The Delta launch vehicle was actually supported, kept alive, and underwent most of its remarkable development under the supervision of NASA's Delta Project Manager, Bill Schindler. NASA's Dan Dembrow remembered:
The Delta launch vehicle was always viewed as an interim launch vehicle in NASA's stable, and was used to retain an intermediate size orbital payload capability until larger launch vehicles were developed. The Delta Project Manager at NASA, Bill Schindler, had a knack for keeping the program alive. He would participate in the launch vehicle assignment process, and when he feared that Headquarters was about to kill the Delta on the grounds that a new mission exceeded its capabilities, he would assure them that Delta could do the job. Then he would challenge his technical staff, and often with the aid of the prime contractor, McDonnell Douglas, and our Goddard technical staff, to figure out a way to extend the flight envelope. This process occurred many times and it was extremely difficult as production launch vehicles are not meant to undergo such constant changes in design. Delta payloads grew from about 200 lbm in low earth orbit in 1960 to about 4100 lbm in geosynchronous orbit by 1990.
In the 1960's, Goddard contracted directly for many of the components (including the second stage from Aerojet), and supplied them to McDonnell Douglas as government furnished equipment (GFE). During this period, Schindler oversold what Delta could do, and each successive payload had us in a quandary. Aerojet was always ready to test changes that would increase the second stage total impulse, and did so frequently. In one such case, a special test was required, and Aerojet went to a lot of trouble to upgrade the test stand for display to NASA management. Among the improvements was a new fail-safe system, and they even went to the point of repainting the bay. At the scheduled date the NASA managers had a schedule conflict, so I was the only NASA observer.
The test took place as scheduled, the instrumentation performed flawlessly, the test values were all nominal, and suddenly the test ended unexpectedly in mid-duration. Nothing within the control room showed anything wrong. When we went out into the test bay, the newly painted walls were on fire. The heat from the fire must have damaged some wiring in the fail-safe system, which promptly terminated the firing.
Aerojet did not realize the critical nature of the test, and this failure almost inadvertently killed the Delta program. Fortunately I was the only NASA observer, and a re-test was successfully concluded within a few days, so Schindler by that time was able to persuade NASA management that all was well. The critical decision was made to fly the mission on Delta.