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X-43A Speed Record

 



Seven 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.

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 engine-on 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

Explorer III – Short & Sweet

Fifty-three years ago this week, Explorer III became the third artificial satellite to be successfully orbited by the United States.  Interestingly, this early trio of successful orbital missions had been achieved in a period of less than 60 days.

The early Explorer satellites (Explorer I, II and III) were designated as Explorer A spacecraft.  Their primary mission was to study the Earth’s Magnetosphere.  Each satellite measured about 81-inches in length and had a maximum diameter of 6.5-inches.  On-orbit weight was close to 31 pounds.

Explorer satellite instrumentation was modest.  The primary instruments carried included a cosmic ray detector and micrometeorite erosion gauges.  Data were transmitted to Earth using a 60 milliwatt dipole antenna transmitter and a 10 milliwatt turnstile transmitter.  Electrical power was provided by mercury chemical batteries that accounted for roughly 40 percent of the payload weight.   

Explorer I was the first artificial satellite to achieve Earth orbit.  The satellite was launched atop a Jupiter-C launch vehicle on Friday, 31 January 1958 from LC-26A at Cape Canaveral, Florida.  The country’s first satellite quickly went to work and discovered what we know today as the Van Allen Radiation Belts.

Explorer II was to verify and expand upon the findings of Explorer I.  However, the craft never achieved orbit after it was launched on Wednesday, 05 March 1958.  The cause was attributed to a failure in the 4th stage of its Jupiter-C launch vehicle.  While the outcome was disappointing, the Explorer Program quickly readied another Explorer satellite for flight.

Explorer III was launched from Cape Canaveral’s LC-5 on Wednesday, 26 March 1958 at 17:31 UTC.  The Jupiter-C launch vehicle performed admirably and delivered Explorer III into a highly elliptical 1,511-nm x 100-nm orbit.  However, all was not well in orbit.  Telemetry data indicated that the pencil-like satellite was tumbling at a rate of about 1 cycle every 7 seconds.

Explorer III performed its intended mission in spite of the anomalous tumbling motion.  Indeed, the craft corroborated the findings of Explorer I and helped verify the existence of the Van Allen Radiation belts.  However, the unwanted tumbling increased Explorer III’s aerodynamic drag and significantly shortened its mission lifetime. 

Explorer III’s orbit decayed to the point that it reentered the Earth’s atmosphere on Tuesday, 27 June 1958.  During its 93 days in space, the spacecraft made approximately 1,160 trips around the Earth.

Posted in Aerospace, History

Emergency in Space

Forty-five years ago this week, the crew of Gemini VIII successfully regained control of their tumbling spacecraft following failure of an attitude control thruster.  The incident marked the first life-threatening on-orbit emergency and resulting mission abort in the history of Amercian manned spaceflight.

Gemini VIII was the sixth manned mission of the Gemini Program.  The primary mission objective was to rendezvous and dock with an orbiting Agena Target Vehicle (ATV).  Successful accomplishment of this objective was seen as a vital step in the Nation’s quest for landing men  on the Moon.

The Gemini VIII crew consisted of Command Pilot Neil A. Armstrong and Pilot USAF Major David R. Scott.  Both were space rookies.  To them would go both the honor of achieving the first successful docking in orbit as well as the challenge of dealing with the first life and death space emergency involving an American spacecraft.

Gemini VIII lifted-off from Cape Canaveral’s LC-19 at 16:41:02 UTC on Wednesday, 16 March 1966.  The crew’s job was to chase, rendezvous and then physically dock with an Agena that had been launched 101 minutes earlier.  The Agena successfully achieved orbit and waited for Gemini VIII in a 161-nm circular Earth orbit.

It took just under six (6) hours for Armstrong and Scott to catch-up and rendezvous with the Agena.  The crew then kept station with the target vehicle for a period of about 36 minutes.  Having assured themselves that all was well with the Agena, the world’s first successful docking was achieved at a Gemini mission elasped time of 6 hours and 33 minutes.

Once the reality of the historic docking sank in, a delayed cheer erupted from the NASA and contractor team at Mission Control in Houston, Texas.  Despite the complex orbital mechanics and delicate timing involved, Armstrong and Scott had made it look easy.  Unfortunately, things were about to change with chilling suddeness.

As the Gemini crew maneuvered the Gemini-Agena stack, their instruments indicated that they were in an uncommanded 30-degree roll.  Using the Gemini’s Orbital Attiude and Maneuvering System (OAMS), Armstrong was able to arrest the rolling motion.  However, once he let off the restoring thruster action, the combined vehicle began rolling again.

The crew’s next action was to turn off the Agena’s systems.  The errant motion subsided.  Several minutes elapsed with the control problem seemingly solved.  Suddenly, the  uncommanded motion of the still-docked pair started again.  The crew noticed that the Gemini’s OAMS was down to 30% fuel.  Could the problem be with the Gemini spacecraft and not the Agena?

The crew jettisoned the Agena.  That didn’t help matters.  The Gemini was now tumbling end over end at almost  one revolution per second.  The violent motion made it difficult for the astronauts to focus on the instrument panel.  Worse yet, they were in danger of losing consciousness. 

Left with no other alternative, Armstrong shut down his OAMS and activated the Reentry Control System reaction control system (RCS) in a desperate attempt to stop the dizzying tumble.  The motion began to subside.  Finally, Armstrong was able to bring the spacecraft under control.   

That was the good news.  The bad news for the crew of Gemini VIII was that the rest of the mission would now have to be aborted.  Mission rules dictated that such would be the case if the RCS was activated on-orbit.  There had to be enough fuel left for reentry and Gemini VIII had just enough to get back home safely.

Gemini VIII splashed-down in the Pacific Ocean 4,320 nm east of Okinawa.  Mission elapsed time was 10 hours, 41 minutes and 26 seconds.  Spacecraft and crew were safely recovered by the USS Leonard F. Mason.

In the aftermath of Gemini VIII, it was discovered that OAMS Thruster No. 8 had failed in the ON position.  The probable cause was an electrical short.  In addition, the design of the OAMS was such that even when a thruster was switched off, power could still flow to it.  That design oversight was fixed so that subsequent Gemini missions would not be threatened by a reoccurence of the Gemini VIII anomaly.

Neil Armstrong and David Scott met their goliath in orbit and defeated the beast.  Armstrong received a quality increase for his efforts on Gemini VIII while Scott was promoted to Lieutenant Colonel.  Both men were awared the NASA Exceptional Service Medal.

More significantly, their deft handling of the Gemini VIII emergency elevated both Armstrong and Scott within the ranks of the astronaut corps.  Indeed, each man would ultimately land on the Moon and serve as mission commander in doing so; Neil Armstrong on Apollo 11 and David Scott on Apollo 15.

Posted in Aerospace, History

The First OSO Mission

Forty-nine years ago today, the United States successfully launched Orbiting Solar Observatory No. 1 (OSO-1) into Earth orbit.  This robotic spacecraft provided the first detailed scientific examination of the Sun from space.

The 1960′s was a time of both rapid growth and spectacular achievements in space exploration.  Indeed, weather satellites, communications satellites and surveillance satellites were new inventions.  Robotic space probes were sent to orbit and land on the Moon.  Other autonomous spacecraft visited the inner planets of the Solar System.  Men orbited the Earth.  Still others landed on and returned from the Moon.

Space probes were also employed to good effect in an effort to learn more about our Sun.  NASA’s Orbiting Solar Observatory (OSO) Program was America’s first attempt to acquire detailed solar physics data using orbital spacecraft.  A total of eight (8) OSO space probes were launched into Earth orbit between 1962 and 1975.

The fundamental objective of the OSO Program was to monitor and measure solar electromagnetic radiation levels over an 11-year sun spot cycle.  The idea was to map the direction and intensity of Ultraviolet, X-Ray and Gamma radiation throughout the celestial sphere over the long solar cycle.  Onboard scientific instrumentation included a solar spectrometer, scintillation detector, proton electron analyzer and various flux monitors 

OSO satellites were relatively large and complex for their time.  Spacecraft attitude had to be tightly controlled since onboard instrument systems needed to be continuously trained on the solar disk.  The probe’s solar physics data could be transmitted to ground receiving stations in real-time or recorded on tape for later transmittal.

OSO-1 was the first solar observatory orbited by the United States.  Launch from Cape Canaveral’s LC-17A took place on Wednesday, 07 March 1962 at 16:04:00 UTC.  A Thor-Delta 301/D8 launch vehicle placed the 458-lb OSO-1 satellite into a near circular Earth orbit (291-nm x 275-nm).  The orbital period of 94.7 minutes meant that OSO-1 orbited the Earth 15.2 times each day.

OSO-1 performed well until its second onboard tape recorder gave up the ghost.  This anomaly occurred on Tuesday, 15 May 1962.  The loss of its last functional data recorder meant that all subsequent measurements had to be transmitted in real-time. 

OSO-1 would continue making and transmitting solar physics measurements until May of 1964.  At that time, the spacecraft power supply died when its solar cells failed.  Although dormant, OSO-1 would continue to orbit the Earth for another seventeen (17) years.  The spacecraft reentered the Earth’s atmosphere on Thursday, 08 October 1981.

OSO-1 and all succeeding OSO satellites contributed significantly to progress in the realm of solar physics.  The OSO Program laid the foundation for more sophisticated and detailed study of our Sun through the auspices of such solar probes as SOHO, Ulysses and Skylab.  Indeed, NASA’s Solar Probe Plus probe, currently scheduled to fly within the Sun’s coronal region sometime in the 2015/2016 period, will continue the legacy begun long ago by OSO-1.

Posted in Aerospace, History