online effort.
Sometimes I just flat out don't get it.

Offline Ben the Space Brit

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Re: Boeing discusses use of SLS for robust lunar program
« Reply #81 on: 08/22/2013 12:14 pm »
I wonder what this payload and mission plan plus the mooted MB-60-powered Dual-Use Upper Stage could deliver?
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Offline Lobo

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Re: Boeing discusses use of SLS for robust lunar program
« Reply #82 on: 08/26/2013 07:39 pm »
I wonder what this payload and mission plan plus the mooted MB-60-powered Dual-Use Upper Stage could deliver?

Not sure.

I think here Boeing assumes a few things.
1)  4-engine SLS Block 1 core (which is the same for the Block 1B DUUS)
2) An upper stage that uses two J2X engine, and will do a chunk of the ascent.  I'm assuming that means they are assuming larger payloads that the 4-engine SLS core won't be able to get to disposal orbit, needing that J2X power to push to orbit.
3)  That two J2X upper stage does part of the EDS burn as well, and then is jettisoned before it does all of the TLI burn.
4)  Boeing's in-space stage is graphically depicted as looking just like a DCSS/ICPS, but when you look at the mass of it, it's more than twice as heavy I think.  Some of that is LCH4, but not all.  Because it does the remainder of the TLI burn, adn then gets to the gateway with enough propellant to refuel the lander and take it almost to the lunar surface.  So it really is an all new stage.

So, if I understand the Boeing proposal properly (and I discussed this at length with Steve Peitrobon, so I -think- I do) they are calling out a Block 1 SLS core, with a new 2-J2X upper stage, and a new inspace stage that's more than twice the size of the ICPS.

Vs. the DUUS/EUS plan which would probably put less total mass in LEO without the 2-J2X upper stage doing part of the ascent, and relies on the SLS core to get to disposal orbit.  But it then combines the J2X upper stage with the in-space stage.  So only one new development.
So, if keeping with Boeing's concept to have a gateway and a reusable lander based there, then I really don't see any reason the DUUS/EUS couldn't do the same thing, just with one stage.  It might effect the mass of the lander though.  While a single DUUS might be cheaper to develop than a 2-J2X stage and inspace stage, it might not have quite as good of performance.  I'll guess the dry mass of the inspace stage is less than the DUUS, so that's less mass being hauled to EMLP2, and less mass going down to the lunar surface.  Sort of the reason a 3- stage rocket is usually better performing than a 2- stage rocket.  But more expensive because of the extra stage.

So, what someone would have to do, is to model a Block 1B mission with a DUUS with MB-60 engines pushing Orion and tank of LCH4 to EMLP2, and see how much hydrolox is had left, along with how much spare residual LOX it would have for the lander.  Then that will tell you how much mass the lander can have and the DUUS still be able to get it to the lunar surface.

I'm guessing it'll be a little bit smaller lander than Boeing's proposal, but would be cheaper to develop with one stage vs. two. Because it won't be able to get quite as much methalox and dry mass down to terminal landing.

However, as I understand, the total dV required to go from the Earth's surface directly to the lunar surface is less than if going to L2 first, then coming back down to the lunar surface.  Ditto with going from the lunar surface back to Earth rather than going to L2 first.
So, there's a chance that while Block 1B and DUUS might mean a smaller lander for Boeing's proposal, it might be able to throw a Boeing sized lander (or a bit smaller lander) and Orion directly to LLO.
So you might be able to get pretty much the same mission by going directly rather than deturing to a Gateway station.
That assumes an expedanable lander of course.

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