Balky radar

Having just dealt with a shorted abort switch. Apollo 14 ran into more technical problems when they reached a point where they expected the landing radar to begin feeding data to the computer. Typically, crews expected the all-important radar to be working by 10,000 metres altitude, but as Aniares passed this point, the computer was still receiving no radar data from the antenna.

“Come on radar,’’ implored Ld Mitchell, the LMP, but the two lights on the DSKY stayed stubbornly illuminated. “Come on radar!”

A minute passed and Fred Haise in Houston informed them of when they could expect P63 to begin throttling the engine. "Okay, 6 plus 40 is throttle down, Aniares.”

“Roger. Houston,’’ said Mitchell. “We still have altitude and velocity lights.’’

By 7.000 metres, there was still no valid data coming from the landing radar and the two crewmen frantically tried to make it work, knowing that if they still had no success by 3.000 metres, they were bound to abort the mission, separate the ascent stage, and return to the CSM.

“Antares, Houston,” said Haise. “We’d like you to cycle the landing radar breaker.”

Mitchell pulled one of the little aviation-type circuit breakers to remove power from the radar, then pushed it in again. Quite often in electronics, a power-down, power-up cycle is all that is required to clear an abnormal operating condition and the earlier manual patch to the computer to deal with the abort switch short had created such a state. “Okay.” said Shepard. “Been cycled.”

“Come on in!” Mitchell urged, then. ’’Okay!” as the lights went out and the radar began to function normally at only 5,500 metres. “How’s it look, Houston?” called Shepard.

Shepard, at 47, was the oldest of the Moon-bound crews and the only Mercury astronaut to go to the Moon. Many have wondered whether he would have attempted a landing without the radar. Most believe that if he had tried, the narrow’ margins of propellant w ould have obliged him to abort further down.

In contrast to Apollo 14‘s late acquisition of radar data, Young and Duke got a pleasant surprise when Orton s landing radar began to deliver data much earlier than expected on Apollo 16. Compared to the other landing flights, Orion’s descent began at a much higher altitude over 20.000 metres, probably due to some over­compensation made for the influence of the mascons on Apollo 1 5. They were then surprised when their landing radar started to work while they were still 15,000 metres or 50,000 feet up. w’hich was 50 per cent higher than expected.

“Look at that!” exclaimed Young. “Altitude and velocity lights are out at 50k!“

“Isn’t that amazing," agreed Duke.

“Look at that data, Houston,” said Young. "When do you want to accept it?”

“Okay, you have a Go to accept.” said Jim Irwin once the flight controllers had passed on their agreement.

”Okay,” replied Duke. "It’s in.”