When (first) orbital flight?First integrated flight test occurred April 20, 2023. "The vehicle cleared the pad and beach as Starship climbed to an apogee of ~39 km over the Gulf of Mexico – the highest of any Starship to-date. The vehicle experienced multiple engines out during the flight test, lost altitude, and began to tumble. The flight termination system was commanded on both the booster and ship."
What's happening next? SpaceX has assessed damage to Stage 0 and is implementing fixes and changes including a water deluge/pad protection/"shower head" system. No major repairs to key structures appear to be necessary.
Why no flame diverter/flame trench below the OLM?Musk tweeted on April 21: "3 months ago, we started building a massive water-cooled, steel plate to go under the launch mount. Wasn’t ready in time & we wrongly thought, based on static fire data, that Fondag would make it through 1 launch." Regarding a trench, note that the Starship on the OLM sits 2.5x higher off the ground than the Saturn V sat above the base of its flame trench, and the OLM has 6 exits vs. 2 on the Saturn V trench.
I'll attempt to keep this post current with links and major updates, but would be greatly helped by information supplied by the community. I hope this can be an alternate place to discuss Starship development. While the Starship Development Threads on Reddit are not party threads, Lemmy is still small enough that I don't imagine that strict moderation will be needed in the short term.
In a Twitter Space with @ashleevance, @elonmusk shares that Starship will hot-stage during the next flight, lighting engines on the ship with some engines still running on the booster, as to Never Stop Thrusting!™️
"Hot staging" is firing the upper stage engines while it's still nominally attached to the lower stage (like resting on or loosely attached). The advantages that I gather exist: It's fast. It takes care of stage separation without needing springs or little rockets or a flip or anything. Before firing a liquid-fueled stage that may have gases in a tank ("ullage"), you have to settle the contents so that the engine intakes suck only liquid (maybe using "ullage rockets"), but if you're still accelerating at separation, that's automatically taken care of.
But if you intend to reuse the first stage, well, I wonder whether six engines igniting will be too hard on it.
Apparently U.S. Titan rockets, a lot of Soviet / Russian ones (Soyuz, Progress, N-1), and (some?) Chinese Long March rockets were designed with hot staging.
Joe Barnard @joebarnard replies: "'okay so when I hot stage it’s “an anomaly” and I’ve “torched another flight computer” but when SpaceX does it it’s fine???'
"We made sort of a late-breaking change that’s really quite significant to the way that stage separation works," Musk said, describing the switch to hot staging. "There’s a meaningful payload-to-orbit advantage with hot-staging that is conservatively about a 10% increase."...
Musk said that, for Starship, most of the 33 Raptor engines on the Super Heavy booster would be turned off, but a few still firing, when the engines on the Starship upper stage are ignited. Doing so, he said, avoids the loss of thrust during traditional stage separation, where the lower stage shuts down first.
Doing so requires some modifications to the Super Heavy booster. Musk said SpaceX is working on an extension to the top of the booster “that is almost all vents” to allow the exhaust from the upper stage to escape while still attached to the booster. SpaceX will also add shielding to the top of the booster to protect it from the exhaust.
“This is the most risky thing, I think, for the next flight,” he said of the new stage separation technique.
Besides the change in stage separation, Musk said SpaceX made a “tremendous number” of other changes to the vehicle, “well over a thousand.” He didn’t go into details about the changes, ...
SpaceX also made improvements to the Raptor engines, with Musk describing the vehicle launching in April as using a “hodgepodge” of engines built over time. The Raptors on the new vehicles include changes to the hot gas manifold in the engine to reduce fuel leakage.
Those changes, he said, gave him more confidence in the success of the next launch. “I think the probability this next flight working, getting to orbit, is much higher than the last one. Maybe it’s like 60%.” In an online conversation in late April, he estimated a “better than 50% chance” of success on the next launch.
In another note, Musk finally learned some caution!
Musk, asked about any plans for a Starlink IPO, declined to comment. “It would not be legal for me to speculate about a Starlink IPO,” he claimed. “I think it’s against regulations to talk with any kinds of specifics about a future public offering.”
Edit: Peter Hague PhD @peterrhague: Thus far Musk estimates $2-3bn invested by SpaceX so far in Starship. The price of a single SLS launch
At stage separation how horizontal is Starship? If there was no vertical moment then how significant would the gravity loss actually be?
AFAIK most of the gravity loss is in the first few second of a launch but I don't have any idea what you are losing by the time you get to stage separation.
Interesting, most of the Soviet rockets that uses hot staging had a truss between each stage to allow the exhaust to vent. As far as I know starship doesn't have anything like this yet, I wonder if they'll add some or if they're just gonna see what happens without it 😂
Such a device has been spotted at the shipyard. It has been speculated that the reason the ship QD was removed was to adjust it for the height added by the vented spacer.