The need for real “rocket science” to solve Russian spaceflight setbacksby James Oberg
|
| How could top Russian space officials be so badly advised by their experts? And why did they feel so eager to display their confusion and ignorance in front of the entire planet? |
The failure of the probe, say top Moscow investigators, remains baffling because no useful telemetry was radioed back to Earth. The head of the Russian Space Agency, Vladimir Perminov, is puzzled about why so many “accidents” seem to be happening to Russian space vehicles just when they are out of radio contact with Russian tracking sites. Both Perminov and the emeritus space official Yuriy Koptev have publicly speculated that a powerful radar on Kwajalein Island, being used for tracking a passing asteroid, may have inadvertently “zapped” the Russian probe.
Ironically, the only aspect of the mission that Moscow officials claim to be certain of, is exactly where the probe’s debris landed: safely in the Pacific Ocean, off the west coast of Chile. And this is the one Moscow-sourced “factoid”—using the ending -oid in its traditional meaning of something that looks like, but really isn’t, the denoted word—that Western experts are themselves most dubious of.
But well-established principles of rocket science, learned through amazing experience over the past half century, can establish that the things the Russians say they are baffled by should not be puzzling at all, and the thing they claim to be absolutely certain of should be doubted the most.
And that’s the greatest puzzle of all from this affair. How could top Russian space officials be so badly advised by their experts? And why did they feel so eager to display their confusion and ignorance in front of the entire planet?
Lack of telemetry
According to an Interfax report from Moscow on January 23, even if the probe’s radio had been functioning properly it would have been nearly impossible to communicate with it while it remained stuck in its low “parking orbit”. That orbit meant that the probe quickly fly past any ground sites trying to get in touch with it.
“Practically all of the radio stations involved in the project were expected to operate in the distances of hundreds of thousands of kilometers when the probe’s stay within their zone would last for hours,” a source close to the Phobos-Grunt accident investigation commission told Interfax.
| For the first ten days of the mission, the orbit’s perigee—its low point—gradually increased, even as natural air drag should have been lowering the orbit. |
“The designers hoped that Phobos-Grunt would not stay in the low Earth orbit for long,” the source continued. “They thought it would head for Mars after having circled the Earth a couple of times, so it did not carry a short-wave transmitter and receiver for stable communication with ground stations.”
But if the probe could not communicate by radio, it still was trying to signal its builders. Its autopilot was sending clues that might yet be interpreted to imply a particular failure mode.
This signaling occurred through a bizarre pattern of its orbital motion. For the first ten days of the mission, the orbit’s perigee—its low point—gradually increased, even as natural air drag should have been lowering the orbit. The effect was real, not a computational modeling bias or some other artificial deviation.
This subtle but steady alteration of the flight path, as noticed and reported in tracking data released by the US Department of Defense, then stopped abruptly, and natural orbital decay commenced. This continued all the way down until the probe hit the atmosphere on January 15.
Where was the thrusting—for such it must have been—coming from, and why did it stop? Western observers still don’t have enough technical specifications of the probe to know for sure, but speculation centers on an accidental byproduct of autopilot-controlled thruster firings to keep the probe pointed in a certain direction.
Such thruster firings are known to nudge spacecraft off planned flight paths. Improperly modeled predictions of this disturbance, caused by erroneous units of measurement, led to the navigation error that allowed the Mars Climate Orbiter to accidentally hit the upper atmosphere and burn up when it arrived at Mars in 1999. That’s well-known rocket science.
Reading the autopilot’s thoughts
Why was the Phobos-Grunt autopilot commanding so many orientation maneuvers? A clue was given in a remarkable article in Moskovskiy Kosmolets on December 8, which included numerous detailed interviews with specialists involved in the project. One of them, identified only as a senior worker at the Institute for Space Science, told the reporter that during the first (and only) successful communications session with the probe, ground controllers were surprised to see that it had failed to hold its sun-pointing orientation as it passed through Earth’s shadow. This meant it had to instigate a large reorientation maneuver at sunrise when a special sensor locked onto the sun. If this error continued to recur at every orbital sunrise over the next few days, it could explain why only one portion of the orbit was showing effects of the thrusting.
An even more plausible hypothesis has been developed by Ted Molczan. He suggests, in a long study to be released shortly, that the net posigrade burns were the autopilot endlessly repeating the pre-ignition sequence which includes a small propellant settling burn (also called an ullage burn). But something prevents ignition, so the autopilot, trapped in a tantalizing loop, restarts the sequence.
| Molczan suggests the autopilot was endlessly repeating the pre-ignition sequence which includes a small propellant settling burn (also called an ullage burn). |
In an email to me, Molczan mustered another argument for his suggestion. It is not generally recognized “that there were two components to the perigee creep,” he announced, and he was right: it was news to me. “The perigee distance crept higher, but the argument of perigee also crept forward, and it was the latter that accounted for about 80 percent of the delta-V of these maneuvers.”
In his draft paper, Molczan insightfully pointed out: “Given the lack of telemetry, I would expect the Russians to have performed a similar, but more sophisticated version of my analysis, in order to determine the likely state of the hardware and software that would account for such behavior.” Any rocket scientist would have expected this.
And why did the “perigee creep” effect suddenly stop after ten days? At some point the propellant tanks allocated to the thrusters would have become exhausted.
The Russian investigators alone have the probe’s design data to assess this hypothesis. So thanks to these orbital changes, even without any radio signals they are not totally “in the blind” about what was happening aboard Phobos-Grunt, thanks to rocket science.
“Blind spots” of orbits
In a long and candid interview with Izvestiya, Roscosmos head Vladimir Popovkin remarked on another idea that bothered him: “Also incomprehensible are the partial failures in our vehicles in this period when they fly over the side of Earth blocked from Russia—where we do not see them and receive telemetry from them.”
This seemed a mite suspicious to him, perhaps suggesting deliberate malicious intent on somebody’s part. “These days there are very powerful means for affecting space vehicles, the possibility of the use of which cannot be excluded,” he continued, quickly adding, “I do not want to accuse anyone.”
| By asking the wrong question, Popovkin was accidentally “forcing” the wrong answer. A rocket scientist would have looked for commonality of spacecraft activity, not of cartographic coincidence. |
Popovkin, who took over the space agency after his predecessor was retired due to a series of space failures a year ago, came from a long career in military space operations. This was followed by a stint as Deputy Defense Minister for Procurement, where he concentrated on the low quality of aerospace products from contractors. For decades it was his job to be alert for enemies and saboteurs.
But by asking the wrong question, he was accidentally “forcing” the wrong answer. He should not have connected the string of recent failures with the condition of being out-of-touch with Russia. Instead, a rocket scientist would have looked for commonality of spacecraft activity, not of cartographic coincidence.
The question should have been, “Why do these failures all seem to occur when the vehicles are performing propulsive maneuvers?” And when it’s worded that way, the proper line of inquiry reveals itself.
Now, Popovkin might also have asked a fair question, “Why do we schedule major propulsive maneuvers outside the range of our space tracking?” That question, too, leads to deeper understanding of the real problem along with some obvious constructive remedies.
Many spacecraft headed into orbit rely on a second “kick” burn halfway through the first revolution, to circularize at a planned altitude or even (in the case of the 12-hour Molniya-class orbiters) raise the orbit over the northern hemisphere even higher. For those headed for 24-hour orbits, this kick burn needs to occur over the Equator since the high point also needs to be over the Equator. For lunar and interplanetary missions, solar system geometry dictates an even wider range of locations for the escape burns.
In practical terms, many Russian kick maneuvers occur at what space navigators call “conjugate points”: the region 180 degrees away from a launch site, where orbits of any launch azimuth from that site crisscross, or “conjugate”.
For Molniya-class orbits from Plesetsk, this point is off the coast of Chile, and indeed for decades residents of southern South America have been treated to twilight sky spectacles as the Russian upper stages perform their burn and then dump surplus propellant as an anti-explosion safety measure. The resulting clouds, backlit by the setting sun, create mass amazement and contribute markedly to UFO lore on that continent.
| “As the manager of NASA projects that detect and track asteroids coming near the Earth, I can tell you we have never used anything at Kwaj to do that,” Johnson said. |
For interplanetary missions, the kick stage firing tends also to be over South America, so that the ascending spacecraft appears in the sky over Russia and dwells for several hours as it climbs. In the old Soviet days, Russia sent tracking ships into the South Atlantic to provide live data links with these maneuvers, but one ship became a museum and the rest were sold for scrap in the 1990s. For Phobos-Grunt, a Russian scientist sent out emails to recruit South American amateur astronomers to eyeball the skies and report on the results of the planned rocket firings.
It was during such dynamic, inherently dangerous operations that most recent Russian spacecraft troubles have occurred. Rocket science explains clearly that the regions where the troubles occur are determined by geography and orbital mechanics. That the Russians chose to give up previous capabilities to track in these regions, and now wonder why they can’t figure out what is happening there without the help of Brazilians with binoculars, is a puzzle beyond the scope of rocket science.
The threat from Kwajalein
In seeking any possible external influences that could have damaged the probe, somebody in Moscow noticed a remarkable coincidence. The same day as its launch, NASA was making radar observations of a passing asteroid called “2005 YU55”. And since an American military base on Kwajalein Island, aka “Kwaj”, in the eastern Pacific (9.399°N; 167.482°E) has been bristling with Russia-watching radars for more than half a century, it was possible to add 2 plus 2 plus 2 to get 999. NASA officials denied it all. But that wasn’t enough for a lot of people.
Now, it doesn’t help to just take conflicting official declarations and select which to believe out of esthetics or favoritism. Instead, you follow a principle of rocket science and track back the pedigree of every item—hardware, software, verbal—that you’re building your final product with, and verify it’s authentic. Check, double-check, triple-check.
Now it’s true that Dr. Lindley Johnson, Program Executive for NEO (Near-Earth Objects) Observations in the Planetary Science Division at NASA HQ, said that NASA didn’t use Kwajalein. “As the manager of NASA projects that detect and track asteroids coming near the Earth, I can tell you we have never used anything at Kwaj to do that. To my knowledge, only NASA’s own Goldstone Solar System Radar or the radar capability on the National Science Foundation's Arecibo Radio-Telescope Observatory in Puerto Rico have the power and pointing capabilities to track asteroids at the distance of the Moon or farther.”
A rocket scientist would do an Internet search for reports of earlier asteroid radar observations, in which the actual facilities that were used were specified. They would then find out that none of these reports mentioned using Kwajalein. So Johnson’s assertion stands confirmed, and there was no motive for any Kwaj radar to transmit a super-high-powered pulse to anywhere in space.
Secondly, even if such a pulse had been sent out, there was no means of hitting Phobos-Grunt with it. High-power radar beams for deep-space probing are very concentrated and hence very narrow: slimmer than the angular size of the Moon in the sky. The odds of anything flying through such a beam, even if one existed at the time of the probe’s two fly-overs, are very slight.
The European Space Agency found that even when they actually tried to get their narrow-focus beams on the Phobos-Grunt to aid in Russia's recovery effort, it was devilishly difficult and took multiple missed attempts before they managed it—and then it still didn’t work. So there was no practical means for the postulated mechanism to actually be effective.
| The public performance of Russian space officials in recent months, related to the mysteries of the Phobos-Grunt debacle, show a fundamental lack of this “rocket science” approach. |
The last argument is the most “rocket science” related. Simple Internet-available astronomy software, such as JPL’s Horizons online ephemeris computation service, can be used to show that the asteroid in question was below the horizon during both passes of the probe over Kwaj that day. It was impossible to send a beam to it at those times, so why should anyone have been trying?
The world’s top amateur satellite watcher, Ted Molczan, ran those results and presents a detailed chronology on the SeeSat site. Former NASA Mission Control flight dynamics officer (FiDO) Daniel Adamo independently confirmed the calculations, and he was a professional rocket scientist. That demonstrates no opportunity for Kwajalein to have seen the asteroid during the intervals that the probe was passing overhead.
No motive, no means, and no opportunity: the perfect formula for proving innocence in a court of law. But apparently there were no rocket scientists, or lawyers, involved in the Roscosmos decisions to go public with such a silly suggestion.
What rocket science teaches
A rational approach to the challenge of spaceflight involves significant mental discipline and a specific habit of mind to ask the right questions and not be satisfied with superficial answers or deflectional excuses. Without this approach, disaster and disappointment is inevitable. And even with our full attention, as Mike Griffin once said, “Spaceflight is so hard that even at our best we are barely able to accomplish it.”
The public performance of Russian space officials in recent months, related to the mysteries of the Phobos-Grunt debacle, show a fundamental lack of this “rocket science” approach. If they carry out their spaceflight duties with the same level of mental flabbiness as they make their public statements, the root cultural cause of this recent chain of woe becomes clear.
And it goes beyond merely bad rocket science: this lamentable mindset touches on the kindergarten behavioral criterion of “Works Well With Others”, especially the part about blaming your classmates for your own failings. Aside from just flinging suspicions against Americans (a long, deeply-rooted habit throughout the last decade of space partnership), it involves vile accusations such as the January 26 claim from Roscosmos Deputy Chief Anatoly Shilov that “Roscomos made an official proposal to the United States to take part in the investigation [of the claim against NASA activity on Kwajalein], but the U.S. side refused.” But NASA spokesman Robert Jacobs emailed me the next day that his office had checked with all NASA groups in contact with Russians and drew a complete blank. “NASA is not aware of any such request,” he explicitly declared. If Shilov is a real rocket scientist he will be able to document his accusation. If not, people who think and talk like he did need to leave the Russian Space Agency as one step in its cultural rebirth.
Any remediation must start in the minds of program leadership, and will be quickly evident if it is there. Since the US is now bound hip and thigh and space helmet to the Russian space program, all measures in our power to encourage this cultural revolution must be taken.