How do American missiles destroy runaway satellites? What will happen if they miss?

At 9: 07 EDT on 20th (22: 07 Beijing time on 20th), the space shuttle Atlantis returned from the International Space Station and landed safely at Kennedy Space Center as planned. This means that the last obstacle for US warships to launch missiles to destroy the runaway spy satellite "US 193" has been removed. The U.S. Department of Defense said that after the space shuttle Atlantis landed, the U.S. military immediately entered the window time to shoot down the out-of-control spy satellite, and the military would take action at an appropriate time. It is also reported that the weather in the North Pacific is not good and the time may be delayed.

Previously, the United States had been hoping to wait until the space shuttle Atlantis landed successfully before implementing the plan to hit the satellite. Although Steve Frick, commander of the space shuttle Atlantis, believes that the orbits of the space shuttle and the satellite are completely different, and the height of the space shuttle is much higher than that of the current satellite, even if the missile hits the satellite before the landing of Atlantis, the risk of hitting Atlantis is very small.

The Xinhua News Agency quoted the Associated Press as saying that the US military has issued a notice asking planes and ships to stay away from the vast sea area and its airspace in the Pacific Ocean west of Hawaii at 2 1: 30 EDT (Beijing time 10: 30) on the 20th. This shows that the first "time window" for the United States to launch interceptor missiles is about to open.

The first "time window" will close at 0: 00 a.m. EDT (2 1 GMT 13). If no action is taken during this period, the cruiser "Lake Erie" equipped with Aegis anti-missile defense system and standard -3 missiles will be closed from 2 1: 30 EST to 22: 00 GMT (10: 30 GMT), and it has been put in place hundreds of kilometers west of Hawaii.

According to the data, the "USA 193" satellite, also known as L-2 1, was developed by Lockheed Martin Company and is worth millions of dollars. The weight of this satellite is between 5000 pounds (2.26 tons) and 10000 pounds (4.53 tons). It was launched in vandenberg air force base, California in 2006, about 70 kilometers from the scheduled orbit of 280 kilometers above the ground. Due to the rapid loss of contact with the ground, the satellite never received instructions to carry out reconnaissance missions. The toxic fuel hydrazine used to change the direction of the satellite also accumulated in the satellite and was not used. The satellite also carries complex and secret imaging sensors.

process analysis

How to hit three missiles?

The bull's eye is the fuel tank.

The "forbidden zone" has been defined. Chen Hu, a military expert and executive editor of World Military magazine, is concerned about the attack height, attack time, the actual number of missiles launched and the accuracy of missile hit.

The attack altitude is when the satellite descends to 150 miles (about 24 1 km) from the earth's surface. According to the US military, striking at this altitude can ensure that the debris will not stay in space on the one hand, and make most of the debris burn due to air friction when entering the atmosphere on the other hand. "This height is still a long way from hitting an orbiting satellite, at most it is hitting the perigee of a low-orbit satellite, or a falling satellite like this, or a ballistic missile." Chen Hu told reporters.

Second, the attack time. According to the Pentagon, the best time to intercept satellites on the evening of 20th local time in the United States is two and a half hours. If the interception of that day is delayed or failed for some reason, the US military still has a chance to launch again, as long as it is before the first week of March when the satellite is expected to hit the Earth. The exact time will be ordered by US Secretary of Defense Gates who is in charge of the Hawaiian Fire Slave Lu Lu badminton Command Center. Chen Hu said: "The time window for shooting down out-of-control satellites is very long, and the time to take action from the United States can evaluate its reaction speed."

Third, about the three standard -3 interceptor missiles that have been prepared. Chen Hu believes that in order to obtain as much experimental data as possible, it is possible to continue launching after an impact. US Naval Operations Secretary Roughead said, "We will only launch one missile at a time. After the first missile is launched, there will be a day or two to evaluate the impact effect. If you feel dissatisfied, prepare for the second or third launch. "

The hit accuracy that the missile wants to achieve also attracts attention. It is reported that the American interceptor missile will take the fuel tank containing 453 kilograms of hydrazine on the satellite as the "bull's eye", not a runaway satellite the size of a bus.

The missile will destroy the out-of-control satellite in a head-on collision way. If successful, the satellite debris will weigh more than 4 tons after passing through the atmosphere, and its debris will be scattered within hundreds of miles in diameter. The US Air Force will send a specially modified aircraft to capture samples of toxic gases that may be produced after the satellite is destroyed. The Navy's "Observation Island" intelligence ship is responsible for all intelligence gathering before and after this operation.

It is estimated that this interception will cost about $60 million.

Accuracy: "50% is a conservative estimate"

The 50% chance of success is judged by David Wright, a senior expert of the American Federation of Scientists who is concerned about nuclear issues. In this regard, Chen Hu believes that "this is a conservative estimate".

One of the difficulties in satellite shooting lies in its low infrared characteristics. Chen Hu said, "Shooting down a satellite that crashed out of control is technically more like an anti-ballistic missile test. However, because the escape satellite has almost no heat source except sunlight, the temperature is much lower than that of the missile warhead, that is, the infrared characteristics are lower than that of the missile. Therefore, the US military's transformation of interceptor missiles this time is mainly aimed at this. " A ballistic expert in Shanghai also said that the US anti-missile interceptor mainly tracks by observing the infrared signal from the target, so the US Navy specially improved the relevant software this time to make up for the difficulty of insufficient heat source. The improved standard -3 missile is a heat-guided missile and is more sensitive.

The second difficulty lies in positioning. "For a missile, its subsequent trajectory can be calculated by monitoring a section of its orbit. However, because the crashed satellite has no predetermined orbit, the falling route may change randomly, so from this level, its interception is more difficult than missile interception. " The expert said.

The third difficulty naturally lies in the target itself: to hit the fuel tank accurately, not the whole satellite.

"Nevertheless, the success rate should exceed 50%." Chen Hu believes that since the problem of infrared characteristics has been solved, the time window of this attack will be longer, and there will be plenty of calculation time if the falling route of the satellite does not change unexpectedly. The expert also added: in the case of anti-missile interception, the missile may release bait or avoid intercepting the missile by means of multiple warheads, but the falling satellite will not take corresponding deception, so it is relatively easy to intercept the satellite at this level.

According to US military officials, the success rate of this operation can reach 80%. Chen Hu pointed out that the confidence of the US military can be seen from two aspects: one is the precise setting of the "bull's-eye"; Second, the US military uses impact kinetic energy warheads for interception, not explosive warheads, which obviously means that there is no need to increase lethality through explosion.

What happens if you miss?

If all three missiles prepared by the US military fail, what is the probability that "US Army 193" will hit a densely populated area? What are the consequences of hydrazine, a toxic substance?

First of all, it is almost impossible to predict the exact release position in advance and respond. Jonathan mcdowell, an astrophysicist at the Smithsonian Center of Harvard University, told this reporter that it is theoretically possible to calculate the descent trajectory of "USA 193", but the problem is that after it enters the atmosphere, the descent rate of the satellite will be affected by the atmospheric density, and the latter will be affected by the unpredictable dark spots of the sun. Therefore, it is an "impossible task" to predict the specific landing site even a few hours in advance. At present, it is known that this satellite may fall anywhere between 58.5 degrees north and south latitude.

Tim Gilder, a political scientist at the University of Maryland, made a calculation: According to the data provided by the US military, the maximum radius of fuel hydrazine carried by the "US 193" satellite is 27 meters, and the area is about 1/4 hectares. According to this calculation, if the population affected by pollution exceeds 1, then the average population per hectare in this area should be more than 4. According to the scanning map of population density drawn by Oak Ridge National Laboratory, between 58.5 degrees south latitude and 58.5 degrees north latitude, about five thousandths of the area has an average population of more than four people per hectare. The possibility of affecting more than three people (including three people) is two in a thousand. According to NASA's calculation, if "America 193" is hit by a missile, the probability of its debris colliding with the International Space Station will reach one in a thousand. Coincidentally, there are just three astronauts working in the space station at present. "The risks are similar." This is the main reason why Gilder opposes missile attacks on satellites: in a sense, it is futile to fight.

"It can be said that whether the missile hits the satellite will not make the result better or worse," Jonathan mcdowell told reporters humorously. "It only cost American taxpayers a little money."