[AR] Re: Ozone layer was Re: Removing Coking Deposits
- From: Henry Spencer <hspencer@xxxxxxxxxxxxx>
- To: Arocket List <arocket@xxxxxxxxxxxxx>
- Date: Wed, 21 Sep 2016 00:56:51 -0400 (EDT)
On Tue, 20 Sep 2016, Peter Fairbrother wrote:
First of all, weather - it does seem evident that a WWJ can operate in
higher winds than a VTVL.
As per other postings, no, that's not evident, and indeed there is good
evidence that it's the other way 'round.
Second, landing site vs takeoff site. A WWJ can takeoff, fly backtrack on
jets before turning forward for main boost phase, and then glide to land at
the same site where it took off from - avoiding the transport problems and
time involved in landing several hundred miles away from its takeoff point. I
don't think a VTVL can do that.
Has it escaped your attention that SpaceX is *already* landing their VTVL
first stages at the takeoff site? And they're coming back from a fair way
downrange to do that, too. You don't need to backtrack in advance if you
can backtrack after separation instead.
Even if that was not possible, I don't think a VTVL can be refuelled,
recargoed, and take off from the spot where it landed.
It has been done.
True, for high-performance types, quite possibly a landing pad and a
launch stand will be sufficiently different that the vehicle needs to be
moved from the former to the latter before refueling and reloading. This
is not a hard or complicated or time-consuming operation. A tow tug --
the same kind you find around airports towing WWJs around -- goes out with
a set of wheel jacks, attaches them to the VTVL's feet, actuates the jacks
to lift the feet, and tows it where it needs to go. (Wheel jacks are a
standard commercial product, used even for moving wheeled vehicles when
it's not convenient to power them up; a VTVL might need a slightly custom
type, but that's not expensive.) It's an added complication, yes, but a
rather minor one.
Plus, if you want to move WWJs round on the earth for operational,
maintenance etc reasons, then you just fly them wherever you want them.
VTVLs would need a transporter.
VTVLs can be flown places where a WWJ can't land or take off. Whether
they would be allowed to is a different question... but then, the WWJ is
quite likely to be constrained by things like noise regulations too.
(It's going to be a lot louder than a 747, and horizontal takeoff means
flying low over surrounding areas.)
"This *isn't* just like an airplane." -- Jeff Greason.
No, but a WWJ is a lot more like an airplane...
Again you're appealing to faith rather than logic. No, it *isn't*
necessarily a lot more like an airplane -- that was precisely Jeff's
point. One WWJ is not just like another. When you start wanting
seriously high performance, you can easily find yourself operating in
areas of the trade space that are actually very poorly populated, with
little real past experience to go on.
(Historical example: the designers of the US SST discovered, to their
dismay, that although it had seemed like there was a lot of experience
with supersonic aircraft, very little of it was relevant! Brief sprints
to Mach 2.5+ had little in common with trying to cruise at such speeds,
and they were spending a lot of extra money and time pioneering new
technology in areas where they'd expected off-the-shelf solutions.)
Indeed, "very poorly populated" is probably an understatement. Mach 6 at
100km is beyond anything ever done with a WWJ. Even the X-15 couldn't do
that (either one, but not both simultaneously). It's not just possible
that there are big new problems lurking and much of the existing
experience is inapplicable -- it's almost inevitable.
A note on the Hustler - I heard that the reported 3x the cost of the B-52
high operating costs were calculated to include in-flight refuelling -
without which flight costs per hour were only about 30% higher than the B-52,
If they had been based closer to target, the operating costs would be much
less than the reported 3x the cost of the B-52.
Don't know the details of the cost accounting, but given the dismal
numbers reported for B-58 dispatch reliability and man-hours/flight-hour,
I'm skeptical. It might have been true on a day when everything was
working, but there were too few such days.
Henry
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