In November 1957 JPL proposed “Juno III”, a four stage Jupiter-boosted rocket similar to Juno II but using more powerful upper stage solid motors from Grand Central Rocket Company. Juno III would be able to lift about 54.4 kg (120 lbs) to low earth orbit (LEO), about 20% more than Juno II. Juno III was proposed to launch a spacecraft to photograph the far side of the Moon.
ABMA and JPL planners knew that even more capable launch vehicles would be needed. On March 20, 1958, ABMA’s General Medaris asked JPL to investigate the use of one or two liquid storable propellant upper stages atop Jupiter. The new configuration would be named “Juno IV”.
On March 27, 1958, newly-formed Advanced Projects Research Agency (ARPA) announced “Operation Mona”, its program to aim U.S. satellites toward the Moon. ARPA funded three Thor-Able and two Juno II launches for the program. Juno III was not included, which effectively ended all plans for Juno III development.
By early April, JPL had completed a preliminary design study for Juno IV and briefed ABMA on the results. Its study recommended use of hypergolic pressure-fed liquid upper stages. Juno IV would be capable of lifting up to 10 to 20 times as much payload as Juno II/III,
Juno IV’s upper stages would use nitrogen tetroxide (N2O4) oxidizer and hydrazine (N2H4) fuel. JPL would develop two new engines for the stages. A 20.4 tonne force (45,000 lb) thrust engine would power the second stage. A 2.72 tonne force (6,000 lb) thrust engine would propel the third stage.
Both stages would be pressure-fed, using helium stored in high-pressure spheres. A “heated hybrid” pressure feeding system was proposed for both stages. The system would use a small hydrazine gas generator to heat helium passing through a heat exchanger. Gas generator products would pressurize the hydrazine tank. Heated helium would pressurize the nitrogen tetroxide tank. The “heated hybrid” approach would result in substantially lower mass compared to standard pressure fed methods.
The main engines would gimbal for pitch and yaw control. Gimbaled gas generator exhaust would provide roll control. The third stage would have used hydrazine thrusters for three-axis control during coasting periods.
Both stages were limited to 1.778 meters (70 inches) in diameter to allow mating atop the existing Jupiter guidance compartment (“aft unit”). The stages would consist of separate 2014-T6 aluminum fuel and oxidizer tanks supported by aluminum semi-monocoque interstage and intertank structures. Oxidizer would be stored in the forward tank, fuel in the aft tank, on both stages.
A three-stage Juno IV would weigh up to 62.41 tonnes (137,600 lbs) at liftoff. Its Jupiter first stage would be loaded with up to 44.5 tonnes (98,100 lbs) of propellant. The second stage would carry up to 11.14 tonnes (24,550 lbs) of propellant. The third stage would be loaded with up to 3.4 tonnes (7,500 lbs) of propellant. Propellant loading would vary depending on the mission type, with maximum upper stage loading for LEO missions and reduced loading for lunar or escape missions. Reduced upper stage propellant loads would be offset by increased first stage propellant loads, and vice-versa.
Three-stage Juno IV would be able to lift 1,000 kg (2,200 lbs) to a 400 km (250 mile) orbit, or 163 kg (360 lbs) toward the Moon. This was more than three times better than Thor-Able and comparable to Thor-Agena A, an IRBM-based launcher then under development that would have been a Juno IV contemporary. Pickering asked his JPL teams to study a 159 kg (350 pound) Mars flyby spacecraft that Juno IV could launch.
On May 1, 1958,ARPA gained control of Juno I and II, beginning the transition of orbital launch programs away from the U.S. Army. ABMA and JPL formally proposed Juno IV development to ARPA on May 5. The proposal called for a first flight in March 1959 using an interim second stage engine, a 15 tonne (33,000 lb) thrust GE 405H model derived from Vanguard’s first stage engine, as an interim step while JPL’s new “45K” engine was developed.
ARPA authorized JPL to continue its Juno IV upper stage design work on May 31, 1958. The Lab test fired a “45K” development engine on June 3. This was only a brief firing using an uncooled nozzle. JPL performed similar tests of its “6K” engine. Testing showed that the second stage engine would achieve 304 second vacuum specific impulse while the third stage engine would make 301 seconds.
During July, two ARPA engineers, David A. Young and Richard B. Canright, visited ABMA to review programs. While there, they learned about a year-old ABMA study for a “Super Jupiter”. “Super Jupiter” plans called for a first stage of unprecedented size powered by four yet-to-be-developed Rocketdyne E-1 engines that together would have produced 671 tonnes (1.48 million pounds) of thrust. ARPA’s engineers were interested in moving quickly during that post-Sputnik era. They suggested substituting eight existing Thor/Jupiter S-3D engines for the still-to-be-developed E-1. The change would save $60 million and two years in development time. The new rocket was soon named “Juno V”.
Juno IV Authorized
Juno IV went through a series of proposal stages during the summer of 1958. Plans to use the GE engine were dropped in favor of an interim “Juno IVA” two-stage rocket. Juno IVA would use the third stage as a second stage, with the stage slightly enlarged to carry up to 4.08 tonnes (9,000 lbs) of propellant. Juno IVA would lift about 494 kg (1,090 lbs) to a 400 km (250 mile) orbit, but would be unable to perform lunar or escape missions.
JPL would employ a light weight guidance system, borrowed from the Sergeant missile program, for Juno IVA. The Jupiter ST-90 platform would have operated during first stage flight. MING (Miniature Injection Guidance) would have controlled the second stage flight. The system would have used a single-axis platform for pitch guidance, augmented by miniature integrating gyros for yaw and roll. A magnetic tape recorder programmer would have provided pitch program control.
On August 15, 1958, ARPA authorized development of both Juno IVA and Juno V. Plans called for at least three Juno IVA launches, beginning in 1959. ARPA expanded the program in September, adding three three-stage flights. The GE engine reentered the program to power the second stage on these flights. The three-stage rockets would be named “Juno IVB”. Plans still called for eventual use of JPL’s “45K” engine.
Sudden Death, and Vega
Atlas-Vega would have used Juno IV Upper Stage
NASA official began operations on October 1, 1958 and began picking up the ARPA programs. On October 9, NASA’s Propulsion Committee met with ARPA officials. During the meeting, NASA’s Dr. Abe Silverstein said that NASA would keep ARPA’s Juno II program, but would drop Juno IV. Juno IV, he said, “would do no job that the old boosters that are around now cannot do”. On October 10, ABMA’s Lt. Col Glenn Crane met with Silverstein who again reaffirmed his Juno IV decision.
Reflecting NASA’s plans, ARPA officially canceled Juno IV on October 17, 1958. About $8 million of Juno IV funding was redirected to Juno V. Suddenly Jupiter was a dead end program, with only a limited missile deployment and only 10 Juno II orbital launches planned. With the first Juno II launch still two months away, the Juno II project team found itself working on a project with an expiration date.
All four of the original IRBM/ICBM U.S. missile programs led to orbital launch vehicles, but Silverstein’s abrupt October 1958 decision determined that Jupiter’s family would have a short and bittersweet life.
The Juno IV decision spelled the beginning of the end of JPL’s in-house launch vehicle propulsion work. JPL joined NASA on December 3, 1958. Three days later the new NASA center proposed its “6K” Juno IV upper stage for use with NASA proposed Atlas-Vega launch vehicles. On January 30, 1959, JPL was awarded $2 million to start work on the engine.
On March 17, 1959, JPL performed its first fuel-cooled “6K” engine test. Plans called for eight Atlas-Vega launches beginning in August 1960. Before the year ended, however, NASA learned about the secret Agena B program. Like JPL’s “6K” stage, Agena B would be restartable. On September 30, a recommendation was made to drop the JPL stage in favor of Agena B. Silverstein made the decision official in early November, and the entire Vega program was canceled on December 7, 1959.
JPL’s upper stage work ended. The Lab was left with NASA’s exploration spacecraft work, at which it soon excelled. Early studies of Juno IV launched spacecraft for exploring the Moon and Mars led to the eventual development of Ranger and Mariner.
Also read: KING OF GODS: The Jupiter Missile Story
Mercury-Jupiter Projected Appearance, Illustrating Mating Problem
Early NASA plans for Project Mercury, as of late 1958, were to use eight Mercury Redstones augmented by two Mercury Jupiters for suborbital test flights. The Mercury Jupiters would have explored the flight envelope at higher velocities than Redstone, prior to the use of Mercury-Atlas.
The first flight would have carried a primate, the second possibly an astronaut. Later plans hinted at unmanned tests only, with the flights meant to qualify Mercury for maximum reentry load factors. ABMA would have built the spacecraft adapter for Jupiter.
In July 1959, NASA canceled Mercury-Jupiter when it became apparent that Atlas could serve the same purpose. Basically the schedule was so compressed that Atlas flights would have happened before the Jupiter flights. NASA spent $1.8 million on Mercury-Jupiter before canceling the effort. Although two Jupiters were ordered, they do not appear to have ever been delivered.
One challenge was that the Mercury spacecraft and escape tower weighed 1.935 tonnes, about 0.75 tonnes more than Jupiter’s nose cone. In addition, Jupiter’s “aft unit” guidance and control compartment could be cut down to only 1.778 meters (70 inches) in diameter at its top while the Mercury capsule was 1.892 meters (74.5 inches) in diameter. NASA eventually deemed the structural redesign effort excessive for only two flights.
Saturn I (SA-T) Assembly Showing Jupiter and Redstone-Based Tanks
Although it lost Juno IV, ABMA was kept very busy with Juno V. ABMA decided to use not just a cluster of engines, but also a cluster of tanks. The design combined eight 1.778 meter (70-inch) diameter tanks, built using Redstone tooling, with a central 2.667 meter (105-inch) diameter tank manufactured with Jupiter missile tooling. The central tank and four of the outer tanks would carry LOX and would be load bearing. The other four tanks would carry kerosene fuel and would not carry structural loads because they would not expand and contract as much as the supercold LOX tanks.
In August 1958, ARPA initially provided funding for a Juno V feasibility demonstration project The original plan called for construction of only one booster for captive firing tests on a modified Jupiter/Redstone test stand at the Arsenal. ABMA quickly contracted Rocketdyne to develop the first stage engine, now designated H-1. Early H-1 versions would be rated at 165,000 pounds thrust. Later models would produce 188,000 pounds of thrust.
Years after the final Juno II launch, after the deployed Jupiter missiles were scrapped or turned into lawn ornaments, and after the old Jupiter/Redstone launch complex had been turned into a museum, Jupiter’s legacy lived on in NASA’s Saturn and Saturn IB. Chrysler assembled Jupiter based tanks for Saturn until production ended in 1968. The final Saturn IB launch, for the ASTP mission, took place on July 15, 1975, about 20 years after Wernher von Braun had presented ABMA’s IRBM proposal to the Armed Services Policy Committee.