Douglas SASSTO

Last updated

Douglas Aircraft's SASSTO, short for "Saturn Application Single Stage to Orbit", was a single-stage-to-orbit (SSTO) reusable launch system designed by Philip Bono's team in 1967. SASSTO was a study in minimalist designs, a launcher with the specific intent of repeatedly placing a Gemini capsule in orbit for the lowest possible cost. The SASSTO booster was based on the layout of the S-IVB upper stage from the Saturn family, modified with a plug nozzle. Although the SASSTO design was never followed up at Douglas, it is widely referred to in newer studies for SSTO launchers, notably the MBB "Beta" (Ballistisches Einstufiges Träger-Aggregat) [1] design, which was largely an updated version of SASSTO.

Contents

History

In 1962 NASA sent out a series of studies on post-Apollo launch needs, which generally assumed very large launchers for a crewed mission to Mars. At Douglas, makers of the S-IVB, Philip Bono led a team that studied a number of very large liquid-fueled boosters as a way to lower the cost of space exploration. His designs were based on an economy of scale which makes larger rockets more economical than smaller ones as the structure accounts for less and less of the overall weight of the launcher. [2] At some point the dry weight of the launcher becomes lower than the payload it can launch, after which increases in payload fraction are essentially free. However, this point is crossed at relatively large vehicle sizes - Bono's original OOST study from 1963 was over 500 feet (150 m) long - and this path to lower costs only makes sense if there is an enormous amount of payload that needs to be launched.

After designing a number of such vehicles, including ROOST and the ROMBUS/Ithacus/Pegasus series, Bono noticed that the S-IVB stage, then just starting to be used operationally, was very close to being able to reach orbit on its own if launched from the ground. Intrigued, Bono started looking at what missions a small S-IVB-based SSTO could accomplish, realizing that it would be able to launch a crewed Gemini capsule if it was equipped with some upgrades, notably an aerospike engine that would improve the specific impulse and provide altitude compensation. [3] He called the design "SASSTO", short for "Saturn Application Single-Stage To Orbit".

These same upgrades would also have the side-effect of lowering the weight of the SASSTO compared to the original S-IVB, while at the same time increasing its performance. Thus the study also outlined a number of ways that it could be used in place of the S-IV in existing Saturn IB and Saturn V stacks, increasing their performance. When used with the existing Saturn I lower stage, it would improve payload to low Earth orbit from 35,000 to 52,500 lb (23,800 kg), or 57,000 lb (26,000 kg) if the landing gear were removed and it was expended like the S-IVB. SASSTO would thus give NASA a short-term inexpensive crewed launch capability, while also offering improved heavy-launch capability on the existing Saturn infrastructure.

SASSTO required a number of new technologies, however, which made development risky. In particular, the performance of the aerospike engine had to be considerably higher than the J-2 it would replace, yet also offer the ability to be restarted multiple times as the single engine was used for launch, de-orbit and landing. Of particular note was the final landing burn, which required the engines to be restarted at 2,500 ft (760 m) during the descent. The vehicle's weight was also greatly reduced, almost by half, which would not have been trivial considering the relatively good performance of the S-IVB design.

Design

Although the SASSTO claimed the S-IVB as its starting point, this was a conceit, and the vehicle had little in common with the S-IVB except its size.[ citation needed ]

The internal fuel tankage was considerably different from in the S-IV. The LH2 was no longer cylindrical, but spherical, and moved to the forward location in the fuselage. The LOX tankage, originally on top of the LH2, was re-positioned into a series of smaller spherical tanks arranged in a ring below the LH2. The tanks were all moved forward within the airframe compared to the engine, all of these changes being made in order to reduce changes in the center of gravity as the fuel was burned off. The fuselage section immediately above the engine was necked down, forming what appeared to be a larger single plug. The upper section of the fuselage, over the top of the hydrogen tank, was likewise necked down.

In order to increase the amount of LH2 being carried, given the fixed dimensions, SASSTO proposed freezing 50% of the fuel to produce a slush hydrogen mixture. This improvement was not uncommon in designs of the era, although it was not until the 1990s that any serious development work on the concept was carried out. [4]

The rearmost portion of the spacecraft was a single large plug nozzle, fed by a series of 36 injectors operating at 1500 psia, producing 277,000 lbf (1,230 kN) of thrust. Since plug nozzles gain efficiency as they grow larger, the 465 sec specific impulse (compared to the J-2's 425) was not particularly aggressive. The engine also served as the primary heat shield, actively cooled by liquid hydrogen that was then dumped overboard.

Four landing legs extended from fairings on the fuselage sides, retracting to a point about even with the "active" portion of the engine area. Four clusters of small maneuvering engines were located between the legs, about half-way from front to back along the fuselage. A series of six smaller tanks arranged in the gaps between the LOX and LH2 tanks fed the maneuvering engines.

SASSTO delivered 6,200 lb (2,800 kg) of cargo to a 110 nmi (200 km) orbit when launched due east from the Kennedy Space Center. Empty weight was 14,700 lb (6,700 kg), considerably lighter than the S-IVB's 28,500 lb (12,900 kg), and gross lift off weight was 216,000 lb (98,000 kg). The typical payload was the Gemini, which was covered with a large aerodynamic fairing.

Re-entry maneuverability was through a blunt-body lifting profile, similar to the Apollo CSM. The cross-range was limited, about 230 miles (370 km), and there was basically no maneuverability at all on final approach. There was enough fuel for about 10 seconds of hovering and small maneuvers to select a flat landing spot. Because SASSTO was the same basic size as the S-IVB, Douglas proposed transporting it in the existing Aero Spacelines Super Guppy after landing at either Wendover Air Force Base in Utah, or Fort Bliss outside El Paso, Texas.

Developments

Dietrich Koelle used SASSTO as the starting point for a similar development at Messerschmitt-Bölkow-Blohm in the late 1960s. Unlike Bono's version, Koelle used as much existing technology and materials as possible, while abandoning the need for the specific S-IVB sizing. The result was a slightly larger spacecraft, the Beta, that launched 4,000 lb (1,800 kg) of payload without the use of slush fuel, advanced lightweight construction, or a real aerospike engine. As part of the Beta proposal, Koelle pointed out that even the existing S-IVB could reach orbit, with zero payload, if equipped with a high-pressure LOX/LH2 engine of 460 Isp. [5]

Gary Hudson, in 1991, pointed out that such an engine existed, the RS-25, using a RS-25-powered S-IVB as a thought experiment to demonstrate the real-world feasibility of SSTO launchers. [6] This study was part of his "Phoenix" series of launchers, all similar to the SASSTO. [7]

See also

Related Research Articles

<span class="mw-page-title-main">Single-stage-to-orbit</span> Launch system that only uses one rocket stage

A single-stage-to-orbit (SSTO) vehicle reaches orbit from the surface of a body using only propellants and fluids and without expending tanks, engines, or other major hardware. The term usually, but not exclusively, refers to reusable vehicles. To date, no Earth-launched SSTO launch vehicles have ever been flown; orbital launches from Earth have been performed by either fully or partially expendable multi-stage rockets.

A tripropellant rocket is a rocket that uses three propellants, as opposed to the more common bipropellant rocket or monopropellant rocket designs, which use two or one propellants, respectively. Tripropellant systems can be designed to have high specific impulse and have been investigated for single-stage-to-orbit designs. While tripropellant engines have been tested by Rocketdyne and Energomash, no tripropellant rocket has been flown.

<span class="mw-page-title-main">Ariane (rocket family)</span> Family of European medium- and heavy-lift rocket launch vehicles

Ariane is a series of European civilian expendable launch vehicles for space launch use. The name comes from the French spelling of the mythological character Ariadne. France first proposed the Ariane project and it was officially agreed upon at the end of 1973 after discussions between France, Germany and the UK. The project was Western Europe's second attempt to develop its own launcher following the unsuccessful Europa project. The Ariane project was code-named L3S.

<span class="mw-page-title-main">S-IVB</span> Third stage on the Saturn V and second stage on the Saturn IB

The S-IVB was the third stage on the Saturn V and second stage on the Saturn IB launch vehicles. Built by the Douglas Aircraft Company, it had one J-2 rocket engine. For lunar missions it was fired twice: first for Earth orbit insertion after second stage cutoff, and then for translunar injection (TLI).

<span class="mw-page-title-main">Saturn (rocket family)</span> Family of American heavy-lift rocket launch vehicles

The Saturn family of American rockets was developed by a team of mostly German rocket engineers and scientists led by Wernher von Braun to launch heavy payloads to Earth orbit and beyond. The Saturn family used liquid hydrogen as fuel in the upper stages. Originally proposed as a military satellite launcher, they were adopted as the launch vehicles for the Apollo Moon program. Three versions were built and flown: the medium-lift Saturn I, the heavy-lift Saturn IB, and the super heavy-lift Saturn V.

<span class="mw-page-title-main">Rotary Rocket</span> Company

Rotary Rocket Company was a rocketry company that developed the Roton concept in the late 1990s as a fully reusable single-stage-to-orbit (SSTO) crewed spacecraft. The design was initially conceived by Bevin McKinney, who shared it with Gary Hudson. In 1996, Rotary Rocket Company was formed to commercialize the concept. The Roton was intended to reduce costs of launching payloads into low earth orbit by a factor of ten.

<span class="mw-page-title-main">Saturn IB</span> American rocket used in the Apollo program during the 1960s and 70s

The Saturn IB was an American launch vehicle commissioned by the National Aeronautics and Space Administration (NASA) for the Apollo program. It uprated the Saturn I by replacing the S-IV second stage, with the S-IVB. The S-IB first stage also increased the S-I baseline's thrust from 1,500,000 pounds-force (6,700,000 N) to 1,600,000 pounds-force (7,100,000 N) and propellant load by 3.1%. This increased the Saturn I's low Earth orbit payload capability from 20,000 pounds (9,100 kg) to 46,000 pounds (21,000 kg), enough for early flight tests of a half-fueled Apollo command and service module (CSM) or a fully fueled Apollo Lunar Module (LM), before the larger Saturn V needed for lunar flight was ready.

<span class="mw-page-title-main">Lockheed Martin X-33</span> Uncrewed re-usable spaceplane technology demonstrator for the VentureStar

The Lockheed Martin X-33 was a proposed uncrewed, sub-scale technology demonstrator suborbital spaceplane that was developed for a period in the 1990s. The X-33 was a technology demonstrator for the VentureStar orbital spaceplane, which was planned to be a next-generation, commercially operated reusable launch vehicle. The X-33 would flight-test a range of technologies that NASA believed it needed for single-stage-to-orbit reusable launch vehicles, such as metallic thermal protection systems, composite cryogenic fuel tanks for liquid hydrogen, the aerospike engine, autonomous (uncrewed) flight control, rapid flight turn-around times through streamlined operations, and its lifting body aerodynamics.

<span class="mw-page-title-main">McDonnell Douglas DC-X</span> Prototype single-stage-to-orbit rocket developed & flown between 1991-1996

The DC-X, short for Delta Clipper or Delta Clipper Experimental, was an uncrewed prototype of a reusable single-stage-to-orbit launch vehicle built by McDonnell Douglas in conjunction with the United States Department of Defense's Strategic Defense Initiative Organization (SDIO) from 1991 to 1993. Starting 1994 until 1995, testing continued through funding of the US civil space agency NASA. In 1996, the DC-X technology was completely transferred to NASA, which upgraded the design for improved performance to create the DC-XA. After a test flight of DC-XA in 1996 resulted in a fire, the project was canceled.

The Saturn I was a rocket designed as the United States' first medium lift launch vehicle for up to 20,000-pound (9,100 kg) low Earth orbit payloads. The rocket's first stage was built as a cluster of propellant tanks engineered from older rocket tank designs, leading critics to jokingly refer to it as "Cluster's Last Stand". Its development was taken over from the Advanced Research Projects Agency in 1958 by the newly formed civilian NASA. Its design proved sound and flexible. It was successful in initiating the development of liquid hydrogen-fueled rocket propulsion, launching the Pegasus satellites, and flight verification of the Apollo command and service module launch phase aerodynamics. Ten Saturn I rockets were flown before it was replaced by the heavy lift derivative Saturn IB, which used a larger, higher total impulse second stage and an improved guidance and control system. It also led the way to development of the super-heavy lift Saturn V which carried the first men to landings on the Moon in the Apollo program.

<span class="mw-page-title-main">Space Shuttle external tank</span> Component of the Space Shuttle launch vehicle

The Space Shuttle external tank (ET) was the component of the Space Shuttle launch vehicle that contained the liquid hydrogen fuel and liquid oxygen oxidizer. During lift-off and ascent it supplied the fuel and oxidizer under pressure to the three RS-25 main engines in the orbiter. The ET was jettisoned just over 10 seconds after main engine cut-off (MECO) and it re-entered the Earth's atmosphere. Unlike the Solid Rocket Boosters, external tanks were not re-used. They broke up before impact in the Indian Ocean, away from shipping lanes and were not recovered.

The Apollo Applications Program (AAP) was created as early as 1966 by NASA headquarters to develop science-based human spaceflight missions using hardware developed for the Apollo program. AAP was the ultimate development of a number of official and unofficial Apollo follow-on projects studied at various NASA labs. However, the AAP's ambitious initial plans became an early casualty when the Johnson Administration declined to support it adequately, partly in order to implement its Great Society set of domestic programs while remaining within a $100 billion budget. Thus, Fiscal Year 1967 ultimately allocated $80 million to the AAP, compared to NASA's preliminary estimates of $450 million necessary to fund a full-scale AAP program for that year, with over $1 billion being required for FY 1968. The AAP eventually led to Skylab, which absorbed much of what had been developed under Apollo Applications.

<span class="mw-page-title-main">Atlas-Centaur</span> Family of space launch vehicles

The Atlas-Centaur was a United States expendable launch vehicle derived from the SM-65 Atlas D missile. The vehicle featured a Centaur upper stage, the first such stage to use high-performance liquid hydrogen as fuel. Launches were conducted from Launch Complex 36 at the Cape Canaveral Air Force Station (CCAFS) in Florida. After a strenuous flight test program, Atlas-Centaur went on to launch several crucial spaceflight missions for the United States, including Surveyor 1, Mariner 4, and Pioneer 10/11. The vehicle would be continuously developed and improved into the 1990s, with the last direct descendant being the highly successful Atlas II.

<span class="mw-page-title-main">Aerojet M-1</span> Largest rocket engine to be designed

The Aerojet M-1 was the largest and most powerful liquid-hydrogen-fueled liquid-fuel rocket engine to be designed and component-tested. It was originally developed during the 1950s by the US Air Force. The M-1 offered a baseline thrust of 6.67 MN and an immediate growth target of 8 MN. If built, the M-1 would have been larger and more efficient than the famed F-1 that powered the first stage of the Saturn V rocket to the Moon.

<span class="mw-page-title-main">Saturn II</span> Proposed NASA heavy-lift launch vehicle

The Saturn II was a series of American expendable launch vehicles, studied by North American Aviation under a NASA contract in 1966, derived from the Saturn V rocket used for the Apollo lunar program. The intent of the study was to eliminate production of the Saturn IB, and create a lower-cost heavy launch vehicle based on Saturn V hardware. North American studied three versions with the S-IC first stage removed: the INT-17, a two-stage vehicle with a low Earth orbit payload capability of 47,000 pounds (21,000 kg); the INT-18, which added Titan UA1204 or UA1207 strap-on solid rocket boosters, with payloads ranging from 47,000 pounds (21,000 kg) to 146,400 pounds (66,400 kg); and the INT-19, using solid boosters derived from the Minuteman missile first stage.

The Saturn MLV was a proposed concept family of rockets, intended as a follow-on to the Saturn V. MLV stands for "Modified Launch Vehicle".

<span class="mw-page-title-main">Saturn V</span> American super heavy-lift expendable rocket

Saturn V is a retired American super heavy-lift launch vehicle developed by NASA under the Apollo program for human exploration of the Moon. The rocket was human-rated, with three stages, and powered with liquid fuel. It was flown from 1967 to 1973. It was used for nine crewed flights to the Moon, and to launch Skylab, the first American space station.

<span class="mw-page-title-main">Chrysler SERV</span>

SERV, short for Single-stage Earth-orbital Reusable Vehicle, was a proposed space launch system designed by Chrysler's Space Division for the Space Shuttle project. SERV was so radically different from the two-stage spaceplanes that almost every other competitor entered into the Shuttle development process that it was never seriously considered for the shuttle program.

The Lockheed Star Clipper was a proposed Earth-to-orbit spaceplane based on a large lifting body spacecraft and a wrap-around drop tank. Originally proposed during a United States Air Force program in 1966, the basic Star Clipper concept lived on during the early years of the NASA Space Shuttle program, and as that project evolved, in a variety of new versions like the LS-200.

<span class="mw-page-title-main">Liquid fly-back booster</span> Launch vehicle study

Liquid Fly-back Booster (LFBB) was a German Aerospace Center's (DLR's) project concept to develop a liquid rocket booster capable of reusing for Ariane 1 in order to significantly reduce the high cost of space transportation and increase environmental friendliness. lrb would replace the existing liquid rocket boosters, providing main thrust during the countdown. Once separated, two winged boosters would perform an atmospheric entry, go back autonomously to the French Guiana, and land horizontally on the airport like an aeroplane.

References

Notes

  1. ↑ "Beta". Archived from the original on August 20, 2016.
  2. ↑ "OOST" Archived 2011-10-10 at the Wayback Machine
  3. ↑ Bono, 1969
  4. ↑ Nancy McNelis et al., "A Summary of the Slush Hydrogen Technology Program for the National Aero-Space Plane" Archived July 4, 2009, at the Wayback Machine , NASA TM-106863, April 1995
  5. ↑ Koelle, 1970
  6. ↑ "A Single-Stage-to-Orbit Thought Experiment", Appendix to "Recent Developments"
  7. ↑ Gary Hudson, "History of the Phoenix VTOL SSTO and Recent Developments in Single-Stage Launch Systems", Proceedings of 4th International Space Conference of Pacific-basin Societies, AAS Volume 77 (1991), pp. 329-351

Bibliography

Further reading

  • Philip Bono et al., "The Saturn S-IVB as a Test-Bed for Booster Recovery", Douglas Engineering Paper 3808, 6th European Symposium on Space Technology, May 1966
  • Philip Bono, "The reusable booster paradox - aircraft technology or operations", Spaceflight, Volume 9 (1967), pp. 379–387

This page is based on this Wikipedia article
Text is available under the CC BY-SA 4.0 license; additional terms may apply.
Images, videos and audio are available under their respective licenses.