Nasa has until 29 October to launch the Ares I-X
The US space agency will make another attempt to launch a prototype rocket designed to replace the ageing shuttle.
Tuesday's launch of the Ares I-X had to be scrubbed due to bad weather, and the forecast for Wednesday is no better.
There is just a 40% chance of acceptable weather for today's launch attempt, according to Nasa.
The slender, 100m-tall Ares I-X vehicle will test technology crucial for the development of a manned craft that could return astronauts to the Moon.
A combination of high wind speeds and clouds contributed to Nasa's decision to postpone the launch from Kennedy Space Centre in Florida on Tuesday.
Overnight, the site was lashed by rain; Nasa has been testing the launcher to ensure no issues arise as a result of lightning strikes in the area. The closest of these was 640m away.
The experimental craft has a four-hour launch window between 1200 and 1600 GMT (0800 and 1200 EDT) on 28 and 29 October.
Deputy mission manager John Cowart said: "Things are pretty dynamic weather-wise. We are currently "red" (no-go for launch). But only due to weather as it stands now."
Officials think their best chance of flying the rocket may come after 1430 GMT (1030 EDT) on Wednesday.
The craft is the first new launch vehicle that Nasa has designed and built in more than three decades.
Prior to the scheduled take-off on Tuesday, a fabric cover designed to protect a probe on the nose of the craft whilst it was on the launch pad became tangled. It was finally released to a round of applause by the mission team.
A ship that had sailed into the seas surrounding the launch site caused further delays.
Finally, bad weather forced controllers to scrub the event. Winds at ground level were blowing above 20 knots, higher than allowed for launch, and clouds obscured the pad.
The flight team was particularly concerned about the cloud coverage, partly because they needed clear skies to watch the flight but also because of a problem known as "triboelectrification".
This phenomenon occurs when the rocket encounters water or ice droplets in the clouds. As these collide with the rocket they cause a static charge to build up on its skin, creating interference with radio signals.
This is a problem for the 1-X team, which needs clear signals to gather data from 700 sensors wired throughout the vehicle, which are designed to collect flight data.
In addition, the team needed to be able to send a signal to a detonator and explosives onboard the craft, which would be used to destroy it in case of an emergency.
The slim-line rocket is a prototype of the Ares I craft, part of the Constellation programme intended to return the US to the Moon by 2020.
However, a recent report has cast doubt on the future of the programme.
The Augustine panel, which had been asked to review the US human spaceflight programme, published its report on 22 October.
Although the panel supported the Ares I-X test flight, it questioned the need to develop the Ares I.
In particular, the panel queried the cost and design of the craft as well as its development time.