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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.
Pardon me if I don't cry out with excitement at this "discovery." It looks more like a built in obsolescence feature has been circumvented rather than an actual technical breakthrough.
Seriously, who didn't learn the lesson of the limiting reagent in high school chemistry?
When the only tool you have is a claw hammer every problem starts to look like the back of someone's skull.
They didn't do that.
Well, of course they didn't. That would have infringed on UbuntuDupe's patent.
<Complete your profile by adding a signature!>
(I don't know if this should count as funny, flamebait, or insighful.)
None of the above. Your post was just stupid.
This post, however, is insightful as fuck.
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
Who launches a multimillion satellite to space without making sure that it fully uses resources left onboard before retiring? Even if four separate fuel tanks are necessary, they can be just connected by small pipes and fuel can be redistributed with a pump powered by satellite's solar cells. It's not a rocket science!
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
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).
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.
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"You are not remembered for doing what is expected of you." - Atul Chitnis
The article is rather vague, saying that's how much they saved, but then how much revenue the satellites bring in over 6 months. If it's the later, that the income these satellites made, not what they saved. If they bring these down at the start of the 6 months instead of the end, they'd still earn the revenue by having the replacement satellites in place at the earlier date. Anyway, this doesn't really save much, it just allows them to push back the cost of launching the new satellites half a year. I suppose over 30 replacement cycles (15 year life, 6 month extra use, 450 years total) barring advancements in satellite engineering, they would finally have save the cost of one satellite and lanch. I'm not saying it's not a good thing that they've done this, but the article is pretty poor about the numbers and over states the benefits.
You would be correct sir, if we were talking about an environment with gravity.
However, since we are not, your plan would be as likely to empty at least one tank while filling the rest as to equalize the fuel between them.
Any sufficiently advanced technology is indistinguishable from a rigged demo.
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.
They should just put guns on the satellite. When the satellite passes overhead any ground-based fuel tanks it can blow them up, and the spaceship fuel tanks will fill up again.
I thought everybody knew that.
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beware he who would deny you access to information, for in his mind he dreams himself your master
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 would the guns be reloaded? Firing away from the Earth?
I just read Slashdot for the articles.
If the tubes are pressurized fluid fuel, then they will equalize perfectly well, gravity or no gravity.
People in Soviet Russia, however, appear to be afflicted with amusing juxtapositions of the aforementioned situation
Why don't they just use a system with a collapsible fuel bladder inside of a pressurized tank? You could monitor the temperature and pressure inside the tank to see how much the gas had expanded to replace fuel volume.
In Soviet Russia meme tires of you!
Or, even better, you could just run the internet between the fuel tanks! That way, there's not just one, but a SERIES of tubes between them!
Please put some pants on before you post again.
who wants a Satellite flavored life saver, regardless of how long it lasts
1) Your analysis is based on bad assumptions so your result is way off. 2) You're a sick bastard for fucking a horse.
Outside of a nutshell?
Must be a pretty big nutshell to fit a commsat.
Because technology in communication seems to get better and better, wouldnt be better to replace a satellite with a better one? Or are we at the point in optomizeing communication that it would be better to keep an old fleet longer? All in all, it is pretty nice to have a long life span in communication satellites given that the typical time of life is usually anywhere from 5 years to 15.
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.
Assuming you man one fuel and one oxidizer tank not just one tank (boom!), redundancy.
Oh and more redundancy.
And possibly a little backup.
You're thinking small. Why miniaturize the laser, when we could instead enlarge the sharks? -John Searle
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.
Basically, yes. I did an internship with GE AstroSpace during the summer of 1991, and I worked with an engineer in their propulsion group testing exactly this concept. We had a small tank, which we covered with heating elements and temperature sensors, wrapped with typical insulating materials as it would be on a satellite, filled it with various amounts of fluid and helium, stuck it in a vacuum chamber (to eliminate convection effects), and ran it through some heating and cooling cycles while measuring the temperature response.
There's a formula from thermodynamics (which I no longer remember) that relates the change in temperature to the energy added to a system, the mass of the system, and the thermodynamic properties of the materials in the system. In our experiment we knew the values of all of the variables within a certain error, and we were able to verify that the equation was accurately modeling the test. We were also able to invert the equation to solve for the mass of the propellant, and with some fancy analysis we determined the error range for that mass, given the error ranges of our other variables. (eg: the amount of energy going into the tanks depends on the voltage and current going to the heating elements, which the satellite telemetry could measure and report but not precisely, and the temperature could also be measured and reported but not precisely.)
What's really key in the end result isn't the mass of the propellant left in the tank; it's the error. As you noted, the traditional approach is bookkeeping, where the amount of fuel used for each burn is estimated, and over time the errors in that estimate add up. So, near the end of life, you know that you have 2 years worth of propellant, plus or minus six months. With the temperature-response approach, we were able to show that you can reduce the error to plus or minus two months (for example). With bookkeeping, the satellite has to be replaced at 2 years - six months, but with temperature-response it can be replaced at 2 years - two months: four additional months of service, which saves millions of dollars by delaying the new satellite.
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