sevenperforce

Wait, did this actually happen? Sounds like a good story. Now I'm googlin'... Yep, this was PAS-22, launched in 1997. It was launched on Proton but the final Block-DM stage failed, which left it in a useless orbit. The satellite didn't have enough propellant to correct its orbit, but after the insurance companies declared it a total loss a subsequent team figured out how to do repeated Oberth apogee-raising maneuvers to reach a lunar flyby. They ended up doing two different lunar flybys to correct both inclination and perigee -- essentially using lunar gravity as the "burn" of a bi-elliptic transfer -- and then used onboard propellant to lower the apogee to geostationary orbit: The maneuvers burned through a lot of the onboard propellant, which cut the operable lifespan of the satellite in half, but that was much better than losing the satellite entirely. This is a good illustration of another value in bi-elliptic transfers: inclination corrections. It is MUCH more inexpensive to change inclination at apogee than at perigee, and the higher the apogee the better. Most GTO launches today actually place the comsat's apogee well above geostationary altitudes so that the satellite will expend less onboard propellant to correct inclination and raise perigee.

I’m guessing one of two possibilities on the first stage rapid unscheduled disassembly. The obvious is that hot staging is a nasty affair and the upper bulkhead simply couldn’t take the heat. That would make sense. Another possibility is that the slosh during that very energetic booster flip was significantly more chaotic than expected and they had engine starvation problems. The graphic depicting which engines were firing may have supported this, as most of the engines on one side lit successfully, while the ones on the other side did not. The apparent loss of the second stage is much more mysterious and doesn’t seem to have any immediate explanation. I think someone up thread mentioned a possible, autogenous pressurization failure, and that seems like a reasonable possibility, especially if damage sustained during hot staging punctured the tanks somewhere and caused a slow leak that auto press simply couldn’t overcome at the end of the burn when the tanks were mostly empty. Regardless, good job and congrats to everyone.

You should be able to watch it off-X here.

Now you've got me wondering whether the emissivity of the heat shield tiles comes into play, assuming we are using a reusable tanker Starship. Obviously they are not good at conducting heat, which makes them less useful...but they have VERY good emissivity, so that's something to consider. Also wondering if pointing Starship engines-first at the sun makes any difference. I could see a stretched depot Starship with a disposable fairing that covers a deployable heat shade, too; that's a possibility. Methane is not a super great coolant by any means but it's better than some things. They could go in a direction similar to ACES and use gaseous boiloff from both tanks to operate a small internal combustion engine that pumps methane gas into a radiator, compresses it, and then recycles it back in to make a Carnot heat engine. It's been a while since I took thermodynamics so I am not sure about the physics of using a larger mass of coolant to make up for poorer coolant properties and lower power. Here we go!

There shouldn't be significant boil-off due to atmospheric heating; we are talking about huge volumes of propellant in a reasonably well-insulated tube with low surface-area-to-volume ratios. And atmospheric heating during ascent is really not terribly significant...dynamic pressure peaks early and even that doesn't come with significant heating. Maybe they are talking about the amount of propellant that will have to reach orbit to enable a full-loop mission with refueling in elliptical orbit, or something. Or maybe boil off in space is much worse than previously thought. That's the unsettling possibility.

No current market for bulk raw materials in space, really.

Yikes. I don't like the way that sounds.

Yeah, Vulcan is in the vein of Atlas V, and Atlas V really was optimized for high-energy missions, and high-energy missions really make upper stage reuse challenging. Just look at Starship -- it can deliver 100-150 tonnes to LEO but I believe it is only slightly better than FH for GTO. I'm not sure that it can even do GEO missions at all. If Starship is successful then I could see the growth of transporter ferry spacecraft that pick up individual comsats from LEO, take them to GEO, then aerobrake back down to LEO to refuel and repeat.

Not too much technical data but there are a few interesting things. Spoilered to make for easier viewing.

Elon says it's a grid fin actuator. Trying again on Saturday.

Thanks! I hit him with a couple of technical questions.

Ah, good catch. That might well be the gimbal mount, and the mounting brackets on the sides of the engine bell could simply be for the gimbal actuators. That exaggerated lip between the nozzle and nozzle extension is kind of weird, though. This is ORSC so I'm not sure why there would be any boundary; it's not like they need an exhaust injection manifold a la F-1 or MVac. Maybe that's part of the regenerative cooling manifold and they're cooling part of the system with LOX and part of the system with CH4? If I was putting hot oxygen anywhere I would put it as far down the nozzle as possible so that there wouldn't be as much corrosion or risk of failure at burn-through. Now you've also got me wanting to speculate about what kind of ORSC they're doing, whether they are doing a single-shaft turbine with a helium purge or some other design, whether they have boost pumps, and so forth. It would be cool to do, say, an expander-cycle boost pump. There's not any visible detail on that image. I wonder if they are going to try test firing it from pressurized tanks without the preburner? Is the Centaur on Atlas V the same regardless of position (under or not under the fairing)? The fair it when the loads are too high (more SRBs), so it's clearly load driven at some level. Neutron doesn't face that issue. It might be possible to make an even lighter Centaur for lower mass payloads with high C3 (if said Centaur was faired)—but this being "old space" probably not worth the effort. Centaur uses the same tanks whether or not they use the fairing. And the fairing isn't just for bigger loads; the Atlas V 501 (5-meter fairing, no SRBs) has been launched a total of seven times. It does like like the 4-meter fairing has never been launched with more than three SRBs, though, so maybe that's where the aero loads get dicey for Centaur. But the comparison is really something. Centaur has a dry mass of 2,316 kg, which less the 190-kg RL10C-1 comes to 2,126 kg. That, for an external cylindrical volume of 77.15 cubic meters and a total prop load of 20.83 tonnes. Pixel counting is always rough, of course, but based on a 5-meter outer diameter for the Neutron second stage I'm estimating an external cylindrical volume of 119 cubic meters. Even if the more rotund design means lower volumetric utilization -- let's say around 105 cubic meters -- that's 36% more propellant volume than Centaur and 3.02 times more propellant mass given the higher bulk density of methalox over hydrolox. Looking at 63 tonnes of propellant for a 300-400 kg tank is just utterly shocking...that's, like, a propellant mass fraction a little over 99%. Trying to sanity check this. Assuming typical T/W ratio on the order of 150 for the 890 kN vacuum version, I would expect the weight of a single vacuum-optimized Archimedes engine to be around 600 kg, which still leaves us with a 98.4% stage propellant fraction. They advertise 13 tonnes to LEO and 1.5 tonnes to either Mars or Venus. You need about 3.9 km/s to get a transfer orbit to Venus out of LEO which is lower than typical transfer orbit requirements for Mars so let's go with that. Back-calculating with the expected 365 seconds of specific impulse gives us 6.1 km/s of Δv on the ascent stage with a 13-tonne payload, meaning that the first stage has very little work to do other than getting out of the atmosphere. Back-calculating for a 1.5-tonne payload gives us 11.6 km/s of Δv, which is 5.5 km/s of extra: higher than needed for the Venus transfer, but not entirely out of the ballpark. And we're working with dicey numbers here anyway because we don't really know what a Mars or Venus transfer looks like, or whether that's even reusable.

I'm trying to get my kids' elementary school to stream the launch, but Twitter is blocked by their server. Is it going to be anywhere on YouTube or anywhere else?

Yeah that's truly incredible. If they can really get a 5-meter methalox tank in under 400ish kg then...just wow.

Oh, I see your point -- adjusting to where the booster is, not trying to push the booster to the center. Yeah, that's workable.

Yeah, same. The RTLS landing of the last F9 was waaaay off-bullseye when it came down. I know that before they were talking about giving Superheavy those ten-tonne gas-gas methox thrusters for translation during hoverslam and that seemed like a workable plan but AFAIK they have scrapped the thrusters entirely. Yeah, but I don't think the chopsticks are capable of, like, "pinching" the booster into place. And catching Starship with the chopsticks seems like a REALLY long pole.

you are actually incorrect in that statement. N2O4 is just NO2 in liquid form. considering its NO2's melting point is above stp conditions, when removed from a cryogenic thermos or not actively being cooled, it will boil off into NO2 gas. Holy necro batman! But anyway this is sort of true. N2O4 is a different molecule than NO2; it's a dimer of NO2, two -NO2 groups bonded together. But the N-N covalent bond in N2O4 is a very weak bond because the paired oxygen atoms on either side of the dumbbell are holding onto the electron shells tightly, so you only need a small temperature transition to break or form the bond. Red fuming nitric acid, a mix of nitric acid, N2O4, and water, has a lower freezing point than pure N2O4 (as noted above four years ago by @IncongruousGoat) which is great. But it will continue to "fume" toxic NO2 continuously, whereas pure N2O4 will produce very little NO2 gas as long as it is kept below ~12°F. So you can load the propellant tanks at low temperature, tamping down fume production, and then you're good as long as you aren't trying to launch at significantly lower temperatures where N2O4 will freeze.

The top of the engine looks like the SM-6A Service Module from the Making History DLC: Maybe they plan on putting the turbopumps on those attachment nodes? /s In more serious review, it looks like there are gimbal mounting points on the nozzle extension and the nozzle extension seam is fluted, so this could be a true throat-gimbaled engine! Those are fairly rare. I don't think those bits up top are a gimbal, although they might be.

I wonder what capture/collection system you'd actually want to use for that. Titanium's melting point is around 3000°F which is lower than typical cislunar-return re-entry heating, but let's suppose that the lunar manufacturing was such that ablative losses were negligible. What would the ideal collection system look like? Shoot the titanium slag on a trajectory such that it lands in specified desert target zones, then come in after the fact with a bulldozer and scoop up all the sand on the surface and filter out the chunks of metal?

Really fascinating stuff:

Yeah, that's what it looks like. Hence "allegedly". Apparently Willis has gotten good intel previously. Comparing the two images, it is obvious that they are from the same heritage, but if it is a photoshop of the original then it is a VERY good photoshop.

New HLS renders, allegedly (they look pretty legit as these things go). From David Willis on Twitter.

I don’t believe so, certainly not with Skylab and pretty sure on the ISS. Wasn’t much need, since they all had crew tunnels, and seems very high risk. Just looked it up -- there were plenty of spacewalks to assemble ISS, but the first that would have allowed an EVA between vehicles was STS-104 when the Quest airlock was actually installed. Although there were three spacewalks during this mission, two from the Atlantis airlock and one from the Quest airlock, nobody ever left one airlock and entered through another. Maybe it has never happened! Apollo 15 required an EVA to retrieve a recording device from the Apollo service module, but this was after the lunar module had been detached. For Skylab 2 (the first crewed mission to Skylab) the crew had to EVA, climb onto Skylab, and manually disassemble part of the Skylab docking ring in order to get the ring to function for hard capture, so this was at least a transfer between vehicles, even if they didn't enter Skylab via EVA. But yeah, more interesting to see instances where EVA transfer was planned and integral, like in the N1 lunar lander. No, I'm talking about the 1L/Vostok-7 spacecraft (not to be confused with the cancelled Vostok-7 mission, the Vostok-7 I refer to is of the same category of designations as the Vostok-3KA, the official name of the original Vostok). Wow, cool! I love how I'm continually learning new stuff here. Very Kerbal. But that begs the question, why not just launch in the 1L? Not the first time the Soviets launched with no abort ability… They may have had no concerns about launch abort, but the mission profile called for sequential crew-guided assembly of the propulsion modules with the circumlunar crew vehicle attached last: The IL vehicle was added last, so a separate crew vehicle was required.

Wait Vostok-derived lunar flyby?? Probably talking about the early Soyuz-derived lunar flyby using the Soyuz-A-B-V design, where two crewed Soyuz capsules would go up to meet a Soyuz-based tug that would have already been refueled by several subsequent R-7 missions. The two capsules would have had some EVA transfers while assembling the whole circumlunar stack. I'm guessing @SunlitZelkova means EVA transfer for a lunar mission architecture. Weren't there at least some EVA transfers during Skylab and during the construction of the ISS? There was an EVA transfer proposed (in hindsight) as a rescue mission for Columbia, but obviously that wasn't operational.

I think there's likely a top port for fuel transfer, then the side port for crew transfer See, the trick is that they don their spacesuits and swim through the liquid hydrogen. They needed the spacesuits anyway! The best part is no part! Brilliant! If they had a four-engine cluster at the center instead of a five-engine cluster, they could do "sweep" the surface on touchdown by vectoring two engines inward and two engines outward, then reversing. I suppose they could do the same thing with the five-engine cluster since the central engine is going to be doing the work of dusting off the center anyway. Still, it does make a true surface-level egress impossible because you need vertical space for the engines (just less vertical space than a single engine of comparable thrust).