Author Topic: NASA finally sets goals, missions for SLS - eyes multi-step plan to Mars  (Read 28023 times)


Offline Eric Hedman

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Great article.  It will be interesting to see what support develops for this going forward.  I'm looking forward to what is yet to come including information on the DST.

Offline Eric Hedman

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A rendering of the DST.

http://boeing.mediaroom.com/2017-04-03-Boeing-Unveils-Deep-Space-Concepts-for-Moon-and-Mars-Exploration#assets_117:20175

I'm betting that the habitat part is to be made with SLS core tooling so 8.4 meters in diameter.  The SEP propulsion part on it is interesting.
« Last Edit: 04/07/2017 11:23 AM by Chris Bergin »

Offline Khadgars

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Fantastic article.  I like the plan as currently envisioned.  Its pragmatic, nothing too fancy and more importantly, doable with current and near future technology.

It also brings in commercial partners, that may see their role expand as the Gateway progresses.
« Last Edit: 04/06/2017 10:29 PM by Khadgars »

Offline TomH

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A nicely written article by Chris G. Nevertheless, all these grandiose plans coupled with deep beget cuts leaves me more doubtful than ever.

Online shooter6947

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Well:  it's a plan.

But why again put a Deep Space Gateway in lunar orbit?  Without an Oberth Effect it takes hardly less delta-V to get to Mars from there than it does from LEO.  Why not just start in LEO instead of getting everything out there to the Moon in the first place?

I do understand the (perhaps excessively cautious) desire for the shakedown cruise in Lunar orbit.  But then why a gateway again?  I think that I'm missing a link in the logic chain . . .

Offline Eric Hedman

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A nicely written article by Chris G. Nevertheless, all these grandiose plans coupled with deep beget cuts leaves me more doubtful than ever.
We have seen no signs that NASA is going to be hammered hard with budget cuts.  Plus I'd first like to see what NASA says this next phase is going to cost before coming to a conclusion as to what the outcome will be.  And besides, Congress will be setting the budget.

Offline Eric Hedman

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Well:  it's a plan.

But why again put a Deep Space Gateway in lunar orbit?  Without an Oberth Effect it takes hardly less delta-V to get to Mars from there than it does from LEO.  Why not just start in LEO instead of getting everything out there to the Moon in the first place?

I do understand the (perhaps excessively cautious) desire for the shakedown cruise in Lunar orbit.  But then why a gateway again?  I think that I'm missing a link in the logic chain . . .
The reasoning is that the DSG is an affordable next step that also allows missions on and around the Moon by NASA or other agencies or private companies that want to operate there.  Japan is already interested in adding their own module to the DSG.  The delta vee difference from EM-L2 to a Mars transfer orbit and from LEO to Mars transfer is not insignificant.  According to WIkipedia https://en.wikipedia.org/wiki/Delta-v_budget

 LEO to Mars transfer is 4.3 km/s while EM L2 to Mars transfer is <1 km/s.

Also from the rendering of Boeing's concept for the DST it will be propelled by SEP.  You don't want a slow spiral through the Van Allen belts leaving LEO.

Offline RocketmanUS

With the long time delay it looks like the government is dragging its feet waiting for commercial launch vehicles to become available. Commercial has the potential to reach the Lunar surface  and mars surface before SLS.

The economics with SLS are not there and now even more with 1st stage reuse. Congress and NASA needs to face reality !
Mars and beyond, human exploration
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Offline envy887

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Well:  it's a plan.

But why again put a Deep Space Gateway in lunar orbit?  Without an Oberth Effect it takes hardly less delta-V to get to Mars from there than it does from LEO.  Why not just start in LEO instead of getting everything out there to the Moon in the first place?

I do understand the (perhaps excessively cautious) desire for the shakedown cruise in Lunar orbit.  But then why a gateway again?  I think that I'm missing a link in the logic chain . . .

The Oberth assist from L2/NRO/DRO is actually better than in LEO. The first maneuver to insert to a Earth transfer with a low perigee, where the velocity is over 3 km/s greater than LEO and already near escape. At perigee the Mars transfer burn is performed.

It's not as efficient as a direct transfer out of LEO, but high staging has a lot advantages for SEP transfers.

Offline Coastal Ron

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I would have wished that NASA would have put the requirements out to the private sector for them to provide what they think the best solutions would be, and that way we'd also have the ability to assess what the cost trade-offs were for the different approaches.  But alas, we live in a different reality...
If we don't continuously lower the cost to access space, how are we ever going to afford to expand humanity out into space?

Offline redliox

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Better than loitering indefinitely in LEO, still leaves much to desire, but probably the most NASA can afford to do with its foreseeable budget.  I'd take this over the ludicrous ARM plan, and apparently the international community seems to back a Moon-first path. 

The specific part I question would be the DST.  While the DSG could serve a useful function if periodically pushed out to L2, I haven't seen the best enthusiasm for directly coupling SEP with a crewed mission.  Although the Lunar L2 position would be a good staging point, SEP is still painfully slow; at worst the thrust buildup is so slow you might miss your launch window entirely.  This is why I fear such a setup will inevitably require literally tons (tonnes?) of stuff dumped into Mars orbit, translating to far more SLS launches (or just launches in general) just to deliver propellants SEP was meant to eliminate.

The DSG should still be useful, although obviously more towards Lunar v.s. Martian exploration.  Propulsively a direct route to Mars is more efficient, although the L2 stopover would be the 2nd best choice.  I think the plans post 2026 should be reconsidered, especially if Blue Origins and SpaceX deliver on their promises of alternate HLVs and vehicles.  To sum up some constructive criticism, my suggestion would be once the DSG is finished the focus must go exclusively to developing landers: cargo, crew, Lunar, or Martian.
« Last Edit: 04/07/2017 02:03 AM by redliox »
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Offline TrevorMonty

I would have wished that NASA would have put the requirements out to the private sector for them to provide what they think the best solutions would be, and that way we'd also have the ability to assess what the cost trade-offs were for the different approaches.  But alas, we live in a different reality...
International partners are supplying some of modules and helping with others. That is why commercial modules don't get a look in.

Assembly cost for DSG shouldn't be that expensive for NASA. Not counting SLS/Orion flights as the annual flights are going to happen anyway.

DST will be lot more expensive, but while away from needing serious money for that.

If  a commercial crew capable of reaching DSG comes available,  then there is possibility of extra crew or private missions each year.

Online MATTBLAK

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I really hope Commercial Space gets into developing a manned Lunar Lander for future landing ops.

In fact, there has been an interesting thread on that very thing:  http://forum.nasaspaceflight.com/index.php?topic=42363.0;all
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Offline Eric Hedman

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Does anyone have a guess as to how long transit times from L2 to Mars might be with the DST and SEP?

Offline redliox

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Does anyone have a guess as to how long transit times from L2 to Mars might be with the DST and SEP?

I've seen figures that range from 8 months to 2 years.  I do have a few PDFs that included info on SEP propulsion.  I know enough that it won't be Hoffman-style trajectories, but slower ones where the spacecraft isn't just simply zipping by but rather actively (albeit slowly) matching speed with Mars throughout its whole trip.  You certainly won't see any numbers as swift as six months.
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Offline blasphemer

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Well:  it's a plan.

But why again put a Deep Space Gateway in lunar orbit?  Without an Oberth Effect it takes hardly less delta-V to get to Mars from there than it does from LEO.  Why not just start in LEO instead of getting everything out there to the Moon in the first place?

I do understand the (perhaps excessively cautious) desire for the shakedown cruise in Lunar orbit.  But then why a gateway again?  I think that I'm missing a link in the logic chain . . .

*Conspiracy hat on

NASA is aware we aint going to Mars under current budgets. Deep Space Gateway is the nice way to do something in cislunar space while still plausibly pretending that it is all about going to Mars. Otherwise we risk being stuck in LEO for another several decades.

*Conspiracy hat off

Offline K-P

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NASA is aware we aint going to Mars under current budgets. Deep Space Gateway is the nice way to do something in cislunar space while still plausibly pretending that it is all about going to Mars. Otherwise we risk being stuck in LEO for another several decades.

*Conspiracy hat off

a.k.a. better to have 30% of something than 100% of nothing.

And I'm all for that in this matter.


Offline A_M_Swallow

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Ground prototypes for the habitats likely to be used in the Deep Space Gateway and Transport are being developed under NextSTEP-2.
https://www.nasa.gov/feature/nextstep-partnerships-develop-ground-prototypes

I do wonder when the milestones and agreements will be published.

Offline MikeAtkinson

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Well:  it's a plan.

But why again put a Deep Space Gateway in lunar orbit?  Without an Oberth Effect it takes hardly less delta-V to get to Mars from there than it does from LEO.  Why not just start in LEO instead of getting everything out there to the Moon in the first place?

I do understand the (perhaps excessively cautious) desire for the shakedown cruise in Lunar orbit.  But then why a gateway again?  I think that I'm missing a link in the logic chain . . .

The Oberth assist from L2/NRO/DRO is actually better than in LEO. The first maneuver to insert to a Earth transfer with a low perigee, where the velocity is over 3 km/s greater than LEO and already near escape. At perigee the Mars transfer burn is performed.

It's not as efficient as a direct transfer out of LEO, but high staging has a lot advantages for SEP transfers.

But SEP transfers cannot make use of the Oberth effect as they have too little thrust at perigee. They need to do a chemical burn at perigee, then use the SEP, but that just complicates things.

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