NASA has a backup plan to launch crew and cargo to the moon, reduce the gap between shuttle retirement and a replacement ship's debut, and save taxpayers billions of dollars.
They call it the side-mount shuttle. It's basically the space shuttle system without the winged orbiters.
Preliminary NASA studies show that using the existing shuttle's solid rocket boosters, fuel tank and main engines as a launch system, with some minor modifications, could be the foundation of an alternative to the planned Ares rocket program currently under development.
NASA plans to retire the shuttle fleet after the international space station construction is finished, currently targeted for September 2010. Engineers have been working on a new system that not only could transport astronauts to the station, which orbits about 225 miles (360 kilometers) above Earth, but also travel in deep space for visits to the moon and other destinations.
Ares remains on track for a 2015 debut flight to the space station, at a cost of about $35 billion, program manager Jeff Hanley explained last week before a presidential panel reviewing the country's human space program.
For somewhere in the neighborhood of about $6.6 billion, NASA can develop a rocket for the moon.
Shuttle program manager John Shannon, who presented an overview of the side-mount shuttle launch vehicle to the same committee, cautioned that the cost is very preliminary, though it is the same figure derived by a NASA-commissioned team that studied a similar vehicle design three years ago.
Shannon says the shuttle-based heavy lifter is not as capable as Ares V, the rocket currently earmarked for a revived lunar exploration initiative that is intended to land astronauts on the moon by 2020. The side-mount shuttle's lunar lander would have to shrink from the planned 48 metric tons to about 28 metric tons.
"That's still pretty good because the Apollo lunar lander was 16 metric tons," shuttle program manager John Shannon said in an interview with Discovery News.
The side-mount shuttle system would be able to launch astronauts to the station or the moon inside Orion capsules, which also are being developed under NASA's Constellation program.
The capsules would sit inside a protective shroud that could fly the spacecraft away from the rocket in case of an accident. NASA used a similar escape system on its Apollo capsules and is developing one for Orion. Russian and Chinese crewed spaceships also have launch escape systems.
The side-mount shuttle would be simplified to cut costs and increase its lift capability. The shuttle's three hydrogen-fueled main engines, for example, would be not be reused, as they are today. The engines, along with the external tank and solid rocket motors, would be dropped into the ocean during the climb to orbit. Under the current configuration, the shuttle's main engines are attached to the tails of the orbiters, which make piloted runway landings.
"Reusability is a myth, in my opinion," Shannon said, citing the cost of maintaining manufacturing capability, production of single replacement parts and the need for post-flight inspection and engineering assessments.
A few new pieces of equipment would be needed to transition the shuttle into a new launch vehicle, including development of a payload fairing to protect cargo during launch, and a structure to bolt the main engines on to the fuel tank. It would use the same four-part solid-fuel booster rockets used today, with an upgraded five-segment system envisioned for future heavier-lift vehicles.
Among the key advantages of the side-mount shuttle is that the flight software, launch facilities, manufacturing capability and 30 years of test flight history are already in hand.
"The benefits are obvious. We basically have the parts to build everything," Shannon said.
The alternative NASA rocket could be ready for testing in about four and a half years at an estimated cost of about $2.6 billion.
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