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Registered Member #2099
Joined: Wed Apr 29 2009, 12:22AM
Location: Los Altos, California
Posts: 1716
Cool! The same story was reported in the local paper here in California. Here is a similar project with similar technology:
But let's put this in perspective, when casually using the word Space, and comparing the cost of weather balloons with satellite technology.
These amateur balloon-cam pictures show a relatively dark sky and curved horizon (using wide-angle lens) from 20 or 30 km up. Reconnaissance airplanes have cruised that high. Re-entering satellites burn up at air densities 100x or 1000x lower.
To win the $10M Ansari X Prize, a one-man rocket twice coasted up to an altitude above 100 km. THAT could fairly be called "space" -- [edit] but the air is still too thick for a satellite to orbit the earth.
But reaching low-Earth orbital velocity requires 25 times as much energy per kg as merely climbing to 100 km altitude.
Registered Member #2431
Joined: Tue Oct 13 2009, 09:47PM
Location: Chico, CA. USA
Posts: 5639
klugesmith i am intrigued by your math can you explain briefly or include links to the math that descibes the kinetic energy reqiured at different alts like what Rutan achieved versus a satilite? plz ty,.
Registered Member #2099
Joined: Wed Apr 29 2009, 12:22AM
Location: Los Altos, California
Posts: 1716
Patrick wrote ...
klugesmith i am intrigued by your math can you explain briefly or include links to the math that descibes the kinetic energy reqiured at different alts like what Rutan achieved versus a satilite? plz ty,. -Patrick
simple. Sitting still at 100 km, about to fall back into the atmosphere, your potential energy is m * g * h -- about 1 megajoule per kilogram. The record altitude for a shell fired from a gun on the ground is 180 km (HARP / Gerry Bull).
Flying at 7800 meters per second, your kinetic energy is m * v^2 / 2 -- about 30 megajoules per kg. And you really should be at least 200 km above the ground, so there's another 2 MJ/kg.
[edit] I just figured the orbital energy of International Space Station to be about 1.14e13 joules (2.7 "kilotons"). Given the inefficiency of multi-stage rockets, the energy of rocket fuel burned to put it there must have been triple-digit kilotons.
Registered Member #160
Joined: Mon Feb 13 2006, 02:07AM
Location: Melbourne, Australia
Posts: 938
By no means is it "space" photography, but it does get it high enough to get the same feel from the photos. Tracking it would be a lot harder if you could get it up into low earth orbit, not to mention the fact that it would need heat shielding to come back down. This technology alone would need a specific weather to launch it so that you don't have to drive a thousand kms to retrieve it.
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Cheap high altitude photography.
