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Starship's Third Flight Test [video]

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Re: Starship's Third Flight Test [video]

#201

Post by dotnet00 »

DarmokJalad1701 wrote: post #167
Laremere wrote: post #148

Earlier quoted context omitted.

Parent's (correct) point is that it isn't a matter of the ascent trajectory. They can't leave the Starship up in orbit, and where it reenters needs to be controlled.

> They can't leave the Starship up in orbit, and where it reenters needs to be controlled. Why? Plenty of boosters re-enter uncontrolled and burn up all the time.

Typically American policy is to have a controlled reentry option for as much as possible. The disposable first stages of all rockets don't need a controlled reentry because they are always suborbital and thus their splashdown location is relatively well known ahead of time. The second stages are typically supposed to deorbit and burn up over water after a launch to LEO. There are occasional cases where something goes wrong and they fail to deorbit, which is when we sometimes hear of the burn up due to gradual orbit decay being witnessed over land.

Re: Starship's Third Flight Test [video]

#202

Post by baq »

johnyzee wrote: post #138
travisgriggs wrote: post #126

Earlier quoted context omitted.

I wouldn’t classify the re-entry survival problem as icing. But otherwise, I agree with you.

Yeah, breaking up in-air during re-entry (at 65 km going by last telemetry) seems like a potential big issue to fix.

it's the expected outcome of an imperfect (literally not precisely perfect) reentry. something went wrong. it could be a very minor thing like a stuck valve somewhere. we'll know in the next test if they figured it out.

Re: Starship's Third Flight Test [video]

#203

Post by LorenDB »

baq wrote: post #197
Laremere wrote: post #172

Earlier quoted context omitted.

They might do one to test deployment, but it'd be a throwaway. Their relight test was skipped (not said why), so they still don't have confirmation they can control where Starship re-eneters. Until that happens, it's very unlikely they'll target actual orbital velocity. The Starlink satellites do have thrusters, but they're ion engines, so not nearly enough thrust to get that last bit into orbit before they'd re-ente…

99% chance that they lost attitude control hence couldn't point the business end towards wherever they wanted to. we know they can relight the engine on the booster and we know they can relight for landing burns. no surprise if the next launch has a couple pre-production big starlink birds.

On the contrary, they absolutely had attitude control. Otherwise reentry would have seen the ship tumbling out of control and quickly breaking up. Instead, SpaceX was able to begin a controlled reentry in the upright position, indicating nominal orientation performance.

Re: Starship's Third Flight Test [video]

#204

Post by [deleted] »

Daneel_ wrote: post #194
hughes wrote: post #133

Earlier quoted context omitted.

The boostback burn demonstrated relight today.

The key demonstration is “relight in a vacuum”, which was the test that was skipped late in the stream. If you can do this then deorbiting is possible. Relight of the booster doesn’t demonstrate this, unfortunately.

[deleted]

Re: Starship's Third Flight Test [video]

#205

Post by dotnet00 »

golol wrote: post #190
dotnet00 wrote: post #171

Earlier quoted context omitted.

The latest Soyuz revision is ~$50m per launch, it has a payload less than half of a Falcon 9 that lands on a droneship, and ~2/3rd of a Falcon 9 that returns to launch site. Making it twice the cost per kg. The highest flight rate it has ever achieved has been 2/month. It has a 96% success rate. The latest Falcon 9 revision is ~$67m per launch. Lately it flies every ~3 days. Over the past year it has flown ~100 times…

>The latest Falcon 9 revision is ~$67m per launch And that is the price, the cost is unknown but likely lower.

Yeah, the internal cost is believed to be ~$30m, but I didn't compare on that number since we don't have a well known number for Soyuz's internal cost.

Re: Starship's Third Flight Test [video]

#206

Post by dotnet00 »

perihelions wrote: post #199
dotnet00 wrote: post #185

Earlier quoted context omitted.

The number going around from people who typically do this kind of thing is a ~55x235km orbit: https://twitter.com/planet4589/status/1768270310199935299 I'm not really in a place to judge your math right now to really add anything on that.

Yeah, that guy's absolutely a domain expert! But note that he writes -55 km, not +55 km—that is a suborbital trajectory. Its perigee is below the earth's surface; -55 km is a negative altitude. (He's also clearly using a different set of data than I have access to. I can't read the context of the Twitter thread so I don't know what numbers he's looking at).

Ooh that's a good catch, I subconsciously substituted the -55 for ~55!

Re: Starship's Third Flight Test [video]

#207

Post by BenoitP »

grecy wrote: post #191
BenoitP wrote: post #136

FR24 shows a Dassault Falcon 900EX doing circles around the expected Starship re-entry location (Perth to Perth flight plan): https://www.flightradar24.com/MXJ/345b8f09

From a safety perspective, how does that work? This is obviously a test, and safe to say the vehicle was out of control and not entirely predictable. I realize they wouldn't fly into the actual predicted landing area, but just being close must be a risk. Would the flight crew on that plane literally be scanning the sky above them to make sure they're not in the direct path of whatever comes down at whatever speed?

I guess some risk analysis can be made with the plane's and Starship's cross-section.

Let say they are cubes of 30m each. The expected area where they might both be present to be a 5km square. That's a 0.000025 chance of collision at most; and I suppose the plane is away from the center of the expected Starship Gaussian. I'd personally ride in that plane and risk that, even to just to get a glimpse of the reentry.

Re: Starship's Third Flight Test [video]

#208

Post by iwontberude »

dotnet00 wrote: post #171
iwontberude wrote: post #147

Earlier quoted context omitted.

Nevermind

The latest Soyuz revision is ~$50m per launch, it has a payload less than half of a Falcon 9 that lands on a droneship, and ~2/3rd of a Falcon 9 that returns to launch site. Making it twice the cost per kg. The highest flight rate it has ever achieved has been 2/month. It has a 96% success rate. The latest Falcon 9 revision is ~$67m per launch. Lately it flies every ~3 days. Over the past year it has flown ~100 times…

I don’t know what I’m talking about. Thanks for the info.

Re: Starship's Third Flight Test [video]

#209

Post by baq »

LorenDB wrote: post #203
baq wrote: post #197

Earlier quoted context omitted.

99% chance that they lost attitude control hence couldn't point the business end towards wherever they wanted to. we know they can relight the engine on the booster and we know they can relight for landing burns. no surprise if the next launch has a couple pre-production big starlink birds.

On the contrary, they absolutely had attitude control. Otherwise reentry would have seen the ship tumbling out of control and quickly breaking up. Instead, SpaceX was able to begin a controlled reentry in the upright position, indicating nominal orientation performance.

they were tumbling, just slowly. they started reentering side first. that it broke at 65km was unsurprising - shuttle experienced peak heating about there.

Re: Starship's Third Flight Test [video]

#210

Post by Plasmoid2000ad »

LorenDB wrote: post #203
baq wrote: post #197

Earlier quoted context omitted.

99% chance that they lost attitude control hence couldn't point the business end towards wherever they wanted to. we know they can relight the engine on the booster and we know they can relight for landing burns. no surprise if the next launch has a couple pre-production big starlink birds.

On the contrary, they absolutely had attitude control. Otherwise reentry would have seen the ship tumbling out of control and quickly breaking up. Instead, SpaceX was able to begin a controlled reentry in the upright position, indicating nominal orientation performance.

I'm no so sure, it at least looked like it was tumbling before and throughout re-entry. If they had attitude control, I think they would have at least stopped the visible rotation at some point before re-entry?

I'm not sure why the ship not immediatly breaking up, but eventually breaking up is proof that they at attitude control - especially against what the live feed showed - rotation.

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