NASA’s been getting lots of press lately, and it’s got me thinking - what’s the smallest practical rocket that could reach low Earth orbit? I’ve looked around at some of the current offerings from the big aerospace companies, but they all have outrageously large payload lifting capacity. I’m thinking of something that could only lift a tiny “microsat,” or even just the spent rocket body itself and nothing more.
Also, I’m assuming cryogenic fuels (liquid hydrogen & oxygen) would have the best thrust-to-weight ratio, which is probably why nobody’s done this in their back yard before. Am I right about that?
When going from earth surface to low earth orbit, much of the energy is used to overcome air resistance. Air resistance scales up as square of size while amount of energy in the fuel tank scales as cube of size, so there’s a very strong economy of scale. (That is, double the size of the rocket and you carry 8 times more fuel, but air resistance is proportional to frontal area which only increases by a factor of 4.)
The Pegasus launcher seems to be a popular choice for small satellites such as the NASA Small Explorer missions. It can put about 400 kg into low earth orbit. Even smaller satellites exist, but they are either launched several at a time or as a “piggyback” payload on a much larger satellite.
The Pegasus is the best small engine/low cost vehicle I have heard of. Unless you can hitch a ride on another vehicle, I believe the cheapest way into space is the Pegasus.