The second stage failed to achieve the minimal performance necessary to maintain Earth orbit, and the spacecraft re-entered the atmosphere and burned up.

Below the package at the bottom of the sphere was the separation device, a spring loaded tube with a timer designed to push the satellite away from the third stage after orbit was reached.

Four 76 cm (30 in) spring-loaded metal rods were folded along the equator of the sphere and would protrude radially outward when deployed, acting as a turnstile antenna.

[1] An initial launch attempt on 17 September miscarried when a pad umbilical detached prematurely, causing first stage engine shutdown after one inch of vehicle rise.

It settled back onto the launcher, but fortunately no damage resulted and Vanguard SLV-3 launched successfully on 26 September 1958 at 15:38 GMT.

They completed one orbit and reached a peak altitude of 426 km (265 mi) before reentering over Central Africa.

Investigation concluded that particles from a rubber helium fill hose had clogged a filter in the fuel feed system, resulting in the second stage engine being fuel-starved and operating at only 80% thrust.

[3][4][5][6][7] Vanguard SLV-3 was launched from the Atlantic Missile Range in Cape Canaveral, Florida, on 26 September 1958 at 15:38 GMT.

The poor performance of the second stage was concluded to be a result of low fuel flow rate due to contamination from Buna-N rubber particles from the helium fill hose.