RCgothic

Well starship can certainly ship more catwalk to the moon than either NT or Dynetics.

Looked like a two engine landing burn the whole way to touchdown. New York Times runs a story: https://www.google.com/amp/s/www.nytimes.com/2021/05/05/science/spacex-starship-launch.amp.html

Maybe they'll be able to recover the camera drives intact this time and give us some clean footage eventually.

Tile rectangle seems reasonably intact. Note that if you're reading Scott Manley's tweet about a few being missing from the smaller patch down near the engines, they were missing Pre-Launch. Since the static fire I hear.

Landing success!

Tank farm activity!

It's more dependent on whether there's a docking port free at the ISS now. As just mentioned in the HLS thread, the ISS is just barely capable of supporting non-operational missions. Fitting a months-long DEMO mission in around regular crew rotations and supply launches is not trivial.

Selecting Starship saved NASA over $14 billion dollars.

We have no way of knowing it to the day. A tumbling object could hit a denser air patch broadside on and come down pretty soon. Or it may not. The rate of decay is irregular. Maybe a tracking company like LEO Labs might have a rough idea, but I haven't seen any public figures.

Scrub. No SN15 flight today.

I also would have picked Dynetics 1st place before reading the selection report. I thought it would be cheaper than BO, with fewer moving parts and a nice underslung module. But it's hard to argue with a negative mass budget likely to get more negative, not less. I also assumed SpaceX were 2nd place at best due to being the biggest schedule risk , but the selection document actually placed them as least risky and most likely to make the nominal schedule. I found that surprising in particular.

Yes, it is wasteful. Return to launch site comes with a hefty performance penalty as Superheavy has to reserve a sizeable amount of fuel for the boostback burn. Not two thirds or even half its fuel though, as relieved of the mass of the Starship Upper Stage it has a very much more favourable mass ratio and can therefore extract a lot more DV from the remaining propellant. It's notable that even with this performance penalty Starship Superheavy manages almost twice Saturn V's mass to LEO.

An ever increasing population of transhumans requiring a baseline human mother to produce sounds like the potential pool of mothers is going to be proportionately declining. Each mother being sterile after producing *one* offspring is not going to be sufficient to supply the rate of replacement. IRL we currently need about 2.2 offspring per mother with a theoretically fully breeding population to maintain a stable population. If transhumans can't produce themselves that number will go up and up until it's unsupportable.

Yes, you're certainly right. I've got to start applying sanity checks before I post.

Being a bigger stage, even though it will almost certainly break up the chances are the bits will be bigger. Bigger first stage engines. Bigger internal tanks. Larger thrust structures. And because it's uncontrolled we're probably not going to get enough time for an actionable warning. A single orbit is around a thousand miles ground track, and twelve minutes is the difference between coming down on NY or London.

Resilience was in space longer than any Skylab capsule mission.

They don't machine aluminium alloy isogrids for the fun of it. It's a ridiculously expensive technique, it's just that acheiving the same result with welding on those materials is basically impossible, it's hard enough to get a decent friction stir in a barrel weld, let alone all those intricate details. On the other hand stainless steel is comparatively not difficult to weld. There's no point isogridding if welded struts work just as well. And the stainless steel is chosen over the more conventional aerospace materials because it can better withstand the heat of re-entry without excessive heat shield.

NASA suspends work on HLS due to protests by Dynetics and NT until GAO sorts them out. Don't think this is going to have any bearing on SpaceX's progress though TBH.

How not to win international friends:

More like C4, but yes, basically. It's a line of charges up the side of the tanks that can be automatically triggered by the on-board guidance system if it detects the rocket straying from its planned flight path. It can also be triggered manually by remote. When triggered the charges unzip the tanks and let all the fuel out so there can be no explosion on the ground and the rocket can't stray even further from its planned safety area (because the engines are starved of fuel). It also compromises the structural integrity of the rocket, which then tends to be ripped into pieces by aero forces. I'm not completely clear on whether many bits scattered over a wider area is intentionally preferable to a single large bit, but perhaps small bits slow faster and are more likely to be contained within the safety exclusion zone. Edit: I've only now realized that the comment I was replying to was probably meant facetiously. I'm not firing on all gas generators yet this morning, clearly. My bad.

Might get a flight of SN15 today:

Pretty sure expendably it can. Reuse eats a lot of margin both in dry mass and fuel reserved.

Same second stage. Heavier payload = less DV. So first stage has to drop the second stage off higher and faster, reserving less margin for landing.