New main engine promises even safer shuttle ride
Posted: April 27, 2001

The next space shuttle crew can expect an even safer ride into orbit, thanks to the completion of a new Space Shuttle Main Engine. Workers installed one of the new engines, called the Block 2 configuration, on Space Shuttle Atlantis, April 24, at NASA's Kennedy Space Center, Florida.

Engine shop
The upgraded Block 2 engine sits in the Space Shuttle Main Engine Processing Facility at Kennedy Space Center awaiting transfer to Atlantis' hangar. Photo: NASA-KSC
Atlantis' first flight using the new engine is targeted for no earlier than June 14 on mission STS-104 to the International Space Station. Atlantis will use one Block 2 main engine and two Block 2A main engines to complete its full complement of three engines.

Improvements to the main engines, managed by NASA's Marshall Space Flight Center, Huntsville, AL, continue to evolve to produce the safest, most reliable and reusable space transportation system in the world.

The Block 2 Main Engine configuration includes a new Pratt & Whitney high-pressure fuel turbopump.

The primary modification to the engine is elimination of welds by using a casting process for the housing, and an integral shaft/disk with thin-wall blades and ceramic bearings. This makes the pump stronger and should increase the number of flights between major overhauls. Although the new pump adds 300 pounds (135 kilograms) of weight to the shuttle, the results are a more reliable and safer engine because of increased pump robustness.

"With this design change, we believe we have more than doubled the reliability of the engine," said George Hopson, manager of the Space Shuttle Main Engine Project at Marshall.

Previous improvements to the Space Shuttle Main Engine include the Block 1 configuration, which featured an improved high- pressure liquid oxygen turbopump, two-duct engine power head and single-coil heat exchanger. The turbopump incorporated ball bearings of silicon nitride -- a ceramic material 30 percent harder and 40 percent lighter than steel. The Block 1 engine first flew in 1995.

A special transport vehicle carrying the new Block 2 engine arrives at Orbiter Processing Facility bay 3. There the new engine will be installed on Atlantis for its launch in June. Photo: NASA-KSC
The Block 2A engine added a larger-throat main-combustion chamber to Block 1 improvements. The new chamber lowered the engine's operating pressures and temperatures while increasing the engine's operational safety margin. This engine first flew in 1998.

Developed in the 1970s by Marshall, the Space Shuttle Main Engine is the world's most sophisticated reusable rocket engine. Each powerful main engine is 14 feet long, weighs about 7,000 pounds and is 7.5 feet in diameter at the end of the nozzle.

The engines operate for about eight-and-one-half minutes during liftoff and ascent and shut down just before the shuttle reaches low-Earth orbit.

The engines perform at greater temperature extremes than any mechanical system in common use today. At minus 423 degrees Fahrenheit (minus 217 degrees Celsius), the liquid hydrogen fuel is the second coldest liquid on Earth. When it and the liquid oxygen are combusted, the temperature in the main combustion chamber of the engine is 6,000 degrees Fahrenheit (3,316 degrees Celsius), hotter than the boiling point of iron.

Boeing Rocketdyne, Canoga Park, CA, manufactures the Space Shuttle Main Engine.

As the giant forklift moves closer to Atlantis, workers keep watch as the new Block 2 engine nears the shuttle's rear. Photo: NASA-KSC

Hubble poster
The Hubble Space Telescope's majestic view of the Eskimo Nebula. This spectacular poster is available now from the Astronomy Now Store.