GAGA-1
blog.jgc.org
blog.jgc.org
• Some GPS modules are crippled to not work very high and very fast so they can't be used on ballistic missiles.
• "Rise time" is an issue with balloons. You want to hurry up to your burst altitude to stay warm and not drift too far. I suppose aerodynamic shapes are out since it has to be able to expand hugely as it rises.
… ah, details.
You can do one or the other. Mach 1.5+ below 60,000 feet. Above 60,000 feet below Mach 1.5.
Not really sure how much protection that provides given that most commercial flights are below those speed and altitude thresholds.
A lot of GPS units wrongly interpret these limits as being 1000kts OR 60,000 ft, and so aren't suitable for high-altitude ballooning.
Of course, it's a silly restriction because if you've got enough money to build a ballistic missile, you've probably got enough to build your own GPS receiver (CU Spaceflight have built a software GPS receiver themselves).
I went to a balloon launch yesterday in Cambridge and the guys there were great. Very helpful and explained many little things that I don't have time to blog about.
http://blog.jgc.org/2010/07/ballasthalo-5-launch-afternoon-o...
Is it possible to send a balloon up and not have it burst. Just float around for a few days?
How do you calculate the balloon size And helium needed for a given payload?
The balloon manufacturers give lift information and then you simply fill the balloon and measure the lift.
I wonder what the actual formula is to calculate the correct balloon size? It seems like it might be some complicated differential equation. Here's why:
Say I want to lift 10 lbs. So I figure out I need X volume of helium. So I need a balloon weighing 1 lb to hold the helium. Now I need a balloon big enough to lift 11 lbs instead of 10, repeat, repeat.
If by “complicated differential equation” you mean either “surface area is approximately proportional to radius squared so this could be solved by 8th graders” or “just add 20% margin and it’ll probably work perfectly well”.
If it really must be exactly 5 meters/second (or whatever), the computation is still at about the level of a slightly-above-average 8th grader.
We use exotic alloys, explosive fuels and precision machining because we need to reduce weight to the structural limits. If we hadn't, space access would be cheaper and safer.
Sadly, Earth has just enough gravity to ruin our day.
But alas my math skills aren't up to the task of figuring out if it's viable. Someday I'll figure it out and you guys will see a blog post on it.
Or will polystyrene burst/disintegrate at such low pressures?
In any case, this sounds like a fantastic project, best of luck!
Here's some info: http://www.balloonfiesta.com/gas-balloons/gas-ballooning-faq...
but there is more to be found.