N° 42–1995: Possible extension of EUROMIR mission and ESA's first spacewalk

The next highlight of EUROMIR 95 is ESA's first spacewalk (or Extra-Vehicular Activity) on Friday 20 October. At approximately 13:00 hrs (CET), together with his Russian colleague Sergei Avdeev, Reiter will step out of Mir and start work on the outside of the space station, for 3 or 4 hours. This Extra-Vehicular Activity (EVA ) will be performed to deploy elements of the European Science Exposure Facility (ESEF) - the astrophysics and space environment payloads of the EUROMIR 95 mission - and to change cartridges on a Russian experiment nearby. Both these payloads are mounted on the Spektr module.

Though not a first for Europe, this will be the first space sortie by an ESA astronaut (Jean-Loup Chretien of the French national space agency, CNES, had already taken a spacewalk outside Mir, back in 1988).

A spacewalk like this involves intensive training, mainly carried out at the Cosmonaut Training Centre in Star City, near Moscow. The special type of training required for EVA consists of practising all the manoeuvres in a water tank (the Hydrolaboratory, as the Russians call it) which, together with a specially weighted and adapted space suit, provides pseudo- weightless conditions. The crew member in training uses special neutrally buoyant mockups of the hardware to be handled on orbit and models of the spacecraft surfaces over which the astronaut or cosmonaut must move.

The EVA itself will last perhaps 3 to 4 hours, but preparations and associated activities will take place during a period of 5 days set aside especially for this purpose. The ESEF and other EVA- related hardware will be assembled and checked inside, before being carefully packed in a specially designed EVA bag. Inside this bag, items are tethered so that on removal they cannot float out of the crew member's reach. For the 4 ESEF items, a single tether is threaded through their handles in the order in which they will be installed.

The complex EVA procedurehas been designed with crew safety in mind. The suited crew members will leave the Kvant-2 airlock one at a time, with the second to leave (Avdeev) handing the package of payloads out to the first (Reiter) through the hatch. The Russian must then make his way along the device (known as "Strelya") used to move crew and payloads around the station which is a telescopic arm whose base is attached to the core module of the station. Reiter then attaches himself and the payload package to the end of the Strelya. Avdeev then operates Strelya with crank handles so as to move the astronaut from the outer end of Kvant-2 to the outer end of Spektr. Avdeev then moves back down Strelya to join Reiter. They now need to move around the periphery of Spektr to the other side, where the ESEF is located. All operations are carried out with the help of a pair of tether lines and karabiners attached to each suit.

On reaching the ESEF, a platform on which 4 items must be carefully installed, the crew members attach themselves at opposite ends of the work area with the payload package at the outer end. Reiter will then withdraw a 2 m tether from the payload bag and pass the end through wire loops attached to 4 covers on the ESEF platform. Removal of these covers exposes the four sites for ESEF element installation. The covers are detached by pulling a wire loop which releases a locking pin. They carry a radiation-monitoring experiment which has been collecting data since Spektr was launched. They will be returned to Earth by the crew of STS-74, the US shuttle mission which will visit Mir in early November.

Once the covers are removed, the four ESEF elements, two exposure cassettes, a spacecraft environment-monitoring package and a control electronics box, will be placed in their respective positions in turn. They are each locked in place with a single-lever locking mechanism controlled mating of an electrical connector. The tether threaded through the handles prior to the EVA will then be removed, and the locking handles for the exposure cassettes will be released, ready for opening operations when the crew member have returned inside.

Meanwhile, the third crew member, inside the station, will apply power to the platform and verify the correct status of each element. Any incorrect status will necessitate repetition of the installation procedure. Any further difficulty will be discussed with experts on the ground, including the designers and builders of the ESEF, the Institut d'Astrophysique Spatiale from Orsay, near Paris.

After installing the ESEF and checking it out, the crew move to the second payload to be serviced, less than two metres away on Spektr.

As with most EVAs, simple tasks are made complex by the environment and by the limitations of spacesuit design. The semi-rigid Russian suit, in which the rigidising effect of a pressurised garment has been partially eliminated, is still tiring to work in, and combined with the large cross-section and stiffness of EVA gloves, it makes EVA procedures time- consuming. Added to this is the problem of light at the worksite where eclipses make detailed work impossible.