Cryogenic fluid supply from supercritical storage system

Details Cryogenic fluid supply from supercritical storage system Cryogenic fluid supply from supercritical storage system

2001-02-07

2002-04-23

Capossela, Ronald (Department: 3744)

Refrigeration

Storage of solidified or liquified gas

Liquified gas transferred as liquid

C062S007000

Reexamination Certificate

active

06374618

ABSTRACT:

TECHNICAL FIELD
The present invention relates generally to the safe storage and transfer of cryogenic fluids inside the cargo bay of a reusable launch vehicle, and more particularly to cryogenic fluid transfer systems for transferring supercritical cryogenic fluids to subcritical storage tanks in zero gravity environments, thus eliminating potential ignition hazards associated with cryogenic oxygen and hydrogen storage and management through a unique fluid transfer process in a space environment.
BACKGROUND OF THE INVENTION
Cryogenic fluids such as liquid oxygen (LO2) and liquid hydrogen (LH2) are widely used by the aerospace industry as propellants, reactants for power generation, life support systems, sensor cooling, and the like. Although launch vehicles, such as the Space Shuttle, use these cryogens routinely with on-board systems, the storage and handling of these cryogens has been discouraged for payloads due to serious safety issues arising from storage and handling of cryogens inside a closed payload bay compartment. This is due to the fact that reusable launch vehicles (RLV), such as the Space Shuttle, impose unique safety requirements on cryogenic payloads because the payload must be loaded with cryogens on the ground inside a closed compartment, and the RLV must return to the ground with the payload intact in case of an aborted mission. Because the LO2 or LH2 tank is inside a closed cargo bay, serious safety issues arise during loading or after an aborted mission touchdown from small leaks and post landing venting. The concern is that a small amount of hydrogen or oxygen leakage over an extended period of time, e.g., during loading, launch, or post-touchdown, can cause a buildup of hazardous gas concentrations which can result in a fire or catastrophic explosion causing the possible loss of the space vehicle and its crew. Safety issues associated with ignition and explosion can be eliminated if the payload does not have cryogens below altitudes where ignition/explosion can occur. For hydrogen and oxygen the safe altitude where ignition does not occur is above 160,000 ft. At this altitude the atmospheric pressure is too low to support ignition, and therefore hydrogen and oxygen behaves as inert fluids like nitrogen or helium.
Because RLV's, such as the Space Shuttle, contain cryogenic storage tanks for on-board power generation and life support systems, it is possible to transfer hydrogen or oxygen into payloads once the vehicle reaches a safe altitude where ignition hazards are eliminated and where there is sufficient time to completely dump and vacuum inert the payload storage tanks prior to landing. One source of cryogenic fluid is the supercritical storage tanks used to generate electrical power for the Shuttle. The Shuttle's supercritical storage system consists of LO2 and LH2 tanks located in the Orbiter vehicle and also additional storage tanks located on a palette inside the cargo bay referred to as the extended duration orbiter (EDO) tanks. To eliminate liquid acquisition devices that are typically needed in a zero gravity environment, the cryogenic LH2 and LO2 is stored at super critical pressures. Consequently, the fluid is stored as a single phase fluid with no liquid vapor phase. The supercritical pressure is maintained by adding electrical heat to the tank to offset the pressure decay from fluid expulsion. Because the cryogens are stored at supercritical pressures, fluid transfer to a subcritical cannot be done directly.
The cryogenic storage tanks on the EDO pallet are typically tied into (i.e., in fluid communication with) both the fuel cells/life support systems and the pre-existing standard supercritical storage tanks in the orbiter, as shown in the configuration depicted in FIG.
1
. The EDO cryogenic fluid storage system
10
typically consists of a tank
12
having a fill port
14
and a vent port
16
. A conduit
18
from the vent port
16
branches off into another conduit
20
that leads to a relief valve
22
which in turn leads to a common relief line
24
. Conduit
18
also branches off into another conduit
26
which leads to a shutoff valve
28
which in turn leads to a conduit
30
which is in fluid communication with the orbiter cryogenic fluid storage system
32
. The orbiter cryogenic fluid storage system
32
typically consists of a tank
34
having a fill port
36
and a vent port
38
. A conduit
40
from the vent port
38
leads to a shutoff valve
42
which leads to a conduit loop
44
having a check valve
46
located therein. A conduit
48
from the shutoff valve
42
leads to a vent disconnect assembly
50
. Conduit
30
from vent port
16
is in fluid communication with conduit loop
44
and conduit
48
. A conduit
52
from fill port
36
leads to shutoff valve
54
which leads to a conduit loop
56
having a check valve
58
located therein. A conduit
60
from the shutoff valve
62
leads to a fill disconnect assembly
62
. A conduit
64
from the fill port
14
leads to a shutoff valve
66
which in turn leads to a conduit
68
which is in fluid communication with conduit
60
. In order to supply cryogenic fluid to the orbiter's fuel cells and life support systems, it is necessary to provide supply conduits from the two main sources of cryogenic fluid. The EDO cryogenic fluid storage tank
12
is provided with a conduit
70
which leads to a check valve
72
which in turn leads to a conduit
74
which is in fluid communication with the orbiter's fuel cells and life support systems. Likewise, the orbiter cryogenic fluid storage tank
34
is provided with a conduit
76
which leads to a check valve
78
which in turn leads to a conduit
80
(which ties into conduit
74
) which is also in fluid communication with the orbiter's fuel cells and life support systems.
Therefore, there is a need for a system that permits the safe and efficient transfer of cryogenic fluids from supercritical storage systems to subcritical storage systems, especially in low g and/or zero-g vacuum environments.
The present invention provides for the safe transfer of LO2 or LH2 from the Space Shuttle supercritical tanks in a low g vacuum environment which enables cryogenic upper stages to be flown in the cargo bay of the Space Shuttle or second generation RLV. The cryogens that can be transferred to a payload cryogenic tank may be used to demonstrate long term cryogenic fluid management, power upper stages, and provide reactants for power generation, cool sensors or electronic equipment.
SUMMARY OF THE INVENTION
It is therefor an object of the present invention to provide a new and improved cryogenic fluid transfer system.
It is another object of the present invention to provide a new and improved cryogenic fluid transfer system for use in zero gravity environments.
It is still another object of the present invention to provide a new and improved cryogenic fluid transfer system for transferring a cryogenic fluid from a supercritical cryogenic fluid storage system to a subcritical cryogenic fluid storage system.
In accordance with one embodiment of the present invention, a cryogenic fluid transfer system for transferring a cryogenic fluid from a supercritical cryogenic fluid storage system is provided, comprising:
a first subcritical cryogenic fluid storage system for receiving the cryogenic fluid from the supercritical cryogenic fluid storage system;
a conduit for providing fluid communication between the supercritical cryogenic fluid storage system and the first subcritical fluid storage system; and
a heat exchanger assembly in contact with the conduit, the heat exchanger assembly located downstream of the supercritical cryogenic fluid storage system and upstream of the first subcritical fluid storage system;
wherein the heat exchanger assembly cools the cryogenic fluid expelled from the supercritical cryogenic fluid storage system prior to the cryogenic fluid being introduced into the first subcritical fluid storage system.
In accordance with another embodiment of the present invention, a cryogenic fluid transfer system is

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