New Way of Extending Satellite Life Saves Millions 173
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."
Wow! What an innovative idea! (Score:5, Funny)
"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.)
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None of the above. Your post was just stupid.
This post, however, is insightful as fuck.
Re:Wow! What an innovative idea! (Score:5, Funny)
Re:Wow! What an innovative idea! (Score:5, Interesting)
Re:Wow! What an innovative idea! (Score:5, Informative)
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.
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You're right. It's not an obvious solution that has been overlooked. It's a terribly overly complex and non-obvious solution to a relatively simple problem---precisely what I'd expect from an industry with multimillion dollar toilets.
The obvious solution would be to just combine the output of all of the tanks and th
Re:Wow! What an innovative idea! (Score:4, Insightful)
You mean create a single point of failure?
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LoB
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Oh and more redundancy.
And possibly a little backup.
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Combining the output with a single unified fuel line would be a better idea than combining the tank. With one tank, if it ruptures, you're screwed. With four tanks and hardware to prevent backflow (either a traditional backflow prevention valve or a sensor coupled with a standard valve) all dumping into a single shared output line, you still get 3/4ths of your usable life if one tank fails.
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If you have four fuel tanks, you still have at least three other tanks. They estimate the amount of fuel in each fuel tank is estimated by measuring the pressure of the fuel inside the tank. However, this is affected by the temperature of the fuel tank (caused by the orientation of the Sun relative to the satellite, which changes as the Earth rotates each day).
Once they work out what amount of fuel remains in each fuel tank, they ha
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If it gets punctured or the control valve goes wonky, you lose all the fuel.
If you have four fuel tanks, you still have at least three other tanks.
So any reasonble person would suspect. But in the design that they used, according to a more informative article at http://www.eurekalert.org/pub_releases/2007-09/pu- era090507.php [eurekalert.org],
"The tanks are pressurized with the helium. If one tank runs out of fuel, the next time the valve in that tank is opened to ignite the rocket thrusters, the helium from that tank mixes with fuel going to the thrusters from the other tanks, preventing the thrusters from firing and shutting down the propulsion system."
In other words, in this design, if one tank empties completely, it screws up the other three thrusters. The way they did it, four tanks do not increase reliability, they actually increase the likelyhood of failure.
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MOD PARENT UP (Score:2)
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Re:Wow! What an innovative idea! (Score:5, Interesting)
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Re:Wow! What an innovative idea! (Score:5, Insightful)
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!
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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.
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It works prefectly well to get the fuel out and adjust the trajectory, since that is the purpose of the tank and it is used for that purpose without gravity as it is designed to. No gravity, no bubles and no issues that are caused by using 4 tanks instead of the 1 that is actually needed in the first place.
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I thought everybody knew that.
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Re:Wow! What an innovative idea! (Score:5, Funny)
Well, of course they didn't. That would have infringed on UbuntuDupe's patent.
Re:Wow! What an innovative idea! (Score:5, Funny)
NSS?! (Score:3, Interesting)
Seriously, who didn't learn the lesson of the limiting reagent in high school chemistry?
Re:NSS?! (Score:4, Funny)
Oh, great... so now Martin Marietta is gonna file a DMCA complaint and demand the arrest of...
Good Show in either case!
Not a limiting reagent (Score:2)
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My guess is future satelites will be built with (*GASP*) fuel gauges so that you don't have to have a freaking team of PHD guys trying to figure out which one will fail first and modeling how to use the other engines to compensate for the one that gets the most usage.
Damn, with a brain trust idea like this someone might even think to put aysemetric
Re:NSS?! (Score:5, Interesting)
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That's talking about interstellar space, of course, and here we're talking about a region which is comparatively packed with gases, from the Earth and don't forget the solar wind, which is particulate as well (not radiation).
There will always be some
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I'll concede you the density out there isn't quite zero, so you get some eventual decay... I have no idea what the time frame on that is though.
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The way I interpret what they are doing is more a matter of planning their usage of thrusters so all of the tanks run out at the same time. This is similar to some work I did in manufacturing where you would balance the usage of the various cutters swap
Now if they can just apply this to (Score:5, Funny)
Oh wait... who am I kidding...
It would work... (Score:5, Funny)
Oh wait... who am I kidding...
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"Affirmative. Logical. Logical. Logical. I have finished."
On second thought...
It's amazing that this was not done initially (Score:2, Insightful)
Re:It's amazing that this was not done initially (Score:5, Funny)
But this time it really is!
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Actually, yeah it is. Real world engineering is rarely as simple and black and white as the armchair variety.
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I think it's a trade-off between safety and predictability on one side and efficiency and progress on the other.
This is largely explained by the public attitude of both sides. To wit:
The soviets launched in secret. When they had a success, they shouted it from the rooftops. When they had a failure, they brushed it under the carpet. If Yuri Gagarin had died in his attempt to be the first man in space, I suspect they would have simply not told anybody and tried again the next week. Heck, by FAI [wikipedia.org] rules at the time, his flight shouldn't have counted, since he parachuted away from the spacecraft during reentry rather
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But obvious stuff like writing easy-to-understand, well-documented code... that's just expected, no matter how hard it is to do in practice.
sigh (Score:5, Informative)
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.
Re:sigh (Score:5, Insightful)
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Pumping fuel in a zero-gravity environment is not like pumping gas at your gas station. More often, a secondary substance is needed to force the fuel to move, like helium. That also has to be kept aboard in pressurized tanks in a liquid state, which brings about its own set of problems. You also have to take into account the differential heating/cooling that takes place as the satellite rotates and moves about in its orbit, which adds stresses to the system. And let's not forget this all requires more mass
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Re:It's amazing that this was not done initially (Score:4, Informative)
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.
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Satellites often rotate themselves using gyroscopes. Imagine a large spherical weight inside a square box, you spin the sphere clockwise, box rotates counterclockwise, once you are at the orientation you desire, stop the spherical weight, box stops rotating as well. Theres a bit more finesse with th
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Short answer : The pump will weight more than the wasted fuel, so your solution probably just shortened the lifetime instead of extending it.
And, that's assuming that the pump doesn't break.
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Um, connect the tanks? (Score:2)
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cause i could see them not doing it once.. then realizeing that was stupid and doing it for all the rest..
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No, you didn't RTFA, and it shows.
Apparently, they DO connect them together. However, being space, the tanks do not automatically equalize the liquid fuel, even though they are connected. This scheme involves using data about the temperature of the tank to guestimate how much fuel i
Spent some time with the IT guys (Score:4, Insightful)
Do they get half the difference? (Score:2)
Ion drives (Score:2)
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Misleading report (Score:2)
If I am wrong, I apologize, but this seems to be what they were describing.
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Economies of Scale: Standardized Thruster Module (Score:2)
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They could have built more expensive satellites in the first place, to last longer, but why bother? Communications technology changes a lot in 15 years, i wouldnt be surprised if many of the satelites up there werent even in active use for the full 15 years before being replaced with a more modern device.
Slashdot swamped with IDG Shills (Score:5, Informative)
coondoggie [slashdot.com]
inkslinger77 [slashdot.com]
narramissic [slashdot.com]
jcatcw [slashdot.com]
jpkunst [slashdot.com]
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...
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~S
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Obvious Ask Slashdot Post (Score:4, Funny)
Tricky business (Score:5, Interesting)
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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But it's my understanding that this technique is also useful on, um, more expensive birds. Your tax dollars at work.
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Unless one lighted one of the motors and accelerated the whole satellite long enough fo
The real problem: Getting NASA off their asses. (Score:5, Interesting)
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.
NASA doesn't have the incentive to do this (Score:2)
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That's too bad. I work for NASA...Draper Labs proposed doing the same thing with the International Space Station and we tried it out on the vehicle. Worked like a charm, desaturated the Control Moment Gyros and executed a 90 degree yaw maneuver to boot, no propellant used. Remarkable. It was a great tool to add to
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Why would NASA be involved? This change is for the geosync commo birds, which are commercial/private not NASA.
It's much more likely that NASA knew what is immediately obvious to me, and that you seem to have missed.
Estimating hydrazine mass by its thermal effects (Score:4, Informative)
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.
Re:Estimating hydrazine mass by its thermal effect (Score:2, Interesting)
Re:Estimating hydrazine mass by its thermal effect (Score:2)
Re:Estimating hydrazine mass by its thermal effect (Score:3, Informative)
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
Millions? (Score:2)
Imagine my disappointment when I discovered it meant dollars...
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yuck (Score:2, Funny)
So how does it work (Score:3, Funny)
Must be a pretty big nutshell to fit a commsat.
Wouldn't you want to replace old communication sat (Score:2)
Sounds familiar ... (Score:4, Interesting)
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 [af.mil].
Millions saved, by extending satellite life??? (Score:4, Funny)