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  #31  
Old 06-17-2017, 03:15 AM
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blackshire blackshire is offline
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Quote:
Originally Posted by luke strawwalker
I'd argue that Dragon may yet make CST-100 and Orion unnecessary... we shall see... (though I think NASA will continue with Orion so long as funding is forthcoming... regardless of it's "necessity" or not. The shuttle mafia lives on, now in the Orion/SLS mafia... LOL
I just lumped all of the capsules together, "against" the Dream Chaser lifting body. At the current flight rate (and even at a higher rate), I agree--Dragon--in whichever version is most appropriate to any given mission, cargo or manned--could handle most if not all foreseeable missions, even for higher-velocity re-entries from Venus or Mars.
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Originally Posted by luke strawwalker
True... I think that a lifting body type crew vehicle has some advantages... It will probably always have an edge in safety when it comes to landings compared to a ballistic capsule using a powered descent and landing (Dragon, eventually) even with parachute backups... there's a point where you're so low that parachutes do you absolutely no good but you're still quite high enough to pancake in... at least a winged/lifting body type vehicle can, so long as it maintains some sort of controlled glide, do a belly landing and have a chance to walk away from...

Later! OL J R
*Nods* Like the LEM (LM), descending vertical landers--whether in an atmosphere or not--all have a "dead man's zone" at low altitude, where there isn't sufficient time or altitude to do anything (except eject, *if* a vehicle is equipped with such devices). Even for sending cargo (and personnel) to Earth from the Moon (even by means of "lunatron" electromagnetic launchers), lifting body vehicles have been suggested because they could land at existing airfields (capsules could do this too of course, but they would have to land in cleared sea or [uninhabited] land areas).
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  #32  
Old 06-17-2017, 10:19 PM
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Jerry Irvine Jerry Irvine is offline
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Autonomous landing is now fully practical and a properly programmed system can perform corrections at 1000x the speed of a human.

X-47B autolands.

Scramjets autoland.

Drones autoland.

The technology is here now.
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  #33  
Old 06-18-2017, 12:10 AM
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Quote:
Originally Posted by Jerry Irvine
Autonomous landing is now fully practical and a properly programmed system can perform corrections at 1000x the speed of a human.

X-47B autolands.

Scramjets autoland.

Drones autoland.

The technology is here now.
That is true, but if a propulsive vertical-landing vehicle--such as the Super Draco thruster-equipped Dragon capsule--has a thruster re-start failure at low altitude, the autonomous landing system can't save an on-board crew (and if the altitude is too low for the vehicle's parachute to deploy, it won't help, either). The vehicle can, I think, compensate for a complete failure of one of the two Super Draco thrusters in one of the four "quad pods" located at 90 degree intervals around the capsule (one Super Draco under-performed during their pad abort test, and the capsule still landed safely), but anything worse--unless two thrusters happened to fail on opposite sides of the vehicle--would likely result in a "bad day."
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  #34  
Old 06-18-2017, 12:37 AM
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I do not concur that failure mode is likely or non-recoverable by some spinning.
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  #35  
Old 06-18-2017, 01:12 AM
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Quote:
Originally Posted by Jerry Irvine
I do not concur that failure mode is likely or non-recoverable by some spinning.
The two Super Draco thrusters in each pod are segregated from each other by armor, so that a catastrophic failure of one thruster will--hopefully--not affect the other one. Yes, spinning will "average-out" asymmetrical thrust vectors...*if* there is sufficient altitude (and thus time) to implement it. Some of SpaceX's earlier first stage landing failures occurred because of small component failures (and not even failures--one crashed because the Merlin engine's throttle responded too slowly, causing oscillations which the autopilot increased in its attempts to compensate). Yes, autonomous propulsive landing works, but it is a very fault-intolerant operation, in which small problems can cause a catastrophic prang--and very rapidly.
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http://www.lulu.com/product/cd/what...of-2%29/6122050
http://www.lulu.com/product/cd/what...of-2%29/6126511
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