October 14, 1984
It was a massive effort from Dryden. Both NB-52 carriers were airborne at the same time, each carrying under their wing pylon a piloted X-27B. Mission of the day entailed a complex aerial ballet.
The NB-52A lifted-off first and circled over Edwards, waiting for its NB-52B sibling. With the end of the X-15 program in 1969 old NB-52A had been mothballed at Davis Monthan. After the shuttle and SST fiascos of 1971 President Nixon had to somewhat bailout a belaguered aircraft industry so a new program of high speed research has been examined. Enough money was pumped into Dryden that the older NB-52A could be taken out of mothball and put back into service again.
The X-27 subscale shuttle program (SSP) had been funded in 1972 at the expense of the X-24B lifting body program, which had been cut. There had been first an unpowered, unpiloted glider, the X-27A , followed by a couple of piloted X-27Bs. The rocket engine was still the plain old XLR-11, of Bell X-1 fame.
Dick Scobee and Herbert Lawrence dropped their vehicles from under the wings of the B-52 motherships. The two stubby rocketplane shot upwards, flying in parallel trajectories. They flew in a high parabola, up to 80 000 feet and mach 2. Once there, the two pilots experienced with two minutes of weightlessness.
Scobee carefully manoeuvered its X-27B so that it flew above Lawrence own machine. Once there Scobee pressed a button, and two traps opened at the bottom of its subscale shuttle; a crude refueling boom spurted out. Lawrence for his part deployed a refueling probe; it protruded from the nose of his X-27B. Today's objective was to keep the two machines linked for thirty seconds. No atempt was made to transfer liquid oxygen or acohol – propellants of the XLR-11 rocket engine.
The program funding came from DARPA, a military agency known to test hare-brained concepts on shoestring, black budgets.
ORAL HISTORY TRANSCRIPT – BOEING ORION – PART 1
Robert Salkeld
In 1973 former Alamogordo mayor Dwight Ohlinger was inspired by the National Baseball Hall of Fame and Museum to propose a Space Hall of Fame, and further to propose that it be built at Alamogordo because so much of the developmental work for the space program had been done in the Tularosa Basin. The main building was designed and constructed as a "golden cube" (a cube with a gold-tinted glass exterior) and dedicated on October 5, 1976, opening to the public on November 23, 1976.
At the dedication ceremony the initial fifteen Hall of Fame members were inducted, and there was an aerospace conference entitled The Eagle has returned. And I was present that day - interestingly, Maxwell Hunter was also there, but not to discuss Single-Stage-To-Orbit vehicles. Max was deep into the Hubble space telescope studies, together with the Agena tug to bring it to the space station for maintenance. Hunter hadn't gave up on reusable launch vehicles. More about him later.
Present at the conference that day was also legendary NASA engineer Maxime Faget, still bitter about the loss of the space shuttle.
So there I was, at that space gathering, and I was paired with a little known engineer, Richard Nau from General Dynamics Convair division.
To my surprise, I discovered that Nau also had considered inflight refueling of a space plane, but at hypersonic speeds, a crazy concept that he had rightfully dismissed. That idea reached as far bak as 1963 and the Aerospaceplane. As for me, I had suggested subsonic refueling of cryogens in order to have a lighter TSTO shuttle at lift-off.
The Aerospaceplane had been a military program ran from 1958 to 1964. In many ways it paralleled with DynaSoar, and was in fact intended to replace it. It was a broad and pragmatic program where, for the first time, fully reusable space plane concepts were comprehensively reviewed. It was pretty much the RASV of its time: that Air Force dream of a space plane as flexible as a fighter-bomber; a machine that could lift-off from a very ordinary air base into Earth orbit and back.
Because it was the first study of that kind there was no taboos, which mean even the wildest ideas were examined. And that included Richard Nau hypersonic refueling; there was even talk of flying a pair of X-15 to test that.
Needless to say, the hypersonic shock wave, made of heat and sonic booms and turbulences, would have resulted in a catastrophic collision. That obvious fact in turn shot inflight refueling dead for many years, until I brought it back in 1973 (with a more reasonable subsonic tanker, however).
As the conference went on Richard and I were asked by Faget for further details about the Aerospaceplane varied options; it was obvious the legendary designer was searching for a technological breakthrough able to bring his cherished shuttle out of the development hell where it languished since 1972.
Richard Nau suggested we once again review the Triamese concept his company had designed a decade before, in 1968. Richard Nau remembered pretty well how the Triamese had been eliminated from the initial round of shuttle studies.
The initial round of shuttle studies, during the first half of 1969, had come to $1.2 million, divided equally among four contractors. NASA now extended these studies by giving $150,000 more to each of three contractors, with McDonnell Douglas receiving $225,000. The participating companies also received new instructions that redirected their work.
Lockheed was to continue with studies of Star Clipper and of its own version of the Triamese. General Dynamics, home of the initial Triamese concept, was to study variants of this design, and would also apply its background to design a fully-reusable concept having only two elements rather than the three of Triamese.
There were at least five ways to build a fully-reusable shuttle, and NASA had appropriate designations and descriptions:
FR-1: the Triamese;
FR-2: a two-stage vehicle with the engines of both stages ignited at launch;
FR-3: a two-stage vehicle with engines in the orbiter ignited only upon staging (Faget's shuttle was an FR-3; so were the concepts of McDonnell Douglas);
FR-4: a variant of the Triamese with the core stage not of the same length as the twin booster stages;
FR-5: a concept designed to avoid a shift in its center of gravity as its propellant tanks would empty, thus easing problems of stability and control.
Unfortunately on September 4, 1969 another meeting eliminated the Triamese configurations. The initial concept, the FR-1, had called for three elements of common length and structural design. It had proven difficult, however, to have one shape serve both as booster and orbiter.
Richard Nau remembered all too well the pretty blunt opinion of Milton Silveira, the manager of the Space Shuttle Engineering Office
"The Triamese design quickly gets all screwed up, so you end with a lousy orbiter and a lousy booster, but you don't get one that does well." Advocates of the Triamese had turned to the FR-4, a variant with the core stage not of the same length as the twin booster stages. This, however, proved heavier than the FR-3, while requiring two booster elements rather than one. It also lost much of the potential cost saving from design commonality between the three elements.
Nau reminds that “The final report on the Triamese, dated May 7, 1969 actually recognized the inherent issues with the vehicle. We felt however we could pull that trick, build and fly our vehicle. The report said that
“In order to achieve the economy predicted for the Triamese system the orbital and boost elements must have a high degree of commonality and must represent essentially a single development program. This commonality has been obtained by "overdesigning" the boost elements. Commonality is best evidenced by examining the detail weights. Thermal protection designs for the booster and orbiter are common even though boost element environments are much less severe. The performance penalties for a high degree of commonality are accepted in the designs presented in this report.”
Yet we at General Dynamics were furious that NASA rejected the Triamese early on. We were troubled by Milton Silveira blunt analysis. After it was rejected out of hand late 1969 we put the Triamese on hold for some years – until late 1971 when we heard of the space shuttle cancellation.
We decided to renew studies on Triamese in the hope it might be picked up as a shuttle II design in the next decade.
Still troubled by Silveira analysis we got in touch with NASA Langley to try and refine the Triamese. There we found John Houbolt colleagues - the legendary engineer that in 1961 had fought NASA heavyweights to impose the Lunar Orbit Rendezvous mode for Apollo. Houbolt no longer worked at Langley; he had left in 1963 for a private company set in Princeton. But some of his colleagues remained, and we learned some fascinating hindsight on the LOR genesis and battle.
One of Houbolt former colleague (together they had written the seminal Guidance and Navigation Aspects of Space Rendezvous), John Bird had some exotic, intriguing shuttle concepts, what he called atmospheric rendezvous. He promoted the concept through Gene Love Vehicle Branch small group. The aptly-named Bird explored things like air-launching, towing, or even docking a pair of shuttles, if only to try and break the huge weight penalty all-rocket vehicles suffered from.
Unfortunately John D. Bird passed away on December 18, 1980. In 1976 however we interviewed him and he draw fascinating parallel between Suborbital Refueling and his Langley colleague John Houbolt battle for Lunar Orbit Rendezvous back in 1961.
John D. Bird (posthumously)
From 1959 onwards Langley researchers quickly began making lunar and planetary mission feasibility studies of their own. John D. Bird began designing different "lunar bugs," "lunar schooners," and other types of small excursion modules that could land on the surface of the Moon after departing a "mother ship." "Jaybird" (as Bird was called by his peers) became an outspoken advocate of the lunar-orbit rendezvous concept. When a skeptical visitor to Langley offered, with a chuckle, that lunar-orbit rendezvous was "like putting a guy in an airplane without a parachute and having him make a midair transfer," Bird set that visitor straight. "No," he corrected, "It’s like having a big ship moored in the harbor while a little rowboat leaves it, goes ashore, and comes back again."
Three days before President Kennedy's lunar commitment, John D. Bird, "Jaybird", captured Langley's enthusiasm for a moonshot in his sketch "TO THE MOON WITH C-1's OR BUST" (below). In essence, his plan called for a mission via earth-orbit rendezvous (EOR) requiring the launch of 10 C-1 rockets.
(quoted from John D. Bird)
“Knowing what we know now—that Americans would land on the Moon and return safely before the end of the 1960s, using the LOR method—it might be hard to imagine and appreciate the strength of feeling against the LOR concept in the early 1960s. In retrospect, we know that LOR enjoyed—as Brown, Michael, Dolan, and especially John Houbolt had said—several advantages over competitor methods. It required less fuel, only half the payload, and less brand-new technology In the early 1960s, however, all these advantages were merely theoretical. On the other hand, the fear that American astronauts might be left in an orbiting coffin some 240,000 miles from home was quite real. If rendezvous had to be part of the lunar mission, many felt it should be conducted only in the Earth’s orbit. If that rendezvous failed, the threatened astronauts could be brought back home simply by allowing the orbit of their spacecraft to deteriorate. But if a rendezvous around the Moon failed, the astronauts would be too far away to be saved, because nothing could be done. The morbid specter of dead astronauts sailing around the Moon haunted the dreams of those responsible for the Apollo program. It was a nightmare that made objective evaluation of the LOR concept by NASA unusually difficult. It was an amazingly tempestuous intellectual and emotional climate in which NASA would have to make perhaps the most fundamental decision in its history. It was a psychological obstacle that made the entire year of 1961 and the first seven months of 1962 the most hectic and challenging period of John Houbolt's life.
Well, two decades later very similar roadblocks stood in the way of suborbital refueling.
“There was a reluctance to believe that the suborbital rendezvous maneuver was an easy thing. In fact, to a layman, if you were to explain what you had to do to perform a rendezvous and propellant transfer during a suborbital parabola , he would say that sounds so difficult we'll never be able to do it this century. I'm not so sure we ever thought of suborbital rendezvous as very complicated. It's an amazing thing. We thought that if our guys could work out the suborbital mechanics and we gave the pilot the right controls and stuff, then he'd make the rendezvous. We didn't think it was very complicated.
There are many things in spaceflight that are counter-intuitive with their early advocates being mocked.
Lets just take two examples. First, Venus swingbys on the way to Mars, a manoeuver that saves a lot of propellants thanks to clever use of gravitation. But at first glance it looks absurd because you goes in the exact opposite direction from Mars – to Venus ! I had a friend in Langley, a bright astrodynamicist called Dana that got humiliated that way during a Mars gathering in the late 60's.
“Manned Mars stopover missions of duration twelve to twenty-four months are characterized by Earth return velocities of up to seventy thousand feet per second, over the cycle of mission opportunities. A promising mode for reducing Earth entry velocities to forty to fifty thousand feet per second, without increasing spacecraft gross weight, is the swing-by through the gravitational field of Venus. Studies indicate that this technique can be applied to all Mars mission opportunities, and in one-third of them, the propulsion requirements actually can be reduced below minimum direct-mode requirements…”
He hurried through the idea of gravity assist. He tried to emphasize the history and intellectual weight of the idea, showing that his own computations had built on the work of others. “The concept within NASA of using a Venus swing-by to reach Mars dates back to Hollister and Sohn, working independently, who published in 1963 and 1964. This was further elaborated by Sohn, and by Deerwester, who presented exhaustive results graphically in a format compatible with the direct flight curves in the NASA Planetary Flight Handbook…”
It was a little like a game of interplanetary pool, he said. A spacecraft would dive in so close to a planet that its path would be altered by that world’s gravitational field. In the swing-by — the bounce off the planet — the spacecraft would extract energy from the planet’s revolution around the sun, and so speed up; in exchange, the planet’s year would be minutely changed.
In practical terms, bouncing off a planet’s gravity well was like enjoying the benefit of an additional rocket stage at no extra cost, if your navigation was good enough.
“We have already studied the Mariner Mercury mission, which would have swung by Venus en route to Mercury. A direct journey would have been possible, using, for example, a Titan IIIC booster; but the gravity assist would have allowed the use of the cheaper Atlas-Centaur launch system…”
Example number two - how about that guy from JPL, Gary Flandro ? In 1965 he discovered a major planet alignment – Jupiter – Saturn – Uranus – Neptune – that made the Grand Tour (Voyager) feasible within the next three decades, but not thereafter, unless of course you are willing to wait 180 years.
Well, suborbital refueling was one of these counter-intuitive things.
Knowing what we know now—that thousands of ordinary people would fly in orbit and return safely, airliner-style, using the suborbital refueling (SOR) method—it might be hard to imagine and appreciate the strength of feeling against the suborbital refueling concept in the early 1980s.
In retrospect, we know that SOR enjoyed several advantages over competitor Single Stage To Orbit methods – airbreathing, air liquefaction, and very high mass fractions.
It required no brand-new technology – only aerial refueling, rocket engines, and turbofans. In the early 1980s, however, all these advantages were merely theoretical. On the other hand, the fear that passengers might be left crashing or burning through the atmosphere at mach 10 after a collision during refueling was quite real.
If aerial refueling had to be part of any orbital mission, many felt it should be conducted only at subsonic speeds. If that rendezvous failed, the threatened space plane could be brought back home by landing on the closest airstrip. But if a suborbital rendezvous failed because of a collision, death would result for both the tanker and the refueling ship. The Palomares aerial refueling disaster was in all memories – when a H-bomb loaded B-52 collided with a KC-135 and left few survivors.
The morbid specter of dead astronauts burning into the atmosphere at mach 10 haunted the dreams of those responsible for the SOR breakthrough. It was a nightmare that made objective evaluation of the SOR concept by NASA and the military unusually difficult. It was an amazingly tempestuous intellectual and emotional climate in which NASA would have to make perhaps the most fundamental decision in its history. It was a huge psychological obstacle that had to be overcome.
So I, John D. Bird, drifted from LOR to SOR within the span of a decade.
In 1971 NASA Langley and the Vought corporation carried out a study to determine the feasibility of using atmospheric rendezvous to increase the efficiency of space transportation and to determine the most effective implementation.
They concluded atmospheric rendezvous to be feasible. Two basic approaches were investigated for performing the rendez-vous and recovery tasks.
One approach considered use of a large airplane with which rendezvous occured after the orbiter has completed its hypersonic glide and has slowed to subsonic flight conditions.
The other approach was even more audacious, and of further interest for us. It involved use of a recoverable booster which may rendezvous with the orbiter at any speed up to its maximum burn outspeed. The booster would litterally catch the descending orbiter and bring it back to the ground.
Langley's data were prepared by combining reentry-glide comptations with booster launch characteristics based on North American Phase B Space Shuttle studies. They had elaborated the following scenario:
At booster lift-off, the orbiter is approximately 225 nautical miles up range from the launch site and at a velocity of about 13,000 feet per second (4 km/s). At booster apogee, the orbiter is approximately 50 nautical miles downrange from the booster and at a velocity of about 9,000 feet per second (2.7 km/s). Rendezvous occurs at a velocity of 5000 feet per second (1.5 km/s) and about 500 nautical miles downrange from the launch site.
Apogee for the booster is established by launch of another orbiter. Due to apogee being well above equilibrium glide altitude, the first booster overshoot of orbiter flight altitude cannot be avoided. It appears that rendezvous at speeds below 6,000 feet per second (1.8 km/s) can be accomplished by proper control of angle-of-attack. Rendezvous at higher speeds would be very difficult unless the booster launch trajectory were reshaped.
The booster is gliding at a higher speed and a smaller lift-to-drag ratio than the orbiter during the rendezvous flights. Therefore,the booster is continuously approaching from the rear of the orbiter. The relative altitude, however, is much less consistent for the case of rendezvous at 4000 ft/sec (1.2 km/s). This plot of relative altitude versus relative altitude rate shows that the variation is well behaved only during the final minute of rendezvous.
Booster launch occurs during the orbiter hypersonic glide. Therefore there must be some constraint on the launch time in order to rendezvous. A study was made to estimate this booster launch window restriction.
Booster launch time can be delayed if its flight time to rendezvous is decreased and/or if the orbiter flight time to rendezvous is increased. The orbiter cannot delay reentering since it is in the re-entry phase at the time of nominal booster lift-off.
The following two cases were considered for a rendezvous at 5000 fps
(1)booster flight was held fixed and orbiter maneuvers were used to increase the orbiter flight time to rendezvous and
(2) orbiter flight was held fixed and booster maneuvers were used to decrease the booster flight time to rendezvous.
In both cases,velocity and range at rendezvous were held constant. The nominal rendezvous is based on flight at average lift-to-drag ratios.
These data were calculated using equilibrium glide equations.
Assuming that the capabilities of these two cases are additive, it is concluded that booster launch window is aproximatively one minute. Some additional capability may be possible by considering a variable rendezvous velocity; however, it is felt that the launch window would remain rather small, because deceleration is relatively large at these speeds.
We decided to use the booster-orbiter data as a basis to try and fly Triamese elements separately, either two or four of them. They would either dock or refuel or both during atmospheric flight. We concluded that it somewhat remained a bimese except for the fact that we did the stage integration with a hose, and after launch. Mathematically, they were not so different.
We eliminated refueling in favour of docking because of the Triamese cryogenic propellants that made very hard to aerial refuel.
John Bird analysis of the Triamese concluded saying the staging inefficiencies were not as bad with this design as with bimese. The greater complexity of having one stage that could function as both a booster and orbiter would drive up the vehicle development structure cost, he said.
Then Bird suggested that, if amortized development cost could be reduced by using a trimese design, it was logical to ask if using even larger numbers of identical stages might result in even greater savings. We went from three to four vehicles, but not farther as the docking atmospheric ballet become way too complicated to manage.
That a former collegue of Houbolt discussed (atmospheric) rendezvous between two flying machines was hardly a surprise. Aerial docking was not dissimilar to in-space rendezvous, and Langley had specialized in the field in the Houbolt days. Little did we suspected at the time that the battle for suborbital refueling would be as hard fought as John Houbolt quest for Lunar Orbit Rendezvous back in 1960-62.
At this point in a fascinating discussion Max Faget reminded us once again about the sheer craziness of linking a pair of X-15 flying at hypersonic speeds. In response I noted that the X-15 not only flew fast, it also broke altitude records, up to 350 000 feet, to the edge of space. The speed and height flights had totally different profiles and trajectories, which were mutually exlusive; the X-15 never broke speed and height records during the same flight.
At this very moment I saw Richard Nau face changing. He just muttered "height, not speed..." then explained himself.
I was surprised and said: gimme a break. You are saying - whatif we tried that refueling, not at mach 6 but at 300 000 feet ?
Faget poked "Why not ? it can't be worse that hypersonic refueling."
In a most serious way I told Richard that out of the atmosphere there's no shock wave nor thermal heating, since both are the result of atmospheric friction. All the issues that made hypersonic refueling a suicide mission had just vanished without a trace ! I don't know what Faget thought about the concept, but that idea never totally left me afterwards. I did not spoke about it to the rest of the team, not immediately. It looked so outrageous; futhermore, it needed serious refining.
Before we left Richard Nau had this magnificent catchphrase about suborbital refueling
"This is not an attempt to solve the rocket equation problem by means of increasing specific impulse or cutting into the mass fraction - but by decreasing delta-V. "
That sentence also never left me afterwards.
Len Cormier
It all started with my Windjammer, long before the Alamogordo conference.
As of 1971 I was manager of North American Rockwell fighters division in Los Angeles. Once the best in the world, with marvels like the Mustang, Sabre and Super Sabre, it had lost steam. I was in fact more interested in space planes, and the Windjammer was the result of that interest – in my free time. But Rockwell was only interested in the shuttle, a project I didn't liked very much. I had the military nonetheless interested in the Windjammer – Bernard Schriever all powerful SAMSO ballistic missile organization.
In the end I found that Boeing was more interested than both Rockwell and the military itself, and then the shuttle was canned, with Rockwell so angered by the decision they bet all their money on the Apollo capsule rather than an hypothetical shuttle rebirth. I can hardly blame them for that decision. In the end the fighter / spaceplane, Boeing / Rockwell conflicts of interests cost myself my job. In 1972 I packed all and went to Boeing, where I met Andy.
Andy Hepler
Len Windjammer was the starting point of Boeing TAV (Trans Atmospheric Vehicle) very long, tortuous story. We first refined the concept internally, but in 1975 an interesting opportunity arose. NASA Langley had resumed work on the lost shuttle in view of a possible resurrection in the 80's. Lifting-body supporter Eugene Love had spun a small group out of Langley launch vehicle division, and they issued all kind of small contracts to aerospace contractors. We submitted them the Windjammer and further refinment followed, until 1978 (more on this later).
One has to realize that with Marshall dead and Houston entirely committed to Big Gemini and the space station, the shuttle last stronghold was the Langley Research Center, Hampton, Virginia.
So it was no surprise if they were literally flooded with space planes projects; our team was just one among others. During a trip to Langley I still remember a discussion with one of these outsiders. His name was Tony Du Pont, and he had his own vision of what the path toward a SSTO should be.
Du Pont had designed the podded scramjet dubbed the Hypersonic Research Engine that had literally melted on the X-15A-2 speed record flight on October 3, 1967. He had that design of a hypersonic vehicle, still with the podded scramjets on the underside. Gene Love later told me he didn't liked Du Pont design very much; the podded scramjets would produce more drag than thrust, so the vehicle would never accelerate.
In the end the Presidential committment to the shuttle was never coming - to NASA dismay. So we went to the military again, and once again they were enthusiastic. Meanwhile we were making excellent progresses in interesting Boeing top brass to the Windjammer. We were allowed to recruit more engineers, and that's how Gordon [Woodcock] and Dana [Andrews] joined the project. We also had general Bernard Schriever supporting the project, and Schriever brought us another bold recruit – Robert Salkeld.
Len Cormier
"By 1978 I visited John D. Bird at Langley. It was a singular meeting in a strange place. I passed Richmond and turned my car off Route 1 and onto the narrower State Highway 60, heading southeast. The towns were fewer, and smaller. And, at last, after Williamsburg, there seemed to be nothing but forests and marshland, and the occasional farmhouse. I could taste salt and ozone from the coast. At least I reached Hampton. It is a fishing town, a backwater. The Samuel P. Langley Memorial Laboratory is the oldest aeronautical research center in the U.S., and it is father to all the rest. It has been founded during the First World War, conceived out of a fear that the land of the Wright brothers might start to fall behind the European belligerents in aviation. Langley stayed poor, humble, and obscure, but it succeeded in keeping abreast of the latest technology. And back then Hampton is a place where people still referred to the Civil War as “the late war.”
The research center is a cluster of dignified old buildings, with precise brickwork and extensive porches, that looked almost like a college campus. But, set among the neatly trimmed lawns and tree-shased streets, are exotic shapes: huge spheres, buildings from which protruded pipes twenty or thirty feet wide. They are Langley’s famous wind tunnels.
Hampton is so isolated that a lot of bright young aeronautical engineers don’t want to come within a hundred miles of the place. Those who come to Langley tend to be highly motivated, and not a little odd. John Bird is one of them. And the local Virginians hasn’t thought much of the “Nacka Nuts” — as they still called them — arriving in their midst. So the Langley engineers have kept themselves to themselves most of the time, on and off the job, and Langley has evolved into its own peculiar little world.
Langley made immense contributions to the U.S.’s prowess in aeronautics and astronautics. It got involved with the development of military aircraft during the Second World War and then in the programs which led to the first supersonic airplane, the Bell X-1. Langley staff formed the task force which was responsible for the Mercury program, and later it became involved with studies for the optimal shapes for the Gemini and Apollo ships.
We didn't met a Langley but rather at Bird house. So I parked my car and there came John Bird in an old cardigan and with tie loosely knotted, wiping his hands on an oily rag.He tucked his tobacco pouch into the pocket of his shabby gray cardigan and told me
“Well, how’s about a little brain-busting, back in my workshop?”
The workshop, so-called, is actually a small unused bedroom at the back of the house, filled with tools and books and bits of unfinished models, a blackboard coated with obscure, unreadable equations. Bird cleared some loose sketches from a stool. His slacks were already coated with a patina of fine dust. Every surface is covered with scraps of paper, chewed-off pencils, shreds of tobacco, bits of discarded models. Bird began to bustle about the workshop, pulling together obscure bits and pieces from the clutter, sorting haphazardly. Bird puffed at his pipe as he worked.
“You know” he started, at some point in the history of astronautics there was a rupture, a divorce between aircrafts and rockets. Looking back to the early 50's it seemed that jets and rockets could be mixed for high performance interceptors. We flew Republic XF-91 and later the NF-104A. The French had the SO-9000 Trident. Great Britain build the Saro SR-53. The Soviets probably tried to add a rocket to a Mig-21.
“Thus by 1954 or so the path forward seemed to be an aircraft that would lift-off on jet power and then goes to orbit on rocket power. Intermediate steps would be aircraft flying suborbital parabolas, higher and higher, faster and faster, up to orbit. Although it lacked a jet engine (the B-52 carrier was the jet engine by itself), the X-15 showed the way.
Then, within the span of six years things took a brutal, different turn, with jets and rockets going their own separate ways.
By 1956 mixed jet / rocket interceptors were killed by progress in afterburners.
Then in 1957 the manned interceptor by itself was killed by the advent of surface-to-air-missiles (SAMs) that could shot bombers cheaper, faster and higher than any manned aircraft (Boeing BOMARC was the most extreme example of that trend).
Then in 1958 SAMs by themselves were shot down by ICBMs they couldn't intercept.
And then by 1959 ICBMs snowballed into expendable launch vehicles.
At this point the rocket plane fought a Gettysburg battle.
In 1961 through the X-20 DynaSoar it nearly managed a come back, only to be shot in 1962 by the ballistic capsules – Mercury, Gemini.
And then come JFK that send Apollo to the lunar surface and back.
“If only the Shuttle has gone ahead. “ Bird concluded.
I nodded in approval “Instead we are looking at more big dumb rockets like Titan III. More V-2s. Our great rockets, the Saturns of von Braun, work for only minutes, in a flight lasting days, and then fall to their destruction. It’s that crudity of such approach that galls me. Of course the Germans got a man on the Moon, but it’s not elegant, and not the Langley Way. More big rockets! Huh! Still not elegant enough for me.” Bird told me, half joking.
“Ok, thank you for the course in rocket and jet engines. You said that jets and rockets could have send a space plane in orbit. But the large mass of rocket propellants completely crushed any hope of going into orbit. The best jet-and-rocket aircraft you mention reached Mach 2.5. But orbital speed is exactly ten times that number, mach 25.”
“I know that”, Bird said. “It was obvious to us as early as 1960, during flight testing of the X-15 and development of Boeing X-20. Post DynaSoar strategy was to get ride of that cumbersome and expensive and dangerous Titan III, with the long-term goal of flying into orbit from the usual airport. Alas, the Air Force Aerospaceplane studies were a cold shower for us. Before we believed that the elegant thing to do was to rush and develope a smart engine – a scramjet, or an aerospike, or an air liquefaction gizmo which can really cut down the propellant mass, perhaps by sucking the atmosphere one way or another. But the Aerospaceplane showed that won’t come in my lifetime, and maybe not yours. Getting to mach 25 without throwing expendable bits along the way is a daunting challenge. Doing that for the usual airstrip is a nightmare.
“So where’s the room for elegance in all this?” I, Len Cormier, said. “It seems we’re kind of constrained by the laws of celestial mechanics. It’s either Hohmann, or brute force. We are living on a large rocky planet with a strong gravity pull, thus a steep gravity well. On top of that is that thick atmosphere. We would have much easier time on the Moon or even Mars.”
“Let me examine the mixed, jet-rocket aircrafts of the 50's. You said that propellant and jet engine mass would be way too heavy. Some different, breathrough engine would have to fill the gap. But they had weight and complication. Now there is a different technology that was also developed in the 50's. I mean – aerial propellant transfer. Boeing build two thousands air tankers for the military – converted B-29s and KC-97s and KC-135s.”
“Here we are.” I smiled. “That's the reason we need you, John. We want to explore a path not taken – aerial refueling or docking. We do know that in 1972 you, Langley and Vought issued a small research paper. We need Langley knowledge of the mechanics of rendezvous. Houbolt did it for Lunar Orbit Rendezvous. We want you, John Bird, to achieve a similar result for suborbital rendezvous, docking, or propellant transfer.” John Bird smiled and shook my hand. “I'll do it. You can count on me and my fellow Langley rocket scientists.” During another visit some months later Bird introduced me to Langley best engineers, among them was James A. Martin, who dreamed of “orbit on demand” vehicles.
Robert Salkeld
In 1970 Schriever had written a foreword to my book War and space; we knew each others since the DynaSoar days.
Andy Hepler
Since I had also worked on that program (from the Boeing side of the fence) it made Salkeld all the more sympathetic to me.
Gordon Woodcock
As fixed in 1976 by the Strategic Air Command the RASV operational requirements were damn hard. RASV stands for Reusable Aerodynamic Space Vehicle. The SAC wanted the vehicle to reach standby status within 24 hours from warning. Standby to launch shall be three minutes. They heavily insisted on “aircraft-like operations” and incremental testing of the vehicle through the various flight regimes. The craft also would have the ability to abort when one of its two engines ceased to function. The design would require minimal checkout at the launch facility with maximum on-board autonomy and maximum use of an on-board checkout computer system for preflight and postflight operations.
Dana Andrews
In many ways, ground crews would handle the RASV like a B-52. It would be serviced in a B-52 hangar, and an engine could be changed in hours rather than weeks. The RASV would use a flight control tower, not a launch control center and the pilot would make the decision when to launch. Also, the cockpit would look like that of an aircraft, and the pilot would fly it as if it were an airplane. Crew would load payloads from the bottom, not from the top. However, the only operations or maintenance issue addressed by the feasibility study in any detail was that of rapid refueling.
Refueling would have to take place in thirty minutes - which is beyond the limits of available cryogenic technology. To solve that issue we suggested in 1977 that the RASV carried liquid helium to purge and repressurize its fuel tanks. This solution eliminated the need to purge the tanks on the ground, but add further complexity and cost. Non cryogenic propellants were a simpler answer.
Len Cormier
I have to recognize that the Windjammer hardly met these requirements. Early on - circa 1973 - it was to be powered by the very high performance XLR-129 - the space shuttle lost engine.
Even with the XLR-129 high performance however the mass of liquid oxygen and hydrogen is so huge no undercarriage could withstand it. Thus Boeing would have had to develop a sled to accelerate the Windjammer to a speed of 600 feet per second. And a 747 would have to transport the Windjammer back to its launch site, in case of an abort or a forced landing at a site not equipped with a sled launcher.
All this was hardly satisfying.
Undaunted, and with strong support from Boeing top brass, we faced the challenge. We also had results from the Langley studies.
We first attacked the cryogenic issue. As Dana said, the RASV very fast turnaround was beyond the limit of cryogenic technology. The helium purge was dropped as cumbersome and heavy. On top of that we learned that the XLR-129 was in trouble per lack of funding. It was the moment when Andy Hepler had this stroke of genius.
Andrew Hepler
During the Langley studies we had briefly considered the concept of in-flight fueling of the space plane, if only to relieve the undercarriage of the burden rocket propellant is.
The idea actually was Robert Salkeld brainchild. Much like Cormier Windjammer (or perhaps even inspired by it !) Salkeld initial space planes were sled-launched. But a launch sled is a pretty complicated piece of hardware, and it obviously restrict the number of launch sites. Salkeld suggested inflight fueling as an alternative to the sled.
In March 1974 Salkeld published a seminal paper entitled Single-Stage Shuttles for Ground Launch and Air Launch. It had a big impact on the space plane world, to the point Gene Love and James Martin Langley group got money from NASA headquarters for further studies.
Liquid oxygen by itself represented an immense mass of hundreds of tons. Unfortunately inflight transfer of cryogens proved to be pretty difficult; the tanker aircraft was far beyond a Boeing 747, and Salkled (later followed by Langley) dismissed the concept as technologically immature.
Two years later however I decided to revisit the idea if only because the RASV rocket sled was unacceptable to the military. By contrast they had no issue with inflight refueling, and, having worked on Boeing bombers and tankers back in the 50's, I also had favorable experience with the concept. So I gave inflight refueling a second thought, only for the same results found by Salkeld in 1974 and Langley in 1977 – the tanker was truly huge, and the cryogens made inflight transfers extremely complicated. I was nevertheless ready to try my hand at that big tanker, seeing it as preferable to the cumbersome sled. But fate decided otherwise: our little team learned that the XLR-129 was in trouble, and we had little options beside that (J-2 lacked performance, RL-10s were too small).
Meanwhile in 1979 further impetus for a hypersonic research aircraft – much like the RASV - come from a different side of the Air Force. Up to this point of time we had backing from SAMSO and SAC. Then General Lawrence Skantze at Aeronautical System Division at Wright Patterson AFB, Dayton, Ohio ordered a review of NASA Shuttle II projects (notably those from Langley Research Center) to see if any of them was of interest for the Air Force. In 1982 Skantze become Commander of Air Force System Command. He initially pursued a project known as Trans-Atmospheric Vehicle. Soon however Skantze learned of Boeing ungoing RASV project and changed his mind.
Len Cormier
At this point, someone in the team (can't remember who) suggested we drop LOX/ LH2 altogether in favor of non-cryogenic engines, for example the plain old Atlas or Delta LOX/kerosene workhorses. I rehashed the tanker option and discovered that without the cryogens inflight refueling was far easier.
So we switched the Windjammer to LOX/kerosene with kerosene transfer, (we discovered later that Gordon Woodcock had had a similar idea for his own flyback F-1 booster!) but once again it was the LOX - the oxidiser - that represented the bulk of propellant mass. A liquid only at 183 degree minus zero, it was pretty impossible to transfer oxygen in flight.
I thus sought a different oxidiser, and truth be told there was not many of them - N2O4 from the Titan rocket was toxic and quickly eliminated, leaving only two dark horses: nitrous oxide (N2O) and hydrogen peroxide (H2O2). The two were quite similar; H2O2 had a bad reputation of explosivity and instability, but was liquid at room temperature and provided a better specific impulse. N2O was midly cryogenic, although a little pressure would make it liquid at room temperature like hydrogen peroxide. It was a difficult choice: the British had aparently mastered H2O2 for their space program, but the nascent hybrid rockets (and there was a lot of interest for that technology) burned their solid fuel with N2O.
In the end we decided to go the N2O way; there were a lot of enthusiastic young rocket engineers working on hybrid rockets, people like Gary Hudson and George Koopman. They placed safety above anything else, and when we talked about flying out of ordinary airports, they strongly suggested N2O was a much reasonable choice than H2O2. By contrast, at a later date British experience with hydrogen peroxide had the Europeans picking up that oxidizer. In the end we had the early X-30s flying with N2O but later marks of Orion switched to H2O2. Even today Orion variants exists with both oxidizers.
Andrew Hepler
I think the Europeans had a veteran British rocket scientist - what was his name ?
Len Cormier
David Andrews, I believe
Andrew Hepler
That's his name, and he had this to say
"The greatest danger in the use of hydrogen peroxide is likely to arise from the fact that it appears so safe. Nine times out of ten, if something goes wrong, nothing much happens. Danger arises if one becomes blasé in consequence: every so often one is sharply reminded that it is a strong oxident which must be treated with respect. This means, however, that provided safe practise is followed at all times, HTP is very safe indeed."
That's a point of view that could be discussed endlessly.
Len Cormier
We did not totally excluded a return to liquid oxygen someday, but the transfer technology was immature and, most importantly, the mixture ratio was not the same at all. The amount of liquid oxygen to be burned with kerosene is far superior (66 to 33) to N2O or H2O2, the last two being somewhat equal for that matter - 87 to 13. If that sounds cryptic, consider that, for a propellant mass of 100 tons, H2O2 or N2O would represent 87%, leaving only 13% of kerosene. Which in turns makes the space plane extremely light when flying on the turbofans, I mean with the rocket oxidizer tank empty.
Gordon Woodcock
A typical Windjammer mission would be: lift-off on turbofan power, climb to 30 000 ft, top the rocket oxidiser tank from the tanker, disengage, light the rocket, and fly into space (either into suborbital with a kick-stage, or into orbit with the improved mass fraction machine). That was it. The turbofans gave the TAV tremendous flexibility for lift-off, landing and ferry flights.
Non-cryogenic propellants and inflight fueling were major breakthrough – but still not enough by themselves to reach SSTO performance; even with a subsonic refueling the Windjammer mass fraction remained tricky. We suggested the main aircraft never reached orbit, with the payload boosted by a kick stage, perhaps a solid-fuel Star 48 or even an Agena. But the military wanted an orbital machine (and so wanted NASA – there was no way their beloved shuttle stuck to suborbital flight !) Anyway we proposed both concepts to the military. Obviously their opinion was that the suborbital machine was not acceptable; and we were pretty confident we could reach the desired mass fraction.
Len Cormier
As Gordon said – we were confident. Unfortunately over time the TAV underwent changes in the face of new performance requirements. Early in the program life technical requirements for the Trans Atmospheric Vehicle were as follow.
The TAV would be capable of flying 500 to 1,000 times with low-cost refurbishment and maintenance as a design goal from a launch site in Grand Forks, North Dakota, into a polar orbit, or once around the planet in a different orbit, and and would be capable of carrying payloads up to 10,000 pounds (4,536 kg) and no larger than 10 feet by 15 feet (3.0 m by 4.6 m).
One could ask why that precise location - Grand Forks, Dakota ? Well, it is hardly a coincidence that the Safeguard nuclear ABM system only station was located there. The RASV was to support the Safeguard ABM system one way or another.
It now had to be capable of carrying heavier loads into orbit, 30,000 pounds once around the globe from any launch site, though most likely from the central continental United States. I told the rest of the team “we are in trouble.” Even with the addition of inflight fueling and non-cryogenic propellants (which greatly improved the Windjammer aerodynamics, reducing drag losses during ascent) the TAV payload to orbit was a mere 8000 pounds. The suborbital / kick stage variant was hardly better.
Andy Hepler
Although its payload capability seriously lagged behind the requirements, our TAV nonetheless matched a lot of Schriever stringent requirements.
- Standby to launch shall be three minutes.
- ground crews shall handle the TAV like an aircraft.
- It shall be serviced in a B-52 hangar
- an engine shall be changed in hours rather than weeks.
- incremental testing of the vehicle through the various flight regimes
- use of a flight control tower, not a launch control center
- maximum on-board autonomy
We achieved this through use of simple engines. The Windjammer was to be powered by a pair of proven turbofans and a non-cryogenic rocket engine. No scramjet, no high-pressure LOX/LH2 rocket, no carrier aircraft, no ground-sled. No launch pad either.
Dana Andrews
Andy nailed it perfectly. The military definitively liked some of our space plane characteristics. Some said they would easily trade orbital performance and payload for the flexibility Andy highlighted.
At first glance it looked as if inflight refueling might degrade a space plane flexibility, since a tanker would have to be deployed along it. We realized however that the TAV was no worse than the SR-71 which leaking fuel tanks forced an inflight refueling immediately after take-off. The Air Force tolerated that serious issue in exchange for the Blackbird tremendous performance.
Len Cormier
Back to Maxwell Hunter. At the time of the Alamogordo conference he was deep in Lockheed bid for the space telescope; thanks to him the company won the contract late July 1977. Hunter was moved to the post of Agena applications manager.
From 1978 we got in touch with Hunter and he in fact defined a broad strategy. In the beginning he was skeptical of suborbital refueling; he was wary of the payload to orbit and of the trajectory to be flown.
He warily told us the military opinion would be even worse than his one. Our informal group – tentatively called the Orion arm - needed a stepped strategy. Hunter suggested we ask the military funding for a single, suborbital prototype and to connect that with (his) growing Agena business. He felt we should position that machine on two peculiar missions.
Missions one was a successor to Scout of course, but also Thorad, Atlas-Agena and Titan IIIB Agena – the medium launchers that lofted no more than 10 000 pounds.
Mission two was successor of Lockheed SR-71 – Hunter suggested we get in touch with Bernard Shriever and discuss the ISINGLASS hypersonic reconnaissance aircraft.
Hunter felt a demonstration of space plane refueling might be useful. Since 1976 NASA was flying a pair of piloted subscale shuttle models powered by XLR11 rocket engine.
Andy Hepler suggested to load a tank of propellant aboard a cargo aircraft and try to refuel one of these shuttle models at subsonic speed. Hunter suggested two demonstration missions involving the subscale shuttles. First a subscale shuttle should refuel from a subsonic tanker, either a modified KC-135 or a transport aircraft as per Hepler suggestion. The other mission had the two subscale shuttles zoom clibing to 80 000 feet and refueling each other in a suborbital parabola. Perhaps, Hunter suggested, we could scrap some money from DARPA to test that, Hepler said. It was a typical DARPA job: test a crazy idea on the cheap and secretely so that if it doesn't work, no taxpayer would complain...
(...)
Andy Hepler
I did not fully realized it at the time, but our project somewhat restaured an opportunity lost on December 10, 1963 - the day secretary of defence Robert McNamara cancelled Dyna Soar.
Dyna-Soar had a lot to offer the Air Force and the nation and might have changed history. The military might have benefited economically by possessing the world’s first reusable orbital vehicle, and in 1971 the Pentagon would not have been forced to become NASA’s political ally in the space agency’s (failed) political struggle to win funding for its Space Shuttle program. The knowledge gained from the research program, which included over 14,000 hours of wind tunnel tests, could have been applied to a number of applications from glide bombers to future spacecraft.
Whatever, after termination of the program, Boeing carried out a small “X-20 continuation program” for several more years that involved testing various DynaSoar components and design features both in ground facilities and on flight research vehicles. The René 41 high-temperature nickel alloy developed for the X-20 reappeared in the 1970s as part of the airframe structure and heat shielding for Boeing’s Reusable Aerodynamic Space Vehicle (RASV) that of course led to Orion. So is a clear filiation all the way from Sanger to Dynasoar and then to Orion. How about that."
