Discovery before liftoff

This afternoon, at 16:39 Polish time, the shuttle Discovery is scheduled to take off from Kennedy Space Center in Florida. Fueling of the shuttle was completed early this morning – this time there were no fuel sensor problems that prevented the launch two weeks ago.

The shuttle launch date, originally set for May, then July 13, was postponed for safety reasons. After the shuttle Columbia disaster in 2003, experts tightened the launch clearance criteria. The glitch that prevented the last launch – a faulty fuel sensor that reported low levels despite a full tank – has been fixed, but the cause is not entirely clear.

Characteristics like. lightning!

Mechanics working on the service speculate that the problem may have arisen from faulty grounding. Scott Thurston, a member of the mechanical team, says that controlling voltage characteristics “is like predicting lightning – you know it’s going to strike, but you don’t know where.” Changes have been made that should solve the problem, assuming the diagnosis was correct. Technicians announce that if it turns out the source of the problem was different, the launch will be canceled.

Liberalization of procedures?

If the identical error is repeated, Discovery could launch with three working sensors, out of four installed. If that were to happen, it would mean a repeal of the restrictive launch procedures that require all four sensors to be operational. The prospect of such a precedent doesn’t please Rand Aver, who worked on the investigation after the Challenger shuttle explosion in 1986.

– What I want from NASA is for it to provide a factual basis for rescinding the safety measures. I don’t like the fact that all it takes is one failed startup for there to be discussions about liberalizing procedures,” Avera says.

Corrected hazard rate

The Challenger shuttle exploded shortly after takeoff. The accident resulted in an adjustment to the hazard index, which is calculated by NASA. The so-called probabilistic risk assessment is determined based on past experience with space shuttle flights, computer simulations, and expert estimates. After the 1986 disaster, NASA changed the ratio from 1:100,000 to 1:50. Because of later successful missions, the ratio was set at 1:254 in 1998.

However, this one time in 254 cases happened 5 years later – seven astronauts died in the Columbia shuttle disaster. This prompted NASA specialists to make more conservative estimates of launch safety – today it is estimated that the probability of mission failure is 1%.

See you in 12 days?

Discovery will deliver supplies and equipment to the ISS. Two members of its seven-member crew will make three weightless spacewalks, testing various methods of repairing damage to the spacecraft in case a Columbia-like failure occurs. The tragedy occurred because, upon entering Earth’s atmosphere, highly heated gas entered the shuttle’s interior through a hole punched at launch by the impact of a detached piece of insulation material.

If all factors, including weather, prove favorable, the first space shuttle flight in more than two years will begin. The mission, of great importance both scientifically and psychologically, is expected to last 12 days.

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