What caused the American space shuttle Columbia to crash?

A piece of foam that fell off the fuel tank shortly after the launch of the American space shuttle Columbia has always been a big doubt in the accident investigation. An analysis report released by NASA shows that the space shuttle may be hit by as many as three bubbles instead of one as previously thought [4].

The space shuttle Columbia was launched on June+10/October 16, 65438. 1October 24+65438, the technical staff of Boeing Company, the contractor of the space shuttle project, wrote this report and submitted it to the flight control department of NASA on1October 27+65438. According to the report, 82 seconds after the launch of Columbia, three pieces of foam, each about 20 inches (50 cm) long, fell off from the support area connecting the external fuel tank and the space shuttle. After hitting the space shuttle, they "seemed to disintegrate" and became many smaller pieces.

In publishing this report, NASA stressed that according to the conclusion of the report, the impact of foam debris will not affect the flight safety of the space shuttle, and the flight control department of NASA also "agrees with this conclusion".

Nevertheless, after the publication of the new report, the impact of foam materials on the "Columbia" accident once again attracted people's attention. 1 The problem of foam fragments surfaced shortly after the disintegration and crash of Columbia in February. Although NASA has always insisted that the impact of foam fragments will not cause serious consequences, the independent Committee responsible for investigating the "Columbia" accident is still conducting in-depth analysis of the impact of foam fragments. At present, the main conclusion of this independent investigation Committee is that there may be loopholes in the shell of Columbia, which may lead to ultra-high temperature gas entering the space shuttle and eventually lead to an accident. According to the document published by NASA 2 1, an engineer of NASA warned in an e-mail on1October 29th that the damage of the external thermal insulation tile of the space shuttle may lead to cracks in the wheel compartment or landing gear door.

Follow-up investigation on August 13, 2004 further confirmed that the defects in the installation of foam materials on the external fuel tank of the American space shuttle Columbia were the chief culprit of the whole accident. According to the investigation report released by the Columbia Space Shuttle Accident Investigation Committee last year, a piece of foam material falling off the surface of the external fuel tank hit the material named "reinforced carbon" (that is, reinforced carbon-carbon insulation board) on the front edge of the left wing of the space shuttle. When the space shuttle returned, it passed through the atmosphere, resulting in fierce friction, which made the air with the temperature as high as 1400 degrees Celsius rush into the left wing and melt the internal structure, resulting in the melting of the wing and fuselage, leading to the tragedy.

Photography in the cockpit [5]

After the accident, NASA and the accident investigation Committee have not yet reached a final conclusion on the cause of the accident because the foam materials and fuel tanks at the time of the accident could not be quickly retrieved for inspection. At present, about 500 thousand pieces of Columbia's external fuel tank have been found and reassembled. Neil Ott, chief engineer of NASA in charge of the external fuel tank project of Columbia University, said that after many tests, NASA determined that defects in the installation process of foam materials were the main cause of the accident.

Ott said that there is no problem with the chemical composition of the foam itself, but the problem lies in the process of spreading the foam outside the fuel tank with a spray gun. The test shows that the current laying process will leave gaps between foam materials, in which liquid hydrogen can penetrate. After the space shuttle took off, hydrogen was heated and expanded, which eventually led to large foam falling off. The foam material that hit Columbia was the size of a briefcase and weighed about 0.75 kg. Almost a kind of material called "reinforced carbon" (reinforced carbon-carbon insulation board) was torn off in one piece, which hit the leading edge of the left wing of the space shuttle at high speed and formed cracks. When the space shuttle re-enters the atmosphere, ultra-high temperature gas can enter Columbia from the crack, leading to the disintegration of the space shuttle.

Fragments [6]

Ott said that testing the fuel tank according to the new standard is the biggest obstacle that NASA is currently facing. The new standard requires that foam materials exceeding 0.5 ounces (14.17g) outside the fuel tank should not fall off. NASA is currently preparing to test 1 1 fuel tanks of all space shuttles, and it will cost $40 million to check each fuel tank. Experts from the accident committee of the American Space Shuttle Columbia pointed out that the strong wind during takeoff, the temporary replacement of the rocket booster before launch and "being too old" may be the fundamental reasons for the disintegration of the meritorious spacecraft. After taking off for 62 seconds, Columbia suddenly encountered an unusually strong wind, which may lead to "internal injuries" in its left fuselage, laying the foundation for future crashes. Only 20 seconds later, the foam insulation material falling from the main fuel tank at the lower part of the fuselage hit the front end of the left wing, causing direct "trauma". Experts believe that these damages may be nothing to a space shuttle that has been used for 10 years, but they are fatal to an "old machine" like Columbia with a history of 2 1 year.

The investigation Committee pointed out that the relevant parties are studying whether NASA paid insufficient attention to the problem of "physical aging", which eventually led to this tragedy. At present, the direct cause of the "Columbia" crash is basically determined: ultra-high temperature air invaded the lower part of the heat insulation tile from the gap on the surface of the fuselage and fled everywhere, which eventually led to the disintegration and crash of the space shuttle on the way back, killing seven astronauts. It is reported that one minute after the plane took off, the wind intensity encountered was close to the limit allowed by NASA. Therefore, experts believe that the wings that have begun to age are easily impacted by foreign objects because of such strong winds, thus being damaged, forming a "convenient rear" for the ultra-high temperature air invasion on the way back.

In addition, in August last year, the rocket booster rocket that normally matched the main fuel tank of Columbia was dismantled and installed on another space shuttle that was about to take off. It was not until June of that year165438+1October that NASA reinstalled a new booster rocket for Columbia University. It may be that in this "unnecessary" disassembly process, the operation of the relevant personnel caused damage to the surface material of the fuel tank, which led to the insulation material falling off and hitting the left wing of the space shuttle. In addition, due to the "older age", there may be "defects" under the super-strong carbon fiber insulation board at the front end of Columbia's left wing. In the past 10 years, similar components of other space shuttles have also suffered different degrees of damage, including the dangers of external force (small meteorites) impact, scratches, poor sealing and so on.

The investigation Committee pointed out that it is necessary to find out whether NASA timely inspected and replaced the above-mentioned vulnerable parts of the American space shuttle, including Columbia. It is reported that "Columbia" was first launched at 198 1, which is the longest-serving space shuttle in the United States. The ground wind tunnel test after the accident found that Columbia's last-minute tumbling flight was caused by the loss of the protective layer at the front end of the left wing. Experts estimate that at least five U-shaped insulation boards fell off at that time to produce such a strong pulling force. At present, searchers have found more than two. 80,000 pieces of Columbia wreckage were sent to Kennedy Space Center for analysis and investigation. It is reported that these things are only 19% of Columbia's huge fuselage.

final report

structure

On June 30, 2009, 65438+February 30, the National Aeronautics and Space Administration (NASA) released the final investigation report of the space shuttle Columbia, describing in detail the last situation in the cabin before the disintegration of Columbia. The report also pays attention to the safety of astronauts and puts forward some suggestions for improvement. In 2003, the space shuttle Columbia crashed on its way back, killing all seven astronauts. NASA then launched an in-depth investigation [7].

Compared with the investigation five years ago, this 400-page final report restores more details of the astronauts' activities in the cabin before the disintegration of Columbia. According to the report, it only took about 1 minute from the alarm in the "Columbia" cabin to the end of the astronaut's life. The space shuttle was out of control, and astronaut William McMahole pressed several buttons to try to control it. Most other astronauts also follow the established procedures of NASA. At this point, they didn't know that bad luck was coming, and they didn't take the time to prepare. Three astronauts didn't wear protective gloves, 1 didn't sit in chairs, 1 didn't wear helmets. A few seconds later, the crew cabin of Columbia lost pressure. According to the report, the lack of oxygen caused by the pressure drop led to the death or coma of astronauts, and the comatose person subsequently died of fatal impact during the violent rolling and shaking of the plane. According to the report, even if astronauts have time to put on protective clothing to pressurize themselves after the plane loses pressure, they can only live for a while, and it is still impossible to survive.

Memorabilia of the plane crash at 20: 00 Beijing time: "Columbia" is in an orbit 280 kilometers above the ground.

Space shuttle Columbia (18)

Flying around the earth, the crew got the green light signal from the Houston ground mission control center and began to make final preparations for re-entry into the earth's atmosphere [8].

At 20: 49 Beijing time, NASA issued an order to start landing and reposition Columbia. At that time, there was fog over the landing zone at Cape Canaveral, Florida.

At 2 1 09, the fog in the sky dispersed. Leroy Kahn, the return commander, gave Columbia an order to leave Earth orbit.

At 2 1 15, Columbia flew over the Indian Ocean. At this time, the small direction control rocket engine on Columbia was turned on for 3 minutes. The tail of the space shuttle is facing the earth and begins to land.

2 1: 23, the automatic navigation system of inertial guidance computer instructs the space shuttle to adjust to the posture with the front end in front and the tail down.

At 2 132, the auxiliary power unit is turned on, which increases the pressure for the hydraulic system controlling the aileron and landing gear of the space shuttle.

2 1: 42, Columbia reached the position of 144 km over the Pacific Ocean. At this time, the rocket engine is working at a speed of 27,000 km/h (25 times the speed of sound).

2 1: 44, "Columbia" began to "enter the atmosphere", and its front end rose upward, maintaining an elevation angle of 40 degrees, so that the ceramic heat-resistant tiles outside the space shuttle could bear all the heat generated by the friction between the aircraft and the atmosphere when entering the dense atmosphere. Ceramic heat-resistant tiles began to heat up.

2 1: 46, Columbia is only 102 km from the ground, and will land in 30 minutes. Gradually, it crossed the Gulf Coast of California, Nevada, New Mexico, Arizona, Texas and Louisiana, and finally reached Florida.

2 1: 49, Columbia began to slow down gradually as planned, and its front end flew to the right.

At 2 152, Columbia crossed the coast of California. According to the control records of Houston ground mission control center, the temperature of the left landing gear of the space shuttle has slightly changed abnormally. The temperature of the left landing gear displayed by three hydrothermal sensors is between 40 and 60 degrees Fahrenheit (8 to 15 degrees Celsius).

2 1: 53, the fourth sensor on the left wing of the space shuttle shows that the temperature is still rising.

2 1: 54, due to the rising left wing temperature, the whole fuselage temperature rose by 15 degrees Celsius.

2 1: 55, Columbia flies over the Nevada desert.

At 2 1: 56, Columbia flew over southern Arizona.

2 1: 57, when flying over new Mexico, the space shuttle still controlled by the automatic navigation system began to deflect to the left, and the speed dropped again. The Houston ground mission control center lost contact with the data transmission of the left wing temperature sensor of the space shuttle.

2 1: 58, an unexplained force on the left side of the space shuttle pushed Columbia to roll to the left, and the trim rolling stabilizer opened automatically, trying to correct the landing position of the space shuttle.

At 2 159, the onboard computer on the space shuttle tried to further correct its position by starting two yaw jet thrusters. Columbia entered Texas at an altitude of 6 1 km above the ground and at a speed of 2 1 1,000 km per hour. Mission control in Houston recorded the last radio contact signal: "Columbia, this is Houston. We saw your tire pressure information, but didn't copy your last data. "

After a while, Rick Husbanddouglas, the captain of Columbia, replied, "Yes, but ..."

After hearing a short wave noise, the ground lost contact with Columbia.

At 22: 00, Houston ground mission control center continued to track Columbia on the radar without any radio contact. Witnesses on the ground reported that they saw the Columbia break into countless small pieces and drag long white smoke across the sky.

At 22: 16, NASA officially launched the accident emergency plan at the scheduled landing time of the space shuttle Columbia.