"Project Orion is now generating so much interest throughout the government that you can expect a continuous stream of visitors," Don Mixson warned Ted Taylor on June 19, 1959. "It is not the intent of the Air Force Special Weapons Center that such interest be discouraged. However, unless some control is exercised over visits, I believe your work will be seriously impaired." Visitors wishing to meet with Ted at General Atomic would have to obtain approval through Albuquerque first. Mixson made one exception: "the possible visit of Dr. von Braun."[292]
German-born rocket pioneer Wernher Magnus Maximilian von Braun joined the three-year-old Verein fur Rawnschiffahrt (VfR, Society for Spaceship Travel) as a student in 1930 at age eighteen. Founded on July 5, 1927, at the Goldnen Zepter (Golden Scepter) tavern in Breslau (now Wroclaw, Poland), the group's premise was that "out of small projects, large spacecraft can be developed which themselves can be ultimately developed by their pilots and sent to the stars."[293] On July 23, 1930, the small band of amateurs, including von Braun, static-tested their first liquid-fueled rocket engine; it ran for 90 seconds, consuming 6 kg of liquid oxygen, 1 kg of gasoline, and producing 7 kg of thrust.
Von Braun's days as an amateur ended in the fall of 1932, when the German army became interested in his work. Under military sponsorship, he led the development of the V-2 rocket, some 5,000 of which were produced. Fueled with liquid oxygen and alcohol, the V-2 was 46 feet long, weighed 27,000 pounds, and developed 56,000 pounds of thrust. Nearly 4,000 of these missiles, delivering one-ton warheads, were fired during World War II, but, limited to conventional high explosives and inertial guidance, they did little damage in proportion to their cost. Toward the end of the war von Braun abandoned his headquarters at Peenemiinde on the Baltic coast, retreating to the Bavarian mountains where he secreted the most important documents and dispersed his research group. He then surrendered to the Americans, assisting them in recovering fourteen tons of technical papers, 100 disassembled V-2 rockets, and 125 colleagues, who followed him to the United States. The rockets went to the Army's White Sands Proving Grounds in New Mexico and the scientists went to Fort Bliss in El Paso, Texas, where U.S. Army Ordnance provided the resources to resume designing rockets where the work in Germany had left off. The captured V-2s were launched between 1946 and 1951, their warheads replaced with a succession of instrument packages and second-stage space probes that gave the American space program a pre-Sputnik boost.
In June of 1950 the U.S. Army Ordnance Missile Command, under the directorship of von Braun, moved from Texas to the vacant Redstone Arsenal and munitions factory in Huntsville, Alabama, selected partly for its proximity to the Atlantic Missile Range at Cape Canaveral, Florida, where the next generation of rockets could be launched. Von Braun's group produced a series of direct successors to the V-2, starting with the Redstone medium-range tactical missile and ending with the Apollo-boosting Saturn 5, whose first stage, burning for 2.5 minutes, consumed 28,000 pounds of liquid oxygen and kerosene per second, producing 7.5 million pounds of thrust.
After the U.S. Air Force separated from the Army in 1947, the Army justified staying in the missile business on the ground that missiles were a form of artillery, an argument that could be taken only so far. The problem for von Braun and his Huntsville colleagues, who wanted to build larger and larger rockets, was that Ted Taylor and his Los Alamos colleagues were building smaller and smaller bombs. The military now wanted smaller rockets—of little interest to von Braun. Atlas and Titan boosters, now able to deliver warheads more powerful than anyone knew what to do with, would instead be adapted to put Mercury and Gemini space capsules in peaceful orbits around the earth. The original Saturn booster program, initiated by ARPA in late summer of 1958, was transferred to NASA in 1959 from the Department of Defense. On July 1, 1960, von Braun's entire operation in Huntsville, known since 1956 as the Army Ballistic Missile Agency, was transferred to NASA, becoming the George C. Marshall Space Flight Center, or MSFC. The Moon was next.
Von Braun failed to show up in La Jolla, so on September 12, 1960, Ted went to Huntsville instead. "I am very curious to see what the reaction of the classical rocketeers will be," he wrote to Stan Ulam just before his trip.[294] Von Braun was uninterested—at first. "When I began talking about the temperatures that were involved, and the reason for the small amount of ablation of the pusher plate, he literally went to sleep," remembers Ted. "Then I turned on the movie of that flight of the Putt-Putt and he woke up and became a strong supporter from that point on." The sight of the explosive-driven Orion model, blasting off from its launch pad at Point Loma, must have reminded von Braun of his own days spent at the VfR's raketenflugplatz in 1932. The VfR's first few rockets had exploded by accident; the Orion model delivered a series of spectacular explosions by design. The Orioneers were amateurs with an idea that just might work—no crazier than mixing liquid oxygen and gasoline in 1931.
In November of 1960 Ted met with von Braun during the Gardner Committee's space study meetings in Washington, but "he seemed less sharp than in Huntsville in September," according to Ted, "and the committee gave him a hard time. I have a feeling the spirit has been knocked out of the man by our government bureaucracy."[295] Both NASA's organization hierarchy and von Braun's chemical rockets were reaching maximum size. N-level bureaucracies, like N-stage rockets, suffer exponentially as N goes up. Saturn 5, weighing 6,000,000 pounds at launch, was barely able to get three people to the Moon and back. There were two ways to make it go farther: add another, much larger stage at the bottom, or put something different at the top.
To von Braun, Orion offered a way to extend the limits of chemical rockets. To Project Orion, von Braun's boosters offered a way to overcome the political and technical difficulties in launching Orion directly from the ground. Ted credits Frederick Ross with suggesting a boosted launch. "Sparked by Ross's comments," he noted on October 14, 1960, "I looked at what we could do using the Saturn booster, which makes it possible to scale a useful Orion down to a gross weight of 125 tons! This means 50 tons payload in a 300-mile orbit. 30 tons on the moon, over 20 tons back to a low orbit around the earth. Spent most of the evening estimating the neutron and X-ray heating for the 125-ton ship, and the shield weights required for a crew of about 8. The heating requires cooling the pusher, but is not outlandish. Got all excited imagining the following schedule: 2-ton model flying with high explosive in 1962, 20-ton model flight tested above the atmosphere by end of 1964, flight to the moon and back with 8 men in the 125-ton ship by the end of 1966."[296]
A Saturn 5 can lift 100 tons into low Earth orbit, or about 400 tons to the edge of the sensible atmosphere at 300,000 feet. The eight-engine first-stage Nova booster envisioned as a step beyond the Saturn 5 could loft Orion vehicles weighing up to 2,000 tons, or even 4,000 tons using "Super-Nova" or Nova II. The Air Force predicted that a 4,000-ton Orion, lofted by a 3,765-ton chemical booster, could deliver 1,480 tons to a soft landing on the moon—versus 240 tons for the envisioned 8,000-ton all-chemical Nova II.[297]
"This way of going about Orion may bring the big chemical rocket 'lobby' behind us, and suddenly generate serious enthusiasm for the project almost everywhere," hoped Ted.[298] Gaining the support of von Braun and the chemical rocketeers was not enough. Orion needed the approval of the nuclear propulsion community within NASA—already allied, in support of Rover, with the AEC. Rover, initiated in 1955 in an attempt to develop a nuclear-powered ICBM capable of delivering first-generation thermonuclear warheads, had the jump on Orion on three fronts: it was an established program already supported by the AEC; having lost its military justification it had already cultivated the NASA sponsorship required to stay alive; the technology, having nothing to do with bombs, was unclassified and familiar to conventional rocketeers. The operating principle—liquid hydrogen propellant is passed through the otherwise meltdown-hot core of a nuclear reactor—was easy to comprehend, even if problems such as radiation shielding and extreme temperatures were difficult to solve.
Mars
exploration vehicle designed by General Atomic for NASA in 1963-64: the
empty
propulsion module, weighing 100 tons, would be boosted into orbit by a
Saturn
5. Earth-orbit departure weight is 600 tons, with a destination payload
of 80
tons—including two Mars Excursion Modules that weigh 32 tons each.
Eight
personnel and 2,782 kiloton-yield pulse units are carried for the
450-day trip.
Orion's nemesis within NASA was Harold Finger, who became director of nuclear systems in 1958 and manager of the joint AEC-NASA Space Nuclear Propulsion Office in 1960. Finger believed Rover, not Orion, should be the first step toward post-Apollo visits to Mars and permanent bases on the Moon. "We need to walk before we run. And walking is Rover and Orion is running," he argued, according to Ted. Finger had joined the National Advisory Committee on Aeronautics (NACA) at age twenty in 1944, participating in its metamorphosis into NASA in 1958. His first assignment, at NACA's aircraft engine research lab in Cleveland, Ohio, had been testing captured German and Japanese turbochargers, leading him to jet engines and advanced propulsion concepts, including the prospects for nuclear propulsion in space. In May of 1961, two weeks before Kennedy's Moon-landing speech, Finger gave a talk urging die United States to aim directly for Mars, since this would accelerate the development of nuclear propulsion and a visit to the Moon could be made part of the trip. In 1959 he was appointed NASA's representative on the advisory board to ARPA on Project Orion, drafting the statement declining ARPA's offer to transfer Orion to NASA, after which the project went to the Air Force instead.
"We went to General Atomic and had extensive briefings from Ted and others," remembers Finger. "My main position, frankly, was 'Gee, this is an interesting concept, but how do you go about developing this concept?' That was my main concern. Look, we're used to developing everything on the ground. How are we going to test it? I said I have no question that you guys know how to build the explosive device. But I do question the ablative capability of the pusher plate; it's got to withstand thousands of impacts. And then you have the shock-absorber system. You have to test it and you have to test it repetitively. How do we really go about developing this to the point that we can put it up on Saturn 5—at the time we didn't have a Saturn 5—and have a reliable operation? That was my main concern, and to this day it still is."
After NASA declined Orion, the project kept resurfacing every year or two for review. On September 25, 26, and 27, 1961, there was an extensive series of meetings with NASA officials at General Atomic, chaired by Harold Finger, who took the position that the Air Force should continue the project but NASA should hold off on becoming involved. According to the Air Force, NASA's reviewers "agreed that 15 years and 10 billion dollars would represent optimistic estimates for the development effort," and were unwilling to support the project on any more modest middle ground. NASA's position was summed up at the end of 1961: "It is recommended that we do not pick up this project. The feasibility of such a device for use in vehicles is most marginal and it is possible that it never would be made to work. In addition, the project is most expensive and to continue the cost would be at the level of $2 million to $3 million a year."[299] Don Prickett, who represented the Air Force during the discussions with NASA, strongly disagreed. "There are always two philosophies encountered during the research phase of new concepts," he argued. "One which says that if the concept has potential for a significant step forward it is worth a considerable effort to solve the problems even if this effort involves high risks. There is the other philosophy which approves only of research in which there are no real fundamental problems to be solved but rather improvement of established technology. What we need is more people working on novel ideas to solve some of the problems rather than viewing the problems as unsolvable."[300]
General Atomic's estimated costs and development schedule appeared wildly optimistic by the standards of aerospace. "I used the word 'ship' rather than 'craft,' because the protagonists for this system talk in terms of heavy shipbuilding construction and assembly methods," Finger explained in describing Orion to a symposium on Mars exploration in June of 1963. His chief concern was that Orion could not be tested on the ground, in the style of von Braun's static test facility in Huntsville, or the Rover engine test facility at Jackass Flats. "It is always proposed that the system will be developed in flight. I think this is nonsense. I know of no system which has been developed in flight."[301] He also noted that NASA had yet to define any mission for Orion, beyond exploring Mars. "You have to build it and try it before you really know you could integrate the elements of the system. And then if we did it and got it working, what would we use it for?"
It was nuclear physicist James C. Nance who succeeded in enlisting NASA's support. Born in Arkansas in 1927, Nance came to General Atomic in 1960, after seven years as a project engineer on the Aircraft Nuclear Propulsion program at Convair aircraft in Forth Worth, where, as part of the flight-test crew for the Aircraft Shield Test Reactor, he was the first person to operate a nuclear reactor in the air. After three years as Ted's assistant, he became the manager of Project Orion in the fall of 1963, remaining at its helm until the end. "Ted and I had an informal agreement where he pushed AF/DOD and I pushed NASA, notably von Braun and MSFC," says Nance, who secured a small study contract from the Future Projects Office of the Marshall Space Flight Center in Huntsville, supporting about six people at General Atomic for six months.[302] This contract, beginning in July of 1963, was critical in demonstrating that Orion had NASA support—what the Air Force needed in order to continue its sponsorship without an immediate military requirement having been defined. The test ban was looming, and Orion's status as a peaceful enterprise would have to be established if any exemption was to be made for space propulsion using bombs.
Crew
quarters for the 10-meter Mars exploration vehicle, showing (at top)
the
navigation station, radiation-shielded propulsion control center, and
storm
cellar, with lateral passageways to the rest of the ship. The
furnishings in the main crew quarters (widened
section) will be used
under artificial gravity during coast periods and appear upside down.
"Jim Nance was very good at going after things; it was really his doing that we got NASA to put money in," explains Ted. "Von Braun's interest was one thing, but getting money from NASA headquarters was a whole other matter." Nance kept the project alive for a further two years, although growing opposition to the project reduced his role, as Freeman describes it, to being "very good as the captain of a sinking ship." Nance lobbied persistently for Orion, arguing that nuclear energy was essential to post-Apollo missions and that external explosions are intrinsically superior to an internal reactor as a way to propel a ship. "An old analogy here is that of flicking a hot coal off a rug back into the fireplace (impulsive system)," he explained. "If done adroitly, the interaction time is insufficient to burn your finger. But if you pick it up and set it in the fireplace, it is a different story (steady-state system). Note that the same payload is carried through the same velocity increment in both cases."[303] Rover is equivalent to holding the coal in one's hand while walking across the room. Orion is equivalent to skipping the coal across the rug. NASA got the point. "Vehicles utilizing such an engine and operating from earth orbit could typically deliver 45% of their gross weight as useful payload to the lunar surface, over 40% to the Mars surface, and could carry in excess of 25% in a fast, manned, round-trip to Mars," promised Nance.[304]
Nance and his colleagues proposed boosting the vehicle into orbit in three separate launches—first the engine, then the payload section, finally the bomb magazines. Further launches would deliver a crew to assemble and operate the ship. "Manned engines operating from parking orbits can be tested much in the same fashion as ocean-going vessels, i.e., short runs (one or more nuclear explosions) to long complicated maneuvers can 'shake down' the engines and train crews."[305] NASA could follow the incremental, step-by-step development path they were accustomed to, and Huntsville would have an excuse to keep launching Saturn or Nova boosters—constituting the bulk of the program's costs.
The NASA study—which never mentioned "bombs"—was performed in three stages. First, preliminary bounds were placed on vehicle performance and size. Second, engineering studies were conducted, resulting in a detailed conceptual design. Third, mission studies examined possible voyages, including the assignment of estimated operational costs. To supervise the mission studies NASA and General Atomic brought in one of Wernher von Braun's former Peenemunde colleagues, Krafft Ehricke, from the Atlas-Centaur program at Convair Astronautics. "The Atlas was a great success at that time and they wanted somebody with that sort of factual experience," explains Thomas Macken. Ehricke produced a detailed survey of the accessibility of the solar system to Orion, believing the age of space colonization was at hand. Macken remembers "one particular meeting when he talked about mining uranium on the Moon, and then you could take off from there to the end of the universe."
NASA started off thinking of a 1,000-ton ship, driven by 2-kiloton bombs. General Atomic had a five-year head start, with preliminary Studies of a series of 4,000-ton, interplanetary-capable designs, as well its 20-ton, 200-ton, and 800-ton orbital test vehicles. Thanks to specialized computer codes, these existing designs could be readily adapted to NASA's requirements. In presenting the alternatives to NASA, General Atomic differentiated the possibilities into three operational modes (disregarding the original mode of taking off directly from the ground).
In Mode I, "the engine/vehicle combination, loaded to full gross weight, is lofted above the sensible atmosphere prior to pulse-engine startup."[306] The Orion engine, with its shock absorbers fully compressed, is attached by explosive bolts allowing it to kick free from the expended booster before ejecting the first of its bombs. The bombs start firing at between 60 and 100 km altitude, which relaxes the demands of a surface launch, but still entails a high initial pulse rate and a risk of catastrophic failure in the event of missing even one or two shots. On the other hand, it relaxes the demand on the boosters, since a one-stage chemical booster is enough. "The chemical rocket systems planned to loft the nuclear pulse propelled vehicle above the atmosphere are called 'lofters,' " the General Atomic scientists explained to their NASA sponsors at an opening briefing in June of 1963. "This terminology is intended to remind one of the less stringent operational requirements for such chemical rockets as compared to large space boosters."[307]
In Mode II operation, the basic Orion engine, lofted just above the atmosphere as in Mode I, is then "self-boosted into orbit, but in an offloaded or perhaps 'empty' condition. The payload and a full supply of propellant is then taken aboard in orbit."[308] This relaxes the demand even further than Mode I, since the Orion engine carries only a brief series of bombs for its initial kick from the upper atmosphere into orbit. General Atomic proposed a 1,400-ton engine, with a 34-meter-diameter pusher plate for operational modes I and II. This required an enormous booster—of great interest to von Braun. "We had some great big boosters to get it out of the atmosphere and then start the nuclear business," says Hans Amtmann. "The moon rocket wasn't big enough."
In Mode III operation, the engine, propellant, and payload, "packaged in modules of approximately equal mass and diameter," and weighing "for example, one million pounds each," are boosted separately into orbit and assembled there. Much lower thrust is required, and pulse frequency is not critical when the Orion engine starts up. Standard launch modules could be assembled in different combinations to suit different mission plans. "For low-mission-velocity tasks, such as earth orbit-lunar orbit-earth orbit transportation, one or two propellant modules could be used with a large number of payload modules. For planetary missions, a large number of propellant modules could be used with one or two of payload."[309] A 500-ton engine, "compatible with Nova-class boosters," was proposed for Mode III.
The study group assumed, as a baseline for comparisons, a payload of 500 tons would be sent to orbit Mars. Missions to land on the Moon or orbit Jupiter were considered in less detail. Halfway through the study, NASA requested that the size of the vehicles be scaled down, with the 500-ton ship becoming the large version, and most of the design effort being focused on a 100-ton engine that could be boosted into orbit by an off-the-shelf Saturn 5.
"NASA mission constraints on the propulsion system were far less demanding," the summary to General Atomic's final report explained.[310] "Most of the significant results of this study concern a 10-m-diameter propulsion module, which is about half the size of the smallest module that has previously received serious design consideration, but which has very impressive (scaled) performance capability in the orbital start-up operational mode. Much of the credit for appreciating such a vehicle's capability goes to NASA for recognizing the logic and value in this size vehicle in spite of its poor propellant economics and comparatively degraded specific impulse."[311] This was a tactful way of saying that what NASA was interested in was a watered-down version of Orion. Mars was in; Enceladus was out.
The 10-meter (33-foot) -diameter Orion vehicle underwent intense design, engineering, and mission studies over the next few months. A variety of configurations, all built around the same basic engine, were explored, assuming representative 450-day missions to Mars, including a 50-day stay. These missions ranged from an eight-man orbital exploration mission carrying only 1,650 pounds of destination payload, requiring an Earth-orbit departure weight of 600 tons, to a twenty-man mission carrying a 330,000-pound destination payload, with an Earth-orbit departure weight of 1,200 tons. It would require four to nine Saturn launches to build up the basic vehicle in orbit, and for safety it was recommended that a convoy of at least two vehicles make the voyage at the same time. Small "space taxis" would allow transfers between separate ships. The pulse units, of nominal kiloton yield, would weigh 311 pounds and would be ejected at 86-second intervals, with 2,782 pulses required per trip.[312] The vehicle would range between 160 and 204 feet in length depending on how many propellant magazines, with 900 pulse units in each layer, were loaded in revolving chambers around its central spine. The ships were long and slender, completely unlike the original dome-shaped vehicle imagined in 1958 and 1959.
Instead of spinning like a top, to provide artificial gravity around the circumference of the observation deck in the upper dome, the NASA Vehicle would be tumbled end over end: "During prolonged coast periods, artificial gravity is attained by slow rotation (approximately 4 rpm) of the entire vehicle. Three spin-ups and spin-downs are provided during a typical exploration mission."[313] The crew quarters and command station have two sets of furniture so that floor and ceiling can be interchanged: right-side up for use during acceleration periods, upside down for use during artificial gravity mode. Detailed drawings were made of every aspect of the ship, and aeronautical engineers like Thomas Macken, who began his career in 1934, working on wooden biplanes for Avery-Rowes in Manchester, now spent his time on details like shock-absorber attachments, cooling fluid recirculation, crew-compartment shielding, and determining the extent of meteoroid-protection required during an eighteen-month trip to Mars and back.
Details
of 10-meter Orion engine designed under
contract to NASA's Marshall Space Flight Center, 1964.
Smaller Orion vehicles, lacking the inherent radiation shielding of more massive designs, required the crew to take shelter in a shielded compartment during engine operation and in the event of solar storms. Conditions would be cramped. "For short duration missions (nominally about thirty days with an upper limit of ninety days) relatively crowded conditions are assumed satisfactory, including bunk sharing and acceleration couches only in the combined powered flight compartment/storm cellar," noted Walter Mooney in Orion Personnel Accommodations, issued in September 1963. "For longer missions (nominally 450 days, but from say 90 days to 1,000 days or beyond) more spacious conditions will be required; for example, it is felt there should be no bunk sharing and, desirably, private sleeping rooms should be provided each individual crewman. Special areas for eating, exercising, and entertainment will be desired for any long space missions."[314] Gone were the luxurious accommodations Ted and Freeman had imagined in 1958. The smaller Orion engine required high-density, tungsten propellant, so the original plans to recycle crew waste into the bomb canisters as propellant no longer held. "For the longer missions complete water recovery including urine distillation may be desirable," it was acknowledged.[315] NASA Orion crews would be flying coach.
The 10-meter vehicle could perform a bare-bones mission to Jupiter, but a 20-meter (65.6 feet) diameter version, designed to be lofted by Nova-class boosters, was preferred. This would take a twenty-man crew and a 100,000-kg destination payload into orbit around Callisto, the second-largest moon of Jupiter, from where chemical-powered landings on Callisto and unmanned probes to the Jovian surface would be launched. Velocity increments for the mission, with return to Earth orbit, totaled 64,000 m/sec, and the voyage would take 910 days. Earth-orbit departure weight would be 6,000 tons, including 8,291 pulse units, each weighing 993 pounds.
Even this 20-meter ship was much reduced in size and performance from the original Orion designs. "The propulsion modules of this study are rather austere and inefficient in comparison with the apparent potential of nuclear-pulse propulsion," explained the authors of the final NASA report.[316] In making their initial pre-contract briefing to NASA, the Orion group had explained that "there will also be a small effort applied to updating current data on a massive third generation vehicle concept, and to approximate its feasible size limitations. This was envisioned as a vehicle capable of velocity increments totaling more than 300 km/sec, and "of a size to put it in the planetary colonization transport category."[317] In the final report, only a few pages are devoted to these third-generation ships.
Two "advanced-version hypothetical vehicles" are described. "Vehicle A is assumed to have a specific impulse of 10,000 sec and a thrust of 10 million lbs.; B was assigned a specific impulse of 20,000 sec and a thrust of 40 million lbs. The additional ground rule was the assumption of a near-earth-surface initiation of nuclear-pulse operation."[318] These 4,000- and 16,000-ton ships, capable of mission velocities of up to 500,000 ft/sec, are the last official trace of the ocean-liner-class Orion vehicles that Ted and Freeman were working on in 1959.[319]
In the final report to NASA, potential problems were largely dismissed. A typical Mars mission would consume only 28 percent of the United States' annual production of plutonium, assuming the least-efficient conversion methods, and only .06 percent if breeder reactors went full speed ahead. launch sites in Alaska and Australia were investigated, but it was concluded that Florida would be satisfactory, for a boost-to-orbit Saturn 5 start. Eye burn was manageable. "Since high-altitude nuclear explosions are visible from a large area of the earth's surface, there is reasonable probability that several individuals would be looking at the detonation points. We determined conservatively that at altitudes above about 90 km, the flux would not be sufficient to cause retinal burn to the unprotected eye."[320] Fallout was believed to be adequately diminished by orbital start-up at higher magnetic latitudes, with a more serious hazard being a launch-pad explosion of a booster carrying a full load of bombs. The worst-case scenario assumed "that approximately 1,000 pulse units would fall in the fire and all the high explosive (20,000 kg) would detonate. Assuming current nuclear-device design practice, there would be no nuclear explosion or criticality event." There could be big trouble, however, even if the bombs did not explode. "A more serious problem would be the possible burning or vaporization of plutonium, which could produce a downwind inhalation hazard and ground-contamination hazard. If all of the plutonium available were vaporized in the form of an aerosol, a substantial down-range hazard might exist."[321]
General Atomic estimated that a Mars mission, using Saturn-boosted, 10-meter Orion vehicles, could be conducted for something under $2 billion in development and direct operating costs. "Nuclear pulse clearly appears to be the most promising long-range advanced propulsion system which could be available in the middle eighties or sooner," Krafft Ehricke argued, introducing his 425-page analysis of interplanetary missions and their comparative expense.[322] For typical Mars missions, the Saturn 5 launches were determined to make up over 60 percent of the direct operating costs.
Ted was convinced that the project was back on track for Mars. "ORION has crossed a major milestone, I believe, in getting some formal support from NASA," he wrote to Freeman on July 11, 1963. "This will be the first time since the summer of 1958 that we have had a clear charter for more than a few months."[323] The test ban appeared imminent but not insurmountable, and when NASA's interest in Orion became public, Freeman sent congratulations to Ted. "The great thing that has happened to strengthen your position is the general realization, even among the public, that chemical rockets have nothing to offer beyond the trip to the moon," he wrote. "The effect of the treaty on Orion is likely to be quite healthy in the long run. It means the emphasis is automatically pushed away from military applications and toward long range exploring missions. It is just what we always wanted to do."[324]