Launch. Land. Repeat: A history of the VTVL Rocket – Part 3

“I know how to get the U.S. permanently into space. Write me a check for a billion dollars, give me a letter of credit for a second billion I probably won’t have to spend, and get out of the way. I’ll take the money and vanish into the Mojave desert, China Lake for preference, Edwards Air Force Base if I must; and in about four years I’ll have a Single Stage to Orbit savable as well as recoverable and reusable spacecraft capable of putting about ten thousand pounds into orbit at costs of about five times the cost of the fuel the flight takes.”

This quote from and sci-fi author and aerospace industry veteran Jerry Pournelle dates to the early days of what would later become the DC-X. Pournelle was one of many space enthusiasts actively lobbying for a small SSTO project with minimal organisational oversight. As seen in Part 2, the DC-X project found it’s ‘Skunk Works’ home in the Strategic Defence Initiative Organisation (SDIO), but Pournelle’s words turned out to be prophetic – they would just take a while to happen and the innovators behind these projects would be able to write their own billion dollar cheques…

Even as the DC-XA programme was drawing to a close and facing up to disappointment with the vehicle’s destruction and NASA’s X-33 decision, one of the project’s key instigators, Gary Hudson, had moved on to his next project.

Spinning towards space
Hudson still believed there was great potential in a small, lightweight SSTO design and as he had throughout his career, he wasn’t afraid to consider radical ideas. One such concept came to him via an engineering associate, Bevin McKinney, who had been considering using rocket-tipped rotor propulsion to lift a craft up through the atmosphere. The action of the spinning rotors would also be used to pump the propellants saving weight by removing the need for turbo pumps  – a key consideration in SSTO designs. The rotors would then be used to provide braking during re-entry before bringing the vehicle to an accurate helicopter style landing. Though initially sceptical, Hudson soon became convinced of the approach’s merits and he and McKinney formed the Rotary Rocket Company in 1996 to work on the concept, now christened Roton.

Inspired by the Orteig Prize for the first nonstop flight between New York and Paris claimed by Charles Lindbergh in 1927, American entrepreneur Peter Diamandis founded the XPRIZE in 1996. This was a $10-million award for the first team to demonstrate an ability to fly a vehicle capable of carrying 3 passengers above the Kármán Line ( an altitude of 100km – the internationally acknowledged boundary of space) twice within a two-week period.

While Roton in its original form was a relatively small vehicle with extremely limited payload capacity to LEO, the vehicle would have been capable of performing the XPRIZE mission. While Hudson and Bevin had originally considered competing for the award, at the request of investor Walt Anderson they decided not to enter the competition. Instead they saw a commercial future for Roton in an emerging communications satellites market driven by new companies Iridium and GlobalStar.

These companies planned to place constellations of relatively small comsats in LEO to provide global phone coverage. Their need for rapid, reliable and affordable orbital access seemed a good opportunity for a vehicle like Roton – an extension of Hudson’s plans for his previous Phoenix family of SSTOs (see Part 2 HERE) – but the new mission would dictate a redesign of the vehicle to accommodate the larger payload and make the flight profile possible.

The redesigned Roton had a very different appearance to its earlier incarnation – a conical shape far more reminiscent of the DC-X with the rotor head now located at the top of the craft. Whereas the original design had used the rotors to provide lift for the ascent to orbit, the new design featured an ingenious RocketJet rotary aerospike propulsion system consisting of 72 thrust chambers located around the base of the vehicle. This ring of thrusters would rotate rapidly, the motion also providing the pumping action for the kerosene propellant. The rotors would now be used as a braking system, deploying prior to the reentry burn and beginning to rotate powered by the blade-tip rocket motors once the vehicle reached the lower atmosphere, bringing Roton to a controlled landing back at base. A payload to LEO of approximately 6000 pounds would be located in the mid mounted payload bay just above the cockpit housing a two-person crew.

The new design was technically extremely challenging, relying as it did on a number of new propulsive technologies and a water-based heat shield system, but Rotary Rocket remained outwardly optimistic about Roton’s prospects, attracting investors including novelist Tom Clancy. Construction soon began on a $2.8 million full scale atmospheric test vehicle (ATV) to prove the airworthiness of the craft under rotor power. Scaled Composites produced the composite aeroshell for the ATV as they had for the DC-X and the vehicle was rolled out at Rotary Rocket’s Mojave base on March 1st 1999.

Soon though, problems loomed on Roton’s horizon. By the summer of 1999 Rotary Rocket were forced to abandon their plans for the RocketJet propulsion system having been unable to convince investors that the cutting edge technology could be mastered. Instead they turned to the Fastrac engine, then under development at NASA’s Marshall Centre. Around the same time, the ATV began a series of low altitude test flights at Mojave but proved to be anything but stable or controllable.

Worse was to come though for Roton though. The market for small comsats collapsed as constellation providers failed to secure funding and went bankrupt. Hudson moved on from Rotary Rocket – later describing the latter stages of the venture as a ‘Trainwreck’ – and soon the company folded.

A new generation takes up the challenge
During the early years of the new century, while Roton was beginning to founder and other companies eyed the XPRIZE, VTVL rocket flight gained new impetus thanks to the Lunar Landing Challenge (LLC). With a prize fund provided as part of NASA’s Centennial Challenges Program and sponsorship from Northrop Grumman, the challenge was run for four years from 2006-9 initially as part of the XPRIZE Cup. Competitors needed to fly a rocket vehicle on a round trip between two launch areas demonstrating controlled vertical takeoff and landing as well as guidance between the points. The competition had 2 levels with Level One using a simple marked landing area and Level Two using a simulated lunar surface. While a number of teams competed in the LLC over its four years, only two companies managed to successfully complete their two-leg flights.

Founded by John Carmack in 2000, Texas based Armadillo Aerospace hoped to develop a vehicle capable of suborbital tourist flights, but for the LLC they initially developed smaller specialised vehicles. During the first two years of the competition, Armadillo were the sole competitor but were unable to complete a successful two-leg flight on either occasion. In 2008, although they initially faced competition from Chicago’s TrueZer0 they were able to successfully complete the Level One challenge.

In 2009 Armadillo Aerospace had far stronger competition from Mojave based Masten Space Systems. Founded by David Masten in 2004, they entered their Xombie vehicle for Level One and Xoie for Level Two. Both vehicles would take prizes with Zombie taking second place and Xoie beating Armadillo’s MOD vehicle to a narrow victory in the Level Two competition.

Masten Space Systems would take their successful designs beyond the LLC and have since developed a whole family of VTVL vehicles. In 2010 they were able to successfully demonstrate an impressive in-air relight capability with Xombie, an achievement that caught the attention of a certain Elon Musk who figured if a small team in the Mojave could get results like this, surely his company SpaceX could achieve similar…

Back in 2001 South African born entrepreneur and Pay Pal co-founder Musk began looking for ways to pursue his ambitions of creating a human colony to Mars. Initially Musk had hoped he could purchase existing launch vehicles, but following a series of abortive negotiations with Russian booster manufacturers he decided he could best realise his vision by forming a new company. Space Exploration Technologies Corporation – more commonly known as SpaceX – came into being in June 2002.

Musk’s logic behind the decision to go it alone was that by bringing his understanding of markets and materials to the manufacture of launch vehicles and adopting a model of reusability rather than the existing expendability, he could sufficiently reduce the cost of orbital access to a point where martian expeditions could be feasible.

To do this he gathered a wide breadth of expertise and set about creating everything he needed in-house, but this approach was not without its risks. SpaceX would need to master many new techniques in the construction and operation of space systems and do so in a relatively short time. Musk felt the best way to do this was to begin with a ‘smallest useful orbital rocket’ which, inspired by the Millennium Falcon, he named Falcon 1. This rocket would develop and prove key technologies such as the Merlin engine which could then be directly transferred to larger rockets. This modular approach relying on a commonality of components across vehicles would become a central characteristic of SpaceX’s developing plans. In September 2008 a Falcon 1 became the first privately funded liquid fuelled rocket to reach orbit – SpaceX were on their way, but Musk wasn’t the only internet entrepreneur with his eyes turned towards the stars.

Jeff Bezos, founder and CEO of eCommerce powerhouse Amazon, had been interested in space from an early age and the now wealthy entrepreneur saw an opportunity for a meaningful commercial presence in orbit. In 2000 Bezos founded Blue Origin and began to quietly acquire land rights in Texas. Having been impressed by what he’d seen of the DC-X, Bezos set about plans to develop a vertical takeoff, vertical landing rocket capable of providing the sort of cheap, routine orbital access his predecessors had strived for since the dawn of the space age.

Following their company motto “Gradatim Ferociter” (Gradually Ferocious), Blue Origin set about constructing a series of proof-of-concept prototypes, beginning with the jet-powered Charon in 2005 followed closely by the rocket powered Goddard in 2006. These early vehicles were essentially analogous with the DC-X providing operational experience and demonstrating the low level characteristics of a VTVL vehicle. With these early tests successfully negotiated the company then moved on to the full-scale New Shepard  suborbital vehicle consisting of a booster and detachable crew capsule. New Shepard, named in tribute to America’s first astronaut Alan Shepard, would be capable of boosting the capsule on a parabolic arc above the Kármán Line. The capsule would then return to a soft landing under parachutes while the booster would descend rapidly before relighting its BE-3 engine to reduce velocity prior to extending its landing legs and performing a controlled vertical landing on a pre-designated pad.

‘Old Space’ lends a hand 
As both Blue Origin and SpaceX continued to refine their technologies it was clear that both companies would require external impetus, and more importantly funding, to push their key technologies. Having announced an intention to retire the Space Shuttle in 2010, NASA were now looking for a means to meet the logistical needs of the ISS. To this end they announced a number of initiatives under the banner Commercial Orbital Transportation Services (COTS) to allow commercial providers to compete for cargo and crew resupply missions.

SpaceX put forward their Falcon 9 rocket with the Dragon capsule for the cargo resupply mission and were successful in gaining the contract – a valuable vote of confidence from NASA at a time when early failures with Falcon 1 were putting the company’s finances under pressure.

Blue Origin also looked towards NASA contracts, joining SpaceX in pursuing a Commercial Crew Development (CCDev) contract to ferry crews to and from the ISS. This process began in 2010 and while ultimately unsuccessful in the third phase of this process, Blue Origin’s participation had provided a source of funded development and built experience vital to their future plans. SpaceX were again successful, this time with a crewed variant of their Dragon capsule.

Reusability becomes a reality
Even as Blue Origin and SpaceX competed for lucrative NASA contracts, both companies retained their focus on a central element in both of their development plans – the successful demonstration of booster recovery.

For SpaceX this meant the creation of an atmospheric test vehicle, Grasshopper, which began a series of test flights at their Texas test site in 2012. Initially just short hops, Grasshopper eventually managed a flight duration of 79 seconds reaching a maximum altitude of 2,440 ft. With confidence in their ability to conduct the final powered descent, SpaceX now produced the larger F9R Dev to gain experience with a full size Falcon 9 first stage.

Flight testing of the F9R Dev began in April 2014 and three successful test flights were made allowing the retractable landing legs and new steerable grid fins to be tested before a fourth flight in August that year led to the controlled destruction of the vehicle following sensor anomalies.

Alongside the F9R Dev flights, SpaceX also conducted a series of descent tests using Falcon 9 boosters during operational flights beginning with Falcon 9 Flight 6 in September 2013. These tests were largely successful in demonstrating precision, vertical, low velocity landings from a variety of launch trajectories. Given the success of these tests a decision was made not to move forward with a second F9R Dev vehicle, but to move straight to landing attempts on an Automated Spaceport Drone Ship (ASDS).

The first attempt to land a Falcon 9 first stage core on an ASDS was made on January 10th 2015, but ended in failure after the steerable grid fins exhausted their hydraulic fluid supply just prior to landing resulting in what Musk euphemistically referred to as a ‘rapid, unscheduled disassembly’. A similar fate awaited the returning first stage core of Flight 17 (during the CRS-6 mission to resupply the ISS). While SpaceX were getting close to nailing a landing, a major setback during launch now forced the programme into hiatus. On June 28th 2015 a Falcon 9 carrying a Dragon capsule to the ISS for the CRS-7 mission exploded 2 minutes, 19 seconds into the flight due to a failure in the upper stage.

While SpaceX carried out investigations and worked out the problems in the Falcon 9, Blue Origin moved forward with their tests on the suborbital New Shepard. A first test flight of the system on April 29th 2015 had also resulted in a vehicle loss – while the capsule was recovered under parachute, the booster suffered a hydraulic failure resulting in an uncontrolled descent and subsequent crash.

Success at last
Undeterred by the loss of their first vehicle, Blue Origin carried out a second test flight on November 20th 2015 with far more success. Both elements of New Shepard were recovered with the booster returning to a soft landing following a flight to an altitude of 100.5 km. This marked the first occasion a booster had successfully carried out a vertical takeoff and landing on a mission exceeding the Kármán Line.

SpaceX responded in kind on Falcon 9 Flight 20 on December 21st, 2015 when a Falcon 9 first stage was recovered to a controlled landing at one of SpaceX’s recovery pads at Cape Canaveral having successfully launched a payload of 11 Orbcomm-OG2 satellites.

So, within a period of just over a month, 2 commercial space companies had demonstrated the ability to launch and recover VTVL rockets. Many comparisons were made between the 2 missions in the press and social media with Bezos and Musk uncharacteristically trading words on Twitter. In reality, there was a great deal of difference between the size of the vehicles, the velocities involved and what SpaceX and Blue Origin’s were aiming to achieve, but both were undoubtedly technically impressive feats.

The safe recovery of boosters was only part of the challenge though. If this was truly to be the start of a new age of reduced cost access to space, the second part of the challenge needed to be met – demonstrating reusability. Blue Origin have since successfully carried out a series of additional tests with Bezos describing the checkout and refurbishment between flights as costing in the order of tens of thousands of pounds. While still some way from the aircraft-like operations dreamt of by Bono or Hunter, New Shepard certainly seems to be moving towards a point where sub-orbital operations can become regular and reliable, offering a new adventure for would be astronauts and low cost flights for microgravity experiments.

In September 2016 Bezos revealed plans for Blue Origin’s next generation rocket, the New Glenn. While technical specs for the new booster have been hard to come by, two configurations were shown, both featuring a large reusable first stage modelled on the New Shepard and featuring the company’s upcoming BE-4 engines. It seems likely that New Glenn will be able to compete with SpaceX’s Falcon Heavy and ULA’s Delta IV Heavy in terms of payload size. Bezos has also teased that the company is working on another project named New Armstrong, but would only say that this was “…a story for the future.”

SpaceX meanwhile was able to demonstrate recovery at sea on Flight 23 which launched the CRS-8 mission to the ISS on April 8th 2016. While Musk had stated that the first recovered core from Flight 20 would not be reflow following static testing, it is expected that this second core will re-fly soon but the August 2016 explosion of a Falcon-9 on the pad during fuelling tests has caused significant delays in SpaceX’s schedule and pushed the debut of the Falcon Heavy, featuring 3 recoverable Falcon-9 cores, into 2017.

With his current rockets temporarily grounded, some wondered what this would do for Musk’s long stated martian ambitions, but as promised he unveiled his vision for martian colonisation during September’s 2016 International Astronautical Congress in Mexico. SpaceX’s colossal Interplanetary Transportation System features a huge reusable booster sporting no less than 42 of the company’s raptor engines. Musk claims that using the experience gained from Falcon 9 landings, this will be capable of making accurate landings back on the launch pad!

A final word for DARPA
One other notable current project is DARPA’s XS-1 Two Stage To Orbit (TSTO) launch system. Having been announced in November 2013, the XS-1 is an attempt to demonstrate a rapid, reliable means to deliver small satellites to orbit thorough the use of a recoverable first stage and an expendable second stage booster.

In many ways the XS-1 represents an evolution of earlier projects such as the DC-X, perhaps not coincidental as the project is managed by Jess Sponable who played a key role in the DC-X’s flight test programme at White Sands in the mid 1990s.

Three companies, were awarded design contracts for a demonstration vehicle in July 2014 including Masten Space Systems. While other entrants have proposed spaceplane designs Masten, using their huge knowledge of VTVL rocket systems including their earlier experiences in the LLC, have revealed a design named Xephyr which is outwardly reminiscent of McDonnell Douglas’s DC-Y and X-33 proposals. The XS-1 process is entering Phase II with the aim of creating a vehicle capable of carrying out 10 flights in 10 days – truly aircraft-like operations!

Conclusion
Until both Blue Origin and SpaceX have demonstrated an ability to recover and refly their boosters on a routine basis, the jury will remain out as to the financial implications VTVL rockets will have on the global launch market, but if they are successful in their plans it seems likely to significantly alter the launch paradigm driving other providers further towards reusability in order to reduce their launch costs accordingly. It is certainly notable that in Blue Origin’s New Glenn and SpaceX’s ICT we’re now looking at two of the largest planned boosters both featuring reusable VTVL first stages.

At a time when NASA seem content to repeat the mantra that the Shuttle proved reusability didn’t work, we may at last be about to see a new generation of launch vehicles reach maturity and demonstrate that the logic behind that statement is flawed. The shuttle simply proved that one approach to reusability – an approach hamstrung at its design stage by budgetary constraint and conflicting requirements – didn’t work. To draw wider conclusions seems somewhat rash, but given the pressure NASA managers are under to deliver the latest incarnation of congress’s preferred ‘big booster’, the SLS, maybe their reticence to acknowledge other options is understandable.

While New Shepard and Falcon 9 may be a world away from Philip Bono’s Pegasus or Icathus SSTO vehicles, the dream of lowering the cost of access to space remains the same – hopefully recent events point to that dream becoming slightly more achievable in coming years.

Part 1 of this article can be found HERE

Part 2 of this article can be found HERE

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Sources
The ROTON Concept and its Unique Operations – Gary C. Hudson

Realizing Tomorrow: The Path to Private Spaceflight – Chris Dubbs, Emeline Paat-Dahlstrom

Single Stage to Orbit: Politics, Space Technology, and the Quest for Reusable Rocketry – Andrew J. Butrica

History of the Phoenix VTOL SSTO and recent Developments in Single-Stage Launch Systems (1991 report) – Gary C. Hudson

Behind the curtain: Ars goes inside Blue Origin’s secretive rocket factory – Eric Berger (Ars Technica, March 9 2016)

Insanely Great? or Just Plain Insane? – Gary C. Hudson (WIRED, May 1996)

The Rocket Man Who Wants To Beat the Billionaires – Joe Pappalardo (Popular Mechanics, November 2015)

Blue Origin and SpaceX websites

Thanks to Jonathan Goff for additional information on Masten Space Systems