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Cheap Astronomy
2014-Jun-18, 01:08 PM
Hi,

I am genuinely interested in this, so sorry if I am getting a bit pedantic. I previously asked about the plausibility of the Dragon V2 landing procedure shown here: animation of landing: http://www.extremetech.com/extreme/183349-spacex-unveils-dragon-v2-the-worlds-first-commercial-manned-reusable-spaceship

cjameshuff kindly replied (http://cosmoquest.org/forum/showthread.php?151585-Question-about-Dragon-v2) with following calculation:

"As I recall, terminal velocity is around mach 0.6...only ~200 m/s. With an exhaust velocity of 3000 m/s and 30% of the thrust lost to the angled exhaust, a mass ratio of 1.1 does the job...about 9% of the vehicle mass being propellant".

This looked convincing at first glance, but hang on terminal velocity is in the order of 200-400 kilometres an hour. So, does a reverse thrust of 3000 m/s (later revised back to about 2300 m/s) still work??

A quick google search will show the Apollo capsules were plummeting at about 200 km/h AFTER the first drogue chute was deployed.

Remember the key thing is whether the Dragon v2 can plausibly hold enough propellant fuel to slow itself to a soft landing after aerobraking through the atmosphere down to terminal velocity. I think I am reasonably requesting a recount after being first advised the propellant would only need to be 12% of the capsule's mass. Extra kudos to an answer that also defines the altitude at which the rockets should fire in order to enable a soft landing with minimum fuel consumption.

Thanks!

Steve

Cheap Astronomy
2014-Jun-18, 01:18 PM
never mind

Swift
2014-Jun-18, 01:58 PM
Cheap Astronomy,

I have restored the original content of post # 1 of this thread and closed the thread.

It is perfectly acceptable, after you post a question, to say "never mind" (though an explanation is nice) and/or to ask that the thread be closed. But deleting the entire content of your post is unacceptable and is considered a very serious rule violation of our Revisionism Rule (Rule 11). Please do not do that again.