jadebenn

A little birdie told me of a big find of his, and oh man, this is some pretty exciting tech. As part of the modifications made to 39B for SLS, NASA is building a new LH2 tank to replace the Apollo-era one currently in use. This tank is being built to utilize a new NASA-developed technology called Integrated Refrigeration and Storage (IRaS). Not only does this allow for zero-boiloff storage of LH2, but it allows it to be cooled further below boiling temperature to a densified, or even solid, state. In fact, according to a NASA paper on the technology, "It is estimated that densification at the 46% fill level produced the largest single batch of solid hydrogen in history: 1,020 kg, with a solid-to-liquid mass fraction of 25%, or around 11,780 L of solid material." Similar to the RP-1 densification employed by SpaceX, this would allow greater performance of hydrogen rocket stages. With this capability soon to be available to them with the new LH2 sphere at 39B, NASA appears to be investigating the possibility of using it to further boost the performance of SLS. The NASA paper from 2016 that set out the project in the first place stated it would, "...culminate with an operational demonstration of the loading of a simulated flight tank with densified propellants." The page of a follow-up project investigating the use of densified LH2, the Autonomous Propellant Loading Project, includes the claim that a 10% or more gain in SLS ascent performance(!!!) is possible. Overall, this really exciting technology! It's unfortunate it seems to have mostly flown under the radar 'till now.

There's no organized conspiracy to delay CCrew so SLS launches first.

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

Yeah. There's been a lot of weirdly punitive takes after the MET debacle, talking about how NASA could force Boeing to fly another OFT because it's in their contract, and stating all the ways NASA could (and often implying they should) screw them over and force Boeing to spend more money. Thing is, the last thing NASA wants to do right now is take any moves that could result in CCrew falling further behind schedule. They're already facing a bad enough "Soyuz crunch" in 2020 as-is. They're not going to rake Boeing or SpaceX over the coals unless they literally have no other choice. If both parties to a contract agree it should be changed, they can do (just about) whatever they want with it.

To be fair, I was under that impression at first as well. It's only upon further reading that I realized they meant they hadn't left quite yet.

One of the NASA image captions states that the initial transporters were only designed for internal factory use (well, to be more precise, the blue equipment siting on top of them was) and can't navigate inclines. The ones it's on now collectively act as the equivalent of the strongback used in the STS days, capable of navigating the (comparatively) rough road surfaces to the barge. They also had to attach some rigging to it for transit. I don't know the exact details there, though. The first tweet was actually of it rolling into the building. They were moving it to a place where they could prep for ship.

Do you really need to ask? No. It's completely untreaded ground.

I think you're underestimating the difficulty of building a reinforced concrete structure on another celestial body. Look at how much effort goes into building one on Earth, then consider you have zero local infrastructure, an extremely limited amount of construction materials, and an absolutely tiny construction crew working in one of the most hazardous environments known to man. Building the pad alone would almost certainly be a multi-year effort.

If a 40 ton lander does that, that's yet another nail in the coffin of the boneheaded idea of bringing down an entire Starship to the Lunar surface.

I will guarantee you it will not be anywhere near tall enough for that. This is the service gantry the Titan IV used: Now imagine how large one neccessary for Starship would be.

The structure will probably look pretty similar to the old Titan IV Mobile Service Tower (MST) that used to be at SLC-40, though since SpaceX uses off-site payload encapsulation, they should be able to drop the cleanroom aspect. At least, presuming that late access to the payload isn't required. Not quite. But they're working on it.

The first SLS core is preparing to leave Michoud Assembly Facility.

I have acquired a graphic listing the EUS specs as of 2018. I will compare it to the one @tater showed. Dry weight is roughly 1,000 lbs lighter for the new EUS (28,940 lb versus 30,000 lb to 31,000 lb) Propellant weight actually seems to be a fair bit lower (though this may have been an oversight or mistake in the new graphic, as the number seems nonsensically low if it's truly referring to the "wet" weight of the whole stage and not just the weight of the propellant itself). Stage height has decreased (~17.6 m versus 17.8 m) Overall, the new EUS design is actually a bit smaller than the old one, even though it has greater performance.

Right, but the BOLE SRBs are actually supposed to be cheaper in addition to having more performance and being essentially drop-in ready. I would honestly be surprised if they decided to completely exhaust the ASRM stock before switching; Those are powerful incentives. Anyway, NASA and Boeing look ahead to long-term SLS production There's some interesting info about the production rate in there too:

They could phase-in the BOLE SRBs earlier if necessary. I have a feeling they might once OmegA is flying.

The SRBs in that render look like the standard Shuttle ASRM casings, just without the photometric markings. SRB replacement must take place by flight eight due to depletion of the Shuttle casings. The program for this is already underway and is known as the Booster Obsolescence and Life Extension (BOLE) program. I've talked about it on here before, but I'll go over it again quickly for the benefit of outside observers. Basically, OmegA and Shuttle will use nearly-identical SRBs. Same dimensions, casings, propellant, hydraulics, etc. Very minor differences. This is possible because NGIS was smart and knew this situation would occur, so they designed OmegA around the SRBs they were developing for SLS, and not the other way around. Biggest changes are lightweight composite casings, new propellant (apparently just about nobody makes the type Shuttle used these days), no more hypergolics for the flight control systems (they'll be electric), and quite a jump in thrust. SLS with BOLE SRBs will actually be pushing the structural limits of pad 39B's flame trench, with somewhere in the neighborhood of 10-11 million pounds-force of thrust at liftoff compared to the Saturn V's 7-8 million. Thankfully, the pads were overbuilt for the Nova rocket that never materialized, so they should be able to handle anything below 12 million pounds-force of thrust. Anyway, part of the confusion, @tater, is that carrying the Universal Stage Adapter (USA) through the TLI burn on crewed SLS imposes a payload penalty compared to cargo SLS; About roughly two tons of TLI payload. So the lowest payload figures will universally be for the crewed variant. Then there's the fact that not only has the EUS been uprated a few times, but there's also less payload margin being held in reserve as the design matures. So the exact performance of EUS was already murky before this press release, and this only complicates matters. We know it's more than the original 37 tons to TLI, but we don't know by how much.

Boeing is reporting that CDR of EUS components is complete They're quoting 45 tons to TLI performance now, which is very interesting. I was under the impression the BOLE SRBs were required to reach that level, but the implication seems to be that this is just the new EUS performance baseline. Can't make any definitive conclusions with just a press release, though.

They're building a second LH2 sphere at 39B: The extra capacity will be used for Block 1 launch scrubs and for filling the EUS on Block 1B. Considering the OIG estimated an SLS cost at $876M, that doesn't pass a smell test.

EUS will be using RL-10s. Fun fact: Each of the three new LVs that will be using RL-10s (Vulcan, OmegA, SLS) has received a proposal from Blue Origin to use BE-3Us instead. Every single one turned them down.

Exploration Ground Systems is in charge of the SLS infrastructure at KSC. I think KSC itself is in charge of most of the multi-user facilities, but don't quote me on that. For example, the MPPF and PHSF are sometimes used by the LSPs too. I'm not sure who owns either of those facilities, but I'm fairly confident it's the space center management (and not NASA) that operates them. Anyway, EGS is not a big money sink. The contract they awarded to modify High Bay 3 of the VAB was a fixed price contract of only about a hundred million dollars. They were a bit late on it, but no-one really cared since SLS was even later. As far as I can tell, it's the fabrication and modification of the Mobile Launcher(s) that's been the real money sink. Even then, IIRC, the cost-plus contract they awarded to convert the Ares I ML for SLS came in pretty close to the initial estimates. The real waste there (modifying a never-used ML) was Constellation's fault.

Here's a diagram of SLS's process flow (for cargo Block 1B): I've done my research, and I can confirm all the facilities pictured here currently exist. The "Spacecraft Processing Facility" is the Multi-Payload Processing Facility (MPPF), which has already been equipped for Orion and could also handle SLS payload encapsulation if necessary. The generic "Processing Facility" is the Payload Hazardous Servicing Facility (PHSF), which would be the primary facility for payload encapsulation and would also handle processing of the EUS. SLS's processing flow is actually very similar to the Atlas V's: Pretty much all the vehicle and payload operations are conducted off-pad. Here's an image for comparison:

This really is a topic that should be in its own thread.

True. But at the same time this failure mode shouldn't be hard to mitigate. Like I said, a lot depends on the specifics.

NASA wants to start procurement of an unpressurized lunar rover for the Artemis program. NASA to seek ideas for an Artemis lunar rover My reaction can be summed up in two words: Heck yeah! While a pressurized Lunar rover remains the holy grail of Lunar surface exploration vehicles, the capabilities an unpressurized rover provides are still nothing to sneeze at. It was such a game-changer on the late Apollo missions, and it still remains a huge shame it wasn't part of the earlier missions.