Bent Out of Shape
There's a ghost in the machine, says engineer Ali AbuTaha, a fatal flaw in the design and the launch procedure of the space shuttle. The National Aeronautics and Space Administration (NASA) thinks it has exorcised the demon, putting ten successful shuttle missions under its belt since the Challenger disaster of January 28, 1986. But the poltergeist is still on the loose, threatening to sabotage the shuttle's flight manifest for the Nineties by knocking off tiles, warping booster segments, cracking main engine pumps, puncturing holes in fuel lines, and crippling multimillion-dollar payloads.
The trouble with telling people you've seen a ghost is that no one will believe you. Ali AbuTaha learned that the hard way. An engineering consultant from Reston, Virginia, AbuTaha was alarmed by errors and inconsistencies he detected in the Rogers Commission report, the official postmortem of the Challenger disaster, released in 1986. So he pursued his own investigation - not merely with pen and paper, but by visiting the launch site, conducting extensive interviews with NASA officials and engineers, and by painstakingly analyzing footage of the Challenger's 73-second flight. Filtered to eliminate glare, AbuTaha says, those films reveal a radically different sequence of events than that delineated by the Rogers Commission, a panel of scientists, astronauts, and politicians appointed by President Ronald Reagan to investigate the tragedy.
The conventional wisdom promulgated by the Rogers Commission - and accepted by the media - is that Challenger was done in by a defective gasket, an O-ring in the shuttle's solid-fuel boosters. According to Rogers Commission investigators, the explosion that shattered the shuttle and sent it cascading into the Atlantic Ocean was touched off by hot gases leaking through the failed O-ring.
But AbuTaha believes that the ghost that crept into the shuttle has little to do with failed O-rings. He doesn't dispute that the O-ring eventually gave way, but insists it wasn't the primary cause of the disaster (see sidebar: "What About Those O-Rings?"). He traces the Challenger disaster - and future disasters if his warnings aren't heeded - to a radical change in launch procedures that was mandated by NASA officials just prior to the shuttle's maiden voyage in 1981. The change in launch procedures, says AbuTaha, has subjected every mission to liftoff forces far exceeding the hardware's safety margins. It was physical forces unleashed by this change that cracked the Challenger's right solid-fuel booster and ultimately destroyed the craft.
To some aeronautics experts, AbuTaha is an engineer with an honorable cause. To NASA he's an annoying gadfly who is taking advantage of the space agency's recent problems with the Hubble Space Telescope and leaky fuel lines. (Although AbuTaha doesn't claim that his theory explains away every shuttle glitch, he says it can account for the shuttle's recurring fuel-line problems and some of the space telescope's navigational
"Every couple of months he does a press conference," says NASA spokesman Mark Hess. "Basically, he attributes every problem that comes up in NASA to his theories. It just keeps going on and on and on." Hess says the agency is zeroing in on the exact location and cause of the leaks and intends to launch its next shuttle mission in early September.
The Challenger flaws have been corrected, says Hess, adding that the space agency is satisfied with the Rogers Commission O-ring explanation. "The shuttle has flown ten flights since then. It's gotten to the point where everybody has moved on and people don't want to rehash it."
AbuTaha has been pestering NASA since the fall of 1986, repeatedly applying for agency contracts to pursue his research and being turned down every time. To date, AbuTaha claims, he has spent $152,000 from his own pocket on the one-man shuttle investigation, forcing him to mortgage his home four times, spend his life savings, and borrow from friends to support his family. Worse still, AbuTaha contends, the space agency has blackballed him, making it almost impossible for him to obtain contract work in the aerospace industry.
One proof of the campaign against AbuTaha is a sharply worded letter to the president of George Washington University in Washington, D.C., from NASA's manager of the solid rocket motor project office, Royce E. Mitchell. Mitchell expressed "surprise" that the university was offering a continuing education class taught by AbuTaha about the Challenger accident. "I have been exposed to a number of Mr. AbuTaha's qualitative analyses regarding the Challenger accident, and I find them to be flawed and his conclusions unsupportable," Mitchell writes in his February 1989 letter. Mitchell's protest failed to block the class, which attracted staff from an array of federal agencies and space contractors - the Johnson Space Center, the Naval Ordnance Station, the Environmental Protection Agency, Boeing, IBM, Martin Marietta, and McDonnell Douglas.
Every tragedy spawns its brood of conspiracy theories, and the Challenger disaster is no exception. Second-guessers have pinned the blame on a plethora of factors, from wind shear to Soviet sabotage. Washington Times columnist Warren Brookes several months ago fingered the EPA for its crackdown on asbestos-based products. The EPA's "witch hunt," Brookes wrote, forced NASA to switch from a perfectly satisfactory asbestos-based putty used to line rocket joints to an inferior - and fatal - substitute.
But AbuTaha can't be dismissed as a crank. The 47-year-old naturalized Jordanian-American is a twenty-year veteran of the aerospace industry. An engineering graduate of George Washington University, he worked on satellite and antenna projects at the international communications satellite firm COMSAT, in Washington, D.C., for ten years. He put in stints at Aegis Inc., also in Washington, D.C., and at Comtech Labs in Smithtown, New York. Since 1983 he's worked as a free-lance consultant. Despite NASA's scoffing, AbuTaha's shuttle theories have been hailed by others: he was cited by the Giraffe Society, an organization based north of Seattle, in Langley, Washington, formed to laud and publicize the work of whistle blowers. And in 1988, the Challenger Society, which was organized to commemorate the fallen astronauts, named him its man of the year.
"Ali AbuTaha is an engineer with an obsession. He's sort of an idealist who likes to tilt at windmills," says Dr. Yale Jay Lubkin, a retired army colonel who earned his doctorate in applied mathematics and now serves as an assistant editor for Defense Science magazine. An acerbic critic of U.S. military and space policy, Lubkin has defended AbuTaha's theories in several articles, the most recent published by his magazine in April. In Lubkin's eyes, AbuTaha's major fault is that he was naive to believe NASA would admit to wasting two and a half years and spending millions to fix a part that wasn't broken.
"NASA is an organization of true believers and consummate bureaucrats," Lubkin insists. "Their philosophy is pure C.Y.A.," he once wrote of the agency. C.Y.A. stands for "cover your ass."
John Pike of the Federation of American Scientists space policy project describes himself as an "agnostic" with regard to AbuTaha. "I haven't taken the several weeks I need to form an opinion," says Pike. "It's sort of like the Kennedy assassination - very big and very complicated. There is one official version of events and many unofficial versions of reality. It's a little difficult to sift through all the information on your own. AbuTaha is clearly a person of some standing in the scientific community. He's sufficiently reasonable that you have to listen to his theories, if not necessarily believe them."
That NASA might have overlooked a design error in the building of the shuttle is not impossible. And AbuTaha doesn't pretend to have mastered every one of the shuttle's systems, its myriad pumps, computers, and engines or the libraries of computations that go into constructing and flying it. He is the first to concede that the shuttle is the most complicated machine ever devised by man, composed of more than 60,000 parts built by thousands of contractors. Of those, 4686 parts are deemed of "Criticality 1," meaning if they fail, the mission could also fail.
The vastness of the shuttle prevents any single mind from understanding it completely; a seemingly innocuous change in one section can precipitate mammoth - even deadly - changes elsewhere in the craft. This is how the ghost may have invaded the machine.
The space shuttle was conceived back in 1969, the same year Ali AbuTaha joined the satellite firm COMSAT. With the moon landing imminent, it was a halcyon era for space exploration.
In February of that year, newly inaugurated President Richard Nixon formed a space task force to set goals for NASA for the Seventies and beyond. The committee, chaired by Vice President Spiro Agnew, endorsed an aggressive program of exploration that would have culminated with the landing of an American astronaut on Mars as early as the mid-Eighties.
Logistically, such a Mars mission would make Project Apollo look like a drive to the 7-Eleven: because of the distance and the physics of interplanetary travel, the crew would spend two to three years away from Earth. In order to hold the necessary fuel, oxygen, water, and supplies, the ship would dwarf the Apollo spacecraft. Agnew's task force envisioned that the Mars ship would be assembled by an orbiting space station crew, with a fleet of reusable craft ferrying men and supplies between Earth and the construction site.
Nixon abandoned the idea of a manned Mars mission as soon as he found out the cost - $100 billion for one round trip. (President Bush has recently revived the idea, but has allotted a 30-year timetable for the task.) But NASA salvaged the reusable space shuttle idea by selling it to Congress as a space delivery van/tow truck/mobile laboratory that would "take the astronomical costs out of astronautics." The original plan called for the shuttle to fly more than 400 missions during the Eighties. To date it has flown fewer than 40.
The shuttle design that NASA devised is a strange hybrid: part airplane and part rocket, part reusable and part throwaway. The orbiter carries astronauts and satellite payloads into orbit, gliding back to Earth after its mission. The solid-fuel boosters supply 80 percent of the thrust at liftoff. After consuming their fuel two minutes into the launch, the boosters separate from the assembly and parachute into the ocean, where they are recovered and eventually reused.
The only disposable part of the shuttle is the fuel tank, which supplies liquid hydrogen and liquid oxygen to the orbiter's main engines. The shuttle can't reach orbit velocity unless these engines perform properly, so NASA tests them by revving them to full throttle during the final 6.5 seconds before liftoff. (It takes about one second for the engines to reach 100-percent thrust.) The shuttle stays put on the launch pad because it's fastened to the pad by restraining bolts attached to the skirts of the solid-fuel boosters. If NASA's diagnostic computers detect anything amiss in this 6.5-second interval, the orbiter's main engines are shut down and the liftoff aborted. Once launch control is satisfied that the liquid fuel engines are A-OK - and only then - the solid-fuel boosters (which can't be turned off once ignited) are fired, the restraining bolts exploded, and the vehicle soars heavenward.
All previous spacecraft were designed with perfect symmetry in mind. The Saturn V, which carried the Apollo astronauts to the moon, and its smaller cousins were basically enormous, hollow, fuel-filled cylinders with the payload perched on the top.
The shuttle broke decades of design precedent by mounting the airplanelike orbiter on the side of the solid-fuel boosters and fuel tank - a highly asymmetrical arrangement that puts enormous stress on the whole assembly at liftoff. When the orbiter's main engines fire, they do so about 30 feet from the vehicle's geometric center of the attachment of booster to pad. This off-center thrust produces torque - a tendency to bend or rotate - so powerful that it would wrestle the shuttle to the ground if the vehicle were not securely fastened to the pad.
The 185-foot-tall shuttle is designed to bend forward several feet under the brunt of the launch force before snapping back. It vibrates for several seconds after liftoff to dissipate the energies, a motion called "twang," because it's essentially what happens to a guitar string when plucked.
Shuttle hardware was designed to match the stress and strain of precise launch procedures. The procedures laid out in the late Seventies as the first shuttle was being designed and constructed called for the restraining bolts to be blown at 3.8 seconds after ignition of the orbital thrusters. Just prior to this moment, the load on the base of the shuttle (also called the "bending moment") is 350 million inch-pounds, well within the hardware's capacity to absorb. (An inch-pound is the torque you would exert on a bolt if you were to apply one pound of force with a one-inch wrench. A torque of twenty inch-pounds is enough to unscrew the top from any jar.)
But before the maiden voyage of the shuttle, NASA engineers grew worried. Their engineering studies showed that if it were released 3.8 seconds after ignition, the vehicle would snap back far enough to scrape the launch-pad rigging. This could damage the orbiter, and the force of snap-back alone could harm delicate payloads.
NASA considered several launch options to evade this difficulty. One option was to ignite only two of the orbiter's three engines at liftoff; the other was to offset the bending by tilting the vehicle in the opposite direction on the launch pad. NASA found these cures worse than the disease. Instead, the agency settled on an apparently simple solution: delay launching to 6.5 seconds after ignition of the orbiter's main engines. At this point the bending moment is reduced to about 190 million inch-pounds - once again well within hardware limits. The shuttle snaps back a smaller distance and clears the launch pad with ease.
But AbuTaha says it's not that simple. According to his calculations, the bending moment doesn't decrease steadily between four and seven seconds after the orbiter's main-engine ignition. On the contrary: it reaches a peak of nearly 590 million inch-pounds at five seconds after ignition, then declines. Although he worked out the curve independently, AbuTaha's figures agree with the results of a February 1981 ground test of the shuttle Columbia engine, as cited in aeronautics expert R.E. Gatto's article, "Effects of System Interactions on Space Shuttle Loads and Dynamics," which was presented to the International Council of Aeronautical Sciences Congress in 1982.
Why should the maximum stress on the shuttle occur five seconds after ignition? AbuTaha makes a "twang" analogy with a bathroom scale. If you weigh 150 pounds and step onto the scale gingerly, the needle will register 150 pounds with a minimum of fluctuation. But if you pounce on the scale from atop the nearby sink, the needle will oscillate wildly, perhaps ranging between 100 and 200 pounds in a series of increasingly smaller arcs, before settling on 150. Revving the orbiter's main engines to 100-percent capacity in one second delivers a shock to the assembly similar to jumping on the scale. The five-second point, says AbuTaha, is equivalent to the moment when the needle on the bathroom scale records its highest weight.
The Rogers Commission was not oblivious to shuttle "twang." But it rejected the idea that twang had anything to do with the Challenger disaster. Page 54 of the first volume of the commission's report states, "The resultant total bending moment experienced by [the Challenger] was 291 x 106 inch-pounds, which is within the design's allowable limit of 347 x 106 inch-pounds." However, on page 1351 of Volume Five of the report, the commission cites the same figure, written as "291,000,000," as the bending moment for the right solid booster only. The effect on the entire assembly, argues AbuTaha, should be the combined bending moments of both boosters. Multiply by two, and you arrive at the maximum force that AbuTaha calculated.
This figure is 70 percent greater than the design's allowable limit, as cited in the Rogers report. And every shuttle mission up to the Challenger explosion (and possibly afterward) has experienced this force. "This is the kind of error that catches up with you," warns AbuTaha.
Not only does this miscalculation explain the shuttle disaster that killed seven astronauts and set the U.S. space program back nearly three years, as AbuTaha suggests, it also reveals the source of the mysterious malfunctions that have plagued the shuttle program since its first launch in 1981, from tiles knocked off and booster segments warped to satellites that inexplicably failed to work.
He can't explain how NASA engineers missed the error, AbuTaha says, unless they were so concerned with the moment of liftoff and the few milliseconds after that they ignored the rest of the curve. "We have specialists who know everything about nothing," he says, "and generalists who know nothing about everything."
AbuTaha thinks NASA eventually adopted some of his findings without credit and used them in redesigning the space shuttle. But he claims that instead of remedying the fundamental problem, NASA has taken a Band-Aid approach, adding structural reinforcements to the lower section of the assembly. This has only shifted the liftoff stress to the cargo bay. One by one, AbuTaha ticks off recent satellites that failed after they were released from the shuttle's cargo bay: a Defense Department satellite payload that malfunctioned and burned up in Earth's atmosphere; camera problems in the Jupiter-bound Galileo probe; the trouble the Hubble Space Telescope had with its antenna, computers, and navigational system.
"These are problems that have nothing to do with lens grinders," he protests.
He was at home conducting research the morning the Challenger exploded, AbuTaha recalls. "The launch had been delayed several times, so I wasn't watching it on TV. My daughter came running in to tell me. I walked to the TV, saw the explosion, and still didn't
When the Rogers Commission released its report five months later, AbuTaha picked up a copy for professional reasons. Poring over its 3000 pages, he quickly suspected that some of the figures, such as the 291,000,000 inch-pound figure for the bending moment, were impossibly low. But if the vehicle had been overstressed from the beginning, the fact remained that 24 missions had flown without a major hitch. What made the Challenger different?
AbuTaha toyed with the idea that the shuttle assembly might have sustained structural damage before the launch. The Challenger was the first shuttle to be launched from pad 39B at Cape Canaveral. On the way from the assembly building to the liftoff site, the vehicle transporting the shuttle must make a sharp left turn. If the bulky but delicate shuttle assembly were to lean too far in one direction, he reasoned, it could be
AbuTaha approached NASA with his insights - eager to share his findings for the good of the space program. But he makes no bones about another incentive: as he turned up evidence of a major oversight in design, he hoped to land a sizable contract for his labors. A consulting contract of $75,000 to $100,000 was not out of the question.
On June 16, 1986, AbuTaha wrote then NASA director James C. Fletcher, current director Richard Truly, and others in the agency, advising them to search for "preflight" loads - damage caused to the shuttle before it left the ground. He also informed them of his "sharp left turn" theory. NASA took AbuTaha seriously enough that it allowed him to witness the roll-out of the shuttle Atlantis in October 1986. According to Myron Uman, who oversaw the redesign of the solid-fuel booster, NASA arranged the roll-out to test AbuTaha's theory, strapping stress gauges on the assembly. AbuTaha later discounted the sharp left turn theory as the major cause of the accident, although he still believes the stress might have been the nudge that sent the Challenger over the edge.
But that early, imperfect theory did not dissuade AbuTaha. Soon he was devoting virtually all his energy to his shuttle investigation without reimbursement - searching for forces unaccounted for in the official version. In an October 7, 1986, brainstorming session with NASA engineers at the Kennedy Space Center, AbuTaha says, he first learned about the change in launch procedure.
While at Cape Canaveral, AbuTaha was advised by Horace Lamberth, then director of shuttle engineering, to carry on his investigations. Lamberth referred him to the Marshall Space Flight Center in Huntsville, Alabama. AbuTaha wrote up his new suspicions about altered launch procedures in a report entitled, "A Failure Mode and a Missing Baseline," and submitted it to Marshall. On October 30, 1986, John Thomas, manager of the team that designed the solid rocket motor, responded to AbuTaha: "It is my view that it is unnecessary to pursue the thoughts contained in your report."
AbuTaha's criticisms were also dismissed by Admiral Richard H. Truly, then associate administrator for space flight, now head of NASA. "The configuration of the Shuttle at liftoff presents a very complex structural analysis challenge," Truly wrote. "The analytical models used for these calculations have evolved over the years and have proven to produce accurate predictions on how the various elements of the shuttle will behave when exposed to a given set of conditions. This flight was no exception."
In November 1986 AbuTaha's attorney, William D. Blakely, delivered a copy of his latest report to Morton Thiokol, the Utah firm that manufactured the shuttle's solid-fuel boosters. Thiokol's T.F. Garrison wrote, "The report is interesting and well-written," but sidestepped the questions AbuTaha raised. "We are solid-propellant rocket motor people and not expert on either vehicle dynamics or liftoff/flight loads. Therefore, we are not in a position to comment on or meet with Mr. AbuTaha concerning his report."
Shortly before Christmas AbuTaha presented L. Michael Weeks, deputy associate administrator for NASA, with visual evidence suggesting an alternate version of the Challenger accident. Both the Wall Street Journal and Aviation Week & Space Technology carried short reports about AbuTaha's campaign in December. AbuTaha was tight-lipped to the Journal, saying, "This is a jigsaw puzzle...I have to give NASA the pieces first." But NASA officials dismissed AbuTaha's analysis (see "Obviously a major malfunction...." sidebar).
Then, in 1987, as the shards of Challenger were being entombed in an abandoned missile silo, key NASA personnel began to express doubts about the thoroughness of the Rogers Commission investigation. On February 13, 1987, a memo written by John Young, head of NASA's astronaut office, was leaked to Washington Post reporter Kathy Sawyer. Young's memo inquired whether the shuttle was strong enough to stand up to the dynamic forces encountered during a launch, and whether NASA was capable of duplicating these forces during tests. The Post article revealed that in a November 1986 test, the aft skirt of a solid-fuel booster cracked under less stress than the Seventies predictions would have indicated. The aft skirt in question had flown three shuttle missions.
Astronaut Robert "Hoot" Gibson told the Post that damage to bolts on the solid-fuel boosters - which NASA had previously attributed to impact with the ocean - was actually taking place on the launch pad, during motor ignition.
This was exactly what AbuTaha had been trying to tell NASA for months. In a March 23, 1987, letter to NASA administrator James Rose, he complains, "A trend has set in. My findings are rejected out of hand in official letters. Then, months later, I find from the media or official sources that the same findings are discovered by NASA and the contractors."
Following the aft-skirt revelation, NASA increased stress standards for shuttle hardware by fifteen to twenty percent. The redesign of shuttle parts and construction of new test equipment delayed the first post-Challenger flight by an extra year.
By 1988 AbuTaha's funds were drying up, but he maintains he stuck with his investigation out of "duty to [his] adopted country."
"It had also become a matter of personal and professional credibility," he says. "When you know you're right, you can't walk away. You can't let NASA say you're an imbecile, that you don't know what you're doing."
In October of 1988 he applied to NASA's Inventions and Contributions Board for a monetary award. The board is authorized to reward researchers who have made significant contributions to NASA's space efforts. His claim was that NASA had used his data in redesigning the shuttle. After initially dismissing AbuTaha's application, the board scheduled an oral hearing for October 17, 1989.
As evidence AbuTaha cited the June 20, 1988, issue of Aviation Week & Space Technology, which reported that a new, $22 million hydraulic simulator was being used to apply forces of up to 330,000 pounds to test the strength of the solid-fuel booster where the struts (metal attachments) connect it to the liquid hydrogen/liquid oxygen fuel tank.
This figure of 330,000 pounds is significant. In his December 19, 1986, presentation of findings to NASA, AbuTaha had identified what he called a Rogers Commission error. Both solid-fuel boosters are connected to the fuel tank at the aft end by three struts each. The commission reported the total force exerted on the strut nearest the failed O-ring at 140,000 pounds. In Congress's independent investigation of the disaster (House Report 99-1016, October 29, 1986), the force on the struts is reported as 190,000 pounds. AbuTaha believes that the two figures refer to entirely separate forces. The 140,000 pounds represents the dynamic forces at liftoff. The 190,000-pound figure refers to "cryoloads" - shrinking stress induced on metal when supercold fuel is pumped into the fuel tank. Add the two forces together and you get 330,000 pounds, the amount NASA's new, improved hydraulic simulator was designed to deliver. AbuTaha claims he made his calculations abundantly clear to NASA in his December 1986 report.
NASA's Inventions and Contributions Board rejected AbuTaha's claims in writing, both before and after the appeal. Space agency officials asserted that the struts had been designed from the very beginning to withstand forces greater than 330,000 pounds and said, "Quoted media reports are secondary sources which are unreliable to establish facts."
As AbuTaha became convinced that NASA had neither understood his theories nor redesigned the shuttle to withstand the forces that he claimed were acting on it, he sought a greater audience. He gave two continuing education courses about the shuttle accident at George Washington University, and composed a shuttle expose, which was recently published in abbreviated form in the British journal, Professional Engineering.
This past April, shortly before the shuttle Discovery lofted the Hubble Space Telescope into orbit, AbuTaha wrote the team in charge of the mission, warning that excessive liftoff forces might damage the delicate instrument. Bob Crippen, former astronaut and current director of the space shuttle, curtly ended NASA's communication with AbuTaha with a written reply.
"In your most recent letter to NASA, you raise the same issues that previously have been analyzed and rejected. In light of this, I cannot justify any further expenditure of program resources to review what already has been done several times," Crippen writes. "[T]here comes a time when repetitive review becomes counterproductive. We have reached that point and...I have no choice but to consider the matter closed."
Following the mysterious hydrogen leaks that grounded the shuttle fleet, AbuTaha convened a July 9 press conference (his first) in Washington, D.C. He blamed the fuel leaks on the punishing liftoff stresses,and advised reporters that the existing fleet of three shuttles had been prematurely aged by these forces, citing a weakened midfuselage section, damage to the wings, and buckling of struts within the orbiter. NASA had counted on a shuttle lifetime of 100 missions before it had to be junked. AbuTaha said that figure needed to be revised downward.
AbuTaha also challenged NASA to a public debate on the issue of shuttle safety, but the space agency refuses to pick up the gauntlet. "We're not going to take him up on that," says NASA's Mark Hess flatly.
AbuTaha fears that another shuttle tragedy could kill the U.S. manned space program. The prospect of a NASA budget squandered on shuttle program overruns, leaving nothing for the space station or Mars exploration, disturbs him.
"Today, engineers who made the mistake and did not unravel it, before and after Challenger, design our planes, bridges, power plants, and other systems," he says. "Senior experts who reviewed my paper tell me the matter must be debated nationally, among our scientists and engineers. Must we wait for another tragedy?"
NASA, however, remains convinced of the essential soundness of the shuttle. It intends to send ten missions aloft in 1991, and another ten in 1992, when the new shuttle Endeavor becomes operational. But the final arbiter will be the laws of physics. As Rogers Commission member Dr. Richard P. Feynman concluded in his appendix to the commission report: "For a successful technology, reality must take precedence over public relations, for Nature cannot be fooled.
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