Why heat helium? I don't think heated helium is lighter... I will ask a friend. . I would like to ride in a massive dirigible airship... I think one could be built with a carbon fiber half cradle holding the envelope open from the outside. This would eliminate the need for an internal frame. More 'living' space, lighter weight. . I've heard of new flexible type solar collectors that seem perfect for powering this airship. 15 or 20 knots at a ceiling of 70k sounds like a nice ride.

Yes heated Helium is lighter as it gets warmer. the problem is heating all the helium. (think about a large gymn and how much heat is lost from within and how hard it is to warm it one degree. second is in the deridigible all the air wants to go to the front or back trying to put the blimp on nose or tail. this can be adjusted by putting screens that tend to even out the temperature and keep it central. they do have hot air blimps, tho they seem very unreliable and difficult. a blimp becomes more stable and easier the larger it is because comparatively the amount of MASS that each molecule of wind outside now has to move(not to say its easy). their is a company I believe that is trying to use Heated Helium Plasma to warm the area, reason(science) when a molecule is heated it seperates farther from the next molecule the more heat the farther...so instead of all having to be farther apart one could be extreme and move them away making a larger void beside itself.as well transfering heat to the adjacent helium molecules. so it will continue a stream (like a zippo) of plasma helium that has say 80 ft to the top to cool down by transfussion. next dont forget that helium is only 7% heavier than Hydrogen, reason: Hydrogen by itself is half as light as Helium but Hydrogen wants to bind with another electron and so it very quickly becomes H2 which is 1proton 1neutron 1electron conected with 1 electon 1neuton and 1 electron where Helium is 2Protons 2Neutrons and 2electrons so the only difference is that Hydrogen takes up a little more space per 2 molecules... Nasa did an experiment on Helium Hydrogen mixture and found that you can put about 11% Hydrogen into Helium and with a rupture it will not burn in atmosphere. so no worry about explosions (hindenburg like). your semirigid frame is a fine Idea with a stretchable envelope on top...I have worked that myself since I am an avid Blimp fan, Its downfall is when you decrease pressure or heated pressure the envelope will start to waver and could rip. my thought is have a complete rigid blimp (carbon fiber) and inside have a small balloon of air that can be released to the outside or filled to keep the helium inside at the same pressure but it will increase the lift when the balloon gets smaller and more air is pushed outside and volume of Helium is increased. K hope you write back and I will explain more if you want or clarify...glad to see two other blimp fans...

"The orbital airship, also called the space blimp, is a proposed space transportation system that carries payloads to and from low Earth orbit. In the Airship To Orbit (ATO) design envisioned by JP Aerospace, there are three components. A conventional airship (Ascender) lifts payloads up to 30 to 40 kilometers above the ground - roughly the maximum altitude a conventional airship can achieve. At this altitude the second component, a docking station (Dark Sky Station), acts as a resupply station for the third stage. The third stage is an "orbital airship" (Orbital Ascender), which takes payloads to low earth orbit in three to nine days (i.e., it accelerates itself horizontally to orbital velocity and gains sufficient altitude). Their estimated marginal costs are one dollar per ton per mile of altitude, and their development costs thus far have been under one million dollars. Both the atmospheric and orbital airships will be V-shaped for aerodynamics. However, the orbital airship will be angled upwards to help generate lift. As the airship gains altitude, drag will reduce. According to JP Aerospace, there is a wide margin between the thrust that engines can provide the airship and the amount of drag the airship would experience in the outer fringes of the atmosphere. Early stages of the station and the airships will be powered by fuel cells. In the long term, the surface of these objects can be sprayed with a thin-film solar cell, which, while inefficient in energy conversion, would benefit from light weight, simplicity, and the large surface area. An alternative might use Laser propulsion (Lightcraft) to power the early stages and the airships. A ground based laser or maser could be used to provide energy. Furthermore, a similar system could be used to heat the helium inside the first stage from the ground. This will naturally cause it to expand - the pressure can be released through nossels in the bottom of the craft providing additional lift. Heated helium would allow for lower internal pressures to be achieved while maintaining the overall volume of the gas and its craft (a semi-rigid structure might help). (PV=nRT) This allows for the first stage of the craft to achieve higher altitudes - maintaining "lighter-than-air" equilibria at lower surrounding thin atmosphere densities.[ref-1] The platform could be used to store fuel for the second stage which could resemble more conventional(rocket)(or hybrid) design. It is important to recognize the oxygen represents a large proportion of the mass of a conventional rocket. A large part of the cost of lifting a conventional rocket involves lifting this oxygen. A high altitude platform powered from the ground could be used to HARVEST oxygen from the surrounding low density air over time, condense and store it for the second stage. Oxygen is present at high altitudes - even if it is a very low density. [ref 1] Two stages are needed because any airship made strong enough to survive the atmosphere would be too heavy to lift payloads to space. An orbital airship would need to be built larger to improve the volume/surface area ratio, with thinner walls, and designed to operate at notably lower pressure. Even in the outer fringes of the atmosphere, helium is still lighter than air." Source and further information: http://en.wikipedia.org/wiki/Orbital_airship