One thing that would seem to be a concern to me is how to keep the attitude steady while the ion engine is firing. Yes, not much thrust, but to make the most of it, you want it pointing in as close to the ideal direction as possible. I don't know how the various probes like Hayabusa and Dawn do it.. Cold gas? Gyro? I would not think a bar magnet would be good enough (certainly not for deep space probes, but even for earth orbit). Starting to get more complicated.
Another thought about the really cool energy analysis done by KK6MC: Besides the duty cycle imposed by wanting to be out of eclipse, there is another duty cycle imposed by the starting orbit and the desired eccentricity. For example if you were starting from a highly elliptical GTO and you want to get to high circular, you need to thrust mainly at the apogee in order to raise the perigee. If you are circular and you want to be elliptical with perigee equal to the starting height, you thrust at what will be the perigee to raise the apogee. (Of course you probably want to raise both ends some, and you may want to change the plane too but that's the general idea.)
Thanks for bringing this up...great thought experiments, and that's how real projects begin!
Burns, W2BFJ
I wonder about the amount of time spent in the Van Allen belts on the way up there. We're concerned about radiation at a 650 km orbit, it might take some heavy duty ($$) radiation tolerant components to survive a few years trip through the radiation belts as well as the final high orbit?
Jerry N0JY
Where do the gain antennas go on a 10x10x30cm HEO?
73, Drew KO4MA
Sent from my iPhone
On Apr 30, 2013, at 9:01 AM, N0JY n0jy@lavabit.com wrote:
I wonder about the amount of time spent in the Van Allen belts on the way up there. We're concerned about radiation at a 650 km orbit, it might take some heavy duty ($$) radiation tolerant components to survive a few years trip through the radiation belts as well as the final high orbit?
Jerry N0JY
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On the Outside? :-)
just like 90% of the earlier birds they are rolled or folded up until after deployment. IIRC: one of the first actually did use a rolled up tame measure for the elements.
Joe WB9SBD Sig The Original Rolling Ball Clock Idle Tyme Idle-Tyme.com http://www.idle-tyme.com On 4/30/2013 9:51 AM, Andrew Glasbrenner wrote:
Where do the gain antennas go on a 10x10x30cm HEO?
73, Drew KO4MA
Sent from my iPhone
On Apr 30, 2013, at 9:01 AM, N0JY n0jy@lavabit.com wrote:
I wonder about the amount of time spent in the Van Allen belts on the way up there. We're concerned about radiation at a 650 km orbit, it might take some heavy duty ($$) radiation tolerant components to survive a few years trip through the radiation belts as well as the final high orbit?
Jerry N0JY
Sent via AMSAT-BB@amsat.org. Opinions expressed are those of the author. Not an AMSAT-NA member? Join now to support the amateur satellite program! Subscription settings: http://amsat.org/mailman/listinfo/amsat-bb
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Hi all.
Deployable gain antennas are possible, but unfortunately attitude control is a real issue. If the orbit has a high perigee then the magnetic field for magnetorquing is minimal. With limited fuel and little or no magnetic field, keeping the antennas pointing correctly is difficult. Also, all of this getting to HEO is challenging given our lack of experience with low mass / ion propulsion. A compromise could be 4 Watts (ish) from MEO. That can be done with omnidirectional antennas, so when the batteries die and the fuel is exhausted we still have a useful satellite even if we cannot control attitude.
Would be great to team up with a group who want to test a propulsion system and apply for a launch opportunity.
Thanks
David
Here's an oldie but goodie..... http://www.g0mrf.com/MEOSAT.htm
-----Original Message----- From: Joe nss@mwt.net To: amsat-bb amsat-bb@amsat.org Sent: Tue, 30 Apr 2013 17:18 Subject: [amsat-bb] Re: Path to HEO
On the Outside? :-)
just like 90% of the earlier birds they are rolled or folded up until after deployment. IIRC: one of the first actually did use a rolled up tame measure for the elements.
Joe WB9SBD Sig The Original Rolling Ball Clock Idle Tyme Idle-Tyme.com http://www.idle-tyme.com On 4/30/2013 9:51 AM, Andrew Glasbrenner wrote:
Where do the gain antennas go on a 10x10x30cm HEO?
73, Drew KO4MA
Sent from my iPhone
On Apr 30, 2013, at 9:01 AM, N0JY n0jy@lavabit.com wrote:
I wonder about the amount of time spent in the Van Allen belts on
the way up there. We're concerned about radiation at a 650 km orbit, it might take some heavy duty ($$) radiation tolerant components to survive a few years trip through the radiation belts as well as the final high orbit?
Jerry N0JY
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!
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--- On Tue, 30/4/13, g0mrf@aol.com g0mrf@aol.com wrote:
A compromise could be 4 Watts (ish) from MEO. Here's an oldie but goodie..... http://www.g0mrf.com/MEOSAT.htm
Yes MEO would be good. It should be possible to improve the signal levels while keeping omni-directional antennas on the satellite by using lower frequencies bands.
A 144 to 50 MHz (if we can get an allocation there) transponder or 144 to 28 MHz would have a significantly reduced path loss on the downlink (8 dB ?) compared to 435/145.
73 Trevor M5AKA
more outside the box thinking...you have a gun (of sorts) on the satellite. Then fire to the rear forcing the little satellite faster in the opposite direction. We could select from .22LR to 45 ACP. I realize the anti gun folks would go bizerk. Back in my corner now. 73 Bob w7LRD
----- Original Message ----- From: g0mrf@aol.com To: nss@mwt.net, glasbrenner@mindspring.com, amsat-bb@amsat.org Sent: Tuesday, April 30, 2013 1:35:08 PM Subject: [amsat-bb] Re: Path to HEO
Hi all.
Deployable gain antennas are possible, but unfortunately attitude control is a real issue. If the orbit has a high perigee then the magnetic field for magnetorquing is minimal. With limited fuel and little or no magnetic field, keeping the antennas pointing correctly is difficult. Also, all of this getting to HEO is challenging given our lack of experience with low mass / ion propulsion. A compromise could be 4 Watts (ish) from MEO. That can be done with omnidirectional antennas, so when the batteries die and the fuel is exhausted we still have a useful satellite even if we cannot control attitude.
Would be great to team up with a group who want to test a propulsion system and apply for a launch opportunity.
Thanks
David
Here's an oldie but goodie..... http://www.g0mrf.com/MEOSAT.htm
-----Original Message----- From: Joe nss@mwt.net To: amsat-bb amsat-bb@amsat.org Sent: Tue, 30 Apr 2013 17:18 Subject: [amsat-bb] Re: Path to HEO
On the Outside? :-)
just like 90% of the earlier birds they are rolled or folded up until after deployment. IIRC: one of the first actually did use a rolled up tame measure for the elements.
Joe WB9SBD Sig The Original Rolling Ball Clock Idle Tyme Idle-Tyme.com http://www.idle-tyme.com On 4/30/2013 9:51 AM, Andrew Glasbrenner wrote:
Where do the gain antennas go on a 10x10x30cm HEO?
73, Drew KO4MA
Sent from my iPhone
On Apr 30, 2013, at 9:01 AM, N0JY n0jy@lavabit.com wrote:
I wonder about the amount of time spent in the Van Allen belts on
the way up there. We're concerned about radiation at a 650 km orbit, it might take some heavy duty ($$) radiation tolerant components to survive a few years trip through the radiation belts as well as the final high orbit?
Jerry N0JY
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!
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author.
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program!
Subscription settings: http://amsat.org/mailman/listinfo/amsat-bb
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Then fire to the rear forcing the little satellite faster
Yeah, but the control, er safety, folks won't give us enough "mass out the ass" to propel us forward ... can't have a clip with 30 pretty soon!
-- 73 de JoAnne K9JKM
I'll throw this one out there though I'm sure some of you already know about it. "Rocket Propulsion Elements" is a pretty good book on the basics of rocket propulsion. I've dabbled in it a few times but do plan on a more comprehensive study (I'm an EE and actual coursework takes precedence over this, when I graduate I'll have more time).
http://www.amazon.com/Rocket-Propulsion-Elements-7th-Edition/dp/0471326429/r...
Bryce KB1LQC
On Wed, May 1, 2013 at 6:50 PM, JoAnne Maenpaa k9jkm@comcast.net wrote:
Then fire to the rear forcing the little satellite faster
Yeah, but the control, er safety, folks won't give us enough "mass out the ass" to propel us forward ... can't have a clip with 30 pretty soon!
-- 73 de JoAnne K9JKM
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If the solar panels are on 1 end that could be the back side of a patch antenna or reflectors for a Yagi. A 3U gives us about 12 inches in one plane. We will have reaction wheels to do pointing. Both Pumpkin and ISSIS say they have flight heritage on > 50 watt panels. EaLanta has rides to 600 KM and we will have to deal with MR Van Allen when we get there.
This is a great topic at the attitude adjustment session with cold 807's at Dayton
CU there nick K%QXJ
Where do the gain antennas go on a 10x10x30cm HEO?
73, Drew KO4MA
Sent from my iPhone
On Apr 30, 2013, at 9:01 AM, N0JY n0jy@lavabit.com wrote:
I wonder about the amount of time spent in the Van Allen belts on the way
up there. We're concerned about radiation at a 650 km orbit, it might take some heavy duty ($$) radiation tolerant components to survive a few years trip through the radiation belts as well as the final high orbit?
Jerry N0JY
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
_______________________________________________ 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
participants (10)
-
Andrew Glasbrenner -
Bob- W7LRD -
Bryce Salmi -
Burns Fisher -
g0mrf＠aol.com -
JoAnne Maenpaa -
Joe -
M5AKA -
N0JY -
Nick Pugh