This video debunks common misconceptions comparing the Space Shuttle to the Soviet Buran, particularly regarding jet engine capabilities. It traces the historical evolution of the Space Shuttle's design, revealing that early NASA concepts, driven by astronaut preferences and desired operational flexibility, initially included jet engines for both the reusable booster and the orbiter for powered landings, go-arounds, and ferry flights. However, severe budget cuts by the Nixon administration and demands from the Air Force forced significant cost-cutting and design simplifications. Through test programs using lifting bodies (HL-10) and simulated glider approaches (B-52), engineers and pilots concluded that unpowered landings were not only feasible but also simpler and safer than complex powered gliding. Ultimately, the integrated jet engines were designed out of the orbiter in favor of its role as a glider, with cross-country transport handled by specialized Shuttle Carrier Aircraft (modified 747s), proving that "sometimes the best part is no part."
Summary of "How the Space Shuttle Lost Its Jet Engines"
0:06 Dispelling Myths: The video addresses the common misconception that the Soviet Buran was superior to the Space Shuttle due to its jet engines, highlighting that early Space Shuttle concepts also included jet engines, but these were later removed due to various factors.
0:49 Early Concepts with Jet Engines: Initial Space Shuttle designs from the late 1960s to early 1970s proposed both a fully reusable winged booster and the orbiter having jet engines. These engines would allow for powered landings, go-arounds in emergencies, and ferry flights back to launch sites, similar to modern SpaceX Starship concepts.
2:36 Astronaut Influence: Astronauts, largely influenced by Deke Slayton, initially advocated for powered landings with jet engines. However, experienced X-Plane pilots, including Neil Armstrong, demonstrated the feasibility of unpowered landings in challenging aircraft like the F-104 Starfighter.
4:30 Budget Cuts Force Simplification: Severe budget cuts (over 75%) by the Nixon administration significantly curtailed NASA's ambitions, forcing a focus on cost reduction for the Space Shuttle program. The Air Force's involvement, while providing critical support, also necessitated design changes like a larger payload bay.
5:35 Booster Redesign and Engine Limitations: Plans for complex, crewed, reusable boosters with jet engines were replaced by the simpler Solid Rocket Boosters (SRBs) and external fuel tank. Simultaneously, engineers realized the proposed orbiter jet engines weren't powerful enough for true powered flight after re-entry.
6:22 HL-10 Testing and Pilot Feedback: Tests with the HL-10 lifting body using rocket engines showed that shallower, powered glides were paradoxically harder for pilots to control and offered less advantage than pure gliding, especially considering potential engine failures. The conclusion was to design for unpowered landings, reserving engines only for go-arounds.
8:18 B-52 Glider Simulations: To simulate shuttle-sized unpowered landings, B-52 bombers were flown with gear extended, air brakes deployed, and most engines idled, demonstrating the feasibility of gliding a large aircraft to a precise touchdown.
9:05 Engines Persist in Design (Initially): Even after these tests, the 1972 Rockwell Space Shuttle contract still included provisions for orbiter jet engines (e.g., Northrup Grumman's design with a shorter payload bay).
10:06 Air Force Requirements and Ferry Engines: The Air Force's demand for a larger payload bay (40,000 lbs vs. NASA's 25,000 lbs) pushed for the removal of integrated engines, which consumed valuable space and mass. External, bolt-on ferry engines were considered until 1974 but were deemed impractical due to the shuttle's poor lift-to-drag ratio, requiring air-to-air refueling for long-distance transport.
11:51 The Shuttle Carrier Aircraft Solution: The most practical and cost-effective solution was to use existing large aircraft, such as modified 747s (Shuttle Carrier Aircraft), to transport the orbiter. This "piggyback" configuration required minimal airframe changes and was easier to develop and certify than integrated or bolt-on propulsion systems.
13:13 Final Outcome: The Space Shuttle ultimately lost its jet engines, embracing its role as a high-performance glider, with the 747 SCA fulfilling its transport needs and even assisting with landing tests.