Hack in Space

MelloDawg writes: "From the press release: NASA's Far Ultraviolet Spectroscopic Explorer (FUSE) spacecraft, which some had given up for dead in December after critical guidance components failed, was returned to full operations when the team developed an innovative new guidance system. The system uses a complex new set of procedures that lets controllers use electromagnets in the satellite to push and pull on the Earth's magnetic field. Details of the mission are online."

Comments

Go NASA geeks!!!

[mu_wtfo]

It's things like this that really make me proud of our space program. Sure, it's a little tiny thing, we now have one less dead satellite, but that was a beautiful solution, and it's good to know that these folks are still there thinking stuff up.

The Real Deal

[cybermage]

Pretty clever hack. Every time I read about real scientists pulling off neat things like this, I get more and more disgusted with people who simply reboot a server whenever it hangs because it's easier than actually thinking about what the problem is and how to fix it.

Re:The Real Deal

[fahrvergnugen]

Don't be ridiculous. I can tell you that in IT, this line of thinking will get you fired quickly.

Most often, if a system breaks in a production environment, it's imperative to get a it working again as fast as possible. Treating the symptom is paramount in a high availability situation, and while finding and resolving the cause is of course important, it takes an immediate back seat to getting the system back into production. If you can do both at once then that's grand. If not, then you restart the daemons or reboot the server once you've deemed it safe to do so.

Then, armed with log files and information gathered while the system was on error, you can go back through and trace the cause. Even better, you can duplicate the issue on a staging server. What you do NOT do is leave the system down for any reason one second longer than you have to, no matter how much the urge to tinker grabs you.

On the other side of the coin, diagnosing a problem on trivial or near-trivial system is a waste of your valuable time. Why the hell, except for fun, would you diagnose a BSOD issue on a secretary's computer when you could just back up her home directory, restore an image, then restore her personal files?

Obviously, every situation is different, but there are times when inexperienced techs will spend a day searching for the cause of a trivial problem instead of getting back to work.

Taking the time to root out a deep problem instead of just hitting the reset button is most often a luxury.

Re:The Real Deal

[Spencerian]

Some major operating systems (hint-it ain't Windows) lends itself to troubleshooting and repair in a little over 1 hour. And, yes, I -am- in IT and have been for some time.

Some operating systems don't suffer "file rot" like Windows where the OS becomes so decrepit that it HAS to be reimaged after only a few months.

Sure, experience counts in this (most MCSEs aren't worth the paper they're printed on since they lack true field experience), but, honestly, an operating system shouldn't bugger out at the frequency that Windows does (pick one, even XP, which I watched BSOD on national TV a few times recently) anymore than a car does.

Considering that NASA likely makes their OWN operating systems or variants of UNIX to handle probes lends more to their skill when the chips are down/burned/otherwise offline.

I'm not trying to flame, but this "reimage" mentality in Windows IT always chaps my ass. UNIX users look at us as if we grew a third eye for such procedures. It's easy to reimage a secretary's system, but some computer users have more complex environments that "cloned OS"s don't cover. Ask a specialized prepress or scientific user. Recovery and redundancy measures are needed, but your example doesn't cover these kind of users.

Re:The Real Deal

[gol64738]

haha, look at the difference between a unix admin and an NT admin.

you see, in the NT world, resetting the system DOES fix the problem (the problem being that the system has been up too long and needs a reboot). but in the UNIX world, if a problem develops, you normally need to look into it a little deeper and fix it so it doesn't come back and haunt you.

Re:The Real Deal

[SCHecklerX]

I'm glad I'm not the Network Security Analyst at your company.

The title

[pcbob]

made me proud of fellow lumberjacks. Imagine, hacking trees where no trees exist (sort of like BC, after clearcutting). Afterall, that is what all we Canaduhians think aboot, right :)

Finally some good news

[Zarathustra.fi]

I admit, it's an excellent hack.

But on the other hand, it's hard to forget what NASA has been doing for the past few years. Failures and mishaps. Bugs in software. Human errors. In critical projects, in times when funding is already really hard to get.

Luckily this time, the engineers had the means and actually got something fixed - but most of the recent news have been pretty much from the opposite end of the happiness scale. Too bad this wasn't a Mars probe - it would've had a tremendous PR value for the whole Mars exploration concept.

So....

[Ooblek]

Did they keep the ICBMs secret this time, or did it go haywire and start targetting the US again? Someone call Clint Eastwood and tell him to pack an overnight bag.

Re:NASA these days

[PhoenixK7]

Everyone seems to think that since many of the outward looking missions are having trouble that NASA isn't really doing much, check out all the reasearch thats being done on our actual planet. NASA has been collecting huge amounts information about Earth's atmosphere, oceans and land, and they've been doing important analyses. I'd suggest you check out places like:

earth.nasa.gov
earthobservatory.nasa.gov
terra.nasa.gov
data assimilation office

and for image products:

visibleearth.nasa.gov

NASA does alot of interesting earth science too!

So when it broke the first time...

[Anonymous Coward]

... did they say it blew a FUSE?

Re:So when it broke the first time...

[Phil Karn]

Yup. Believe it or not, spacecraft do have fuses. Obviously they can't be replaced when they blow, but by blowing they can isolate a failed module that might otherwise kill the entire spacecraft.

Where to put angular momentum

[Animats]

This is indeed neat.

A basic problem in satellite stabilization is how to get rid of unwanted angular momentum. There are a few options.

You can throw away something. Usually this is reaction mass from a small rocket, or just compressed gas. Weights on the ends of cables that unwind and break free have been used to despin satellites.

You can store angular momentum in an inertia wheel, which is a flywheel on a motor. This doesn't get rid of angular momentum; it just stores it as long as you keep the wheel spinning. Eventually, you hit the maximum motor speed and can't do anything more in that axis. So it's also necessary to have some way to drain off angular momentum, even if very slowly.

You can couple to a gravity gradient. This is done with a long pole aimed towards a nearby planet. The difference between the gravity at the ends of the pole is tiny, but enough that if you get the thing pointed down and stable, it usually stays that way. Only good for one axis, of course.

You can couple to a planetary magnetic field, like these guys are doing. Again, only good for one axis, but it's a different one than the gravity gradient. It's a weak effect, but stronger than the gravity gradient.

You can put out sails and get reaction forces from solar energy. This gets talked about a lot, but isn't done much.

All of these are known techniques. It sounds like this satellite had four inertia wheels and an electromagnet for torquing against a planetary magnetic field. The plan was presumably to maneuver with the inertia wheels, and slowly drain off unwanted angular momentum with the magnetic torquer.

With two inertia wheels down, there are still three torquing devices available, so control of orientation is theoretically possible. Tough, but possible. It's impressive that they made it work.

Re:Where to put angular momentum

[fwc]

This technology is also being used (with great success) on the Amateur Radio satellite AO-40 which was on Slashdot a while back.

Specifically, it was used to de-spin the satellite from almost 18 RPM down to the desired 5 RPM.

Some more relevant quotes I found while looking around on the web about AO-40's system:

From http://www.amsat-dl.org/journal/adlj40ge.htm

Magnetorquer In the satellite, several electro-magnets, also named magnetorquer, are distributes that can be used in the interplay with the Earth's magnetic field close to perigee for the attitude-control of the satellite. The satellite acts as the rotor of an electric motor while the magnet-field of the Earth forms the stator. The process of this movement is named as magnetorquing. With the magnetorquing, the flight-attitude of the satellite and the spin-speed can be changed during perigee-passes.

From http://www.rac.ca/spacenws.htm:

The onboard magnetorquing system--which consists of solenoid coils--makes use of Earth's magnetic field to control the spacecraft's spin and orientation. Magnetorquing is most effective when Earth's magnetic field is strongest, so it typically only takes place at perigee--when the satellite is closest to the Earth. Ground controllers have been making incremental adjustments during each perigee.

I also remember someone saying that this was somewhat "experimental" on AO-40. I can't find a quote though...

I agree fully that it's good to see the NASA engineers thinking "Well it's broke, we can't send someone up to fix it, so what can we do to make it work?" What I would like to know is who came up with the original idea (pre AO-40, or this satellite). It sure doesn't seem like the type of thing which I would have thought about when trying to figure out how to control the attitude of a spacecraft.

Re:Where to put angular momentum

[iangoldby]

Thanks for that. One question though. Where does the unwanted angular momentum come from? I would have expected that once things have settled down after release of the satellite, there would not be much in the way of sources of angular momentum to deal with. The impact of dust might possibly add some, but wouldn't this be negligible? I can't think of any other sources off the top of my head. Induced currents and magnetic fields would tend to damp any rotation. What am I missing? Maybe this satellite is in low-earth orbit and being 'buffetted' by the upper atmosphere...?

Re:Where to put angular momentum

[Gino]

All of these are known techniques. It sounds like this satellite had four inertia wheels and an electromagnet for torquing against a planetary magnetic field. The plan was presumably to maneuver with the inertia wheels, and slowly drain off unwanted angular momentum with the magnetic torquer.

In most cases at least 3 single axis magneto-torquers are provided, one per axis and normally one extra for redundancy. They are indeed used to reduce body angular rates and to control the wheel angular momentum. The reaction wheels (or inertia wheels) of course are limited to a maximum speed and to avoid wheel saturation the magneto-torquers are used to 'dump' some excess angular momentum.

With two inertia wheels down, there are still three torquing devices available, so control of orientation is theoretically possible. Tough, but possible. It's impressive that they made it work.

Actually, in smaller LEO (Low Earth Orbit) satellites this technique has been used for years to facilitate orientation control. It is normally used to reduce the spacecraft angular rates directly after separation from the launch vehicle. Using the magneto-torquers and a magnetometer monitoring the earth's magnetic field, the spacecraft can be controlled into a stable state with the minimum of hardware and with relatively simple control algorithms.

The idea is to get the spacecraft into a stable, known state (either earth pointing or aligned with the earth's magnetic field) before the more complex systems are powered and tested. You need to be sure your star camera, reaction wheels, propulsion systems and all the other cool hardware is in a nominal state before you enable the complex control algorithms required for more accurate orientation control.

The first satellite I've worked on we could not afford the more expensive magneto-torquers (compact electro magnetic rods) and instead opted for a self made magnetic coil without the assistance of ferrite material. Basically just a very long copper wire rolled into a coil and fixed to the frame of the solar panel (one coil per axis). Crude, but it had the desired effect!

What is really impressive is that they've managed to achieve this level of pointing accuracy with a system intended to achieve only basic orientation control and for desaturation of the reaction wheels.

Re:Where to put angular momentum

[Gino]

You have to know that not all satellites have their own dedicated launch vehicle with a perfectly controlled release mechanism - first by the last stage of the launch vehicle and then by the S/C itself.

In fact, the majority of satellites share a ride with other satellites. The satellites are in fact clamped to the last stage of the launch vehicle. At the moment of separation so called piro bolt cutters (in fact an anvil propelled by a small amount of explosive to cut through the bolts) will cut through the bolts fixing the satellite to it and a passive spring loaded mechanism (in most cases) will slowly and safely push the satellite on its way.

...once things have settled down after release of the satellite...

It is this initial release from the last stage that causes the initial angular momentum and there is nothing but these control mechanisms on the satellite to help 'things to settle down'.

Re:Where to put angular momentum

[Skuld-Chan]

Some sattelites you don't want to de-spin - like phase 2 and phase 3 sattelites which spin with the earth (or at least they seem to). Of recent concern is AO-10 which apparently is de-spinning by itself. Actually I don't think anyone is too worried about AO-10 anymore since it is a sattelite literally plagued with problems - but it still works! (when its in sunlight that is). But you read about what guys did to get AO-10 and AO-40 running again its pretty amazing nasa like stuff.

Read all about it - here

Re:Where to put angular momentum

[heikkile]

Magnetorquer [...]for the attitude-control of the satellite.

Do they work on girlfriends as well?

Re:Where to put angular momentum

[Alsee]

Magnetorquer [...]for the attitude-control of the satellite.
Do they work on girlfriends as well?

This has been an extremely dificult question to answer. It could only be tested by someone who has one of each.

-

Re:Where to put angular momentum

[code_rage]

Good question. Here are a few disturbance forces and moments which perturb the trajectory and attitude of satellites. In all cases, we are talking about very small forces acting over long periods of time.

- Aerodynamic drag. Most satellites have all sorts of things protruding into the breeze: solar arrays, antennas, instrument booms, thermal radiators, and so on. If these protuberances are not symmetric with respect to the center of mass, then one side is pushed more than the other.

- Gravity gradient. If a spacecraft (SC) is designed to maintain a fixed orientation wrt Earth, then the designers may take advantage of this to help stabilize the SC, as has been mentioned. For maneuvering vehicles like Hubble, Ikonos etc, the GG moment on the SC varies according to the attitude. There are also higher-order gravity terms due to Earth oblateness, mass concentrations and so on. The GRACE spacecraft pair will be mapping those 'mascons' in great detail; there was something recently on AvWk about this: http://www.AviationNow.com/content/publication/aws t/20020304/aw56.htm

- Drag within the momentum wheels and other moving appendages (antennas, cameras) will tend to torque the SC over long periods of time. Probably a *very* small contribution, unless there is a malfunction in the mechanisms.

- Slow leaks of propellant, battery gases, pressurants, coolants, etc. Early in the mission, possibly even material outgassing, though generally a thermal vacuum cycle is supposed to bake this stuff off prior to launch.

- Propulsive maneuvers which raise, lower, or change the orbit plane. Usually, the propulsion force vector does not align perfectly through the center of mass. To account for this, the SC is steered to minimize the propulsive moment (think Shuttle using a single OMS engine, there is a large offset), but this steering is imperfect.

- External forces from space tethers, applied at the point of attachment to the SC. (Not an issue for FUSE.) Aero drag, gravity gradient, and electrodynamic forces can apply to the tether.

- Light pressure, Solar wind could be disturbances to consider in deep space. They're probably too small to worry about in Earth orbit.

There might be some others I've forgotten. There are some good books out there on SC design, you could search ieee.org or a technical library.

Most of the other disturbances (thermal, e.g. early Hubble solar array problem) tend to be random in direction, and would not therefore tend to affect steady state angular momentum.

Nice Hack, HAMs do it for years

[schimmi]

Using the Earth magnetic field is something used in Amateur radio satellites since many years.

NASA's troubles

[colmore]

First off bravo to the NASA geeks. I always find it truly heartening when they pull these last minute hacks off. They don't really need to. I hadn't even heard about this one breaking, it wasn't that much of a PR problem. I think the only reason they really bothered is because, like any good geeks, this is their toy, and they love it too much not to try.

Second, to people bemoaning the absense of mars missions and moon bases. Why go? Can we learn so much more by sending people that it justifies the risk and cost of doing so? These are the questions being asked. And if you think this means our motives for going to space aren't pure, think about this: would we have gone to the moon had the Russians not been trying to beat us there?

I think the best way to get American astronauts on Mars today would be to convince Bin Ladin to start a space program.

I for one wonder if NASA has perhaps outlived its usefulness. Could it perhaps persist as a regulatory body, overseeing commercial space ventures, and allowing all-to-scarce public research money to go to other areas?

The mission to Mars sounds even less appealing once you consider how much cancer / AIDS / environmental / fusion / fuel cell / quantum computing / immortality / (name your favorite project) research it would replace.

Obviously the answer is more funding for public research, but then, does anyone really see that happening?

Re:NASA's troubles

[Rogerborg]

• to people bemoaning the absense of mars missions and moon bases. Why go?

We choose to go to the moon. We choose to go to the moon. . . . Not because it is easy, but because it is hard. . . . Because there is new knowledge to be gained. We shall send to the moon--240,000 miles away--from the control station in Houston, a giant rocket more than 300 feet tall, made of new metal alloys, some of which have not yet been invented . . . on an untried mission . . . on the greatest adventure.

Now, I'm a pretty cynical old bastard, but those words, nearly forty years on, still choke me up. To me, the defining quality of humanity is that our reach can exceed our grasp.

It's impossible (I think) to justify space exploration in any rational or economic terms. But if "because it's there" isn't justification enough, then that's a sad indicator we have become society of navel gazers and bean counters. And history shows us that societies only go one way once they've reached that stage.

You're right that the space race was based on competition. But I believe that still applies, and if we no longer want to compete, sooner or later we will be superceded by a society that does.

Re:NASA's troubles

[Shivetya]

"The mission to Mars sounds even less appealing once you consider how much cancer / AIDS / environmental / fusion / fuel cell / quantum computing / immortality / (name your favorite project) research it would replace."

Actually its more appealing because of just how much it could benefit these areas of research. Don't forget that the first American space program that eventually sent man to the moon was the basis for many technologies we take for granted today.

There is reason to believe that the obstacles overcome to support man living on the moon or venturing to Mars would also produce such technological findings that many seemingly unrealated areas would benefit.

I thing power production, the environment, and manfucturing would be the 3 key areas of benefit, and from them others areas would benefit as well.

Re:NASA's troubles

[ONOIML8]

"The mission to Mars sounds even less appealing once you consider how much cancer / AIDS / environmental / fusion / fuel cell / quantum computing / immortality / (name your favorite project) research it would replace.
"

I think you miss an important effect of exploration such as this. Sometimes it's not the destination, it's the journey.

As someone else mentioned, we gained as much or more in "other" areas as we did actually achieving the goal of reaching the moon. Some of the research that was done to get us to the moon was useful to us here on earth directly. Other tidbits were byproducts of that.

But your comment is a bit like saying that while you would love to visit the UK someday you can't right now because you have laundry to do. Don't put your life on hold just to do the laundry, live a little. Pack up some of that laundry and do it with you on the way.

Re:NASA's troubles

[Darth Yoshi]

Second, to people bemoaning the absense of mars missions and moon bases. Why go?

I think we can mark the beginning of the end of the human spirit when the majority of people say, "Why bother."

Re:NASA's troubles

[Thing 1]

And history shows us that societies only go one way once they've reached that stage.

I agree with everything you're saying, just wanted to add an aside: who writes the history? The society that supercedes.

I'm actually very worried about our society coming to the stage of "history." The US government is passing weirder and weirder laws, which the people will rebel against, civil disobediently at first.

I liken your "navel gazers" to music industry executives -- they are looking for value in an unnatural way. I mean, against nature. Ideas are not property -- they can be shared, and then we all have them. Giving them away doesn't remove the idea from one's brain.

Including this idea -- I think it's cool that they were able to salvage the satellite, and even cooler that they told us how to do it ourselves.

Re:NASA's troubles

[colmore]

I'll reply to this and reply to every other "but the second hand benefits!" posts.

That's not why we went to the moon. Noble speaches, triumph of human achievement, materials science aside, we went to the moon to beat the damn Ruskies there.

The (very great) side benefits are a wonderful justification after the fact, but if the Russians were sending people down into the Marianas Trench in the Atlantic Ocean, we would have gone there instead.

I'm *not* arguing against the space program. I'm just saying that comparing the mundane modern NASA against the "glorious NASA of the past" is unfair. Our motivations in the past were rather jingoistic, and similar pressures aren't in place now.

I personally think continued exploration, if perhaps not manned exploration, would be a wonderful thing for science. But science is never what convinced congress to send us up there in the first place. Manned exploration is just too dangerous and expensive, and until colonization is a possibility, then

And as for lunar mining etc. that will happen the instance it can be demonstrated to be practical, but the costs of sending a pound of equipment to the moon and getting a pound of whatever material back are so great that unless they've got fist-sized diamonds up there, it isn't happening soon.

In an ideal world, Dupont, Nike, Intel, etc. etc. would invest in NASA since the public-domain research from the space program *directly* contributes to their profit, but likewise, it isn't happening, and they'd probably claim intellectual property.

For the meantime though, it is far easier to get money budgeted for worthy causes by giving a direct cause (cure cancer!) than something vague (tidbits of earthly biproducts!)

I'm not saying I like this reality, it's just the reality.

Powerful magnets

[pacc]

Some people objected to installing a potent soundsystem in a satellite, but the subwoofer saved the day.

In space, noone can hear you scream.

from the paperclips-and-chewing-gum dept?

[Bnonn]

What good are these things without duct tape?

Magnetic stabilization only good for one axis?

[XNormal]

You can couple to a planetary magnetic field, like these guys are doing. Again, only good for one axis

Not really. Full 3-axis stabilization can be implemented using the Earth's magnetic field. Unlike a passive pole the magnetotorquers are active elements and the magnetic field doesn't always point down so at different parts of an orbit it can be used to control all 3 axes.

Design and Experimental Test of Magnetic-Torquer-Based 3-Axis Satellite Attitude Controllers

Yet Another Star Trek Moment

[Ecyrd]

Quote from the press release:

To make up for the missing reaction wheels, scientists and engineers developed new sets of procedures and software that let them use equipment known as magnetic torquer bars in a new way. Controllers can generate local magnetic fields by running electric current through FUSE's three torquer bars, and can flip the polarity of these fields by changing the direction of current flow.

So, reversing the polarity really DOES work! :-)

Re:Yet Another Star Trek Moment

[Sabalon]

That would be Dr. Who and reversing the polarity of the neutron flow :)

If it was Star Trek they would have just run a level 3 diagnostic.

Safe Mode

[fruey]

This automatically put the satellite into a pre-programmed "safe mode" configuration on December 10, 2001.

Arrrgh! Bill is everywhere!

Safe mode?!?!

[pinkUZI]

This automatically put the satellite into a pre-programmed "safe mode" configuration on December 10, 2001.

Don't tell me it's running Windows!

The remaining wheels are still used

[Gino]

At first I was quite surprised at the quoted pointing accuracy achieved (1/4000th of a degree) by using only the magneto-torquers - as implied by the article. The original intended use for these torquer rods are clearly explained in other comments, so I will not repeat them here.

What the article omits is that the fine pointing accuracy is achieved using the magneto-torquers in combination with the two still operational reaction wheels. From the original NASA press release (dated 14 Dec 01) where the anomalies with the two reaction wheels were reported the strategy was laid out to rescue the science mission:

One of the new control mode concepts being investigated is to use the two operational reaction wheels in conjunction with the satellite's magnetic torquer bars to provide control in all three axes. The magnetic torquer bars are presently used to manage the momentum of the reaction wheels by applying a torque on the satellite against the Earth's magnetic field. The torques necessary to make up for the failed wheel would be in addition to that required for momentum management. This is well within the capability of the magnetic torquer bars.

What they probably managed to do is to use the two remaining wheels to do the fine pointing but the satellite will tend to slowly spin 'of course' lacking the two other wheels to compensate. By bringing the torquers into the loop they cancel the spin and attain the fine pointing.

It is nowhere mentioned but I wonder if they can maintain the pointing accuracy long enough to get maximum exposure time. Since they've said that the spacecraft has been restored to full operations I guess it is not a problem.

I'm not trying to take anything away of what they achieved, only to clarify what is omitted from the article (possibly not to make it too technical I guess). It still is an impressive feat and indeed a super hack!

Re:The remaining wheels are still used

[FUSENerd]

You're right, the two remaining wheels are still used.

What they probably managed to do is to use the two remaining wheels to do the fine pointing but the satellite will tend to slowly spin ?of course? lacking the two other wheels to compensate. By bringing the torquers into the loop they cancel the spin and attain the fine pointing.

Actually, not quite. The roll and "skew" wheels are the ones that still work fine. The new design allows the torquer bars to correct an axis that is basically perpendicular to the roll and skew directions, which is sort of diagonal across the science apertures.

It turns out that although the torquer bars are not designed for fine control (their control bandwidth is 15 times lower than the reaction wheels), the satellite is also heavy compared to the MTB's torque. So, the pointing stability is in fact quite good, and the jitter is not much worse than what we had before... as long as the satellite is not pointed in a part of the sky where gravity gradient disturbances are strong.

Re:The remaining wheels are still used

[Gino]

Thanks for the extra info!

It turns out that although the torquer bars are not designed for fine control (their control bandwidth is 15 times lower than the reaction wheels), the satellite is also heavy compared to the MTB's torque. So, the pointing stability is in fact quite good, and the jitter is not much worse than what we had before... as long as the satellite is not pointed in a part of the sky where gravity gradient disturbances are strong.

An oversight on my part ;-) I have only worked on the smaller variants of satellites (100kg to 500kg) - dwarfed by the FUSE of course! The smaller sized S/C poses interesting problems at times. E.g. on one satellite the imager had its own stepper moter used to rotate the optics to enable stereo imaging (scanning the earth's surface from different angles). The dynamics of the small stepper moter had to be considered in the control loop as it had a gyro effect on the rest of the S/C due to the satellites relative small size (about 80kgs if I recall correctly)!

Broken link

[Gino]

Sorry, the Preview screwed up the URL. Here is the link to the original NASA Press Release.

Amusing Timing...

[ebbomega]

Considering this week's poll... Possibly a better header would have just been "Geeks in Space not totally gone..."

Sorry. It's 4 in the morning and I'm all out of American Dew...

Re:This is NO BIG DEAL

[ONOIML8]

It might not be a new idea, and I'm sure it's not. But it is a VERY BIG DEAL.

The reason it is a VBD is that every space program in the world right now needs some positive press. Everyone has been so focused on the negative thing, and there have been a lot of negative things, that we've lost sight of even the small successes.

So let's make a big deal of an old trick, pat these guys on the back for being smart enough to dust off the trick and use it, and give them a bit more encouragement to do it better next time.

Otherwise I worry there wont' be a next time.

What ever happened to

[swagr]

The system uses a complex new set of procedures...

A NASA Ultraviolet Spectroscopic Satellite uses complex procedures for guidance. What ever happened to controling a satellite with smoke signals?

Re:What ever happened to

[edremy]

A NASA Ultraviolet Spectroscopic Satellite uses complex procedures for guidance

What I still don't understand is how they rotate it back out of the imaginary plane. I would think you'd try and stay away from it altogether since you might hit a stray pole.

NASA and Russian Programme

[CDWert]

Well, I must say it looks as with budget cuts and a total lack of inspiration (possibly a result of the cuts) NASA is starting to lokk more and more like its russian counterpart, aging technologies, equipment poorly designed equiptment, and having to hack everything to hell and back just to get it to work.

Maybe I should go into the space-tape buiness, or selling external aftermarket thrusters to keep this shit in space.

I am really suprised NASA is in as bad a shape as it is, The Military can use space as the ultimate high ground, cmon the AF even has space figter training in progress, where are the damm ships and when will these efforts pay off in the comercial sector ?

The moon missions were singulary one of the greatest technical feats ever accomplished, more research and commercial products were born from the Appolo missions thatn any other goverment venture sending us YEARS ahead of our competiton , only for what ? To sit on our asses and never rise above 30 year old shuttle designs ?

My favorite space hack

[Thagg]

About five years ago, Hughes launched a communication satellite. To be useful, these have to reach a geosynchronous orbit. It turns out that the most efficient way to get to from a low-earth orbit to a geosynchronous orbit is to fire a rocket twice [or so it was thought.] The first firing raises the apogee of the orbit to the geosynchronous altitude; so that the satellite is in a very elliptical orbit. Then, when the satellite is at apogee, you fire the rocket again to circularize the orbit. Usually this same motor changes the plane of the orbit as well. Most satellites are launched into orbits inclined to the equator somewhat, and geosynchronous satellites have to be over the equator. It is most efficient to make the orbital plane change at apogee, too.

There was a rash of apogee kick motor failures, and in this particular satellite the motor failed, leaving the satellite in a uselessly ellipitical orbit. There were small thrusters on the satellite which were to be used for station-keeping (small orbital adjustments) but it didn't have nearly enough propellant to raise the perigee. Hughes finally abandoned the satellite.

But one engineer refused to give up. It turns out that the transfer orbit paradigm above is the probably most efficient path in a single-planet system, but Earth has this anomolously large, close, Moon. And while there wasn't nearly enough fuel to get raise the perigee to geosynchronous altitude, there was more than enough fuel to raise the apogee out to lunar orbit. He was given permission to try to rescue the satellite.

In the end, two passes by the moon were made, each raising the perigee somewhat and lowering the inclination of the orbit. The remaining fuel in the satellite was used to lower the apogee back to the geosynchronous orbit altitude, but unfortunately the inclination couldn't be brought down quite to zero, so the satellite isn't in its desired orbit even today. Still, it's in an orbit where some use can be derived from it.

The satisfying conclusion to this story would be that all geosynchronous satellites are launched this way, now. Unfortunately, you can't mess with the status quo to that extent; and satellites are still, in the main, launched the old transfer-orbit way.

thad

Ahem.

[virg_mattes]

> Grammar nazis unite!

Should that not be "Grammar Nazis unite!" instead?

Virg

Actually

[virg_mattes]

There was some work done in an attempt to replace fuses on spacefaring vessels with breakers, the idea of course being that if a breaker popped, a servo could reclose it at a later time (we looked into this issue while I was in college, putting a not-small amount of work into materials development for low-temp breakers that would still work). The concept was scrapped, however, when NASA engineers who were getting our results discovered that (at least with late '80s tech) repairing the fault that opened the breaker was more often than not impossible by remote, so having a servobreaker was pointless. Still, with advances in robotics, I'm still hopeful that one of these gizmos will become useful, and having my name engraved on a piece of polymer that gets to leave the solar system would be a nice memorial.

Virg

Ummm...

[epepke]

Didn't the scientists actually get the satellite up and running as fast as possible? What would you have had them do, get a really long stick and push it?

The problem is not that you need to push the big button in the sky sometimes. The problem is developing a mentality that says that rebooting the server "fixes" the problem. Rebooting the server is palliative. It keeps people from taking preventative and prophylactic measures. This attitude and its destructiveness are lamentably common in business.

Frontiers, myths, and humanity

[epepke]

We need to go because the alternative is suicide. We need to go because we are human and wish to continue to be human.

The most valuable result of the moon landing was not the scientific research, the spin-offs, or the political gain. It was the photograph of Earth as seen from the moon, just after Earthrise, taken by a human being, holding the camera.

To continue to have frontiers is more important than anything else. We could cure cancer and AIDS, fix the environment, and become immortal, and we would be nothing more than healthy, immortal apes. But the way of the explorers is a way that apes do not know, and we must keep it. At this juncture, that means deep sea exploration and space exploration, in person, not by robots.

Yet Another Trekkie Moment

[virg_mattes]

Or perhaps they'd have beamed it into the cargo bay and fixed the damn wheels.

Think, people, think!

Virg

Re:Yet Another Trekkie Moment

[susano_otter]

Actually, they would've reconfigured the main deflector to emit a tachyon pulse. And the solution would've been completed in 1/4th the time NASA took.