What happened during the final hour of Mir's life?

"It was pretty stunning. There was something very peaceful about it. It is an emotional process. Very graceful."

"It was a stunning blue streak followed by a sonic boom. The pieces had a blue incandescence to them."


Mir burns up in the skies above Nadi, Fiji

In less than an hour, the Mir space station, which survived more then 15 years in space, passed into history as it streaked to its final resting place in the South Pacific. Experts disagreed on some of the details during the final hour of Mir's life, but there was little doubt about the sequence of events--realities enforced by the laws of physics.

***The final hour began with the attached Progress freighter's last firing of its braking rocket. According to Russian Mission Control, the station was 50 km (31 mi) above the Earth's surface at 12:55 a.m. EST (05:55 GMT, 8:55 a.m. Moscow time). Less than a minute later, it had fallen to 39 km (24 mi). At 12:58 a.m. EST (05:58 GMT, 8:55 a.m. Moscow time) fragments of the station hit the ocean.

For the first few minutes Mir continued to fly at more than 17,500 mph, losing altitude with each passing second. The Earth's atmosphere begins to thicken significantly at an altitude of around 400,000 feet. At this point, the air molecules become dense enough to have an impact on a reentering object or vessel, such as the space shuttle. Starting at this point, the 135-ton Mir began to contend with two destructive effects of reentry: heat and pressure.

Friction from flying through the air at more than 5 miles per second will cause the station's exterior to heat up, with some parts reaching more than 2,500 degrees Fahrenheit. It's titanium metal skin, carbon fiber from its heat shields, as well as the glass in its solar panels will begin to melt, erode, then break and pull away from the station. The electricity-generating solar wings, the communications antennae, handrails and other small items will quickly fall prey to the heat.

As it hurtled earthward, Mir's spindly structure weakened and the station's six main modules were torn asunder, become independently flying objects. Between the burning metal and the increased density of the air, any pressurized tanks that made it this far will mot likely rupture, possible leading to explosions. There was also the possibility that any remaining thruster propellant in Mir's tank or the Progress freighter might rupture, adding to the fireworks.

Having been slowed down by all the friction, the pieces of Mir probably hit the water with speeds ranging from 125 mph to about 600 mph. According to the projections, a five-pound piece of Mir made of titanium and about the size of a softball hit the water about 125 mph, while a Volkswagen Bug-sized piece weighing about 2,200 pounds would strike at about 325 mph.

Question:  Before Mir's reentry, experts predicted that "nobody will see Mir's last minutes."
Answer:  ***Mir disappeared from all global radars 40 minutes before its splashdown because neither America's mission control in Houston nor the European Space Agency was able to track the fragments during this period. Why? Although the Americans have a radar on the Fiji Islands, its visibility zone is just 2 degrees and it can only spot objects that follow almost along the horizontal. Possibly tourists on commercial flights could have gotten lucky, but this was unlikely because the area of the splashdown is too large.

Question: Before Mir's reentry, there were reports of concerns that certain bacterial mutants that allegedly exist aboard Mir may start multiplying in the ocean, thereby causing unpredictable consequences on Earth. Why do you think?
Answer: This scenario is highly unlikely. Firstly, no dangerous microorganisms have ever been discovered on the station. Secondly, if they did exit, they would inevitably have perished on the station entering the atmosphere because even metal, to say nothing of living organisms, cannot withstand the heat accompanying the process.

Click on the image to see a schematic explanation of Mir's reentry.

 

 

Click here to see the video (27 Mb) of Mir's reentry.

Click here to see an animation of the crash (a theoretical depiction based on real Mir spacecraft configuration and U.S. Space Command orbital information).

Click here to learn about Mir's many modules through this interactive graphic (Flash).