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New Way of Extending Satellite Life Saves Millions
coondoggie writes "A new technique to save aging satellites promises to save millions of dollars by extending the life of communications spacecraft. A process developed by researchers from Purdue University and Lockheed Martin has already saved $60 million for unnamed broadcasters by extending the service life of two communications satellites. In a nutshell the technique works by applying an advanced simulation and a method that equalizes the amount of propellant in satellite fuel tanks so that the satellite consumes all of the fuel before being retired from service. Some aging communications satellites are each equipped with four fuel tanks. If one of the tanks empties before the others, the satellite loses control and should be decommissioned, wasting the remaining fuel in the other tanks."
If there are four propellors with separate tanks, and one empties early, borrow from other tanks so you don't have to throw the whole thing out! What a brilliant idea! I think that's worthy of a patent.
... on a satellite."
"A process for shifting resources from areas with a surplus to those that have run out
Hey -- maybe if I act quickly I can get a patent on "sending a refueling pod"!
(I don't know if this should count as funny, flamebait, or insighful.)
Apology to Ubuntu forum.
They didn't do that.
Well, of course they didn't. That would have infringed on UbuntuDupe's patent.
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ink jet cartridges...
Oh wait... who am I kidding...
I already tried to but apparently I needed 3 other patents to balance it out and now my application is just spinning wildly out of control.
Do not try to read the dupe, thats impossible. Instead, only try to realize the truth
What truth?
There is no dupe
Oh wait... who am I kidding... I just tried it out and your idea works well, but I'm wondering why my pr0n printouts have green nipples!
Well, back to rejecting software patent applications.
It really sounds like they just applied load balancing to the fuel tanks...
Ask not what you can do for your country. Ask what your country did to you
Oh, great... so now Martin Marietta is gonna file a DMCA complaint and demand the arrest of...
Good Show in either case!
Quo usque tandem abutere, Nimbus, patientia nostra?
My interpretation was that the difficulty is figuring out how much fuel is left in each tank in a weightless environment where each can be at dramatically different temperatures (one on the sun-side and one on the shade-side).
"It's not a rocket science!"
But this time it really is!
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Just to be clear, a GEO satellite doesn't really decay. It will fluctuate and perturb, yes; the N-S drift due to the Sun and Moon are particularly annoying. However, it won't lose altitude like a LEO satellite will since there is no atmosphere at all, not even the very sparse atmosphere that slows down those spacecraft.
Sure, it seemed likely that an idea that's obvious to the morons here has been nonetheless overlooked by decades of aerospace engineers, but this time that doesn't appear to be the case.
What I'm listening to now on Pandora...
Who launches a multimillion satellite to space without making sure that it fully uses resources left onboard before retiring?
It has lived its full life. It has reached the end of service. But wait, for a few hundred thousand or so in research/fuel shifting, we can net an extra six months in orbit and $50M in revenue. Do we do it? Do we? Of course.
**that** is the situation. And yes, it is rocket science. Read the first page of the paper at least, they did something creative.
coondoggie
inkslinger77
narramissic
jcatcw
jpkunst
Looks like they spread out the work over a few shill user accounts, which is to be expected. If it's all OK and everything with the corporate ownership of Slashdot to be played by IDG, I suppose that's their business, but one would hope that they are actually getting PAID for being part of IDG's advertising program. And of course there should be disclosure so that visitors to Slashdot realize they are reading advertisements and not an article submitted by a "real" user...
If you want news from today, you have to come back tomorrow.
With all the answers here from "Why not just have one tank?" to "Run a tube between them" to "God, they're so stupid!", I'm surprised that Lockheed Martin didn't just do an Ask Slashdot posting. Baby, Slashdot coulda saved you millions already. Call me.
A friend of mine was hired to work on this project. It's actually pretty tricky. Attitude correction generally involves very brief "puffs" of jets. Of course they measure the fuel consumed in these brief blasts but over years the errors accumulate.
You can't let it run out of fuel since you need enough fuel to deorbit it at end of life. But given the cost of a satellite, each extra month of life is worth millions.
The fuel is floating around in microgravity so you can't weigh it. I'm not sure but I think the most promising technique involves looking at the rate of heating when the tank-heaters are on. But accurately correcting out the effects of solar-heating and the various forms of heat loss is still lots of work.
~~~~~~~
"You are not remembered for doing what is expected of you." - Atul Chitnis
Bearded Dragon
I'm reminded of a quote by some NASA Scientist, on the NEAR probe: "We have no fuel on board, plus or minus 8 kilograms"
Returned Peace Corps IT Volunteer
Good Luck trying to get NASA to effect such a change. Maybe this publicity will help.
I had another solution to the same problem, back about 1990. I worked for Contel, my job was to write an expert system to assist in dumping momentum (use propellent to counter build-up caused by attitude gyros spinning too fast) for the TDRSS satellite system. I asked why momentum builds up. Answer: solar wind against antenae. My suggestion was to build models of antenae configurations or solar array that would drive up or down the momentum as needed... in essence to sail back into normal configuration. The potential exists here to NOT USE PROPELLENT, extending the life of satellites dramatically.
I talked to my bosses and to NASA. And basically, I was told to shut up and sit down. They had procedures for dumping momentum. As a sub-contractor we were PAID to dump momentum. And even though they re-orient the antennae array all of the time, they have no procedure to move the antennae to slow dump momentum during times of low utilization.
In other words, NASA didn't want to deal with new ideas, and have to deal with the work associated with it, or overseeing the work in others. Everything is risky when you don't want to bother.
This has since become one of my stories... the moral being that the tech solution is not necessarily the right solution.
Geostationary spacecraft aren't as stationary as we'd like. Due to many forces (the earth's oblateness, tessoral harmonics in the earth's gravitational field, gravity from the moon and the sun), these spacecraft tend to drift, requiring occasional burns of small rockets to keep the spacecraft where it belongs.
... recording exactly how many grams of fuel was used in each burn. This is imprecise, because of the nature of propellant gauging by measuring pressure and timing burns. So every now and then, the four tanks of hydrozine would be rebalanced by connecting all the tanks together and letting the fuel equilibrate between 'em. Rebalancing the tanks is done by warming a tank and connecting it to the others. The amount of heat to put into a tank depends on how much fuel is in there, but you can't directly measure this ... you depend on book keeping.
In the spacecraft, each of four tanks contains the fuel (hydrazine) and a pressurizing gas (typically helium). There's a system of pipes and valves to allow any tank to feed any of the sets of x-y-z rocket motors. Of course, valves are unreliable, so there's the usual redundancies and crosslinked fuel pipes.
Stationkeeping in geosynchronous satellites requires precisely metered burns at just the right times. Shoot too much hydrazine, and the satellite moves out of the window, and everyone's TV reception goes to pot. Worse, you'll have to fire the rockets again and use more fuel to undo the damage from the previous burn. Too little hydrazine means that you'll need several burns, but these can only be done at certain times. If your first burn is insufficient, you may have to wait for a month (or sometimes six months) before you can fix it. (In fact, you seldom know the exact effects of a burn until doppler & tracking data is analyzed over the next days)
Now, suppose the satellite is low on fuel -- it's near the end of a 15 year lifespan. Three tanks have a little liquid fuel. The fourth tank runs out. If you then simply mix the four tanks, the output fuel line will get a mix of hydrazine and helium. The two phases in the fuel line will cause the motor to sputter, flare, or fizzle. Bad news!
So this is a non-trivial problem. And there's lots of money hanging on the answer.
In the past, the amount of fuel in each tank was determined by simple book-keeping
This paper sounds like they're relating the amount of heat put into a tank, and the tank's temperature. From this relationship, they're getting a better determination of the total hydrazine in each tank, and thus they can better balance the fuel in each tank.
In short, they came up with a nice way to estimate the amount of hydrazine in each tank by measuring the thermal effects. It's a good idea. Might add a few months to the lifespans of some old spacecraft which were launched in the 1990's.
How is pumping affected by lack of gravity besides lowering power requirements on the pump to overcome the same? If the fuel is a gas you don't actually need any pumps - pressure will equalize itself. If it's liquid, you will already need some way to get rid of empty space in the tank, otherwise you would have hard time getting globules floating around to the reaction chamber.
To give you an idea that there is indeed some difficulty here, I'll quote the article:
"It took a year and a half of thermal pumping, carried out at different times, to accomplish the rebalancing".
I'll give a small sample of a multitude of problems.
Since you really aren't anchored to anything, you can't risk performing actions that would perturb your orientation. Change your orientation, and you will need to use fuel to get you back into position which defeats the purpose of equalizing your fuel since you used up what you would have saved.
Remember, they problem of 'pumping' the fuel has been solved. It really is the difficulty of pumping the fuel when the needle is on 'E' and knowing that you won't run out between exits on the interstate.
Out of modpoints but really liked a post? 1BDkF6TtmmeZ3yqXbz9yhdYVqRYnwFoXDj
Some folks formerly at Schriever Air Force Base did something similar with Defense Satellite Communication Systems satellites, which saves the Air Force $5 million per year per satellite. There's more on that story here.
!#@%*)anks for hanging up the phone, dear.
Millions of what, satellite overlords?
I was flipping bits on an abacus, newb.
You mean create a single point of failure?
Fuel=zero plus or minus 8kg. That pretty much sums up the level of uncertainty. It's easy from the comfort of terra firma, many degrees removed from actual work-day problem-solving about this to assume that there's a fuel gauge at least as accurate as on a car. Such is not the case. Obviously five decades of space technology is not enough time to have all the answers all the time.
Wish I had mod points for you for bringing me back down to Earth, so to speak. (why yes, that IS a selfish attitude!)
My first thought when I read the summary was along the lines of this:
WTF?!?!? We've been building semi's (18 wheelers) and satellites about the same amount of time- have the rocket scientists not heard of crossover fuel lines? (they connect left and right tanks and allow for equalization of the fuel level), then I thought...Hmmm...Space, the final frontier...Oh wait! Uhmmm atmospheric pressure, constant gravity from a predictable direction, reasonably constant temps and density- in a moderate range....none of this applies! WTF do we do now?
I hereby revoke my armchair Astrophysics and Rocket Scientist privileges for a week.
Mechanical/electrical engineering in space is no trivial thing. Obvious Earth-bound solutions seem to fail frequently when applied to cold vacuum with micro-gravity. It may not always seem to be so difficult from here, but up there it could be a whole new problem.
Hopefully, even their most inaccurate 'fuel gauge' is better than the one in my car...I either have a quarter of a tank (when FULL) or it reads Empty below an actual 3/4 tank, and you have to use the odometer (Oh Sh*t!, was it reset last fuel-up?!?!?) to guesstimate what the real fuel level may be.
Yes, you all can laugh at me for this. My only semi-reasonable defense can be that I just walked in from work 10 minutes ago, after dealing with John Q Public and Josephine Sixpack for the last 10 hours. I mistakenly bit this worm, dunked the bobber, and now am caught...hook, line, and sinker.
My bad, but I'm at least mouse/man enough to admit it!
Down With Slashdot BETA!!! I've been around the corner and seen the oliphant; you can only abuse me from your perspecti