Stardust Space Probe, USA

Stardust is a space mission by NASA that will fly close to a comet and, for the first time ever, bring cometary material back to Earth for analysis by scientists.

Stardust spacecraft was launched 6 February 1999 from Cape Canaveral, Florida, after delays, which were caused by warning alarms. The mission is the first by NASA, which is dedicated solely to a comet and the first robotic return of extra-terrestrial material from outside the orbit of the Moon. The main aim of the project is to cross the path of the Wild 2 comet and collect dust particles for analysis in space and to later return the particles to Earth for further investigation. The comet to be analysed is thought to carry materials which consist of ancient pre-solar interstellar grains and nebular condensates. These include remnants left over from the formation of the solar system and thus, are thought to hold information about the evolution of the sun and planets and possibly the origin of life itself. The project is one of NASA's discovery missions, which aim to cost less than $150 million.

PROJECT MAKE-UP

Lockheed Martin Astronautics designed and built the Stardust spacecraft. The Jet Propulsion Lab provided an experienced project management team, led by Kenneth L. Atkins, (an early leader in comet missions), and the optical navigation camera. The Max Planck Institute (MPI) of Germany provided the real-time dust composition analyser for the craft.

The probe used two Earth gravity assists to enter an orbit around the Sun. It will make three loops around the Sun crossing the trajectory of the comet on the second. The projected time of cross over has been forecast for 2 January 2004. At this point the probe will only be 62 miles from the comet. Following this the probe will return to Earth taking approximately two years to do so.

The probe cruises at 70,000mph. It was launched from the Earth in February 1999 and by March, the craft was nearly 6.5 million miles from the Earth, tracked continuously through the large antennas of NASA's global Deep Space Network. On 15 January 2006, the collected particles will be dropped off in a re-entry capsule that will parachute to Earth and land on the U.S. military's Utah Test and Training Range near Salt Lake City.

Stardust will deploy a sponge-like aerogel that will gradually absorb the particles of dust in order not to damage them. The gel was designed as a measure of catching the dust particles without vaporising them. These particles will be smaller than a grain of sand and will be travelling at a speed nine times faster than a bullet.

The Cometary and Interstellar Dust Analyzer, will analyze the dust as the probe travels through space, and then send the information back to Earth. Furthermore, the probe will also snap pictures of the comet as it passes its trajectory.

The craft was set inside a protective metal shell which was placed upon a Boeing Delta II 7426 launch vehicle. The vehicle consisted of three stages stacked on top of each other, plus 4 small solid-fuel rockets strapped to the outside of the first stage. Each rocket contained 11,765kg (25,937lbs) of hydroxyl-terminated polybutadiene (HTPB) propellant and provided an average thrust of 446,023N (100,270lbs) at sea level. Total weight of the spacecraft, including the sample return capsule and propellant carried onboard for trajectory adjustments, was 385kg (848lbs).

The three stages each have their own rocket motor, with the first two using liquid rocket fuel and the third using solid rocket fuel. The first stage is lift-off and insertion into a 189km (102-mile) parking orbit, which is a low orbit around the Earth. The second stage is a coast of about a half an hour until the vehicle position is properly aligned relative to the direction it must leave Earth. The final stage is the injection to an escape trajectory.

The four solid rocket strap-ons were discarded and fell into the ocean 66s after lift off, with the remaining strap-on boosters released 1s later. The craft was travelling at a velocity of 3,862km/h (2,390 miles per hour). The central first stage continued to burn for about 3mins powered by an RS-27A engine which used 96,160kg (212,000lbs) of RP-1 and liquid oxygen as its fuel and oxidizer. After 4.4mins stage one shut off and the craft was then travelling at 20,096km/h (12,439 miles per hour).

13.5s later an AJ10-118K engine was ignited and burned 5,900kg (13,000lbs) of Aerozine 50 (A-50). This propellant is a mixture of hydrazine and unsymmetrical dimethyl hydrazine (UDMH) and uses nitrogen tetroxide as the oxidizer. At this point, the shell covering of the craft known as the fairings was discarded. A 10min coast was then followed by a second burn.

The spacecraft is then 'spun up' before the stage three burn launches the craft out of Earth orbit and on trajectory with the Sun. This third and final stage uses a Thiokol Star 37 FM booster. The burn lasted 88s and used thrusters mounted on the arm of stage three to prevent spinning and maintain stability. Stardust then separated from stage three and used its own thrusters to stop spinning.