Orion/SLS Discussion Thread!

[fredinno]

The name says all.

And please, don't .... this one up like the last 2 threads on this topic. You know who you 2 are.

[Zucal]

I'm optimistic. The tentative flight plans laid out seem to be fairly low budget given what SLS is, and NASA has ages to develop payloads.

[fredinno]

I'm optimistic. The tentative flight plans laid out seem to be fairly low budget given what SLS is, and NASA has ages to develop payloads.

I'm.. not so much. It's somewhat better than Constellation, and better than "Battleship Galactica", but it's still unsustainable TBH.

I think the crew should also be sent on a ion drive tug too, and just suck up the extra mission length required.

It would also reduce followup mission mass significantly. Also, use ISRU, if not done, for the MAV, and send a man-rated ISRU experiment on the test lander.

[Frybert]

Third time the charm?

[Mitchz95]

Do we know how long the surface stay is planned to be? Will it be 500 days like Zubrin's Mars Direct, or a month like The Martian?

[PB666]

The name says all.

And please, don't .... this one up like the last 2 threads on this topic. You know who you 2 are.

did we need more of this?

[sgt_flyer]

Do we know how long the surface stay is planned to be? Will it be 500 days like Zubrin's Mars Direct, or a month like The Martian?

i guess it will depend on the trajectory and avaible propulsion means at the time they'll be able to do the manned mission

With 'classic' current tech engines (with limited delta-V) - it depends on the chosen path. With orbital manoeuvers to go directly to mars (when the orbital window is avaible) you'll get the long stay on mars (until the launch window opens back from mars to earth)

If you use a venus gravity assist, to get to mars (not much longer than going directly to mars - but less specific launch windows) when the manned ship arrives to mars after the slingshot, the launch window back to earth is avaible almost immediately, so you get the short stay

Now, if we are able until then to devellop insanely efficient engines, launch windows becomes much less a problem because you can use brachistochrone transfers to mars - (the ship keeps firing it's engines to accelerate until mid course, then decelerate towards mars)

Sooo until we are much closer from the mission time, it'll be hard to predict which case they'll use

[fredinno]

Do we know how long the surface stay is planned to be? Will it be 500 days like Zubrin's Mars Direct, or a month like The Martian?

500 days.

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did we need more of this?

Kind of, yes.

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i guess it will depend on the trajectory and avaible propulsion means at the time they'll be able to do the manned mission

With 'classic' current tech engines (with limited delta-V) - it depends on the chosen path. With orbital manoeuvers to go directly to mars (when the orbital window is avaible) you'll get the long stay on mars (until the launch window opens back from mars to earth)

If you use a venus gravity assist, to get to mars (not much longer than going directly to mars - but less specific launch windows) when the manned ship arrives to mars after the slingshot, the launch window back to earth is avaible almost immediately, so you get the short stay

Now, if we are able until then to devellop insanely efficient engines, launch windows becomes much less a problem because you can use brachistochrone transfers to mars - (the ship keeps firing it's engines to accelerate until mid course, then decelerate towards mars)

Sooo until we are much closer from the mission time, it'll be hard to predict which case they'll use

They are assembling in Cis-Lunar, then sending them on a direct- to-mars trajectory. No Venus Flyby. 500 day stays on Mars per mission.

[Kibble]

Venus assist sounds like a great idea actually! We have lots of experience with people living long-term in orbital laboratories, none with people living long-term in extra-terrestrial surface labs. And it sharply decreases the amount of mass we would have to land on the surface! Maybe no exotic technologies like inflatable heat shields?

[Mitchz95]

I could see the first mission using the Venus assist and a short Mars surface stay, and the second mission being a direct-to-Mars trip with a long duration stay. The obvious downside to the former is that you'd hardly have any time for science on Mars. But the possibility of studying two planets in one mission is enticing, and would be a great "return to flight" moment for NASA as a whole.

If we did the Venus assist, how long would the trip to Mars take?

[fredinno]

Venus assist sounds like a great idea actually! We have lots of experience with people living long-term in orbital laboratories, none with people living long-term in extra-terrestrial surface labs. And it sharply decreases the amount of mass we would have to land on the surface! Maybe no exotic technologies like inflatable heat shields?

Inflatables would probably still be needed to allow cargo to land properly. It would also increase mass on a mission with 10 SLS Block II launches. Not a good idea.

I don't think it would decrease mass too much- Venus delta v is only .1 km/s less than mars. Amd ION is being used for most cargo transports.

[Rune]

What I wrote on the other thread has been one of my most-repped posts, including the ones where I release crafts, and it was never used as cannon fodder in any quote war or nothing. So I will copy the most relevant section, because I think it sums up my feelings on the matter very well:

Clearly this is a jigsaw puzzle made to fit all the unrelated pieces of shiny technology NASA has been pursuing for the last 40 years, lunar station included. The only problem? They don't fit together: you can't stage your mission from an orbit that only makes sense if you have fuel depots, without having fuel depots. You can't use SEP with the premise that it will save mas due to efficiency, when it'll cost extra mass on account of the chemical kick stages, the requirement to leave from a high-energy lunar orbit, and using it for a truly minute portion of the mission. ISRU is there, but again, it's used in such a marginal fashion that it won't actually save anything, just increase the complexity of the mission. Orion, nobody knows clearly what it's there for, I guess only a clone of Apollo can move people to lunar orbit. What is clear is the completely artificial requirement to use a staging orbit only the SLS can reach with meaningful payload. Because hey, the best way to kick-start this whole exploration thing is to exclude any other launch entity in the world from possibly contributing to the project in any way. Way to go, NASA.

Double emphasis on the comment about the current lunar orbit staging architecture being an artificial barrier to justify the existence of SLS. Oh, and a link to a nice article with the juicy details, more or less the free side of a paywall, enjoy.

Rune. So yeah, if the money spent on these had been spent on payloads for real rockets that actually fly... man, be would have launched a whole lot more cool stuff.

[Zucal]

What is clear is the completely artificial requirement to use a staging orbit only the SLS can reach with meaningful payload. Because hey, the best way to kick-start this whole exploration thing is to exclude any other launch entity in the world from possibly contributing to the project in any way. Way to go, NASA.

Two things. One is that the reason that high orbit was chosen is because departing from LEO using SEP means the crew spends too much time in the Van Allen belts. Two: This entire plan assumes the worst case scenario. NASA doesn't receive more funding, commercial parties are unable to contribute launches to lessen the pressure on SLS, ISRU doesn't become more capable/reliable, etc. Many things about this will change for the better between now and when the program begins to pick up speed.

[passinglurker]

What I wrote on the other thread has been one of my most-repped posts, including the ones where I release crafts, and it was never used as cannon fodder in any quote war or nothing. So I will copy the most relevant section, because I think it sums up my feelings on the matter very well:

Double emphasis on the comment about the current lunar orbit staging architecture being an artificial barrier to justify the existence of SLS. Oh, and a link to a nice article with the juicy details, more or less the free side of a paywall, enjoy.

Rune. So yeah, if the money spent on these had been spent on payloads for real rockets that actually fly... man, be would have launched a whole lot more cool stuff.

[warning I may start rambling]

I can see what you are saying but for the sake of conversation lets try this train of thought. The flight rate SLS needs be a certain abount to even be remotely viable and potentially there are bulky heavy payloads like deep space habitats and ISS rivaling solar power trusses that need a rocket with SLS's proportions.

Since its not a flexible clusterable multicore like falcon, delta, or angara that can keep production up by flying lighter configurations for more common jobs it simply has to fly a lot, with the limited budget to actually make the payloads there no room for it to have competition, and it must work at capacity to justify itself(geez it's beginning to sound like STS 2.0 but without the .... scifi space plane am I right?).

Why would anyone hatch a harebrained scheme like this to support the notion that they need a big rocket? While feeding the military industrial complex, and recreating apollo for votes are pretty natural answers let's try being marginally optimistic for a moment and entertain the thought that maybe there are bulky payloads that only a heavy lifter can support and that in order to have the rocket they need for those few payloads they need to hatch a scheme where it is needed for all the payloads.

Essentially if there is even one needed architectural component that no other rocket can support then they would need to hatch a scheme like this to support the one rocket to do the job for that one component. Whether it's the best solution is certainly up to debate. A debate about how to best travel through space that has probably raged since just before apollo. I think in the end the SLS system like the saturn V and STS stand to accomplish great things no one else is going to bother to do. It may be a bloated mess but it's one of only a few rockets being made to actually push boundaries and thanks to its zombie like political momentum it may accomplish some of its ends before going down in history as yet another case of "how not to build a sustainable rocket"

I guess what I'm saying is I'm not going to be too upset about it being a train wreck as long as it gets at least to phobos. politics is a harsher environment than space to the point that engineering to navigate the senate floor is more important than considerations for outer space if one is ultimately to get anywhere in the first place, and you gotta admit if there is one thing SLS is good at its politics. That being said I don't think there is much of a need to rush. A man on a martian moon is nice and all but not at the expense of other more practical programs like commercial crew, planetary science, etc...

Edited September 26, 2015 by passinglurker

[fredinno]

Two things. One is that the reason that high orbit was chosen is because departing from LEO using SEP means the crew spends too much time in the Van Allen belts. Two: This entire plan assumes the worst case scenario. NASA doesn't receive more funding, commercial parties are unable to contribute launches to lessen the pressure on SLS, ISRU doesn't become more capable/reliable, etc. Many things about this will change for the better between now and when the program begins to pick up speed.

The problem is that it's not. The crew is not using SEP to go to Mars, only the cargo, which is also braking at Mars orbit instead of just diving in for some dumb reason.

It's also not a worst-case scenario, this is their plan for the future.

[Zucal]

The problem is that it's not. The crew is not using SEP to go to Mars, only the cargo, which is also braking at Mars orbit instead of just diving in for some dumb reason.

It's also not a worst-case scenario, this is their plan for the future.

Only one of the two plans outlined in the article uses an all-chemical transit stage. The reason that the cargo is braking in orbit is because that vastly reduces the complexity of EDL- see the Viking landers. The extra mass of fuel was obviously deemed worth the increased safety.

This isn't their set-in-stone, fixed course. This is an outline of a few notional routes the Mars program might take, without including the many game changers that are extremely likely to happen between then and now.

[Rune]

Two things. One is that the reason that high orbit was chosen is because departing from LEO using SEP means the crew spends too much time in the Van Allen belts. Two: This entire plan assumes the worst case scenario. NASA doesn't receive more funding, commercial parties are unable to contribute launches to lessen the pressure on SLS, ISRU doesn't become more capable/reliable, etc. Many things about this will change for the better between now and when the program begins to pick up speed.

Well, as somebody has already said, there are payloads, including the humans, that make the trip on chemical stages under the present plans. Hypergolic stages, even. It is very telling in and of itself, that the low-efficiency propulsion option is actually just as efficient in launches, tell you how well leveraged SEP is in this plan. Also, consider that the payload of a SLS to distant retrograde orbit is very comparable to an EELV's payload to LEO, so this pieces are actually sized for an EELV, mass-wise. I know, volume is another constraint... but hey, I can at least affirm without fear of being wrong that you could use less, more massive elements, if you staged in LEO. Or lift the present ones on the existing EELV fleet. And you know, spend the dV that the upper stage uses to launch the pieces to the moon (chemically, I must add) to have extra mass to give yourself dV to depart straight form LEO: good old Oberth will actually save some dV from the budget.

Also, you will tell me how this fits in the present budget, when they are talking about two SLS launches a year or more, while building the surface elements at the same time. NASA has been trying to build one rocket and capsule for more than a decade now, and they expect to build two each year with the same budget?

Rune. Nope, this whole thing is an attempt at justifying SLS and Orion, and a pretty unconvincing one at that.

[davidy12]

500 days.

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Kind of, yes.

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They are assembling in Cis-Lunar, then sending them on a direct- to-mars trajectory. No Venus Flyby. 500 day stays on Mars per mission.

Here's something I can't understand. WHY ASSEMBLE IT IN LUNAR ORBIT? Okay, I know about orbital decay, but it shouldn't be that much of a hindrance right? Also, if they assemble it on the surface like in the Space Flight Initiative, that is just crazy and pointless.

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Also, all in all, I'm fairly confident the SLS will get us to Mars. At this point it's too far to cancel, seeing it's already under construction. I'd be willing to bet my years at graduate school that we'll see men (and women) on a circumlunar flight by the time I'm a sophomore in grad school.

[Mitchz95]

Forgive my ignorance, but what's SEP?

[Karriz]

Forgive my ignorance, but what's SEP?

Solar Electric Propulsion. NASA is looking into using ion engine tugs as part of their mission architecture.

[Zucal]

Also, consider that the payload of a SLS to distant retrograde orbit is very comparable to an EELV's payload to LEO, so this pieces are actually sized for an EELV, mass-wise.

Sorry, but no. SLS Block II can throw 50-60 tons to a Lunar transfer orbit, and the heaviest launcher proposed (Falcon Heavy) will be able to do slightly more than half that to LEO. BFR does not count.

[Karriz]

Sorry, but no. SLS Block II can throw 50-60 tons to a Lunar transfer orbit, and the heaviest launcher proposed (Falcon Heavy) will be able to do slightly more than half that to LEO. BFR does not count.

Isn't Falcon Heavy 50 tons to LEO in expendable mode? I know there's been a lot of debate whether that's the actual figure, but with the F9 Full-Thrust upgrade the numbers have probably changed again.

[Rune]

Sorry, but no. SLS Block II can throw 50-60 tons to a Lunar transfer orbit, and the heaviest launcher proposed (Falcon Heavy) will be able to do slightly more than half that to LEO. BFR does not count.

That is a bit higher than I though when I wrote that, but then again, you are quoting performance for the totally unfunded Block II. At this point, that is more of a hypothetical rocket than the BFR, by many measures. Still, conceding all your points, all the payloads I see are Orions with ~20mT ISS-derived modules, and ion tugs attached to similarly sized payloads and chemical stages. So yeah, they are using that ~50mT payload in DRO to deliver two EELV-sized packages at a time. Oh, and TLI capacity doesn't count either, you have to measure once inserted into DRO, and exclude the weight of the empty upper stage.

I guess that would be sensible if you expect your rocket to be cancelled and you are designing something that could be repackaged in other launcher. Because all of this can be done with a EELV-based architecture, assembling stacks in LEO with chemical refuelable stages. Or, you know, whatever takes the place of EELVs by then. They are a bit tight in payload for some elements, especially the stuff that has to be packaged for martian EDL, but the next batch on the horizon sound much better, most of them go comfortably over the 20mT payload, and FH is even often quoted with 53mT to LEO (I figure I highly doubt, BTW).

But anyhow, given a SHLV like SLS, what you should be really be hot about is the volume. It allows you to launch truly massive ships to LEO to be refueled and restocked later, so this plan also makes very poor use of that humongous payload shroud. Or giant heathshields, although for human-sized payloads you are going to have some short of deployable system for that unless you build truly absurd rockets (>20m in diameter or something similarly stupid). So yeah, if SLS ends up flying, I would actually consider it a sound decision to let it at block 1b or something like that (because the ICPS is absurdly undersized).

Rune. What is really funny is that the original Saturn C-3 that Von Braun wanted to build the manned US space program around was a 50mT high-diameter booster... short of like the N-1 as first envisioned by Korolev. In time, we will come back to the principles, I'm sure...

[fredinno]

That is a bit higher than I though when I wrote that, but then again, you are quoting performance for the totally unfunded Block II. At this point, that is more of a hypothetical rocket than the BFR, by many measures. Still, conceding all your points, all the payloads I see are Orions with ~20mT ISS-derived modules, and ion tugs attached to similarly sized payloads and chemical stages. So yeah, they are using that ~50mT payload in DRO to deliver two EELV-sized packages at a time. Oh, and TLI capacity doesn't count either, you have to measure once inserted into DRO, and exclude the weight of the empty upper stage.

I guess that would be sensible if you expect your rocket to be cancelled and you are designing something that could be repackaged in other launcher. Because all of this can be done with a EELV-based architecture, assembling stacks in LEO with chemical refuelable stages. Or, you know, whatever takes the place of EELVs by then. They are a bit tight in payload for some elements, especially the stuff that has to be packaged for martian EDL, but the next batch on the horizon sound much better, most of them go comfortably over the 20mT payload, and FH is even often quoted with 53mT to LEO (I figure I highly doubt, BTW).

But anyhow, given a SHLV like SLS, what you should be really be hot about is the volume. It allows you to launch truly massive ships to LEO to be refueled and restocked later, so this plan also makes very poor use of that humongous payload shroud. Or giant heathshields, although for human-sized payloads you are going to have some short of deployable system for that unless you build truly absurd rockets (>20m in diameter or something similarly stupid). So yeah, if SLS ends up flying, I would actually consider it a sound decision to let it at block 1b or something like that (because the ICPS is absurdly undersized).

Rune. What is really funny is that the original Saturn C-3 that Von Braun wanted to build the manned US space program around was a 50mT high-diameter booster... short of like the N-1 as first envisioned by Korolev. In time, we will come back to the principles, I'm sure...

But this plan is supposed to use Block II!

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Isn't Falcon Heavy 50 tons to LEO in expendable mode? I know there's been a lot of debate whether that's the actual figure, but with the F9 Full-Thrust upgrade the numbers have probably changed again.

45 T, from V 1.1 Falcon 9.

[Zucal]

45 T, from V 1.1 Falcon 9.

That figure assumes all three cores are expended, and SpaceX almost certainly won't fly that configuration unless they're paid extra by NASA. Assuming no crossfeed and full reuse, FH's payload to LEO is probably in the high 30s.

That is a bit higher than I though when I wrote that, but then again, you are quoting performance for the totally unfunded Block II. At this point, that is more of a hypothetical rocket than BFR, by many measures.

Sorry, but that's not true. SLS Block II's only addition from Block IB (which flies on the second or third total flight) is the advanced boosters. Nothing else is changed. The booster proposals are already out and hardware is already being tested by the companies in question. SLS Block II has a decade to be completed. You can't complain that Congress is overfunding SLS and then complain that Block II is currently unfunded!

By comparison, the only work done on BFR is testing of some of the engine components. Not a single weld has been made on BFR, we don't even know what it looks like, what its payload will be, or whether it will be so specialized that it cannot be used as a general super-heavy lifter.

Edited September 26, 2015 by Zucal