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NASA's Compton Hits Earth On Sunday
fialar writes: "NASA's Compton Gamma-Ray laboratory is due to plunge into a remote area of the Pacific on Sunday marking an end to the mission. Read the complete story here."
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Skylab was great. I have some pictures from NASA in Ames from the party they had when it finally plunged through the atmosphere and burned up. I seem to remember reports that a 1 foot or so peice actually made it to the ground and landed in New Zealand somewhere. Remember the US/Soviet docking? I forget what it was called but remember seeing it on TV.
More race stuff in one place,
than any one place on the net.
Earth escape speed is about 25 mi/sec. This speed, however, will still leave the object in solar orbit at earth's distance. To make the object fall into the sun, you have to accelerate it to the orbital speed of the earth around the sun, about 67 mi/sec. This delta-v requires far more fuel than any spacecraft can possibly carry to low earth orbit.
You got all the facts right; the numbers are off. Earth escape speed is 7 miles per second (perhaps you were thinking Mach 25, orbital speed?), and earth orbital speed is... damn, I used to know this one. BOTE calculations give me 19 mi/sec.
Anyway, a lot of speed. We can't even send probes up to solar escape velocity without gravity assists, and solar escape velocity is actually lower deltaV than an orbit inside the sun.
No, much better to drop used-up LEO satellites into the ocean (since air resistance will bring them down eventually, best to force the matter and keep the reentry risks minimal), and to move used-up HEO satellites into parking orbits where they are less likely to be a debris source.
To answer another poster's question, yes satellites carry rocket fuel on them... although it's almost certainly not going to be the same high-thrust cryogenic fuel that got them up in orbit to begin with. For a satellite, you just need a little thrust for stationkeeping purposes. Since the Earth isn't perfectly round and isn't the only other body in the universe, you can't expect your satellite to follow a nice Kepler orbit exactly without help. And for LEO sats, your orbit will drop over time as air resistance (not much of it, but it's there) takes its toll, unless you have small thrusters to raise the orbit again.
Of course, what I'd like to see done with old satellites is refueling and refurbishing. I'd like to see a tug in orbit with ion drives to reduce its fuel requirements and a metal or water-shielded bay to carry satellites through the Van Allen belt. The primary use of such a beast would be to carry satellites from LEO to GEO (thus putting much heavier sats in geosynchronous orbit than we can with chemical rockets alone, and permitting travel to GEO from reusable launch vehicles), but perhaps even bringing back satellites for on-orbit refueling and replacement of failed parts would be economical.
The Compton Gamma-Ray Observatory outlived its mission lifetime by seven years. NASA considers it to be one of the space agency's most successful missions.
All that any satellite has to do is fulfil its mission. If it sticks around another year or two, then that's gravy. All satellites eventually die; the low earth orbiting ones all need to be deorbited so they don't collide with other satellites. Compton outlived its life by _seven_ _years_. The US taxpayer got WELL worth his or her money with this one. ;-)
Compton, satelite
Not the bad L.A. suburb
Don't confuse the two
According to the article (for those too lazy to read it), it was still working fine with 2 out of 3 gyroscopes after the first one failed. They decided to crash it to reduce the risk of debree hitting a person from 1 in 1000 (after the second gyroscope failed and it lost control) to 1 in 29 million.
That seems like kind of a waste to me. I mean, 1 in 1000 doesn't seem so bad to me, odds-wise. And that's only after the second one fails. They probably could have gotten years of service out of it without any problem.
I hope the press is kind to them, they sure were rough on NASA back in Dec,-Jan when this first was announced.
WASHINGTON, D.C., June 2, 2000. Secretary of the Interior called a press conference today to announce the implementation of a new cooperative agreement between the U.S. Fish and Wildlife Service and the National Aeronautics and Space Administration. The interior Secretary called the agreement an historic step towards successful implementation of Reinventing Government, Stage II, that has been developed by the Clinton Administration.
Under the terms of the new agreement, packs of wolves, imported from Canada, will be introduced into several NASA centers. In particular, the NASA research and spaceflight centers at Goddard (Greenbelt, MD), Marshal (Huntsville, AL), Johnson (Houston, TX), and Ames (Moffett Field, CA) have been targeted. "Wolves are an endangered species that need special protection to allow their populations to increase," said Babbit. "Private landowners have objected to releasing wolves in National Parks, fearing that they will wander onto private lands and attack livestock. This agreement represents an innovative compromise that will allow the wolves to prosper in areas where the public will have no objection to their presence."
The Administrator of NASA, Daniel Goldin was present at the Department of Interior press conference. When asked for his reaction to the plan, Goldin said, "NASA is undergoing unprecedented downsizing in response to the desire on the part of the Clinton Administration and the U.S. Congress to reduce the size and cost of the Federal Government. This agreement with the Fish and Wildlife Service will introduce ecologically sound management practices that will replace the 'business as usual' approach to personnel issues at NASA. Federal agency work forces are no different than overpopulated herds of deer or elk in our country today. We, too, need to thin the herds," said Goldin.
The Interior Secretary interrupted Mr. Goldin to reassure NASA employees that the vast majority of them would be unaffected by wolf pack predation. "Keep in mind that wolves tend to prey mostly on the weak and slow," Babbit said. "Most NASA employees can move pretty fast and stay out of harm's way. If you keep alert and show no fear, chances are the wolves will leave you alone. Our wildlife experts tell me that 95% of the NASA employees will be unaffected by wolf predation in an average year."
An information brochure, entitled "Adapt or Die," will be distributed to all NASA employees. The brochure explains the ecological basis for this new management policy. It also points out that there are severe penalties for harming endangered wolves, even in self-defense. It says, "Keep in mind that humans are not an endangered species and, therefore, lack protection under the law."
Oh well, I guess I better get back to the walker, I'm pushing 30 here.
--
The unsig!
I remember when NASA use to try to squeze every ounce of life out of it's probes, Just look at the history.
Neptune and Uranus where secondary objectives for voyager II if it survived that long.
Pioneer 10 and 11, first probes to cross the asteroid belt, visit jupiter, and visit saturn. They continued obtaining data from them long after the jupiter and saturn(pioneer 11) flybys. Pioneer 10 expired in the mid 90's (launched 1973) and they are predicting pioneer 11 (launched 1972) to kick the bucket anyday now. It is still returning usefull data, though it has no budget!
Pioneer 6, launched in 1965 is considered NASA's oldest operational space craft, I know it was still running in 1996, I think it is still running...
Pioneer Venus launched in 1978 was designed to last a year, they kept it going until 1992.
The Viking missions, launched in 1976, they kept them going till the landers died in the mid 80's.
The Skylab rescue, instead of writing it off they salvaged the derilict space station.
They salvaged and repaired Solar Max with the shuttle, to bad they where to cheap to launch a reboost mission to keep it going later (under the NEW NASA)
And finally the (Orbiting Astronomy Observatory) OAO-3 copernicus. Launched in 1972, it was kept going until the early 1990's. As the Gyro's failed (one by one) the control software was modified to handle first only 2 working gyro's, then only 1 working gyro.
Which btw. is what happened to GRO, it now has only 2 working gyro's. GRO was designed to be serviced by the space shuttle (just like solar max, and hubble). NASA acknowledges that they can modify the software to safely control/re-enter with 1 or 0 operating gyro's.
This is a waste of tax payer money, and a direct effort by the NEW NASA to distance itself from the successful programs of the OLD NASA.
Did you hear since the VP is in charge of the space program that Al Gore invented outer space ?
TastesLikeHerringFlavoredChicken
While I vent some deep links to nasawatch
comments on the crash
likely excuses by NASA
FAQ on why to crash
SpaceflightNow crash status
TastesLikeHerringFlavoredChicken