Aluminium Liner without weld seams

Helium Xenon has been gaining importance in the Space industry due to its use as propellant in electric propulsion thrusters which, due to their very high specific impulse, are often used in satellites. The storage of Xenon is complex due to the extremely high performance requirements, especially in mass, due to the fact that each additional kg of storage mass costs over €30,000 to put into orbit. Being a gas at ambient temperature and pressure its density is modest requiring substantial pressure application (150bar) to produce good storage performance. On the subject of gases stored at very high pressures ESA also needs to store Helium, usually at over 300bar, to act as a pressurant (for MMH and N2O4).

Aluliner is an alternative solution to currently in‐use gas storage tanks which, through an ingenious concept for gas entrapment, can deliver the performance required by this demanding industry. The gas is stored in highly pressurized spheres, which are then placed in larger tanks (operating at intermediate pressures) whose shape constraints are much less stringent than those of currently existing tanks. The conceptual advantages are obvious: avoiding the Xenon pressure regulator, higher flux rates between tanks and thrusters and an easier and cheaper manufacturing.

This concept can also be employed in Terrestrial mobility solutions, namely for storage of Compressed Natural Gas, on which many of the urban buses, used throughout various capital cities of Europe, run.

Applications:

       •Ionic and Chemical Propulsion;
       •Cold Gas Thrusters;
       •CNG Passenger Cars and Buses.

Innovative Liner

Production

The need to increase the competitiveness of European tanks and provide products that maximize the propellant capacity whilst minimizing the mass and recurrent cost, has urged ESA to substitute the current techniques of forging and machining thick metal shells, plagued with huge costs from tooling suited to only one size of component, high amounts of expensive waste material, and very long lead development and production time.

In the search for new liner manufacturing techniques, that are more flexible and do away with the need for specific sets of tooling, Omnidea, together with IST, studied the feasibility of adapting one of the manufacturing phases of the Aluliner concept to dedicated liner production. Omnidea’s revolutionary forming process, developed over the last 6 years, delivers the possibility of manufacturing spherical or cylindrical tanks without the traditional girth welds, hence enabling the use of aviation grade Al7075 as a liner material which, costing 10 times less than titanium, significantly reduces both the amount and cost of the waste produced, while simultaneously reducing the procurement time for the material. Also, due to the specific nature of the forming process, liner production is substantially hastened, with the bulk of tank being manufactured in a single operation, should seamless welded tube be available.

Applications:

       •Metallic Liner Tank Manufacture
               Propellant Tanks for satellites
                Autogas (LPG) tanks

       •Liner production for COPV (Composite Overwrapped Pressure Vessels)
               Pressurant Vessels manufacture for satellites
                On-board storage of H2 at 700bar

Product Features

 Intrinsic

       •No welds on the tank shell (elimination of potential failure points, cheaper and faster production);
       •Integral neck to attach interface parts or fittings.

Optional

       •Custom thickness distribution (with maximum-to-minimum thickness ratio up to 3 or more, with machining);
       •External machining for a more accurate geometry is possible;
       •Integral neck may be complemented or replaced by crimped fittings, if required;
       •Chemical passivation, anodizing and surface treatments are possible.

Future Development

In 2012 Omnidea was asked by a Space industry customer to produce a set of 120 mm aluminium pressure vessels (for N2, with 40 bar MEOP) for a ground testing jig. In order to achieve this Omnidea, adapted what was by then its current capability to the customer's needs. Currently, the target of our research effort is the production of a 70 litre aluminium liner for a xenon tank intended for electric ion propulsion systems in satellites. This liner is to be used in a COPV, with the whole system scheduled for qualification. The pursuit of this capability has been done in stages, with each stage comprising production of tanks with ever growing dimensions. As each stage is validated, Omnidea retains the production capability for tanks of that diameter.


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Portfolio using weld-less seams technology
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Aluminium weld-less tanks
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Cold forming tool process
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Finished tanks
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Finished tank before paint
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Cold forming tool