According to NASA
, "The Space Shuttle Discovery and its seven-member crew are set to launch from NASA's Kennedy Space Center at 3:49 p.m. EDT on Saturday, July 1. Commander Steve Lindsey and his crew will continue evaluating new shuttle safety improvements during the 12-day mission. They'll also carry supplies and a third crew member to the International Space Station. At least two spacewalks are planned."
There are two main objectives for the STS-121 mission, Return To Flight and International Space Station assembly. Return To Flight
Since the Columbia space shuttle tragedy, safety and inspection is a priority. The Columbia Accident Investigation
determined that a piece of insulating foam came off the huge orange fuel tank on its launch and struck the leading edge of the wing on the shuttle. This caused damage to that section of the black heat shielding tile system that protects the space craft from the immense heat generated during shuttle's re-entry through the atmosphere. That damage caused the tragic disintegration of Columbia during re-entry, destroying the shuttle and killing all of its STS-107 crew members
The last space shuttle mission, STS-114, was a great success, but some insulating foam debris was also detected coming off the external fuel tank during the launch phase. That fuel tank has since been redesigned to correct known probable causes for debris. In addition, this launch will be filmed by a large number of additional cameras set up to detect any tank debris during launch. Cameras located on the Discovery shuttle, on the launch pad, on the ground, and even in chase aircraft will film the launch of STS-121.
When the external fuel tank seperates from Discovery, cameras will film it as it falls away to capture additional images for inspection and analysis to determine if foam has come off of it. Also, before Discovery docks with the International Space Station, the shuttle will perform a rollover maneuver so cameras located on the ISS can film the heat shielding tiles to inspect the integrity of them.
During the 12-day mission, the crew will also perform some testing and evaluation of possible repair measures that could be taken, if needed. One of the Extra-Vehicular Activities (spacewalks) NASA has planned will test the viability of using the long loading arm as a platform for performing repairs on the shuttle. Not officially scheduled, another EVA will entail testing the performance of a patching substance, called novax, on a set of sample damaged tiles, if time permits.
The EVA that will test the arm should be fairly interesting. Imagine for a moment that you fixed a certain weight on the end of your car's radio antenna or at the end of a fishing rod. The Discovery crew will be testing whether or not the slow motion deflection of the loading arm with the weight of a man would prohibit him from doing repairs. In other words, would the swaying or bouncing of the arm itself -- estimated to be as much as four feet in simulation -- prohibit a man from doing repairs that require fine motor skills. If so, the crew will test a repair platform position that only utilizes a position halfway on the arm to limit the instability. International Space Station assembly
As important as the Return To Flight objectives are, 2/3rds to 3/4ths of the actual mission goals for STS-121 will be International Space Station assembly and will take up much of the Discovery's crew time in space. The big picture dictates that the NASA shuttle program fulfill its obligations to its international partners in building the ISS before the program is mothballed in 2010.
Equipment and supplies will be transferred from the shuttle to the station. Three new EVA suits will be tested and left on the ISS. Repair and replacement of equipment will take place inside the ISS, and outside, involving the second planned EVA mission.
The second EVA will repair one umbilical system that accidently cut its cable earlier this year with the installation of a new part to prevent accidental damage, and also totally replace another one. From all accounts, the total replacement portion of that EVA will be tricky. One crew member will be on the arm while another "translates" himself around the outside of ISS and Discovery. The piece of replacement equipment to be manhandled from Discovery to the ISS -- and conversely -- the old one to be taken from the ISS back to Discovery, is described as weighing about 350lb (160kg) and as cumbersome and bulky as moving a refrigerator. Don't you hate when your friends ask you to help them move?
Equipment and supplies are often delivered by our Russian partners in unmanned delivery vehicles, launched from Baikonur Cosmodrome, Kazakhstan. The Progress 22 cargo spacecraft
just docked at the ISS at 11:25 EDT on Monday in anticipation of STS-121. Progress 22 is destined to be a semi-permanent ISS closet rather than a delivery craft that is subsequently filled with trash and discarded by detaching it and letting it burn up in the atmosphere. The Russian Soyuz style craft can also be used as "lifeboats" should the need arise.
Discovery, on the other hand, will leave one of its crew members, European Space Agency astronaut Thomas Reiter, to complement the current ISS crew of Commander Pavel Vinogradov and Flight Engineer Jeff Williams.
The STS-121 crew includes Commander Steven Lindsey, Pilot Mark Kelly and Mission Specialists Michael Fossum, Lisa Nowak, Stephanie Wilson, Piers Sellers and Thomas Reiter, an astronaut with the European Space Agency.
While I know I'll run outside my house and try to see the launch
with my own eyes this upcoming Saturday, I'll be watching the rest of the mission on NASA TV
. May everyone complete their mission and return safely back to us, here on Earth.