Posted on 02/03/2021 12:23:28 PM PST by CivilWarBrewing
One common factor of the last two test flights of SpaceX's SN8 and SN9 both resulting in crash landings is really bugging me..
Unlike the Falcon boosters' successful return to Earth after going vertical LONG BEFORE LANDING, the 'pitch to vertical' maneuver of the Starship rockets seems to occur TOO LATE IN THE DESCENT and just mere seconds before landing.. WHY IS THIS?
My main question is about the latent pitch to vertical before landing. Why does it wait so long to do this? Does it have to do with the tremendous weight involved that is different than the Falcon booster?
What about SPEED BRAKES? Could Starship use two or three thin titanium speed brakes to help create drag on its way down?
Thanks in advance!
I think parts flew off a Raptor engine just as it was straightening up and these Starships are just prototypes , wait until they get to SN18 or 19
Good thing worry warts like you weren’t around for testing of most WWII planes, SR71, and lots of other secret development aircraft...
The Wright brothers crashed as well... 😉
The pitch to vertical is a landing maneuver. If they did it earlier they would have to spend more fuel longer.
It seems to imply that this is the most fuel-efficient way to land.
I agree that it seems mighty precarious, that you're making everything slosh around in the tanks, by doing things so quickly.
My counter point is this: well, SpaceX figured out how to make the Falcon booster land well, so they obviously could have used that approach if they wanted to...
Overall it makes sense. Basically you want to come down as fast as possible, then decelerate as fast as possible. The longer you're in the air, the more fuel you need. It also is a negative feedback loop. The more fuel you need, the more mass you're trying to decelerate, the more energy (fuel) you need...
“Not because it is easy. But, because it is hard!”
The reason they don’t want to pitch earlier is because as soon as you go vertical, the ship will begin accelerating again, and the earlier you go vertical, the more fuel you will need to land. Starship is trying to maximize pounds to orbit while remaining reusable, so the more fuel you have to carry, ESPECIALLY fuel that you have to carry all the way to the end of the flight, cuts down on that.
I, also, wonder if they aren’t trying to shave things a little close with the landing, and they’ll probably need to try something a little less dramatic if they ever intend to return it to Earth with passengers, but... I assume they know what they’re doing with testing it this way.
As for Speed Brakes, well... that’s the entire reason it falls horizontally, the ‘belly flop’... the entire spacecraft body is a gigantic ‘speed brake’. If you ever see a wide angle shot of SN9 or SN10 coming down, they fall REALLY slowly, using the atmosphere to bleed off so much speed that you don’t need much ‘oomph’ to flip over and land. The only problem so far has been getting the ‘oomph’ to start reliably for the landing.
It looked to me like there was a problem with the 2nd engine after reaching altitude.
The primary issue has been restarting the 2 engines needed for a soft landing. They have an issue getting the two engines they need restarted. Both prototypes reliably restart only one engine.
The issue appears to be proper fuel flow ratios to more than one engine. In both landing attempts, the engine that restarts reliably is in the same spot. The 2nd engine that won’t resart is in the same position on both attempts.
Because the Starship descends in a bellyflop attitude, it falls at a much slower velocity than the Falcons and doesn’t have a lot of speed to scrub off. As far as the timing, the later you do it, the less fuel (weight) is needed. Every bit of fuel used for landing has to be subtracted from the payload performance of the rocket. The only limitation on time is you have to have adequate time given the trust available for the deceleration to take place. They only use 2 Raptor engines to decelerate and 1 to touch down, so thrust available is clearly not an issue. It seems late, but it’s an automated procedure. Compare the Falcon landing burns. They seem late too, right? SN9 didn’t crash because the decel maneuver was late. It crashed because the 2nd Raptor engine didn’t light properly. They will figure it out quickly, come up with a solution, and SN10 will nail it.
The fins and body of the rocket take on a lifting body and wing type of effect that is more controllable and more efficient than a straight vertical descent.
Sound good, eh?
Lots of Buck Rogers stuff going on with this crew. They seem to be alone in their endeavors and I ain’t gonna criticize anything they do short of neglegent human injury/death.
Wasn’t both landing due to something other than engine failure? 1st one was some kind of fuel pressure problem? Not directly related to the engines.
Without seeing the parameters of the test I could guess they were pushing the limits on purpose.
the Starship has flaps that are used during decent for control. also these test flights are not going much above 39,000 feet. might need to flip upright earlier.
I misspoke. Starship has Raptor engines, not Merlin.
Merlin is the second stage, vacuum optimized, engine on the Falcon 9.
* Are you a member in a league?
* Are there still tickets available?
* When is the next telecast?
* Where do you rank in the current standings?
Or are you fiercely retaining your amateur status?
Paint a face on the landing pad. Not just any face.....
Hellery, Nanzi, ...
That might give the rocket anti gravity
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