sevenperforce

Crazy that the spacecraft has been cruising toward its destination for 9 months and its target is only now coming into view. The white spot is Didymos, the primary asteroid. The camera has now picked up Dimorphos, the target moon, but it's too dim to be seen for us.

Felt like it came down much farther from the bulls-eye than I'm used to seeing.

Rocket launches are one of the few places where advertising budgets pale. If you’re charging $70-200 MILLION for a single launch, the amount of money an advertiser can pony up is negligible.

Looks like this launch was prime viewing for the entire eastern seaboard. I have a friend in NC who saw the first-stage re-entry burn as well as the upper stage pass.

Was not expecting to see this tonight but the trajectory of the Starlink launch brought it right over the horizon at sunset. Really cool to see with my kids.

Here's a good place to start: https://en.wikipedia.org/wiki/Comparison_of_orbital_rocket_engines I'm not sure what you mean by "most use[d]" but there are a few possibilities: The oldest orbital-class rocket engines still in use AJ10 (first flight in 1958, still flying today on the Orion spacecraft) NK-33 (designed in the late 1960s, still flying today on the Soyuz-2-1v) RD-107/8 (designed in 1957, still flying today on the Soyuz family) RD-0110 (first flight in 1960, still flying today on the Soyuz family) RD-253 (first flight in 1965, still flying today on Proton) RL10 (first flight in 1962, still flying today on Atlas V, Delta IV, SLS, and Vulcan) The engines that have launched the most total vehicles to orbit through history RL10 (used on Atlas, Saturn I, Titan III, Atlas G, Titan IV, Atlas II, Atlas III, Atlas V, DC-X, and Delta IV) RD-107/8 and RD-0110 (up to 1900 launches in the Soyuz family) Merlin 1D (used on all Falcon 9 launches since 2013) The engine that currently launches the most payload to orbit each year Merlin 1D (Falcon 9 launches have made up approximately half of all mass to orbit so far this year)

Overall attitude, perhaps, but at least this is vastly safer because no one is on board.

If you are low enough in the thermosphere that drag is at all meaningful, then the random buffeting of particles it experiences will average out to cause it to orient with the heavy end forward (i.e., in the direction of travel). At the same time, the tidal gradient of Earth's gravity well is going to try to pull the heavy end to point toward Earth. Gravity is stronger the closer you get to Earth, and so the "stable" position is to have the heavy end deeper in the gravitational field. These two sets of perturbations will induce a rotation. In the absence of force, angular momentum is preserved, and so the bowling pin will eventually settle into a rotation equal to its orbital period: It may be weird to think about the bowling pin rotating as it orbits, but it will, just like a moon. Angular momentum is conserved even if something is small. The ISS, for example, always keeps the same orientation with respect to the Earth because it rotates every 90 minutes, the same as its orbital period. The amount of time that it takes to settle into a stable rotation, and the angle at which it will eventually settle, will ultimately depend on the sizes of those perturbing forces I noted above. At a very low altitude, where both thermospheric drag and tidal forces are higher, this will be faster and the angle will be more bent back. At very high altitudes it will take longer.

For anyone who might find it useful, I went ahead and did a pixel count with known values (total vehicle height and second stage height) to estimate the dimensions of everything in Neutron so far: Interesting that the "5 meter diameter" fairing appears to be the true internal envelope diameter (as this is the diameter of the upper stage) rather than a measurement of the outside of the fairing, which is notably larger. The 7 meter diameter does not include the landing legs. I'm sure someone can drum up tank volumes from this.

It's fun and dancy and full of joy, as JLo would say.

This is clearly just preliminary concept art, but I spy four reasonably large engine bells peeking out from what appears to be the service module. Given that there is no apparent intention to make the upper stage reusable, it might make sense to give the service module a ring of simple, high-thrust, low-efficiency methalox engines (preferably ignited with a solid pyro) plumbed through the PAF to the upper stage itself. Then, in a low-altitude abort, those engines would drain the upper stage in a matter of moments, pulling it and the capsule free of the booster: This would eliminate the need for carrying the abort propellant on the service module like Starliner (which means less total mass to orbit), and also avoids plumbing the capsule itself with the same propellant used for abort like Crew Dragon. The abort motors would be pretty thoroughly oversized but they'd certainly have no lack of propellant.

Interesting...from this article, it's stated that the very hefty first stage will use methalox, not hydrolox: https://universemagazine.com/en/aerospace-startup-tests-reusable-rocket-engines/ Not particularly well-written so I don't know how much I trust it, but it might have been something discussed in one of the presentations that I missed. I'm still pining for that fully-reusable sustainer-architecture TSTO of lore, though. I suppose that once they have it flying as a proper TSTO, they could start experimenting with making the upper stage an SSTO using hydrogen drop tanks like the ROMBUS concept. Or, you know, make the drop tanks crossfed side boosters that use the interface with the side of the main ship as an intake ramp for air-augmentation. . . .

I'm eternally sad that they jettisoned the drop tank plan (pun intended). It always seemed like an electric-pump-fed methalox lander with solar-rechargeable batteries and drop tanks was a really clean solution.

I know this is kinda off topic, but while you remember right about the dual turbines, each also had their own separate preburner: Oh, dang, that's even worse than I remembered. You'd think that with completely separate preburners, they would have worked on varying the mixture ratios to optimize thrust and Isp since the pumps are completely independent, but evidently the RS-25 maintains a single mixture ratio at all times. Weird. And technically the RS-25 is both a FRSC engine *and* a closed expander cycle engine, since the fuel is pumped around the chamber and engine bell to cool it, then that supercritical fuel expands through a low-pressure turbopump to step up the propellant pressure before it enters the main turbopump: Because the RS-25 uses a fuel-rich preburner to operate the oxidizer turbopump, it had to have a separate helium tank to provide a constant flow of helium to continually purge the cavity between the fuel and the oxidizer. The only thing that doesn't need the constant helium purge would be a proper FFSC engine like Raptor. The engine I was thinking of was not actually the RS-25, but the RS-68. It has a single burner (although it's a gas generator, not a preburner) that exhausts into separate turbines which run the pumps independently: The two gas generator exhausts also provide single-axis roll control. The Chinese YF-77, which is essentially a clone of the RS-68 (except that it uses active dump cooling on the nozzle instead of ablative cooling like the RS-68) does the same thing, with a single gas generator and two separate turbines with two separate exhausts. They fly the YF-77 in pairs on the Long March 5 core, though, so I don't know whether they use the nozzles for roll control at all. As always, I highly recommend reading this amazing blog post about the many possible complexities of just one type of engine cycle. The engines on Neutron's first stage will always keep the center of gravity extremely low, just like with Falcon 9's first stage. Opening the fairings would definitely pull the center of lift/drag further back, but that's not going to be a major issue since the center of gravity will already be low enough. I was just thinking in terms of additional drag.

Illustrating again why "start with the coldest possible substance" is not a useful exercise in active cooling. You need the same amount of delta-v. You need more thrust. . . . Well, to be pedantic: if you have a vehicle with just enough Δv to make orbit, and then you add mass to that vehicle for heat shielding, then that vehicle no longer has enough Δv to make orbit. So you need more Δv. And you might not need any more thrust at all; you might have wholly sufficient thrust already. There are any number of ways to get more Δv and "more thrust" or "more power" are not the whole.

I wonder what their flow rate is.

Brittle? As in easy to break? A metal can be either brittle or ductile. A more ductile material will be able to handle expansion and contraction without cracking, while a more brittle material will not. Put simply, you can make a very springy spring out of steel; you cannot make a very springy spring out of tungsten. Having a ductile construction material is important for a vehicle like Starship because the tanks will expand and contract as they go through temperature cycles. Tungsten is also very difficult to work because it is so brittle. It is very hard to bend it at all, but even if you can get it to bend, it will probably crack. Its melting temperature is so high that it is also extraordinarily difficult to weld, and in fact it must be welded in a pure argon atmosphere (or another inert gas) or other stuff will get into the weld and weaken it. Its high melting point means you can't even smelt it; you have to extract it and refine it chemically. Fine... coat a layer of tungsten over the steel. If you have a steel inner tank wall with something that will keep the steel cool, then you don't need the tungsten at all. To that point, though, there's something fundamental you need to understand about cooling. Suppose you have a back injury and you want to put an ice pack on your back (which we will assume normally has a surface temperature of 35°C). What will keep your back colder for longer: a pouch of water at 0°C, or a pouch of rubbing alcohol at -10°C? Assume that both pouches contain the same weight of coolant. You might think the rubbing alcohol would work better, because it's starting at a lower temperature. But you'd be wrong. The heat capacity of water is 74% higher than the heat capacity of rubbing alcohol, so by the time the alcohol temperature goes from -10°C to 35°C, the water will only have gone from 0°C to 25.8°C. That's because water is just better at absorbing heat than rubbing alcohol. Keeping something from overheating is not a function of how cold your coolant starts out, but rather a function of how fast your coolant can get rid of heat. If you want to use active cooling with liquid hydrogen or liquid helium or even water, that's perfectly fine. Just know that you'll have to carry that extra liquid hydrogen or liquid helium or liquid water into orbit. No, we don't. You don't need more power; you need more delta-v. And simply adding mass is one way to fix it but not the only way. You don't even need a bunch of mass. The design by Stoke uses an actively-cooled heat shield.

Tungsten has a cross-sectional ultimate tensile strength that is 90% greater than stainless steel. However, its density is 145% greater than stainless steel. So a tungsten tank with the equivalent strength of a steel tank will be around 30% heavier. It's also very brittle and becomes more brittle as it gets cold, which makes it VERY poor for holding cryogens. And before you suppose that a layer of tungsten will work: tungsten can handle re-entry heat just fine, but it will also transfer that heat to whatever it is touching, so you'll still need insulation between the tungsten and everything else.

Good idea. Unfortunately: Dreamchaser's heat shield isn't rated for high-energy returns from the moon Dreamchaser doesn't have enough propellant to enter or return from lunar orbit There aren't any upper stages with storable propellants that have enough dV to push Dreamchaser into TLI.

There was a time when we had the capability to keep an extra shuttle ready on the other pad for a rescue mission every time we launched. No reason we couldn’t have maintained both pads, transitioning one to Shuttle-C and one to DIRECT in order to ultimately set up for EOR lunar missions. Shuttle-C would have been able to put 71 tonnes into LEO. That, surely, is sufficient for an all-hypergol lunar lander including LOI braking propellant. Combined in LEO with Orion launched on Jupiter-246, with the JUS upper stage performing the TLI for the whole stack, you surely would have had enough performance for the whole mission.

Shuttle C at least keeps your pad running long enough to come up with a smooth transition to DIRECT.

That’s counter-intuitive, though, because a longer first stage burn (to enable the fairing drop and staging to be simultaneous) means a hotter re-entry, which you’d think would require a braking burn. Maybe if they leave the clamshell open for initial shuttlecock entry, like Stoke is planning, that will help. Well oxygen is denser so you can extract more torque in a smaller turbine. That’s probably the first reason. Using ORSC also gives you a higher overall O:F ratio which reduces both your tank volume and your propellant costs. Finally, while coking isn’t typically a problem with methane, ORSC is much better-studied and has a longer legacy, and it certainly obviates any possibility of coking from any impurities that end up in the CH4. IIRC, the RS-25’s FRSC cycle actually uses dual turbines running off a single fuel-rich preburner because trying to build a single-shaft FRSC engine is just too complicated.

It's also very interesting that they provided the expendable, reusable, and RTLS payloads specifically (15 tonnes, 13 tonnes, and 8 tonnes respectively). The difference between the downrange recovery and expended recovery is remarkably small. Definitely enough information that we can play around with it and maybe come up with some dry mass numbers.

So they're going with oxygen-rich staged combustion rather than the gas generator we had originally anticipated. Looking at 303 seconds of sea level specific impulse, 329 seconds of vacuum specific impulse for the sea level engines, and 367 seconds of specific impulse for the vacuum engine. The "not a capsule announcement" is about what I would have expected for not really having much of a plan yet. But it would be cool if they were thinking about making the service module integrated with the second stage. Very interesting that the staging structure is NOT what I had originally thought. I had imagined that the upper stage and the payload was all contained within the moveable fairing, but in actuality the upper stage is contained within the whole fixed upper half of the launch vehicle.

The Kerbal Diana program (hint: Diana is the Roman version of the Greek goddess Artemis) is plagued with cost overruns, schedule snafus, and recurring problems with legacy hardware. However, the Kerbal Space Center is confident that their KLS Megarocket will eventually be functional, and they're looking for commercial solutions to get crew and cargo down to the Munar surface from the Munar Gateway. For this project, the powers that be at the KSC are looking for two things: reusability and flexibility. They want the same autonomous vehicle to be able to deliver crew on one trip and cargo on the next trip, or vice versa. For cargo deliveries, like rovers or surface stations, the vehicle should drop the payload off on the surface of the Mun and return back to a space station; for crew deliveries, the vehicle needs to bring the crew back. You can do drop tanks or refilling, but obviously the lower mass required from Kerbin to the space station, the better. Show me what you've got!