What If a Shuttle Orbiter Struck a Bird? (1988)

Final approach: the Shuttle Orbiter Discovery lands on the Shuttle Landing Facility at Kennedy Space Center, Florida, at the end of its longest mission (STS-131, 5-20 April 2010). Image credit: NASA.

The first NASA astronaut to die in the line of duty was U. S. Air Force Captain Theodore Freeman. Little known today, Freeman was a member of the third astronaut selection group, which NASA introduced to the world on 18 October 1963. The group included 10 astronauts who would become famous — Michael Collins, Edwin Aldrin, Alan Bean, David Scott, Russell Schweickart, William Anders, Eugene Cernan, Walter Cunningham, Donn Eisele, and Richard Gordon — and three besides Freeman who would perish before reaching orbit — Clifton Williams, Roger Chaffee, and Charles Bassett. Of the seven pre-Shuttle NASA astronaut groups, Group 3 experienced more pre-flight astronaut deaths than any other.

The astronauts had at their disposal Northrop T-38 Talon supersonic training aircraft. They used them in two basic ways: for training sorties to accumulate flight time so that they could keep their piloting skills well honed and retain their flight status, and as readily available, speedy transportation to NASA and contractor facilities and training sites across the United States. Transportation flights also contributed to the flight time requirement.

On 31 October 1964, 34-year-old Freeman took off alone in a T-38 from Ellington Air Force Base, located between downtown Houston, Texas, and NASA's Manned Spacecraft Center (MSC). He began his training sortie by flying over MSC, then out over Clear Lake and Galveston Bay.

NASA's Third Astronaut Group. Theodore Freeman is in the back row, fourth from left. Image credit: NASA.

As he returned to Ellington, a flock of Canadian geese took wing to one side of his flight path. As he made a turn, the flock rose up around his T-38, and one bird struck and shattered the plane's plexiglass forward canopy. Plexiglass shards entered the jet's twin engines through their air intakes. Moments later, the engines began to fail.

The eight-pound goose did not enter the T-38's intakes, though some sources report that it did. In fact, after striking the canopy, it struck the plane's rear seat, then spun away along the jet's upper fuselage.

Freeman tried to line up with an Ellington runway, but the engines flamed out and his plane began a steep dive at low altitude. He ejected, but before his parachute had time to open he struck the ground and was killed.

In October 1983, nearly 20 years after Freeman's untimely death, The Christian Science Monitor published a puff piece on NASA's efforts to keep wild pigs and alligators off the 15,000-foot-long, 300-foot-wide Shuttle Landing Facility (SLF) runway at Kennedy Space Center (KSC) in Florida. The story was timely because NASA aimed to achieve its first Orbiter landing at the SLF in January 1984. The space agency had planned to land Challenger at the SLF at the end of mission STS-7 on 24 June 1983, but had to divert it to Edwards Air Force Base (EAFB) in California after KSC became fogged in.

The north end of the SLF is about a mile from the Visitor Center for the Merritt Island National Wildlife Refuge (MINWR). MINWR and KSC both owe their origin to President John F. Kennedy's 25 May 1961 "Moon Speech." In 1962-1963, NASA acquired more than 140,000 acres of orange groves, swamp, and beaches to create a safety buffer around its Apollo Saturn V launch pads and other facilities. As landowners moved out, sometimes grudgingly, wildlife moved in.

On 28 August 1963, the space agency and the U.S. Fish and Wildlife Service agreed that the latter would manage the roughly 90% of KSC that NASA did not actively use. The interagency agreement assumed that KSC activities would increase over the course of the 1960s and 1970s and that its facilities would steadily expand. Apollo-era construction leveled off in 1966-1967, however.

Major facilities expansion did not begin again at KSC until April 1974, when the Morrison-Knudsen Company began work on the $22-million-dollar SLF. The facility, modeled on flight research runways at EAFB, was completed in 1976. It became KSC's airport, supporting astronaut T-38s, Gulfstream II Shuttle Training Aircraft, and other planes and helicopters. The first space-worthy Orbiter, Columbia, arrived at the SLF atop a 747 carrier aircraft in March 1979.

The Shuttle Landing Facility. Image credit: NASA.

A NASA spokesman told The Christian Science Monitor's reporter that KSC and MINWR played host to "all kinds of bald eagles, vultures, lots of brown pelicans, and ducks in winter." This was, however, not of great concern; the Shuttle Orbiter was a glider, he explained, so lacked air intakes that might ingest birds.

The Christian Science Monitor reporter wrote that the Orbiter had "triple-strength windows." This was a reference to the design of the six windows making up the flight deck windshield; each was three panes thick, with empty spaces between the panes. The outermost pane, the "thermal" pane, was attached to the fuselage structure; the innermost pane, the "pressure" pane, was attached to the crew cabin structure. Between these, also attached to the crew cabin structure, was a thick "redundant" pane.

The article affected an almost humorous tone as it described measures aimed at keeping alligators and wild pigs off the SLF. It seemed impossible that the Space Shuttle, a pinnacle of U.S. technological know-how, could ever be harmed by mere animals. Its author did suggest, however, that running over alligators basking in the Sun on the SLF runway might damage the Orbiter's "delicate landing gear."

On its second try, at the end of mission STS 41-B in February 1984, Challenger glided to a safe landing on the SLF runway. NASA hailed the landing, little more than five miles from the launch pad Challenger had left just eight days before, as a major step toward routine Shuttle flights and Shuttle launch rates of up to 25 per year.

A little less than two years later, on 28 January 1986, Challenger disintegrated 73 seconds after liftoff from KSC's Pad 39B, killing its seven-person crew. The disaster revealed that the Shuttle stack — twin reusable Solid Rocket Boosters, expendable External Tank, and reusable delta-winged Shuttle Orbiter — was much less robust than many had assumed.

Under intense scrutiny, NASA commenced a wide-ranging examination of Space Shuttle systems and operations. The U.S. civilian space agency soon found that many of its comfortable assumptions were incorrect.

Shuttle windshield: the Orbiter Endeavour during mission STS-123 (11-27 March 2008). Image credit: NASA.

Karen Edelstein, with NASA's Johnson Space Center, and Robert McCarty of the Wright Aeronautical Laboratories at Wright-Patterson Air Force Base in Ohio, reported on results of their study of bird impacts on the Orbiter windshield. They determined that, far from being triple-strength, it was "a poor barrier to bird impacts."

In fact, computer modeling using a refined version of the U. S. Air Force Material and Geometrically Nonlinear Analysis (MAGNA) program showed that, in every case, a four-pound bird — for example, a typical turkey vulture — would penetrate all three windshield panes in less than a second and enter the flight deck if the Orbiter were moving above an indeterminate speed between 150 knots (172 miles per hour) and 175 knots (201 miles per hour). They noted that the Orbiter traveled at up to 355 knots (408 miles per hour) as it fell past 10,000 feet and 195 knots (224 miles per hour) as its rear wheels touched the SLF runway.

This meant that at no time during descent through altitudes where birds fly did the Orbiter's windshield provide protection from bird strikes. In fact, the crew on the flight deck remained vulnerable until about the time the Orbiter's nose gear touched concrete.

Edelstein and McCarty did not examine in detail a bird impact leading to a partial window failure; for example, broken thermal and redundant panes and an intact pressure pane. This scenario was expected to occur at speeds as low as 150 knots. One may speculate that at the very least a partial failure would make the affected window essentially opaque; it might also create extra drag, altering the handling characteristics of the Orbiter.

A turkey vulture. Its wingspan is about six feet. Image credit: Wikipedia.

They noted that, short of a major redesign, there was little NASA could do to beef up the Orbiter windows. They urged designers of future space planes to seek materials more sturdy than glass when designing their windshields.

The Edelstein and McCarty paper did not lead to a major Orbiter redesign or new Orbiter window materials; NASA's allotted budget would not extend that far. Instead, the space agency redoubled its efforts to scare birds away from the SLF. Mostly it relied on loud noises.

For a time in the mid-1990s, however, KSC seriously considered putting falconers on its payroll. A June 1994 study noted that falcons had been used intermittently since the 1940s to kill or scare away birds at airfields in the U.K., the Netherlands, Spain, France, Canada, and the United States.

The study determined, however, that most of the more than 300 bird species that spent at least part of the year in MINWR had little experience with falcons, so were unlikely to be frightened by them. Falcons, for their part, were likely to be confused by wading birds such as herons and egrets.

The birds most threatening to Orbiters and other aircraft at the SLF, the 1994 study found, were various species of vulture. These were too large and numerous for falcons to tackle. It noted that groups of up to 30 individuals were frequently found around a single roadkill and that a "roost" of about 300 vultures had become established on the SLF runway's southern approach path.

The vultures, which weighed up to five pounds, took to the skies to ride thermals over KSC beginning in mid-morning. Mostly they glided lazily between 150 and 1800 feet above the ground. The air currents rising off the 526-foot-tall Vehicle Assembly Building were especially attractive to them. If the birds smelled a carrion buffet, however, they could fly rapidly, thwarting efforts to track and deter them. Loud noises, effective in driving away most other birds, were of little concern to vultures.

During the mid-morning launch of the Orbiter Discovery at the start of mission STS-114 on 26 July 2005, a vulture collided with the External Tank before the Shuttle stack cleared the Pad 39A launch tower. The bird probably weighed more than twice as much as the 1.7-pound chunk of External Tank foam insulation that had struck and breached Columbia's left wing leading edge on 16 January 2003, 82 seconds into mission STS-107. The foam chunk was estimated to have been moving at about 525 miles per hour when it hit the wing.

During Earth-atmosphere reentry on 1 February 2003, hot gases entered Columbia's left wing through the breach and rapidly destroyed its aluminum internal structure. NASA's oldest Orbiter broke up, killing the seven-member STS-107 crew.

Though the low-speed bird impact caused no obvious damage to the External Tank, NASA took notice because it occurred during launch of the first Shuttle mission since STS-107. The vulture might easily have struck a more vulnerable part of the Shuttle stack, or have struck it at a higher altitude, after the Shuttle had gained speed. KSC managers decided to apply SLF bird control techniques to the twin Shuttle launch pads. They also adopted a launch-day vulture "trap-and-release" policy.

By 2009, KSC's Bird Abatement Program relied on quick removal of roadkill to eliminate a major scavenger food source and pare down vulture numbers, bird detection radar and cameras, sirens, shotguns firing blanks and whistlers, and 25 liquid-propane-fueled "cannons." Installed along the SLF in 2007, the noise-producing cannons could be set off from the SLF runway control tower or by bird observers on the ground. They could also be set to fire automatically at random times and in random directions. Despite these measures, the risk to the Shuttle from bird strikes persisted until the Orbiter Atlantis rolled to a stop on the SLF runway at the end of STS-135, the final Shuttle mission, in July 2011.

Sources

"Space Shuttle Orbiter Windshield Bird Impact Analysis," ICAS-88-5.8.3, K. Edelstein and R. McCarty, Proceedings of the 16th International Council on Aeronautical Sciences Congress held in Jerusalem, Israel, 28 August-2 September 1988, Volume 2, pp. 1267-1274.

A Review of Falconry as a Bird Control Technique With Recommendations for Use at the Shuttle Landing Facility, John F. Kennedy Space Center, Florida, U.S.A., NASA Technical Memorandum 110142, V. Larson, S. Rowe, D. Breininger, and R. Yosef, June 1994.

"History of the Shuttle Landing Facility at Kennedy Space Center," E. Liston and D. Elliot; paper presented at The (40th) Space Congress in Cocoa Beach, Florida, 28 April-2 May 2003.

Fallen Astronauts: Heroes Who Died Reaching for the Moon, Revised Edition, C. Burgess and K. Doolan with B. Vis, University of Nebraska Press, 2016, pp. 1-45.

"NASA Tries To Keep The Hogs and 'Gators Off the Shuttle's Runway," G. Klein, The Christian Science Monitor, 12 October 1983 (https://www.csmonitor.com/1983/1012/101225.html - accessed 17 December 2017).

"It's a Jungle Out There!" L. Herridge, 26 June 2006 (https://www.nasa.gov/mission_pages/shuttle/behindscenes/roadkill.html - accessed 14 December 2017).

"Bye, Bye, Birdies," C. Mansfield, 30 June 2006 (https://www.nasa.gov/mission_pages/shuttle/behindscenes/avian_radar.html - accessed 16 December 2017).

"Bird Team Clears Path for Space Shuttles," L. Herridge, 12 August 2009 (https://www.nasa.gov/mission_pages/shuttle/behindscenes/clearbirds.html - accessed 14 December 2017).

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