Orbital airship

From Wikipedia, the free encyclopedia
Jump to: navigation, search
Main article: Airship
"Space blimp" redirects here. For airships used in a role similar to satellites, see stratospheric airship.

The orbital airship, also called the space blimp, is a proposed space transportation system that carries payloads to and from low Earth orbit. It is intended to achieve orbital altitude and orbital velocity using low thrust rocket propulsion by flying in the manner of an airship rather than a rocket, employing buoyancy and aerodynamic lift rather than vertical thrust to sustain flight during its ascent.[1]

JP Aerospace’s Airship To Orbit[edit]

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 43 kilometers above the ground – roughly the maximum altitude a conventional airship can achieve. At this altitude the second component, a floating 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 (i.e., it accelerates itself horizontally to orbital velocity and gains an altitude in excess of 100 km) over several days.[2][3]

Their program sponsors and business revenues have continued to cover their development costs thus far.[4][5][6] They funded part of their operation until 2005 with a contract for development of military communication and surveillance airships designed to hover over battlefields at altitudes too high for conventional anti-aircraft systems. They had hoped to fly a prototype in 2005, but the vehicle was damaged during testing and the contract was discontinued.[7] Other vehicles are still under development, and JP aerospace has subsequently flown several aerostats as testbeds for ATO hardware and techniques.[8][9]

Multiple vehicles are needed because any airship made strong enough to survive the relatively turbulent lower atmosphere would be too heavy to lift payloads to space. An orbital airship would need to be built larger to improve its buoyancy-to-weight 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.

Both the conventional and orbital airships will be V-shaped for aerodynamics. The orbital airship wings will be shaped to function as hypersonic airfoils and can be angled upwards to help generate lift. As the airship gains altitude, drag will reduce, allowing the vehicle to accelerate with increasing altitude. According to JP Aerospace, there is a wide margin of drag-to-power ratios within which an orbital airship can attain orbit.[10]

Early development 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. The final version of the orbital ascender can also employ refractory materials on the wing leading edge to reduce thermal wear. JP Aerospace’s US patent #7614586 identifies the orbital ascender’s propulsion system as chemical and/or electric rockets. John Powell’s Floating to Space cites several candidate propulsion systems. JP Aerospace is currently developing a hybrid chemical/electric rocket engine.

Their estimated marginal costs for cargo are one dollar per ton per mile of altitude, as quoted to Dr. Jerry Pournelle at the 2004 Space Access Conference[11]

Similar proposals[edit]

Use of large balloons for aerobraking has been previously proposed by aerospace researchers [12] or featured in works of science fiction.

Other groups in addition to JP Aerospace have recently claimed to be researching or actively developing alternative orbital airship designs.[13][14]

JP Aerospace has also acknowledged competition from other organizations in its suborbital applications.

Potential problems[edit]

A practical orbital airship design must deal with multiple engineering challenges of both high altitude balloons and spacecraft.

It should be mentioned that although unmanned weather balloons often reach heights up to 40 kilometres (25 miles), the altitude record for balloons is actually at 53 kilometres (33 miles).[15]

Buoyancy[edit]

One potential limitation is the weight of the material used to contain the airship's gas. For example, air density at 51 km in the mesosphere is estimated at 0.00086 kg per cubic meter according to the International Standard Atmosphere model. To be lighter than air at this altitude, the airship's total density – the weight of its gas plus its cargo and structure divided by its total volume – must be less than 0.00086 kg per cubic meter. This should be achievable with hydrogen, helium, and/or with heated gas inside the balloon, and/or with partially rigid supports. For comparison, the ISAS BU60-1 scientific balloon, holder of the world altitude record for an unmanned balloon as of 2009, flew to 53.0 km. With an inflated mass of 39.77 kg and a maximum volume of 60,000 cubic meters, the total density of BU60-1 was 0.00066 kg per cubic meter.[16]

It will be necessary for all ATO system components to achieve comparably low total density while still transferring sufficient propellant and payload for the orbital ascender to ultimately achieve orbit, or the system components will not have the necessary buoyancy to attain the altitudes stated by JP Aerospace. Additionally, the system components are claimed to be suitable for repeated use.

The square-cube law – common in many engineering calculations – is expected to be critical to the orbital airship design. The material needed to contain a given space increases as the square of its dimensions, while the volume of the space increases as per the cube of its dimensions. In theory one can create a lead zeppelin, or a concrete canoe, or an ironclad ship and have it float if it is of sufficient size, although this may not always be practical.

To achieve significantly higher altitudes, one needs very large volumes and/or very strong materials with low density that are affordable in bulk. Nevertheless, a mesosphere based high altitude platform could offer many potential advantages. One could harvest oxygen and store it for further stages – which might resemble a more conventional launch vehicle. Conditions in the mesosphere are very different from those at lower altitudes in the stratosphere or higher in the thermosphere. Such a platform might also serve as a radio repeater or a relay point while receiving maser or laser energy from the ground.

A mesosphere-based high-altitude platform could also increase its altitude temporarily—in a non-lighter-than-air manner—using energy from ground based or solar sources.

Size[edit]

The final version of JP Aerospace’s first-stage Ascender airship would be the largest airship ever constructed, with an expected volume (57 million cubic feet) greater than seven times that of the Hindenburg. The size of this vehicle would pose unique problems for design, construction, maintenance, deployment and storage.

The other vehicles in JP Aerospace’s proposed architecture are significantly larger, with expected volumes among the largest inflatable structures of any type ever constructed. These vehicles are intended to remain in operation indefinitely (alleviating requirements for deployment and storage), and their operating environments are not predicted to be as structurally demanding as those of the first stage Ascender airship. However, size related problems of design, construction and maintenance will remain.

Other potential problems[edit]

The final design must address several other potential problems.

Additional helium will need to be added to the station and airship to help keep it buoyant. Refueling and resupply of other materials may also be required.

Hypersonic gas dynamics will create high temperature flow across the wings of the orbital ascender, and heat transfer along the wings must be kept low enough to avoid damage.

Regulatory hurdles are expected, beginning during the development phase. The vehicles will potentially traverse the airspace of several nations, and will need to meet legal regulations for flight in every country that they traverse the internationally recognized airspace of.

The orbital ascender faces some of the same harsh environmental conditions as a space elevator, such as elemental oxygen, radiation and space debris.[17]

JP Aerospace believes the problems can be solved, and has already begun tests of the Ascender. They also point out that, if something goes wrong on an airship, there is more time to correct problems than on a rocket.

Potential applications[edit]

JP Aerospace’s Airship to Orbit architecture is three distinct vehicles plus ground control. Thus it would have potential applications beyond those of a direct launch rocket.

The vehicles could support extended research and exploration in the mesosphere and/or thermosphere, which are largely unexplored regions of the atmosphere.

The Dark Sky Station could provide a permanent station for both equipment and personnel. It could function as an outpost or port for space exploration in some of the same ways proposed for space stations – including outposts on other planets with atmospheres – and serve some of the roles filled by orbital satellites today. Possibilities for space tourism and space manufacturing are greatly expanded by the presence of a permanent station. Multiple dark sky stations could support enough living quarters to make residency a viable option.

The orbital airship might provide relatively low cost shipping and transportation, both suborbital and earth-to-orbit. The orbital airship would also be capable of providing orbit-to-earth shipping with equal or greater cargo capacity.

See also[edit]

References[edit]

  1. ^ JPAerospace.com ATO Handout
  2. ^ United States Patent No. 7614586
  3. ^ John M. Powell Floating to Space, Apogee Books, c. 2008, ISBN 978-1-894959-73-5.
  4. ^ JPAerospace.com Sponsors Page
  5. ^ JP Aerospace Press Releases and Related Pictures
  6. ^ Foust, Jeff. “Floating to Space” The Space Review, Tuesday June 1, 2004
  7. ^ Spacefellowship.com Topic – Near Space Maneuvering Vehicle
  8. ^ JPAerospace.com Blog Page
  9. ^ Spacefellowship.com Official JP Aerospace Forum
  10. ^ Boyle, A. “Airship groomed for flight to edge of space” MSNBC.com May 21, 2004
  11. ^ Jerry Pournelle.com Chaos Manor Blog Entry, Dated Friday April 23, 2004
  12. ^ Archimedes Project Website
  13. ^ Spacefellowship.com Topic – Russian ATO Copy
  14. ^ NewMars.com Topic – JP Aerospace – Airship to LEO
  15. ^ http://www.isas.jaxa.jp/e/special/2003/yamagami/
  16. ^ T. Tamagami. “Research on Balloons to Float over 50 km Altitude” JAXA ISAS Special Feature
  17. ^ Space Materials Handbook, Lockheed Missiles and Space Company, c. 1965

External links[edit]