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Old 2020-12-10, 02:50   #1035
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What was it that this vehicle was supposed to do? It did not turn out very well from the looks of it.
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Fuel header tank pressure was low during landing burn, causing touchdown velocity to be high & RUD†, but we got all the data we needed!

Even reaching apogee would've been great, so controlling all way to putting the crater in the right spot was epic!!
†Rapid Unscheduled Disassembly

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Old 2020-12-10, 02:54   #1036
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I think that they had the engines throttled back to start with, because 1 engine was enough for the test hops (with a dummy load on top). Since the low pressure in the fuel tank happened, there was not enough thrust at the end to slow it down fast enough. That also likely explains the odd exhaust color. Fuel is used to cool the engines and protect it. Once you lose that, hot oxygen can attack the metal.
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Old 2020-12-10, 09:26   #1037
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That also likely explains the odd exhaust color. Fuel is used to cool the engines and protect it. Once you lose that, hot oxygen can attack the metal.
the colour reminded me very strongly of nitrogen dioxide.

N_2H_4 burn-off perhaps?
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Old 2020-12-10, 09:35   #1038
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I watched the latter part of the video. The liftoff seemed slow. I wondered what all the engine misbehavior was about.
There were some tests that simulated engine failure. The vid shows how quickly the engines are re-gimballed to adjust for the defunct engine(s).
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Old 2020-12-11, 18:12   #1039
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Quote:
Originally Posted by Uncwilly View Post
I think that they had the engines throttled back to start with, because 1 engine was enough for the test hops (with a dummy load on top). Since the low pressure in the fuel tank happened, there was not enough thrust at the end to slow it down fast enough. That also likely explains the odd exhaust color. Fuel is used to cool the engines and protect it. Once you lose that, hot oxygen can attack the metal.
There must be pumps to supply the engines with what they need. I would not think a lowering of tank pressure would interfere with pump operations that much, unless a negative G force was involved during the attempted landing.

A bit off-topic given the current context. The two Crew-Dragon flights had a camera inside the second stage. The engine bell was white-hot both times. Those must be made from something quite special to tolerate that much heat.
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Old 2020-12-11, 18:25   #1040
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Quote:
Originally Posted by xilman View Post
the colour reminded me very strongly of nitrogen dioxide.
Cu

Quote:
Originally Posted by storm5510 View Post
There must be pumps to supply the engines with what they need. I would not think a lowering of tank pressure would interfere with pump operations that much, unless a negative G force was involved during the attempted landing.

A bit off-topic given the current context. The two Crew-Dragon flights had a camera inside the second stage. The engine bell was white-hot both times. Those must be made from something quite special to tolerate that much heat.
The powerhead of the rocket engine has/is those pumps. If the supply line feeding those pumps does not have enough pressure, they will starve. (Pumps are designed to run a certain head pressure). The final burn was coming off the 'small' header tanks. Those are designed to be able to feed the engines during this maneuver. The tanks are pressurized with hot gas produced by the engines. Some rockets use helium to keep the tanks at pressure (a small volume of the liquid a small tank can expand to a very large volume of gas). The Star Ship is designed to use the autogenous system, because there are no helium fueling stations on the moon or Mars.
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Old 2021-02-03, 17:30   #1041
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SpaceX's 2nd Starship test flight ends with another kaboom
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The full-scale stainless steel rocket reached its intended altitude of 6.2 miles (10 kilometers), slightly lower than the last one. Everything seemed to be going well as the 160-foot (50-meter) Starship flipped on its side and began its descent. But it did not manage to straighten itself back up in time for a landing and slammed into the ground.

"We've just got to work on that landing a little bit," said SpaceX launch commentator John Insprucker. "Reminder - this is a test flight."
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Old 2021-02-03, 18:38   #1042
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I'm not a fan of humans further away than low orbit - as that's just throwing good money after bad money. (the burden it lays at the taxpayers because our technology is not so advanced yet, that burden is way way too high and it's all about some monkey surviving in space then rather than increasing the knowledge of humankind).

That said - it's tests what happens here - they're supposed to crash a lot - otherwise you clearly aren't testing everything very well!

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Old 2021-02-03, 18:52   #1043
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I'm not a fan of humans further away than low orbit - as that's just throwing good money after bad money. (the burden it lays at the taxpayers because our technology is not so advanced yet, that burden is way way too high and it's all about some monkey surviving in space then rather than increasing the knowledge of humankind).
It is not entirely tax payers' money.

Private enterprise already has ambitions for lunar and Martian missions and is putting their money where their mouths are. IMO, there is a very good chance of them occurring within 5-10 years.
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Old 2021-02-03, 19:03   #1044
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It is not entirely tax payers' money.

Private enterprise already has ambitions for lunar and Martian missions and is putting their money where their mouths are. IMO, there is a very good chance of them occurring within 5-10 years.
Manned mission to Mars is order 10 trillion dollar - except if you want to 'throw away the people' with certainty. In short if you do not care they get killed with 99.99% certainty very quickly during the mission.

And all they would do on mars such people is sit in a bunker deep underground as going outside is too dangerous and would risk their life too much. The only advantage of having them there is that they can remote operate robots a little faster.

Why pay all those trillions of dollars if the alternative is autonomeous software with robots - which we didn't have yet - for example because CPU's and programming wasn't that advanced yet - in the 1960s?

Note that as for mars so far the only succesful landings on the Marsian soil has been done by NASA last time i checked.

There is nothing in space which privately is worth more cash than the same material is on the surface of planet earth. It's all taxpayers dollars what it is about.

Saying that some missions were 'privately paid' by Musk is also not entirely true - he got billions of subsidy cash first. So wasting a rocket with a cardboard Tesla car to 'test' some rocket out in space is not exactly privately paid either - that was tax payers dollars too.

As far as i know not even Musk, whose wealth comes close to some of the Arab oil sheikhs, posseses trillions of dollars. He's simply a businessman good in making money. Saying that he would want to pay something privately or could afford going manned to Mars privately is a nonsense story.

p.s. there is lots of nonsense stories out there in the media. Like Musk who optimistically said launching a rocket he would do for 10 million dollar. Yet in reality every mission he brings 4 astronauts to ISS, he'll catch what is it like 90 million a ticket or in short he catches over 300 million dollar - and if we add the billions of subsidy - it's right now a couple of billions a mission - which in the long run could go to 0.5 billion dollar for a single mission. Still factor 50 more than what is out there in the media.

Guess anyone can afford a ticket to the Moon?
Cheapest price i heard to go to the moon is 700 million dollar.
Yet that'll be eating babi papi pangang all the way to the moon without return ticket i guess.

Sure Jeff Bezos could. But will he?

They all want a share of those trillions of dollars if in future some president is stupid enough to sign off for a manned mission to Mars. And otherwise some dude in the EU. Not good enough to run a small ministery in Germany - good enough as EU president it seems. Yet not good enough to even buy a handful of vaccins. Some dude like that in future might sign off - who knows? They all want a chance to cash in some of those trillions!

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Old 2021-02-04, 01:05   #1045
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Watching this reminded me of the B&W video's of the early 1960's Atlas tests. John Glenn was present for many. He would have to ride one into orbit. I doubt having the escape tower on top brought him much comfort. I am sure he would have liked going to the moon. NASA finally allowed him to participate in a shuttle mission in 1998. He was 77 years old at the time.
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