Testimony by Dr Robert Zubrin included the following:
"Over the course of its history, NASA has employed two distinct modes of operation. The first prevailed during the period from 1961-1973, and may therefore be called the Apollo Mode. The second, prevailing since 1974, may usefully be called the Shuttle Era Mode (or Shuttle Mode, for short).
In the Apollo Mode, business is conducted as follows: First, a destination for human spaceflight is chosen. Then a plan is developed to achieve this objective. Following this, technologies and designs are developed to implement that plan. These designs are then built, after which the mission is flown.
The Shuttle Mode operates entirely differently. In this mode, technologies and hardware elements are developed in accord with the wishes of various technical communities. These projects are then justified by arguments that they might prove useful at some time in the future when grand flight projects are initiated.
Contrasting these two approaches, we see that the Apollo Mode is destination-driven, while the Shuttle Mode pretends to be technology-driven but is actually constituency-driven. In the Apollo Mode, technology development is done for mission-directed reasons. In the Shuttle Mode, projects are undertaken on behalf of various internal and external technical community pressure groups and then defended using rationales. In the Apollo Mode, the space agency’s efforts are focused and directed. In the Shuttle Mode, NASA’s efforts are random and entropic.
Comparing these two records, it is difficult to avoid the conclusion that NASA’s productivity in both missions accomplished and technology development during its Apollo Mode was at least ten times as great as under the current Shuttle Mode."
H/T to Shlock Vaidya.