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I want to build a small satilite and launch it into low space orbit. Nothing 'too fancy' a Raspberry Pi to power the systems, camera which'all transmit video and also a radio reviver and transmitter, maybe a small power bank to power the Pi and solar panels to charge that and gyro for stability in space instead of multiple thrusters. Hopefully it should last a few weeks before it burns up. The weight of the satilite would be under 5Kg. Also would radiation cause any short term harm to the electronics?

I was also thinking if I could first launch it with a weather balloon, have a small chemical rocket fire just before the weather balloon pops and then once it's reached micro gravity the rocket falls away and a canister of compressed air can accelerate it from there to a distance where should last a couple weeks.

I was also thinking about ion thrusters but they use a lot of electricity

Would this be possible at all?

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    $\begingroup$ You are vastly underestimating the amount of energy it takes to get stuff to orbital velocity-- your "small chemical rocket" needs to be pretty big. $\endgroup$ – antlersoft Sep 13 '16 at 18:12
  • $\begingroup$ What research have you done to find out what is possible and what it takes? What experience do you have of launching rockets? $\endgroup$ – sammy gerbil Sep 13 '16 at 23:48
  • $\begingroup$ as noted below, this question and its whopping 11 answers in SX SE has a lot of helpful data and discussions. $\endgroup$ – uhoh Sep 14 '16 at 3:56
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    $\begingroup$ For that matter we've had "launch from a balloon" questions on this site before, though no one bother going beyond quoting total delta-v requirements. $\endgroup$ – dmckee Sep 14 '16 at 16:11
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@antlersoft is right. You'd still need a powerful rocket to get moving fast enough to enter into orbit around the Earth, so probably not, unless it's a really really big balloon holding a really big rocket!

The term "microgravity" might be a bit misleading. The gravity up there is almost as strong as it is on the surface. The key is to go fast enough so that your "fall" towards earth actually ends up being an orbit. That's about 7.7 kilometers per second!!

If you are inside a spacecraft, in an orbit, moving at such an orbital velocity, you would also be in orbit around the earth. If you just look at how your body moves with respect to the spacecraft, you could call it "microgravity" (lots of people do, even astronauts) but maybe it should be called micro-acceleration with respect to the spacecraft.

Without the buoyancy that the balloon provides only while it's within the atmosphere, your rocket would accelerate towards earth. At only say 30km above the surface, you're only 0.5% farther from the center of the earth. Since the force behaves like $1/r^2$ that means gravity is only about 1% lower, so you'd accelerate towards Earth at roughly 8.8 $m/s^2$ instead of 9.8 at the surface, until you got low enough where the air is dense enough to start slowing you down.

So the hard part about getting to - and staying in space is not just the altitude, it's speeding up to that 7.7 kilometers per second that's the hard part.

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  • $\begingroup$ This is why the suborbital space-tourism people are really a bit of a con: it's just hugely easier to get 'into space' than it is to get int orbit. $\endgroup$ – tfb Sep 13 '16 at 18:50
  • $\begingroup$ @tfb I'm pretty sure people buying a suborbital ticket are perfectly happy that they are going to be gently returning to Earth in minutes or hours. I would be! Put them in orbit and tell them they have to stay there until a re-entry can be arranged, that they'll have to sit through 5 to 9 g's and cook for a few minutes, that they will likely start vomiting, their heads will fill with fluids and their eyeballs may change shape, and that they'll have to pay for it, and they're gonna be really unhappy! $\endgroup$ – uhoh Sep 13 '16 at 19:14
  • $\begingroup$ Oh yes, I'm sure it's what people want, I just object to the 'look, space travel is now cheap, those NASA people are just old fogeys' thing: suborbital is cheap, but it's also, well, suborbital. $\endgroup$ – tfb Sep 13 '16 at 19:40
  • $\begingroup$ Thanks I guess if I actually do this it'd be better using a very large rocket from the start. If I wanted to reach an altitude where the satilite will be there for a couple hours to a day how high would I need to go and if you could give a very rough estimate on how big the rocket would have to be (to carry around 5Kg) Thanks $\endgroup$ – J A Sep 13 '16 at 21:04
  • $\begingroup$ There is a similar question: Could it be possible to launch a rocket from a balloon? in space exploration stackexchange which has 11 answers! There is plenty of helpful discussion and data there. There are many serious difficulties mentioned that makes this much more difficult than you might first think, and the punch line is that you can avoid all of those problems by launching a slightly larger rocket from the surface in a standard way. The balloon is a headache and doesn't buy you much. $\endgroup$ – uhoh Sep 14 '16 at 3:56

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