[meteorite-list] STS Astronaut Kenneth D. Cockrell on micrometeorite damage

[MARK BOSTICK]

Bio edited from NASA's website: Dr. Kenneth D. Cockrell was born April 9, 
1950 in Austin, Texas.  Cockrell received his commission through the Naval 
Aviation Reserve Officer Candidate Program at Naval Air Station Pensacola, 
Florida, in December 1972.  In the 1970's to the mid-80's Cockrell was a 
test pilot with experience flying A-4, A-7, F-4, and F/A-18  aircraft. He 
then reported to Naval Station, San Diego, for duty as a staff officer for 
the Commander of the USS Ranger and subsequently the USS Kitty Hawk Battle 
Groups. Cockrell was then assigned as a pilot in an operational F/A-18 
squadron and made two cruises on the USS Constellation in 1985 and 1987. 
Selected by NASA in January 1990, Cockrell became an astronaut in July 1991. 
  A veteran of five space flights, Cockrell has logged over 1,560 hours in 
space. He served as a mission specialist on STS-56 Discovery (April 8-17, 
1993), was the pilot on STS-69 Endeavour (September 7-18, 1995), and was the 
mission commander on STS-80 Columbia (November 19 to December 7, 1996, 
STS-98 Atlantis (February 7-20, 2001), and STS-111 Endeavour (June 5-19, 
2002).

Mark: Did any meteorite damage happen during any of the the STS flights you 
were on?

Kenneth Cockrell:

Statistically, significant damage from meteorites is almost non-existent. 
With many years in orbit, the MIR space station, the ISS, and their 
predecessors (Skylad, Salyut, ect.) suffered no damage that was ever 
detected by the crews or by any sensors on the vehicles.  With much shorter 
times in orbit, the space shuttle is even less liely to receive meteorite 
damage.

We do, however, take the possibility for damage seriously.  We don't fly the 
shuttle during the Perseus or Leonid acitivity.  We also have a leak repair 
kit as part of our inflight maintenance equipment that is designed to 
quickly patch a hole in the hull.

A slightly bigger risk for us is damge from "orbital debris," man-made 
objects in decaying orbits aorund the Earth.  The U.S. Space Command tracks 
the bigger pieces of this "space junk", and we plan our flights to avoid 
everything that we know about.  If any predicted conjunctions occur during 
flgiht, ground controllers will direct the crew to make an orbit adjusting 
maneuver to create a bigger predicted miss distance.  I have made two such 
burns in my career.  Debris that is too small to be tracked does 
occasionally hit the shuttle.  I don't think anyone has ever heard an 
impact, but many of us have found damage to a window, in the form of a tiny 
star-shaped crack (like might be made by a pellet gun to a car window) when 
we looked through it on a new day on orbit.

In the late '80's and early '90's, NASA did some research on the nature of 
space debris and micrometeorites using the Long Duration Exposure Facility 
(LDEF) satellite.  Space shuttle mission STS-32 retrieved LDEF from orbit.  
You might be able to find some of the results of that researhc on the NASA 
web site.

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LDEF information from NASA's website:

LDEF post-retrieval evaluation of exobiology interests
Bunch, T. E.; Radicatldibrozolo, F.; Fitzgerald, Ray
NASA Center for AeroSpace Information (CASI)
NASA, Washington, Fourth Symposium on Chemical Evolution and the Origin and 
Evolution of Life, p 110 , Oct 1, 1991
Cursory examination of the Long Duration Exposure Facility (LDEF) shows the 
existence of thousands of impact craters of which less than 1/3 exceed 0.3 
mm in diameter; the largest crater is 5.5 mm. Few craters show oblique 
impact morphology and, surprisingly, only a low number of craters have 
recognizable impact debris. Study of this debris could be of interest to 
exobiology in terms of C content and carbonaceous materials. All craters 
greater that 0.3 mm have been imaged and recorded into a data base by the 
preliminary examination team. Various portions of the LDEF surfaces are 
contaminated by outgassed materials from experimenters trays, in addition to 
the LDEF autocontamination and impact with orbital debris not of 
extraterrestrial origin. Because interplanetary dust particles (IDP's) 
nominally impacted the LDEF at velocities greater than 3 km/s, the potential 
for intact survival of carbonaceous compounds is mostly unknown for 
hypervelocity impacts. Calculations show that for solid phthalic acid (a 
test impactor), molecular dissociation would not necessarily occur below 3 
km/s, if all of the impact energy was directed at breaking molecular bonds, 
which is not the case. Hypervelocity impact experiments (LDEF analogs) were 
performed using the Ames Vertical Gun Facility. Grains of phthalic acid and 
the Murchison meteorite (grain diameter = 0.2 for both) were fired into an 
Al plate at 2.1 and 4.1 km/s respectively. The results of the study are 
presented, and it is concluded that meaningful biogenic elemental and 
compound information can be obtained from IDP impacts on the LDEF.


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Clear Skies,
Mark Bostick
www.meteoritearticles.com