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The first stage would be a high altitude balloon, which could reach 30km. Then start a rocket-candy from that high.

Without cargo, is it possible to reach the edge of space (Kármán line - 100km), or even Low Earth Orbit (160km)?

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    $\begingroup$ Do you want to reach space altitude or reach a stable orbit? The first is far, far easier than the second. $\endgroup$ – Philipp Aug 30 '15 at 20:34
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    $\begingroup$ It isn't just difficult, it's also dangerous. Most amateur rockets use small amounts of safe propellants of poor performance in safe, thick tanks; but if you want to reach space with anything reasonably sized, you need to use efficient propellants, which are dangerous, and trim the safety margins to reduce dry mass. Even if you can obtain these propellants legally, any failure (and there will be many!) usually results in an explosion, which - even if you are uninjured - means rebuilding the rocket from scratch. $\endgroup$ – SF. Mar 20 '17 at 2:20
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First of all, LEO isn't just reaching 160 km, it's reaching there and moving at a very fast speed. In fact, 160 km would be a really poor orbit, you really need something more like 350 km to get anything practical done.

As to your question, yes, it is theoretically possible. In fact, there have been a few amateur made rockets that have reached the Kármán line. The first happened May 17, 2004, by the Civilian Space eXploration Team (CSXT). This is the only known amateur rocket to make it past 100 km. For a more complete list, see HobbySpace.

Note that any team that has managed to make it that close usually has corporate sponsorships, and often has failures. It's really hard to get a rocket that high up.

As to making it to orbit, well, I don't think that's really possible given today's technology. It takes a lot of really smart guys working really hard to get a rocket to orbit, I don't think that's the kind of thing an amateur is going to do any time soon.

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While it's theoretically possible to home-build something capable of attaining the needed 9.3+ km/s, it's not something that the average person can pull off. You'd need to be exceptionally talented and extremely wealthy.

You'd also still need multiple flying stages, and a rather large rocket.

It's implausible, but not impossible.

Note that balloon launching of a solid fuel rocket to suborbital is directly comparable to the SpaceShip 1 and White Knight combo - Attaining orbital insertion would require a higher thrust to drag ratio - which can be attained by upscaling the rocket or adding some (parachute recoverable) SRB's.

Space Ship One is within the realm of what can be home-built. It's a carbon fiber shell, with a solid rocket/liquid oxidizer motor.... The project, including multiple aircraft designs, ran 25 million.

Converting to a balloon launch, you're looking at (potentially) about twice the ceiling of White Knight (which is about 16000 m). Assuming a safe drop of 1000m at launch, then climbout, there should be just barely enough delta-V to get it into a technical orbit... but you'd want some external thrust (parachute recovered) to put it into a useful orbit.

OII∞ is a low cost launch system (in development) that uses a high altitude balloon launch of up to 0.2 tonnes payload. It's also a multi-stage design - "2 donuts and a muffin" hung from a balloon and then launching from high altitude.

Refs:
Wikipedia Space Ship One
Wikipedia: Scaled Composites White Knight
TMRO: Toroids are doughnuts with OIIOO - Orbit 10.11 (Youtube)

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Yes! I discussed this with a person a few months ago, to include a few of the things mentioned here by others. We also discussed the balloon being solar powered.

The idea here is using a balloon to get as high as possible, might potentially negate a large portion of the fuel and bulk ones of the rocket, lowering cost and complexity, also (potentially, with a lot of friends in the right places, or a disregard for law) the rocket could launch far away from land, over an ocean.

The person I spoke with had (I think) an ingenious idea to recycle the balloon. I.E.: instead of it being a stage that separates, it folds up into a protected portion of the rocket, deployable upon Reentry or a failure to achieve orbit, as well as a possible energy source for a simple camera, or a comms system, potentially allowing the entire system to be used multiple times. This might however, count as cargo.

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    $\begingroup$ A balloon helps a bit getting to altitude, but not with the more important factor in going to space: you need lots of speed. $\endgroup$ – Hobbes Mar 20 '17 at 19:46
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    $\begingroup$ Folding the balloon is very difficult in the brief time you have. The balloon starts out as much larger than the rocket, then you have to deflate it, and use a winch to pull it into its storage compartment (without tearing), all before you can ignite the rocket engine (which would incinerate any part of the balloon left otuside). $\endgroup$ – Hobbes Mar 20 '17 at 19:48
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Although it stretches the definition of home made, JP Aerospace is a very small company run by John Powell. They started out attempting just that. Their current plan is to build an airship that is a "V" shaped airfoil. They plan to spin it out of the atmosphere using both thrust and lift to get to orbital velocities (with the initial workload handled by buoyancy).

Their plan is to trade time for efficiency, taking far longer to get up there than a rocket but using far less fuel.

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  • $\begingroup$ Thanks for adding this answer - I had not heard of JP Aerospace before, and their project looks really fascinating. $\endgroup$ – FKEinternet Aug 15 '17 at 5:51
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Your first question is a short description of the da Vinci Project that was an entrant in the X Prize contest.

Reaching orbit means getting your vehicle up to 9.3 kilometers per second. Without cargo, this still leaves you pushing the weight of the empty fuel tank and whatever guidance equipment you have.

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    $\begingroup$ -1 many homemade model rockets stage, so carrying the fuel tank may not be needed. $\endgroup$ – aramis Aug 30 '15 at 20:10

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