Company Aims To Launch Spacecraft On Beams of Microwaves

MarkWhittington writes: The quest for cheap access to space, to make space travel as inexpensive as air travel, has eluded engineers, government policy makers, and business entrepreneurs from before the beginning of the space age. It has become axiomatic, almost to the point of being a cliché, that the true space age will not begin until launch costs come down significantly. Forbes reported about a company called Escape Dynamics that has a unique approach to the problem. The company proposes to launch payloads into low Earth orbit on beams of microwaves.

Comments

Good Idea, and a Possible Modification

[Anonymous Coward]

I have been reading about beamed propulsion for a while, this is an interesting concept. It is very nice to see progress is being made here. The advantage of beamed propulsion is that we can leave the power components on the ground (instead of needing to carry the energy as chemical propellant), which makes it far more efficient and can make spaceflight much more accessible (see rocket equation, most of the energy for a normal rocket is spend moving propellant and other things like propellant tanks up; we usually need to do things like multiple stages, etc. which add complexity and make resuability much harder). I think beamed propulsion is on the right track.

From the article, it seems that the hydrogen propellant (which is heated and blasted out) is used at all altitudes. This ship is then still described by the rocket equation, since it is effectively firing out hydrogen propellant at a given speed (the energy for the firing is external, but still, the propellant must be all on board at the beginning). Is it possible to instead use an air intake as long as feasible, switching to the hydrogen only at very high altitudes? This will greatly reduce the amount of hydrogen propellant needed, which will help a lot (again, refer to the rocket equation). I know this has been considered with usual spacecraft, there the situation is very different as chemical rocket spacecraft have to be using propellant always (even if not oxidizer in the air-breathing phase), here we can have a ship that can initially ascend as slowly as it wants while using air intake (since it is externally powered and isn't using hydrogen propellant yet), can accelerate fastest when air density is optimal (there is air for the intake, but not too much drag), and then switch to hydrogen at the end. Has this been considered?

Good luck Escape Dynamics, you have a very good project.

Re:Good Idea, and a Possible Modification

[ceoyoyo]

I'm sure they've thought of that. This isn't really a new idea, and the use of beamed power engines that switch from using atmosphere to carried fuel isn't new either (you can even use it in Kerbal Space Program with the right mods). The problem is that the molecular mass of air is quite high, and that reduces your specific impulse and thrust for a given power input. So to get the same thrust with air you'd need a bigger transmitter (probably much bigger). With rockets you usually need your highest thrust early on, because you're lifting more fuel, gravity is stronger, and you need to go more or less straight up. Later on you can get by with less thrust. Unfortunately, that's the opposite of what an air/fuel switching beamed power engine provides. You can get around that using a spaceplane design, but you still need to get up to speed and altitude while in range of your ground station... or build more ground stations.

They're probably looking at getting something working first, then building out the infrastructure to do more. That fits in with their plan to make a suborbital ship first: if you go basically straight up you're always in range of a single ground station, but you can't get into orbit.

Re:Poorly described

[weilawei]

So, you don't need to carry an oxidizer. If you wanted to run a turbopump to do the same in order to generate thrust, you'd need to react it with something. Neat idea, nice Isp, no idea if it's actually practical.

IANARS (I Am Not A Rocket Scientist).