791–800 of 1001 posts
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Eh, if SpaceX had genuinely not expected the rocket to get off the launch pad, they would not have launched it. I expect their math was something like: 95% chance of enough engines lighting to launch 90% chance of clearing launch pad 60% chance of making 60 seconds of flight 30% chance of 2nd stage separation 15% chance of re-entry
I did sense a bit of sarcasm in the GP post. Not sure if you did too?
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Exactly, the two untested things were stage zero (all the new ground infrastructure) and stage one (booster). I think it's clear one of their biggest lessons is that the construction of the launch mount is wrong, and it REALY needs a flame diverter. Take a look at this photo: https://mobile.twitter.com/LabPadre/status/16490627841670307... That massive hole in the ground should not have happed, and I suspect that was…
I agree with this assessment and probably the biggest problem in the test. After that, they still have a fair way to go on Raptor reliability; I was a bit disappointed with the number of engine outs: clearly the engines have not arrived. I think the big win of the day was the overall resilience of the vehicle. It seemed to handle (what looked to be) possibly explosive engine failures and kept going and stayed intact.…
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The height difference is not huge, but Starship is twice the weight and 1/10th the cost ($50b vs $5bn in 2022 USD)!
And twice the thrust
Initially posted this as a reply, but going top-level, cause the hot takes are too spicy for my liking. So the plan was to test x, y, and z. Launch sequence and takeoff, stage separation and Starship engine light, and the post-launch stuff like booster wet landing, reentry, and heat tiles. The booster by itself is not aerodynamic, so the only way to test x is with a starship on top. And if you have starship, you migh…
The launch pad is not in great shape either https://twitter.com/LabPadre/status/1649062784167030785
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I suspect they were told "if we get off the ground, it's a success." Elon's been saying similar things over the last week.
Which is rightly, awesome... They just launched an 11 million pound firecracker.... It would be AWESOME if elon included actual fireworks which would go off in the event of a RUD to add some fabulousness to such events. In fact, all the devices that are stripped out for these test launches should be replaced with their equivalent weights in fireworks. Detonate them when possible during a RUD to allow for more spectac…
There's something called FTS. Said fireworks were responsible for todays RUD... ;-)
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The thing that bothers me about this rapid unplanned disassembly development methodology is all the environmental damage that this thing is doing. It was bad enough blowing up next to a wildlife preserve, but now they are (with some degree of certainty) blowing it higher up and scattering fragments across a huge area. The rockets are not getting any smaller. > so the only way to test x is with a starship on top. Why…
This is the real legacy of propulsion flight. What is the end goal of this? Moon trips for rich people? Disgusting.
Yes, advances in technology are used for wasteful things too, that doesn't mean they aren't still good for humanity.
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It's extremely, extremely tiny compared to the impact of the thousands of commercial airplane flights that happen every day. Plus, methalox burns very cleanly, second only to the much more dangerous and finicky hydrolox in terms of environmental friendliness.
It is extremely tiny now- but definitely will be something worth thinking about when (here's hoping!) SpaceX and others reach their goals. When we run 100x or 1000x current launch capacity I don't think it's unreasonable to worry about rocket pollution.
Commercial passenger flights departing in the United States produced 179 million metric tons of carbon dioxide emissions in 2019.
1 Ton of Methan produces 3 tons of CO2.
Starship+Booster fully loaded has 1000 tonnes of methane (and three times oxygen).
So a thousand Starship launches a year would be 3 million metric tons of CO2. Not nothing but (surprisingly?) less than 1.5% of commercial US flight industry.
Theoretically one can produce Methane climate neutral through bio gas. I found different prices for liquid methane (1000 to 2000 dollars?), with that it seems the fuel cost are only around 2 million per launch? That is cheap. A 1000 Starships would only cost 1 billion in Methan fuel (disregarding oxygen and heightened demand and economy of scales).
Initially posted this as a reply, but going top-level, cause the hot takes are too spicy for my liking. So the plan was to test x, y, and z. Launch sequence and takeoff, stage separation and Starship engine light, and the post-launch stuff like booster wet landing, reentry, and heat tiles. The booster by itself is not aerodynamic, so the only way to test x is with a starship on top. And if you have starship, you migh…
In the SpaceX feed they were waiting for the second stage to separate and light, and it didn't do either. So first question is why didn't it separate? I think that is the relevant one because I would expect them to have interlocks that would prevent the second stage from starting up if it were still attached to the booster. The interlocks would explain not starting up the second stage engines.
One anomaly I noticed was that the booster did not appear to shut down 100%, ever. If that was the case, that would be important because the onset of "zero g" from engine shutdown is a well tested way for the next stage to know that the stage below it has stopped firing.
Some (many? all?) spacecraft rely on the physics of the expended boost stage being much lighter than the remaining stack. This disparity means atmospheric drag on the lower stage has a bigger effect than it does on the upper stage. If the second stage retention system "lets go" when it detects zero-g, then the two pieces will begin to separate, slowly at first, and then faster when the very un-aerodynamic opening to the top of the booster gets into the slip stream.
Depending on how the second stage interlock works, it could be timed (wait t seconds and then light up) or radar (wait for distance between first and second stage) or some communication between the booster and the stage. By time is cheap, but risks a slowly separating booster being "too close" and having it become damaged from the blast of the vacuum engines starting up. Radar is likely most reliable (and most expensive), and comms would work by there is a lot of ionization going on at that speed that makes them more difficult.
So questions I would look at; First, if all the raptors didn't shut down, why not? Second, did the booster attempt a rotation and re-entry burn with the second stage still attached? Third, is there a way to "abort to orbit" this scenario where the second stage decides to let go and light up even though the first stage hasn't shut down?
Fun to watch though, its a pretty amazing rocket and that they didn't have 4 (or 5) of the raptors firing when it started off was another thing to look into. On pad aborts are a thing too, but as the parent states, there are faults that you won't get any useful data, and those you note and continue on through. I think the non-start of the raptors was of the latter.
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Some parts are interchangeable. The countdown process needs optimization. There are things missing and things which shouldn’t be there. We’re talking about speed of loading propellant, density of it, etc. Then there’s software. So much software. And a million other things. Rockets are complex, launching them doubly so.
also, to test the software you don't need to launch the rocket, so I'm not sure why you even mention that..
At some point, your in silico model needs real world data to validate it.
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Exactly, the two untested things were stage zero (all the new ground infrastructure) and stage one (booster). I think it's clear one of their biggest lessons is that the construction of the launch mount is wrong, and it REALY needs a flame diverter. Take a look at this photo: https://mobile.twitter.com/LabPadre/status/16490627841670307... That massive hole in the ground should not have happed, and I suspect that was…
>That massive hole in the ground should not have happed, and I suspect that was not an expected possibility. Interestingly, this post predicting exactly this kind of damage was flagged on HN just days ago: https://news.ycombinator.com/item?id=35590279 I think it's unlikely that SpaceX wasn't aware of the damage that would be caused. They have a pretty good engineering team, and that aspect didn't involve an anomaly,…