Silavite

Thrust termination ports (blow-out panels) could provide control for the exact amount of impulse necessary.

Are the ground stations planning to use mechanically steered antennas now? I was under the impression that phased arrays would be used. (Though I'm a bit relieved if they are dropping the phased array idea. Even with SpaceX's price dropping wizardry, I don't think that they could make phased arrays cheaply enough.)

That's comparing SL ISP of a kerolox engine to vacuum ISP of a methalox engine. Visiting Wikipedia gives me a sea level ISP of 311 s for the RD-180 and a vacuum ISP of 359 s for the RD-0124. The numbers for Raptor are 330 s at sea level and 380 s in vacuum (for the sea level and vacuum engine types, respectively). Raptor's ISP numbers are still impressive, but it's not quite an 80 second improvement. It's also worth noting that Raptor is expected to have a better TWR than both of these engines.

What does he mean by, "cryo strength bump of CH4"? Is he referring to the increase in strength of stainless steel at the cryogenic temperatures of liquid CH4?

Ayup. They're saying that it should be ready before the end of 2021 (for now). https://arstechnica.com/science/2020/06/james-webb-space-telescope-will-absolutely-not-launch-in-march/

Payload deployed. Congrats on another successful mission, SpaceX!

I feel like that's true most of the time, but not always. For example, I think Tim did a good job in this interview in getting Elon to talk about Methalox vs Kerolox and why SpaceX declined to use an aerospike engine (related to combustion efficiency in aerospikes vs bell-nozzles).

@tater Ignore my previous post. Just realized that the precession will occur about the equator, not about the ecliptic. Thus the orbit will become misaligned from the terminator as the Earth revolves around the sun.

You could get the same, constant sunlight from a sun-synchronous orbit with an inclination of 113.5 degrees (90 deg + Earth's equatorial tilt of 23.5 deg w.r.t. the ecliptic) and altitude of 3127 km. The path of the orbit follows the Earth's terminator, so the spacecraft would be under constant illumination. The downside is that this orbit is smack inside the inner Van Allen belt. That said, if you're looking to test the durability of a space system, this could be viewed as a positive. Ignore this

About the launch vehicle discussion; https://arstechnica.com/science/2020/05/nasa-is-counting-on-a-lot-of-unproven-rockets-for-its-artemis-plan/

The pedant in me feels obligated to point out that the inverted gull has an added bonus of reducing interference drag for a low mounted wing. That said, this was indeed likely nothing more than a bonus as opposed to the more pertinent consideration of a 13' propeller chopping through carrier decks.

I was thinking that roll could be handled purely by the RCS (and thrust vectoring when applicable). There isn't a need for rapid rolling, and I don't see where large external torques in the roll axis would arise.

I had the idea of using a single set of control surfaces which do not rotate, but only translate. Here's a crude MS Paint approximation: Benefits: Fewer control surfaces required in total could help to reduce mass and potential points of failure. The fact that these surfaces move perpendicular to the velocity vector (in a skydiver configuration) rather than directly against it means that less powerful and thus less massive actuators would be required. Drawbacks: A big slot on the side of the spacecraft for the necessary translation would likely be... undesirable during reentry. Even if the actuators could be smaller, they're delivering power to a moving surface. Thus, the actuator would have to move with the control surfaces, or some kind of system would be needed to deliver the force. (Or maybe you could try using some kind of linear motor.) Comments? I'm sure there are more flaws which I haven't thought of yet.

Was this a gamma ray burst? The coverage I've seen thus far just seems to be talking about an, "explosion," without much further detail about the exact phenomena.

Apparently Tesla is looking to try and substitute Ni-Co-Al vehicle batteries with Li-Fe-P. Tesla in talks to use CATL's cobalt-free batteries in China-made cars

According to Shotwell SpaceX is likely to spin-off Starlink. (In a similar manner to how they spin-off Starlink satellites from the F9's upper stage ) https://arstechnica.com/information-technology/2020/02/spacex-plans-likely-spinoff-and-ipo-for-starlink-broadband-division/

Some takeaways from the post-flight press conference. Hardware for DM-2 will probably be ready sometime in February, but the flight itself won't happen until a bit later due to necessary checks/scheduling. This test doesn't really have applications outside of commercial crew. Whether DM-2 will be short duration or long duration is TBD. NASA is still planning to purchase another Soyuz seat.

A bit off-topic, but I cannot resist sharing this gem

How would the heliosphere and stellar bow shock affect our observations of objects outside the solar system, if at all?

I'm a bit late to the party, but I don't think a the factors are quite black-and-white with respect to the certainty of the SLS program. For example, take the patronage of Richard Shelby (R-AL) to the SLS. I doubt the program would be cancelled if his support were to be removed, but I think that there would be some shake-ups. This is evidenced by the fact that support for the SLS isn't universal. A few months ago, the chairman of the Senate budget committee sent a letter to Bridenstine which contained (among other things) criticism of the SLS program. We're all used to treating Shelby as some omnipresent, omnipotent god as far as U.S. spaceflight is concerned (I'm exaggerating just a tad ), but his backing of the SLS program is not guaranteed. It is contingent several factors, including that— Shelby is alive and well. Shelby is 85 years old. According to actuarial tables provided by the U.S. Social Security Administration, an 85 year old male has (on average) 6 years of life remaining. I do not know the details of Shelby's personal health, but the chance that he dies or is rendered unfit to serve as a senator due to his health is likely non-trivial. Shelby is elected. If Shelby is alive and fit, then he must be reelected in 2022. Given Alabama's partisan lean and Shelby's own sterling electoral history, I think he is nearly guaranteed reelection. Shelby is the head of the appropriations committee. If Shelby's party were to lose the Senate, then he would cease to be the chairman of the Senate appropriations committee. This isn't likely given the geographic advantages the Republicans have in Senate elections, but I would still deem it to be a non-trivial possibility. Supporting the SLS program is to Shelby's benefit. Unless MSFC sprouts wings and flies to another state, this seems almost guaranteed. (Hopefully I didn't run afoul of Rule 2.2b in discussing all this. I used an example which is political in nature because it is linked so closely to the SLS program, and because it illustrates the similarities in doubt between government backed and commercial ventures. I think I should be in the clear since 2.2b only prohibits content which is political and unrelated to spaceflight.) Anyway, this is only a single political example. The point I'm trying to make is that there are very real scenarios which cast doubt upon the success of the SLS program: I would not call it a guarantee. (For the record, I do think that SLS has more inertia due to it's government backing, I just also think that it's not guaranteed.)

Perhaps I just missed it in all of the excitement, but what time on Saturday is the Starship presentation occurring?

It's long fulfilled its purpose, but I'm certain this song will always be insufferably catchy.

I'm surprised that no one has posted any of Levi Cowan's videos yet. His analyses are excellent.