At 8:00 a.m.* EDT tomorrow, October 27, NASA will launch a test rocket called Ares I-X from Kennedy Space Center in Florida. The rocket is the first new launch vehicle to be tested in nearly four decades and the test will gather data critical to the design and development of Ares I–NASA’s new rocket designed to replace the aging space shuttles and take humans to the moon, and possibly to Mars and beyond as part of the Constellation program.

Last week it took engineers almost seven hours to roll Ares I-X to launch pad 39B where it completed its flight readiness review. Now NASA’s biggest concern for lift off is the weather. The agency has a four hour launch window, and while it only needs 10 minutes of clear skies for a “go”, the forecasters are calling for 60 percent chance of clouds. If the launch is scrubbed, engineers will try again on Wednesday.

The test flight comes at a trying time for NASA, after its plan for the future of human exploration underwent an independent review and the outcome did not favor the Ares I. Despite these findings, NASA officials support the test flight, saying the data gathered will be useful for the design of any future rocket.

“This is the first time in more than 30 years that NASA has built a vehicle in a new configuration so this has been a valuable learning experience,” said Doug Cooke, associate administrator for NASA Exploration Systems Mission Directorate in a press release.”This test will yield important data to support the nation’s next steps in exploration. There is no substitute for hard data–flight testing clarifies the distinction between imagined outcomes and real flight experience.”

Follow the launch on Twitter, and the Ares I-X blog, then return to Delta-V for a post-flight analysis.

*Update 8:49 a.m, 10/27.: The launch has been delayed, scheduled for 9:24 a.m.. A rain shower is expected to pass over the launch pad at 9:50 a.m., which could cause further delays if not launched as currrently scheduled.

*Update 9:39 a.m.: There is a cargo ship in the Atlantic Ocean “danger zone”, so launch is now scheduled for 9:49 a.m.

*Update 9:54 a.m.: NASA is now waiting for a break in the clouds for flight. The weather aircraft is making its flight and NASA will announce a new launch time in 5 minutes.

*Update 10:35 a.m.: New launch time is 10:54 a.m., but weather forecasters not so confident the skies will hold.

*Update 11:26 a.m.: Today’s launch attempt has been scrubbed due to weather. NASA will try again tomorrow, October 28, starting at 8:00 a.m. EDT.