I just came back from hospital (a new type of flu virus in Poland, that I wasn't resistant off, and it got me paralysed so badly that I almost sufficated).
I see lot's of posts came-up. I don't know where do you peeple get those numbers from...please use links and quotes, becouse I spend lot's of time confirming what you have said and finding-out that many things are wrong.
Like:
The effect on a human with a 2000 watt laser beam would be instantaneous and brutal. Safely capturing said beam at the other end would also be a challenge, even at 50% efficiency that is still a lot of heat the laser collector has to dissipate.
LaserMotive developed the diode-laser beam system that kept the Pelican aloft. Near-infrared light from the equivalent of 250,000 laser pointers were focused and sent up to shine onto the quadrocopter's photovoltaic array, using a system of lenses and mirrors in the back of a delivery truck. The laser system served as a "wireless extension cord" for the Pelican, Nugent said. But the copter also had a battery capable of keeping the rotors running for a few minutes, just in case something went wrong with the 2.5-kilowatt laser.
Jordin Kare, another one of LaserMotive's co-founders and a pioneer in the field of laser propulsion, said the laser generated enough radiation to heat up your hand if you stuck it in the beam, but nowhere near enough to blast a hole in it. "We've actually cooked hot dogs with that laser, and it takes about four or five minutes," Kare told me. "Not exactly a death ray."
http://cosmiclog.msnbc.msn.com/_news/2010/10/28/5368938-copter-sets-a-laser-powered-recordAs an aside, cooking a hot dog with a laser is not really much different than cooking it with an electric grill. The power level is comparable, the wavelength is a bit different (and so you want to wear protective goggles), and the toaster is just a bit more expensive, but otherwise there’s an on-off switch, a power dial, a bottle of Haynes, a bottle of Dijon, and squeeshy hot dog buns. There was no beer, even for guests.
http://www.spaceelevatorgames.org/category/team-specific/--------------------------------------------------------------------
The problem is the collector will be about as heavy as a small RSG in many cases.
Stirling radioisotope generator (SRG)Power:
Thus each SRG will utilise two Stirling converter units with about 500 watts
of thermal power supplied by two GPHS units and will deliver 100-120 watts of electric power.
http://en.wikipedia.org/wiki/Stirling_radioisotope_generatorMass:
34 kg http://newfrontiers.larc.nasa.gov/PDF_FILES/09_NF_PPC_Schmidt.pdfAdvanced Stirling Radioisotope Generator (ASRG)# Nominal power : 140 W
# Mass > 30 kg
http://en.wikipedia.org/wiki/Advanced_Stirling_Radioisotope_GeneratorLaserMotive climbing devicePower:
With more than 1000 Watts transferred (peak) and roughly a horse power on average, their climber is clearly superbly designed, and is capable of achieving this speed.
http://www.spaceelevatorgames.org/Mass (with batteries, motors and other parts):
At the 2009 Challenge, on November 6, 2009, LaserMotive successfully used lasers to drive a 4.8 kg (11 lb) device up a 900 m (2,950 ft) cable suspended from a helicopter.
http://en.wikipedia.org/wiki/LaserMotive--------------------------------------------------------------------
The "Small" collector still needs a way to dissipate the heat from the conversion inefficiency and the heat sinks and the like will add to the weight significantly.
The next test is the Climber Melt Test.
If you recall, this is the test where the climber is illuminated at 100% power for the full climb duration (plus margin), and we confirm that it can take the heat.
We also look at the amount of power produced by the climber, to confirm that it is sufficient to move it up the cable at competitive speeds.
Moving to photovoltaics, NSS settled on a PV technology called TPV – Thermal Photovoltaics. These cells are optimized to operate with thermal IR radiation (longer wavelength than TRUMPF’s NIR 1030 nm beam) but have acceptable performance at this wavelength as well. More importantly, these cells can work with high light intensities, which means that you can get more power out of a smaller (and thus lighter) array, if only you can get the transfer the excess heat away from the cells.
What this calls for is a good heat exchanger – and this turned out to be the highlight of the day.
Check out the images of the climber. The TPV cells are completely immersed in acetone (4 ounces) which is vigorously boiling away under the heat load of the beam, completely evaporating every 15 seconds – only to be continuously captured by the bags and dripped back down onto the cells.
Acetone was chosen since it has the lowest boiling temperature, and so will be most effective as the working fluid. This is a basically a cooling tower (or heat pipe) – something that was used by Centaurus Aerospace back in the 2005 games – using water in vacuum, in their case. The acetone solution is a lot lighter, and yes – more flammable.
We’ve looked into this issue, and we recognize that there are failure modes under which the system can develop a leak, but we feel that a) the acetone is far removed from any spark sources, b) there is only a small amount of acetone in the system, and c) there is no place for leaking acetone to accumulate, and so the consequences of an acetone leak are acceptable. We will also be monitoring the temperature of the PV receiver, and if we see it rising above the boiling point of acetone, we will know that the acetone is depleted and the climb is over.
So after observing the climber operating under full laser power, and with some modifications required, we’ve decided to ok the design, and allow NSS to catch up and participate in this year’s challenge.
http://www.spaceelevatorgames.org/[4 ounces = 113 grams]
BTW: the same radiation techniqe is used in space.
On October 28, 2010, Lasermotive set a flight endurance record at the Future of Flight Center by powering a quadcopter UAV for more then 12 hours using laser propulsion.
http://en.wikipedia.org/wiki/LaserMotive and
the Ascending Technologies Pelican quadrocopter and the LaserMotive power system were both capable of continuing indefinitely
http://lasermotive.com/news/blog/--------------------------------------------------------------------
The climber was able to use the laser energy as it was a rather small robot which would have suffered a rather sizeable mass fraction for the batteries used for motive power.
In the test the team launched the Pelican using its five-minute-duration
battery and then turned on the laser power beam to provide continuous energy.
“It just sat there, 35 or 40 feet in the air, hovering constantly for
almost 12 and a half hours.”
The Pelican’s battery was recharged in flight, and near the end of
the test the craft flew over the spectators and landed under battery
power.
http://lasermotive.com/wp-content/uploads/2010/04/AUVSI-LaserMotiveUS0211.pdf--------------------------------------------------------------------
The climber was able to use the laser energy as it was a rather small robot which would have suffered a rather sizeable mass fraction for the batteries used for motive power. The motors for the climber could be relatively small, as they didn't need to provide a lot of motive force for the climber to defeat gravity.
A remote mining / smelting facility, on the other hand, would require massive amounts of energy, on the order of tens or hundreds of kilowatts if smelting is occuring.
I reely don't understand what's your point here....Wat's are Wat's, no mather what uses them. If a robot gained 1000 Wats, than it can use 1000 Wats, no mather if it has batteries or low-/highpowered engines.
Why do you compare a mini-climbing robot with a big fabric on Earth? It's the energy source that we'r discussing.
If a mining-plant used a 10.000 kW of energy, you could deliver it in several ways:
1) send to Mars and plant in-situ a
SECOND thorium reactor...
2) send to Mars and plant in-situ
100 square meters of PORTABLE PVP's. (efficiency 100 W/m^2 --->
http://solarwall.com/en/products/solarwall-pvt.php)
3) send to Mars and plant in-situ a
71 Advanced Stirling Radioisotope Generator (ASRG)
4) send lot's of methane-oxygen generators to Mars and produce and use in-situ tens-of-tons of oxygen and methane
and finally the
BEST solution, becouse it's the most economical one:
5) send one thorium reactor in the main base. Use wireless-laser energy transfer to send excess energy it produces to locations that currently needs energy.
Those locations need only a few T/PV (thermal photo-voltanics) cells that receive power.
Those locations (like: mining facility) stores the excess power that they doesn't needs at the time. Unneded power is shut-down from the main base or stored inside regular lithium-batteries or high-cappacity batteries like
Refualable Water Cells inside the mining facility thats stores unneded power. That power can then be used when you need more power, for the time when you do some super-energy-consuming processes. If the mining facility needs more power, the base sends more power inside the laser-beem. It's also required to understand that "not evertything will be done all-the-time"...that means that if you'r refining resources, you only refine them...when you have them. You electrolyse the water into H2 and O2...only when you have water. You create methane in Sebatier reactor...only when you need it for fueling rovers and/or generators, and you have water.
So in fact - you can send even smaller T/PV cells on Mars that will generate less power and the excess power will stack-up untill you use it.
BTW: That might be a nice gameplay scenario. For instance: You need to send enought power to the other side of the map, so that they could start a refining process, and send the refined resources back to the main base.
Two more things:
One - wireless energy transfer laser can send power to multiple sources.
Two - laser-energy can send a lot more than just few kilowats per-meter. For instance:
http://www.popsci.com/technology/article/2010-04/skeeter-zapping-laser-entrepreneur-turns-sights-space-solar-powerThis is obviously far more than can be passively managed.
Thus, an active cooling system has to be transported and set up [...]
This system will require at least 50, probably in excess of 100 litres of cooling fluid to transfer the excess heat from the laser receiver to the radiator farm
A generator or RTG farm to provide the equivalent power would be as light or lighter [...]
[...] and would provide fewer points of failure.
Do you reely have some proof of those fact or did you just made them-up?
--------------------------------------------------------------------
I would like to point out the reason heat is such a major issue with this, is not due to the amount of heat, it is due to the concentration of heat. Even with atmospheric blooming lasers will be focused on a very small area, and the material that is collecting the light also is very prone to not dissipating heat.
Setting aside that I previously quoted that:
1) in the heat-exchenge test in 2009 those wireless-power laser-machines did good and passed the 100% beam light power.
2) in 2010 two machines flew over 12 hours constanlty only on the laser-beem power, and has proven to have the ability to fly indefinitely.
3) heat radiation can be managed by small amounts of simple fluids (and this techniqe is used also in space)
there are two more things that needs to be mentioned:
1) the laser doesn't needs to be fired from a single diode.
2) after 1 km, a sigle laser "dot" turns into a big circle.
On a side note though I am certain you could run a Stirling generator off the waste heat of anything over 100 watts in order to get even more power from this, but it would probably just power the thermal management loop.
Actually - no.
I know it sounds tempting, but the teams that DID try the stirling engine...lost.
It seems that a simple T/PV cell floating inside a cooling liquid is more efficient in terms of energy and mass than the laser-Stirling engine.
For instance:
One of the nice things about having multiple teams is that you get to see different ideas at work, and NSS is definitely not short on ideas.
Their first climber design featured a thermal (rather than photovoltaic) receiver, based on a Stirling engine. (Stirling engines are high efficiency engines often used for solar power generation) Stirling engines are a difficult proposition for a Space Elevator climber, since they typically weigh a lot more than a PV panel, and so NSS had to design and manufacture their own engine – and it is indeed a beauty. Using Helium as the working fluid, this engine also uses a transparent cylinder head in order to get the laser beam directly into a thermal absorber that is placed inside the cylinder – a perfect way to avoid the latency associated with the thermal mass of a regular absorber plate.
The problem NSS ran into was with properly sealing the engine while keeping the weight down. Anyone who’s ever worked with Helium knows how difficult it is to seal – it is a noble gas, and so is monatomic, which means its molecules are really small, and they get around most seals.
The other problem faced by thermodynamic engines is that while they are able to capture 100% of the energy of the beam (unlike the 30-50% of PV cells) they have to waste a good fraction of it at the heat exhaust side, and this gets worse the hotter the exhaust is. Which means that a thermodynamic engine needs to be coupled to an efficient heat exchanger – something that NSS started to design as well.
As it turned out, NSS was not able to solve the He sealing issue, and started working fast towards a photovoltaic “plan B” climber. However, not all of the effort was wasted – the heat exchanger design turns out to be very important in keeping their PV cells cool – more on that on the next post.
As a side note, Bert Murray and Matt Abrams have vowed that if the prize money is not awarded this year, they will solve the Helium seal issue and be back next year with a working Stirling climber.
http://www.spaceelevatorgames.org/And there is this....
Othertypesofreceiversarepossible,suchaslaserturbojetswhichuselaser power insteadof
combustiontoheatairandproducethrust,butphotovoltaicreceiversarethe best developed.
http://www.scribd.com/doc/37446434/Laser-Power-for-UAVs--------------------------------------------------------------------
In a gaming sense, how does a geo-stationary nuclear powered sattellite which produces a laser transimitted to the surface to a collector
I can only say this:
The idea of harnessing lasers to deliver power to a receiving solar cell has slowly gained traction over the years. A U.S. company called Solaren signed an agreement with California-based Pacific Gas & Electric to supply space-based solar power by 2016.
Japan also plans to launch its own solar power satellite by 2015, as a precursor to a larger model that would provide power to 300,000 homes. Europe's biggest aerospace company, EADS Astrium, would put its own solar-collecting demo satellite into orbit by the end of the decade. Such projects have also drawn plenty of skepticism.
http://www.popsci.com/technology/article/2010-04/skeeter-zapping-laser-entrepreneur-turns-sights-space-solar-powerI know power output would be an awful amount to produce a beam to reach the surface
Actually - not reely. If you'r point is to just send a laser (by a means of few photons) then all you need is a few kW laser that can go from Earth to the moon and back. On Mars, with it's thin air, it "should" be even easier.
But for transfering power from Mars orbit to Mars surface the situation is even better than on Earth.
Why?
1) Thin air.
2) GEO Mars orbit is 17,200 km (10,625 miles)
and Earth's GEO orbit is at: 35,700 km (22,183 miles)
so the laser "dot" would be smaller on the surface, and thus - be stronger.
Anyways, giving astronauts portable (or not) lasers to power equipment sounds like to much of a temptation to start firing at rivial factions... before you know it there will be Mars wars.
![Cheesy :D](http://hyperkat.com/scratchbox/Smileys/akyhne/cheesy.gif)