[FPSPACE] Orbital versus sub-orbital spaceflight -- how MUCH harder?

[robot at esper.com]

The "first cosmic velocity" is 7900 m/sec, not 7200.

Having done a few of these back o' the envelope exercises myself, I
concur with the portion of the analysis concerning the greater impact
of air drag on suborbital vehicles than orbital. I usually use a drag
budget of a mile per second or so, similar for gravity loss. Even my
back o' the envelope ABM concept developed well over 7 km/sec to do
its job.

Robert

Robert G Kennedy III, PE
www.ultimax.com

---- Original Message ----
>Date: Sun, 29 Apr 2007 10:35:17 -0500
>From: "Jim Oberg" <joberg at houston.rr.com>
[snip]
>Orbital versus sub-orbital spaceflight -- how MUCH harder?
>
[snip]
>Real world orbital launch vehicles typically need to deliver
>8500-10000 m/s of delta-V (compared to the orbital velocity of
>~7200m/s) to reach a low earth orbit. 
 ^^^^^^^^
>Somewhere between 1300 and 2800
>m/s of delta-V ends up getting eaten up by drag and gravity losses.