Possibilities of Dirigible Airships
Airships since the Hindenburg and R101 have had a very bad press. Lighter than air structured airships could transport large volumes of goods and people with minimal or almost silent propulsion. I could envisage an modern airship using helium or hydrogen made with modern radar absorbing materials, being a stable troop transport, especially if the ship used foldable LCD type external materials.
Basically a TV screen that projected the image of the area behind it. It would not show up on radar and may only give the impression of haze during the day. At night it may be mainly invisible if it projected the stars behind it. For just night-time use all that would be needed would be dark matt non-light reflective materials.
A water ballasted hydrogen lift based system would also have the advantage that it could be used to run near silent gas turbines pulling air from in front of the vehicle and ejecting behind and upward for propulsion and steering. The primary fuel and lifting gas would be stored in tanks and as the hydrogen decreased, the ballast would be diffused in a rainfall type pattern until it ran out then it could be used from the main lifting frame.
Which would be better for use, pure hydrogen, a hydrogen/helium mix or pure helium would be down to engineering and performance.
Because the craft is a large buoyancy supported frame, possibly of an Aluminium Beryllium or Titanium Beryllium alloy with ceramic coated Carbon Fibre skin and modular bags, it could be of great size, streamlined like a stealth fighter design, but giving a cross section of a very small object. For heavier loads you could have a detachable tank lifting body.
If weight/performance was not an acute problem you could even use near silent electric motors and lithium batteries and under wing fans for quick lift.
A lot of the problems with airships is disposing of static difference that an airship can acquire in flight or being just off the ground, but this static electricity can be concentrated to a single place that can be just detached and dropped or made of materials that don’t easily accumulate a charge. Or the grounding is built into the design so that it is gradually leached rather than a single discharge.