SEDS -1

Small Expendable Deployer System

SEDS-1 was launched from Cape Canaveral Air Force Station as a Delta/GPS secondary payload on March 29, 1993. An hour after launch a spring loaded Marman clamp ejected a 26 kg payload downward at 1.6 m/s. This impulse was sufficient to allow deployment of enough tether for gravity gradient effects to take over and guarantee the remainder of deployment. Once into this regime, the tether paid off the end of a fixed spool inside the deployer at an increasing rate. Passive effects caused a smooth rise in tension as the tether unwound faster and faster from a shrinking package. Finally, when 1 km of tether remained, active braking was applied by wrapping the tether around the "barber pole" brake. This increases the tension by 10% for each 30° of wrap.

Unlike the later SEDS-2, the braking was open-loop. It reduced the deployment rate by only 50%. This resulted in a series of gentle "bungee" bouncees at the end of deployment. The tether swung to the vertical and was cut 1 orbit after the start of deployment. This slung the payload and tether from Guam onto a reentry trajectory off the coast of Mexico. Pre-flight simulations had indicated that bouncing would have little effect on the reentry location, and the reentry was accurate enough that a pre-positioned observer was able to videotape the payload re-entry and burnup. The last data collected from the payload before reentry showed a predicted tension rise as drag began to blow the tether back and turn it into a kite tail.

SEDS Deployer Can and Winding.

Installing SEDS Deployer on the Delta Launch Vehicle.

SEDS Team