Small SRA for a missile
All SRA’s that we design and supply for missiles have in common that they must not take up much space, they must not have much mass, they will be subject to enormous accelerations on launch and then possibly large manoeuvring accelerations. The SRA is likely to be subject to substantial vibration in flight so the issue of the resonant frequency of the component parts of the SRA is important if electrical signal noise is to be kept within specification. They may be in storage in missiles for years without testing or maintenance.
This example shown is a cylindrical SRA- this sort of design has been chosen because of the space envelope available to our customer. Some other Pandect missile SRA designs are pancake types.
Some missile SRA designs may have to run only for seconds- others may be operational for hours on each of many missions.
An SRA may be in a missile that is left on a sunny runway for hours before being fitted to an aircraft and then it may fly to a great altitude. So in a short time it may go through extremes of temperature change and one consequence of this may be the creation of condensation. Similarly with a diving missile on engagement.
One of the reasons why lubricants are used between SRA brushes and rotors, apart from wear, is to help to reduce signal electrical noise. Another reason for lubrication is to reduce “microcuts” where for a very short period the resistance of the signal path is infinite. Sometimes it is not possible to have any sort of lubricant between an SRA brush and its rotor in order to avoid the slightest possibility of contamination of what else is inside the missile. So designs without lubricants have particular challenges. Where lubricants are acceptable the effects of the very low temperatures on them at great altitudes need great attention.
The electromagnetic emissions of an SRA in a missile need to be very low indeed.
For more information please visit the Missile Guidance section of our website.