space ship one makes the target

"Paul Sengupta"
wrote:

How do you measure altitude at 328k feet? Surely a standard
barometric device isn't going to work?

I set my Tivo to record the CNN coverage and Dick Rutan
mentioned that there were two tracking stations monitoring
the flight that could verify altitude to about "this far"
and he held his hands about 2 feet apart. I "think" he said
they were optical tracking stations. I presume there's
another form of on-board altimeter for measuring low
pressure or perhaps a radar altimeter.
Todd Pattist
(Remove DONTSPAMME from address to email reply.)
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Make a commitment to learn something from every flight.
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As I recall, Dick said something about Edwards and China Lake both tracking it
on radar. At best, that might give you a hundred meter accuracy.

A radar altimeter at 63 miles is a hell of a feat AND subject to severe angle
errors. I'd probably rely on GPS. As Dick indicated, two feet is about the
resolution you can get with a regular old GPS (unenhanced). That is my bet.

Jim


Todd Pattist
shared these priceless pearls of wisdom:

-I set my Tivo to record the CNN coverage and Dick Rutan
-mentioned that there were two tracking stations monitoring
-the flight that could verify altitude to about "this far"
-and he held his hands about 2 feet apart. I "think" he said
-they were optical tracking stations. I presume there's
-another form of on-board altimeter for measuring low
-pressure or perhaps a radar altimeter.


Jim Weir (A&P/IA, CFI, & other good alphabet soup)
VP Eng RST Pres. Cyberchapter EAA Tech. Counselor
http://www.rst-engr.com

Jim Weir wrote:

As I recall, Dick said something about Edwards and China Lake both tracking it
on radar. At best, that might give you a hundred meter accuracy.

Do you recall him holding his hands apart? I have to admit,
my attention was distracted right about then, so I can't
recall exactly what he said.

A radar altimeter at 63 miles is a hell of a feat AND subject to severe angle
errors.

I took a class in the early '70's on radar mapping of Venus
and the moon from ground based radar dishes. The basic
technique says you send out a spherical wave, and the
leading edge of your return wave is the closest point to
you. I don't have any info on radar altimeters, but
shouldn't they be reasonably self aligning if you get the
point below into your beam? I recognize that might be hard
for a craft in free-fall, but if it's not tumbling and the
beam width isn't too narrow ... of course, now you've got
power and detection problems at wide beam and 63 miles. :-)

I'd probably rely on GPS. As Dick indicated, two feet is about the
resolution you can get with a regular old GPS (unenhanced). That is my bet.

Makes sense. Cheaper too.

Todd Pattist
(Remove DONTSPAMME from address to email reply.)
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I'm sure if they were smart enough to figure out how to get up there,
they were also smart enough to figure out how far up they got.