The Perseus design effort struggled along on skimpy funds until 1991, when NASA was conducting a "High Speed Research Program" to evaluate designs for a future supersonic transport, and needed to learn more about the possible environmental impact of such an aircraft on the upper atmosphere. Funds became available to procure a few aircraft.
The Perseus design effort struggled financially until 1991, when NASA launched a program to study supersonic transport designs and their environmental effects on the upper atmosphere. This led to funding for a limited number of aircraft.