×

Welcome to the Slashdot Beta site -- learn more here. Use the link in the footer or click here to return to the Classic version of Slashdot.

Thank you!

Before you choose to head back to the Classic look of the site, we'd appreciate it if you share your thoughts on the Beta; your feedback is what drives our ongoing development.

Beta is different and we value you taking the time to try it out. Please take a look at the changes we've made in Beta and  learn more about it. Thanks for reading, and for making the site better!

New Way of Extending Satellite Life Saves Millions

samzenpus posted more than 6 years ago | from the make-it-last dept.

Space 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."

cancel ×
This is a preview of your comment

No Comment Title Entered

Anonymous Coward 1 minute ago

No Comment Entered

173 comments

Wow! What an innovative idea! (5, Funny)

UbuntuDupe (970646) | more than 6 years ago | (#20498473)

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.

"A process for shifting resources from areas with a surplus to those that have run out ... on a satellite."

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.)

Re:Wow! What an innovative idea! (1, Informative)

Anonymous Coward | more than 6 years ago | (#20498497)

borrow from other tanks

They didn't do that.

Re:Wow! What an innovative idea! (5, Funny)

SomeJoel (1061138) | more than 6 years ago | (#20498525)

They didn't do that.

Well, of course they didn't. That would have infringed on UbuntuDupe's patent.

Re:Wow! What an innovative idea! (2, Insightful)

Anonymous Coward | more than 6 years ago | (#20498527)

(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.

Re:Wow! What an innovative idea! (4, Funny)

Timesprout (579035) | more than 6 years ago | (#20498533)

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.

Re:Wow! What an innovative idea! (0)

Anonymous Coward | more than 6 years ago | (#20498627)

Propellors? On a satellite??

Re:Wow! What an innovative idea! (4, Funny)

Ngarrang (1023425) | more than 6 years ago | (#20499021)

Propellors? On a satellite??
Yup, to beat against the ether. It is newest form of propulsion.

Re:Wow! What an innovative idea! (4, Interesting)

Chuckstar (799005) | more than 6 years ago | (#20498633)

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).

Re:Wow! What an innovative idea! (0, Troll)

Romancer (19668) | more than 6 years ago | (#20498715)

Dude, seriously.... Run a tube between them, the fuel will be equal in them all. WTFN? (What the F*** Nasa?)

Re:Wow! What an innovative idea! (2, Insightful)

Bartab (233395) | more than 6 years ago | (#20498985)

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.

Re:Wow! What an innovative idea! (-1, Flamebait)

CriX (628429) | more than 6 years ago | (#20499559)

A tube in zero G wouldn't do shit, smartypants. He was being sarcastic.

Re:Wow! What an innovative idea! (2, Informative)

Squalish (542159) | more than 6 years ago | (#20499907)

If the tubes are pressurized fluid fuel, then they will equalize perfectly well, gravity or no gravity.

Re:Wow! What an innovative idea! (2, Funny)

bbcisdabomb (863966) | more than 6 years ago | (#20499969)

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!

Re:Wow! What an innovative idea! (5, Informative)

Otter (3800) | more than 6 years ago | (#20498787)

Looking at the paper (linked in the article), they're doing that and then using differential heating of the tanks to shift the fuel to rebalance them.

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.

Re:Wow! What an innovative idea! (-1, Offtopic)

Anonymous Coward | more than 6 years ago | (#20499395)

If you're a fratboy with no life outside computer video games, GTFO.
If you think "strafe" is a synonym for "sidestep," GTFO.
If your first exposure to Bungie was from the Xbox 360, GTFO.
If you own an Xbox 360, GTFO.

Bandwagon jumpers are not welcome among real [imageshack.us] http://img518.imageshack.us/my.php?image=img2569sq 6.jpg [slashdot.org]">Mac http://img264.imageshack.us/my.php?image=img9205zl 3.jpg [slashdot.org]">users. Keep your filthy, beige [imageshack.us] PC fingers to yourself.

Re:Wow! What an innovative idea! (1)

Locutus (9039) | more than 6 years ago | (#20498815)

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

Re:Wow! What an innovative idea! (1)

Harmonious Botch (921977) | more than 6 years ago | (#20499857)

I hope they are now launching systems with fuel balancing mechanisms in place...
Ummm...how about just one fuel tank?

Re:Wow! What an innovative idea! (1)

Jeff DeMaagd (2015) | more than 6 years ago | (#20498919)

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.

Re:Wow! What an innovative idea! (4, Interesting)

griffjon (14945) | more than 6 years ago | (#20499081)

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"

Re:Wow! What an innovative idea! (0)

Anonymous Coward | more than 6 years ago | (#20500171)

just keep track of how much fuel has been used up until now. duh!

Re:Wow! What an innovative idea! (0)

Anonymous Coward | more than 6 years ago | (#20498975)

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...

Re:Wow! What an innovative idea! (2, Funny)

sentientbeing (688713) | more than 6 years ago | (#20499413)

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.

NSS?! (2, Interesting)

Dread_ed (260158) | more than 6 years ago | (#20498503)

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?

Re:NSS?! (3, Funny)

Penguinisto (415985) | more than 6 years ago | (#20498615)

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.

Oh, great... so now Martin Marietta is gonna file a DMCA complaint and demand the arrest of...

...oh, wait; this ain't the computer field we're talking here, so common sense actually applies. My Bad.

Good Show in either case!

/P

Re:NSS?! (1)

JamesP (688957) | more than 6 years ago | (#20498647)

Great!

Pray, please explain then, how would you control a satellite in outer space without using fuel.

Oh, and by the way, satellite orbits decay with time, so unless you don't want it to crash and burn, you need to push it back up again.

Re:NSS?! (4, Interesting)

Nyeerrmm (940927) | more than 6 years ago | (#20498779)

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.

Re:NSS?! (1)

tygt (792974) | more than 6 years ago | (#20499615)

Well.... let's not forget that even the "hard vacuum" of outer space contains something - I realize I'm being pedantic here, but [http://en.wikipedia.org/wiki/Vacuum [wikipedia.org]]:

even in interstellar space, where there are only a few hydrogen atoms per cubic centimeter
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 "friction" loss and so the orbit will eventually decay - just very gradually.

Re:NSS?! (2, Insightful)

Analogy Man (601298) | more than 6 years ago | (#20500299)

Thanks for the clarification. These thrusters adjust the orientation of the satellite. It is also for this reason that there are not fuel lines interconnecting these fuel systems. The additional tubing and failure modes would more than cancel any benefit.

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 swapped into a CNC machine so that the all the cutters would be on the same maintenance cycle. If one cutter did 80% of the work and needed to be replaced every 2 hours and the others lasted for a week, you would get much less throughput than if you off loaded some of the work of that cutter to other perishable tools.

Not a limiting reagent (1)

everphilski (877346) | more than 6 years ago | (#20498677)

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.

Re:Not a limiting reagent (0)

Anonymous Coward | more than 6 years ago | (#20499667)

He was not referring to an actual chemical limiting reagent. The empty tank is the limiting reagent. When one tank is gone, the whole thing, in effect, is gone. It's an analogy, see?

Re:NSS?! (0)

Anonymous Coward | more than 6 years ago | (#20498863)

The lack of respect for feats of engineering is a little surprising on slashdot. Though I suppose it ties in with the general attitude for other subjects nicely enough. ;)

They're extending things about six months. From TFA:

[The satellites] generally have a 15-year lifetime, bringing in $5 million to $10 million a month in revenue.

Which would imply that the achievement here is sucking out the last 3% or so of the fuel, spread over four tanks, no one of which can under-deliver fuel early.

Having an idea is easy. Yet somewhere in between the base design, which was 97% efficient in fuel use, and the fairly obvious idea of "Wouldn't it be better to be 100% efficient?" was that messy implementation step, which was a non-obvious feat of engineering.

Now if they can just apply this to (4, Funny)

the_skywise (189793) | more than 6 years ago | (#20498531)

ink jet cartridges...

Oh wait... who am I kidding...

It would work... (5, Funny)

CaptainPatent (1087643) | more than 6 years ago | (#20498607)

Now if they can just apply this to ink jet cartridges...
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!

Re:It would work... (3, Funny)

Anonymous Coward | more than 6 years ago | (#20498649)

Maybe it's Vulcan pr0n?

Re:It would work... (0, Offtopic)

rootofevil (188401) | more than 6 years ago | (#20498653)

there was a kid in highschool that went through a couple of color cartridges printing out his collection of pictures. which he kept in a binder. that he took to school with him. the binder was a good 4 inches thick and weighed more than 10 pounds. dude carried it with him every day.

Re:It would work... (0)

Ironsides (739422) | more than 6 years ago | (#20499271)

I just tried it out and your idea works well, but I'm wondering why my pr0n printouts have green nipples!

Maybe because you printed out a picture of a naked star trek alien? I'm told female Orion's [wikipedia.org] are quite the nymphomaniacs.

Remember Kids: (0)

Anonymous Coward | more than 6 years ago | (#20498723)

Any attempt to reduce costs by extending the lifespan of printer cartridges is a violation of the DMCA.

why not a brlliant idea..... (0, Redundant)

downix (84795) | more than 6 years ago | (#20498547)

have 1 tank that feeds 4 propellants?

Re:why not a brlliant idea..... (0)

Anonymous Coward | more than 6 years ago | (#20498991)

"have 1 tank that feeds 4 propellants?"

Great, now try to balance the thing.

Re:why not a brlliant idea..... (1, Funny)

Anonymous Coward | more than 6 years ago | (#20499545)

"have 1 tank that feeds 4 propellants?"

Great, now try to balance the thing.
Maybe put it in the middle? I mean, come on, it's not like this is rocket science.

Oh, wait...

It's amazing that this was not done initially (2, Insightful)

iamacat (583406) | more than 6 years ago | (#20498561)

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!

Re:It's amazing that this was not done initially (4, Funny)

GweeDo (127172) | more than 6 years ago | (#20498679)

"It's not a rocket science!"

But this time it really is!

Re:It's amazing that this was not done initially (2, Informative)

DerekLyons (302214) | more than 6 years ago | (#20498707)

But pipes can fail, so can pumps and so can fuel measuring devices (and all the associated power and control hardware). Thus the choice in the past has been to limit possible points of failure at a potential cost in satellite life.
 
 

It's not a rocket science!

Actually, yeah it is. Real world engineering is rarely as simple and black and white as the armchair variety.

Re:It's amazing that this was not done initially (1)

iamacat (583406) | more than 6 years ago | (#20498745)

If a failure happens, we are no worse off than the current situation. So what's the catch?

Re:It's amazing that this was not done initially (1)

compro01 (777531) | more than 6 years ago | (#20498893)

no, if a failure in terms of a clogged fuel line happens, it is not going to be when we expect it, unlike the known-and-planned-for "out of gas" failure, thus will definitely be worse.

Re:It's amazing that this was not done initially (1)

Bazer (760541) | more than 6 years ago | (#20499103)

From what I recall, this mindset was the reason why the ol' Russkies were ahead of the US space program in terms of technology. Development of rocket engines and Buran come to mind as an example. I think it's a trade-off between safety and predictability on one side and efficiency and progress on the other. Disclaimer: IANA Rocket Scientist or Historian.

Re:It's amazing that this was not done initially (2, Insightful)

nsayer (86181) | more than 6 years ago | (#20499783)

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 than land inside it. The soviets didn't actually land inside their spacecraft until Voskhod 1, in October of 1964, by which time NASA's Mercury project had been over for more than a year. They got away with it because.... wait for it.... nobody was watching.

By contrast, NASA performed all of their activities totally in the public eye. As such, every failure was a public embarrassment and the loss of an Astronaut would have been totally unacceptable. The Apollo 1 fire kept NASA out of orbit for a year and a half while they investigated the cause(s) and fixed a bunch of problems.

Re:It's amazing that this was not done initially (1)

DerekLyons (302214) | more than 6 years ago | (#20500409)

If you *increase* the chance of a failure happening (which you do by adding the fuel transfer hardware, controls, etc...), then you are *worse* off than the current situation. That's the catch.

Re:It's amazing that this was not done initially (2, Interesting)

ChrisMounce (1096567) | more than 6 years ago | (#20498973)

I think an analogy to programming styles is appropriate here. Clever code is often lauded, just because so-and-so managed to write a one-liner that does <insert complex task here>. People compete to be clever (see those obfuscated C contests [ioccc.org]). Clever is impressive.

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 (4, Informative)

everphilski (877346) | more than 6 years ago | (#20498797)

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.

Re:It's amazing that this was not done initially (1)

Billosaur (927319) | more than 6 years ago | (#20498989)

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 for the satellite, increasing the cost of the satellite and the cost of launching it.

So, as others have said, this is rocket science.

Re:It's amazing that this was not done initially (1)

iamacat (583406) | more than 6 years ago | (#20499431)

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.

Re:It's amazing that this was not done initially (3, Informative)

IndustrialComplex (975015) | more than 6 years ago | (#20499959)

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.

Um, connect the tanks? (1)

AJWM (19027) | more than 6 years ago | (#20498569)

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.

Re:Um, connect the tanks? (1)

Amouth (879122) | more than 6 years ago | (#20498699)

it might have occured on the second plane with more than 1 fuel tank..

cause i could see them not doing it once.. then realizeing that was stupid and doing it for all the rest..

Re:Um, connect the tanks? (1)

harrkev (623093) | more than 6 years ago | (#20499129)

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.

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 is in each tank, and using selective heating to distribute the fuel around.

Re:Um, connect the tanks? (0)

Anonymous Coward | more than 6 years ago | (#20500125)

NO cause, fuck that ! The plane is going to fall sideways in the trenches. TFA is a miscreant. Not gonna happen in your lifetime, buddy. and even so, there is no chance you'd even survive the sudden stop. So, dream on diamond. Sheesh, you'd think people on this site would have figured that out by now.

Disappointed (0)

Anonymous Coward | more than 6 years ago | (#20498593)

When I read the title I thought it meant saves millions OF HUMAN LIVES.

This is just moolah.

Spent some time with the IT guys (4, Insightful)

techpawn (969834) | more than 6 years ago | (#20498613)

It really sounds like they just applied load balancing to the fuel tanks...

Poorly described - I think they mean... (1)

bradgoodman (964302) | more than 6 years ago | (#20498681)

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.

Re:Poorly described - I think they mean... (1)

bradgoodman (964302) | more than 6 years ago | (#20498773)

P.S. These are existing units in space - can't do anything about the tanks not being interconnected now!

Ion drives (1)

Rolgar (556636) | more than 6 years ago | (#20498691)

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.

Re:Ion drives (1)

TheRaven64 (641858) | more than 6 years ago | (#20498865)

Ion drives are much heavier than chemical drives (which are basically just bottles). This is not a problem for long range systems, where the reduction in propellant mass more than makes up for it, but it might be on satellites, where the engines are only to make minor orbital corrections, and are a tiny part of the mass. You'd probably also need to add more solar panels if you wanted to be able to power an ion thruster. You'd also complicate the orbital calculations a lot (ion thrusters provide small amounts of thrust for a long time, while chemical ones provide a lot of thrust for a short time, which is easier to compute since you can approximate it to an instantaneous impulse).

How to Prolong the Life of a Satelite (0, Offtopic)

doyoulikeworms (1094003) | more than 6 years ago | (#20498701)

Give it a serial number with many eights (ie: 88888888888888).
Paint it red.
Name it something with "Dragon."
etc...

*runs away*

Misleading report (1)

pjt48108 (321212) | more than 6 years ago | (#20498705)

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.

Re:Misleading report (1)

Chris Burke (6130) | more than 6 years ago | (#20498821)

Helping the satellite reach its full life span, extending the life span of the satellite... what's the difference? Either way the result is the broadcast companies have to launch new satellites less often, and thus they save money.

Re:Misleading report (2, Insightful)

Rolgar (556636) | more than 6 years ago | (#20498935)

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.

Economies of Scale: Standardized Thruster Module (1)

StCredZero (169093) | more than 6 years ago | (#20498805)

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.

Re:Economies of Scale: Standardized Thruster Modul (1)

Bert64 (520050) | more than 6 years ago | (#20499871)

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.

Slashdot swamped with IDG Shills (5, Informative)

Frosty Piss (770223) | more than 6 years ago | (#20498825)

Looks like IDG (ComputerWorld, ITWorld, NetworkWorld...) is really hitting Slashdot HARD, either that or they have a deal with Slashdot. Here's a partial list of the shills that regularly show up and have almost 100% article acceptance rates:

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...

Re:Slashdot swamped with IDG Shills (2, Interesting)

Soporific (595477) | more than 6 years ago | (#20498963)

Well I would take jpkunst out of that list. But the others yeah, 30 stories with 3 comments? I don't get it either.

~S

Re:Slashdot swamped with IDG Shills (1)

jjrockman (802957) | more than 6 years ago | (#20499131)

We get it. How many articles are you going to infect with the same comment?

Re:Slashdot swamped with IDG Shills (0)

Anonymous Coward | more than 6 years ago | (#20499393)

Maybe this should be a disclaimer in EVERY IDG story? Truth in advertising? Would your opinion be different if it where MICROSOFT shills? Of course it would. Mr. Double Standard IDG Fanboi.

Re:Slashdot swamped with IDG Shills (0)

Anonymous Coward | more than 6 years ago | (#20499795)

Thats not an issue. No one anyways reads the articles.

Obvious Ask Slashdot Post (4, Funny)

Anonymous Coward | more than 6 years ago | (#20498881)

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.

Tricky business (5, Interesting)

linuxwrangler (582055) | more than 6 years ago | (#20498885)

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.

Re:Tricky business (1)

PIBM (588930) | more than 6 years ago | (#20499045)

From TFA, satellites cost 100M and launching costs can reach that number, so if it does, you look at 200M for 15 years of work, which happens to be only 1.1M per month, not millions per extra months of life.

While their income is higher than this per month (which has to be!), they would have sent another satellite if they had not extended those satellites live..

Re:Tricky business (1)

linuxwrangler (582055) | more than 6 years ago | (#20499581)

I didn't say cost, I said "worth". Using (revenue-cost)/lifespan, each extra month is worth millions even for relatively inexpensive commercial satellites.

But it's my understanding that this technique is also useful on, um, more expensive birds. Your tax dollars at work. :)

Re:Tricky business (1)

morgan_greywolf (835522) | more than 6 years ago | (#20499307)

Why not use a float system like a car? Only one designed to work in microgravity?

Re:Tricky business (2, Informative)

Anonymous Coward | more than 6 years ago | (#20499625)

Nothing floats in microgravity. You can freely mix gases, liquids and solid materiials to the limits that surface tension allows. Watch this NASA video about liquids and gases in microgravity [youtube.com], consider that a number of fuel drops of various sizes may be bouncing around the fuel tank, possibly mixed with helium bubbles (used to pressurize some fuel tanks), and tell me what is supposed to float where and in which direction.
Unless one lighted one of the motors and accelerated the whole satellite long enough for all the fuel to coalesce on one side of the tank, that's just not going to work.

The real problem: Getting NASA off their asses. (5, Interesting)

dougwhitehead (573106) | more than 6 years ago | (#20499225)

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.

Re:The real problem: Getting NASA off their asses. (1)

Ollabelle (980205) | more than 6 years ago | (#20499575)

Someone please mod this man up! He understands government contracting.

Estimating hydrazine mass by its thermal effects (4, Informative)

Cliff Stoll (242915) | more than 6 years ago | (#20499693)

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.

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 ... 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.

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 (2, Interesting)

NoisySplatter (847631) | more than 6 years ago | (#20499953)

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.

Re:Estimating hydrazine mass by its thermal effect (1)

PitaBred (632671) | more than 6 years ago | (#20500035)

Stop backing up your refutations of comments with facts, logic and comprehension. You're making us armchair engineers look bad ;)

Millions? (1)

Bazman (4849) | more than 6 years ago | (#20499909)

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...

Re:Millions? (1)

owlstead (636356) | more than 6 years ago | (#20500039)

Yeah, I had the same thing. I thought it was weird when I read the headline. Maybe some all-important weather or communications satellite? Somehow I feel suckered in, I probably wouldn't have read the summary if the headline included " of dollars" at the end. And the only reason I joined in the discussion was to say this. You just beat me to it though, and I'm freshly out of mod points :(

Re:Millions? (0)

Anonymous Coward | more than 6 years ago | (#20500165)

Well, it could save lives -- older imaging satellites used for tracking hurricanes, etc, could potentially use this technique.

So how does it work (2, Funny)

Kelz (611260) | more than 6 years ago | (#20500219)

Outside of a nutshell?

Must be a pretty big nutshell to fit a commsat.

Wouldn't you want to replace old communication sat (2)

asm2750 (1124425) | more than 6 years ago | (#20500287)

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.

Sounds familiar ... (3, Interesting)

PhxBlue (562201) | more than 6 years ago | (#20500297)

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].

Solution... (0)

Anonymous Coward | more than 6 years ago | (#20500365)

Use 1 tank?
Load More Comments
Slashdot Account

Need an Account?

Forgot your password?

Don't worry, we never post anything without your permission.

Submission Text Formatting Tips

We support a small subset of HTML, namely these tags:

  • b
  • i
  • p
  • br
  • a
  • ol
  • ul
  • li
  • dl
  • dt
  • dd
  • em
  • strong
  • tt
  • blockquote
  • div
  • quote
  • ecode

"ecode" can be used for code snippets, for example:

<ecode>    while(1) { do_something(); } </ecode>
Sign up for Slashdot Newsletters
Create a Slashdot Account

Loading...