STS-41

Flight Crew

RICHARDS, Richard Noel, 44, USN, commander, 2nd mission Previous mission: STS-28 (1989)

CABANA, Robert Donald, 41, USMC, pilot MELNICK, Bruce Edward, 40, USCG, mission specialist 1 SHEPHERD, William McMichael, 41, USN, mission specialist 2, 2nd mission Previous mission: STS-27 (1988)

AKERS, Thomas Dale, 39, USAF, mission specialist 3

Flight Log

Originally intended to be deployed from Challenger by the liquid-fuelled Centaur upper stage during the STS 61-F mission in May 1986, the joint NASA/ESA Ulysses solar polar probe mission was delayed by the loss of Challenger in the STS 51-L accident of January 1986. The decision not to fly Centaur stages on the Shuttle over safety concerns and to use the IUS/PAM upper stages instead meant that Ulysses would miss the 1986 launch window. It soon became clear that the Shuttle would not be ready for the June 1987 window and, to ease the 1989 launch schedule, NASA rescheduled the mission to October 1990. Difficulties with the leaking propulsion systems on Atlantis and Columbia during the summer of 1990 placed added pressure to launch STS-41 on time but, despite three short delays due to ground equipment and the weather problems, STS-41 finally left the ground just 12 minutes into the 2.5 hour window.

The crew successfully deployed the IUS combination carrying Ulysses just 6 hours 1 minute 42 seconds after leaving the launch pad. Following the deployment of their primary payload, the crew of STS-41 concentrated on the variety of mid-deck and

payload bay experiments for the remainder of their short mission. Though the flight of STS-41 lasted only just over 4 days and is one of the shortest missions in the programme, the primary payload mission has lasted much longer. After more than 16 years in space, the Ulysses probe continues to function, transmitting important solar and interplanetary data back to Earth. To a degree, therefore, the “mission” of STS-41 continues.

Just over an hour after the deployment, the first stage of the IUS burned for 110 seconds, boosting the spacecraft from 29,237 kph to 36,283 kph. The second stage burned for 106 seconds, further increasing the speed to 41,158 kph, before the PAM-S fired for 88 seconds, resulting in a speed of 54,915 kph. Ten minutes later, the space­craft was separated from the upper stage to begin its long flight towards the Sun via Jupiter. The probe made its 375 km closest approach to Jupiter on 8 February 1992. Its first southern polar zone pass between 26 June and 6 November reached 80°S (13 September). Its first northern polar pass occurred between 19 June and 30 Sep­tember 1995 and saw the official completion of its primary mission. Its closest approach at 1.34AU occurred on 12 March 1995. It took almost five years from launch to the second polar pass, though it took only 8 hours to journey the 382,942 km from Earth to the orbit of the Moon, a trip that took Apollo astronauts three days to complete. Ulysses completed its second pass of both poles in 2001. Its third southern polar pass is planned for 2006/2007 and its third northern polar pass for 2007/2008.

Milestones

135th manned space flight 66th US manned space flight 36th Shuttle flight 11th Discovery flight

3rd Shuttle solar system deployment mission 1st three stage IUS deployment mission 1st solar polar probe

1st US Coast Guard officer (Melnick) to fly in space