Aerospace Engineering: Deep Space 1

Deep Space 1

Dedicated to testing new technologies for deep space and interplanetary missions, NASA launched Deep Space 1 (DS1), NASA’s first spacecraft in the New Millennium Program. Deep Space 1’s purpose was to test the viability of the ion engine, autonomous navigation software, solar power concentration array, miniature camera, and 8 other technologies that had never previously been tested in space.

Deep Space 1 launched on October 24th 1998 from Pad 17-A at the Cape Canaveral air station at 12:08 UT ( 8:08 AM EDT). One of its initial missions was to fly by the asteroid 9969 Braille, which was selected as the mission’s target. The mission was extended twice to include capturing images of the comet Borrelly, and to further conduct engineering tests. Although there were small problems initially during early stages of flight, the encounter with the comet proved to present valuable results.

 

Mission Accomplishments

All of the technology systems on Deep Space 1 were successful. The mission proved the effectiveness of an ion engine for long-duration spaceflight and advanced the field of space craft navigation. Deep Space 1 also captured images of the asteroid Braille, and thus revealed interesting similarities between the asteroid Braille and the asteroid Vesta. Furthermore, Deep Space 1 validated valuable science especially during its flyby of comet Borrelly.

Initially, DS1 was intended to fly by the dormant comet Wilson-Harrington, but DS1’s star tracker failed before the mission on November 11th 1999. Instead, NASA mission planners devised a plan for DS1 to flyby Borrelly in September of 2001 without a star tracker.  DS1 was not only able to flyby the comet without a star tracker, but it captured never before seen images of the comet. In fact, because the Borrelly mission was so successful, it not only confirmed the use of tracking without a star tracker, but the use of an ion engine for deep space missions.

Deep Space 1 set the record for the longest operating time for a propulsion system in space. By August 17th 2000, the engine had been operating for 162 days as part of its 8 month test.  NASA disconnected contact with Deep Space 1 on December 2001, but the success of DS1 prompted the launch of Deep Space 2 in December of 2001.

  • NASA Deep Space 1 Mission Profile:  A brief summary explaining details about the Deep Space 1 mission including the space craft dimensions, mission costs and accomplishments.
  • Deep Space 1 Technology:  A deeper look at Deep Space 1 spacecraft and the technologies that were used to propel it.
  • The Borrelly Comet Mission:  A brief summary about the Deep Space 1’s successful encounter with the Borrelly comet, and successful capture of the first image of the comet’s core.

 

Technology: DS1’s Ion Engine and How It Works

Deep Space 1’s ion engine was not the first ion engine ever produced. NASA started developing them in the 1950s, but because the technology was expensive, it was deemed too risky to test during actual space flight.

A typical rocket engine produces thrust using Newton’s third law of motion – for every action, there is an equal and opposite reaction. A chemical rocket burns rocket fuel and shoots exhaust from the engine’s nozzle at roughly 7,000 miles per hour, thereby creating thrust. The weight of the exhaust combined with the speed generates thrust.

Ion engines, however, are a much more efficient engine because it shoots ions out of the engine’s nozzle at a much higher velocity or speed. This is the basic premise behind the ion engine. Instead of using combustion to accelerate atoms, an ion engine accelerates them electronically.

First, xenon atoms are ionized to give them an electrical charge. A pair of grids is charged over 1,000 watts to accelerate the xenon atoms to over 7,700 miles per hour. These xenon atoms are traveling 10 times faster than the atoms leaving a combustion engine, and therefore provide about 10 times the thrust compared to that of a chemical combustion engine.

 

Other Technologies

SCARLET concentrating solar array

To charge the grids that excite the ions, most ion engines use solar panels to provide electricity. The primary source of power on DS1 was produced by a new solar array technology called SCARLET, the Solar Concentrator Array with Refractive Linear Element Techonolgy. SCARLET uses linear fresnel lenses made of silicone to concentrate light onto solar cells.

The solar array panels on Deep Space 1 provided approximately 2400 watts, which is enough to accelerate about 100 grams of xenon per day. Of the 81.5 kg of xenon dedicated to DS1’s ion engine, DS1 only used approximately 17 kg during its primary mission.

Autonav

Deep Space 1’s Autonav system, developed by NASA’s Jet Propulsion Laboratory, works as a tracking and navigation device.  Autonav works by taking images of known bright asteroids, and then uses those images to mark a fixed point as if on a map. From there, Autonav is able to observe other moving asteroids in the Solar System with a noticeable predictable speed, and by comparing their locations, it can predict its own relative position. Two or more known asteroids’ locations are necessary in order for the spacecraft to triangulate its position.  In essence, Autonav is similar to a GPS system, but without the costs of an operator.

Before DS1, most spacecrafts were tracked by transmitters of the Deep Space Network (DSN), which requires skilled operators. Autonav, however reduces the mission costs and the demands on personnel.