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NASA Human Landing System

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23 hours ago, sevenperforce said:

NASA's current Ground Rules and Assumptions for cislunar activities presume total propellant mass boiloff, per day, as follows:

  • 0.35% for hydrolox
  • 0.20% for methalox
  • 0.20% for kerolox

Is it for fuel tanks of a rocket in space or for on-ground storage facilities with active cooling?

(As "Ground" and "cislunar").

Edited by kerbiloid

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On 2/22/2019 at 9:43 PM, sevenperforce said:

Refueling isn't a magic fix for issues like boiloff and ullage. Starship gets around it by having such a massive square-cube advantage that boiloff and generous RCS use are inconsequential, but something like Centaur can't manage nearly so easily. IIRC, Centaur has to actively vent hydrogen boil-off throughout its entire coast just to maintain ullage and prevent the tanks from popping.

The Falcon 9 user's guide suggests the current payload adapter is limited to 11 tonnes for center of mass reasons, but says that higher-mass payloads can be accommodated as a special service. I believe the problem is not so much with structural loads on the upper stage (and certainly not for the lower stage) as it is the bending moment on the payload adapter during pitchover under power. If the payload's center of mass is too high above the payload adapter then it will not be able to stay secure. The largest payloads launched in a fairing to date have been the Iridium NEXT clusters at over nine tonnes.

But all you need to remedy that is to design a custom PAF, which isn't so bad. Structural limitations on the vehicle itself are probably much higher.

You forgot the starlink missions with 18 ton on the last. With the crazy release mechanism it probably did not use an standard adapter. 

 

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22 hours ago, tater said:

Storables make far more sense, as the idea of 2 SLS launches anything like close together in time seems fully absurd, and on top of that long pole, I tend to think that distributed launch really needs to demonstrate rapid launch cadence first, then there can be talk of non-storable props, otherwise it makes sense to design architectures that are not as schedule-critical.

The issue of course is that any SLS-based architecture also needs the lander to do LOI (low at Gateway), and transfer to LLO (basically making it similar to direct LLO LOI) so the dv requirements for the vehicle are higher than they would be otherwise.

But of course if you have ZBO for non-storables, you can use distributed launch and you don't need SLS in the first place.

18 hours ago, kerbiloid said:

Is it for fuel tanks of a rocket in space or for on-ground storage facilities with active cooling?

(As "Ground" and "cislunar").

"Ground rules" is a term of art referring to basic principles or starting points; it has nothing to do with GSE. Those boil off numbers are for tanks in transit from Earth to the moon, assuming barrel roll or other mitigation.

17 hours ago, magnemoe said:

You forgot the starlink missions with 18 ton on the last. With the crazy release mechanism it probably did not use an standard adapter. 

Fair, but that quote was from February, before any Starlink flight flew.

I suspect, as I've said before, that the Starlink stack is braced against the fairing for stability during ascent.

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2 minutes ago, sevenperforce said:

But of course if you have ZBO for non-storables, you can use distributed launch and you don't need SLS in the first place.

LOL, true.

 

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On 11/19/2019 at 1:55 PM, sevenperforce said:

NASA's current Ground Rules and Assumptions for cislunar activities presume total propellant mass boiloff, per day, as follows:

  • 0.35% for hydrolox
  • 0.20% for methalox
  • 0.20% for kerolox

We know kerolox does not boil off at all -- rather, it is more likely to freeze -- and so the LOX is the limiting factor for both kerolox and methalox. O/F ratio is higher for methalox than kerolox, anyway.

Correct.  The oxygen is hard to keep.  

Hypergolics can keep in a steel can without insulation or cooling for a long time.  There is about a loss of 6% ISP... which means it's superior for missions lasting more than 30 days.

For a lander the advantages are numerous.  

Instead of a beach ball with a frame around it, like Blue Moon, the incentive is to put fuel in any stamped metal cavity rather than design around a huge fuel tank.

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This thread should probably be renamed to "NASA Human Landing System," as that's the official name of the program.

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18 hours ago, tater said:

 

I really like the way this lander looks.

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3 hours ago, jadebenn said:

This thread should probably be renamed to "NASA Human Landing System," as that's the official name of the program.

Done.

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3 hours ago, Wjolcz said:

I really like the way this lander looks.

So do I. Not sure how it gets to space, though.

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1 minute ago, sevenperforce said:

So do I. Not sure how it gets to space, though.

It needs an large fairing, Looks like its 7-9 meter wide. The fuel tanks looks a bit small however, not sure how heavy the capsule is and this think looks single stage. 
That is unless it has an docked drop tank you drop before landing. This makes sense here, not fully reusable but the fuel tank is pretty cheap and you need to bring in fuel anyway. 

 

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2 minutes ago, magnemoe said:

It needs an large fairing, Looks like its 7-9 meter wide. The fuel tanks looks a bit small however, not sure how heavy the capsule is and this think looks single stage. 

Turn it sideways, it fits in a 5m fairing.

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Just now, tater said:

Turn it sideways, it fits in a 5m fairing.

Thought about it, will create plenty of sideways forces however, but you could launch it dry, this makes some sense as you do not need it to handle 3 g load fully loaded anyway. 

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27 minutes ago, magnemoe said:

Thought about it, will create plenty of sideways forces however, but you could launch it dry, this makes some sense as you do not need it to handle 3 g load fully loaded anyway. 

Is it that hard to make it survive lateral loading? Structure looks pretty robust.

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55 minutes ago, tater said:

Is it that hard to make it survive lateral loading? Structure looks pretty robust.

It has a nice scaffold around it that should allow lateral loading without problems.

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