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SpaceX Starship - Integrated Flight Test #2 - Starbase TX - Including Post Launch Dissection
- Thread starter Grendal
- Start date
No chance. Rockets don't carry propellant to dump it. Everything has a use. Starship is exceptional because of its size and the fact that SpaceX is willing to lose experimental vehicles. Everyone else focuses on every flight being perfect.
Remember depress events during testing? Those are the vents. Here's a beautiful venting shot during the last attempt at a wet dress rehearsal.
I didn't lend much credence to the idea that venting broke something because the venting process is so simple. The only way I can see venting breaking something is through the violence of the vent. Venting on the ground is venting with 1 bar of back pressure (the atmosphere). In space, there's no back pressure and they may not have accounted sufficiently for that. Venting in a vacuum is not normal.
Hmmm... I guess the images I seem to remember of previous flights were plumes of exhaust and/or during things like engine cutoff when there was some slight amount of unburned prop that escapes the nozzle.
Oh, that is a nice clear shot of the venting locations... thanks.
So, oxygen by itself isn't flammable. But it is reactive enough to make many things burn that normally wouldn't.
If your theory holds true and O2 found it's way back inside the structure of the ship somewhere, perhaps inside the engine skirt where there was even the slightest unburned methane in the exhaust, or even other material (wiring, aluminum structural material, insulation, etc...) I wonder if that's what went up in "a combustion event and subsequent fires" as the report says....
So, SpaceX also said: "The previously planned move from a hydraulic steering system for the vehicle’s Raptor engines to an entirely electric system also removes potential sources of flammability."
I wonder if that is purely a "proactive" statement, or if there's some suspicion that LOX interacted with the hydraulic TVC system somehow.
Also, this is a good point:
I wonder if that is purely a "proactive" statement, or if there's some suspicion that LOX interacted with the hydraulic TVC system somehow.
Also, this is a good point:
Oh, sure, there's propellant leakage because valves aren't perfect, but there's no dumping, per se.
Oxidization is often an exothermic reaction, so throwing something into a pure oxygen environment can result in the release of a lot of energy. That energy will help the reaction along.
Even a spark across some electrical contacts could be enough to get things going. That would start aggressively oxidizing some copper wires, or the plastic, or something else nearby, and you're off to the races. This was the tragic sequence of events behind the Apollo 1 fire.
I'm not sure what Alex is concerned about. You've got a chaotic environment because of the LOX tank blockage. The computers had time to detect partial blockages and cleanly shut down those engines, while other engines were completely blocked and blew up.
Yeah, the Apollo fire is what I was thinking... the stuff you mention in addition the things I did inside the engine skirt would be vulnerable in a O2-rich environment...
Yeah, it just wasn't addressed in what SpaceX published, but agree that's the likely set of events.
For those who have been following this topic closely there is nothing I consider noteworthy in this NSF analysis but it is a decent overview.
Here's a guy playing with pure oxygen at low pressures combined with heat to cause ignition. He starts with some experiments with brown paper, but I'm linking to an experiment with steel wool. He runs a current through it to see how it reacts in that low pressure, pure oxygen environment.
Earlier in the video, he mentions that the silver strips shown are actually made of silver because they won't burn in an oxygen environment. He also mentions that copper and stainless steel will.
Earlier in the video, he mentions that the silver strips shown are actually made of silver because they won't burn in an oxygen environment. He also mentions that copper and stainless steel will.
Thanks for posting that video, I love to see amateur scientists running experiments just to see what will happen!
Fortunately SpaceX has stated that there will not be a ship LOX vent during IFT-3. I look forward to learning what the dummy payload will be.
Fortunately SpaceX has stated that there will not be a ship LOX vent during IFT-3. I look forward to learning what the dummy payload will be.
My reading of the info from SpaceX is that the leaks they refer to are methane leaks which then combusted with the LOX being vented.
Cool video... it makes me wonder what the "effective pressure" on the ship at the altitude was when it vented the O2.
Also, one of the reason oxyacetylene torches can cut steel is the "oxy" part. That and why smoking around your grandma in the oxygen tent at the hospital is frowned upon...
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I feel like an history student from the local community college who wandered into a Math class at MIT.
Why would do you have to vent LOX vent if there is no payload? I don't see the connection. If they ended up with excessive LOX at the end of the burn, for whatever reason, why bother venting it? Rather why not take just about enough LOX commiserate to the payload weight?
I think they had a full load of LOX in order to more fully simulate the mass that Starship would be for a normal flight.
I assume they dumped some LOX to then simulate what the ship would be experiencing at the point it was approaching LEO, and would then belly-flop (mostly empty) back to earth and attempt a landing burn sequence.
I suspect this next flight we'll instead see the next item in line for payload simulator, after big wheel of cheese and Roadster.
I assume they dumped some LOX to then simulate what the ship would be experiencing at the point it was approaching LEO, and would then belly-flop (mostly empty) back to earth and attempt a landing burn sequence.
I suspect this next flight we'll instead see the next item in line for payload simulator, after big wheel of cheese and Roadster.
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My interpretation of SpaceX's statement was that it was a regulatory thing. They were trying to have little to no fuel at time of landing/splashdown. So they were purging the excess fuel to make that happen. Here is the pertinent statement:
"At vehicle separation, Starship’s upper stage successfully lit all six Raptor engines and flew a normal ascent until approximately seven minutes into the flight, when a planned vent of excess liquid oxygen propellant began. Additional propellant had been loaded on the spacecraft before launch in order to gather data representative of future payload deploy missions and needed to be disposed of prior to reentry to meet required propellant mass targets at splashdown."
The updated FAA impact assessment was heavily focused on marine impacts due to the belly smacker,. That analysis was dependant on residual propellant on board.
There are two target operating points:
Mass and velocity at reentry
Mass at launch
To match mass at launch, they need a full propellant load. One could hypothesis an extra 100 tons to simulate payload. However, the tanks theoretically would not have been sized to support 8% more volume. Extra volume used would also impact mess up ullage behavior by taking up free space. 100 metric tons is about 1.4m of ship height or most of a ring.
So assume the Ship was 100 tons light. That means it will hit its target velocity sooner and not require the normal amount of propellant. That leaves LOX to dump.
If they did have 100 tons extra loaded, that would need dumped to hit the reentry mass number.
Either way, LOX to dump. Theoretically, they would have extra methane too, but its a 3.6:1 ratio so much less to deal with and they may have burned the extra in the engines.
Aren't they planning on a hover landing now? That would seem to be a nice solution to the problem of dumping the methane as well as disassembling the vehicle; run the engines in a hover until you're out of propellant. That should produce some nice engine RUDs. Though I guess they're RPDs at that point.
Original plan to FAA was a smack down followed by the second and third burning up on entry. Since the IFT-2 had a heat sheild, the plan has changed. IFT-3 is doing a pseudo reentry burn, maybe it will try to hover also? Unfortunately, the launch licenses are light on details.
Page 6-7 had earlier plan:
https://www.faa.gov/media/27271
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