Human Powered Flight
People could actually fly in the relatively low gravity of the moon, with strap on wings.
This would require a large pressurized volume. A lunar base might not have enough volume at first. But an underground lava tube type habitat probably would.
When people are ready to produce about 1,000,000 cubic meters of sintered regolith brick and use it with appropriate reinforcing bars to build a suitable dome, then they should be able to produce a flying track on the moon. The dome should be of semicylindrical cross section like a quonset hut but with a 100 foot span of the arch and extend 2000 feet down the axis of the arch in a figure eight pattern with the building crossing over itself being carried on a ramp up to an arch where the upper floor crosses over the lower floor. A thirty-six meter thick roof of sintered brick should hold in one atmosphere pressure by its weight so it would not need to have anchors holding it down at its base and the roof would not be under tension. Lunar regolith is about one and a half times as dense as water and the sintering process would add to its density. A metal liner for the dome could hold the internal atmosphere that would otherwise seep through porous sintered brick. It could work but, with a thirty-six meter thick roof, one might as well dig a tunnel thirty-six meters deep. It would be possible to go with a 100 foot (30.5 meter) diameter tube with the tube wall under tension to hold in one atmosphere pressure. It would be covered with six meters of regolith for radiation protection.
Earth bound test
To test the popularity of a flying track, one could be built on Earth. The specifications of the track would be somewhat different. Internal pressure in the figure eight dome would be a quarter percent higher than the atmospheric pressure outside to hold up the gas tight fabric roof. The dry gas inside should be 78% octafluoropropane by volume, 21.96% oxygen, and 0.04% carbon dioxide, with enough water vapor for breathable humidity. This heavy gas mixture would allow other people than top condition athletes to fly human powered aircraft because it is six and a quarter times as dense as air. So, the amount of lift for a certain air foil moving through the air at a certain speed would be six and a quarter times the lift from air. Less power would be needed to lift the weight of the aircraft and pilot. The octafluoropropane is something used in some medical test procedures such as ultra sound imaging. So, it is unlikely to have serious toxic effects. People who use the flying track would need to breath ordinary air for a while in a transition chamber to get the octafluoropropane removed from their systems. The gas would be passed through a counter current heat exchanger to a cold trap at minus 45 degrees centigrade. This would remove the octafluoropropane to recycle it and prevent it from getting loose in the atmosphere of Earth as a contaminant. The cold trap would also remove carbon dioxide and water vapor, so, scrubbed gas would be saved as a source of pure oxygen once nitrogen from the breathing gas transition process is removed. Late transition process scrubbed gas would just be dumped. People would be provided with fresh air instead of the gas to be scrubbed. When people have the octafluoropropane removed from their systems they will no longer sound like demons as they did while using the track.
Human powered blimps might fly on a track in such a dome with heavy interior gas mixture. A six meter long, two meter diameter blimp would have a lifting capacity of about 158 kg which might be enough to lift pilot and aircraft. The lifting gas would be ordinary air, the same gas as the pilot breathes so there would not be separate compartments for breathable gas and lifting gas. Separate balloonettes for freon-12 and dome interior gas would be used to maintain trim. With the trim balloonettes in the rear, freon 12 would be condensed allowing dome interior gas to enter the blimp, isolated in the balloonette, providing nose up pitch trim. The entry air lock would be at the bottom of the blimp serving to anchor the blimp and allowing the pilot or pilot and copilot could enter. The blimp door and access area door would be conformal so there would be very little space between them, which space would be purged with pure oxygen which is a component of both the lifting gas and the heavy dome interior gas. Development would determine the final dimensions of the blimp but 8 meters long and 2.45 meters diameter might be right for a craft to carry pilot and copilot. A completely indoor operation of the aircraft would simplify a number of design considerations for the blimp itself.
