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MAVEN development to orbit insertion
mcaplinger
post Apr 10 2013, 04:10 AM
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QUOTE (centsworth_II @ Apr 9 2013, 09:03 PM) *
My guess: So they can be as long as possible and still fit in the fairing?

From http://lunar.colorado.edu/~jaburns/astr480...AVEN-ExSumm.pdf

QUOTE
The solar arrays were enlarged to allow a “gull-wing” design, to shift the center of pressure (CP) relative to the center of gravity
(CG) and provide aerostability under all circumstances.



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nprev
post Apr 10 2013, 05:01 AM
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A very fine example of learning from experience & making improvements, I'd say. That's how it works. smile.gif


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djellison
post Apr 10 2013, 05:10 AM
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QUOTE (centsworth_II @ Apr 9 2013, 08:03 PM) *
My guess: So they can be as long as possible and still fit in the fairing?


They have hinges. Fitting isn't a problem. Indeed - having them at the angle they are means they must be BIGGER to provide equivilent power margin compared to entirely 'flat' arrays.

QUOTE
Also, no solar cells are on the bent portions so nothing to do with power


The very first hit for a Google image search of 'MAVEN solar panel' (and indeed every artists impression of MAVEN ever released) shows that there are indeed solar cells on the angled panel

http://lasp.colorado.edu/home/maven/files/...solar_panel.jpg
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mcaplinger
post Apr 10 2013, 05:31 AM
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QUOTE (djellison @ Apr 9 2013, 10:10 PM) *
having them at the angle they are means they must be BIGGER to provide [equivalent] power margin compared to entirely 'flat' arrays.

Cosine losses for these small angles are pretty negligible, of course (e.g., cos(10) is 0.98).


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Explorer1
post Apr 10 2013, 08:41 AM
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And the other option, putting the magnetometers on their own booms, would probably have been too heavy. Makes sense.
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djellison
post Apr 10 2013, 01:52 PM
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QUOTE (mcaplinger @ Apr 9 2013, 10:31 PM) *
Cosine losses for these small angles are pretty negligible, of course (e.g., cos(10) is 0.98).


Good point - I was only inspired to mentioned it because the paper you linked to does use the phrases "The solar arrays were enlarged to allow a “gull-wing” design..." before going on to talk about CP/CG etc.
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mcaplinger
post Apr 10 2013, 02:28 PM
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QUOTE (nprev @ Apr 9 2013, 10:01 PM) *
A very fine example of learning from experience...

I'm not sure what experience you're talking about. Previous Mars orbiters using aerobraking (e.g., MGS, MRO) have had articulated solar panels that could be shuttlecocked back for stability. MAVEN has fixed panels so this wasn't an option.


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dvandorn
post Apr 10 2013, 10:17 PM
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This, of course, would not be the first time a Mars probe has had some kind of "trim flaps" at the tips of its solar panels, and the reasoning was similar, if not exactly the same.

Mariners 3 and 4 (of which only Mariner 4 survived launch) had small triangular trim tabs at the ends of its solar panels. This was not for aerodynamics, but for pressure dynamics. They were used to take advantage of the pressure of the solar wind to help keep the spacecraft stable.

IIRC, the stabilizing force was so minuscule that follow-on probes omitted this kind of feature. They weren't worth the weight penalty. Now that we're dealing with much thicker gasses than the solar wind (with aerobraking maneuvers), adding stabilizing tabs apparently becomes worth the weight penalty.

-the other Doug


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Paolo
post Apr 11 2013, 05:15 AM
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QUOTE (dvandorn @ Apr 11 2013, 12:17 AM) *
Mariners 3 and 4 (of which only Mariner 4 survived launch) had small triangular trim tabs at the ends of its solar panels. This was not for aerodynamics, but for pressure dynamics. They were used to take advantage of the pressure of the solar wind to help keep the spacecraft stable.


the Mariner sails, just like solar sails (IKAROS etc) exploit the radiation pressure of solar photons, which has nothing to do with the solar wind
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kwan3217
post Apr 12 2013, 02:51 PM
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About the angled panels: As a previous poster said, the panels are angled so that the craft is stable when flying through the atmosphere. What no one has noted is why it needs to be stable. Maven is NOT going to aerobrake. It goes initially into a 35-hour highly elliptical orbit, but after a couple of days it performs another powered maneuver to lower the period from 35 hours to 4.5 hours, all in one burn.

The spacecraft performs periodic deep dips, to allow the instruments on board to touch, smell, and taste the atmosphere. It dips in to the upper atmosphere, as low as the scientists could convince the engineers to go, stays low for a couple of (4.5 hour) orbits, then raises periapse back out of the atmosphere. It does this several times (5 times planned for the prime 1-earth-year mission) because the orbit precesses such that the periapse latitude changes, and therefore the spacecraft can deep-dip at a variety of latitudes.

So, the panels are angled to be stable, and it needs to be stable not for aerobraking but for deep dips.

Also, the science orbit is not optimal for relay, and the relay orbit is not optimal for science. At some point, the plan is to maneuver from an orbit more friendly to science to an orbit more friendly to relay, for sure after the 1-earth-year prime mission is complete, but as late as the scientists can convince the project managers. The relay equipment on Mars Odyssey and Mars Recon Orbiter both still work fine, but they won't last forever. Maven is a backup/replacement for those.

I have never heard about a plan for a terminal deep-dip, and from what I can tell, the scientists would prefer a longer mission to going out in a blaze of glory, even if relay were not an issue.
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MahFL
post Apr 15 2013, 11:39 AM
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MAVEN was always going to serve as a relay, and it's orbit was going to be changed to enable that.
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Astro0
post May 4 2013, 09:55 AM
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Send your name and a message to Mars with MAVEN.

http://www.nasa.gov/home/hqnews/2013/may/H...me_to_Mars.html
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punkboi
post May 8 2013, 12:29 AM
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I think this is the first time that names were collected for a Mars orbiter mission and not a lander/rover. I guess MAVEN wasn't getting as much attention in the public as NASA would like.


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vjkane
post Jul 8 2013, 07:40 PM
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I'm hoping someone here can help me out. I'm writing a piece for my blog on possible future planetary smallsats. I want to use MAVEN as an example of the current state-of-the-art Discovery-class mission (the rules for the Mars Scout program were very similar). I've looked all over the web, but I can't find out what the total mass of MAVEN's instruments will be. Do any of you know or have a lead of where I might look?

Thanks!


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mcaplinger
post Jul 9 2013, 05:14 PM
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QUOTE (vjkane @ Jul 8 2013, 12:40 PM) *
I'm writing a piece for my blog on possible future planetary smallsats. I want to use MAVEN as an example of the current state-of-the-art Discovery-class mission... I can't find out what the total mass of MAVEN's instruments will be.

http://www.lpi.usra.edu/meetings/marsconce...4267.pdf‎ has some (not-entirely-consistent) numbers in it.

I'm not sure I would believe everything you can find about smallsats -- a lot of blue-sky hype in that area, not so much real engineering. A summary article that just echoes a lot of marketing fluff is not that valuable IMHO.


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