boiloff

This study clearly identifies the need to decrease the boiloff rate by an order or magnitude or more.

Better insulation is needed, particularly on cryogenic tanks, to prevent too much propellant boiloff during coast.

The coldest ion is rather sorted out by using an ion evaporation technique called boiloff.

The cryogenic boiloff technique concentrated the fraction of the mass-2 isotope of hydrogen to a degree that made its spectroscopic identification unambiguous.

An active cryogenic depot is a passive depot with additional power and refrigeration equipment/cryocoolers to reduce or eliminate propellant boiloff.

This is because of both the low density and the additional insulation required to minimize boiloff (a problem which does not occur with kerosene and many other fuels).

In one concept, hydrogen boiloff is also redirected to reduce or eliminate liquid oxygen boiloff and then used for attitude control, power, or reboost.

An additional flight of the Ares V heavy launch vehicle was required to stage a Mars mission due to 70 tons of boiloff, assuming 0.1% boiloff/day.

Lunar or Mars missions will require require weeks to months to accumulate 10,000s to 100,000s kgs of propellant, so additional equipment may be required on the transfer stage or the depot to mitigate boiloff.

For cryogenic vehicles and cryogenic depots; additional boiloff mitigation equipment is typically included on the transfer stage, reducing payload fraction and requiring more propellant for the same payload unless the mitigation hardware is expended.

The design issues include propellant settling and transfer, propellant usage for attitude control and reboost, the maturity of the refrigeration equipment/cryocoolers, and the power and mass required for reduced or zero boiloff depots with refrigeration.

Recent design work has developed an approach to substantially reduce hydrogen boiloff, and to economically utilize the small remaining boiloff product for requisite in-space tasks, essentially achieving zero boil off (ZBO) from a practical point of view.

Tests conducted at the NASA Lewis Research Center's Supplemental Multilayer Insulation Research Facility (SMIRF) over the summer of 1998 demonstrated that a hybrid thermal control system could eliminate boiloff of cryogenic propellants.

Non-cryogenic, earth-storable liquid rocket propellants including RP-1 (kerosene), hydrazine and nitrogen tetroxide (NTO), and mildly cryogenic, space-storable propellants like liquid methane, can be kept in liquid form with less boiloff than the cryogenic fuels, but also have lower specific impulse.