[AR] Re: re virgin orbit bankrupcy
- From: Henry Spencer <hspencer@xxxxxxxxxxxxx>
- To: arocket list <arocket@xxxxxxxxxxxxx>
- Date: Tue, 4 Apr 2023 13:08:24 -0400 (EDT)
On Tue, 4 Apr 2023, James Fackert wrote:
it is remarkable to me that it costs so damn much to keep a conventional
airliner flying when your paying flight rate is only a few per year.
I'm told that if you do the accounting carefully, the same is true of
cars: you have to be using one fairly intensively before the per-mile
costs dominate the per-year costs.
Maybe if you had a strap-on rocket hanger and could just rent one that
is in commercial service for a few days a year....
There aren't many large civilian aircraft that are certified even for
carrying external payloads, never mind for dropping them in flight. And
the details of the payload matter more than you might think -- even
dropping something in level flight at high subsonic speed is a tricky
business that requires careful testing. (Combat aircraft tend to spend a
significant part of their flight-test time on "stores separation" tests.)
The aerodynamic interactions are complicated, and it's easy for a dropped
payload to come back up and hit the aircraft, or do even freakier things.
(If I recall correctly, there have been cases of a payload dropped from
under a wing coming back up, passing upward *ahead* of the wing, and
gouging the *top* surface of the wing as it departs rearward.)
But orbital is all about velocity and not much about altitude. And wings
suck for that.
They're not *entirely* useless for that, because they can get you high
enough to permit higher nozzle expansion ratios and lower drag losses.
But the gain isn't large -- probably not enough to justify the costs
unless having a mobile "launch pad" confers some advantage that's
important to your business model.
Henry
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