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Prelude to Orbit

Fifty-five years ago this month, the first Jupiter-C launch vehicle flew a suborbital mission in which it attained a maximum velocity of 16,000 mph.  The successful flight test was a significant step in the development of what would ultimately result in the United States’ first satellite launcher.

The Jupiter-C was a derivative of the Army’s Redstone Short Range Ballistic Missile (SRBM).  It was designed to test sub-scale models of the warhead reentry vehicle used by the Jupiter Intermediate Range Ballistic Missile (IRBM).  The “C” in Jupiter-C stood for Composite Reentry Test Vehicle.

The Jupiter-C launch vehicle was composed of three (3) separate stages.  The vehicle measured 68.5 feet in length and had a maximum diameter of 70 inches.   Lift-off weight was 62,700 lbs.  All Jupiter-C launches took place from LC-5 and LC-6 at Cape Canaveral, Florida.

The Jupiter-C first stage was a Redstone missile stretched by 8 feet to allow for increased propellant load capability.  Power was provided by a single Rocketdyne A-7 liquid rocket engine that burned alcohol and liquid oxygen as propellants.  The A-7 produced 78,000 lbs of thrust for about 150 seconds.

The Jupiter-C second and third stages consisted of clusters of Baby Sergeant solid rocket motors.  Specifically, the second stage clustered eleven (11) of these motors that generated a total thrust of 16,500 lbs for 6 seconds.  The third stage utilized a cluster of three (3) Baby Sergeants that produced a total thrust of 4,500 lbs for 6 seconds.  Propellants for the solids included polysulfide-aluminum and ammonium perchlorate.

The second and third stage solid rocket motors were housed in a large cylinder that sat atop the first stage.  This cylinder (referred to as the “tub”) was spun at a rotational velocity that varied from 450 to 750 RPM in flight.  The purpose in doing so was to mitigate the effects of thrust misalignments and provide gyroscopic stability during the  firing periods of the second and third stage solid rocket motor clusters.

The kinematic performance capability of the Jupiter-C was such that it could readily put a payload in orbit given a fourth stage.  However, the State Department strictly forbade any attempt to orbit a satellite with the Jupiter-C.  Even if that were to happen “accidentally”.  The philosophy at the time was that America’s first satellite would be orbited using a non-military booster.

The first Jupiter-C was launched from LC-5 at Cape Caneveral, Florida on Wednesday, 19 September 1956.  Launch time was 05:47 UTC.  (For the record, we note here that some historical sources quote the launch date as being Thursday, 20 September 1956.)  The vehicle did not carry a scaled Jupiter nose cone test article, but a dummy fourth stange and about 20 lbs of instruments in its stead.

The kinematic performance of the first Jupiter-C was impressive.  The vehicle reached a speed of 16,000 mph (1,500 mph less than orbital requirement) at third stage burnout.   Impact occurred in the Atlantic Ocean roughly 2,861 nm downrange of the launch site.  Apogee for the suborbital flight was 593 nm.

There were only two more Jupiter-C test flights after the inaugural mission.  These occurred on Wednesday, 15 May 1957 and Thursday, 08 August 1957, respectively.  Each vehicle carried a scaled Jupiter nose cone test article.  Surface temperatures exceeded 2,000 F and the ablative thermal protection system worked remarkably well.  So much was learned from these missions that further Jupiter-C flights were deemed unnecessary.

The addition of a live fourth stage rocket motor to the Jupiter-C was known as Juno I.  Indeed, using a single Baby Sergeant solid rocket motor and a small scientific payload constituted the Explorer I satellite.  History records that Explorer I was orbited by a Juno I launch vehicle on Friday, 31 January 1958.  Significantly, it was the first satellite to be orbited by the United States.

Posted in Aerospace, History

XF-92A Dart First Flight

Sixty-three years ago this week, the USAF/Convair XF-92A Dart made its first official flight from Muroc Army Airfield in California.  Convair test pilot Ellis D. “Sam” Shannon was at the controls of the experimental delta-winged aircraft.

The XF-92A Dart holds the distinction of being the first delta-winged, turbojet-powered aircraft in the United States.  It was designed and produced by the Consolidated Vultee Aircraft (Convair) Company for the United States Army Air Force.  Only one copy of the type (S/N 46-682) was ever built and tested.

At the time, the delta wing planform was something of a novelty.  Convair designers chose this shape principally due to its aerodynamics benefits.  For example, transonic wave drag is significantly lower than that of a swept wing of equal area.  The delta wing also exhibits favorable lift-curve slope, center-of-pressure travel and ground effect characteristics.

The large chord of a delta-winged aircraft allows for static pitch stability to be realized without the use of a classic horizontal tail.  Pitch control is obtained via wing trailing edge-mounted elevons; surfaces which combine the functions of an elevator and the ailerons.  When differentially-deflected, elevons provide roll control.

The XF-92A measured 42.5 feet in length and had a wing span of 31.33 feet.  Empty and gross weight were 9,978 lbs and 14,608 lbs, respectively.  Early in its development, the XF-92A was powered by an Allison J33-A-21 turbojet which generated a maximum thrust of only 4,250 lbs.  The final version of the aircraft was configured with an Allison J33-A-16 turbojet which produced a maximum sea level thrust of 8,400 lbs.

The XF-92A made its maiden flight on Saturday, 18 September 1948 from Muroc Army Airfield, California.  Convair test pilot Ellis D. “Sam” Shannon did the piloting honors.  Although the aircraft handled well, it was a bit over-responsive to control inputs.  In addition, the XF-92A was underpowered.

Convair completed  the last of 47 Phase I test flights on Friday, 26 August 1949.   The Air Force conducted the first Phase II flight test on Thursday, 13 October 1949 with none other than Major Charles E. “Chuck” Yeager at the controls.  Phase II testing was completed on Wednesday, 28 December 1949 by USAF Major Frank K. “Pete” Everest.

Following Phase II testing, the aircraft was re-engined with an Allison J33-A-29 turbojet capable of generating 7,500 lbs of sea level thrust.  The Air Force continued to fly the XF-92A on various and infrequent test missions into February of 1953.  Pilots of historical note who flew the aircraft include Al Boyd, Kit Murray, Jack Ridley, Joe Wolfe and Fred Ascani.  It appears that the Air Force flew a total of 47 flight tests using the XF-92A.

The lone XF-92A was turned over to the National Advisory Committe For Aeronautics (NACA) once the Air Force was done testing it.  The aircraft was promptly configured with an Allison J33-A-16 turbojet that generated 8,400 lbs of sea level thrust.  NACA test pilot A. Scott Crossfield flew the XF-92A a total of 25 times.  The type’s last flight occurred on Wednesday, 14 October 1953.

The XF-92A was not all that great from a piloting standpoint.  Among other things, the aircraft had a severe pitch-up problem which produced normal accelerations between 6 and 8 g’s.  The XF-92A was also plagued with landing gear failure problems.  As noted previously, the aircraft was underpowered; a situation that was not uncommon for jet-powered aircraft of the era.

Inspite of its flaws, the design and flight experience gained from the XF-92A’s development led to an extensive series of delta-winged highly-successful aircraft produced by Convair in the 1950’s.  These historically-significant aircraft include the F-102 Delta Dagger, F-106 Delta Dart, B-58 Hustler, XF2Y Sea Dart and XFY Pogo.

Posted in Aerospace, History

First Successful Live Payload Rocket Flight

Sixty-years ago this month, a live biological payload consisting of a primate and a colony of mice was lofted to an altitude of 236,000 feet by a two-stage Aerobee X-8 sounding rocket.  The mission marked the first recorded instance where a mamallian payload survived the rigors of high altitude rocket flight.

The post-World War II period saw a rapid expansion in America’s efforts to explore space.  Emphasis was placed on flying faster and higher.  Rocket power led the way.  First, into the upper atmosphere, and ultimately into the lower reaches of space.

Early post-war flight research capitalized on using V-2 rockets captured from the defeated Third Reich.  These vehicles were brought to America and adapted to boost instruments to high altitude.  While servicable in this new role, the V-2 was less than ideal from the standpoints of launch, performance and payload recovery.

In light of the above, a variety of purpose-built rocket systems rapidly came into being during the post-war years.  Prominent among these was the Aerobee high altitude sounding rocket.  Aerojet General initiated development of the system in 1946.  The first Aerobee test vehicle was flown in November of 1947 at White Sands proving Grounds (WSPG).

The first Aerobee configuration was about known as the X-8.  It consisted of a solid propellant booster and a liquid sustainer.  The booster generated 18,000 lbs of thrust for 2.5 seconds.  Sustainer propellants included aniline and furfuryl-alcohol (fuel) and red fuming nitric acid (oxidizer).  The sustainer rocket engine produced 2,600 lbs of thrust for 40 seconds.

The X-8 launch vehicle measured 26.4-feet in the length with a launch weight of about 1,100 lbs (including 150-lb payload).  The sustainer stage was a little more than 20-feet in length and 15-inches in diameter.  The launch weight of the booster was roughly 50 lbs more than that of the sustainer.

The X-8 was launched from a 143-foot tower which was typically canted 3-degrees off of the vertical.  Booster burnout occurred at 950 ft/sec and 1,000 feet above the ground.  Sustainer burnout took place at 4,420 ft/sec and an altitude of 17-nm.  Apogee was on the order of 66-nm.

The Aerobee carried a variety of scientific instruments to probe the atmospheric and space environments.  Measurements were made of high altitude thermodynamic properties, winds, radiation and magnetic fields.  The Aerobee Program also provided a wealth of information regarding vehicle aerodynamics, flight dynamics and dispersion.

The Aerobee was also used to loft live biological payloads into near space.  At the time this flight research began in the late 1940’s/early 1950’s, very little was known about the effects of high altitude rocket flight on living organisms.  A variety of small animals were used as test subjects including primates, mice, and insects.  The data obtained from these animal flights were ultimately used to safely launch men into space.

History records that it was not all that easy to rocket animals into space and have them survive the experience.  Animals died either due to the rigors of rocket flight, launch vehicle failure or recovery system malfunction.  Sometimes everything worked, but an animal died due to heat exhaustion when recovery crews could not extract it from the downed payload section soon enough.  It would take over 3-years of flight experience before success was achieved.

The great day came on Thursday, 20 September 1951.  An Aerobee X-8 RTV-A1 served as the launch platform.  The live biological payload consisted of a monkey named Yorick and a colony of eleven (11) mice.  The launch took place at 15:31 UTC from Holloman Air Force Base, New Mexico.  The X-8 carried the monkey and mice payload to an apogee of 236,000 feet.  The parachute recovery system finally worked.  Recovery was also successful.

Many more successful Aerobee animal flights took place in the ensuing years.  Even as Aerobee rocket performance increased significantly as numerous variants of the X-8 were developed over the life of the program.  Indeed, almost 1,100 payloads were lofted into the realms above by the time the Aerobee was taken out of active service in 1985.

Posted in Aerospace, History

Atlas Goes Operational

Fifty-two years ago this week, the United States Air Force successfully conducted an Initial Operational Capability Demonstration (IOC DEMO) of the Atlas D Intercontinental Ballistic Missile (ICBM).  The Atlas Missile System was pronounced operational following the successful launch from Vandenberg Air Force Base, California.

Named for the superhuman strongman of Greek mythology, Atlas was the United States’ first operationally deployed intercontinental ballistic missile (ICBM).  Program roots go back to 1946 when Consolidated Vultee Aircraft (Convair) was awarded a study contract by the United States Army Air Forces for a 1,500 to 5,000 mile range missile that could carry a nuclear warhead.

At the time Convair began its study, no missile within conception could carry even the smallest nuclear warhead available at the time. However, a confluence of technological developments in the early 1950’s led to Atlas becoming a high priority development within the United States defense community.  First, the thermonuclear weapon was successfully demonstrated.  Second, a design breakthrough occurred wherein nuclear warhead mass was sharply reduced.  Finally, CIA activities revealed that the Soviet Union was making significant progress with their own ICBM program.

Atlas A, B and C were the initial test and development variants of America’s first ICBM.  Atlas D was the first operational version.  Configured with a Mark 2 reentry vehicle, it measured 75 feet in length and 10 feet in diameter.  Atlas D weighed 255,000 lbs at launch and had a range of 10,360 miles.

The Atlas propulsion system consisted of a single Rocketdyne LR105 sustainer  (57,000 lbs thrust) and a pair of Rocketdyne LR89 boosters (150,000 lbs thrust each).   Roll control and fine velocity control was provided by a pair of Rocketdyne LR101 vernier rocket engines (1,000 lbs thrust each).

The Atlas sustainer rocket engine was mounted between the outboard booster rocket engines.  This trio of rocket engines was ignited at launch.  While the boosters were jettisoned around 130 seconds into flight, the sustainer core continued to fire until propellant exhaustion.  This unique arrangement made Atlas a stage-and-a-half launch vehicle.

In striving for the minimum weight solution, the Atlas airframe included propellant tankage constructed of very thin stainless steel.  This so-called “balloon tank” design required internal pressurization with nitrogen gas at about 5 psig to provide structural rigidity.  An Atlas launch vehicle would simply collapse under its own weight if not so pressurized.

Atlas A, B, C and D variants employed radio guidance.  That is, the missile sent position information from its guidance system to the ground via radio.  In turn, the ground sent course correction information back to the missile.  Starting with the Atlas E, the guidance system was entirely autonomous.

On Wednesday, 09 September 1959, the Strategic Air Command (SAC) conducted an Initial Operational Capability Demonstration (IOC DEMO) launch  at Vandenberg Air Force Base, California.  The Atlas D 12D launch vehicle lifted-off from Launch Complex 576-A2 at 17:50 UTC.  Its Mark II reentry vehicle flew 4,480 nautical miles downrange and landed less than 1 nautical mile from its target near Wake Island.  Apogee and maximum speed were 972 nautical miles and 16,000 mph, respectively.

The Atlas IOC DEMO mission was entirely successful.  General Thomas D. Power, SAC Commander-in-Chief, was so impressed with the results of the flight that he immediately declared the Atlas System to be operational.

The Atlas missile ultimately stood sentinel at 11 separate launch sites located throughout the United States.  Roughly 350 Atlas missiles were manufactured during the program’s lifetime, with a maximum of 129 missiles being deployed at any one time being 129.  However, the introduction of the famous Minuteman missile in 1963 sounded the death knell for Atlas.  Indeed, there were no more operational Atlas missiles after April of 1965.

Although its operational service life was somewhat brief, Atlas provided a proving ground for a multiplicity of emerging missile technologies. Further, Atlas development served as the organizational and procedural template for all future ICBM programs.

Following retirement from active ICBM service, depostured Atlas ICBM’s were converted to the space launch role.  It was employed for nearly a quarter of a century in such capacity.  Indeed, all Mercury Earth-orbital missions were launched using man-rated Atlas launch vehicles.

The Atlas is still active in the US launch vehicle inventory.  Although now manufactured by Lockeed-Martin and having a configuration quite distinct from that of its ICBM forbears, the latest version of the venerable vehicle is the Atlas V.  This modern Atlas variant can send nearly 65,000 lbs of payload into LEO and 29,000 lbs into GTO.

Posted in Aerospace, History