Much of the debate on the board here arises from our common desire to see the launching of satellites with a larger footprint.
A fine analysis of one approach to this is the video and ppt of David, G0MRF, discussing his ideas for a bird that reaches the financial sweet spot, between LEO and HEO, a 'middle earth orbit, or MEO.
http://www.batc.tv/vod/AMSAT-UK_MEO.flv and http://www.uk.amsat.org/2009/2c_Bowman-MEO.pdf
He points out that a bird at 7000 km altitude is beyond the inner radiation belt and yet has a pass duration of 90 minutes and a footprint diameter of over 13,000 km.
Here's the great thing, though: it is possible to do an orbital transfer from LEO to MEO.
David points out some difficulties, though: VLSI electronics components are not as tolerant of radiation than others, and the attitude control of the second burn might be tricky.
Another approach (also gleaned from David's rich harvest), which would be even more simple, and perhaps within the realm of a 3x cubesat, would be to raise a typical cubesat from its 650km altitude to the 1400km or so that has made AO-7 so popular.
An elliptical orbit, requiring only one 'burn' might even be seen as an advantage. As David says, it would allow for the bird eventually to be deorbited, but it would also mean that periodically the bird could be used with very simple antennas for local communications, and on other occasions would require a better groundstation affording a wider footprint.Using DH2VA's propulsion spreasheet, I see that delta_v for one half of a Hohmann Transfer Orbit from 650 to 1500 is 212 m/sec ish. Since my understanding of the HTO is that it comprises two burns, one creating an ellipse, the second turning that ellipse into a circle, I've assumed that that number is about right for an elliptical orbit with the final altitude.
Using David's http://g0mrf.com/MEOSAT.htm, I gather that the Isp of a cold-gas thruster is about 60 sec, which should be enough to get the necessary delta_v above.
And then there's the transponder. With William PE1RAH's transponder board in hand, and the work about to be done on FUNCUBE (not to mention Delfi C3 and NE3T), we should have a very good idea of what can be achieved with linear transponders in small LEO vessels. With one or two of the cubes dedicated to thrust, we'd have lots of solar panel area. What about a software transponder vs. hardware transponder shootout with respect to volume and power requirements? Could a software transponder include the modulation/demod of a suitable digital mode, allowing less elaborate stations to work the bird at apogee?
Anyway, that's the sort of fun one can have with the materials that David has provided.
From a promotional standpoint, a project that aims to provide the
functionality of AO-7 could highlight the remarkable success of that bird and at the same time point out the new opportunities and challenges in space.
73, Bruce VE9QRP
Much of the debate on the board here arises from our common desire to see the launching of satellites with a larger footprint.
For what it is worth, this semester I will finally get a student to work on the 40 year old AMSAT idea of a water rocket. (Carry water to orbit and use solar power to electrolizie the wate to H2 and O2 and then burn those in a thruster to raise the orbit of a cubesat.
Mostly the goal is to get from the very low (short lived) LEO to a higher LEO to get longer life, but it will be fun to get this project going again. I had a working model about a dozen years ago, but it eventually blew up.. Now we will get another one built probably...
Bob
Morning Bob,
This water fuel sounds interesting.
I know you can seperate water into it's components with electricity as you say. common .
But when water either Boils, evaporates, or in the case of a vacuum, again a somewhat different "Boil" and turns gaseous, is it still H2O or has it broke down into it's components also?
Joe
Robert Bruninga wrote:
Much of the debate on the board here arises from our common desire to see the launching of satellites with a larger footprint.
For what it is worth, this semester I will finally get a student to work on the 40 year old AMSAT idea of a water rocket. (Carry water to orbit and use solar power to electrolizie the wate to H2 and O2 and then burn those in a thruster to raise the orbit of a cubesat.
Mostly the goal is to get from the very low (short lived) LEO to a higher LEO to get longer life, but it will be fun to get this project going again. I had a working model about a dozen years ago, but it eventually blew up.. Now we will get another one built probably...
Bob
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On Mon, Aug 24, 2009 at 12:11 PM, Robert Bruningabruninga@usna.edu wrote:
Much of the debate on the board here arises from our common desire to see the launching of satellites with a larger footprint.
For what it is worth, this semester I will finally get a student to work on the 40 year old AMSAT idea of a water rocket. (Carry water to orbit and use solar power to electrolizie the wate to H2 and O2 and then burn those in a thruster to raise the orbit of a cubesat.
Bob --
Thanks for letting us know about this. It sounds very interesting. As the water would be under far less pressure than, the nitrogen (e.g.) in a cold-gas thruster, would the water/electrolysis system be considered safer to launch? I can see the argument being made that a leak in a water container would likely ruin a great number of things on the launch than would an inert gas. OTOH, the (I presume) low pressure would reduce the likelihood of a leak.
Mostly the goal is to get from the very low (short lived) LEO to a higher LEO to get longer life, but it will be fun to get this project going again. I had a working model about a dozen years ago, but it eventually blew up.. Now we will get another one built probably...
If such a system were used in flight, instructors could do simple electrolysis of H2O and combustion on the ground to illustrate the process quite vividly!
73, Bruce VE9QRP
On Mon, Aug 24, 2009 at 12:11 PM, Robert Bruningabruninga@usna.edu wrote:
For what it is worth, this semester I will finally get a student to work on the 40 year old AMSAT idea of a water rocket. (Carry water to orbit and use solar power to electrolizie the wate to H2 and O2 and then burn those in a thruster to raise the orbit of a cubesat.
Bob --
Very interesting concept! Probably not much in the way of thrust, but the amount of "fuel" that can be created from a little water is pretty large, and we have lots of time.
But, tell me, in zero gravity, how is the gas separated from the water? On Earth is just floats to the top, but that doesn't work in outer space. Is the whole thing spun?
Greg KO6TH
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This is neat. How many times more powerful than venting steam out a nozzle?
73, Joe kk0sd
-----Original Message----- From: amsat-bb-bounces@amsat.org [mailto:amsat-bb-bounces@amsat.org] On Behalf Of Greg D. Sent: Tuesday, August 25, 2009 10:45 PM To: bruninga@usna.edu Cc: amsat-bb@amsat.org Subject: [amsat-bb] Re: High LEO for cubesat?
On Mon, Aug 24, 2009 at 12:11 PM, Robert Bruningabruninga@usna.edu
wrote:
For what it is worth, this semester I will finally get a student to work on the 40 year old AMSAT idea of a water rocket. (Carry water to orbit and use solar power to electrolizie the wate to H2 and O2 and then burn those in a thruster to raise the orbit of a cubesat.
Bob --
Very interesting concept! Probably not much in the way of thrust, but the amount of "fuel" that can be created from a little water is pretty large, and we have lots of time.
But, tell me, in zero gravity, how is the gas separated from the water? On Earth is just floats to the top, but that doesn't work in outer space. Is the whole thing spun?
Greg KO6TH
_________________________________________________________________ With Windows Live, you can organize, edit, and share your photos. http://www.windowslive.com/Desktop/PhotoGallery _______________________________________________ Sent via AMSAT-BB@amsat.org. Opinions expressed are those of the author. Not an AMSAT-NA member? Join now to support the amateur satellite program! Subscription settings: http://amsat.org/mailman/listinfo/amsat-bb
Bob, do you really mean a CubeSat or any picosat?
Recent CubeSat Spec changes have increase mass to 1.333kg/cube or 4kg for a triple cube which could play nicely into your plans to giving you more water to zap when in orbit.
http://cubesat.atl.calpoly.edu/media/CDS_rev12.pdf
You have indeed taken on a big challenge of not only the propulsion of a CubeSat but also stabilizing and orienting it for each burn.
Please keep us posted on developments.
73, Alan VE4YZ EN19kv AMSAT LM 2352 http://www.wincube.ca
-----Original Message----- From: amsat-bb-bounces@amsat.org [mailto:amsat-bb-bounces@amsat.org] On Behalf Of Greg D. Sent: August 25, 2009 10:45 PM To: bruninga@usna.edu Cc: amsat-bb@amsat.org Subject: [amsat-bb] Re: High LEO for cubesat?
On Mon, Aug 24, 2009 at 12:11 PM, Robert Bruningabruninga@usna.edu
wrote:
For what it is worth, this semester I will finally get a student to work on the 40 year old AMSAT idea of a water rocket. (Carry water to orbit and use solar power to electrolizie the wate to H2 and O2 and then burn those in a thruster to raise the orbit of a cubesat.
Bob --
participants (6)
-
Alan VE4YZ -
Bruce Robertson -
Gary "Joe" Mayfield -
Greg D. -
Joe -
Robert Bruninga