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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.
There is a whitepaper linked from the company website:
http://escapedynamics.com/wp-c...
The short story
Microwave provides source of energy by targeting heat-absorbing material
Heat exchanger is used to heat and compress Hydrogen to 150 atmospheres
Hydrogen is fed to aerospike nozzle, which provide impulse thrust gt 750 seconds
Claims launcher will be able to provide 8% to 12% of total weight as cargo
Right now most of the website is pretty pictures and videos, time will tell
Wherever You Go, There You Are
Picking a launch vehicle more ar less at random, an Atlas V grosses 334,500 kg (737,400 lb). Now, at 80,000 ft (24,400 m) the lift of helium is 0.0375 kg/m^3. Even if the balloon and suspension massed nothing whatsoever, it would have to have a volume of 8.92 million cubic meters - 44.6 Hindenburgs in size. Counter-intuitively but still most impressively, a sphere 257 m (840 ft) in diameter would do it. But then again, such a balloon and suspension sufficient to lift 334,500 kg would be anything but zero mass. Most high altitude balloons lift only a few hundred kg of payload at most, which is why they do not suffer from scale problems like this.
Hydrogen has a tad more lift, but only a few percent, so the ludicrousness of the scale would not be appreciably affected, plus you'd have to be damn sure you wouldn't have to worry about static buildup in the extremely thin plastic film of the balloon.
Using either helium or hydrogen, you'd have to figure out how to inflate such a colossal structure in the open without it being wrecked by the tiniest zephyr.
Now, since the whole idea is to reduce that 334,500 kg gross weight by saving on fuel mass, it wouldn't be quite that bad, but clearly bad enough to be a spectacular non-starter.
I am thinking an air-breathing ramjet winged first stage would have more potential. It strikes me as spectacularly stupid to use rockets, with a gigantic oxidizer flow rate when the atmosphere is full of oxygen, all the way from zero meters; especially during the first few seconds when the fuel and oxidizer is getting sucked out faster than a cheap hooker could dream of, while the vehicle is barely moving at a snail's pace.
I'd like you to point out any launch site for orbital rockets that is anywhere even remotely close to tall buildings or even aircraft flights? The FAA routinely makes a pretty large exclusion zone around any launch activity. With the recent launch disasters from SpaceX and Orbital-ATK, I think such warnings should be well heeded even for ordinary Kerosene fueled rockets, much less something with an exotic propulsion system like this. It sure isn't going to be launched out of Central Park or any other urban center.
Besides, the CEO addressed this specific issue in an interview recorded a few months ago. Not only is the launch going to be far from cities, it will also need to happen in an arid region in part due to the microwave power being absorbed by water in the atmosphere. In other words, it is likely that this won't be launched from KSC in Florida either.