ESA Document - Emits - ESA
ESA Document - Emits - ESA ESA Document - Emits - ESA
s cryocooler heat lift [W] 1.5 1.4 1.3 1.2 1.1 1 0.9 0.8 0.7 0.6 0.5 0.4 0.3 0.2 0.1 0 0 0.2 0.4 0.6 0.8 1 1.2 tank diameter [m] 10 layers 20 layers 30 layers 40 layers 50 layers 60 layers 70 layers 80 layers cryocooler heat lift [W] HMM Assessment Study Report: CDF-20(A) February 2004 page 292 of 422 2 1.8 1.6 1.4 1.2 1 0.8 0.6 0.4 0.2 0 0 0.2 0.4 0.6 0.8 1 1.2 1.4 1.6 1.8 2 tank diameter [m] sink 300K sink 270K sink 260K sink 250K sink 240K sink 150K Figure 4-44: Cryocooler heat lift as function of the number of layers and tank diameter 4.3.4.3.8 Synthesis As seen here above, optimum can be reached with: • a performant insulation that depends on the number of layers of the MLI. This latest is set to 40 layers (DAM with goldenized external layers) • a low heat sink that depends on the location and accommodation of the tanks. A dedicated tank compartment (not pressurised) at 250K seems a reasonable compromise with constraints from the MAV vehicle (heat soaking at the interfaces) and from the hardware located in this compartment (coolers) • an appropriate medium for the storage: spherical tank with appropriate diameter, this is a compromise between cooling capability (that constrains the diameter downward) and the number of tanks (accommodation that constrains the number to match the allocated volume) • a heat lift provided by a mechanical cooler Presently available in Europe is the Astrium 20-50K two-stage Stirling cooler with a performance of 120 mW at 20K and about 300 mW at 30K, not suitable to this study (would drive a high number of tanks, more than 27 at both temperatures). The pre-cooler of this system however could be used with a performance about 800 mW at 30K. Hydrogen Per tank Budget total case sink [K] nbr of tank diameter MLI layers liquid pressure nbre of heat lift mass liquid thickness structural thermal input power thermal total dry input power [m] temp. [K] (MPa) cryo units [W] [kg] tank [mm] mass [kg] mass [kg] [W] mass [kg] mass [kg] [W] 1 300 40 0.44 40 22.9 0.2 1 349 3.0 0.4 0.7 0.5 28.0 351.9 378.7 1120.0 2 300 15 0.62 40 22.9 0.2 2 690 8.4 0.6 1.9 1.0 56.0 263.8 291.9 840.0 3 300 8 0.76 40 22.9 0.2 3 1050 15.5 0.7 3.4 1.5 84.0 211.1 238.7 672.0 4 300 17 0.66 40 31.4 1 1 784 7.3 3.1 11.3 1.1 46.0 160.2 352.4 782.0 5 300 6 0.94 40 31.4 1 2 1588 21.1 4.4 32.7 2.3 92.0 113.3 309.2 552.0 6 300 4 1.06 40 31.4 1 3 2023 30.2 4.9 46.8 2.9 138.0 111.2 298.5 552.0 7 250 14 0.64 40 22.9 0.2 1 331 9.2 0.6 2.1 1.1 23.0 131.0 159.8 322.0 8 250 5 0.88 40 22.9 0.2 2 672 24.0 0.8 5.4 2.0 46.0 93.0 119.7 230.0 9 250 3 1.04 40 22.9 0.2 3 940 39.7 1.0 8.8 2.8 69.0 83.1 109.6 207.0 10 250 6 0.94 40 31.4 1 1 763 21.1 4.4 32.7 2.3 37.0 63.5 259.4 222.0 11 250 2 1.34 40 31.4 1 2 1555 61.1 6.2 94.6 4.6 74.0 42.4 231.7 148.0 Table 4-12: Solutions Cases 9-11 appear interesting in terms of budgets and 11 is retained: two hydrogen tanks - diameter 1.34 m - with two single-stage Stirling coolers mounted on each pole of each tank. The
s HMM Assessment Study Report: CDF-20(A) February 2004 page 293 of 422 thickness (6.2 mm aluminium shell to match a internal pressure of 1 MPa) allows a good spreading of energy from the poles to the equatorial belt. Optimised mechanical support systems for the cryogen tanks should also be considered (PODS for example). The tanks are in an unpressurised section, so that –23C can be reached as a radiative environment. In these conditions, the moderate heat lift required (0.5 to 1W between 20 to 30K) to counter BO does not require significant development but modifications of existing hardware (Stirling coolers). If the environment has to be modified (external tanks submitted to environmental loads), or because of a more integrated system (with ECLS) resulting in larger tanks, the use of higher heat lift capability may become necessary and the choice of the cooling system oriented to recuperative systems (reverse Brayton, Joule Thomson cycles). As previously seen and within the study’s hypothesis, the oxygen tanks do not necessarily require a cooling capability. A tolerance to boil-off is accepted per design with an increased initial mass of oxygen liquid. Oxygen Per tank Budget total case sink [K] nbr of tank diameter MLI layers liquid pressure nbre of heat lift mass liquid thickness structural thermal input power thermal input power total mass [m] temp. [K] (MPa) cryo units [W] [kg] tank [mm] mass [kg] mass [kg] [W] mass [kg] [W] liquid [kg] 1 250 1 1.36 40 97.2 0.2 0 0 1454.6 1.3 19.8 4.8 0.0 4.8 0.0 1454.6 2 250 2 1.12 40 97.2 0.2 0 0 812.4 1.0 11.0 3.2 0.0 6.5 0.0 1624.9 3 250 3 1 40 97.2 0.2 0 0 578.3 0.9 7.9 2.6 0.0 7.7 0.0 1734.9 4 250 4 0.92 40 97.2 0.2 0 0 450.3 0.9 6.1 2.2 0.0 8.7 0.0 1801.2 5 250 1 1.46 40 119.6 1 0 0 1589.6 6.8 122.4 5.5 0.0 5.5 0.0 1589.6 6 250 2 1.22 40 119.6 1 0 0 927.5 5.7 71.4 3.8 0.0 7.7 0.0 1855.0 Table 4-13: Options Case 1, a tank of a diameter 1.36 m appears as the best solution of a no coolers trade-off and could be integrated with the 2 hydrogen tanks. However, an appreciable mass saving could be obtained with a cooling capability and is the option to prefer for an optimised system. 4.3.4.4 Budget 4.3.4.4.1 Synthesis per subsystem (main features) Fluid loops Primary loop Pump assembly: 67 kg, 463W nominal (950kg/hr) (x 2) Condenser heat exchangers: 20.6 kg (x 2),cold plates: 3.4 kg (x 10), valves (on/off, manual): 4 kg (x 20) 120 kg of tubing (dry including insulation, brackets) + 20 kg of water Secondary loop Pump assembly: 56.7 kg, 311W nominal (x 2) Heat exchangers: 15.9 kg (x 4), cold plates: 3.4kg (x 5), valves (on/off, manual): 4 kg (x 5) 36 kg of tubing (dry including insulation, brackets) + 31 kg of ammonia Body-mounted radiator Passive thermal control Cylindrical/conical radiator of 22 m 2 , 0 kg (transferred to structure budget) Insulation 193 kg for the main body of the transfer vehicle (to check the status of PMOD). 50 kg are provisioned for specific external and internal elements insulation. Heating system 728W installed power Two control units (1 on), each 6 kg, 29W when shell heaters are 100% duty cycle
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s<br />
cryocooler heat lift [W]<br />
1.5<br />
1.4<br />
1.3<br />
1.2<br />
1.1<br />
1<br />
0.9<br />
0.8<br />
0.7<br />
0.6<br />
0.5<br />
0.4<br />
0.3<br />
0.2<br />
0.1<br />
0<br />
0 0.2 0.4 0.6 0.8 1 1.2<br />
tank diameter [m]<br />
10 layers 20 layers 30 layers 40 layers<br />
50 layers 60 layers 70 layers 80 layers<br />
cryocooler heat lift [W]<br />
HMM<br />
Assessment Study<br />
Report: CDF-20(A)<br />
February 2004<br />
page 292 of 422<br />
2<br />
1.8<br />
1.6<br />
1.4<br />
1.2<br />
1<br />
0.8<br />
0.6<br />
0.4<br />
0.2<br />
0<br />
0 0.2 0.4 0.6 0.8 1 1.2 1.4 1.6 1.8 2<br />
tank diameter [m]<br />
sink 300K sink 270K sink 260K sink 250K<br />
sink 240K sink 150K<br />
Figure 4-44: Cryocooler heat lift as function of the number of layers and tank diameter<br />
4.3.4.3.8 Synthesis<br />
As seen here above, optimum can be reached with:<br />
• a performant insulation that depends on the number of layers of the MLI. This latest is set<br />
to 40 layers (DAM with goldenized external layers)<br />
• a low heat sink that depends on the location and accommodation of the tanks. A<br />
dedicated tank compartment (not pressurised) at 250K seems a reasonable compromise<br />
with constraints from the MAV vehicle (heat soaking at the interfaces) and from the<br />
hardware located in this compartment (coolers)<br />
• an appropriate medium for the storage: spherical tank with appropriate diameter, this is a<br />
compromise between cooling capability (that constrains the diameter downward) and the<br />
number of tanks (accommodation that constrains the number to match the allocated<br />
volume)<br />
• a heat lift provided by a mechanical cooler<br />
Presently available in Europe is the Astrium 20-50K two-stage Stirling cooler with a<br />
performance of 120 mW at 20K and about 300 mW at 30K, not suitable to this study (would<br />
drive a high number of tanks, more than 27 at both temperatures). The pre-cooler of this system<br />
however could be used with a performance about 800 mW at 30K.<br />
Hydrogen<br />
Per tank<br />
Budget total<br />
case sink [K] nbr of tank diameter MLI layers liquid pressure nbre of heat lift mass liquid thickness structural thermal input power thermal total dry input power<br />
[m]<br />
temp. [K] (MPa) cryo units [W] [kg] tank [mm] mass [kg] mass [kg] [W] mass [kg] mass [kg] [W]<br />
1 300 40 0.44 40 22.9 0.2 1 349 3.0 0.4 0.7 0.5 28.0 351.9 378.7 1120.0<br />
2 300 15 0.62 40 22.9 0.2 2 690 8.4 0.6 1.9 1.0 56.0 263.8 291.9 840.0<br />
3 300 8 0.76 40 22.9 0.2 3 1050 15.5 0.7 3.4 1.5 84.0 211.1 238.7 672.0<br />
4 300 17 0.66 40 31.4 1 1 784 7.3 3.1 11.3 1.1 46.0 160.2 352.4 782.0<br />
5 300 6 0.94 40 31.4 1 2 1588 21.1 4.4 32.7 2.3 92.0 113.3 309.2 552.0<br />
6 300 4 1.06 40 31.4 1 3 2023 30.2 4.9 46.8 2.9 138.0 111.2 298.5 552.0<br />
7 250 14 0.64 40 22.9 0.2 1 331 9.2 0.6 2.1 1.1 23.0 131.0 159.8 322.0<br />
8 250 5 0.88 40 22.9 0.2 2 672 24.0 0.8 5.4 2.0 46.0 93.0 119.7 230.0<br />
9 250 3 1.04 40 22.9 0.2 3 940 39.7 1.0 8.8 2.8 69.0 83.1 109.6 207.0<br />
10 250 6 0.94 40 31.4 1 1 763 21.1 4.4 32.7 2.3 37.0 63.5 259.4 222.0<br />
11 250 2 1.34 40 31.4 1 2 1555 61.1 6.2 94.6 4.6 74.0 42.4 231.7 148.0<br />
Table 4-12: Solutions<br />
Cases 9-11 appear interesting in terms of budgets and 11 is retained: two hydrogen tanks -<br />
diameter 1.34 m - with two single-stage Stirling coolers mounted on each pole of each tank. The
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