sevenperforce

Didn’t seem to have any chute delays on this mission either.

Electric props are not allowed as the challenge says that you can use only monopropellant for propulsion. There's certainly nothing stopping anyway from doing a heavily-clipped version to see how low they can get it, but it's always going to be in a different class than one that uses proper aero.

This is just speculation, but I'd say with Block 1B you could definitely have some issues with an early SSME shutdown I don't think this is likely to be an issue. It certainly won't be an issue before booster separation. At booster separation, SLS has burned less than 27% of its propellant load, so the core still weighs in at a whopping 814 tonnes, plus Orion's 33 tonnes including the abort tower. The difference between EUS (~140 tonnes) and ICPS (~31 tonnes) is significant, but at booster separation Block 1B only weighs about 12% more which shouldn't be enough to cause problems. Plus, Block 1B can fly a less lofted trajectory due to the higher thrust on EUS.

The SLS can manage a single engine loss, as long as it doesn't happen too early in flight. Once SLS is past the initial flight phase, an early engine loss on Artemis I would result in an alternative mission profile to put ICPS and Orion into as lofted a trajectory as possible, thus allowing an accelerated heat shield test without a lunar flyby. If the engine loss happened later in flight, it would do an adjusted MECO but otherwise largely fly the same mission. Late in flight, it can press on to expected MECO just by differential throttling. Loss of more than one engine would be a commanded abort. Here's more discussion of that from NASA: https://ntrs.nasa.gov/api/citations/20205001579/downloads/SLS Engine Out.pdf

I managed an 11.47-tonne solution with a three-stage ascent vehicle where the third stage holds a command chair and is left in LEO to act as the descent vehicle. Munar orbit rendezvous, except that Jeb uses an extra EVA fuel pack to enable an EVA ascent from the munar surface to the command module, which is merely an empty tank with a couple of extra EVA packs in it to enable him to make the burn back to Kerbin. There's a personal parachute for him attached to the third stage. I've tested all the parts independently but I haven't flown the whole mission yet.

Yeah this is puzzling to me. Kind of like with SpaceX spending a bunch of energy trying to catch the fairings in a net and then realizing it was fine to just land them in the water and fish them out. If a quick bath in the drink won't hurt Electron then why go through the trouble of doing the helicopter? I suppose that with proper housings/containment, it would be easier to make electric-pump-driven engines seawater proof than gas generator or staged combustion engines.

When Apollo 4 launched, the sound pressure caused ceiling tiles to drop at a distance of three miles. Once they upgraded the deluge system it wasn't so bad, though. I suspect your organs would start to liquefy somewhere around the three-second mark.

I have absolutely no physics or math to back this up, but I suspect that you will suffer permanent hearing damage before you are close enough to incur other injury. Oh, I think you're absolutely right. I'm assuming it goes: Loud zone Pain zone Eventually deaf zone Instantly deaf zone Physical injury zone Eventually dead zone Instantly dead zone Vaporization zone

I'm always curious -- with an engine in this thrust class, how close could you physically be, sustained, without dying? What about without injury?

Once you’re in orbit, you’re halfway to anywhere. Earth’s gravity well gives us a delightful atmosphere that supplies us with delicious oxygen and protects us from all manner of outer-space harm and makes sunsets pretty, but both the gravity and that atmosphere make it just tremendously difficult to get into space. So the barrier to exploration is rather high. Space missions are a little like climbing Pike’s Peak: it’s not THAT hard, but if it you don’t have a way to make it to the foot of the trail, you’re certainly not making it to the top. But once you have low-cost access to LEO, everything else becomes much, much easier.

I’m surprised the catch didn’t foul the chute.

She said it was a confirmed catch. Presumably the tow arrangement is such that it's offscreen. I think there was an "awwww" when it went out of frame because it looked like they had missed the chute, but then there was a bunch of cheering.

That's a catch!

Well, the primary constraints are mass and volume; remove those, and you've got a lot of room to work. Especially because miniaturizing things costs more money too.

Head-down, back to windward, and very very gradually.

Yep! Go for it.

Impressive. And I thought I was coming in well with a single-stage Mun lander and return vehicle. I’m assuming you could shave that significantly lower by angling your Puff engines to reduce cosine losses, no?

I think that was a typo; @Beccab meant we wouldn’t have been able to put people onto it until the 2020s. There’s a bit of a pork problem inherent with Orion, but repeatedly changing the mission profile and requirements certainly didn’t help. Originally, Ares I was supposed to do double duty: sending a clean-sheet-design Crew Exploration Vehicle to the ISS periodically and setting the CEV up for lunar sorties with Altair on Ares V. But of course Ares I was a terrible idea and never had a workable upper stage, and building a CEV (which became Orion) for cislunar operations was overkill for the ISS. If we had transitioned to an immediately-flyable Shuttle-derived architecture like Shuttle-C or Jupiter-DIRECT, without immediately worrying about rating the clean-sheet crew vehicle for cislunar operations, we could have had an Orion Lite flying to the ISS shortly after the last flight of the Shuttle. And then we could have focused on upgrading Orion Lite to allow cislunar operations rather than pushing out development endlessly. By now Orion would be a mature crew vehicle and we could have upgraded the service module to make it actually useful BLEO, and we could have a workable deep space crew lander based on the Orion pressure vessel and ECLSS. A service module large enough to take Orion from TLI to LLO and back to earth interface would be approximately the right size to take an Orion-based lander capsule from the lunar surface to LLO. Instead we have a 23-billion-dollar monstrosity sitting on the launch pad, that can’t even execute a proper wet dress rehearsal, without a functioning capsule, with the only “Shuttle-Derived” elements being the rebuilt engines that cost more than brand new ones.

I would hope that in an alternate universe where we didn't spend decades and a zillion bucks on trying to make pork fly, we would have managed to get Orion working by now.

Yeah, Direct was cool. The problem with a "Jupiter-120" configuration, with just two RS-25s on the core, is that T/W ratio at booster is a measly 66.7%, which is obviously unacceptable. However, if you simply detank the core to around two thirds of its propellant load, then a DIRECT with just two RS-25s and the old four-segment boosters could send Orion to the ISS with 18 tonnes of comanifested payload. That surely would have been cheaper (and faster to fly) than all of the nonsense NASA has been working on since 2005. They would have been able to keep the pork flowing and keep flying from American soil this entire time with a progressively-evolving launch architecture based on the same core: Jupiter-120d (4-segment boosters, 2 RS-25s, partially-detanked): Orion+18 tonnes to ISS, Orion+6 tonnes to Hubble Jupiter-130 (4-segment boosters, 3 RS-25s): Orion+25 tonnes to ISS or 65 tonnes to LEO. Jupiter-231 (4-segment boosters, 3 RS-25s, DCSS): Orion to TLI free-return Jupiter-246d (4-segment boosters, 4 RS-25s, 6 RL10B-2s, partially detanked upper stage): Orion + 57 tonnes to LEO Jupiter-246 (4-segment boosters, 4 RS-25s, 6 RL10B-2s): 100 tonnes propellant to LEO

I daresay the segmented SRBs are more sacrosanct than the core configuration. The pork must flow, after all. I wonder if a core based on the original SLWT with just two RS-25s would have been able to reach orbit. Probably not; if so, DIRECT-3.0 presumably would have suggested it as an intermediate step. It’s just a shame that we wasted so much time and money on Ares I and Ares V when we could have kept servicing the ISS and Hubble using Shuttle-C or Jupiter-130.

What you should do is score based on the distance covered by each successive VTOL, but add a multiplier for each successive stage. So if you have a three-stage nested VTOL, then the first stage score is the distance covered by that stage, and then the second stage score is 2*distance covered by that stage, and the third stage score is 3*distance covered by that stage. Even that might not reward successive stages enough, so you could do 1x, 2x, 4x, 8x, 16x... so that each successive stage receives a boost which is the square of the boost of the preceding stage. Do the VTOLs need to be able to re-nest inside their parent vehicle, or can they decouple permanently? Assuming a re-nesting capability requirement, I've got a single-Kerballed contra-prop-based VTOL aircraft (burning biprop with fuel cells for electricity) that pulls 58.3 m/s in surface velocity with 5324 seconds of flight time, or a range of 310 km. I think I might be able to increase speed in level flight by giving it wings, but I haven't been able to make it perform well yet, and I fear it would make it too bulky to fit in a Matryosha system. It fits inside the 1.25-meter structural tube (with a hinge-based lift) of an accursed torpedo-shaped VTOL plane with Juno-based tiltwings that can pull at least 127 m/s in forward flight with a flight time of 2560 seconds (although I'm sure I could increase it by adding more LF; it has a generous liftoff T/W ratio of 1.11) for a range of 325 km. Depending on how the scoring is set up, I might benefit from adding a Wheesley or Panther engine to the back end to increase horizontal flight speed. The "torpedo" fits snugly (with re-nesting capability) inside a Mk3 cargo bay, although I haven't yet built a VTOL plane around that. I might be able to make it small enough to fit inside a 5-meter fairing but that's a tall order.

It should be noted that Apollo 15-17 sent just under 49 tonnes to TLI. Orion is of course annoyingly heavy, but it does have the ability to return from low lunar orbit on its own, provided that the lander brakes it into lunar orbit a la Altair/Constellation. With 51.5 tonnes of throw and Orion's injected mass of 26.5 tonnes, that's 25 tonnes of margin for a lander. With a low-boiloff, well-insulated hydrolox landing stage based on the BE-3U, BE-7, or RL-10, that's something in the neighborhood of 9.4 tonnes of braking propellant from TLI into LLO. The lander/ascender budget then becomes 15.6 tonnes, which gets you 10.3 tonnes landed on the lunar surface. Total hydrolox use is 14.7 tonnes, 13% less than the propellant load of a 4-meter DCSS. The 4-meter DCSS is 2.48 tonnes dry, so if we allow 2.5 tonnes for the dry mass of the landing stage (1.96 tonnes tank mass but tacking on 540 kg to account for boiloff, maneuvers, landing legs, and extra engines), then that leaves us with a payload and ascent module budget of 7.8 tonnes, 66% greater than the Lunar Module ascent stage. Thus. building a new common bulkhead and adding four Raptors (or Be-4s) on a drop skirt to the existing SLS saves two RS-25s per flight and converts Block 1B into a single-stack moon rocket a la Apollo. SpaceX has dozens of deprecated Raptor 1 engines laying around at this point; I'm sure Elon would let them go for cheap. Surface sorties can be augmented by surface assets emplaced through commercial heavy-lift. That's if NASA remains stubbornly insistent on flying segmented SRBs, SSMEs, and Orion.

I did some more math on this, and it looks like one problem would be the gee-loading right before the skirt is dropped. In order to get a core T/W ratio of at least 0.8 at skirt separation, you'd need to run the F-1Bs for 137 seconds. But even with the RS-25s at minimum throttle, that's 3.3 gees just before the skirt separates, which is going to increase the weight of the upper adapter. But perhaps the F-1Bs could downthrottle enough to deal with this. The other problem is that the F-1Bs are just too powerful. The skirt thrust structure would end up weighing a LOT...which is mitigated since you drop it, but it cuts into payload. Using a SLWT-sized core with appropriate upper adapter, lower adapter, EUS, and five-segment boosters, that's 31 tonnes to TLI, which is lower than Block 1B. Of course you get away with a smaller core. A modern evolution path (we'll call it Block 1C) would be to use either BE-4s or Raptors on the skirt of the existing SLS. NASA would have add another bulkhead to store liquid methane, strengthen the upper core adapter by around 12% (to allow for the greater payload capacity of this version), replace the lower thrust adapter with one approximately half as heavy (for the two sustainer engines) and add a skirt for the methane engines. With four Raptors and a skirt burn time of 375 seconds, it would send 51.5 tonnes to TLI using five-segment boosters and EUS, which is dramatically better than Block 1B or Block 2. Adding more Raptors and lowering the burn time can help a little, but not much, because the weight of the skirt thrust structure starts ramping up again.

Back of the envelope math would suggest you’d need a pair of RS-25s mounted centrally and a pair of F-1Bs. That would more than double the thrust of the core, from 9.1 MN to 20.5 MN. Of course, the core’s wet mass would be higher given the RP-1 that would be replacing LH2, but not that much higher. With EUS, likely enough to outperform Ares V; with a proper EDS, significantly more. The F-1B is DOA unfortunately, but a modern version with six BE-4s or four Raptors on the skirt would work almost as well.