The National Space Society held a press event at the National Press Club today in conjunction with the Discovery Channel to announce the results of power beaming tests carried out in the Hawaiian Islands earlier this year, between January and April. The testing was funded and filmed by the Discovery Channel as an episode of an eight part ‘Discovery Project Earth’ series and should be airing tonight in the US.
The briefing was given by John C. Mankins, COO of Managed Energy Technologies LLC who actually built and carried out the tests and shared the podium with Mark Hopkins, Senior Vice President of the National Space Society. The house was packed, standing room only with more people in the hallway,.according to an attendee whom I interviewed.
John Mankins and his crew built a portable and modular energy transmission system for under a million dollars. This was not just a technological feasiblity study. We have known for decades that it is possible to transmit power via microwaves over long distances. What the Mankins test showed was how it can be done in a real world situation. They had to work around bureaucratic approvals which limited the total power; they had to deal with tribal religious requirements that nothing be left on the sacred volcano over night and they had to build equipment that could be carried to a site, plugged together, aimed and turned on.
They succeeded. 1 watt of power was beamed from a portable antenna on Maui to a small receiving antenna on Hawaii, 147 kilometers away.
The equipment was not engineered for efficiency nor high power, both of which are possible. Mankins and the Discovery Channel team have succeeded in what they set out to do: they have an iconic real world demonstration that shows the key technology behind Geosynchronous Solar Power Satellites works.
Do the orbital stations need to be geosync? Surely if they were in low orbit there would be less of a problem with beam spread. Although, it would then be necessary to have a series of ground stations with high switching speeds as the satellites orbit.
Secondly, if the satellites are in geosync orbit, the beam would have to be highly focused and high energy at departure, could this fry satellites in slightly lower orbits as they enter the beam?
The very first tests will almost certainly be low orbit. We might see something of that nature come out of the USAF Academy if Col Coyote gets his way. That will be very low energy but proof of the concept from space.
When we start building the real thing they will be gigantic structures with acre after acre of collecting area and capital values on the order of a similarly rated power plant on the ground, ie multiple billions even after we get up the learning curve.
Since they will be major bits of infrastructure they are best placed at GSO where they can constantly beam to fixed and very large rectenna’s on the ground.
Additionally, any LEO satellite is in shadow half the time unless you go sun-synch, and that is not a very useful orbit for delivery of base load power.
Which is of course one the main points: the solar power sat concept is aimed at eventual delivery of base load power. For that you need a nice steady static system.
Even at GEO you do get a few minutes a year of shadow but it is predictable and they are not very long. It will only occur when the line of intersection of the Earth’s equator with the plane of the Earth’s orbit around the sun is pointed at the sun and the powersat is anti-sunward of the Earth.
As to satellites… orbits that are sub-GSO are not really used for anything, and even if they were, the time it spends in beam would not be very long. The since the ground end will be dispersed to cover acres with an energy levels around that of the sunlight falling on that area, the beam width near the powersat should not take very long to cross. There might well be emergency cutouts if it looks like it would be a problem. I’d count that as a minor engineering issue.
We’re moving through the steps now to retire technical risks. Once that is done, it is going to be up to the power industry to run with it.
Am I the only one that hears “Massive Space-Borne flamethrower-type weapons system” when they say beaming power from orbit to earth?
Even if we’re OK with our own governments having this capability, how do we tell the Chinese, Russians, and etc. “Sorry, you can’t be trusted.”?
A discussion of why it would make a p**s poor weapon would take a lot more time than I have and space than the comment section is made for, but just for starties, it is a gigantic (measured in acres or even square miles of solar collecting area) and incredibly flimsy (by earth based standards) target that is in an absolutely known and predictable orbit and does not have much, if any, capability of moving.itself.
The military guys would prefer everyone has one, because then you have a, shall I dare say, ‘balance of power’? “If you try to take out ours we probably can’t stop you… but you can’t stop us from then taking out your base line power either”
We will have powerful beams from space, but they won’t come from easily targetable and mostly indefensible targets like this. They’ll be in mobile craft and use use fusion power for energy. if they are orbital fortresses, they’ll be big balls of rock and dirt with self contained systems underneath. They will not have square miles of ‘here I am, hit me and I’m dead’ solar panels.
Dale, thanks for sharing. Helps keep the rest of us aware of progress in the real world.
The big message is that the solution to our energy woes is through advances in technology. Unfortunately, our political class gets all hung up on 17th century solutions (windmills) or actual scams (ethanol). That’s not the way to stimulate technological advances. We need to find a way to encourage human beings to explore lots & lots of possible dead ends — because one or two of them may just work.
I don’t want to seem overcritical – this is a very interesting development, but not, I think, for the application envisaged.
We already have more than enough solar energy available down at ground level – the issue is cost. It currently costs about 20 times as much as coal if I remember correctly. So the question is not whether you can do it, but whether you can do it cheaper. Does doing it in space make solar panels cheaper?
Now, about 40% of sunlight is reflected or absorbed before you get to ground level, and obviously it’s dark at night, so you lose another factor of 2 or 4, depending on how you account for the sun’s elevation. So sunlight is, perhaps, ten times more plentiful in space. That still wouldn’t be enough to make it economic today, but with more development it sounds close.
But on the other hand, there are going to be transmission losses. There are going to be conversion inefficiencies. You’ve still got to get the electricity from the ground station to the users. And, probably most significant of all, you’ve got to get the collectors up into space, and do maintenance on them. You know how much it costs per kilogram to put stuff into orbit? If you’ve fixed that little problem, you’ve got a lot more applications than space power.
Maybe you could make them on the moon?
However, for beaming energy across the surface to remote locations far from the grid, I can see definite applications. What would be really interesting is if you could bounce it off an aircraft, (that could be unmanned and hovering indefinitely in place,) and solve the line-of-sight problem.
“Additionally, any LEO satellite is in shadow half the time unless you go sun-synch, and that is not a very useful orbit for delivery of base load power.”
I don’t quite see how sun-synch solves anything. Yes, one equator crossing is at a fixed local time in daylight (the spooks reportedly like 10 AM), but the other equator crossing is always at the corresponding time at night.
I guess you could do a 6 AM/6 PM orbit. I don’t know whether being always effectively at dawn/dusk would be a problem with looking past the atmosphere (probably not). It would make the orbital velocity be always edge-on to the panels, which would help with drag.
BladeDoc wrote, “Am I the only one that hears “Massive Space-Borne flamethrower-type weapons system” when they say beaming power from orbit to earth?”
Dale pointed out good a political reason why this would make a poor weapon. A well-known technical reason is that microwave beams can’t be focused to a diameter less than that of the transmitter aperture (which will have to be quite large to keep beam-spread down between the orbital transmitter and the receiving antenna on Earth), and so the power density in the beam will be low. Typically, rather less than the intensity of sunlight. Now satellites flying through even a low-intensity microwave field may need to be specially engineered to avoid surface currents developing on their external parts; however, this should be a straightforward extension of what spacecraft engineers already do to protect satellites against natural (solar-induced) surface charging effects.
Pa Annoyed wrote, “We already have more than enough solar energy available down at ground level – the issue is cost.”
Yes, there’s plenty of ability to collect solar energy on Earth and convert it to electricity. However, the issue is not cost—it’s energy storage. While solar cells are fairly expensive, all known technologies for storing electricity are *really* expensive. You need batteries (or equivalent) to store power for the times when your solar cells aren’t making power—which is most of the time. (Plus you need lots of extra solar cells to produce enough excess energy to charge the batteries, as well as run your electrical loads at the same time.) The advantage of space-based solar power, over ground-based solar power, is that it can generate power continuously (at least, for satellites placed in GEO), thus removing (or at least greatly reducing) the need for batteries.
Bruce Hoult wrote, “I guess you could do a 6 AM/6 PM orbit. I don’t know whether being always effectively at dawn/dusk would be a problem with looking past the atmosphere (probably not).”
The dawn/dusk sun-synch orbit is one of my favorites; I’ve put one satellite into that orbit (MOST, which is still chugging away 5 years on), and designed another mission (NEOSSat) which will also be going into that orbit fairly soon. No problem “seeing past” Earth’s atmosphere, as long as you’re at a decent altitude (typically I’d put a solar power satellite well above 700 km). Good point about the solar arrays being edge-on to the atmosphere there. From that altitude, the satellite can be seen from the ground for passes within +/- 100 minutes of 6 AM and 6 PM—thus could provide power only from about 4:30 AM to 7:30 AM, and ditto for PM; as Dale points, out doesn’t really solve the baseload power problem.
Kieren: Thanks for jumping in. I have been buried in business taxes for the last week and did not have enough neurons left over to try to make some of this more comprehensible to the non-aerospace public.
Since we do have a couple ‘serious dudes’ on this discussion, I am going to throw out the almost never mentioned topic which is in my mind the biggest unretired risk there is in these things.
The collecting area of a solar power satellite, seen from a large distance will be somewhat like a sheet of paper. The thickness, compared to the length and width will be miniscule.
This means the structure will be a bit like a two-dimensional suspension bridge except it has no fixed points unless you call the central transmission tower by that name.
Many I have talked to just imagine this thing floating benignly in space. It is zero gravity after all, right?
I am afraid it is mind bendingly more complex than that. The structure is going to have resonant frequencies. It is going to be creaking and groaning (if you put a mike to the structure) constantly. There are all sorts of differential forces working on it that I can think of off the top of my head and I am even more worried about the ones I haven’t imagined.
First. there is a small gravity gradient across the structure reflecting the position of each point on the structure in the three-body Earth-Moon-Sun gravity field. As it orbits the earth, this field is constantly changing.
Second. There is a flux of solar wind against the structure. How large is flux gradient over the surface? I do not know if we even know whether there are significant differences in flux over a distance of a few tens to hundreds of meters.
Third. There are eclipses of the structure. What is the effect of a sudden cooling from a sun facing temperature to a temperature controlled by the black body temperature of the Earth? And then a few minutes later again? Especially since ingress and egress of leading and trailing edges of the structure are different enough to set up temperature differentials which could cause both compression waves and shear waves?
Fourth. Is the light pressure from the sun always uniform in both time and space? If there is any variation in either, it will cause small vibrations.
That is probably enough for starters. If under any circumstances any of these forces or combination of them reinforce, we could end up with a 21st century version of ‘Galloping Gertie’.
There will probably be a need for some sort of active cancellation, but even there one runs into problems. A cancellation feedback force, if it comes after a time delay, can push the nodes onto the right half of the plane (for those who took control theory courses long long ago like I did) and that is real bad news. On your stereo it just means a screech. On a structure it means self destruction.
None of this is show-stopping. It is just a new level of civil and mechanical engineering, some of which may have to be learned the hard way.
That’s why I do not think we are going to wake up one day and go out and build a 1GW solar power station… we’re going to work our way up from smaller ones and learn the engineering the way we always have. The hard way.
Since I was listing things which could cause dynamic effects on the structure, I might as well add:
* Shock from hard dock and undocking with spacecraft
* Effects of astronauts moving around on the structure for repairs,
construction, etc.
* Accidental plume impingement
* Shock propagation from micro or larger meteor strikes.
Has anyone else here read any books about Edgar Cayce, and his description of a high-tech Atlantis? He talked about how they eventually ended up with beamed power! And how one of the destructions of Atlantis was caused by energy being sent into the Earth. Whilst Atlantis is a four-letter word in Science, we keep turning up anomalies (the ‘beachrock’ road in Bimini is now thought to be a constructed highway- the scientist who reported it was natural did a sloppy job.)
I hope they have good safety precautions. I’d hate Hawa’ii to disappear!