"Brad Guth" wrote in message
...

On Sunday, April 20, 2014 5:41:25 PM UTC-7, Orval Fairbairn wrote:
In article ,

Brad Guth wrote:



On Saturday, April 19, 2014 8:34:35 PM UTC-7,
wrote:

"Behold the first test of the Falcon 9 Reusable rocket, launching and
then



smoothly landing in another location--an entire rocket going up and
landing

back



on Earth ready to be refilled and launched again. Unlike the
Grasshopper,

this

thing is huge!"





See:



http://sploid.gizmodo.com/awesome-vi...able-rocket-la

unchi-1564763284/+jesusdiaz



That's a terrific demonstration, as proof of accomplishing what other
space

agencies (including our NASA) still can not do.



A truly reusable fly-by-rocket is a serious game changer.



Wondering how much extra fuel was consumed.



Propellant usage would also be my top question -- followed by heat
damage to the base of the rocket.


1. If you use such a large mass fraction of propellant backing down to
landing, it loses all utility as a launch vehicle. It is nice to see
that Space-X can maintain enough control to back down to a powered
landing, but the utility question remains.


2. If the base gets so much heat and flame damage that it warps the
structure, the vehicle is only semi-reusable.

Perhaps a brief refueling in LEO before attempting its fly-by-rocket
landing. Of course we'd have to place a sufficient spare amount of HTP
plus a little something else of a hydrocarbon on orbit first.


You just made the problem much harder.

The fuel you need to get the 1st stage into orbit is what you would use for
landing.

And if you get it into orbit, it has a LOT more energy you have to lose
before landing.




--
Greg D. Moore http://greenmountainsoftware.wordpress.com/
CEO QuiCR: Quick, Crowdsourced Responses. http://www.quicr.net