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Registered Member #96
Joined: Thu Feb 09 2006, 05:37PM
Location: CI, Earth
Posts: 4061
Hi.. Seems that technology originally developed back in 2004 may finally allow a self contained Lifter to be built.
The basic concept is similar to DARPA's remote charging of UAVs, in this case a laser is used to remotely charge the unit's internal LiPo cells via a solar array "on the fly" when it begins to lose power.
I envision something like a large circular ring structure with spokes going towards the centre, containing the solar cells and associated electronics, HV supplies etc.
The really novel part is that the solar array could be "flipped" mechanically (as part of the tracking system) to draw power from the Sun once at altitude.
The use of diode split piezoelectric transformers for the HV stage gets around many of the limitations of conventional (heavy/inefficient) wound units, reducing the problem to a simple matter of synchronising the transformers electronically so they are in phase and the voltages add on the positive peaks.
Registered Member #27
Joined: Fri Feb 03 2006, 02:20AM
Location: Hyperborea
Posts: 2058
A simple lifter delivers a thrust of 1 W/g, so assuming that your total budget is 1 kg you need to fit a 1000 W solar panel and the high voltage converters in 500 g.
Registered Member #56
Joined: Thu Feb 09 2006, 05:02AM
Location: Southern Califorina, USA
Posts: 2445
There was a thread about the possibility of a lifter powered by a LiPo battery, and eventually it was determined it wouldn't really be worth the effort.
It would be possible to do it with solar cells, a properly optimized cell can get >60% efficiency at intensities exceeding 1MW/m^2, so with a 1500w diode array over 15cm^2 array you could get the better fraction of a kw of power into your lifter (this is what the space elevator people are doing). Of course operation would have to be short, since the poor thing would be getting cooked with over 1kw of power being focused on it! And that goes without saying such a system is a bit beyond the grasp of a garage budget...
It is oddly tempting, I have such a diode array (1.3kw roughly) and a good single junction silicon cell should give about 40% efficiency at 800nm... If only I didn't have 37 other projects going on already
Registered Member #162
Joined: Mon Feb 13 2006, 10:25AM
Location: United Kingdom
Posts: 3140
I'm not sure how your local authoritiswould view a kilowatt laser being scanned around the sky, but here in UK >1 milliwat would be discouraged, to put it mildly.
Must admit, Lifters have never interrested me - I'd use a helium ballon!
Registered Member #96
Joined: Thu Feb 09 2006, 05:37PM
Location: CI, Earth
Posts: 4061
someone also pointed out that solar cells lose efficiency when hot, so one idea might be to cool the back of the panel with the inline airflow.
Obviously this would only be safe with a dedicated launch corridor (iirc the guys using the plasma based laser flier have such a clearance as well as a multi-MW laser) but for indoor use the power requirements might not be as high.
Powerbeam have a similar system based on lasers, however in their case it has built-in failsafes to prevent exposure to the beam if it is cut or loses lock on the target device.
Registered Member #10
Joined: Thu Feb 02 2006, 09:45AM
Location: Bunbury, Australia
Posts: 1424
From my website page on Lifters: "My lifter, give or take, uses 5 W to lift its 3 g (= 0.6 g/W). This neat little helicopter weighs about 2500 kG, and lifts a further 2500 kg using 1 MW. Proportionately 1MW would lift 600 kg with my lifter specs. Only about 1/4 that needed to achieve lift of the helicopter. One wonders if technology can't offer something more efficient than my triangular lifter though. I have a few ideas ..... "
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Laser powered Lifter?
