Taking another step towards her debut flight, Vega’s P80 motor is schedule for a static firing on the same test pad a the Guiana Space Centre, Kourou, French Guiana, that evaluated the solid motors which power the Ariane 5 launch vehicle.
While NASA test their ATK Solid Rocket Motors at the test range in Utah – as recently seen with the night firing on one SRB – ESA (European Space Agency) will test fire their P80 on the test stand, with large blades would cutting the envelope open, allowing the solid propellant to burn freely without providing any thrust.
The test will last about 100 seconds, with the motor delivering some 200 tonnes of average thrust.
ELV SpA (Italy) is the lead manufacturer of the vehicle, which is designed to carry payloads in the range 300 kg to 2.5 tonnes into low Earth orbits. The typical reference for Vega’s launch capacity is to carry 1500 kg to a 700 km-altitude polar orbit.
The P80’s propellant load was cast some six kilometres from the BEAP test stand, at the Guiana Propellant Plant (UPG) where the EAP’s – the solids for the Ariane 5 – lower segments are also loaded.
‘The propellant is not exactly the same as on the EAP’s,’ explained Stefano Bianchi, Vega Programme Manager at ESA. ‘We adapted the propellant mix and the granulometry to increase its performance and density.’
As for the EAP segments, once the propellant’s polymer binder had solidified, the mandrel forming the exhaust canal for hot gases was extracted and the motor underwent numerous inspections to make sure that no bubbles or cracks had formed inside the binder. In a solid motor, these kinds of defects could have explosive consequences. After inspection, the motor was prepared for its test firing.
The P80 is not simply the new motor developed for the first stage of ESA’s Vega small launch vehicle. It is a multidisciplinary demonstrator to validate advanced technologies which could later be applied to Ariane 5’s boosters.
The most obvious change is to the booster casing. It is made of filament wound graphite epoxy, a technology largely used on smaller motors for civilian launchers as well as ballistic missiles. Much lighter than the stainless steel currently used on Ariane boosters, it provides a dramatic increase in payload capacity.
Other improvements in the motor include a new design of igniter with a simplified architecture, also using a carbon-fibre case.
The P80 nozzle looks like a shorter version of the EAP nozzle but its design was revised to achieve more simplicity, incorporate fewer elements, and reduce production costs. New thermal insulation material and a narrower throat improve the expansion ratio and overall performance. The new type of flexible joint makes it a lot easier to steer and has allowed the replacement of heavy hydraulic actuators by much lighter electromechanical ones for thrust vector control.
‘There are lots of challenges on this test,’ says Stefano Bianchi. ‘As on every maiden firing, there is also a lot to learn.’
After the 30 November test, it is planned that each of the three motors will undergo an additional static test before the maiden flight of the Vega launcher, which will complement Ariane 5 and Soyuz in the small satellite segment of the launch market.