Experimental + reference-model benchmark
NASA K-Site LH₂ self-pressurization
A primary-source benchmark against NASA TM-105411. OffshoreLH2 is gated against NASA’s homogeneous reference because the present tank is a lumped equilibrium model; the measured stratified experiment is shown separately as model-form evidence.
What was tested
Quasi-steady pressure-rise rate and full pressure-versus-time response for a flightweight liquid-hydrogen tank under low wall heat flux.
Primary source
Van Dresar, N. T.; Lin, C. S.; Hasan, M. M. (1992), Self-Pressurization of a Flightweight Liquid Hydrogen Tank: Effects of Fill Level at Low Wall Heat Flux, NASA TM-105411 / AIAA-92-0818.
Values taken from NASA
| Quantity | Value used | NASA basis |
|---|---|---|
| Tank internal volume | 4.89 m³ | Experimental apparatus |
| Tank internal surface area | 14.0 m² | Experimental apparatus |
| Initial pressure | ≈103 kPa | Tank reduced to atmospheric pressure before self-pressurization |
| Wall heat fluxes | 2.0 and 3.5 W/m² | Figure 2 / test procedure |
| Cryoshroud temperatures | 294 K and 350 K | Used to obtain the two nominal heat fluxes |
| Fill levels | 29%, 49%, 83–83.5% | Figure 2 and earlier 83% campaign |
| Experimental sampling | 0.5 h | Paper states data were sampled at 1/2-hour intervals |
| Starting condition | Steady boil-off | Figure 2 dataset |
Quasi-steady pressure-rise results
The acceptance rule was fixed at ≤10% relative error against NASA’s published homogeneous-theory slope.
| q″ | Fill | NASA measured | NASA homogeneous | OffshoreLH2 | Error vs homogeneous | Status |
|---|---|---|---|---|---|---|
| 2.0 W/m² | 29% | 3.820 kPa/h | 2.730 | 2.4716 | 9.465% | PASS |
| 3.5 W/m² | 29% | 8.210 | 4.830 | 4.9382 | 2.240% | PASS |
| 2.0 W/m² | 49% | 2.720 | 1.860 | 1.9719 | 6.017% | PASS |
| 3.5 W/m² | 49% | 6.070 | 3.710 | 3.8013 | 2.460% | PASS |
| 0.35 W/m² | 83.5% | 0.223 | 0.198 | 0.20525 | 3.661% | PASS |
| 2.0 W/m² | 83.5% | 3.470 | 1.460 | 1.3624 | 6.688% | PASS |
| 3.5 W/m² | 83.5% | 8.140 | 2.630 | 2.7204 | 3.436% | PASS |
Full pressure-time results
Figure 2 was digitized from the primary NASA PDF. The predeclared gate is pressure-rise NRMSE ≤10% against the NASA homogeneous curve.
| Case | Pressure-rise NRMSE | Status |
|---|---|---|
| 2.0 W/m², 29% | 2.30% | PASS |
| 2.0 W/m², 49% | 3.36% | PASS |
| 2.0 W/m², 83% | 4.58% | PASS |
| 3.5 W/m², 29% | 0.32% | PASS |
| 3.5 W/m², 49% | 0.98% | PASS |
| 3.5 W/m², 83% | 1.73% | PASS |
Measured stratified experiment
The measured NASA pressure rise is higher than the homogeneous prediction because the real tank develops gravity-driven thermal stratification and natural convection. OffshoreLH2 does not resolve those spatial effects, so this comparison is deliberately descriptive only. The disagreement is retained rather than tuned away.
Digitization check: fitted slopes from the digitized experimental markers reproduce NASA Table 1 within 0.31–2.41% across the six pressure-time cases.
Reproducibility
reference/nasa_k_site_pressure_timeseries_digitized.csvreference/nasa_k_site_pressure_timeseries_PROVENANCE.mdvalidation_cases/lh2_nasa_k_site/timeseries.cppscripts/analyze_nasa_k_site_timeseries.py