Let's Make Robots!


10 pts to whoever gets the title reference.

I was perusing all the amateur DIY near-space balloon flights that have been gaining popularity lately, and a thought hit me.

Would it be possible to have a two stage flight; first stage would be the balloon and payload reaching a certain altitude. The second stage, when this specific altitude is reached, a ROCKET is fired from within the payload, taking it further into space (hopefully reaching escape velocity.

Now I know this is most likely definitely not legal in the US to do, but would it even be POSSIBLE? If you think so, try to help me figure out how.

What size rocket would we need, how much fuel, what the weight would be, etc.

I'm imagining a miniature satellite; one with solar cells to capture sunlight and charge the electronics. Maybe something arduino powered with a light sensing circuit and servo to move the solar panels, along with a temperature sensor and perhaps even a small camera to record video and gps tracker.


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 it would be cool to try

It is possible but very difficult and has a lot of drawbacks - see Rockoon

You need to define "outer space". If you want to launch a satelite, you need to reach an orbit (at least LEO - Low Earth Orbit). This is for a hobbiest nearly impossible to realize, even the payload is very small - some nevertheless try it, see N prize

Crazy people like me wanted to reach even the moon - see Google Lunar X Prize

Feasible is to launch a rocket into space (defined as 100 km above the earth's surface). We're just trying that - see SS2S. Costs a lot of money though. I've spent around 25k USD to make it happen but we are far away to be succesful.

I read somewhere a balloon reaching the 100km mark to achieve LEO, but it popped shortly after reaching there.

Also I've looked into Rockoons a little bit last night; didn't get too far though.

Then there's this video: http://www.youtube.com/watch?v=P6GnP6qs2Bk

That's 90km. Wouldn't a rocket launching from that point be able to achieve greater heights?

there's a few group looking into this idea like this one. http://www.youtube.com/watch?v=WfJNNXTt85Q

but the answer is yes a rocket launched from a balloon at would go higher even a small rocket. the advantage of this idea is you at 90 km 99% of the atmosohere is behind you so there's a lot less friction to over come.

Many of the balloon based launches you have probably read about hit about 20 miles give or take. Markus' space definition is 60+ miles. I believe, don't know for sure, it would take a fair bit of propellent to cover that extra 40 miles. I don't believe a model rocket would do it. :)

It's not my space definition, it's the offical one, called Karman line.

One main problem to launch a rocket from a balloon is how to stabilize the rocket. At this height, the air density is so low, that fins make no sense anymore. You would need to spin stabilize the rocket.

I have done the math already, see here: http://letsmakerobots.com/files/2-D_vector_rocket_equations_with_air_drag.pdf



But the best rocket launch I've seen is a human sized rocket planned to hit outer space or atleast get a photo of the curvature of the earth and it hit 33km+ on the GPS. The exact height was not known as the parachute mechanism to get it back failed and the altimeter in it was in pieces. The size of the rocket was- 12 feet and about half a meter wide (dunno exacts, just a guess).


As to the launch being legal in US, I think you'll have to take permission from your local airport and army but you can do it. The show that I watched was shot in US and they took permission from both the authorities. The narrator said that they have to hurry with the launch as the army have to try a few missiles later on. 

The rocket was created in the backyard and they created all the parts themselves- from the parachute release mech to the body of the rocket and the fuel. Only thing that was created by someone else was the tail fins (as they didn't have cutting tools accurate enough to do it themselves).

I can do the math part for you but I'll have to refer to my old physics book before I can guarantee that. I'll post back about it, probably tomorrow (24 hours from now).