As space engineers and scientists met last month for a final review of the
Mars Express spacecraft design, the spacecraft itself was taking shape at
the premises of Alenia, Torino, Italy. “Normally, we would have the critical
design review (CDR) after tests of the spacecraft structural model (SM tests)
have been completed. But because of the tight schedule for Mars Express,
most of the review had to be completed early. We’ve done all the reviewing
we can. A few items have to wait until after the SM tests,” says Rudi
Schmidt, Mars Express Project Manager.

The CDR was a lengthy process involving all contributors to the Mars Express
spacecraft. After receiving reports from the various industrial teams, a
group of 63 engineers met at the offices of Astrium, Toulouse, the prime
contractor, for a “co-location” meeting lasting one week at which all
reports were scrutinised and awkward questions asked. The co-location
report then went before a final board meeting, attended by ESA’s Director
of Science, the Inspector General and other senior staff outside the Mars
Express project team, for final scrutiny. “The CDR went well. The final
board made some recommendations, but these were largely what we had
expected,” says Schmidt.

Meanwhile, in mid-July the Mars Express flight model was delivered to Alenia
from Astrium, Stevenage, UK where the propulsion system (engines and fuel
tanks) had been fitted (see earlier story). Alenia is installing mass
dummies of all instruments and sub-systems into the flight model. Later
this month, the Mars Express trailer will transport flight model plus mass
dummies to Intespace, Toulouse for four weeks of mechanical tests. These
will involve filling the oxidiser and fuel tanks with water and IPA
(iso-propyl alcohol), as fuel substitutes, so that the mass of the
spacecraft and its centre of gravity can be simulated accurately. The fuel
tanks have already been subjected to stringent ‘over pressure’ tests at
Astrium Stevenage, where they were filled with fuel substitute and tested
under very high pressure to ensure they could withstand unexpected
increases in fuel pressure.

By mid October, all mechanical tests should be completed and the spacecraft
will be transported back to Alenia, Torino where the mass dummies will be
removed and the flight models installed. “This process is expected to take
about six months, but by May next year, the spacecraft that will actually
fly to Mars should be ready for the flight model tests,” says Schmidt.

In parallel with the spacecraft tests, testing is still continuing on the
electrical and functional verification system test bench at Toulouse. “The
electrical tests are getting more complex, now that all the sub-systems
have to be integrated. These tests are expected to continue at a cracking
pace,” says Schmidt.


* Mars Express home page


[Image 1:]
The Mars Express flight model delivered at Alenia, mid-July 2001.

[Image 2:]
Unloading of the Mars Express flight model at Alenia, mid-July 2001.

[Image 3:]
Alenia installs mass dummies of all instruments and sub-systems into the
flight model, mid-July 2001.

[Image 4:]
The Mars Express flight model.