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Today the US Celebrates 47 Years of Manned Space Flight

05/05/2008 03:47PM

Today the US Celebrates 47 Years of Manned Space Flight
Forty-seven years ago today, May 5, 1961 9:34am EST to be exact, astronaut Alan Shepard became the first American in space. He launched aboard Mercury-Redstone 3 (MR-3), in his capsule named Freedom 7, to make an historic 15-minute suborbital flight.

The main scientific objective of project Mercury was to determine man's capabilities in a space environment and in those environments to which he will be subject upon going into and returning from space. A few of the basic flight problems included: The development of an automatic escape system, vehicle control during insertion, behavior of space systems, evaluation of pilots capabilities in space, in flight monitoring, retrofire and reentry maneuvers and landing and recovery.

The formal countdown for the preparation for launching MR-3 started on the day previous to launch day. The countdown was actually split into two parts because previous experience had shown that it was preferable to run the countdown in two shorter segments and allow the launch crew of both the spacecraft and the launch vehicle to obtain some rest before starting the final preparation. The countdown started at 8:30am EST on May 4, 1961. All operations proceeded normally and were completed ahead of schedule. A build-in hold of approximately 15 hours was called at T minus 6 hours 30 minutes. During this time the various pyrotechnics were installed in the spacecraft and the hydrogen peroxide system was serviced.

The countdown was resumed at T minus 6 hours 30 minutes at 11:30pm EST on May 4, 1961. A built-in hold of 1 hour had been previously agreed upon at T minus 2 hours 20 minutes. This hold was to assure that spacecraft preparations had been completed before the astronaut was transported to the pad. The countdown proceeded with only minor delays until T minus 2 hours 20 minutes. At this time, final preparation of the spacecraft was conducted and the astronaut was apprised of the continuance of the countdown and transported to the Pad. The countdown was continued after the hold at T minus 2 hours 20 minutes and, except for some minor holds, the countdown continued until T minus 15 minutes. At this time it was determined that photographic coverage of the launch and flight could not be obtained because of low clouds near the launch area. Weather forcasters predicted that visibility would improve rapidly within 20 to 45 min. During this time, one of the 400hz power inverters to the launch vehicle had regulation problems. The count was recycled to the T minus 35 minute and holding mark and the count picked up 86 minutes later after the replacement of the inverter.

Again at T minus 15 minutes it was necessary to hold the count again to make a final check of the real-time trajectory computer. The countdown then picked up and proceeded until liftoff at 9:34am EST on May 5, 1961.

In this historic 15 minute, 28 second flight, Alan Shepard reached an altitude of 116.5 statute miles and a velocity of 5,134 mph.

After the flight of Freedon 7, there remained no doubt that man could function intelligently aboard the Mercury spacecraft and with relative safety in a true space environment for 15 minutes.

What of the primitive spacecraft that he had inhabited? How well did it perform? The answer seemed to be very well indeed. But could its systems be trusted to work under even more demanding conditions in orbital flights? These were only a few of the questions that remained to be answered in subsequent Project Mercury flights.


For more information:

http://www.nasa.gov/externalflash/alan_shepard_gallery/index_noaccess.html

http://science.ksc.nasa.gov/history/mercury/mr-3/mr-3.html

http://www.hq.nasa.gov/office/pao/History/SP-4201/toc.htm

http://www.hq.nasa.gov/office/pao/History/SP-4201/ch11-4.htm


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