NASA fueled space shuttle Discovery for an early morning flight to the international space station on Tuesday as a TV comedian whose treadmill is on board gave a "go" for launch and urged, "Let's light this candle!"

Thunderstorms remained over the launch site late Monday, however, and forecasters lowered the odds of acceptable conditions to a grim 40 percent.

Discovery and seven astronauts were set to blast off at 1:36 a.m. with a full load of supplies, experiments and equipment. They headed out to the launch pad Monday night, waving and smiling, and climbed into the shuttle one by one. The weather worsened as the night wore on, and a lightning strike was reported six miles from the pad.

Discovery's most prominent payload is NASA's new $5 million treadmill, which is named after Comedy Central's Stephen Colbert. He could not attend the launch, but said in a recorded message that he couldn't be prouder that his treadmill soon will be installed at the space station "to help finally slim down all those chubby astronauts."

"Let's face it, being weightless is mostly just a desperate bid to get away from that bathroom scale every morning," Colbert said. "But you guys and gals are ambassadors to the universe. Don't make us look bad. Put down the astronaut ice cream, tubby. Tubby, tubby, two-by-four, couldn't fit through the air lock door."

Colbert campaigned earlier this year to have a space station room named after him. He won the online vote, but NASA went with Tranquility, the name of the dry lunar sea in which Neil Armstrong and Buzz Aldrin landed 40 years ago this summer. As a consolation prize, Colbert got the treadmill. It's full name is Combined Operational Load Bearing External Resistance Treadmill; it will fly up in more than 100 pieces and won't be put together until sometime next month.

Colbert poked fun at NASA's choice of Tranquility for the chamber, which will be launched early next year. "Yeah, that will scare the aliens," he said. He ended his televised message by shouting, "I am 'go' to launch me. Let's light this candle!"

In all, the space shuttle will deliver about 17,000 pounds of gear to the space station. The experiments include six mice that will remain at the orbiting outpost until the following shuttle visit in November. Part of a bone loss study, the mice will be the first mammal creatures — other than humans — to spend a prolonged period at the space station.

Three spacewalks will be performed during the 13-day shuttle flight, to install a new ammonia tank, part of the space station's cooling system, and replace other equipment and retrieve outdoor experiments. And the station will get a new resident, Nicole Stott. She will replace an astronaut who moved in during the last shuttle flight last month. That spaceman will return to Earth aboard Discovery, as will Buzz Lightyear. The action figure toy has been in orbit for more than a year.