Crew Return Vehicle - Medical Considerations

Medical Considerations

The ISS is equipped with a Health Maintenance Facility (HMF) to handle a certain level of medical situations, which are broken into three main classifications:

• Class I: non-life-threatening illnesses and injuries (headache, lacerations).
• Class II: moderate to severe, possibly life-threatening (appendicitis, kidney stones).
• Class III: severe, incapacitating, life-threatening (major trauma, toxic exposure).

However, the HMF is not designed to have general surgical capability, so a means of evacuating a crew member in case of a medical situation that is beyond the HMF's capabilities is essential.

A number of studies have attempted to assess the medical risks for long-term space station habitation, but the results are inconclusive, as epidemiological data is lacking. It is, however, understood that longer periods in space increase the risk of serious problems. The closest estimates show an illness/injury rate of 1:3 per year, with 1% estimated to require emergency evacuation by means of a CRV. For an eight-person ISS crew, this results in an expected need for a CRV flight once every four to 12 years. These estimates have been partially corroborated by experiences on board the Soviet Union's Mir space station. In the 1980s, the Soviets had at least three incidents where cosmonauts had to be returned under urgent medical conditions.

Because of its potential use as a medical evacuation method, the CRV design was required to address a number of issues that are not factors for a standard manned space vehicle. Foremost of these are the g-loadings as influenced by reentry profiles and deceleration/landing methods upon patients with hemorrhagic shock issues. Patient security issues are more critical for injured astronauts than for uninjured personnel. Additionally, depending on the nature of the injury, it may be unlikely that the patient could be placed in an environmentally contained space suit or minicapsule, therefore the CRV needs to have the capability to provide a "shirt sleeve" environment. The ability to address air purity issues is included in this requirement, as air purity is especially critical in medical as well as toxic exposure situations.