RCgothic

Simulations, comprehensive engine test fire campaigns, integrated whole vehicle static fires, vastly superior flight computers and instrumentation, a flight test program that frankly doesn't care too much if the vehicle survives, and a vehicle that actually returns flown flight articles intact for inspection. There's nothing of any substance in common with the N1 program. It's a very silly criticism.

TOS season 3 is widely regarded as terrible. Neither the social philosophy nor the quality of writing has meaningfully changed.

Star Trek has never not been highly allegorical.

Fast breeder reactors are pretty awesome. They can use lower enriched fuel, and then create more fuel from fertile blankets. They're also a pretty good way of using the "spent" fuel produced by regular reactors. Every time someone suggests we bury used fuel I cry inside - it's going to be such a valuable future resource. A number of issues though: 1) They're more expensive than regular reactors. Molten salt cooling loops aren't cheap, and can never be allowed to cool down. Maintenance can be challenging, and sodium reacts violently with water. Water is a basically ideal medium for driving turbines, but a sodium-water heat exchanger would be... Interesting. So I believe they need another intermediate loop as well. 2) Uranium and enrichment of it got cheaper, which took away their advantage. 3) Reprocessing used fuel gets much more economic after a couple hundred years after the initial fission products have decayed off. It's a young industry and we're not there yet. 4) They produce a lot of plutonium, which is easier to purify to weapons-grade than uranium because it only involves chemically separating elements rather than physically separating isotopes of the same element. That's a proliferation risk. 5) Managing a closed loop fuel cycle is more involved. You need to be producing enough fuel to reprocess and then making sure that gets delivered back to a plant in a timely manner. There's more opportunity for that loop to break down, and MOX fuel is more challenging to handle due to the presence of residual fission products. Compared to importing fresh uranium which is handleable by hand, and then just storing what's produced, it's a lot more challenging to make that all work nicely. I do think FBRs will pick up in popularity in future, much more likely than Fusion ever taking off IMO. Economical maintenance/handling for fusion plants is such a difficult challenge, even more so than maintaining the plasma and extracting usable energy.

I believe the theoretical maximum ISP for nuclear pulse propulsion is around 100000s. The largest weapon ever detonated was 27 metric tonnes. Applying that in highly ideal and theoretically generous circumstances assuming a perfectly designed device to the 4.9 million metric tonnes of the Enterprise D and assuming the shields don't provide any mitigation, would kick it to about 5m/s. The bridge crew would certainly feel that, but I think worse impacts have been delivered on screen. There's no point getting into theoretical yields of antimatter torpedoes, they appear to be used mostly for miniaturisation of the warhead rather than increased yield. The torpedos that tore through the Reliant and Enterprise A clearly weren't megaton range.

The Enterprise D canonically weighs 4.9 million metric tonnes. An Imperial Star Destroyer is 40 million tonnes. They're going to be hard to shift, even before accounting for nuclear devices being very very inefficient at turning their energy into momentum.

If I were to take a few guesses at Raptor's particularly large shutdown plume, I'd say: 1) A particularly high chamber pressure leads to particularly high flow rates as the gas is purged, which leads to the flame reaching further from the engine. Raptor operates at about 70% more chamber pressure than the next highest American engine, the RS-25. 2) Related to 1), but it's an extraordinarily powerful engine for its size, processing a very large quantity of fuel. It's got a lot to purge and takes a while to spool down. This would all lead to more fuel being purged and a bigger effect. 3) As a full flow combustion engine, the purge is generally from the main nozzle, whereas a gas gen might split some off a vent. This might be relevant to comparisons between static fires with a zoom on the main nozzle vs full-vehicle shots. 4) Fuel-rich Methane burns a lot more brightly than hydrogen does. 5) Retropropulsion tends to exaggerate the effects as in a static fire or launch it's just exhaust buoyancy driving the flame up a vehicle, instead of high velocity air-stream. 6) Tank venting and vehicle safing also add substantially to the mass of fuel being burnt at engine shutdown. The only other vehicle we regularly see do this is Falcon 9, and I'm guessing residual supercooled liquid RP1 is fairly safe to leave in the tanks (pressurised with helium) compared to superheated methane autogenous ullage gas.

Yeah, there was plenty of discussion of it up-thread, the post I quoted was @tater getting the first mention in.

The hinge fire is news to nobody in this thread who actually reads it instead of doing nothing but post pet theories. Also nice use of a diagram of SN8. The 3rd hinge on SN33 is comfortably above the false ceiling, exactly where we'd expect to see a plumbing leak.

The plumbing. New downcomers in that section. Engines no significant changes.

Thinking about the "don't bother with reuse, just send it expendable because that works" argument just now and realised that something similar is causing me a significant amount of personal frustration at work right now. There's a major intermittent process I'm responsible for designing, and the traditional way of doing things will cost £190-240M GBP (in 2025 terms) over plant life. Spending perhaps a twentieth of that up-front to implement existing tech would allow us to cut that cost by a third (potentially saving £60M GBP in 2025 terms), employ fewer people, generate less hazardous waste, and provide a safer environment for workers. But because it's "only saving a few weeks" when the process actually rolls round every 5 years or so there's a traditionalist block that is being stubbornly obstructionist, and having lost the technical argument, is now using the argument of development time and submission deadlines to try kill the innovation through "process". I.e: "the way we've always done it works, don't bother." SpaceX could abandon their innovation and take the easy way. They've got a 5-10 year tech advantage over their nearest competitors. But they won't keep that lead by abandoning innovation. Full rapid reuse is the holy grail of spaceflight for a reason. Got very limited sympathies for the alternative arguments right now.

Scott Manley thinks the explosion was FTC activation 2-3 minutes after loss of telemetry, on automated detection of deviation from flight corridor. He thinks the FTC was uncalled for in this instance, and only had the effect of spreading the debris over a larger area. Luckily the ship was entering the atmosphere at the time. If FTC detonation had occured in space on an upward trajectory the debris field could have been extremely large. Potentially Starship could have attempted to glide to a pre-programmed safe splashdown, (varying depending on flight stage) although this may not have been possible with a loss of attitude control. All this counter-balanced against the risk of a large un-FTC'd chunk surviving an uncontrolled re-entry.

Where is the ship going to come down I guess is now the question.

They'll have had data up until loss of vehicle, possibly a few moments after IMO. Raptor pi survived a second flight though!

https://bsky.app/profile/sciguyspace.bsky.social/post/3ldjuvm6r6j2c FAA approve IFT-7

It's a sensible idea. Movements of large quantities of propellant are risky, and the ability to stand the crewed module off at a safe distance might be a useful safety feature. They undock and return dragons to the ISS with crew on with moderate frequency, this would be similar.

I think expendable Superheavy is just a case of making SpaceX an offer, plus a bit of time. How much time? Probably not more than any other option.

16 SLS block 2 missions? Plus commercial refilling in cislunar space? (Talking what, 50+ additional flights?) File that under never going to happen. If SLS even gets to 4 flights and block II it will have beaten the odds at this point. It's amazing how 2040 for a crewed landing can be both totally unrealistic and completely devoid of ambition at the same time.

The apollo programme as a whole may have been expensive due to the amortization of the extensive R&D and construction of infrastructure from the ground up, but the marginal cost of Apollo applications missions would have been less than what shuttle ultimately cost and we'd have got a lot more done with 70+t to LEO capability than shuttle managed. The only unique thing I think shuttle truly accomplished was Hubble servicing. But for the savings we could have built another.

You can get a "skip" re-entry without aerodynamic lift on a ballistic trajectory. Just put your track high enough that you'll pass periapsis before scrubbing enough velocity and altitude will start to rise again. When Apollo commentaries talk about missing the entry corridor and skipping off into space, this is what they mean. The capsule will definitely be coming back to Earth in a later pass, just at a time that's potentially beyond the endurance of the capsule and/or at a very non-conducive-to-safe-landing location. Aerodynamic lift allows better control over the trajectory. It might be desirable to keep the path higher in the atmosphere than a pure ballistic territory would allow, e.g. if the heat shield can endure moderate heating indefinitely and your craft has features that don't enjoy g-forces and high drag, such as wings or fins, then it makes sense to scrub off as much velocity high up as possible. But if the heat shield is ablative, a long re-entry can wear it away. So to keep the total heat absorbed low it might be desirable to come in steeper than ballistics would allow. This would have higher peak temperatures and g-forces, but would ablate less material. Another reason to use aerodynamics during re-entry is if the apoapsis is high or interplanetary, there's a lot of velocity to scrub off. A craft might not be able to endure a low enough periapsis to scrub off enough velocity in one pass ballistically. Using aerodynamics can hold the craft down at a survivable periapsis long enough to scrub velocity instead of skipping off. The heat-shield on the Orion capsule was apparently designed for an initial phase of heating, a skip to a higher altitude for a period of cooling, then a final re-entry. It sounds like that design had some flaws when gasses generated by the first phase of heating built up in the heat shield during the cooling phase, and the build up of excess of pressure of those gas pockets popped large chunks off the shield.

I'm cautiously optimistic about Isaacman as administrator. I think he'll be unsentimental about cutting elements that need to be cut and driving forward progress towards a greater goal. I don't think he'll be able to command Polaris missions whilst NASA administrator however.

I don't expect Isaacman to be sentimental about SLS when he takes charge of NASA.

Quite a nice fireball on splashdown. Nominal insertion for Starship though. Relight test in approx 25mins. Not yet that I've heard.

No-go for catch. Aiming for splashdown.

Liftoff! Max-Q!