Reading 7: SMART Technology: Moon Mission to Test Solar Engine with No Limits

READING PASSAGE 7

You should spend about 20 minutes on Questions 1 – 11 which are based on Reading 7.

SMART Technology: Moon Mission to Test Solar Engine with No Limits

Electric power and ion propulsion are about to combine for only the second time to propel a spacecraft beyond Earth orbit. Next April the European Space Agency's SMART-1 lunar satellite will head off to explore the Moon from an orbital position.

Electric propulsion has been used in low-Earth telecommunications satellites for years, and a high-tech ion engine powered NASA's Deep Space 1 test craft from 1998 until late last year. But before this technology is ready for prime-time missions to other planets and beyond, more tests are needed.

While SMART-1 is slated to perform science experiments at the Moon, its main mission is to test this technology. The engine being built for SMART-1 was originally designed by the Soviet space program in the 1970s. It does not burn fuel like chemical rockets; instead solar panels convert sunlight into electricity, which powers the atomic-scale propulsion system.

Most spacecrafts use rockets for propulsion, but the rocket fuel hydrazine is enormously heavy. Burdensome fuel tanks limit payloads, from how many scientific instruments can be carried to the number of astronauts. It's virtually impossible to embark on any voyage beyond the Moon without the help of gravity assist -- looping around a planet for a slingshot effect -- which limits launch windows and creates long, meandering trajectories.

Electric propulsion avoids these problems.

"To get rid of gravity assist, a more efficient propulsion system is needed, so that a craft can fly directly to Saturn for example, and not have to spend the time it takes go from Earth and then to Venus and then back again, before it finally travels out to Saturn," said John Brophy, a propulsion engineer at the Jet Propulsion Laboratory. The limits so far will be less than those imposed by chemical rockets.

Electric-ion propulsion is more efficient because its energy source (the solar panels) and the propulsion chemical (xenon) are separate. This way, the xenon atoms are used at an atomic scale, not on a massive scale like rocket fuel, which is both the fuel and energy source.

The atomic scale of the mechanism means the thrust on SMART-1 will be very small, equivalent to the pressure a sheet of paper applies to the palm of your hand. But because the xenon will be energized so much more efficiently than in a rocket, the ion engine will run much longer.

Over time the momentum of the craft will increase, eventually gaining speeds faster than a rocket would be able to produce.

Imagine SMART-1 is a car that uses 10 times less gas. The car may also go very slow when it starts, but it gains a certain velocity every hour that it runs.

The ability to run continuously, all the while gaining velocity, will aid energetically demanding missions such as the upcoming ESA trip to Mercury. This journey will demand more energy output than a trip to Mars or Venus.

An electric propulsion spacecraft would take two-and-a-half years to reach Mercury, beating a conventional spacecraft by a year and four months. The extra weight of the rocket fuel would require gravity assists from both Earth and Venus. "There is no limit to where this technology may take us," said Denis Estublier, the propulsion engineer for the mission.

The low thrust of electric propulsion has another advantage: maneuverability. The tiny push of the thruster, pointed in different directions, will make for more precise orientation of the craft.

NASA's Deep Space 1 mission tested the maneuvering capability of its thruster after an onboard star-tracking device broke down last year. The thruster's soft touch was able to control pitch and roll with more stability than the original steering mechanisms. Brophy said the images taken at that time were less shaky because of it.

Questions 1 – 5

Using no more than three words, answer the following questions. Write your answers in boxes 1 – 5 on your answer sheet.

1. According to the passage, in what area has the electric propulsion has been used for a number of years?

2. Apart from exploring the Moon, what is the main mission of Smart-1?

3. In the space technology at the present time, what do most of spacecrafts use for propulsion?

4. As a new type of space technology, what are the two advantages of electric-ion propulsion?

5. With the new technology, what will the pictures taken from spacecraft be like?

Questions 6 – 11

Complete the summary below. Choose your answers from the box and write them in boxes 6 – 11 on your answer sheet.

NB There are more words than spaces so you will not use them all. You cannot use any of the words more than once.

List of words

burdensome        a number of         technology       mature

tests                      burning                complete            turn

1.3                         run                         carry                   spacecrafts

2.5

Smart Technology

Electric power and ion propulsion are about to combine for only the second time to propel a spacecraft beyond Earth orbit. This technology has been used in low-Earth telecommunications satellites for many years. However, before it is … 6 … for prime-time missions to other planets and beyond, numerous … 7 … need to be done. With the new technology, the engine will … 8 …solar energy into electric power instead of … 9 … fuel like chemical rockets. By removing the … 10 … fuel tanks which limit payloads, the new engine will be able to … 11 … more scientific instruments and astronauts. A spacecraft with the Smart technology will travel about … 12 … years to reach Mercury.