Due to micro-meteorites and space debris, a non-neglectable probability exists of a wall perforation particularly during a long space journey or during the life of a space station.
Analysis and tests have been performed at ESTEC and at the Technical University of Delft of various methods to close a hole manually; it has been shown that with certain patches of silicon rubber, polyethylene or flame-retardant similar polymer foams, holes can be easily and adequately sealed without imposing additional risks to the astronaut. Proper sealing maintains for several days, even with hole sizes up to 10 cm2 (this latter size being the largest ones tested, which size corresponds to a probability of less than order 10-2 for a ten years life of the 1993 Station Freedom baseline). The method works also for holes difficult to reach and for holes with large crater-like and sharp edges.
Present operational practise calls for emergency evacuation procedures rather than attempts to seal the hole. A certain anxiety exists for pressure leaks amongst engineers, and managers involved in space operations as well as amongst many astronauts. This anxiety can be taken away, using the proposed patch materials and using the reported tests as training and demonstration. It is felt that in many cases, a crew action to seal a hole serves crew safety better than the egress of a pressurized and in principle liveable module.
Realizing the ease and effectiveness of the proposed sealing method, It is recommended to fly such patches (whose mass is less than 100 grams) on each of the future manned spaceflights.