16 March 2004
This is the one area in which our expectations about space travel turned out to be too negative. Natural micrometeorites turned out to be so rare that heroic methods like the giant Pegasus spacecraft had to be employed just to get some meaningful statistics. The danger of meteorite damage is so small that it can mostly be ignored.
But because of our carelessness in the first 40 years of space flight, we have recreated that danger. The thousands of dead satellites, rocket stages, and associated junk pieces that have accumulated in Earth orbit since 1957 form a system of colliding bodies very much like the asteroid belt. And like the asteroid belt, mutual collisions are inexorably smashing this material down into smaller pieces.
The Earth is now encircled by its own artificial meteor storm, which is getting thicker by about 4% per year. All spacecraft in Low Earth Orbit are orbiting in the middle of this celestial shooting range. Some unmanned spacecraft may already have been destroyed.
This problem is so scary and so intractable that nobody wants to hear the unpleasant facts about it. So it isn't any surprise that the "space journalism" community has mostly missed the most important news story since the Columbia crash: the near-destruction of the International Space Station by an orbital debris strike at 2:59 AM Eastern Time on 26 November 2003, and the narrow escape of the two crewmen from unpleasant deaths.
On the surface, the Nov. 26 event seems harmless enough. The caretaker crew of the ISS heard a loud noise described by Michael Foale as "like a metal can being crushed and then unfolded." A careful examination of the Station showed no defects (except of course the dozens of failures in major systems that have already accumulated over the scant five years since construction began). So NASA in its traditional way has declared this event a non-problem since no one was killed.
Of course we learned from both Shuttle accidents that any unexplained anomaly in a complex system like ISS should not be ignored. It is a sign that we don't understand how the system works. And if we don't understand it, we can't make a reliable estimate of how often it will fail. The Shuttle managers chose to ignore the danger of small foam fragments falling off the ET, even though there was no good understanding of the mechanism involved. They just declared it a non-problem and pressed on to destruction.
By ignoring the Nov. 26 event and its frightening implications, NASA is setting itself up for another disaster that will kill yet more astronauts and probably the entire US manned space program as well.
So what really happened at 2:59 EST on Nov. 26? Just look at this diagram of the mutilayered "space armor" on the ISS modules:
The "Stuffed Whipple Shield" on ISS is supposed to work as follows: A space junk fragment hits the outer aluminum "bumper layer" and explodes due to the kinetic energy of its ~10km/sec velocity. A cone-shaped blast of metal fragments, melt droplets, and plasma strikes the intermediate layers of Kevlar "stuffing" and this material is bent inward. Due to the dispersal of the original junk particle's energy and momentum over a large area, the ~3mm aluminum pressure hull of the Station is untouched.
But what happens if the particle is just slightly larger than the ~1cm Al sphere that the armor is designed to resist? The Kevlar "stuffing" is thrown violently against the pressure hull, which is dented inward like a car fender hit with a wooden mallet at your local body shop. Unlike a car body, the internal pressure of the Station's atmosphere will then flatten out the dent and return the pressure hull to its original shape.
This near-penetrating impact scenario explains the odd two-phase sound heard by the astronauts inside the Station: "like a metal can being crushed AND then unfolded." This by far the most likely explanation. It isn't just my theory -- engineers involved with the design of the shield have independently proposed it. Anyone with any knowledge of basic physics must suspect that this is what happened.
So what did NASA do to test this theory?
The first response was to inspect the area of the noise with the external cameras on the Station. It happens that these cameras have only a distant and oblique view of that area, so they were conveniently unable to see the hole in the outer bumper, which would only be about 1cm across at the largest.
The station crew also checked out every item of internal equipment that might possibly have made such a noise. No evidence of any malfunction was found.
Some have claimed that the US space recon community was asked by NASA to look at the ISS with their super-secret spy satellites and ground-based telescopes. This would be a pointless exercise, because none of these systems can possibly resolve a half-inch feature on the ISS. But since the failure to use these military assets to image the shuttle Columbia caused such an intense controversy, possibly the request was made anyway, to insure against a future investigation.
It is also possible that this story was deliberate misinformation. Since the public has a wildly exaggerated notion of spy satellite capability, the mere rumor that the spooks have not detected anything would tend to damp down public curiosity about the Mystery Noise.
The Russian space surveillance organization added to its growing reputation for incompetence by releasing two contradictory stories, one claiming that its radars had detected a fragment knocked off the station, and another saying that no such detection had been made. As always in the wacky world of Tsar Vlad, it is impossible to determine the truth.
The only definite way to determine if the 26 November event was a debris impact would be for one of the caretaker astronauts to go outside and visually examine the suspect area. Indeed, such an inspection was scheduled for the recent controversial two-man spacewalk. But the EVA was cut short by a spacesuit malfunction and the inspection never took place. NASA declared the EVA a "success" like they always do with obvious failures.
So we don't really know for sure what happened to the ISS on 26 November 2003. But the evidence suggests that we very nearly added two more astronauts to the 14 already killed by NASA's refusal to face plain facts, whenever those plain facts call for the manned program to be stopped or even slowed down.
So how soon can we expect an actual hull breach on the ISS? The National Academy of Sciences addressed this in a 1997 report. They calculated that over the ten years that the fully assembled ISS would operate there was a 19% chance of a penetrating hit on one of the pressurized modules!
It's worth thinking about that number for a minute. Anyone who bothered to read that NAS report knew that the Space Station program basically had a revolver with one loaded chamber pressed to its head. Dan Goldin and the Clinton Administration went ahead with a program that was essentially a game of "Russian Roulette" in space.
A penetration would probably kill or seriously injure any astronauts in the punctured module, due to the shock wave and shower of high-speed fragments. Even if the surviving crewmen managed to seal off the punctured section, it would be depressurized and useless. If the damaged module were in the middle of the ISS, some crewmen might find themselves in an isolated section with no access to the ISS "lifeboat", condemned to a lingering death from CO2 poisoning like many submarine crewmen who have been in similar situations. It is hard to imagine how the US Congress and the public would continue to support the manned space program after this kind of disaster, on top of Challenger and Columbia.
NASA made a token attempt to give the ISS crewmen complete protection in response to that 1997 study. They sent a request to the US Space Command to track and monitor all space debris in the ISS altitude band down to below 1cm in size (the theoretical capacity of the armor). Space Command responded with a request for $7B from NASA to upgrade its radars. And then the whole idea was quietly dropped. Even if the $7B upgrade had been funded, the result probably would have been so many false alarms (due to the inevitable error margin in projecting orbits) that the warning system would have been useless.
The military spacewatchers continue to provide NASA with warnings of possible collisions with objects larger than about 10cm in diameter. And the ISS periodically maneuvers to avoid such objects. But there at least 100,000 objects in the 1-10cm size range that are not detectable by existing US or Russian radars, but which could cause a fatal penetration of the ISS or severe damage to the many vital systems outside the pressure hull.
Since the 1997 NAS report, the orbital debris population has continued to grow at the predicted rate -- unlike the Station, which is only about one-half finished after five years of work. The NAS panel didn't consider the chances of a penetration during the assembly period. And their ten years of "routine operations" was basically 2001-2011. Now the ISS not scheduled to be finished until 2010. International agreements call for it to remain manned until at least 2020 (although the new Space Initiative calls for the USA to withdraw from the project in 2016). So the lifetime danger of a catastrophe will clearly be much higher than the NAS panel predicted. We are playing Russian Roulette with two or three chambers loaded!
This problem can't be fixed with any reasonable amount of money. The ISS is not only useless and absurdly expensive, it is a death trap for its crews. It is time to abandon this project before it claims any more lives.
The orbital debris menace also seems to be the reason for proposed changes to the mission plan for the JIMO Jupiter spacecraft. This mission was supposed to be launched into a low parking orbit on a Delta 4H or Atlas 5H booster, and then use the new Prometheus nuclear-ion spacedrive to slowly spiral up out of the Earth's gravity well over a period of two years.
But the new plan is different. According to Space.com: "However, those two years of exposure to the space environment - rife with human-made orbital debris, meteoroids, and intense radiation belt hazards - are among issues that have moved NASA to consider putting JIMO on an escape velocity shortly after launch."
Of course, the hazard from meteoroids is trivial and no larger near the Earth than in deep space. And a spacecraft designed to orbit Europa will have to be so rad-hard that it won't even notice the Earth's Van Allen Belts. The only danger cited that could possibly have caused this huge change in the JIMO flight plan is "human-made orbital debris".
A look at the preliminary design concepts for the Prometheus drive module reveals that it is particularly vulnerable to space debris -- far more so than anything launched before. Prometheus requires huge radiators to dump the waste heat from its nuclear reactor. A tiny puncture in any of many small pipes in these radiators would cause loss of coolant and reactor shutdown -- or meltdown. Coolant is already leaking from several Soviet reactors that were abandoned in high orbits in the 1970s and 1980s, probably due to debris impacts.
Even worse, the feeble thrust of the Prometheus ion engines will only gradually lift JIMO through the debris band around the Earth. It will climb up through the clutter zone on a long spiral orbit that will cross paths with almost ever screw and paint chip ever lost by a LEO satellite. It takes decades for an average 1-cm fragment to be pulled down to Space Station altitude by atmospheric drag, but JIMO will climb up and pass them all within a few months. It is easy to see why NASA wants to put JIMO directly onto an escape trajectory with a chemical rocket before starting the reactor.
And this change is not a trivial one. Adding a chemical escape stage pushes up the weight of JIMO from 26 tonnes to 50 tonnes -- far beyond the capacity of any existing booster. The planners are now hoping that NASA will develop Shuttle-C or some other heavy-lift booster and give them one for JIMO.
And the super-Prometheus that some people hope will be the core of the new manned space initiative? Forget about it. Nuclear-ion drive is just another technology that looked good when Ernst Stuhlinger proposed it in the 1950s , but just isn't usable in the real Solar System. Any nuclear rocketships in Plan Bush will be based on NERVA, not Prometheus.
So the lesson here is that we can no longer hide our heads in the sand and pretend that the space debris issue is not a very serious threat to future manned operations in LEO. Already, it has nearly killed two astronauts and crippled the only new space propulsion system that is actually in the NASA budget.
In order to make any intelligent plans for implementing the new Space Initiative, we need to know how bad the space debris problem will be 20 to 50 years in the future. If it will not be possible to use LEO for prolonged assembly or parking of interplanetary vehicles, we will have to shift such operations at another site such as the Earth-Moon L-1 point. The Congress or the Aldridge Commission needs to force NASA to conduct a serious study of the future evolution of the orbital debris population and make specific predictions about what limitations this hazard will present to the manned missions proposed in the new Space Initiative.
The ideal group to do such a study would be the space debris research group at Johnson Space Center. Oddly enough, NASA tried unsuccessfully last year to de-fund this group and strip itself of any in-house experts on the debris threat! (Experienced NASA-watchers have learned to recognize this kind of behavior as a red flag. Like Saddam Hussein, NASA instinctively responds to bad news by quietly shooting the messenger who brought it. Has this organization already discovered disquieting information that offended the Space Lords?)
If this study is not done, we might find ourselves some years down the road with a lot of expensive nuclear space hardware that cannot be flown due to safety constraints. In the worst case, we might have some more dead astronauts who could have been saved with a little foresight and honesty.
Jeffrey F. Bell is Adjunct Professor of Planetology at the University of Hawai'i at Manoa. All opinions expressed in this article are his own and not those of the University.