But those of us who grew up thinking it was perfectly natural for a landing manned spacecraft to have the undivided attentions of an aircraft carrier and various support craft
I think this pretty much encapsulated my thinking on the subject. And yet I always thought the the land based Soyuz returns were a much better way of doing it. Go figure.
SpaceX uses pintle throttles/injectors which combine variable obstruction to flows with maximal mixing of combustibles. That's why such deep throttling is available reasonably smoothly without all the popping and farting. The question hangs though, as to whether a trained human pilot could have sufficient finesse to more-or-less hover slam though. Meaning that in terms of fuel efficiency ( which includes the case of having enough fuel at all for a given manoeuvre ) that is the prime case to measure against. My intuitive answer is that a well trained computer would be way better. You don't want the case where the pilot has run out of fuel a mere 100 feet up, this is a somewhat similar scenario to the development of jet ejection seats that work ( without killing the pilot ) from zero altitude at zero knots.
Now the Apollo landers reached the Moon's surface with hypergolic propellants, but they have low specific impulse which is fine for the lunar surface gravity. While the Draco engines are a proven ripper for emergency egress, it will be interesting to see how they perform for nominal approach and landing. Of course you could Draco down to the sea surface which gives more tolerance for the occupants in terms of jerks on contact, but then you may as well have parachuted huh ? Do we then use some bouncy ball cushions* like a Mars mission ? :-)
Cheers, Mike.
* Or if it is truly like a car crash then just put automotive air bags ( suitable adapted ) in the crew compartment. This is a well understood and mature technology, including the biphasic inflation feature so as not to kill people.
( edit ) If you are really curious one can always refer to how it goes down when professional racing drivers cock it up ( 3:30 onwards is the slo-mo ). { The sub-contexts here are that 3 cars into 1 corner didn't go, that is a $350K+ AUD write-off, and all axes of the roll cage were tested. } I would emphasise the additional importance of a Hans device to protect the cervical spine, personalised molding of the seat and the five+ point harness restraint. The roll cages are ~ $80K+ cost, with high grade titanium alloy plus around 1000 man-hours of preparation, specifically specialist welding techniques.
I have made this letter longer than usual because I lack the time to make it shorter ...
... and my other CPU is a Ryzen 5950X :-) Blaise Pascal
To be clear : I am referring to the Super Draco engine for powered returned to land. The key question is how much time at what throttle level do you have to use ?
There is an impressive 7.2K Newton maximum available per engine, the nominal return payload is 3000 kg and so (8*7.2)/3 = 19.2 m/s^2 or 1.95g leaving an excess of 0.95g upgoing at full throttle. I have seen talk ( without references ) of 25% of full being the level of deep throttle ie. without stop and restart. That lower amount gives 4.8 m/s^2 or about 0.49g. Hence that gives the pilot the dynamic range of 0.51g down through to 0.95g up to play with in regulating descent with the engines operating ( ballpark figures ). However one can restart as often as you like ( provided fuel remains obviously ). There is a roughly four-fold difference in fuel consumption b/w those minimum & maximum settings. Now if you are not returning 3000kg then recalculate .....
{ .... in fact the pad abort test had nett upward going 3.8g ( 160 kph in 1.2 seconds ) or 4.8g total thrust, so m = F/a = (8*7.2)/(4.8*9.8) = 1220 kg. The magic question is how much fuel, or alternatively how much of a full tank, did they use in that test ? }
Cheers, Mike.
I have made this letter longer than usual because I lack the time to make it shorter ...
... and my other CPU is a Ryzen 5950X :-) Blaise Pascal
I've read that the Federal Aviation Administration is concerned with the pilots' ability to manually pilot the aircraft in case the automatic pilot fails because ,say, of ice in the Pitot tubes as happened to a French airliner over the South Atlantic, resulting in the loss of the aircraft.
Tullio
That is another matter altogether and one reason why I will only fly British Airways. I would like to maximise my chances of getting there in one piece.
Waiting for Godot & salvation :-)
Why do doctors have to practice?
You'd think they'd have got it right by now
RE: But those of us who
)
I think this pretty much encapsulated my thinking on the subject. And yet I always thought the the land based Soyuz returns were a much better way of doing it. Go figure.
SpaceX uses pintle
)
SpaceX uses pintle throttles/injectors which combine variable obstruction to flows with maximal mixing of combustibles. That's why such deep throttling is available reasonably smoothly without all the popping and farting. The question hangs though, as to whether a trained human pilot could have sufficient finesse to more-or-less hover slam though. Meaning that in terms of fuel efficiency ( which includes the case of having enough fuel at all for a given manoeuvre ) that is the prime case to measure against. My intuitive answer is that a well trained computer would be way better. You don't want the case where the pilot has run out of fuel a mere 100 feet up, this is a somewhat similar scenario to the development of jet ejection seats that work ( without killing the pilot ) from zero altitude at zero knots.
Now the Apollo landers reached the Moon's surface with hypergolic propellants, but they have low specific impulse which is fine for the lunar surface gravity. While the Draco engines are a proven ripper for emergency egress, it will be interesting to see how they perform for nominal approach and landing. Of course you could Draco down to the sea surface which gives more tolerance for the occupants in terms of jerks on contact, but then you may as well have parachuted huh ? Do we then use some bouncy ball cushions* like a Mars mission ? :-)
Cheers, Mike.
* Or if it is truly like a car crash then just put automotive air bags ( suitable adapted ) in the crew compartment. This is a well understood and mature technology, including the biphasic inflation feature so as not to kill people.
( edit ) If you are really curious one can always refer to how it goes down when professional racing drivers cock it up ( 3:30 onwards is the slo-mo ). { The sub-contexts here are that 3 cars into 1 corner didn't go, that is a $350K+ AUD write-off, and all axes of the roll cage were tested. } I would emphasise the additional importance of a Hans device to protect the cervical spine, personalised molding of the seat and the five+ point harness restraint. The roll cages are ~ $80K+ cost, with high grade titanium alloy plus around 1000 man-hours of preparation, specifically specialist welding techniques.
I have made this letter longer than usual because I lack the time to make it shorter ...
... and my other CPU is a Ryzen 5950X :-) Blaise Pascal
If we can land 747's and
)
If we can land 747's and A380's on full autopilot, a piddling little space ship should be no problem?
Waiting for Godot & salvation :-)
Why do doctors have to practice?
You'd think they'd have got it right by now
To be clear : I am referring
)
To be clear : I am referring to the Super Draco engine for powered returned to land. The key question is how much time at what throttle level do you have to use ?
There is an impressive 7.2K Newton maximum available per engine, the nominal return payload is 3000 kg and so (8*7.2)/3 = 19.2 m/s^2 or 1.95g leaving an excess of 0.95g upgoing at full throttle. I have seen talk ( without references ) of 25% of full being the level of deep throttle ie. without stop and restart. That lower amount gives 4.8 m/s^2 or about 0.49g. Hence that gives the pilot the dynamic range of 0.51g down through to 0.95g up to play with in regulating descent with the engines operating ( ballpark figures ). However one can restart as often as you like ( provided fuel remains obviously ). There is a roughly four-fold difference in fuel consumption b/w those minimum & maximum settings. Now if you are not returning 3000kg then recalculate .....
{ .... in fact the pad abort test had nett upward going 3.8g ( 160 kph in 1.2 seconds ) or 4.8g total thrust, so m = F/a = (8*7.2)/(4.8*9.8) = 1220 kg. The magic question is how much fuel, or alternatively how much of a full tank, did they use in that test ? }
Cheers, Mike.
I have made this letter longer than usual because I lack the time to make it shorter ...
... and my other CPU is a Ryzen 5950X :-) Blaise Pascal
I've read that the Federal
)
I've read that the Federal Aviation Administration is concerned with the pilots' ability to manually pilot the aircraft in case the automatic pilot fails because ,say, of ice in the Pitot tubes as happened to a French airliner over the South Atlantic, resulting in the loss of the aircraft.
Tullio
That is another matter
)
That is another matter altogether and one reason why I will only fly British Airways. I would like to maximise my chances of getting there in one piece.
Waiting for Godot & salvation :-)
Why do doctors have to practice?
You'd think they'd have got it right by now
And here is Boeing's
)
And here is Boeing's contribution to the space race. Bet its noisy.
49 Years ago today
)
49 Years ago today ....
Apollo 1
Remembering Virgil I. "Gus" Grissom, Edward H. White II, and Roger B. Chaffee today.
https://en.wikipedia.org/wiki/Apollo_1
RE: 49 Years ago today
)
Yes. And Challenger on the 28th. RIP.
For aeroplanes at least I
)
For aeroplanes at least I subscribe to : if it is not Boeing then I'm not going !
Cheers, Mike.
I have made this letter longer than usual because I lack the time to make it shorter ...
... and my other CPU is a Ryzen 5950X :-) Blaise Pascal