What Happened To Beagle 2
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Beagle 2 was supposed to have landed on the Martian surface on December 25th 2003 but all contact was lost and whatever happened to it still remains a mystery.
Attempts were made throughout January and February 2004 to contact Beagle 2 using the Mars Express Orbiter however, no communication was ever established and it was declared lost on 6 February 2004.
After a thorough investigation a number of scenarios of possible failures were published:-
- Beagle entered in atmospheric conditions outside the range assumed by its designers and could have burnt up. The scenario that it may have “bounced off into space” has been put forward but this does not stand up to close technical scrutiny. The amount of dust in the atmosphere often varies widely, changing its density and temperature characteristics. However, the chosen margins on the design of the heat shield and the thermal loads it can withstand are such that the burn-up scenario is unlikely, and even the worst case density variations certainly are not such that, given the steep entry flight path angle at entry, the craft could conceivably have left the atmosphere again (see also Section 6.1 of the Inquiry Report, which states explicitly: “the Commission concludes that deviation of the atmospheric entry conditions is not a probable failure mode of the mission”);
- The probe’s parachute or cushioning airbags failed to deploy or deployed at the wrong time. This is supported by the observation that throughout the transfer to Mars, the outgassing of some substance and subsequent condensation on optical components of the Mars Express spacecraft carrying the Beagle lander was observed. This observation would be consistent with a leak in the gas generators of Beagle’s airbags;
- Beagle’s backshell tangled with the parachute preventing it from opening properly. It is not clear whether the difference in air drag between the probe with the parachute deployed and the back shell of the heat shield is sufficient to guarantee a safe separation distance (see Section 5.4.4 of the Inquiry Report);
- Beagle became wrapped up in its airbags or parachute on the surface and could not open. Entanglement with the parachute appears plausible in view of the fact that the parachute’s strop was shortened from the original design to save mass. Assuming that the airbags deployed, Beagle would, in the scenario, have bounced off the surface right back into the descending parachute (see also Section 5.4.6 of the Inquiry Report).Beagle may have jettisoned its airbags too early, before it had come to a complete rest on the surface. For mass and cost reasons, the airbag jettison device was designed to be triggered by a timer rather than by acceleration sensors that would have discerned when the lander package had stopped moving. Given that the landing package of NASA’s Spirit rover mission rebounded off the surface in Gusev crater numerous times before coming to a standstill – taking much more time than anticipated – Beagle’s timer may have been set to a too short time (see Section 5.4.8 of the Inquiry Report);The parachute deployment sequence was designed to be triggered by three accelerometers. The system was not designed for a “best out of three” logic. Rather, the first accelerometer to compute that a safe deployment velocity had been reached would trigger the parachute deployment sequence, even if the accelerometer readout were faulty.