sevenperforce

It looked like the second stage ignition started and then died off. Too bad.

So it looks like we were saying the same thing the whole time? I wish I could read Russian. It is admittedly hard to tell from the pictures whether the lever arms attach to the core, to the booster, or to the core-booster interface itself. I suppose the third option would be ideal from a force management perspective. The separation mode for the Soyuz boosters is, frankly, awesome. They don't use solid rockets for the separation which creates the Korolev cross. Instead they simply vent the pressurant from the LOX tank. Such a good design. You can replicate that in KSP by using one of the little fuel vents, linking it to an action group, and keeping just a touch more oxidizer in your tank than liquid fuel so as to leave a little bit for the propulsive vent.

Dumb question, perhaps, but why does it have to cross feed at the engine? Why can’t you have tanks that run pressed feed lines to the other tanks?

Yes, I agree that the ring formed by the four arms is what holds up the whole affair. I'm saying that the load-bearing attachment at the tip of each ring appears to attach to the tip of each booster and not to the core itself. I could be wrong, of course, but that's my understanding of it.

Since we haven't been hating on SLS enough lately.... I was racking my brain to come up with a way to actually make use of the RS-25's abilities. What if you put two RS-25s on a narrower, shorter SLS core and then crossfed them from auxiliary tanks on top of kerolox (or even solid) boosters? You'd get the benefit of the high specific impulse all the way from sea level to orbit but you wouldn't be dragging that heavy empty core almost all the way to orbit.

That's not my understanding. From Wikipedia: "The entire rocket is suspended in the launch system by the load-bearing mechanisms on the strap-on boosters where they are attached to the central core. The latter rests on the nose sections of the strap-on boosters. This scheme resembles flight conditions when the strap-on boosters push the central core forward. The concept of suspending the rocket was one of the novelties introduced with the R-7/Soyuz. Since the launch pad has been eliminated, the bottom portion of the rocket is lowered." I believe the tulip arms connect to the boosters, not to the core.

The thing I abuse more than anything is using warp to stop undesired rotation......

It's much easier to build strong spherical pressure vessels than it is to build strong cylindrical pressure vessels. Rather than having to design a tank which will both hold internal pressure and withstand compressive longitudinal load, you split the jobs up. The N1's spherical tanks were lighter for the amount of propellant they held than the Saturn V's cylindrical tanks, and the N1's outer load-bearing frame was lighter for the load it carried than the Saturn V's overall structure. But of course having one structure do both jobs is much more lightweight. In that sense, the N1 was more of a brute force solution, while the Saturn V took a lot more...doing.

Landing profile is the same as Insight but then the rover rolls off, more like Spirit and Opportunity.

I was sure I had seen all three engines light in the Cosmic Perspective slow-mo but it was just one of the Mach diamonds that made it look like three engines were lit when there were only two.

I really like the way the Soyuz looks with people on it. Another reason they stuck with the R7 design was that they needed a way to keep the R7 from collapsing on the pad while it was being fueled. The V-2 could stand under its own weight well enough but trying to cluster them to support their own weight and also not knock each other over was too challenging (especially because they were horizontally integrated). The solution was to "hang" the core stage from the boosters. They still horizontally integrate, so they still do this. It's just easier. The Space Shuttle was vertically integrated. Energia was horizontally integrated but they positioned the four Zenit boosters such that pairs could be bolted together at the top and bottom and thus have a much more stable stack. The three boosters for Falcon Heavy are sturdy enough to stand on their own launch clamps but the core had to be really strengthened to be able to do that AND support the loads from the side boosters.

Oh yes, very clear. Well apparently my clear memories just suck

With something like the Blok D crasher stage profile for the N-1, where you stage at an altitude of around 4 km with 100 m/s of horizontal velocity, the crasher stage is going to impact so far away (and at such a relatively low speed) that you're more than completely clear of ejecta.

SN15 lit all three engines on ascent and all three engines at the flip. They did a planned shutdown of one engine once the flip was underway in order to bring down their TWR.

It had 8 thrusters to control pitch and yaw and 8 thrusters to control roll, but they were in two redundant banks. So two identical starboard yaw thrusters to rotate you in one direction and two identical port yaw thrusters to rotate you back, and so on. No means of translation.

The Vostok capsule had an independent service module, unlike the Mercury capsule, but unlike Gemini service module the Vostok service module only had RCS for attitude control. The thrusters were placed on the sidewall, pointing radially, so they could rotate the entire vehicle but could not provide translational impulse. And even if they could, it only had 9 kg of nitrogen at 59 psi which doesn't give you any meaningful dV.

Vostok had sufficient reserves for up to 13 10 days in orbit (the planned decay lifetime), but the launch failed to place the capsule in the correct orbit and it would have taken 20 days to decay, which was a week more than Gagarin had reserves for.

Definitely not possible. 1.8 full orbits at exactly 100 km would take 156 minutes. Deimos is currently undergoing retrofit at Brownsville. The FCC filing doesn't specifically say that the booster will splash down. I wonder if they try to land it on Deimos if only to recover the engines.

The current landing legs are single-use crushables. Let's see here. The burn to orbit lasts 345 seconds (there's not much we can figure out from this; burning all six engines at full throttle for that long would consume 1,413 tonnes of propellant which is much more than Starship's capacity but we know they will throttle down or shut off the SL Raptors at some point). I don't feel like doing the integration to estimate the distance covered by a vehicle with variable thrust over this regime, so I'm going to cheat and use Falcon 9 as a rough guide. A quick glance at the last RTLS launch with a good webcast suggests that SECO-1 occurs about 1400 km downrange from the pad. So in the 4900 seconds between SECO and splashdown, Starship will travel 7450 km less than the circumference of the Earth, about 81% of a full orbit. We do have to shave off some time for the descent, of course. It took SN15 about two minutes to go from 10 km to the ground. If we guesstimate that SN20 will reach terminal velocity about 20 km above the Pacific (based on the Shuttle's speed-to-altitude regime), that's about four minutes total of non-horizontal motion. So we reduce that 4900 seconds to 4660 seconds. By the power of basic math, a full orbit would be 5,750 seconds or about 96 minutes. For a circular orbit that would be an orbital altitude of 568 km ASL which seems wildly high. Even if we increase the drop time and allow six minutes of non-horizontal motion, that's still 471 km. It doesn't make sense to allow any more drop time than that because terminal velocity will be higher where it's higher up, decreasing drop time. No way is SpaceX putting a 150-tonne chunk of metal into a circular orbit HIGHER than the ISS, not on its first go-round. If anything goes wrong that would be disastrous. On the other hand, if the targeted periapsis is ~30 km ASL then the apoapsis can be a nice merry 970 km, you get an toasty entry interface at 8 km/s, and you are assured of a safe disposal if anything goes wrong. And you can still say it's a proper orbit.

Hawaii is 3700 miles from Boca Chica. 90 minutes is a lot of flight time to only go 85% of the way around the world. Granted, part of that is ascent and descent but most of it is not. Seems more likely that they would say "we placed Starship in an orbit which intentionally crossed Earth's atmosphere to ensure safe disposal if there was a problem." It would be a bad, bad day if you ended up with another CZ-5B R/B situation but with a vehicle ten times larger. And to answer my own question -- no, they can't do this, three SL Raptors would limit it to a prop load of about 550 tonnes which only gives 4.9 km/s, not nearly enough for orbit.

I wonder whether Starship will do a deorbit burn or if it will just boost to what is effectively a very, very long suborbital trajectory and come down that way. It definitely saves propellant reserves. They might even be able to get away with a smaller prop load and only sacrifice three Raptors...although that seems unlikely. This also means they don't have to worry about solving the landing leg problem yet.

Literally came here to post that. It makes a lot of sense. Avoids overflight of land during the scary parts. And they definitely need to be able to demonstrate boostback and landing burns for the booster before attempting to drop it onto land. This allows them to validate the heat shield and aerodynamic re-entry management even if they haven't worked out all the kinks in the landing sequence yet.

Yes, the concern with prop-depot distributed launch was always cadence. Even if the commercial LVs could pull it off, it was still very much time-sensitive. If SLS slips, you could end up with a mission-threatening level of boiloff. So that restricts your tug (ACES or whatever) to the limited role of putting storables into cislunar space. And with storables, you are more likely to want them pressure-fed, which means the value of propellant transfer drops (the tank *is* the turbopump in a pressure-fed regime). Starship obviates all that by being so massively overpowered and boasting so much capacity that it can accept extra loiter time. I wouldn’t imagine so. I mean, we’ve crashed tons of stuff into the moon before. As long as you drop at the proper angle and speed and altitude, it’s no big deal.

That’s limited by TLI throw. If you set Starship aside (because Starship makes everything easier) and you set SLS aside (because it doesn’t fly enough to be useful) then your max TLI throw is restricted what Vulcan, New Glenn, and Falcon Heavy can do. NG and Vulcan can do something like 9 tonnes to TLI. Falcon Heavy can do a little more. But that’s not a lot to work with.

It takes less energy to distill CO2 than O2. It takes a LOT more energy to crack CO2 and H2O into O2 and CH4 than it does to just distill O2 out of thin air.