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America’s Space Twins

Fifty-five years ago this week, Gemini III was launched into Earth orbit with astronauts Vigil I. “Gus” Grissom and John W. Young onboard. The 3-orbit mission marked the first time that the United States flew a multi-man spacecraft.

Project Mercury was America’s first manned spaceflight series. Project Apollo would ultimately land men on the Moon and return them safely to the Earth. In between these historic spaceflight efforts would be Project Gemini.

The purpose of Project Gemini was to develop and flight-prove a myriad of technologies required to get to the Moon. Those technologies included spacecraft power systems, rendezvous and docking, orbital maneuvering, long duration spaceflight and extravehicular activity.

The Gemini spacecraft weighed 8,500 pounds at lift-off and measured 18.6 feet in length. Gemini consisted of a reentry module (RM), an adapter module (AM) and an equipment module (EM).

The crew occupied the RM which also contained navigation, communication, telemetry, electrical and reentry reaction control systems. The AM contained maneuver thrusters and the de-boost rocket system. The EM included the spacecraft orbit attitude control thrusters and the fuel cell system. Both the AM and EM were used in orbit only and discarded prior to entry.

Gemini-Titan III (GT-3) lifted-off at 14:24 UTC from LC-19 at Cape Canaveral, Florida on Tuesday, 23 March 1965. The two-stage Titan II launch vehicle placed Gemini 3 into a 121 nautical mile x 87 nautical mile elliptical orbit.

Gemini 3’s primary objective was to put the maneuverable Gemini spacecraft through its paces. While in orbit, Grissom and Young fired thrusters to change the shape of their orbital flight path, shift their orbital plane, and dip down to a lower altitude. Gemini 3 was also the first time that a manned spacecraft used aerodynamic lift to change its entry flight path.

As spacecraft commander, Gus Grissom named his cosmic chariot The Molly Brown in reference to a then-popular Broadway show; “The Unsinkable Molly Brown”. Grissom chose the moniker in memory of his first spaceflight experience wherein his Liberty Bell 7 Mercury spacecraft sunk in almost 17,000 feet of water during post-splashdown operations.

At almost two (2) hours into the mission, pilot John Young presented Grissom with his favorite sandwich which had been smuggled onboard. Grissom and Young took a bite of the corned beef sandwich and put it away since loose crumbs could get into spacecraft electronics with catastrophic results. Not amused, NASA management reprimanded the crew after the mission.

Gemini 3 splashed-down in the Atlantic Ocean at 19:16:31 UTC following a 3 orbit mission. The spacecraft landed 45 nautical miles short of the intended splashdown point due to a mis-prediction of aerodynamic lift. Although hot and sea-sick, Commander Grissom refused to open the spacecraft hatches until the recovery ship USS Intrepid came on station.

Nine (9) additional Gemini space missions would follow the flight of Gemini 3. Indeed, the historical record shows that the Gemini Program would fly an average of every two (2) months by the time Gemini XII landed in December 1966. During that period, the United States would take the lead in the race to the Moon that it would never relinquish.

Posted in Aerospace, History

Remembering HYPER-X Flight 2

Sixteen years ago this week, the NASA X-43A scramjet-powered flight research vehicle reached a record speed of over 4,600 mph (Mach 6.83). The test marked the first time in the annals of aviation that a flight-scale scramjet accelerated an aircraft in the hypersonic Mach number regime.

NASA initiated a technology demonstration program known as HYPER-X in 1996. The fundamental goal of the HYPER-X Program was to successfully demonstrate sustained supersonic combustion and thrust production of a flight-scale scramjet propulsion system at speeds up to Mach 10. The term scramjet stands for Supersonic Combustion RAMJET.

The scramjet is a key to sustained hypersonic flight within the earth’s atmosphere. Whereas rockets are capable of producing large thrust magnitudes, both the duration of operation and the amount of thrust per unit propellant mass is low. In part, this is because a rocket has to carry its own fuel and oxidizer supplies. A scramjet is a much more efficient producer of thrust in that it only has to carry its fuel and uses the atmosphere as its oxidizer source.

Rocket technology is a highly developed discipline with a deep experience and application base. In contradistinction, flight-scale scramjet technology is still in a developmental stage. Considerations such as initiating and sustaining stable combustion is a supersonic stream, efficient conversion of fuel chemical energy to kinetic energy, and optimal integration of the scramjet propulsion system into a hypersonic airframe are among the challenges that face designers.

Also known as the HYPER-X Research Vehicle (HXRV), the X-43A aircraft was a scramjet test bed. The aircraft measured 12 feet in length, 5 feet in width, and weighed nearly 3,000 pounds. The X-43A was boosted to scramjet take-over speeds with a modified Orbital Sciences Pegasus rocket booster.

The combined HXRV-Pegasus stack was referred to as the HYPER-X Launch Vehicle (HXLV). Measuring approximately 50 feet in length, the HXLV weighed slightly more than 41,000 pounds. The HXLV was air-launched from a B-52 mothership. Together, the entire assemblage constituted a 3-stage vehicle.

The second flight of the HYPER-X program took place on Saturday, 27 March 2004. The flight originated from Edwards Air Force Base, California. Using Runway 04, NASA’s venerable B-52B (S/N 52-0008) started its take-off roll at approximately 20:40 UTC. The aircraft then headed for the Pacific Ocean launch point located just west of San Nicholas Island.

At 21:59:58 UTC, the HXLV fell away from the B-52B mothership. Following a 5 second free fall, rocket motor ignition occurred and the HXLV initiated a pull-up to start its climb and acceleration to the test window. It took the HXLV about 90 seconds to reach a speed of slightly over Mach 7.

Following rocket motor burnout and a brief coast period, the HXRV (X-43A) successfully separated from the Pegasus booster at 94,069feet and Mach 6.95. The HXRV scramjet was operative by Mach 6.83. Supersonic combustion and thrust production were successfully achieved. Total power-on flight duration was approximately 11 seconds.

As the X-43A decelerated along its post-burn descent flight path, the aircraft performed a series of data gathering flight maneuvers. A vast quantity of high-quality aerodynamic and flight control system data were acquired for Mach numbers ranging from hypersonic to transonic. Finally, the X-43A impacted the Pacific Ocean at a point about 450 nautical miles due west of its launch location. Total flight time was approximately 15 minutes.

The HYPER-X Program made history that day in late March 2004. Supersonic combustion and thrust production of an airframe-integrated scramjet were achieved for the first time in flight; a goal that dated back to before the X-15 Program. Along the way, the X-43A established a speed record for airbreathing aircraft and earned a Guinness World Record for its efforts.

Posted in Aerospace, History

Final Flight: USAF/Martin XB-51

Sixty-four years ago this month, the lone remaining USAF/Martin XB-51 light attack bomber prototype crashed during take-off from El Paso International Airport in Texas. The cause of the mishap was attributed to premature rotation of the aircraft leading to an unrecoverable stall.

A product of the post-WWII 1940’s, the Martin XB-51 was envisioned as a jet-powered replacement for the piston-driven Douglas A-26 Invader. The swept-wing XB-51 utilized a unique propulsion system which consisted of a trio of General Electric J47 turbojets. Demonstrated top speed was 560 knots at sea level.

The XB-51 was a good-sized airplane. With a length of 85 feet and a wing span of 53 feet, the XB-51 had a nominal take-off weight of around 56,000 lbs. The wings were swept 35 degrees aft and incorporated 6 degrees of anhedral. The latter feature to counter the large dihedral effect produced by the type’s tee-tail.

A pair of XB-51 aircraft were built by Martin for USAF. Ship No. 1 (S/N 46-0685) first took to the air in October of 1949 followed by the flight debut of Ship No. 2 (S/N 46-0686) in April of 1950. The air crew consisted of a pilot who sat underneath a large, clear canopy and a navigator housed within the fuselage.

While the XB-51 flew hundreds of hours in flight test and made many lasting contributions to the aviation field, the aircraft never went into production. This fate was primarily the result of having lost a head-to-head competitive fly-off against the English Electric Canberra B-57A light attack bomber in 1951.

The No. 1 XB-51 aircraft was lost on Sunday, 25 March 1956 during take-off from El Paso International Airport. The mishap aircraft accelerated more slowly than normal and with the end of the runway coming up quickly, the pilot rotated the aircraft in a attempt to get airborne. Unfortunately, the rotation was premature and the wing stalled. The aircraft exploded on impact and the crew of USAF Major James O. Rudolph and Staff-Sargent Wilbur R. Savage were killed.

The loss of the No. 1 XB-51 was preceded by the destruction of Ship No. 2 (S/N 46-0686) on Friday, 09 May 1952. That tragedy occurred during low-altitude aerobatic maneuvers at Edwards Air Force Base in California. The pilot, USAF Major Neil H. Lathrop, perished in the resulting post-impact explosion and inferno.

As a footnote, the XB-51 was never assigned an official nickname by the Air Force. However, it was unofficially referred to in some aviation circles as the Panther. Due to its prominently-long fuselage, the less majestic monicker of “Flying Cigar” was sometimes used as well.

Posted in Aerospace, Final Flight, History