Apogee Engine Valve Development

Competitiveness & Growth

Status

Ongoing
Status date

2013-05-17

Objectives

The aim of this program was to develop a product which will be suitable for use with monopropellant thrusters with thrust levels of up to 200N (ex: Ariane 5 SCA thruster valves) and bipropellant thrusters up to 650N (ex: LEROS engine range).

Challenges

The following issues were identified at the outset of the program:

The initial design parameters that would be critical to the operation:

Flexure fatigue
Internal leakage
Seal swell

An element test campaign was designed to address these items.

Some items are difficult to calculate so the first built hardware needed to check:

Valve response
MON flow tests over a range of temperatures

For the qualification phase 1 key parameter needed to be mastered:

Cleanliness, generating a production process that would meet the spacecraft cleanliness requirements.

Benefits

The valve developed has the following benefits:

Low pressure drop of 1.1Bar at a flow-rate of 95g/s water
Exceptional flow coefficient stability with MON-3 across a wide temperature range
Internal heater built into the sleeve. An internal heater is a big improvement as external heaters are difficult to attach and are frequently damaged during engine and spacecraft integration.

Features

The Apogee Engine Valve design is a solenoid operated flow control valve with a single seat, dual coil, normally closed, non-sliding fit configuration. The valve has redundant coils located in tandem. The wetted area body is manufactured from Stainless Steel with 'soft-iron' being used in non-wetted areas for magnetic field enhancement.

The unit comprises a fixed pole and a suspended, flat-faced moving pole, within which is housed the PTFE seal feature of the valve. A fully welded structure ensures sealing of the valve to atmosphere. The valve is normally closed and is opened by energizing either of the two coils. The valve closes when current is removed from the energizing coil, under the influence of the coil spring. The fluid pressure force will again become active and together with the spring, ensure a leak tight seal. The spring is sized such that it is effective in sealing across all inlet pressures.

The solenoid actuator of the valve has two independent, fully redundant coils. The valve and solenoid actuator have no sliding fits and are designed not to generate debris during operation. The inlet interface incorporates a particle filter, welded into the inlet. The coil sleeve of the valve contains an internal heater rated to 2W which is potted in with the two actuator coils.

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