Re: superhero space navigation

On 2008-04-07, Leonard Erickson <shadow@[EMAIL PROTECTED]
> wrote:
> Well, if nothing else, I'd like an idea as to what a normal handheld
> GPS unit would *do* on a trip to low orbit.

I suspect it would depend a lot on how much "sanity checking" the GPS
was designed with.  I wouldn't be surprised if most of them just
indicated an inability to determine position if they calculated an
altitude of a few hundred kilometres or more.


> I was rather surprised when I looked up the specs and discovered how
> high the GPS satellites are.

If they were in low orbit, almost all of them would be below the
horizon almost all the time.  Even at 5000 km altitude, the surface in
line-of-sight would be only about 20% vs ~40%, and about twice as many
satellites would be needed to ensure sufficient satellites in view
everywhere at all times.


> I'm suddenly picturing an old laptop running one of the spaceflight
> simulator programs. :-)

Yes, you can pick up an old Pentium laptop for pretty close to nothing
these days.  I've still got one that runs XEphem and Celestia.


> Call it 10 gees.

Definitely enough to ignore gravitational corrections.  Hmm, I have an
add-on script for Celestia that does a reasonable approximation of
moving the viewpoint under acceleration and gravity.  I'll see what it
looks like :-)


- Tim