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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.
borrow from other tanks
They didn't do that.
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
have 1 tank that feeds 4 propellants?
Karma Whoring for Fun and Profit.
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!
Of course I haven't RTFA, but don't they connect the tanks on these things? That seems pretty obvious, and something they've been doing with airplane fuel tanks probably since they built the first plane with more than one tank.
-- Alastair
When I read the title I thought it meant saves millions OF HUMAN LIVES.
This is just moolah.
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
Propellors? On a satellite??
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).
Same propellant in each tank. But when one tank goes, the whole satellite goes. Note that they are only squeezing 6 months out of a 15 year satellite, or 3.3%. Not exactly planned obsolescence.
I think they they have 4 different thruster groups/tanks that can thrust the satellite in a multitude of *different* axises/directions. By carefully calculating when/where/how they apply the thrust (i.e. being more discerning - waiting for the satellite to reach specific positions and orientations) - they can better *balance* which thrusters (and therefore tanks) are used for a given maneuver - thus giving themselves (best-case) 4 times the life out of a satellite.
Y'know. $30 million?
Deleted
I'm wondering why they haven't started using ion drives on satellites. They would have to be significantly cheaper to launch and should last significantly longer, which should more than make up the cost of using newer technology.
Give it a serial number with many eights (ie: 88888888888888).
Paint it red.
Name it something with "Dragon."
etc...
*runs away*
The article claims that the process saved $60 million. However, according to the satellite life cycle they describe, it isn't a savings that was realized, but an unanticipated revenue above expectations. They extended the service life of the satellite, rather than helping it achieve its full lifespan.
If I am wrong, I apologize, but this seems to be what they were describing.
Mmmmmm... Bold, yet refreshing!
Dude, seriously.... Run a tube between them, the fuel will be equal in them all. WTFN? (What the F*** Nasa?)
) Human Kind Vs Human Creation
) It'd be interesting to see how many humans would survive to serve us.
Any attempt to reduce costs by extending the lifespan of printer cartridges is a violation of the DMCA.
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.
How about thruster modules which can attach to satellites with a standardized mounting system? Then you could extend satellite life by having the old module detach itself and re-enter the atmosphere, letting the new module attach itself in its place. Alternatively, make the standardized mounting capable of supporting at least two modules, so that the old one can stay on and do station-keeping, while the new module docks. Perhaps a ring around the satellite's waist that the modules can clamp themselves to? The thruster modules would depend on the satellite for long term power. The same link that supplies power could also transmit data.
Thanks, that sounds less like the "duh" comment I originally had. After all these years, I hope they are now launching systems with fuel balancing mechanisms in place and also a refueling dock. The dock would be just incase some drone can be launched from the ISS or a shuttle in the future.
LoB
"Anyone who stands out in the middle of a road looks like roadkill to me." --Linus
Pretty close yeah. Here is an article with a more detailed explanation.
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
That doesn't make sense. If pressure alone isn't enough to know, then a pressure and temp sensor on each tank should be enough to calculate the remaining fuel.
Wow, these d00ds must live in the stone age. This is the stupidest thing since I learnt about the discardable car. It was UAZ made in the USSR maybe in the 60's and had no way to add oil. The finnish army modified the car and some are still in service.
The superpowers are known for their grand efficiency...
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.
It should clearly reside in the "well duh" catagory.
Never ascribe to malice what can be adequately attributed to ignorance. -Napoleon
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.
------
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.
Remember that these are communications satellites.... And they last 15 years usually...
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.
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If only getting from LEO to geosync was that easy.
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
I read the headline and thought it meant it would save millions of people... Better imaging of flood areas, hurricane tracking, or something.
Imagine my disappointment when I discovered it meant dollars...
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.
Stop backing up your refutations of comments with facts, logic and comprehension. You're making us armchair engineers look bad ;)
My blog. Good stuff (when I remember to update it). Read it.
just keep track of how much fuel has been used up until now. duh!
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.
Use 1 tank?
Just don't try this without running Incident I & II first. Really.
deleting the extra space after periods so i can stay relevant, yeah.
Millions of what, satellite overlords?
I was flipping bits on an abacus, newb.
But.. but.. I need my 360 to play Viva Piñata!!! Can I still stay... please?
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 then split it back off to the engines so that it doesn't matter if one tank contains more propellant than another so long as the average pressure is sufficient... or you know, maybe even something ingenious like... oh, I don't know... valves? Either way, the only thing that matters at that point is that you have some propellant in at least one tank. Am I missing something here?
And before you say it, yeah, I know, valves can get stuck in the cold of space. So can the valve that allows ignition. Your point? :-)
Wow. I didn't know I could be that sarcastic.
Check out my sci-fi/humor trilogy at PatriotsBooks.
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
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.
Check out my sci-fi/humor trilogy at PatriotsBooks.
I think it's because you don't know how much is liquid and how much is gas. And you'd probably need more than one temp sensor to get an accurate idea of what's going on.
You're thinking small. Why miniaturize the laser, when we could instead enlarge the sharks? -John Searle
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. 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 have to take into account the temperature differences to ensure that fuel moves in the correct direction. Otherwise, a warmer fuel tank could end up sending fuel to a cooler fuel tank with exactly the same amount of fuel.
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Till bubbles get involved. When the tanks are full the tubes are full of fluid and equalize the fuel fine but at end of life your fuel can just be a big blob floating in the middle of the tank.
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?
How is that better than "if any one tank is empty or fails to perform we're fucked"?
I do that with my toner! I thought of it first, somebody needs to sign a check...
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.
So we're brilliant all of a sudden and use the same system that they use to get the fuel out of the tank in the first place.
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.
) Human Kind Vs Human Creation
) It'd be interesting to see how many humans would survive to serve us.
Unless the fuel tank has a membrane that has a pressurized gas on one side in order to maintain constant pressure on the fluid and prevent the formation of voids (aka; bubbles), such as my under-the-counter reverse osmosis water filter tank has in it.
9/11 Eyewitnesses to Explosive WTC Demolition 1 of 2
You are assuming that these old satellites actually have a physical connection between the tanks to balance the fuel load. If not, then a method to even it out (without some sort of pipe) is actually a very good idea.
Comment removed based on user account deletion
To my understanding, satellites are highly compact nuggets of streamlined function. Standardized mounting would waste space, add mass and another point of failure. Also, nobody would ever agree on what's the best way to mount stuff. You think aerospace engineers get out much?
Private space companies, who incidentally are booming and profitable with regards to satellite operations (because, unlike everything else done in space, they bring back real, measurable benefits to mankind), have great multi-million dollar incentives to keep costs down. You save the shareholders a million bucks with a bright idea? Congratulations, collect a $10,000 bonus. However, at NASA, the bureacracy exists to perpetuate itself and that does NOT happen by saving money, it happens by spending it. $10 million extra in operational costs is 10 million opportunities to buy the votes or publicity that they need to get their next $400 million mission-to-nowhere approved. That is why cost savings which would make this article seem like a footnote (gee, lets start with "Stop sending up shuttle missions since we know they are hideously expensive and of no scientific value whatsoever" and move on from there) will never, ever be approved.
Help poke pirates in the eyepatch, arr.
Please read Apollo 13 and then get back to us. They had just such a cross-connected system, and when one of their several oxygen tanks blew out, they lost all their O2, rather than just some of it.
No weapon in the arsenals of the world is so formidable as the will and moral courage of free men.-Ronald Reagan
Except of course that sending a person up there to rework the plumbing will cost about a trillion dollars, whereas given the that the hardware is already up there, already has a ridiculous four fuel tanks and when one is empty we fail design, and (I assume) already has the hardware to do the fuel balancing the complicated heating way it seems a cheap way to get an extra 6 months of service from an expensive asset.
even better - one big ass tank!
The article he refers to has a much better explanation than TFA.
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
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
I dont see why they dont have 1 big tank that can be shared. I mean all you need is hoses after that.
On the other hand I have no idea what the f*** im talking about. I've never even thought of building anything for space before.
The tanks can refuel each other, so at the beginning of the mission you can easily fix the issue, the problem here is that it is difficult to tell if a tank is at 10% or 5%, so measuring where the fuel needs to go is very tricky.
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When you're getting low on ammo, you shoot an armoury?
455fe10422ca29c4933f95052b792ab2
Are we talking about the "if one tank fails the other three will be okay and fully unable to position the satellite" kind of redundancy here? I don't really see any advantage of that over "if the one tank fails we'll be fully unable to position the satellite (while saving millions on three tanks and an expensive-as-fuck fuel balancing system)".
Please explain how it's possible to have -8 kilograms of fuel :P Anti-fuel perhaps?
The AACS key is NOT 0xF606EEFD628B1CA427BEA93A9CA9773F
That's definitely a more detailed article. I wonder why they couldn't store the fuel in a bladder, and have it squeezed out like a toothpaste tube, rather than having it sloshing all over the place in a tank. They would still use the Helium, but it would be easier to tell how much fuel is left.
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You mean create a single point of failure?
Yes, exactly, like when the Ubuntu install process HIGHLY RECOMMENDS that you overwrite the MBR with GRUB when you've put Ubuntu on a secondary hard drive.
Design principles: they don't apply to products that people recommend to me.
Apology to Ubuntu forum.
It boggles the mind that you kids just make shit up like that when a little googling will get you this: The first satellite, Sputnik, was launched October 4, 1957. It had no fuel.
Now get off my lawn. And no, you can't have your balls back, you damned kids!
-mcgrew
Right, and you kind of figure it would have to be flexible... because you sure as hell aren't going to have AIR bubbles leaking in from outside.
Do aerospace engineers get out much?
Who do I know who's an aerospace engineer? Hmmm. The keyboard player in my band. Does he get out much? He has a blonde hottie wife who has a bunch of hottie friends. And he's in high enough demand that he flies to gigs around the country.
That's why I said you would need valves to prevent backflow, and, ideally, sudden pressure loss sensors to cut off that tank just to be certain. Losing all your propellant because of a single tank failure just isn't a plausible scenario. Losing it because of a single hose failure in just the right spot is, but it would be anyway.
Check out my sci-fi/humor trilogy at PatriotsBooks.
Seems to me that you're either pumping liquid or you aren't. If it starts sucking air, you could detect that and route fuel from a different tank, then pump an equal amount of fuel from every other tank equal to the total amount of fuel expected in an average tank divided by the number of tanks. Over time that should average out to all tanks being equally full.
This just seems to me like designing a car with an engine that fails catastrophically if it runs out of fuel, and instead of fixing the engine design, putting in a cut-off to automatically shut down the distributor when the tank gets below a quarter tank.... It's a clever workaround for existing satellites, but it still seems more of a workaround than a feature.
Check out my sci-fi/humor trilogy at PatriotsBooks.
Yup. A failure in that single line is catastrophic, but so would be the same failure in the individual lines. If the probability of failure of a line during the product's life is n, then the probability of failure of at least one of k lines is k * n. Therefore, the single point of failure can be shown to have a substantially lower risk of failure than the multiple line design.
It's like hard drives. If you have one large disk with all of your content, you are less likely to lose data than if you have two disks in a RAID-0 striped array because the changes of each drive failing are about the same, so having two drives doubles your risk. Since loss of either disk will probably result in loss of all of the data in a striped array, you're better off with a single disk unless your only goal is to overcome throughput limitations.
Check out my sci-fi/humor trilogy at PatriotsBooks.
dgatwood, Sorry dude, but you really are so ignorant in this area that you should educate yourself a little before you start writing down your thoughts and embarrassing yourself... I used to work for MIT's Lincoln Labs on NOAA weather satellites and usually the designers of those things go to such exorbitant lengths to ensure redundancy that it is ridiculous, occasionally though one of them dies and needs to be replaced with some young punk fresh outa school, then his work is highly scrutinized by those that have been designing systems to withstand ionizing radiation (ever see what that does to a computer?), 500 degree temperature changes happening almost instantaneously, induced voltages that'd kill you if you were exposed to them and if they weren't handled properly, and I could go on and on... this problem is not nearly as simple as you make it out to be, so relax, realize for just one second that you do not know everything about it, and go back to playing WoW in your mom's basement.
>>The obvious solution would be to just combine the output of all of the tanks and then split it back off to the engines
>You mean create a single point of failure?
Well, that sure beats four single points of failure...
Because you obviously already understand this. (cough)
StoneCypher is Full of BS
It's in space. If it starts sucking vacuum, it's gonna break. Space makes things harder than just your car. Also, there are no service stations up there.
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