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A Distant Echo

Fifty-seven years ago this month, the United States successfully launched the Echo 1A passive communications satellite into Earth orbit. The 100-foot diameter balloon was among the largest objects ever to orbit the Earth.

A plethora of earth-orbiting communication satellites provide for a global connectivity that is commonplace today. Such was not always the case. Roll the clock back more than a half-century and we find that a global communications satellite system was just a concept. However, keen minds would soon go to work and provide mankind with yet another tangible space age benefit.

Communications satellites are basically of two types; passive and active. A passive communications satellite (PCS) simply reflects signals sent to it from a point on Earth to other points on the globe. An active communications satellite (ACS) can receive, store, modify and/or transmit Earth-based signals.

The earliest idea for a PCS involved the use of an orbiting spherical balloon. The balloon was fabricated from mylar polyester having a thickness of a mere 0.5 mil. The uninflated balloon was packed tightly into a small volume and inserted into a payload canister preparatory to launch. Once in orbit, the balloon was released and then inflated to a diameter of 100 feet.

The system described above materialized in the late 1950′s as Project Echo. The Project Echo satellite was essentially a huge spherical reflector for transcontinental and intercontinental telephone, radio and television signals. The satellite was configured with several transmitters for tracking and telemetry purposes. Power was provided by an array of nickel-cadmium batteries that were charged via solar cells.

Echo 1 was launched from Cape Canaveral, Florida on Friday, 13 May 1960. However, the launch vehicle failed and Echo 1 never achieved orbit. Echo 1A (sometimes referred to as Echo 1) lifted-off from Cape Canaveral’s LC-17A at 0939 UTC on Friday, 12 August 1960. The Thor Delta launch vehicle successfully placed the 166-lb satellite into a 820-nm x 911-nm orbit.

An interesting characteristic of the Echo satellite was the large oscillation in the perigee of its orbit (485 nm to 811 nm) over several months. This was caused by the influences of solar radiation and variations in atmospheric density. While these factors are just part of the earth-orbital environment, their effects were much more noticeable for Echo due to the type’s large surface area-to-weight ratio.

Echo 1A orbited the Earth until it reentered the Earth’s atmosphere on Saturday, 25 May 1968. Echo 2 was a larger and improved version of Echo 1A. It measured 135-feet in diameter and weighed 547-lb. Echo 2 orbited the Earth between January of 1964 and June of 1969. Other than the Moon, both satellites were the brightest objects observable in the night sky due to their high reflectivity.

The Echo satellites served their function admirably. For a time, they were quite a novelty. However, progress on the ACS scene quickly relegated the PCS to obselescence. Today, virtually all communication satellites are of the ACS variety.

Posted in Aerospace, History

X-15 Maximum Apex Mission

Fifty-four years ago today, NASA chief research pilot Joseph A. Walker flew X-15 Ship No. 3 (S/N 56-6672) to an altitude of 354,200 feet. This flight would mark the highest altitude ever achieved by the famed hypersonic research vehicle.

Carried aloft by NASA’s NB-52A (S/N 52-0003) mothership, Walker’s X-15 was launched over Smith Ranch Dry Lake, Nevada at 17:05:42 UTC. Following drop at around 45,000 feet and Mach 0.82, Walker ignited the X-15’s small, but mighty XLR-99 rocket engine and pulled into a steep vertical climb.

The XLR-99 was run at 100 percent power for 85.8 seconds with burnout occurring around 176,000 feet on the way uphill. Maximum velocity achieved was 3,794 miles per hour which translates to Mach 5.58 at the burnout altitude. Following burnout of the XLR-99, Walker’s X-15 gained an additional 178,200 feet in altitude as it coasted to apogee.

Joe Walker went over the top at 354,200 feet (67 miles). Although he didn’t have much time for sight-seeing, the Earth’s curvature was strikingly obvious to the pilot as he started downhill from his lofty perch. Walker subsequently endured a hefty 5-g’s of eyeballs-in normal acceleration during the backside dive pull-out. The aircraft was brought to a wings-level attitude at 70,000 feet. Shortly after, Walker greased the landing on Rogers Dry Lake at Edwards Air Force Base, California.

The X-15 maximum altitude flight, in which the aircraft’s design altitude was exceeded by more than 100,000 feet, lasted 11 minutes and 8 seconds from drop to nose wheel stop. In that time, Walker and X-15 Ship 3 covered 305 miles in ground range. This mission was Ship No. 3’s 22nd flight and the 91st of the legendary X-15 Flight Research Program.

For Joseph Albert Walker, the 22nd of August 1963 marked his 25th and last flight in an X-15 cockpit. The mission qualified him for Astronaut Wings since he had exceeded the 328,000 foot (100 km) FAI/NASA standard set for such a distinction. However, it would be more than four decades after his historic mission that Walker would be officially be recognized as an astronaut. In a special ceremony conducted at NASA’s Dryden Flight Research Center on Tuesday, 23 August 2005, Joe Walker was posthumously awarded his Astronaut Wings.

Posted in Aerospace, History

The Big Bang

Fifty-three years ago yesterday, the fabled North American X-15 hit a speed of 3,590 mph (Mach 5.23) in a flight that reached an altitude of 103,300 feet. While decelerating through Mach 4.2, the nose gear of the aircraft unexpectedly deployed in flight.

The 114th powered flight of the legendary X-15 Program took place on Friday, 14 August 1964. USAF Major Robert A. Rushworth was at the controls of X-15 Ship No. 2 (S/N 56-6671). The mission would be Rushworth’s 22nd flight in the famed hypersonic aircraft.

X-15 drop from the NB-52A (S/N 52-0003) launch aircraft took place over Delamar Dry Lake, Nevada. Seconds later, Rushworth called for 100% power from the X-15’s XLR-99 liquid-fueled rocket engine as he pulled into a steep climb. He subsequently pushed-over and then leveled-off at 103,300 feet.

XLR-99 burnout occurred 80.3 seconds after ignition. At this juncture, the X-15 was traveling at 3,590 mph; better than 5 times the speed of sound. Following rocket motor burnout, the aircraft slowed and began to lose altitude under the influence of weight and aerodynamic drag.

As the Mach meter needle passed through Mach 4.2, Rushworth heard a loud bang from the airframe. The aircraft became hard to control as it gyrated in pitch, yaw and roll. Rushworth was equal to the moment and brought his troubled steed under control. However, the aircraft had an uncommanded sideslip and Rushworth had to use left aileron to hold the wings level.

Gathering his wits, Rushworth realized that the loud bang he heard was very similar to that which occurred when the nose gear was deployed in the landing pattern. Unaccountably, the X-15 nose gear had deployed in supersonic flight. An unsettling confirmation of Rushworth’s hypothesis came when the pilot spotted smoke, quite a bit of it, in the X-15 cockpit.

As Rushworth neared Edwards Air Force Base, chase aircraft caught up with him and confirmed that the nose gear was indeed down and locked. Further, the tires were so scorched from aerodynamic heating that they probably would disintegrate during touchdown on Rogers Dry Lake. They verily did.

Despite his tireless nose gear, Rushworth was able to control the rollout of his aircraft fairly well on the playa silt. He brought the X-15 to a stop and deplaned. Man and machine had survived to fly another day.

Post-flight analysis revealed that expansion of the X-15 fuselage due to aerodynamic heating was greater than expected. The nose gear door bowed or deformed outward more than anticipated as well. Together, these two anomalies caused the gear uplock hook to bend and release the nose gear. Fixes were subsequently made to Ship No. 2 to prevent a recurrence of the nose gear door deployment anomaly.

Rushworth next flew X-15 Ship No. 2 on Tuesday, 29 September 1964. He reached a maximum speed of 3,542 mph (Mach 5.2) at 97,800 feet. The nose gear door remained locked. However, while decelerating through Mach 4.5, Rushworth heard a bang that was less intense than the previous flight. This time, thermal stresses caused the nose gear door air scoop to deploy in flight. While the aircraft handled poorly, Rushworth managed to get it and himself back on the ground in one piece.

Following another redesign effort, Rushworth took to the air in X-15 Ship No. 2 on Thursday, 17 February 1965. He hit 3,539 mph (Mach 5.27) at 95,100 feet. On this occasion, both the nose gear door and nose gear door scoop remained in place. Unfortunately, the right main landing skid deployed at Mach 4.3 and 85,000 feet.

Thermal stresses were once again the culprit. Despite degraded handling qualities with the landing skid deployed, the valiant Rushworth safely landed the X-15. Upon deplaning, he is reported to have kicked the aircraft in a show of disgust and frustration. Unprofessional maybe, but certainly understandable.

Yet another redesign effort followed in the aftermath of the unexpected main landing skid deployment. This was the third consecutive mission for X-15 Ship No. 2 and Rushworth to experience a thermally-induced landing gear or landing skid deployment anomaly. Happily, subsequent flights of the subject aircraft were free of such vexing issues.

Posted in Aerospace, History

GT-5 – Eight Days or Bust

Fifty-two years ago this month, NASA astronauts Leroy Gordon “Gordo” Cooper and Charles M. “Pete” Conrad set a new spaceflight endurance record during the flight of Gemini 5. It was the third of ten (10) missions in the historic Gemini spaceflight series. The motto for the mission was “Eight Days or Bust”.

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 deboost 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 V (GT-5) lifted-off at 13:59:59 UTC from LC-19 at Cape Canaveral, Florida on Saturday, 21 August 1965. The two-stage Titan II launch vehicle placed Gemini 5 into a 189 nautical mile x 87 nautical mile elliptical orbit.

A primary purpose of the Gemini 5 mission was to stay in orbit at least eight (8) days. This was the minimum time it would take to fly to the Moon, land and return to the Earth. Other goals of the Gemini 5 mission were to test the first fuel cells, deploy and rendezvous with a special rendezvous pod and conduct a variety of medical experiments.

Despite fuel cell problems, electrical system anomalies, reaction control system issues and the cancellation of various experiments, Gemini 5 was able to meet the goal of an 8-day flight. But it wasn’t easy. The last days of the mission were especially demanding since the crew didn’t have much to do. Pete Conrad called his Gemini 5 experience “8 days in a garbage can.”

On Sunday, 29 August 1965, Gemini 5 splashed-down in the Atlantic Ocean at 12:55:13 UTC. Mission elapsed time was 7 days, 22 hours, 55 minutes and 13 seconds. A new spaceflight endurance record.

Gemini 5 was Gordon Cooper’s last spaceflight. Cooper left NASA due to a deteriorating relationship with management. Pete Conrad flew three (3) more times in space. In particular, he commanded the Gemini 11, Apollo 12 and Skylab I missions. Indeed, Conrad’s Apollo 12 experience made him the third man to walk on surface of the Moon.

Posted in Aerospace, History

Lifting Body Precision Landing

Forty-two years ago this week, the USAF/NASA/Martin X-24B became the first lifting body to make an unpowered precision landing on a concrete runway. The feat was pivotal to convincing NASA officials that landing the Space Shuttle Orbiter in an unpowered state was operationally feasible.

Early Space Shuttle Orbiter operational concepts featured the use of a pair of turbojets to provide a powered landing capability. These airbreathing engeines were to be internally stowed just below the Orbital Maneuvering System (OMS) pods. The turbojets would be deployed and started once the Orbiter had decelerated to high subsonic flight speeds.

While airbreathing propulsion would give the Orbiter a loiter and go-around capability, the drawbacks were significant. Jet fuel would have to be carried into and out of earth orbit. The weight of this fuel and the turbojets would severely penalize Orbiter payload capability. Further, the system would increase both the complexity of and cost to Shuttle operations.

As the Shuttle Program grappled with the development of a powered landing capability for the Orbiter, the NASA DFRC flight test community made what appeared to be a rather bold claim. The Orbiter could simply glide all the way to touchdown and land deadstick. After all, X-planes had been doing so safely and without incident since the late 1940’s.

A leading proponent of unpowered Shuttle landings was NASA DFRC test pilot John Manke. He was convinced that the Orbiter could routinely and safely conduct unpowered precision landings on a concrete runway. If true, the Orbiter could land anywhere a 15,000-foot concrete runway was located.

Manke proposed that the X-24B (S/N 66-13551) lifting body be employed to conduct unpowered precision landings on Runway 04/22 at Edwards Air Force Base. He and fellow test pilot USAF Lt. Col. Michael V. Love practiced low lift-to-drag precision landings using F-104 and T-38 aircraft in preparation for the demonstrations.

On Tuesday, 05 August 1975, John Manke successfully made the first-ever unpowered precision landing of an aircraft on a concrete runway. The X-24B main gear touched-down exactly at the aimpoint situated 5,000 feet down Runway 04/22. On Wednesday, 20 August 1975, Mike Love duplicated the feat.

Following the successful unpowered precision landings with the X-24B lifting body, John Manke was quoted as saying: “We now know that concrete runway landings are operationally feasible and that touchdown accuracies of ±500 feet can be expected.” NASA Space Shuttle Program management concurred and officially adopted the unpowered precision landing concept.

History records that thirty-one years of Orbiter flight operations confirmed the wisdom of that long-ago decision.

Posted in Aerospace, History