A BALLOON FOR SPACE TRAVEL

A SPACE VEHICLE FOR BOTH MANNED AND UNMANNED SPACE TRAVEL Ian MacDougall A possible future for space exploration and journeys. I assume here that there will be future scientific and economic reasons for travel to become routine between the Earth and the Moon and International Space Station; perhaps also to Mars, hardly likely at all to Venus and Mercury, and very little by comparison to the outer planets, though their moons may be a different story. Travel beyond the solar system for crewed space vehicles is highly improbable IMHO, and even within the solar system would appear to present enormous logistical, support and supply problems. Ever since Yuri Gagarin’s first 1961 manned spaceflight, the only way to access space anyone appears to have considered has been via expensive, multi-stage, powerful and single-use rockets. What is proposed below is a radically different approach. An aircraft carrier sits at the top of the hydrosphere and is used as a base for travel to and from the atmosphere. In a similar way, a balloon of whatever size could be used as a base in the atmosphere for travel beyond the atmosphere; likewise for journeys to and from the space shuttle. This system could first of all be modelled at whatever scale. Imagine a spherical balloon of whatever diameter. A prototype could be a fabric (say of fibreglass or carbon-fibre) sphere rendered gas-tight and coated with a thin layer of duralumin and filled with a hydrogen-helium mixture. As the biggest danger likely is a puncturing of the balloon with space particles, its structure would need to be spongy and self-sealing; a collection of an optimum number of separately inflatable ‘cells’ inside the balloon perhaps. The Gas Bag (GB) cells would be filled with a low density gas, say a hydrogen-helium mixture (remembering always the Hindenburg disaster.) Below the spherical GB would be a gondola, containing crew accommodation, supplies, fuel reserves etc. The gondola would be suspended below the GB in the conventional fashion. Below the gondola would be mounted four rocket engines, or alternatively, ion engines for maximum payload /propulsion and fuel mass /propulsion ratios; for both lift and steering, and pointing always away from the gas sphere. Travel to and from the balloon would be by helicopter, which would land on top of the GB. Crew would access the gondola from the top of the balloon via a tube, internal or external, connecting to the gondola. At its parking altitude, the gondola would be effectively weightless, its weight being balanced by the upthrust force on the GB. So the whole assemblage would rarely have to return to the Earth’s surface once launched and/or assembled at parking altitude. The volume of a sphere is proportional to the cube of its radius, (Vsphere = 4/3πr3) while its surface area is proportional to the square of that same radius. (Sasphere = 4πr2) So we get more lift per unit area of balloon the larger the balloon is. (We could start with something small: say an experimental model 1 metre in diameter, or whatever multiple of that, and proceed from there.) Ascent/descent in the atmosphere could be controlled by pumping the low density gas from the high-volume, low-pressure GB into a low-volume high pressure reserve tank or tanks. At all times, the pressure inside the balloon would have to be higher than the external air-pressure, and at whatever altitude. This would be necessary to prevent the balloon from collapsing. The envisaged balloon need be launched only once in its working lifetime. From then on until the day it was decommissioned, it could be permanently parked away from air traffic lanes and at whatever parking altitude; perhaps in the still air at the centre of the circumpolar wind over the South Pole. On an outward journey, the whole spacecraft would move in the same initial direction as Earth’s rotation; rising vertically at first then, steered by its rockets below the gondola, moving out of the vertical towards the horizontal, but finishing at an exit path angle of 45 degrees to the horizontal. The permanently still air of the South Geographic Pole would appear ideal, and once in the still upper atmosphere, the balloon could move elsewhere as a component of the Earth’s atmosphere. Before lift-off from wherever, the balloon assemblage would have to be kept at minimum gas pressure and tethered at a suitable location. It would be readied for flight by being topped-up with low density gas; transferred into the GB from high-pressure storage beneath the gondola. The balloon assemblage would lift off by simple flotation. Hours, possibly days, could be taken for both ascent and descent. Firing of the rockets to assist lift and steering could take place once a suitable altitude was reached. As the outside air thinned and cooled, adjustments would be made accordingly to the GB reserve balance. As the balloon gained altitude, the rockets would gradually turn its ascent path out of vertical towards horizontal, putting the balloon into something approaching orbit, and at whatever speed. On the outward journey, the balloon would move in the direction of the earth’s rotation, and at a tangent to it. As external air density drops, so does air resistance. Less pressure is required to keep the GB inflated, so lifting gas can be pumped from the GB into the reserve tanks. The sub-gondola rockets would achieve maximum lift coupled with maximum horizontal velocity at 45 degrees to the vertical: a simple vector diagram, neglecting high-altitude weather as a factor. As external air pressure and resistance diminishes, so does balloon buoyancy. The balloon’s speed can rise and approach a tangential velocity, while using air resistance to create lift; in much the same manner as the inertia of the ocean lifts a speedboat out of the water. The balloon lifts to its peak flotation altitude, by definition the altitude where air density is too low to support it any further. At this stage, it will have reached maximum expansion. Lift gas would be conserved by being pumped from GB to reserve tank or vice-versa as required or not required. From the top of the atmosphere (TOA) onwards, lift has to be by rocket propulsion through increasing orbital radii. But as air resistance declined, so the bulk of the gas would be transferred to the storage tanks. Finally, the GB would be filled with just enough lifting gas to keep it inflated for the whole journey to whatever atmosphere-free destination. (Every time a spacecraft has returned in a fiery blaze through Earth’s atmosphere, it has been testimony to that same atmosphere’s lifting power.) On the return journey, the craft approaches Earth opposite to Earth’s rotation. So the balloon starts to act like a parachute, slowing its approach and swinging its direction from horizontal to approaching vertical. Lift gas is steadily pumped from the reserve tanks to the GB, inflating the GB and making it more like a parachute. As it approaches the top of the atmosphere however defined, the balloon turns towards horizontal in a direction opposite to the earth’s rotation. There is a slowing effect of the air resistance in the opposite-Earth-rotation motion, which can take however long is necessary and be combined with rockets firing to retard the whole assemblage. In the last stage of descent, the whole spacecraft comes back to its parking altitude, one or more helicopters land on its upper surface, and the crew goes through a procedure the reverse of lift-off. Alternatively, it can descend all the way to the Earth’s surface and park at some suitable location where the air is still, such as at the South Geographic Pole. The ideal initial launch site would likely be as close as possible to that South Geographic Pole, which is in still air and at 2,835 m altitude; the Antarctic Continent at the Pole being at around sea level. The balloon could possibly be permanently ‘parked’ above Antarctica. Because the balloon spacecraft would be 100% re-usable, and is using minimum fuel to counter gravity in lift-off, there should be considerable savings over use of massive single-use rockets to get to the top of the atmosphere; or for that matter a conventional aircraft used as a launch platform, as recently happened in South Australia. Rockets are used to launch space vehicles because historically, they were first built for Cold War military purposes. NASA’s space programs piggy-backed on military programs. END