Testing shows using microwaves to propel a craft into space might work

Testing shows using microwaves to propel a craft into space might work

A team of researchers at Colorado based Escape Dynamics is reporting that initial tests indicate that it might really be possible to launch space-planes into space using microwaves sent from the ground, to allow for a single stage spacecraft. If the idea pans out, the cost savings for sending satellites (or perhaps humans) into orbit could be considerable.

Today's rockets are all based on the same idea, a multi-stage rocket is used, each part filled with propellant that pushes the rocket into as the propellant is burned. It is a really expensive way to go because the propellant is extremely heavy. ED's idea is to use beamed from the ground to heat hydrogen carried by the space-plane to push the craft into space, a much more efficient approach. They are reporting that testing done at their facility shows that the idea might be possible.

The testing involved building a thruster that operates on the ground and then testing to see how much thrust is generated—the team is reporting that they achieved a specific impulse of 500 seconds when using helium, and believe that when they switch to hydrogen that number will jump to 600 seconds—enough, they claim, to push a small craft into space.

With a real space plane, the microwaves would strike the heat shield on the bottom of the craft (both at liftoff and as it made its way into space) powering an electromagnetic motor which in turn would heat hydrogen as it was released from a tank—the result would be pushed through a nozzle, resulting in thrust. Once in orbit the plane would stay aloft long enough to deploy a satellite, then glide back down to Earth. The trick here is that the entire system does not have to be efficient, just the craft itself. The microwave array would be powered by electricity, generated by any number of means, down here on Earth.

There are of course still a number of hurdles to pass before the idea can be deemed viable—the microwave array would have to prove strong enough and able to maintain tracking of the craft as it climbed into space, likely the main ones. There might also be safety issues surrounding the firing of such a massive amount of microwaves into space. On the other hand, if the idea proves viable, it could mean sending satellites into orbit for a fraction of the cost of today's systems.


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Jul 22, 2015
the microwave array would have to prove strong enough and able to maintain tracking of the craft as it climbed into space, likely the main ones.

Tracking shouldn't be much of a problem. Some legal issues might be. I'm not sure if everybody is comfortable with individual nations operating something that is effectively a large microwave gun capable of delivering serious energies to LEO (and potentially sattelite-wrecking energies much further out)

I hope they address this by opting for an international launch port (should the idea pan out. Certainly sounds like its worth a shot)

Jul 22, 2015
This comment has been removed by a moderator.

Jul 22, 2015
Might want to take a look at this space propulsion technology.

http://arc.aiaa.o...008-5122


Jul 22, 2015
Never going to work. Some bird will fly into the path of the micro wave and get fried and then the "bird " people will have a field day

Jul 22, 2015
docile: The microwaves travel from ground to the vehicle. So they are, by definition, not confined inside the rocket engine.

Jul 22, 2015
Might want to take a look at this space propulsion technology.

http://arc.aiaa.o...008-5122


I doubt that a patent will be approved for an engine capable of achieving 99.9% light speed and needing 144 days to get to Mars. I mean, talk about taking the scenic route!

A constant acceleration of 1 G will get a ship to Mars in about two and a half days, and will get a ship to light speed in about a year. I foresee hybrid ion engines doing that in the foreseeable future. That is a far more realistic goal.

Jul 22, 2015
Using microwave would you need to wait for a low humidity day?

Jul 22, 2015
The trick here is that the entire system does not have to be efficient, just the craft itself. The microwave array would be powered by electricity, generated by any number of means, down here on Earth.


It has to be nearly perfectly efficient or it simply won't be possible. A single SRB of a Space Shuttle produced about 13.7 GW of power and there were two, plus the Shuttle's main engines.

If you get a low efficiency, like 20% power transfer, you need on the order of 100 GW electrical power in the array to launch pretty much anything all the way to orbit, and that's about a fifth of all the electric power generation in the entire USA.

When you turn the array on, several surrounding states would have to black out.


Jul 22, 2015
This approach make sense. Technically, the difficult part is not the microwave emitters because they do not need to be more efficient than existing technology, they can be as big and heavy as required, and they can put as many of them as needed. The real issue here is the EM engine, that is the really difficult device to make light and efficient.

Jul 22, 2015
It has to be nearly perfectly efficient or it simply won't be possible. A single SRB of a Space Shuttle produced about 13.7 GW of power and there were two, plus the Shuttle's main engines.


In fairness, the SRB has to lift its own fuel and a lot of other fuel and parasitic load. If you had just the spacecraft, with an ion rocket, and a microwave rectification system, the whole thing could require a lot less energy. So perhaps not 13 GW, but 1 GW would be practical.

Jul 22, 2015
You also can use a hybrid of the two designs and use the microwave to plasmize onboard fuel. If the fuel is completely stable unless vaporized with GW of power, the potential for fires and explosions in the event of a crash are greatly lessened.

Jul 23, 2015
The antennae shown in the video are certainly not emitting microwave lasers. They're emitting tight-beam microwaves, but not lasers. Which means a lot of the energy is not going to land on the target, no matter how good the tracking mechanisms. A lot of it is going to go right past the spacecraft, more and more as it becomes more distant from the launch point.

You could mitigate that by laying out a string of emitters along the flight path, instead of grouping them at the launch site in an array. It's still going to be sloppy.

LEO is crowded. I foresee a risk of damaging orbiting satellites.

Meh. My gut reaction is, this'll never fly.

Now when directed energy weapons are further along (lasers, specifically), maybe something could be engineered to capture the energy - missing very little of what's sent - and turn it into thrust. Maybe.

I don't think Elon Musk needs to be worried about it, though. If it's even feasible, it's a long way out.

Jul 23, 2015
As this concept still carries the Hydrogen: Air breathing rockets like SABRE have a better chance of delivering the required specific impulse with similarly low launch weight.

The EM engine they propose must be a new concept design, as ion engines like VASIMIR only work in a vacuum. While in the atmosphere, ionised air would be a better EM propellant than hydrogen.

Jul 23, 2015
Another possibility is fusion reactors. I realize that's a real long shot, but if Lockheed Martin's Skunk Works is able to hit their projections - which I seriously doubt, but I can't rule it out - we'll have 100 MW reactors in the approximate form factor of a semitrailer. We might be able to do something with that energy in a launch vehicle, perhaps ionize air, as EyeNStein is talking about. Though I suspect they'll need propellants anyway to get off the ground.

Small fusion reactors would also speed up transit times to other solar system destinations, though the question of obtaining mass to expend isn't trivial. Ice mines on the moon, perhaps, or captured asteroids with high volatiles content.

Jul 23, 2015
In fairness, the SRB has to lift its own fuel and a lot of other fuel and parasitic load.


The microwave rocket still has to carry reaction mass - fuel. It just doesn't need to generate its own power. The advantage is that all the reaction mass can be something like hydrogen gas, which achieves higher exhaust velocity and a more efficient transfer of energy than heavier molecules like CO2 or H2O. Less energy is lost to the exhaust stream.

That saves -some- of the starting mass, but not all of it.

Jul 23, 2015
Hmm.. they can deliver some really hot meals to the ISS with this.

Jul 23, 2015
nathj72 rote, "It should be possible to collimate the microwave beam and adjust the focal point of the beam to always be on the craft."

Sure. I only observed that the antennae shown in the video can't produce microwave lasers.

Though even if you defocus it, a laser in the 100 MW range landing its energy on the butt-end of a spacecraft is going to strip atoms off of any material we have available (unless reflective, which would not serve the purpose), and at a pretty good clip.

Frankly, I think we'll have to look at other approaches to reduce the cost of launches.

I like rail guns for launches, myself. Not for people, but for everything else. We could send up a half-ton cargo capsule once every 15 minutes with one of those running up the side of a mountain. But I'm guessing one couldn't be built for less than 20-30 billion dollars, roughly. We'd have to cancel some F-35s.

That would be a smart move, actually.

Jul 23, 2015
Power for the microwaves could be from earth base solar array near the launchpad. no reason to launch vertical either. Thrusters underneath the craft could point down as microwaves some from side to 'take off receptors under wings. Landing does not have to be a fiery stressful event either. Simply direct microwaves at bottom again and let reverse thrust force from beams slow the craft so temperature on underside stays within limits and deceleration forces stay low.

Alternatively, a nuclear or fusion powered Shawlor thruster could provide the take off power. Chinese know how to make THIS right now! They read Shawlor's work. WHY DO WE NOT DO THIS TOO??!

Jul 23, 2015
Laser power gives tighter beam, so need big honkin' space gun to launch it.. Screw complainers. Do like the Chinese do and just DO it like they are stealing a whole ocean right in the world's face and who is doing ANYTHING about that. It really IS a GOOD time to be an international scoundrel.

Jul 24, 2015
nathj72, of course you can focus noncoherent light, but that antennae field sure looks like fixed-focal-length emitters to my eye.

Coherence is the logical way to achieve a tight-enough beam over varying distances to deliver most of the energy to the target. But either way, if the focal point coincides with the receiving plate and delivers energy on the scale needed, any non-reflective material we have, even high-conductivity materials, would disintegrate. We're talking about something like a hundred or more megawatts delivered to a few square meters. Temperatures would surely reach into the millions of degrees.

It doesn't look practical from an engineering standpoint, no matter what emitter design you choose.

Contrast that with the Project Orion concept. With Orion, you give up on the idea of constraining mass and use an enormous big huge pusher plate that you *expect* will lose mass with every detonation. That's a pragmatic engineering task by comparison.

Jul 25, 2015
Laser power gives tighter beam, so need big honkin' space gun to launch it.. Screw complainers. Do like the Chinese do and just DO it like they are stealing a whole ocean right in the world's face and who is doing ANYTHING about that. It really IS a GOOD time to be an international scoundrel.


Gotta admire their engineering prowess. Building an island is a magnificent achievement. We should do that.
-------------------------------------
Now to the design of the receiver. You need something that converts efficiently or there is too much heat. How efficiently can you convert hundreds of megawatts?

Jul 25, 2015
Adam asked, "You need something that converts efficiently or there is too much heat. How efficiently can you convert hundreds of megawatts?"

Any materials we have available to use for the receiving plate will quickly vaporize.

If you want to get really, really clever, you'll line up a pulse laser and deliberately vaporize sacrificial material inside a tube, with the tube guiding the exhaust. But the pulses will have to be separated in time sufficient to permit the exhaust to get out of the way, or the next pulse will be scattered by it and you won't get thrust from the pulse. And the tube will have to be aligned correctly with the laser's beam. Get it slightly wrong and the spacecraft will be destroyed.

I honestly didn't think there were any spaceflight propulsion proposals more risky and technically difficult than Orion. Aiming a directed energy weapon - that's what this is, really - at a spacecraft is actually worse than Orion, and that's saying something.

Jul 25, 2015
I'm not sure if everybody is comfortable with individual nations operating something that is effectively a large microwave gun
How many nations now have large armies and nuclear arsenals able to inflict much more damage?
no reason to launch vertical either
Vertical has the advantage of reaching orbit the quickest with the least exposure to countermeasures.
It doesn't look practical from an engineering standpoint
What, another engineer wannabe?

"A team of researchers at Colorado based Escape Dynamics... Advisory Board which includes Professor Harry Atwater, the world's leading materials and renewable energy expert from Caltech, Dr. Peter Diamandis, Chairman and CEO of the X PRIZE foundation, Gonzalo Martinez, Director of Advanced Technology office at Autodesk, and Ingvar Petursson, SVP of Technology and Finance at Nintendo of America"

-If you dont mind I think I prefer their opinion over yours.

Jul 25, 2015
I like rail guns for launches, myself. Not for people
Why not for people?
http://www.nasa.g...nch.html

"A 240,000-horsepower linear motor converts 180 megawatts into an electromagnetic force that propels a scramjet carrying a spacecraft down a two-mile-long track. The craft accelerates from 0 to 1,100 mph (Mach 1.5) in under 60 seconds— fast, but at less than 3 Gs, safe for manned flight."
http://www.popsci...ft-orbit

Jul 25, 2015
The microwave rocket still has to carry reaction mass - fuel
Perhaps they cound combine it with this
https://en.wikipe...thruster

Jul 25, 2015
Adam asked, "You need something that converts efficiently or there is too much heat. How efficiently can you convert hundreds of megawatts?"

Any materials we have available to use for the receiving plate will quickly vaporize.
.


Are you certain the microwaves need to be received using a plate?

Jul 25, 2015
Might want to take a look at this space propulsion technology.

http://arc.aiaa.o...008-5122


I doubt that a patent will be approved for an engine capable of achieving 99.9% light speed and needing 144 days to get to Mars. I mean, talk about taking the scenic route!

A constant acceleration of 1 G will get a ship to Mars in about two and a half days, and will get a ship to light speed in about a year. I foresee hybrid ion engines doing that in the foreseeable future. That is a far more realistic goal.


Where are the expected filling stations needed for hybrid ion propulsion in deep space travel ?

Ion propulsion puts enough energy out to move a small feather.

NLS 74 days one way. This means less radiation to travelers.


Jul 25, 2015
NLS propulsion will work in deep space as proposed NOT launching a vehicle from Earth proposed
by the microwave concept.

Also the cargo from Earth to GEO or whatever will weight about as much as a Coors beer can.

Microwave and ION propulsion Not really useful for travel in the Solar system and planetary bodies.


Jul 25, 2015
Otto, the main reason I left out people was cost. A 3 gee rail gun capable of moving a capsule set up for sustaining humans in it will be much larger, much more expensive and much more technically challenging. Our main problem isn't getting people up and down, it's getting mass up where it's useful.

I'm pretty much in favor of relying heavily on robotics to build out an unmanned infrastructure that can begin delivering useful goodies to Earth and using robotics to build out a colonial infrastructure on the Moon, Mars and elsewhere. I don't like the idea of sending people to Mars just to leave footprints like we did with the Moon. But those are hostile places for human life; to actually live there, we have to dig and build on a pretty large scale. Send people later, not earlier, after existing there can be made comfortable and routine. Eventually we can get around to people-launching railguns, but we can do a tremendous lot with smaller ones and perfect the technology.

Jul 25, 2015
Adam asked, "Are you certain the microwaves need to be received using a plate?"

That's just a word I used for the spacecraft's energy-receiving surface. Call it anything you like. Whatever you use, when you put a hundred megawatts or more onto a few square meters, it's going to be converted into plasma.

Jul 26, 2015
Vertical has the advantage of reaching orbit the quickest with the least exposure to countermeasures.


You don't get to orbit by going straight up.

You simply fall back down, unless you manage to get right to the geostationary orbit 22,236 miles up.


Jul 26, 2015
nathj72 wrote, "If you solve this problem you will see that the outer plate will be about the same temperature as the inner side at 100MW. Once you get into the GW you start running into trouble."

Only if thermal resistance is pretty damned close to zero will the outer surface of the plate be close to the same temperature as the inner side of it. That's not a reasonable assumption.

But even if you do make that assumption, all you've done is move the materials problem to the other side of the plate. So now you get plasma there instead of outside. Can you say 'boom?'

I'm dubious that we can make materials stand up for very long to that much continuous energy input over a small surface (or an even smaller internal apparatus).

We use magnetic confinement to deal with high-temperature plasmas. But the magnets are massive and themselves power gluttons. That won't be a 'get out of jail free' card for this nutty launch concept.

Jul 26, 2015
"Vertical has the advantage of reaching orbit the quickest with the least exposure to countermeasures.

You don't get to orbit by going straight up"

-Duh.

Let me repeat - duh.

Vertical takeoff is safer militarily as it is the quickest way to orbit. But it requires more fuel.

Jul 26, 2015
But there are many other advantages to vertical takeoff.

"OTOH a rocket engine burns fuel so rapidly that it will run out in a few minutes. Consequently it must accelerate continuously. This means it will quickly exceed Mach 2, which would result in thermal stress and unacceptable drag losses in the sensible atmosphere. Moreover, horizontal takeoff of a rocket-propelled orbital launch booster would require that the wings support the fully fueled weight, which is easily ten times the empty weight. This would require very large wings which add both mass and drag.

With a rocket there is no choice; you must get out of the sensible atmosphere as quickly as possible. That is why most launch vehicles climb almost vertically to an altitude of at least 60 km before pitching over and accelerating horizontally. Even winged rockets like the X-15 and Pegasus quickly pull up into a near-vertical climb where the wings provide little or no lift."

Jul 26, 2015
Let me address your other puzzling deficit... an orbit requires an ORBITAL velocity.

"A geostationary orbit, geostationary Earth orbit or geosynchronous ... This equates to an orbital velocity of 3.07 km/s (1.91 mi/s) or an orbital period of 1,436 ....."

Jul 26, 2015
Adam asked, "Are you certain the microwaves need to be received using a plate?"

That's just a word I used for the spacecraft's energy-receiving surface. Call it anything you like. Whatever you use, when you put a hundred megawatts or more onto a few square meters, it's going to be converted into plasma.


I know you meant that. My question remains - are you certain you need a surface to collect the energy? Is it not possible to collect electromagnetic energy using some type of superconductive coil or field which would not involve it absorbing into matter? Or if a coil cant collect the energy directly then instead of absorbing the beam into a plate that would evaporate, absorb it into a plasma that cannot. Then collect the energy from the plasma using coil.

Jul 26, 2015
Adam, we don't have high-temperature superconductors. Anything at the ass-end of an ascending spacecraft is high-temperature. If you want to use superconducting materials, you'll have to haul along tons and tons of gear to cool them. It's a nonstarter.

Confining plasma is routine in laboratories. But it requires great big huge powerful magnets. There's no weight allowance on an ascending spacecraft for that, either.

If you want to work with plasmas, the only option I can see is the pulsed laser up the pipe approach. That will require very tight operating tolerances with a very high cost of missing the tolerances. I rule it as impossible to engineer to acceptable safety standards.

We really should be working on a rail gun.

Jul 26, 2015
nathj72 wrote, "The whole point is to heat the hydrogen which is on the other side of the plate to the point it can be used to propel the ship. Not to the point it becomes a plasma."

So, merely warmed-up hydrogen shoots out the back? The specific impulse you'd get isn't going to lift a box of tissues, while the propellant mass you'd have to carry would be enormous. Nor are you going to remove enough heat fast enough from the system to avoid destroying it.

"Take a look at the solar thermal towers for generating power. These use materials that can stand up to that much continuous energy for a very long time."

Solar thermal towers require coolant to move heat energy from the collector to the steam generator. The coolant keeps materials in a survivable regime. Rather obviously, you won't be tacking on any such coolant mechanisms to an ascending spacecraft. They're huge.

Jul 27, 2015
Never going to work. Some bird will fly into the path of the micro wave and get fried and then the "bird " people will have a field day


Or better, some guy who uses the alias execspec1 and the whole humanity will have a filed day ;)

Jul 27, 2015


I like rail guns for launches, myself. Not for people, but for everything else. We could send up a half-ton cargo capsule once every 15 minutes with one of those running up the side of a mountain. But I'm guessing one couldn't be built for less than 20-30 billion dollars, roughly. We'd have to cancel some F-35s.

That would be a smart move, actually.


Or we could open a Kickstarter ;)
I love the idea of the railgun too and hope to see one launching stuff intos space in my live.

Jul 27, 2015
I have a new definition for the word 'optimist' - a fellow who hopes that a Kickstarter campaign can raise 20 billion dollars for a worthy cause.

Alas, projects of that scale are too risky for private enterprise to bear. It's government or it's nothing.

I say we soak the rich in taxes and get on with doing things like this. In the US, over 75% of wealth is owned by 10% of the population, they pay less taxes per buck than the 90% who own less than 25% of the wealth, and it's getting worse every year. Wealth concentration leads to corruption that diverts government from doing useful infrastructure work like this. Enough, already.

Looking forward to seeing conservative heads explode over this recommendation. I'll just put on some popcorn to pop. There, all set. Bring it on, wingnuts.

Jul 27, 2015
nathj72, you can power a paper airplane with Coca-Cola and Mentos.

It doesn't scale up.

Jul 27, 2015
Anyone down-range is going to get their brains fried by the scattered microwaves which will bounce off water vapor in the atmosphere, and some (several percent) will bounce off the spacecraft itself.

Someone said it might take 100 GW worth of microwaves, well if 1% of that gets reflected, then that would be a GW of microwaves hitting the ground. People down range who look up at the thing will literally get their eyes fried...even at just 1% reflection.

Jul 27, 2015
nathj72, rather obviously, nobody has scaled up a Coca-Cola and Mentos rocket. And rather obviously, nobody has scaled up a microwave launch system, either.

The latter looks improbable to me; your arguments in favor amount to wishing away the engineering difficulties. You cite low-energy hydrogen propulsion for high-energy microwave capture, which makes no sense. You imagine using materials from solar tower collectors which survive in those towers only because of cooling on a scale unavailable to launch vehicles. The only evidence for microwave launch being feasible is a clever cartoon.

I might be wrong; I acknowledge it. What has never been done might, in the end, be accomplished, to my very great surprise. But it's far more probable, in my opinion, that this is a scam intended to separate stupid venture capitalists from their money.

Returners, in what universe is 1% of 100 MW equal to a GW? You forgot your meds.

Aug 04, 2015
I wonder at what power density the microwave energy will heat the air enough to ionize it which would cause a faster absorption and eventually just reflect the energy back at the array.

The power density of air brakedown at 92 GHz is above 500 MW/m2 through the entire atmosphere. The launch vehicle Escape Dynamics is developing requires power density on the vehicle around 10-20 MW/m2.

Aug 06, 2015
@Eikka You need to get to the lagrange point.


No you don't. That hasn't got anything to do with it. You have a certain "orbital" velocity simply by standing still on the ground, because the earth is spinning. If you manage to go straight up high enough it will be sufficient to maintain an orbit, and if you go higher still it will be sufficient for escape velocity, but any lower and you will fall back down.


Aug 08, 2015
Interesting concept, but lots of issues to be solved. For cargo, I still think a linear mass accelerator would be the best/cheapest route. Build one up the side of a mountain facing East to gain momentum and use a partially evacuated tube to avoid atmospheric friction as much as possible, exiting the tube above 3km. Since the craft themselves would be inexpensive, containing steering and guidance only, they could be disposable - or used in on-orbit construction projects as raw material.

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