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SMART-1: The First Spacecraft Of The Future



 
 
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Old September 22nd 03, 04:47 PM
Ron Baalke
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Default SMART-1: The First Spacecraft Of The Future

Paris, 22 September 2003
European Space Agency Information Note
N° 16-2003

SMART-1: the first spacecraft of the future

A very efficient engine, plenty of room for instruments, accurate
performance, good price. All these features characterise ESA's SMART-1,
due for launch during the night of 27-28 September. SMART-1 is much
smaller, cheaper and, in many ways, 'more powerful' than conventional
spacecraft. Its secret lies in several new technologies being tested on
board, which will be essential for spacecraft of the future. But this
space adventure is not only for engineers; scientists too are eagerly
awaiting SMART-1 - the first European mission to the Moon.

This is the first of a series of missions designed to test key
technologies for future spacecraft - SMART stands for 'Small Missions for
Advanced Research and Technology'. In the case of SMART-1, the two main
new technologies to be tested are a new 'solar-electric propulsion' system
and miniaturised spacecraft and instrumentation. Together, these
technologies make up a spacecraft with revolutionary qualities: smaller,
lighter, capable of carrying more scientific instruments, greater fuel
efficiency. All of which also considerably reduces the cost of the
mission.

So, the idea behind SMART-1 is to pioneer a futuristic philosophy, the
motto of which could be: 'more science for less money'. Even though it is
the first of a kind, SMART-1 has been developed in less than four years,
and at about a fifth of the cost of a major science mission for ESA: only
110 million euros. That includes the launch, the operations and a dozen
scientific experiments. This was achieved partly by using new management
methods - such as working with smaller teams both within ESA and in the
industry - and partly because of some of the new features inherent in
SMART-1, such as the miniaturisation and novel design.

Giuseppe Racca, SMART-1 Project Manager, explains: "What has been our
trick? First, a short development period in itself means less money. But
also, with its small size - which was a requirement of the mission because
we are testing miniaturised hardware - the spacecraft is able to 'share' a
commercial Ariane flight with two other passengers. Besides, since we were
not constrained by any existing design or heritage, we could be more
innovative and elegant in our architecture. For example, the new SMART-1
electrical architecture has enabled us to simplify the system tests
considerably."

SMART-1 could almost be a toy spacecraft - it weighs only 367 kilograms
and fits into a cube just one metre across (the solar panel wings extend
about 14 metres) - although one able to gather high-value scientific and
technological data.

Another innovation lies in the industrial policy applied to this mission.
SMART-1 is a good example of an ESA mission in which a comparatively small
company such as the Swedish Space Corporation (SSC) has been selected as
prime contractor. "The experience of SSC in highly successful projects at
national level was a key factor in the decision, as was ESA's goal of
fostering a balanced industrial landscape in Europe," says Niels Jensen of
ESA's Directorate of Industrial Matters and Technology Programmes.

The magic of ion engines

Solar-electric propulsion, one of the main technologies to be tested by
SMART-1, is a new technique that uses 'ion engines'. These work by
expelling a continuous beam of charged particles --ions-- at the back of
the engine, which produces a thrust in the opposite direction and
therefore pushes the spacecraft forward. The energy to feed the engine
comes from the solar panels, hence the name 'solar-electric propulsion'.

Engineers have been working on ion engines for decades, but only recently
have obstacles such as the lack of power availability from a spacecraft's
solar panels been overcome. Recent missions have been using ion thrusters
mainly for attitude control and orbit station keeping. In the recent case
of ESA's telecommunication satellite Artemis, the onboard availability
of ion thrusters was actually what allowed the mission to be rescued.
Having been left by the launcher on an unplanned orbit, Artemis was slowly
- but safely - brought up to its final working orbit by the power of its
ion engines, initially designed for orbit maintenance only.

Starting with SMART-1, the first European spacecraft to use an ion engine
as its main propulsion system, the amazing advantages of this method can
now be fully exploited. Ion engines are very efficient: they deliver about
ten times as much impulse per kilogram of propellant used. This gives a
substantial reduction in the mass of the fuel carried on the spacecraft,
which in turn leaves more room - more weight - for scientific
instrumentation. Also, ion engines allow scope for designing trajectories
to travel very long distances in less time, thereby opening the door to
deeper space exploration. Another advantage is that these engines make for
very accurate spacecraft control, which is essential for missions that
require highly precise target pointing.

Such qualities stem from the fact that ion engines generate a very gentle
thrust. SMART-1 will be accelerated just 0.2 millimetres per second per
second, with a push equivalent to the weight of a postcard. This is why
solar-electric propulsion cannot be used for taking off from Earth, for
example; it only works in the vacuum of space. For very distant
destinations, this is not a problem. Compared to conventional chemical
rockets, which burn for a few minutes, ion engines work for years, or for
as long as the solar panels keep providing electricity. So the ion
"tortoise" will eventually overtake the chemical "hare".

Long, energy-demanding interplanetary missions will benefit most from
solar-electric primary propulsion. In such cases, spacecraft need an
enormous amount of chemical fuel on board, leaving very little capacity
for scientific instruments. Moreover, to make the most economical use of
this fuel, they need to take maximum advantage of gravity-assist
manoeuvres, making space journeys longer and more complex. With
solar-electric propulsion, in contrast, much less fuel is needed on board,
with the advantages of more room for instruments and the ability to avoid
complex gravity-assist manoeuvres. But these advantages do not come into
play on short distances, such as from the Earth to the Moon.

So why is SMART-1 testing its ion engine on a trip to the Moon? The answer
is threefold. First, the Moon is a very interesting scientific target.
Secondly, SMART-1 has the opportunity to share the cost of an Ariane-5
launch with other passengers heading for the geostationary transfer orbit
(GTO), from which the Moon can be reached. Last but not least, the spiral
orbit which SMART-1 has to take to reach the Moon from GTO is a long and
complex trajectory, so that the ion engine will be fully tested in
conditions representative of a deep-space mission.

Good news for the whole space sector

The technology to be tested on SMART-1 is a strategic investment for ESA.
In particular, development of the solar-electric propulsion technology was
followed by ESA directly. The experience gained with SMART-1 will be
useful to many aspects of space technology, providing thorough groundwork
for future ESA programmes.

As ESA engineer Denis Estublier explains, "SMART-1 will provide answers to
technological questions that affect the whole sector. It will demonstrate
the use and the lifetime in space of electric thrusters; the ground
control of a quasi-continuously thrusting satellite, the performance of
the solar panels in the radiation belts; the interactions of the ion beam
with the spacecraft surface and instruments."

Many kinds of spacecraft, including commercial telecommunication
satellites, will benefit from such technology. Ion engines will find an
immediate application in future ESA scientific missions to distant
destinations that could not be reached otherwise, as conventional
chemical-propulsion spacecraft could not carry the required payload mass.
Other scientific missions will have to rely completely on the accurate
spacecraft control provided by the very gentle thrust of the ion engines.

SMART-1's journey starts on Saturday 27 September at 08.02 p.m. local time
in Kourou (Sunday 28 September at 01:02 a.m. CEST) with a launch an Ariane
5 rocket from the European launch base in Kourou, French Guiana. The trip
itself will be part of the adventure, with the engineers checking on the
performance of the new technology. But for the scientifically curious the
real thrill will begin in December 2004, when SMART-1 reaches the Moon.
Then it will be the turn of the scientific instruments, which will help to
solve such questions as the origin of the Moon, the existence of water on
the Moon, and the possibility of building a permanent human base on the
lunar surface.

Note to editors
SMART-1 was developed for ESA by the Swedish Space Corporation, as prime
contractor, with contributions from almost 30 contractors from 11 European
countries and the United States. The spacecraft carries 19 kilograms of
science payload consisting of experiments led by Principal Investigators
from Finland, Germany, Italy, Switzerland and the United Kingdom.

For more information, please contact:

ESA Communication Department
Media Relations Office, Paris, France
Tel: +33 (0)15369 7155
Fax: +33 (0)15369 7690

Giuseppe Racca, ESA SMART-1 Project Manager, Science Programme Directorate
Tel: +31 71 565 4618
E-mail:

Bernard Foing, ESA SMART-1 Project Scientist, Science Programme
Directorate
Tel: + 31 71 565 5647
E-mail:


Niels Jensen, ESA Directorate of Industrial Matters & Technology
Programmes
Tel: +31 71 565 3932
E-mail:


A dedicated SMART-1 launch page is available at:
http://www.esa.int/smart1
For more information about the ESA science programme, visit:
http://www.esa.int/science
For more information about ESA, visit: http://www.esa.int


 




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