NASA finally acknowledges the elephant in the room with the SLS rocket

"You know, you're right, the flight rate—three years is a long time."

See full article...

 

[theradicalmoderate]

I don't believe the existing NG has the performance to put a human lander down to the moon without refueling. If they're betting on that, they're likely betting on having their 9x4 rocket ready.

Nope, but it can launch one BM1.5 (i.e., a BM1 with a small crew module), and two proto-CTs (I suspect that a CT is just a BM1 with everything stripped off that isn't needed for the crew or landing), and that'll do the trick--just barely.

Bat chart:

And maneuvers with prop consumption:

(Pay no attention to the "tankers needed" lines. The spreadsheet started out life as a Starship tool.)

It's very, very tight, and obviously makes lots of assumptions about the dry mass of the BM1 and CT. But it seems to work with a 3t crew module, which is what the BM1 is supposed to be able to land one-way. The trick is to find the delta-v necessary to get the BM1.5 back to LLO, where a second CT can pick it up and take it back to NRHO. This conops does that by making the first CT, which picks the BM1.5 in NRHO and delivers it well below LLO, making the CT a crasher.

Note the extraordinarily low boiloff numbers. But if Blue can't get to near-ZBO, they're gonna be in trouble no matter what. So they need all the prop storage tech, but they could forgo the refueling.

 

[Wickwick]

Nope, but it can launch one BM1.5 (i.e., a BM1 with a small crew module), and two proto-CTs (I suspect that a CT is just a BM1 with everything stripped off that isn't needed for the crew or landing), and that'll do the trick--just barely.

Bat chart:

View attachment 127773

And maneuvers with prop consumption:

View attachment 127776

(Pay no attention to the "tankers needed" lines. The spreadsheet started out life as a Starship tool.)

It's very, very tight, and obviously makes lots of assumptions about the dry mass of the BM1 and CT. But it seems to work with a 3t crew module, which is what the BM1 is supposed to be able to land one-way. The trick is to find the delta-v necessary to get the BM1.5 back to LLO, where a second CT can pick it up and take it back to NRHO. This conops does that by making the first CT, which picks the BM1.5 in NRHO and delivers it well below LLO, making the CT a crasher.

Note the extraordinarily low boiloff numbers. But if Blue can't get to near-ZBO, they're gonna be in trouble no matter what. So they need all the prop storage tech, but they could forgo the refueling.

So you're proposing to have two landers attached to one another with a mission-critical separation event on the way to the lunar surface and another mission critical rendezvous in LLO between the surface and NRHO? And this is better than refilling how?

 

[theradicalmoderate]

Mystery solved. Thanks. I even wondered if that was the case but saw multiple (obviously incorrect) cite of the mass being to 200 km reference orbit which it obviously is not. The only published mass to orbit is this irregular orbit while essentially everything else (US) is to a 200 km circular 28.5 deg reference orbit.

It also makes sense that Block 1b (EDS) doesn't really improve payload mass to LEO. It is largely for the improvement to TLI.

Note that I went back and actually did the computation for how much residual prop you'd have if you went to 200x200 instead of 70x1800,¹ and it didn't exceed 80t. I suspect that the core has monster residuals.

With the EUS, things are harder to figure, because it's heavy enough that the core can't get it and the USA+SCA+ESM+CM stack into LEO; the EUS has to help out. But if somebody were to build the mythical cargo fairing for Block 1B, it would indeed get a lot more payload to LEO.

Not gonna happen--ever.

___________
¹Semi-pedantic note about this weird orbit: The goal is to get as much energy as possible, so the ICPS has enough delta-v to get things all the way to TLI, while still ensuring safe disposal of the core. So the perigee is designed for auto-reentry, while the apogee is as high as they could get. That's why the ICPS has to do the apogee burn before the Orion separates. Otherwise, the ICPS+Orion would reenter instead of doing the TLI. That's also a safety feature in case the ICPS burn fails: just separate the CM and it'll go straight home with no delta-v at all.

Arty 2 numbers are slightly different, but it's the same basic idea for the initial parking orbit. But it doesn't go straight to TLI. Instead, the ICPS puts Orion into a 378x109,000km orbit with a 42hr period, allowing the crew to do prox ops tests with the ICPS, and ensure that the ECLSS system is performing, before the Orion takes the crew into the TLI/free return trajectory. The free return is needed because the Orion has to send itself to TLI, and there isn't enough delta-v left to get into and out of NRHO. Kinda clever from a crew safety standpoint, but not very satisfying from a space nerd's perspective.

 

[wagnerrp]

The real answer is that SLS Block 1's payload to LEO is exactly the mass of the ICPS + Orion, because that's the only payload it can carry. Ain't no stinkin' cargo fairing, man.

The SLS SRBs + core put the ICPS+Orion (65.5t) into a ~70 x 1800km orbit, which has the same energy as a 932km circular orbit. That's 635m/s above a 200x200 orbit. From there, you have to do some figuring to determine how much residual prop you'd have in the core if you went to the lower altitude. That, plus the 65.5t, should be the mass to the reference LEO.

I'm just gonna do the calculation: RS-25 has an Isp=452.3s, and the core has a dry mass of 85,275kg. exp(635/452.3/9.807) = (Mdry + extraProp) / Mdry.

So extraProp = 13.1t. Add that to the 65.5t that it actually takes to 70x1800, and you have 78.6t. I don't know where the 95t comes from. Maybe they have monster residuals on the Block 1 launches?

Wikipedia cites some twitter post claiming 98t dry, and assuming MRS, and even empty, those tanks are going to have around 1t/bar of ullage gas. MRS is likely on the order of 105-110t. And you need to add the 65t of Orion/ICPS to that to measure the propellant burn.

 

[theradicalmoderate]

So you're proposing to have two landers attached to one another with a mission-critical separation event on the way to the lunar surface and another mission critical rendezvous in LLO between the surface and NRHO? And this is better than refilling how?

Well, a lander and a CT, which is probably about 90% the same as two landers. And yeah, the crasher separation event is... mission-critical.

The reason it's better than refueling is because Blue doesn't have to do the work to turn the GS2 into a tanker, and work out all the RPOD details between the CT and the GS2. It also doesn't require a CT to refuel the BM2 in NRHO.

It's a fairly clean evolutionary step, however, between a one-way BM1 and the full-up BM2 they're planning on using for the SLD/SLT HLS missions. If you look at what's needed between the BM1 that's supposed to be tested this year and the BM2:

Increase BM1 size to BM2: not needed (crew module payload is 3t-ish)
Get ZBO working for both BM and CT: needed
GS2 to CT RPOD and refueling: not needed
CT to BM RPOD : needed
CT to BM2 refueling: not needed
CT-BM separation mechanism: needed

The wasted step is putting the small crew module on the BM1 between the tankage and the thrust structure, à la BM2. I don't think this is particularly hard, but the structure will have to change for the BM2 to support a bigger crew module, and the small crew module is a throwaway. But it's also a nice pathfinder for the full-up BM2 crew module.

 

[theradicalmoderate]

And you need to add the 65t of Orion/ICPS to that to measure the propellant burn.

Ah! Yup, that's an error. That takes it up to 88.7t. I'll fix it.

 

[SpikeTheHobbitMage]

Boil off is unavoidable and taking 17hrs before the start of venting says just as much about the state of fill in the tank as it does the rate of boil off. I would take any value from that specific number.

Your previous point about needed high quality vacuum, is that a vacuum pump onboard? They couldn’t seal their vacuum lines? Or have the fueling station do it as part of the fueling process? The boil off would go to powering various standby systems while the vehicle is stationary, like a pump.


It’s a problem that plagues rocketry too. Hydrogen in any achievable form is very low density, and very low energy density. You can’t force a lot of it into a combustion chamber, nor can you force a lot of it into a piston, so engines need to be large and heavy with low specific power.


The fueling system would certainly need to be designed to prevent gasoline hydrogen fights.

The fuel tank is a thermos bottle with a high vacuum insulation layer. I would expect it to be welded together rather than screwed but potential outgassing from contaminated metal and hydrogen diffusion through the tank wall would still be concerns.

 

[SpikeTheHobbitMage]

When you use hydrolox for your main stage, you are swapping a huge increase in costs/complexity for a minor performance increase.. Huge increases in tank mass/volume and no one has ever stopped the leaks.

When you use hydrolox for your upper stage, you are chasing performance at the cost of economics.

When you use it for deep space, you are fighting against boiloff.

The sole use of hydrogen should be as propellent for nuclear thermal engines, where its basically a requirement to achieve high ISPs.

Even using argon a nuclear electric ion thruster would still have between two and three times the ISP of a nuclear thermal engine. (2500s vs 850-1000s) The only place for hydrogen is when you need extremely good regenerative cooling, such as Stoke Space's engine/heat shield hybrid.

 

[SpikeTheHobbitMage]

I've said for years it would have been more cost effective to pay all the non-management individuals working on the program the same amount directly to do literally nothing, and there'd likely be enough left over to fund a competently-run program to build a launcher with the same capabilities

Ah, but where would that saved money come from? It would no longer be flowing into the pockets of the very same wealthy insiders promoting the current system. This is why we can't have nice things.

 

[Wickwick]

Well, a lander and a CT, which is probably about 90% the same as two landers. And yeah, the crasher separation event is... mission-critical.

The reason it's better than refueling is because Blue doesn't have to do the work to turn the GS2 into a tanker, and work out all the RPOD details between the CT and the GS2. It also doesn't require a CT to refuel the BM2 in NRHO.

It's a fairly clean evolutionary step, however, between a one-way BM1 and the full-up BM2 they're planning on using for the SLD/SLT HLS missions. If you look at what's needed between the BM1 that's supposed to be tested this year and the BM2:

Increase BM1 size to BM2: not needed (crew module payload is 3t-ish)
Get ZBO working for both BM and CT: needed
GS2 to CT RPOD and refueling: not needed
CT to BM RPOD : needed
CT to BM2 refueling: not needed
CT-BM separation mechanism: needed

The wasted step is putting the small crew module on the BM1 between the tankage and the thrust structure, à la BM2. I don't think this is particularly hard, but the structure will have to change for the BM2 to support a bigger crew module, and the small crew module is a throwaway. But it's also a nice pathfinder for the full-up BM2 crew module.

Well, a staged descent module will be a new one for the books.

 

[MeValeMadre]

"Every SLS rocket is a work of art, every launch campaign an adventure, every mission subject to excessive delays." "...the SLS rocket is dead hardware walking".

Yup, that about sums SLS, Orion, Gateway, and, if it doesn't change fast, NASA up.

 

[Xavier1908]

I'm just spitballing here but has NASA tried just wrapping a ton of duct tape around the seals?

 

[Xavier1908]

The chief supporters include Texas Senator Ted Cruz and Shelby's replacement in the Senate, Katie Britt. Cruz and his staff have been doing a lot of the heavy lifting of late.

Since SpaceX is now based out of Texas shouldn't that sway Ted Cruz, with SpaceX's lobbying dollars, to support using Starship instead?

 

[Tom the Melaniephile]

Falcon Heavy wasn't adequate, because it didn't come with a deep-space-capable capsule, and it couldn't get Orion to TLI.

Until there's something that can get a crew from Earth's surface to lunar orbit, there's at least a flimsy argument that SLS/Orion provides a service that nobody can match. But the moment that HLS Starship is crew-certified, that will no longer be true.

For a lot less than a single SLS + Orion launch ($5B+), we could have paid to develop a deep-space version of Dragon.

 

[Wickwick]

Since SpaceX is now based out of Texas shouldn't that sway Ted Cruz, with SpaceX's lobbying dollars, to support using Starship instead?

"Local jobs" is only the justification politicians use when they can. Corporate bribes lobbying dollars are what the politicians really want. OldSpace companies are really good at spreading lobbying dollars around.

 

[miker289]

'Flourine' is a mineral useful in baking. Or did you guys mean 'Fluorine'?

Yeah, that one. Thanks!

 

[Dtiffster]

Well, a staged descent module will be a new one for the books.

It is the same approach that the Chinese are using with their lander (Lanyue Lander). The descent stage inserts them into lunar orbit and handles the descent, then separates and crashes while the ascent stage finishes the soft landing.

 

[DragonDeborn]

Since you mentioned Ares I, I have an excuse to mention that the displays were going to have to strobe in-phase with the expected vibrations or else none of the passengers would have been able to read anything.

It's a cool solution to a problem that should never, ever be allowed to exist.

I thought it was the SLS that had that problem. I had read about the strobing display solution in an article years back. The article had also mentioned that more complicated solutions had been considered, like using springs to dampen the vibrations felt in the Orion.

 

[Wickwick]

I thought it was the SLS that had that problem. I had read about the strobing display solution in an article years back. The article had also mentioned that more complicated solutions had been considered, like using springs to dampen the vibrations felt in the Orion.

SLS inherited the solution I believe. But Ares I was a single-stick SRB rocket. Its vibrations were going to be far worse than SLS.

And yet, SLS still get nixed as the delivery vehicle for the Europa Clipper because its vibrations were still too high.

 

[blackhawk887]

Well, a staged descent module will be a new one for the books.

New for the moon, maybe, but old news here on Earth. Vostok crews "staged" from the capsule mid-descent, that counts as TRL-9 in my book.

 

[blackhawk887]

Since SpaceX is now based out of Texas shouldn't that sway Ted Cruz, with SpaceX's lobbying dollars, to support using Starship instead?

JSC buys more votes employs more people, so the astronaut corps must remain. What vehicle they fly on probably doesn't matter so much, though.

 

[Njut]

Aight, here's my armchair Kerbal engineering modification to the Artemis program to get rid of SLS. I present to you the Starshite architecture! Superheavy (recoverable) launches an expendable Starship ("Starshite") modified to carry the reusable Lunar Ascent/Descent Module (ADM, "Adam") and to perform TLI and LOI burns for the Orion & ESM. After LOI, Orion separates and extracts the ADM, followed by Starshite's deorbit and expeditious encounter with the Lunar surface (disposal). (The next Starshite will not need to bring an ADM, and can instead bring other cargo and extra hypergols to refuel the ADM.) The astronauts transfer to the ADM, land, and deploy the Lunar Cruiser (LC) on the first landing (mobility and temporary non-lander shelter) or Hab module (on subsequent landings).

TL/DR:
Goal: Single launch carries all supplies and fuel necessary for every mission. Superheavy (replaces SLS) lifts modified disposable Starshite (replaces ICPS). Altair lander resurrected as re-usable, fully-hypergolic integrated Ascent/Descent module (ADM); subsequent missions refuel the ADM.

eta: If "Starshite" doesn't strike your fancy, perhaps "Just The Tip" will!

 

[theradicalmoderate]

Well, a staged descent module will be a new one for the books.

Crashers have been modeled extensively. It's definitely a higher-risk mission, with one critical undocking and three critical RPODs, instead of one critical RPOD.

I don't really expect a Blue proposal to be accepted as a replacement for Arty 3--I think that was mostly Duffy-based performative nonsense. But it certainly is something that would look good in an RFI response.

I'm still dying to know what was in SpaceX's RFI response. There's a decent argument to be made that replacing SLS/Orion with D2 + an HLS before Arty 3 could be a schedule acceleration. But it would require demonstrating refueling pretty soon, a huge acceleration in launch cadence, and probably something extremely off-nominal with Arty 2.

 

[theradicalmoderate]

For a lot less than a single SLS + Orion launch ($5B+), we could have paid to develop a deep-space version of Dragon.

Let's suppose D2 magically gets put into TLI. How heavy would it have to be to get into and out of LLO?

D2 as-is is about 12.5t with only enough consumables for a couple of days to the ISS, with 2.6t of prop. (Inert mass=9.9t.) The D2 would have to be able to do TLI-LLO (940m/s) and LLO-TEI (1000m/s), for a total of 1940m/s. If you have Isp=300s Dracos (which won't work without substantially more delta-v due to gravity losses from low thrust), you'd need 9.3t of prop. Add another 0.4t of tankage, 0.2t of consumables, 0.2t of comm and nav gear, about 0.3t of extra heat shield (these are all semi-educated guesses) and now you're at 20.3t.

But FHE can only put 15.5t into TLI (C3=-1.5km²/s²), according to the NASA LSP database. It just doesn't work. It's not even close.

 

[theradicalmoderate]

Aight, here's my armchair Kerbal engineering modification to the Artemis program to get rid of SLS. I present to you the Starshite architecture! Superheavy (recoverable) launches an expendable Starship ("Starshite") modified to carry the reusable Lunar Ascent/Descent Module (ADM, "Adam") and to perform TLI and LOI burns for the Orion & ESM. After LOI, Orion separates and extracts the ADM, followed by Starshite's deorbit and expeditious encounter with the Lunar surface (disposal). (The next Starshite will not need to bring an ADM, and can instead bring other cargo and extra hypergols to refuel the ADM.) The astronauts transfer to the ADM, land, and deploy the Lunar Cruiser (LC) on the first landing (mobility and temporary non-lander shelter) or Hab module (on subsequent landings).

TL/DR:
Goal: Single launch carries all supplies and fuel necessary for every mission. Superheavy (replaces SLS) lifts modified disposable Starshite (replaces ICPS). Altair lander resurrected as re-usable, fully-hypergolic integrated Ascent/Descent module (ADM); subsequent missions refuel the ADM.

eta: If "Starshite" doesn't strike your fancy, perhaps "Just The Tip" will!

You can model this with something like Silverbird (or Kerbal!). If you rip the nose off a Starship, along with the header tanks, TPS, and flaps (say dry mass = 80t), replace it with an Orion stack and some unspecified co-manifested payload, and launch completely expendably, the rocket can put about 50t into TLI. The Orion stack (USA+SCA+ESM+CM with no co-manifest) weighs about 41.6t.

Mind you, this has to stage from NRHO, because Orion sucks, and your co-manifested lander can't exceed 8.4t.

It's not impossible, but it's really, really tight, especially since that 80t dry mass for Starship is probably optimistic, and the 8.4t lander system has to be able to do NRHO-LS-NRHO, which is a delta-v of about 5670m/s.

There are much easier ways to get rid of SLS and Orion without creating a Frankenrocket. Most of them involve launching and recovering a crew on a D2, using one Starship HLS to go LEO-LLO-LEOpropulsive, and a second one to do LLO-LS-LLO. It's basically no additional development beyond what has to be done for the Starship HLS in the first place.

 

[Maltedmothball]

Yes, a cool rocket launch would have been best but a close second would be the thing blowing up...

ah yes a wickwick event as i recall shame it didnt happen

 

[AdrianS]

This is an overblown point. Certainly, there are processing details that were lost, but most of those were very specific to a given piece of equipment using stock from a given supplier. The rocket science (engineering) was well captured and is taught to tens of thousands of students every year. It's almost better to forget these detailed points of expertise or else they can turn into a bit of Cargo Cult Science behavior. It's better to work through them again as needed when new tooling and materials might bump into the same problem.

In my experience working on-and-off for the same company for many decades, what get's lost isn't the "how", it's the "why".

"Why do we do it this way? I know we've done it like that for decades, but no-one remembers what led to that decision."

 

[DDopson]

In my experience working on-and-off for the same company for many decades, what get's lost isn't the "how", it's the "why".

"Why do we do it this way? I know we've done it like that for decades, but no-one remembers what led to that decision."

Yup, and then your supplier changes for one input, or some technology evolves, and you no longer have the fundamental knowledge to understand why you just screwed up the process.

The same guy who wrote "The Lunacy of Artemis" has an interesting post about the history of Scurvy: https://idlewords.com/2010/03/scott_and_scurvy.htm. The gist is that the solved scurvy by giving out lemon juice rations (which they called "limes"), but then subsequently changed to some kind of lime that has a lower vitamin C content, and then as a cost cutting measure, decided to concentrate the lime juice into a syrup, totally destroying the vitamin C. So they broke their scurvy cure, but they didn't notice because it was the 1800's and steam had made voyages short enough that scurvy was no longer a serious risk for regular naval sailors. But then they sent explorations to the poles and had a devil of a time with scurvy because the "lime juice" no longer worked, and there was a bad theory circulating that the lime juice was just a quack cure (false! fresh lemon juice really is a 100% cure for vitamin C deficiency; aka, scurvy).

They remembered the "how", but not the "why", so the "how" eventually got corrupted and it took a lot of gruesome deaths to re-learn the lessons that had been forgotten.

 

[FSTargetDrone]

Obama got a lot of heat for trying to kill this white elephant. Now a decade and a half later he looks like a genius.

Remember even if they succeed on flying this mission without killing everyone onboard. Even if they manage to cobble together enough jury rigged equipment to fly another one and land on the moon, it will be meaningless. This system is simply a total loss. The US will not be able to establish a base and do multiple missions with the SLS. Two more flights and then it will be time to throw away all the work, all the years, all the money and start over with a rocket that isn’t Saturn V Mk. 2. As it stands there the SLS is as obsolete as a B17 on an Air Force base would be today.

B-17’s were actually useful, and some are still flying today about 90 years after the first ones were designed and built (and yes, rebuilt).

 

[FSTargetDrone]

I am hoping when the current nightmare is done that SpaceX is taken over by sober minds, and that Musk is deported to South Africa.

I’d prefer to see him prosecuted, imprisoned and all his assets stripped from him for the massive fraud, waste of resources and destruction of important programs he inflicted on this country.

 

[InvariantCapitalist]

Even using argon a nuclear electric ion thruster would still have between two and three times the ISP of a nuclear thermal engine. (2500s vs 850-1000s) The only place for hydrogen is when you need extremely good regenerative cooling, such as Stoke Space's engine/heat shield hybrid.

imagine if the $30B spent on the SLS had gone into nuclear thermal? Even if only used for unmanned probes, we’d soon have them orbiting and landing on largest moons of Jupiter, Saturn, Uranus and Neptune and the largest dwarf planets in the Kuiper Belt.

 

[Wickwick]

Crashers have been modeled extensively. It's definitely a higher-risk mission, with one critical undocking and three critical RPODs, instead of one critical RPOD.

I don't really expect a Blue proposal to be accepted as a replacement for Arty 3--I think that was mostly Duffy-based performative nonsense. But it certainly is something that would look good in an RFI response.

I'm still dying to know what was in SpaceX's RFI response. There's a decent argument to be made that replacing SLS/Orion with D2 + an HLS before Arty 3 could be a schedule acceleration. But it would require demonstrating refueling pretty soon, a huge acceleration in launch cadence, and probably something extremely off-nominal with Arty 2.

How about missions based on the ISS deorbit vehicle? It uses hypergolic propellants and is basically just a tug. But transfer of hypergolics has been done on-orbit many, many times. Imagine if NASA took the path they threatened they could do with Mars Sample Return. They could select parts from multiple vendors. They could use Blue's lander and SpaceX's tugs and capsules.

 

[Del Varner]

From the article: "some of the smartest engineers in the world," I suggest that these engineers have moved to places like SpaceX where things really get done and progress is actually made.

 

[henryhbk]

If NASA put out an RFP for a commercial Orion launch, SpaceX would definitely propose using Starship. They might submit one using FH as well, but they would prefer to use Starship. Both would be a similar amount of effort, but FH is not the forward-looking product.

It's not forward-looking, but it is the one you can go to the warehouse and launch on Tuesday...

 

[brw02005]

If you can purge so safely that you can have a robot grind the weld bead off, then why not just use that level of purge to capture the escaped hydrogen during the current process?

I don't think you understand if you hard pipe it you can fill it without it leaking which is the problem then you isolate by closing valves and just purge whatever is left in the fill pipe. They are outside as long as vent to a safe location this is perfectly safe. The flexible hose connections is where they are having trouble getting a seal.

 

[brw02005]

Regardless of when the umbilical is connected and disconnected (e.g. after VAB rollout and before main engine start to help with this idea), it cannot be rigid. There will be relative motion between the fill/drain port and launch platform during the propellant loading process, and the umbilical has to accommodate that motion to avoid springing a much more catastrophic leak.

I think many if not most people here understand that thermal contraction occurs when cryogenic fluids are loaded into the tanks. But what may not be as widely understood is that the thrust structure at the base of the core stage is NOT resting on the launch platform. The entire liquid hydrogen tank is hanging over the flame trench, suspended from the intertank crossmember, which transfers the load through the SRB forward attach struts and down the steel SRB casings to the launch platform. The thermal contraction of the entire length of the liquid hydrogen tank causes the position of the fill/drain ports to rise relative to the platform. If the umbilical weren't flexible, it would likely break.

something easially accomplished with EJs (expansion joints ) on a hard pipe. Just they are tig welded and don't leak. Everything moves if big enough and temperature changes. This is solved engineering in my book but your taking about flexible connections with hydrogen a material that can literally phase through a perfectly welded pipe as it is a tiny molecule. This just gets you to the point where if your outside you are nowhere near LEL.

 

[paulfdietz]

The fuel tank is a thermos bottle with a high vacuum insulation layer. I would expect it to be welded together rather than screwed but potential outgassing from contaminated metal and hydrogen diffusion through the tank wall would still be concerns.

Isn't hydrogen diffusion through aluminum negligible, especially at cryogenic temperatures?

 

[blackhawk887]

It's not forward-looking, but it is the one you can go to the warehouse and launch on Tuesday...

Putting Orion on FH would probably cost about $1B in non-recurring expense, and take 2 years if started today. Still cheaper than even a single flight of SLS. But Starship would be a similar cost and time, and has more future value.

 

[Wickwick]

I don't think you understand if you hard pipe it you can fill it without it leaking which is the problem then you isolate by closing valves and just purge whatever is left in the fill pipe. They are outside as long as vent to a safe location this is perfectly safe. The flexible hose connections is where they are having trouble getting a seal.

I misunderstood that you wanted to grid off at the QD face plate.

 

[theradicalmoderate]

How about missions based on the ISS deorbit vehicle? It uses hypergolic propellants and is basically just a tug. But transfer of hypergolics has been done on-orbit many, many times. Imagine if NASA took the path they threatened they could do with Mars Sample Return. They could select parts from multiple vendors. They could use Blue's lander and SpaceX's tugs and capsules.

The USDV, even if stretched, isn’t going to have the delta-v needed to perform the tug roles.

If Blue has solved the hydrolox storage problem for the BM1.5, then they’ve also solved it for the CT. It’s the BM1.5 with the dodgy delta-v budget that causes the need for the crasher. You can’t fix that by souping up the tugs.