What would change the answer if it were measured?
Where the model is guessing
The uncertainty register, sorted by how much each unknown moves the endurance number. This is the research queue: what would have to be measured before any of the rest is worth trusting.
Where the model is guessing
Values nobody has published, with the range and what measurement would resolve each. A number without a source fails the build here, so anything genuinely unknown has to be declared rather than quietly invented. This list is the project's research queue.
Defect-dominated, as above.
Resolved by: Bench measurement.
Nitrogen is a much larger molecule and permeates far more slowly, but the ratio across a metallised barrier is dominated by pinhole defects rather than by bulk solubility, and defect density is a manufacturing variable nobody publishes.
Resolved by: Measure on the same coupon as the hydrogen test. Inward nitrogen flux is what sets the purity decay rate and therefore the electrolyzer duty cycle.
Same back-computation, same lack of primary data.
Resolved by: Not worth resolving.
Strongly dependent on ambient temperature, humidification state, and whether the stack is kept warm.
Resolved by: Measure on the selected system at the coldest expected condition.
No supplier publishes a price for a 0.21 kg/m2 para-aramid plus metallised-PET airship cell laminate at 15,000 m2. The nominal is Ripstop by the Roll's 1.43 oz Dyneema composite fabric at $45.05/m2. IT IS NOT MATCHED ON AREAL MASS: that fabric is 48.5 g/m2 against the cell film's 210, a factor of 4.3. What it is matched on is MANUFACTURING KIND, a multi-layer film-and-fibre laminate made in small quantities by a converter for a technical market, which is the only property of it that says anything about price. The band spans a factor of six because that is what one unmatched proxy is worth.
Resolved by: A quotation from a barrier film converter for 15,000 m2 of the selected laminate. This is the single largest line in the bill of materials and it is the one with no price.
Entirely a behavioural and equipment choice. A submarine crew manages on 12; a household figure is over 100. The range spans a factor of five and it is the largest single lever on the water budget.
Resolved by: A decision, not a measurement. Choose the washing equipment and the standard of living, then this number follows.
Merchant hydrogen is about $1.09/kg at the plant and delivery by gaseous tube trailer adds $9.46/kg in 2016 dollars, which is $13/kg escalated. Retail station prices in California exceed $30/kg. What a one-off 2.4 tonne delivery to a rural site costs is not published.
Resolved by: A delivered quotation from an industrial gas supplier for a single 2.4 tonne fill.
Marine and aerospace practice both specify a glass barrier but quote thickness as a number of plies rather than in millimetres, and ply thickness varies with the cloth. Two plies of 200 gsm glass is the common recommendation.
Resolved by: Fix the cloth areal weight and the layup, then measure a cured coupon. A conservative build simply uses more plies: the mass penalty is negligible and the failure mode is not.
Varies enormously across the band and with season. The low end is the eastern subtropical ocean, the high end approaches the ITCZ.
Resolved by: Reanalysis precipitation data for the specific station, which the mission module will ingest in phase 5.
Typical rather than best-in-class. Derived from the sub-1 L/(m2 day) helium figure quoted for multi-ply polyester and Tedlar airship envelopes, scaled for hydrogen.
Resolved by: Bench measurement on a candidate coupon.
Build order
Each phase has a validation gate. Nothing downstream of a failing gate is trustworthy, so a phase has to pass before the next opens.
- 1FoundationUnits, atmosphere, gas properties, buoyancyGATES PASS
- 2Does it close?Permeation, electrolysis, fuel cell, solar, water balanceGATES PASS
- 3Can it be built?Structure, buckling, mass fraction versus sizeIN PROGRESS
- 4Does it fly?Aerodynamics, propulsors, 6-DOF with added massGATES PASS
- 4bThe powertrain decisionFuel choice, TBO consumables, dissimilar redundancyIN PROGRESS
- 5Can it be lived in?Habitat, life support, thermal, the year-long missionIN PROGRESS
- 6Will it kill me?Hydrogen safety, lightning, icing, failure injection, regulationIN PROGRESS
- 7The siteDesign explorer, flight simulator, mission playerIN PROGRESS
- 8Build documentationFrame drawings, laminate schedules, bill of materialsPENDING