NASA Human Landing System

[wumpus]

19 hours ago, mikegarrison said:

Well, I guess they are lucky you aren't the one they have to convince.

Presumably the only way to convince NASA would be to cut the price down to what Congress authorized.  Doing an end-run around NASA and convincing Congress might work better.

[Beccab]

1 hour ago, wumpus said:

Presumably the only way to convince NASA would be to cut the price down to what Congress authorized

Actually no, that wouldn't work. Lunar Starship was the highest rated of the three without including the cost, and was even awarded the contract before starting to rediscuss the dates of the milestones to fit the payment. So even if BO actually halved their cost again they would still have a lower rating than Spacex, and thus to be selected together with them would still need Congress to double the HLS founds (and which would still be half the money NASA had originally requested)

[YNM]

2 hours ago, wumpus said:

Doing an end-run around NASA and convincing Congress might work better.

A lawsuit kinda suits in it perfectly.

26 minutes ago, Beccab said:

[...] Even if BO actually halved their cost again they would still have a lower rating than Spacex, and thus to be selected together with them would still need Congress to double the HLS founds (and which would still be half the money NASA had originally requested)

I do have one worry however. Funding in a lot of cases, even with partial funding, means that you have the obligation to it. In this case, NASA is only owed half the obligation of what developing Starship for HLS capability is. The rest goes to SpaceX itself, where HLS capability merely represent a subset of what Starship could achieve in their own milestone. My real question is where will they cut the line on calling it "ready for HLS" ? I'm mostly worried by the fact they put out "half or less" - ie. there's chance that they'd be developing something additional and it'll affect HLS deployment even if it's not actually needed in HLS. Now yes flying a vehicle that's closer to perfection is always better - you want every doubts to be down in the mud, if possible - but this could represent one risk that the timescales might slip.

That being said, given SLS itself has a rather... terrible time schedules (yet the program is dependent on it), and the rest of the bidder couldn't even make something more believable than Starship's bid, then the point is somewhat moot in this specific case. But it is a point in any case.

Edited April 28, 2021 by YNM

[tater]

Lawsuits are standard in these cases.

[wumpus]

21 hours ago, Beccab said:

Actually no, that wouldn't work. Lunar Starship was the highest rated of the three without including the cost, and was even awarded the contract before starting to rediscuss the dates of the milestones to fit the payment. So even if BO actually halved their cost again they would still have a lower rating than Spacex, and thus to be selected together with them would still need Congress to double the HLS founds (and which would still be half the money NASA had originally requested)

The point is that Congress will still have the last word.  If they want to hand it to BO, they could always include a maximum height requirement in the funding or something else Spacex can't achieve.  I doubt they like to do this on a regular basis considering just how many contracts are out there (I think the Pentagon decided who would build each generation of fighter jets (a far more massive contract), and Congress didn't override them.  But almost all the criteria were political).  I think Congressional overrides are more typical in changing how much they will buy/pay for.  And often they insist on paying more than the original customer wants (typically big defense contracts, but the SLS is a great example.  I can't imagine NASA like seeing all their budget go to that).

But they'll still need an act of Congress even with a winning lawsuit.

[sevenperforce]

Hating on SLS, as always, but it occurred to me that coming up with something better isn't particularly straightforward.

I mused that it would be nice to see those SRBs swapped out for paired F-1Bs (e.g. Pyrios concept), the RS-25s swapped out for a cluster of Raptors, and extra RL-10s added to the EUS. But after running the numbers, I actually ended up with a lower throw weight to TLI. So that was disappointing.

If the objective of SLS was to throw something actually useful to TLI and you could swap out any of the engines (keeping in mind that you will need to adjust tank strength to account for increased propellant load), what would you choose? You can use any engines that have actually been built and that you have specs for. You just have to keep the overall stack dimensions the same within a 2.5-stage architecture (otherwise it is no longer an apples-to-apples comparison).

Edited April 29, 2021 by sevenperforce

[RCgothic]

Well I wouldn't go 2.5 stages for starters. I'd go for a full three stages. 2 to LEO and a 3rd for earth departure.

Lugging that huge core to LEO really kills it.

That said, the US didn't really have any good engine choices back in 2010.

Edited April 29, 2021 by RCgothic

[sevenperforce]

54 minutes ago, RCgothic said:

Well I wouldn't go 2.5 stages for starters. I'd go for a full three stages. 2 to LEO and a 3rd for earth departure.

Lugging that huge core to LEO really kills it.

But if you were going to go 2.5 stages......

55 minutes ago, RCgothic said:

That said, the US didn't really have any good engine choices back in 2010.

Assume you could use any engines.

[YNM]

12 hours ago, sevenperforce said:

Hating on SLS, as always, but it occurred to me that coming up with something better isn't particularly straightforward.

Not really straightforward when we're this far down the execution.

There were actual tests with an old F-1 engine as well as merely the turbopumps I think. Obviously it's not great when all the hardware are ages old. J-2X design and testing was underway but was terminated in 2014 due to 'lack of funds'.

Shuttle-derrived designs are going to be limited by what the Space Shuttle was. If you really want to make something much more capable you better design things for the ground up again, or at least use parts of the design that the Space Transportation System design also included (ie. tugs and all). But since the Shuttle was deemed way too dangerous towards the end of it's career (not due to age but due to the inherent design), and the basis of STS is the Shuttle itself, then that means the whole plan just don't work.

Starship and Superheavy on the other hand are designed to meet the advanced capabilities they're supposed to reach one day. It's not for no reason they're 9 m in diameter. It might not going to fly as quickly as we did for Saturn V (from concept to actual flight), but it's designed for it's mission from the start.

Edited April 30, 2021 by YNM

[tater]

5 hours ago, sevenperforce said:

If the objective of SLS was to throw something actually useful to TLI and you could swap out any of the engines (keeping in mind that you will need to adjust tank strength to account for increased propellant load), what would you choose? You can use any engines that have actually been built and that you have specs for. You just have to keep the overall stack dimensions the same within a 2.5-stage architecture (otherwise it is no longer an apples-to-apples comparison).

I wonder if Be-4 can burn hydrogen. It's 2400kN vs 1860kN for RS-25, so even losing thrust, it should still exceed RS-25 capacity. I say this because we know they are cheap (Tory Bruno rocket cost math places them at under $7M each).

Next are the ridiculously overprices SRBs. As long as the thrust is the same, the core should be able to deal with any drop-in replacement. You'd need something akin to NG S1, 6 Be-4 (burning LNG) (a NG S1 is 3.5m longer than a 5 seg SRB)

[sevenperforce]

4 hours ago, YNM said:

Shuttle-derrived designs are going to be limited by what the Space Shuttle was. If you really want to make something much more capable you better design things for the ground up again, or at least use parts of the design that the Space Transportation System design also included (ie. tugs and all). But since the Shuttle was deemed way too dangerous towards the end of it's career (not due to age but due to the inherent design), and the basis of STS is the Shuttle itself, then that means the whole plan just don't work.

Starship and Superheavy on the other hand are designed to meet the advanced capabilities they're supposed to reach one day. It's not for no reason they're 9 m in diameter. It might not going to fly as quickly as we did for Saturn V (from concept to actual flight), but it's designed for it's mission from the start.

But for all its splendidness Starship+Superheavy can't actually match the TLI throw of SLS, not without refueling. Two stages with methalox can't beat 2.5 stages of hydrolox boosted by solids.

Obviously refueling is Starship's whole shtick, but still.

I'm all about encouraging criticism of Shuttle-derived designs but all I'm saying to keep is the tank diameter and total vehicle height, which is hardly Shuttle-derived at all. 

I suppose you could shrink the core vertically and stretch the upper stage and see if that helps.

1 hour ago, tater said:

I wonder if Be-4 can burn hydrogen. It's 2400kN vs 1860kN for RS-25, so even losing thrust, it should still exceed RS-25 capacity. I say this because we know they are cheap (Tory Bruno rocket cost math places them at under $7M each).

Next are the ridiculously overprices SRBs. As long as the thrust is the same, the core should be able to deal with any drop-in replacement. You'd need something akin to NG S1, 6 Be-4 (burning LNG) (a NG S1 is 3.5m longer than a 5 seg SRB)

That 452 seconds of vacuum isp on the RS-25 is pretty hard to beat.

Six or seven BE-4s will definitely beat the hell out of the SRBs. So would a cluster of Raptors in the Big Falcon configuration.

[tater]

55 minutes ago, sevenperforce said:

That 452 seconds of vacuum isp on the RS-25 is pretty hard to beat.

Yes, but Be-4 can air start and deep throttle.

I don't see a reason why it would have a grossly lower Isp than RS-25 if it was instead using the existing tanks to burn hydrogen. The likely ~339s Isp of Be-4 in vacuum is a function of the engine design, and the CH4, after all.  Other engines have been used with different fuels, maybe a hydrolox version is possible.

The NG side boosters could of course be recovered.

Edited April 30, 2021 by tater

[RCgothic]

3 hours ago, sevenperforce said:

But for all its splendidness Starship+Superheavy can't actually match the TLI throw of SLS, not without refueling. Two stages with methalox can't beat 2.5 stages of hydrolox boosted by solids.

Pretty sure expendably it can. Reuse eats a lot of margin both in dry mass and fuel reserved.

[YNM]

7 hours ago, sevenperforce said:

But for all its splendidness Starship+Superheavy can't actually match the TLI throw of SLS, not without refueling. Two stages with methalox can't beat 2.5 stages of hydrolox boosted by solids.

Obviously refueling is Starship's whole shtick, but still.

It eliminates the need for a dedicated transfer vehicle for the case of Mars if we're comparing to most NASA-sponsored plans. It's not really designed for the Moon, but it's well in the capability if we're using the Mars-destined design.

7 hours ago, sevenperforce said:

I'm all about encouraging criticism of Shuttle-derived designs but all I'm saying to keep is the tank diameter and total vehicle height, which is hardly Shuttle-derived at all. 

I suppose you could shrink the core vertically and stretch the upper stage and see if that helps.

That hardly makes anything shuttle-derrived... If they were to replace the SRBs with LRBs powered by F-1s and replace the main engine with something better than the SSMEs (new ground-up design LH2/LOX engine that's designed to be thrown away), and the 2nd stage utilize J-2X, would that be Shuttle-derrived or Apollo-derrived ? We're using like, two Apollo-derrived engines by that point.

Edited April 30, 2021 by YNM

[tater]

SLS long since dumped Shuttle derived.

 

[YNM]

34 minutes ago, tater said:

SLS long since dumped Shuttle derived.

Fact that they use an expensive SSME only to be thrown away and retain the exact same SRBs makes it as Shuttle-derived as much as possible w/o the Space Shuttle being used itself. There were plans to fly Centaur on Shuttle so will say that even the use of RL-10 is Shuttle-derived.

Edited April 30, 2021 by YNM

[tater]

2 minutes ago, YNM said:

Fact that they use an expensive SSME only to be thrown away and retain the exact same SRBs makes it as Shuttle-derived as much as possible w/o the Space Shuttle being used itself. There were plans to fly Centaur on Shuttle so will say that even the use of RL-10 is Shuttle-derived.

The SRBs are 5 segment, so a multi-billion dollar total redo, and at multiples of the constant dollar cost of the Shuttle SRBs.

The tanks are the same diameter, but otherwise unrelated, and at vastly higher cost. There is no reason for the core stage (tanks) to cost more than maybe $200M, and the cost is unknown except 3 tanks for $6.7B including dev.

Shuttle derived would have been sticking engines on a Shuttle external tank with an interstage added, and some upper stage.

[YNM]

5 minutes ago, tater said:

Shuttle derived would have been sticking engines on a Shuttle external tank with an interstage added, and some upper stage.

Will say that it's a bit odd to think that Shuttle + payload was 110 tonnes max (launched to LEO) yet SLS Block 1 payload to LEO is only 95 tonnes max. Perhaps to do with not carrying the engines to orbit but it's weird that they need an extra segment and one more engine.

[sevenperforce]

7 hours ago, RCgothic said:

Pretty sure expendably it can. Reuse eats a lot of margin both in dry mass and fuel reserved.

If you reuse the Superheavy booster but expend the Starship, its TLI performance comes very close to SLS Block 1. It depends on how stripped-down you can make the Starship. At 60-65 tonnes dry it matches Block 1 almost perfectly.

Block 1B of course has significantly higher throw. Not sure whether expending the Superheavy booster would raise dV enough to match.

6 minutes ago, tater said:

6 hours ago, YNM said:

That hardly makes anything shuttle-derrived... If they were to replace the SRBs with LRBs powered by F-1s and replace the main engine with something better than the SSMEs (new ground-up design LH2/LOX engine that's designed to be thrown away), and the 2nd stage utilize J-2X, would that be Shuttle-derrived or Apollo-derrived ? We're using like, two Apollo-derrived engines by that point.

The tanks are the same diameter, but otherwise unrelated, and at vastly higher cost. There is no reason for the core stage (tanks) to cost more than maybe $200M, and the cost is unknown except 3 tanks for $6.7B including dev.

Shuttle derived would have been sticking engines on a Shuttle external tank with an interstage added, and some upper stage.

Yeah, if SLS was still "Shuttle-derived" after stretching the main tank, un-stretching it wouldn't make it any less Shuttle-derived.

The most Shuttle-derived part of SLS is the concept of taking a massive first-stage tank with heavy first-stage engines just to the edge of orbit and then dropping it. Which was also the most inefficient thing about the Shuttle.

[sevenperforce]

There are also more exotic solutions, like jettisoning SSMEs mid-flight. But seriously that core is.....just so heavy.

[Silavite]

11 hours ago, tater said:

Yes, but Be-4 can air start and deep throttle.

I don't see a reason why it would have a grossly lower Isp than RS-25 if it was instead using the existing tanks to burn hydrogen. The likely ~339s Isp of Be-4 in vacuum is a function of the engine design, and the CH4, after all.  Other engines have been used with different fuels, maybe a hydrolox version is possible.

The NG side boosters could of course be recovered.

The idea of a BE-4 modified for hydrolox has some precedent in the LR87, since it was originally designed for kerolox and then was made to use hydrolox and storables in separate variants. That said, the LR87 used a relatively simple gas generator cycle as opposed of the BE-4's oxidizer rich staged combustion cycle.

In addition, most hydrolox staged combustion engines (save for perhaps the RD-701) use fuel rich staged combustion. Perhaps it would be possible to stick with the oxidizer rich cycle, but modifying a staged combustion engine to burn different fuel seems (to my untrained eye) like it would be difficult.

[Guest]

Get rekt, Dynetics, Blue Origin, and Lockheed Martin 

SPACEX IS KING   

Edited April 30, 2021 by SpaceX_Boi
comma

[SpaceFace545]

42 minutes ago, SpaceX_Boi said:

Get rekt, Dynetics Blue Origin, and Lockheed Martin 

SPACEX IS KING   

not really, NASA just couldn't afford a real solution.

[kerbiloid]

So, is LOP-G  now obsolete?

And Orion.
(Not that, true atomic Orion, but this, Apolloid one.)

Edited April 30, 2021 by kerbiloid

[sevenperforce]

Could prove useful.