NASA calls off space launch

     NASA called off the space shuttle launch because of a heater failure. "Commander Mark Kelly and his crew were on their way to the launch pad, when NASA halted the countdown. The astronauts' van did a U-turn and returned the astronauts to crew quarters"(http://www.npr.org/). Another try for the launch will be Sunday very early. Engineers did not know what the problem was so the launch was halted. Mark Kelly is married to wounded congresswomen Gabrielle Giffords.