what we're doing around hereLast night, Sir Charles W. Shults III, president of
Xenotech Research was on
Coast to Coast with George Noory. For the first hour of the show, he talked mostly about the nascent private space industry. He briefly outlined some of the major players in the industry, such as
Robert Bigelow,
Burt Rutan,
Sir Richard Branson,
Elon Musk,
Jeff Bezos,
John Carmack,
Peter Diamandis,
John Powell,
David Masten,
Michael Laine,
Bradley C. Edwards, and
Gene Meyers. In the course of discussing these individuals, he covered such topics as private space stations, private space launch, space tourism, the space elevator concept, space property rights, and the commercial development of space in general.
Sir Charles also mentioned some of the things that are going on at Xenotech. As the chief engineer for Xenotech Research, I have kept pretty quiet about the things that are going on here. Now that the cat is out of the bag, I feel free to talk about these things as well, and in more detail than Charles was able to go into on the show.
solar powerWe have spent the last couple of years working on a solar-thermal electrical generation system. This is a mechanical system (as opposed to photovoltaic panels, which are solid state) that focuses sunlight onto a boiler, which in turn drives a turbine that turns a generator - essentially a
heat engine. A working fluid travels through the system in a closed cycle, being heated in the boiler, transferring power to the turbine, then condensed in a radiator and going back into the boiler. We already have most of the components of our demonstrator model built and tested. Within the next three months we should have a working system that produces appreciable amounts of electricity.
Why go to all that trouble of making a mechanical system, when solar panels are readily available? Well, there are a couple of advantages to the mechanical system.
Solar panels are difficult to produce. The nature of photovoltaic cells requires that they be manufactured in a semiconductor plant. Such plants are expensive to set up and operate, so the cost of a photovoltaic panel is pretty high - a solar panel system for home use (like those available at
Home Depot) would save the owner money on the monthly electric bill, but it would take
decades for the savings to cover the initial cost of the system. With our system, the components could be made in any well-equipped machine shop, thus drastically lowering the initial costs and hence the price the customer pays.
Solar panels also are bad for the environment. This may seem counterintuitive at first (after all, they produce power from sunlight, don't they?), however, the production of solar panels is a process that requires the use of some very harsh chemicals such as arsenic. Our system requires no such use of harsh chemicals.
With solar panels, the amount of energy converted from light into electricity is proportional to the area of the panels. If you want to increase the amount of electricity produced, you have to increase the area of your solar panels, either by getting bigger panels or by adding more of them, so the cost per kilowatt remains fairly static - the more energy you produce, the more it costs, in pretty much a linear relationship. For our system, a single boiler, turbine and generator are used. To increase the amount of energy produced, one only needs to increase the surface area of the light collection system and the surface area of the heat radiators. The collectors and radiators are among the least expensive parts of our system, so as the energy production is increased, the cost per kilowatt actually drops (there are limits of course, as a single boiler cannot handle an infinite amount of sunlight).
The energy produced by solar panels is also proportional to the
energy conversion efficiency. Solar panels are not very efficient. For the types of panels available today, an energy conversion efficiency of 6 to 16% is typical for most commercially-available panels, with the multiple-junction research lab cells having an efficiency of up to 30% (at a cost of 100 times that of an 8% efficient cell). In contrast, our mechanical system is basically a heat engine; we estimate that we should be able to produce a system for home use that is up to 60% efficient (and for our future solar-thermal system for use in space, efficiencies of greater than 95% are possible). Also, as a photovoltaic panel heats up (say, from being exposed to direct sunlight for extended periods) its efficiency drops - but with our system, as the input heat increases the
efficiency rises.
Note that no semiconductor plant is powered by the solar cells that they themselves produce.
So, our solar-thermal electrical generation system will be lower cost (and the cost per kilowatt will drop as the scale is increased), will be better for the environment, and will be of a higher energy conversion efficiency than the best photovoltaic panels available commercially today.
There are of course drawbacks to our system. Being mechanical in nature, there are a small number of moving parts in our system (aside from the sun tracker, which could be included in a photovoltaic system as well) - there is a working fluid, a check valve, a turbine, a generator, and a transmission between the turbine and the generator. Moving parts can wear out over time. However, the parts are inexpensive to produce and will be easy to replace.
Solar panels face a similar drawback, in that they degrade in efficiency over time, with an expected working lifetime of around 40 years. If waste, inefficiencies, and energy used in production are taken into account, then solar panels are basically a break-even proposition over the course of their working lifetimes - the total savings on the electrical bill are pretty much equal to the (after rebate and tax incentive) total cost of the panels.
As a mechanical system, our solar generator experiences a drawback not shared with solar panels. All mechanical systems experience losses due to friction and acoustic losses (noise). The tests we have conducted so far indicate that the acoustic losses will occur mainly in the turbine, but that our turbine runs fairly quietly, producing less noise than a typical home air conditioner. The losses due to friction and noise are more than offset by the inherent efficiency of a heat engine, and as the input temperature is increased these losses represent a smaller and smaller portion of the total energy collected.
Our solar generator faces a problem that it has in common with photovoltaic cells - environmental damage. Such things as hail, earthquakes, hurricane-force winds and so on would damage both our system and solar panels. Because our system is much less expensive than solar panels, replacement costs are much lower.
All in all, we predict that our solar generator system will be much less expensive per kilowatt-hour than solar panels, paying for themselves many, many times over during the course of a similar working lifetime.
space launchRegular readers of this blog will know that I am a serious space geek. Well, so is everyone else here at Xenotech. This leads us to the major announcement that Charles made on the show last night: we are going to start making and launching rockets.
Our rockets will be small, two-stage affairs. The first stage will be a Hydrogen balloon that lifts the rocket to an altitude of 20 to 30 kilometers, getting us above the bulk of the atmosphere. At that altitude the rocket itself will fire. The initial altitude and low drag mean that for a given payload the rocket ends up being much smaller than one launched from the ground. We will most likely be releasing this balloon-rocket or
"Rockoon" combination from a boat off the East coast of Florida, beyond the 12-mile limit and well outside of airline flight paths. Each balloon will be equipped with large dihedral antennae and strobe lights to allow for long-distance visual and radar visibility.
Starting the rocket above the bulk of the atmosphere also means that the engine operates more efficiently, at nearly the
vacuum ISP rather than starting at the sea level ISP and transitioning to the vacuum ISP. This allows a large
expansion ratio in our engine, without suffering from flow separation effects.
I have been designing this rocket with a specific class of payload in mind:
CubeSats. These small satellites (sometimes called nanosatellites or picosatellites) are cubes with edges 10 centimeters long (total volume equal to one liter) and massing only one kilogram.
We will be building and testing these rockets (which we have dubbed "Fireflies" after the
TV series) in incremental stages. First, we will be doing some high-altitude balloon tests, with some instrument packages and a dummy mass. Next, we will test the various rocket component systems on the ground.
After these initial tests, we will construct a few rockets, send them up to our launch altitude, and fire them on suborbital trajectories. During these suborbital tests, the payloads will be business cards (or objects of similar size and mass to business cards).
Anyone can have their business card launched as part of these suborbital payloads for a price of US$10 per card.
When we are satisfied with our design, we will progress to the next stage of testing, orbital launch. The only difference between the suborbital tests and the orbital tests will be the trajectory of the rocket. The orbital launches will be to a low earth orbit, with an altitude of around 150 kilometers. The atmosphere at that altitude is very thin indeed, better than the hard vacuum produced in labs on earth, but there are still traces of atmosphere up there - enough that at 7 kilometers per second there would be sufficient friction to slowly bring the rocket down into the upper atmosphere over the span of a week or two, eventually burning it up. The payload for the initial orbital tests would again be business cards, which we will launch for a price of US$20 per card, along with some instrument packages to measure and transmit our telemetry.
Once those tests are complete, our launch operations will begin in earnest. We will be launching CubeSats into orbit, adjusting the size of our rockets slightly upward to attain a somewhat higher orbit.
Thus far, CubeSats have been launched as piggyback modules on large payloads. There have been three successful
CubeSat launches so far, with six, three, and one CubeSat launched piggyback along with larger payloads. Then on July 26, 2006, a DNEPR rocket carrying 14 CubeSats was
destroyed, along with the five large satellites that represented the primary payloads.
These lost CubeSats had had their launch postponed numerous times due to delays in the original primary payload,
EgyptSat-1. This is a hazard that so far has plagued all CubeSat launches, as all have been subject to the scheduling quirks of the main payloads on which they piggyback. And, as illustrated by the July 26 launch, a launch failure can result in the loss of a large number of CubeSats.
By making the CubeSat the primary (indeed, only) payload for our Firefly rockets, we can eliminate the schedule slip problem. The time period from delivery of the payload to our facility to the launch of the payload would be measured in days or weeks instead of months or years. And, since only one CubeSat would be on a given rocket, a launch failure would result in the loss of only one CubeSat
We will be offering the CubeSat launch service for a price in the neighborhood of US$10-20 thousand. This is comparable to the per-kilogram cost of launch on the Space Shuttle. At that price, colleges, universities, small businesses, and even high schools or private individuals could afford to build and launch their own CubeSats into orbit. With this large potential market, it would be possible for us to produce Firefly rockets on an assembly line. As a result, the performance and reliability of our rockets will continually improve. Also, the costs will continually decrease, as the development costs will be amortized over a large number of units, and as we develop greater efficiencies in our production processes.
We have further plans for the future which dovetail from the above plans, but for now we are going to concentrate on the solar power generators and the Firefly rockets. It's going to be fun here at Xenotech over the next couple of years.
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