Vacuum Environment

Question 1

Under what condition does outgassing occur?

Answer 1

when the ambient pressure is less than the vapour pressure of the material. The vapours can then recondense on important equipment and impact performance such as optics

Question 2

Why is lubrication difficult in vacuum

Answer 2

oils and greases usually used to lubricate will sublimate

Question 3

Why is it important to properly bleed the air from inside components on the spacecraft, particularly electronic ones?

Answer 3

Because paschen breakdown is inversely dependant on the ambient pressure, so if the air leaks, this will reduce pressure and an electrical signal could result in a discharge that damages the equipment

Question 4

Cold-welding can cause mechanisms to jam easily in vacuum. What are two low-vapour pressure oils used to protect against this?

Answer 4

1. Fomblin Z25 oil
2. Braycote 602 grease

often thickned with PTFE and Molybdenum Sulphide (MoS2)

Question 5

For rapidly moving parts, what state of lubricant is best?

What about for one-shot devices and slow moving parts?

Answer 5

Liquid for fast parts

Solid for one shot and slow parts