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88-417: HOTOL , for Horizontal Take-Off and Landing , was a 1980s British design for a single-stage-to-orbit (SSTO) spaceplane that was to be powered by an airbreathing jet engine . Development was being conducted by a consortium led by Rolls-Royce and British Aerospace (BAe). Designed as a single-stage-to-orbit (SSTO) reusable winged launch vehicle, HOTOL was to be fitted with a unique air-breathing engine,

176-476: A thrust to weight ratio in excess of 1, enabling them to lift off. Clearly, one of the main issues with nuclear propulsion would be safety, both during a launch for the passengers, but also in case of a failure during launch. As of February 2024, no current program is attempting nuclear propulsion from Earth's surface. Because they can be more energetic than the potential energy that chemical fuel allows for, some laser or microwave powered rocket concepts have

264-569: A French license were not to be exported to other foreign nations without its express approval. Yet another form of common licensing restriction related solely to the licensing activity, regulating whether the specified product was fully produced or partly assembled, and whether entire products or their individual components were manufactured. The governments of Germany and Switzerland imposed similar restrictions on military vehicles manufactured in Argentina and Chile under license. In some cases,

352-472: A conventional runway (approx 1,500 metres minimum). Only a single payload would have been carried at a time as BAe had judged this to be more economic as it removed any need for satellite interfacing and allowed for missions to be tailored to individual requirements. During its high-altitude phase, its flight control system would have been linked to ground stations and to space-based global navigation system navigation, while radar would have been used during

440-520: A justification, and that there was no defence requirement for such vehicles. He also noted that the "engineering problems are considerable" and that it was unlikely to enter service until the 2020s; Barnes also observed the HOTOL engine to be "ingenious". In November 1985, the RAE issued an assessment of HOTOL's study proposal; the organisation believed that HOTOL would take up to 20 years to develop, rather than

528-413: A licensee who is authorized to use such rights under certain conditions. The licensee is manufacturing a product for which it has been granted production rights under specific conditions, while the licensor retains ownership of the intellectual property thereof. In some cases the licensor will supply the necessary technical data, prototypes, and/or machine tools to the licensee. While licensed production

616-461: A much higher rate of production, and was considerably cheaper than national sourcing and off-the-shelf acquisition. European automobile manufacturers were the first to adopt this practice, producing a number of specialized American components for their passenger cars under license. The United States not only supplied European factories with the necessary blueprints and licenses, but also sourced American-made tooling equipment accordingly, which allowed

704-438: A poor quality licensed product may damage the reputation of the original licensor. However, this is not considered a form of consumer fraud unless the product is unlicensed or counterfeit . Unlicensed production is the utilization of foreign manufacturing technology without a license, achieved through industrial espionage or reverse engineering . Products in high demand on the international market can be reproduced, based on

792-569: A proposed SSTO. It is one of only a few prototype SSTO vehicles ever built. Several other prototypes were intended, including the DC-X2 (a half-scale prototype) and the DC-Y, a full-scale vehicle which would be capable of single stage insertion into orbit. Neither of these were built, but the project was taken over by NASA in 1995, and they built the DC-XA, an upgraded one-third scale prototype. This vehicle

880-496: A prototype could be flying as early as 1990. According to British government files, neither BAe nor the MoD were enthusiastic for the prospects of American involvement in the programme, expressing reluctance out of a belief that the outcome of such a move could result in the UK becoming a junior member in a project that it once led. There was also a belief that if Britain chose to pair up with

968-650: A public display of the HOTOL satellite launcher project and released details on its proposed operations. In December 1984, a Department of Trade and Industry (DTI) memorandum noted that West Germany was interested in the programme, while France had adopted a critical attitude towards HOTOL, which the ministry viewed as potentially due to it being seen as a competitor to French-led projects. According to Minister of Trade and Industry Geoffrey Pattie , French diplomatic pressure to gather support for its own proposed Hermes space vehicle had inadvertently generated support and interest amongst European Space Agency (ESA) members in

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1056-534: A pure rocket approach would give approximately the same performance at less cost. By 1989, the outlook for HOTOL had become bleak; from the onset of the project, support between the British government and industrial partners had been uneven, while the United States had emerged as the only foreign nation that showed willingness to contribute to the programme, in part because of the secrecy surrounding it. There

1144-488: A relatively small delta-v increase can be helpful, and outside assistance for a vehicle is therefore desirable. Proposed launch assists include: And on-orbit resources such as: Due to weight issues such as shielding, many nuclear propulsion systems are unable to lift their own weight, and hence are unsuitable for launching to orbit. However, some designs such as the Orion project and some nuclear thermal designs do have

1232-555: A reusable vehicle must be able to reenter without damage, and land safely. While single-stage rockets were once thought to be beyond reach, advances in materials technology and construction techniques have shown them to be possible. For example, calculations show that the Titan II first stage, launched on its own, would have a 25-to-1 ratio of fuel to vehicle hardware. It has a sufficiently efficient engine to achieve orbit, but without carrying much payload. Hydrogen fuel might seem

1320-520: A significantly higher degree of regular maintenance. It is considered to be marginally possible to launch a single-stage-to-orbit chemically fueled spacecraft from Earth. The principal complicating factors for SSTO from Earth are: high orbital velocity of over 7,400 metres per second (27,000 km/h; 17,000 mph); the need to overcome Earth's gravity, especially in the early stages of flight; and flight within Earth's atmosphere , which limits speed in

1408-605: A similar manner to that of a rocket when having attained close to and within LEO. This engine would have also been capable of powering the spacecraft to hypersonic speeds. It was a crucial element of the programme, having been publicly attributed as "the heart of Hotol's very low launch costs". The exact details of this engine were covered by the Official Secrets Act of the United Kingdom; consequently, there

1496-693: A sufficiently efficient propulsion system and discontinued development. Single-stage-to-orbit is much easier to achieve on extraterrestrial bodies that have weaker gravitational fields and lower atmospheric pressure than Earth, such as the Moon and Mars, and has been achieved from the Moon by the Apollo program 's Lunar Module , by several robotic spacecraft of the Soviet Luna program , and by China's Chang'e 5 and Chang'e 6 lunar sample return missions. Before

1584-518: A suitable engine, and soon conceived of an unmanned, fully reusable single-stage-to-orbit (SSTO) winged spaceplane as a launch vehicle. Thus, the project had soon become a joint venture between BAe and Rolls-Royce, led by John Scott-Scott and Bob Parkinson . Early on, there was an ambition to 'Europeanise' the project and to involve other nations in its development and manufacture as it was recognised that an estimated £4 billion would be needed to fund full-scale development. In August 1984, BAe unveiled

1672-449: A two-year £3 million proof of concept study be performed under a public-private partnership arrangement, consisting of £1 million provided by the UK government and the remainder being financed by Rolls-Royce and BAe themselves. Pattie reasoned that the project would serve Britain's "strategic capability", and that tests of key technologies could foster international collaboration. According to aerospace publication Flight International ,

1760-486: A vacuum bell in atmosphere would have disastrous consequences for the engine. Engines designed to fire in atmosphere therefore have to shorten the nozzle, only expanding the gasses to atmospheric pressure. The efficiency losses due to the smaller bell are usually mitigated via staging, as upper stage engines such as the Rocketdyne J-2 do not have to fire until atmospheric pressure is negligible, and can therefore use

1848-521: A wing design that had been derived from that of Concorde ; its large area resulted in relatively low wing loading, which would have resulted in lower reentry temperatures (never rising above 1,400 °C). Built out of carbon composite materials, there would have been no need for the use of insulating tiles akin to those that comprised the Space Shuttle thermal protection system . The internally stowed landing gear would have been too small to carry

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1936-488: Is an important concept in the engineering of a rocket. However, mass fraction may have little to do with the costs of a rocket, as the costs of fuel are very small when compared to the costs of the engineering program as a whole. As a result, a cheap rocket with a poor mass fraction may be able to deliver more payload to orbit with a given amount of money than a more complicated, more efficient rocket. Many vehicles are only narrowly suborbital, so practically anything that gives

2024-519: Is because of both the low density and the additional insulation required to minimize boiloff (a problem which does not occur with kerosene and many other fuels). The low density of hydrogen further affects the design of the rest of the vehicle: pumps and pipework need to be much larger in order to pump the fuel to the engine. The result is the thrust/weight ratio of hydrogen-fueled engines is 30–50% lower than comparable engines using denser fuels. This inefficiency indirectly affects gravity losses as well;

2112-526: Is defined as an overseas production arrangement, usually as a direct result of inter-state trade agreements, that permits a foreign government or entity to acquire the technical information to manufacture all or part of an equipment or component patented in the exporting country. According to the World Intellectual Property Organization (WIPO), it must constitute a partnership between an intellectual property owner and

2200-410: Is often dependent on the appropriate technology transfers , it does not necessarily entail ownership and management of the overseas production by the technology supplier. However, the licensor does retain the right to continue to use the licensed property, and to attribute further licenses to third parties. Occasionally, licensees may themselves sub-license a third party with or without the agreement of

2288-402: Is relatively little public information about its development and on its operation. However, material was later declassified when government policy changed to prevent the keeping of secret patents without an attributed justification. Within the atmosphere, air is taken in through two vertically mounted intake ramps , then the flow would be split, passing the correct amount to the pre-coolers, and

2376-603: The SSME ) + 10 x turboramjets. Around 1985 the NASP project was intended to launch a scramjet vehicle into orbit, but funding was stopped and the project cancelled. At around the same time, the HOTOL tried to use precooled jet engine technology, but failed to show significant advantages over rocket technology. The DC-X, short for Delta Clipper Experimental, was an uncrewed one-third scale vertical takeoff and landing demonstrator for

2464-629: The United Kingdom Space Agency , BAe, and the Air Force Research Laboratory . As of 2017 REL plan to demonstrate a flight-ready pre-cooler operating under simulated flight conditions in 2018, and statically test a demonstration engine core in 2020. HOTOL was envisioned as an unmanned, fully reusable single-stage-to-orbit (SSTO) winged spaceplane. The unmanned craft was intended to put a payload of around 7 to 8 tonnes in orbit, at 300 km altitude. It

2552-510: The United Nations Office on Drugs and Crime has noted that while licensing companies often provide quality control measures, and there is some incentive for licensees to comply or risk legal action and the ensuing damage to their own profit, manufacturers who engage in unlicensed production are under no such obligations. Another method of circumventing the need for a license involves a manufacturer making slight modifications in

2640-404: The 12-year timetable that had been envisioned by industry. The RAE also projected that the project would have an estimated total cost of £5 billion (as of its value in 1985), £750 million of which would be required in a six-year definition phase and an estimated £25 million in a pre-definition feasibility study. During development, it was found that the comparatively heavy rear-mounted engine moved

2728-463: The 1990s) which were never constructed include: Star-raker : In 1979 Rockwell International unveiled a concept for a 100-ton payload heavy-lift multicycle airbreather ramjet/ cryogenic rocket engine , horizontal takeoff/horizontal landing single-stage-to-orbit spaceplane named Star-Raker , designed to launch heavy Space-based solar power satellites into a 300 nautical mile Earth orbit. Star-raker would have had 3 x LOX/LH2 rocket engines (based on

British Aerospace HOTOL - Misplaced Pages Continue

2816-571: The DC-X, often said that he thought the first successful orbital SSTO would more likely be fueled by propane. Some SSTO concepts use the same engine for all altitudes, which is a problem for traditional engines with a bell-shaped nozzle . Depending on the atmospheric pressure, different bell shapes are required. Engines designed to operate in a vacuum have large bells, allowing the exhaust gasses to expand to near vacuum pressures, thereby raising efficiency. Due to an effect known as Flow separation , using

2904-480: The HOTOL project. Despite this climate of tentative interest and possible European support, there was a general attitude of reluctance within the British government to take the lead on a new space launcher. In March 1985, there were claims that Rolls-Royce was in the process of conducting licensing talks for HOTOL engine technology with American propulsion company Rocketdyne . In April 1985, Pattie wrote to Secretary of State for Defence Michael Heseltine to propose

2992-461: The RB545 or Swallow, that was under development by British engine manufacturer Rolls-Royce. The propellant for the engine technically consisted of a combination of liquid hydrogen /liquid oxygen ; however, it was to employ a new means of dramatically reducing the amount of oxidizer needed to be carried on board by utilising atmospheric oxygen as the spacecraft climbed through the lower atmosphere. Since

3080-602: The RB545 would switch to using on-board LOX to burn with the hydrogen as a high-efficiency hydrogen/oxygen rocket. Single-stage-to-orbit 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 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 . The main projected advantage of

3168-676: The Rolls-Royce patents, and the Skylon vehicle intended to solve the problems of HOTOL. They first published these engine and spacecraft concepts in 1993, and have since been developing the core technologies, particularly the engine and its frost-controlled pre-cooler; initially supported by private funding, but latterly with support from the European Space Agency , the British National Space Centre ,

3256-466: The SSTO concept is elimination of the hardware replacement inherent in expendable launch systems. However, the non-recurring costs associated with design, development, research and engineering (DDR&E) of reusable SSTO systems are much higher than expendable systems due to the substantial technical challenges of SSTO, assuming that those technical issues can in fact be solved. SSTO vehicles may also require

3344-517: The United States, it would find itself frozen out of work on future European launchers. However, Rolls-Royce viewed transatlantic cooperation as necessary. BAe's head of future business, Peter Conchie, stated that, if possible, HOTOL should become a part of the European space framework. In early 1986, the British government formally approved the two-year study. In December 1984, project management consultant David Andrews issued an eight-page critique of

3432-425: The atmosphere to reduce the take-off weight of the vehicle. Some of the issues with this approach are: Thus with for example scramjet designs (e.g. X-43 ) the mass budgets do not seem to close for orbital launch. Similar issues occur with single-stage vehicles attempting to carry conventional jet engines to orbit—the weight of the jet engines is not compensated sufficiently by the reduction in propellant. On

3520-725: The atmosphere when it is at low altitude, and then using onboard liquid oxygen after switching to the closed cycle rocket engine at high altitude, the McDonnell Douglas DC-X , the Lockheed Martin X-33 and VentureStar which was intended to replace the Space Shuttle, and the Roton SSTO , which is a helicopter that can get to orbit. However, despite showing some promise, none of them have come close to achieving orbit yet due to problems with finding

3608-469: The atmosphere, and achieving a high enough mass-ratio to carry sufficient propellant to achieve orbit, plus a meaningful payload weight. Air-breathing designs typically fly at supersonic or hypersonic speeds, and usually include a rocket engine for the final burn for orbit. Whether rocket-powered or air-breathing, a reusable vehicle must be rugged enough to survive multiple round trips into space without adding excessive weight or maintenance. In addition

British Aerospace HOTOL - Misplaced Pages Continue

3696-561: The automobile companies to optimize their production lines. By the 1960s it was not uncommon for an entire specialized industry—such as the manufacture of rotary aircraft in the United Kingdom —to be dependent wholly on foreign-licensed components. A number of countries began making improvements to foreign products manufactured under license, and were even able to re-export them successfully. This trend resulted in some technology suppliers imposing additional conditions on

3784-452: The centre of mass of the vehicle rearwards. This meant that the vehicle had to be designed to push the centre of drag as far rearward as possible to ensure stability during the entire flight regime. Redesign of the vehicle to do this required a large mass of hydraulic systems, which cost a significant proportion of the payload, and made the economics unclear. In particular, some of the analysis seemed to indicate that similar technology applied to

3872-529: The early stages of flight due to drag, and influences engine performance. Advances in rocketry in the 21st century have resulted in a substantial fall in the cost to launch a kilogram of payload to either low Earth orbit or the International Space Station , reducing the main projected advantage of the SSTO concept. Notable single stage to orbit concepts include Skylon , which used the hybrid-cycle SABRE engine that can use oxygen from

3960-403: The economic life of the product. Developing nations began accounting for a significant percentage of licensed production during the late twentieth century. Governments of developing nations often sought to encourage rapid industrialization, reduce dependence on foreign imports, and combat high levels of unemployment by creating and retaining local jobs. However, in many of these nations there

4048-404: The end of its design phase while much of the plans remained in a speculative state; the craft was reportedly still dogged with aerodynamic problems and operational disadvantages at this point. A cheaper redesign, Interim HOTOL or HOTOL 2 , which was to be launched from the back of a modified Antonov An-225 transport aircraft , specifically was promoted by BAe in 1991; however, this proposal

4136-604: The engine, which it referred to by the name Swallow . Reportedly, the United States Air Force were interested in the technology used in the Swallow engine for its own purposes. In November 1985, discussions between Prime Minister Margaret Thatcher , Minister without portfolio David Young and US President Ronald Reagan 's scientific advisor George Keyworth noted American interest in collaboration on developing hypersonic vehicles such as HOTOL, and that

4224-412: The excess to spill ducts. Hydrogen from the fuel tanks would be passed through two heat exchangers to pre-cool the air prior to entering a high overall pressure-ratio turbojet -like engine cycle — the heated hydrogen driving a turbine to compress and feed the cooled air into the rocket engine, where it was combusted with some of the hydrogen used to cool the air. The majority of the remaining hot hydrogen

4312-423: The exhaust gases down to near vacuum pressures. As a result, these engine bells are counterproductive due to their excess weight. Some SSTO concepts use very high pressure engines which permit high ratios to be used from ground level. This gives good performance, negating the need for more complex solutions. Some designs for SSTO attempt to use airbreathing jet engines that collect oxidizer and reaction mass from

4400-402: The explicit licensing of technological information. Knock-down kits are regarded as a prerequisite to licensed production; they consist of products assembled locally from imported, pre-manufactured parts. Some licensors find it difficult to regulate the quality of their products manufactured under license. It is not always made clear to consumers where exactly a particular good originated, and

4488-443: The intellectual property owner. Licensing agreements determine the form and scope of compensation to the intellectual property owner, which usually takes the form of a flat licensing fee or a running royalty payment derived from a share of the licensee's revenue. The licenses can be terminated by the licensor, or may expire after a set date; however, the technology and knowledge, once transferred, cannot be rescinded, so even if

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4576-474: The intention of producing a viable engine for powering a space launch system . In 1982, British Aerospace (BAe), which was Europe's principal satellite -builder, began studying a prospective new launch system with the aim of providing launch costs that were 20 per cent of the American Space Shuttle operated by NASA . BAe became aware of work by British engine manufacturer Rolls-Royce on

4664-487: The larger bell. One possible solution would be to use an aerospike engine , which can be effective in a wide range of ambient pressures. In fact, a linear aerospike engine was to be used in the X-33 design. Other solutions involve using multiple engines and other altitude adapting designs such as double-mu bells or extensible bell sections . Still, at very high altitudes, the extremely large engine bells tend to expand

4752-509: The last drop of specific impulse, and shaving off the last pound, costs money and/or reduces reliability. The Tsiolkovsky rocket equation expresses the maximum change in velocity any single rocket stage can achieve: where: Licensed production This is an especially prominent commercial practice in developing nations , which often approach licensed production as a starting point for indigenous industrial development. While licensed production in developing nations provides stimulus to

4840-491: The licensee. The United States began inserting pro forma statements into licensing agreements known as "side letters" , which required the free sharing of any improvements made to American technology. Other attempts were also made to control the destination of licensed products, particularly with regards to the arms industry . For instance, France stipulated that military vehicles manufactured in South Africa under

4928-449: The licensing agreement expires they remain in the licensee's possession. Two related commercial practices are foreign subcontractor production and the proliferation of knock-down kits . Foreign subcontracting occurs when a product's original manufacturer contracts the production of its individual parts and components to a second party overseas. Such arrangements are not considered examples of licensed production because they do not involve

5016-543: The main challenge is achieving a high enough mass-ratio to carry sufficient propellant to achieve orbit , plus a meaningful payload weight. One possibility is to give the rocket an initial speed with a space gun , as planned in the Quicklaunch project. For air-breathing SSTO, the main challenge is system complexity and associated research and development costs, material science , and construction techniques necessary for surviving sustained high-speed flight within

5104-495: The mass ratio to delta-v curve is very steep to reach orbit in a single stage, and this makes a 10% difference to the mass ratio on top of the tankage and pump savings. The overall effect is that there is surprisingly little difference in overall performance between SSTOs that use hydrogen and those that use denser fuels, except that hydrogen vehicles may be rather more expensive to develop and buy. Careful studies have shown that some dense fuels (for example liquid propane ) exceed

5192-477: The obvious fuel for SSTO vehicles. When burned with oxygen , hydrogen gives the highest specific impulse of any commonly used fuel: around 450 seconds, compared with up to 350 seconds for kerosene . Hydrogen has the following advantages: However, hydrogen also has these disadvantages: These issues can be dealt with, but at extra cost. While kerosene tanks can be 1% of the weight of their contents, hydrogen tanks often must weigh 10% of their contents. This

5280-479: The original technology supplier did not need to manufacture the product itself—it merely patented a specific design, then sold the actual production rights to multiple clients. This resulted in different companies separately manufacturing identical products licensed from the same licensee. For many licensee companies, licensed production by other firms provides a continuous outlet for their proprietary technology, increasing their return on investment and prolonging

5368-430: The other hand, LACE-like precooled airbreathing designs such as the Skylon spaceplane (and ATREX ) which transition to rocket thrust at rather lower speeds (Mach 5.5) do seem to give, on paper at least, an improved orbital mass fraction over pure rockets (even multistage rockets) sufficiently to hold out the possibility of full reusability with better payload fraction. It is important to note that mass fraction

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5456-519: The oxidizer typically represents the majority of the takeoff weight of a rocket, HOTOL was to be considerably smaller than normal pure-rocket designs, roughly the size of a medium-haul airliner such as the McDonnell Douglas DC-9 / MD-80 . While HOTOL's proof-of-concept design study was being carried out, attempts were made by both industry and the British government to establish international cooperation to develop, produce, and deploy

5544-499: The performance of hydrogen fuel when used in an SSTO launch vehicle by 10% for the same dry weight. In the 1960s Philip Bono investigated single-stage, VTVL tripropellant rockets , and showed that it could improve payload size by around 30%. Operational experience with the DC-X experimental rocket has caused a number of SSTO advocates to reconsider hydrogen as a satisfactory fuel. The late Max Hunter, while employing hydrogen fuel in

5632-423: The potential to launch vehicles into orbit, single stage. In practice, this area is not possible with current technology. The design space constraints of SSTO vehicles were described by rocket design engineer Robert Truax : Using similar technologies (i.e., the same propellants and structural fraction), a two-stage-to-orbit vehicle will always have a better payload-to-weight ratio than a single stage designed for

5720-427: The production and technical capabilities of local industry, in many cases it remains at least partly dependent on foreign support. The four most common applications of licensed production have historically been automotive engines and parts, weaponry, aircraft, and pharmaceuticals. During World War I , it was more common for licensing agreements to take place between companies in the same country; for example, Opel

5808-495: The programme, noting that the design was optimised for the ascent while exposing itself to extended thermal loads during descent due to a low level of drag . He also claimed that the vehicle offered no capability that was not already available; BAe responded that the criticisms made had been answered. In April 1985, the Ministry of Defence 's research and development department deputy controller James Barnes claimed that HOTOL lacked

5896-414: The project ended. The termination of development work on HOTOL led to the formation of Reaction Engines Limited (REL) to develop and produce Skylon , a proposed spacecraft based on HOTOL technologies, including its air-breathing engine. The ideas behind HOTOL originated from work done by British engineer Alan Bond in the field of pre-cooled jet engines. Bond had specifically performed this research with

5984-614: The risks inherent in the development of new products by taking advantage of the proven reputation of products which had already achieved success in foreign markets. The economic life of many products, namely in the automotive and defense sectors, have been prolonged by overseas licensed production long after they were considered obsolete in their countries of origin. Developing nations such as Pakistan and Singapore which built important segments of their industry on licensed production have now themselves become licensors of technology and products to less developed states. Licensed production

6072-408: The same mission, in most cases, a very much better [payload-to-weight ratio]. Only when the structural factor approaches zero [very little vehicle structure weight] does the payload/weight ratio of a single-stage rocket approach that of a two-stage. A slight miscalculation and the single-stage rocket winds up with no payload. To get any at all, technology needs to be stretched to the limit. Squeezing out

6160-448: The same or similar design, and branded in ways to make them indistinguishable from the original. When copied and reproduced without a license, certain items are sometimes recopied in a similar manner by a third party. The manufacturers responsible may also grant legitimately registered sub-licenses for their unlicensed products, profiting at the expense of the real intellectual property owner. The quality of unlicensed goods varies greatly;

6248-432: The second half of the twentieth century, very little research was conducted into space travel. During the 1960s, some of the first concept designs for this kind of craft began to emerge. One of the earliest SSTO concepts was the expendable One stage Orbital Space Truck (OOST) proposed by Philip Bono , an engineer for Douglas Aircraft Company . A reusable version named ROOST was also proposed. Another early SSTO concept

6336-483: The spacecraft. In spite of American interest in the programme, there was little appetite amongst the members of the European Space Agency (ESA), and the British government was not prepared to depart from ESA cooperation. Additionally, technical issues were encountered, and there were allegations that comparisons with alternative launch systems such as conventional rocket vehicle using similar construction techniques failed to show much advantage to HOTOL. In 1989, funding for

6424-513: The support of the Ministry of Defense (MoD) was critical as the design of HOTOL's engine had been classified. In July 1985, Rolls-Royce's technical director Gordon Lewis stated that the firm sought the involvement of the Royal Aircraft Establishment 's (RAE) propulsion group, and that Rolls-Royce was not prepared to invest its own funds into engine development for HOTOL. By the second half of 1985, work had commenced on

6512-473: The take-off and landing phases. In addition to the placing of satellites into geosynchronous orbit or LOE, HOTOL was also projected as being able to also perform the retrieval of satellites and hardware from LOE. BAe promotional material depicts HOTOL docking with the International Space Station (ISS), a feat that the company claimed would have required manned operation as automated systems were not capable of performing such docking manoeuvres at that time. HOTOL

6600-404: The temperature to −50 °C (−58 °F) flash freezing the water into microscopic ice crystals, sufficiently cold that they wouldn't melt due to kinetic heating if they struck the second pre-cooler elements. A water trap could have been added after the first pre-cooler if operating conditions resulted in an excess of moisture. When it was no longer possible to use the atmosphere for combustion,

6688-577: The two-year concept-of-proof study. Early on, there was considerable pressure to demonstrate the project's feasibility and credibility in advance of final decisions being taken by ESA on the Hermes and what would become the Ariane 5 launch system, thus the work concentrated on the validation of critical technologies involved. By November 1985, DTI and RAE discussions noted that Rolls-Royce were seeking American data on ramjet technology to support their work on

6776-436: The vehicle has to hold itself up on rocket power until it reaches orbit. The lower excess thrust of the hydrogen engines due to the lower thrust/weight ratio means that the vehicle must ascend more steeply, and so less thrust acts horizontally. Less horizontal thrust results in taking longer to reach orbit, and gravity losses are increased by at least 300 metres per second (1,100 km/h; 670 mph). While not appearing large,

6864-401: The weight of the fully fuelled rocket, so emergency landings would have required the fuel to be dumped. The RB545, which was given the name "Swallow" by its manufacturer, British engine maker Rolls-Royce, was an air-breathing rocket engine. It would have functioned as an integrated dual-role powerplant, having been capable of air-breathing while operating within the atmosphere and operating in

6952-466: Was a reusable launch vehicle named NEXUS which was proposed by Krafft Arnold Ehricke in the early 1960s. It was one of the largest spacecraft ever conceptualized with a diameter of over 50 metres and the capability to lift up to 2000 short tons into Earth orbit, intended for missions to further out locations in the Solar System such as Mars . The North American Air Augmented VTOVL from 1963

7040-514: Was a similarly large craft which would have used ramjets to decrease the liftoff mass of the vehicle by removing the need for large amounts of liquid oxygen while traveling through the atmosphere. From 1965, Robert Salkeld investigated various single stage to orbit winged spaceplane concepts. He proposed a vehicle which would burn hydrocarbon fuel while in the atmosphere and then switch to hydrogen fuel for increasing efficiency once in space. Further examples of Bono's early concepts (prior to

7128-404: Was designed to conduct fully automated unmanned flights; however, it had been intended at a later stage to potentially re-introduce a pilot. Manned operations would have required the installation of a dedicated pressurised module within the payload bay. As designed, HOTOL would have been 62 metres long, 12.8 metres high, a fuselage diameter of 5.7 metres and a wingspan of 19.7 metres. It featured

7216-526: Was granted a license to produce BMW -designed aircraft engines for the German war effort. During the 1920s, European economists began advocating licensed production of foreign goods as the cure for "industrial particularism" —it allowed countries to bypass the costly research and development stage of acquiring products with which their own industries were unfamiliar, and refocus on the domestic manufacture of preexisting overseas designs. This allowed for

7304-423: Was intended to take off from a runway, mounted on the back of a large rocket-boosted trolley that would help get the craft up to "working speed". The engine was intended to switch from jet propulsion to pure rocket propulsion at 26–32 km high, by which time the craft would be travelling at Mach 5 to 7. After reaching low Earth orbit (LEO), HOTOL was intended to re-enter the atmosphere and glide down to land on

7392-399: Was little prospect for European involvement, ESA having elected to pursue development of what would become the Ariane 5 , a conventional space launch system. Rolls-Royce withdrew from the project, judging the eventual market for the engine was unlikely to be large enough to repay the development costs. The British government declined to offer further funding for HOTOL. The project was almost at

7480-809: Was lost when it landed with only three of its four landing pads deployed, which caused it to tip over on its side and explode. The project has not been continued since. From 1999 to 2001 Rotary Rocket attempted to build a SSTO vehicle called the Roton. It received a large amount of media attention and a working sub-scale prototype was completed, but the design was largely impractical. There have been various approaches to SSTO, including pure rockets that are launched and land vertically, air-breathing scramjet -powered vehicles that are launched and land horizontally, nuclear-powered vehicles, and even jet-engine -powered vehicles that can fly into orbit and return landing like an airliner, completely intact. For rocket-powered SSTO,

7568-492: Was not a strong tradition of technology-based industrial development, and local firms were seldom active participants in creating indigenous technology through research and development. Since their research capacity was typically too limited to meet their goals, adopting licensing agreements for foreign technology was an especially attractive option. Manufacturing licensed products generated employment and empowered local industry while reducing dependence on imports. It also avoided

7656-464: Was rejected as well. The design for Interim HOTOL was to have dispensed with an air-breathing engine cycle and was designed to use a more conventional mix of LOX and liquid hydrogen as fuel instead. In 1989, HOTOL co-creator Alan Bond and engineers John Scott-Scott and Richard Varvill formed Reaction Engines Limited (REL) which has since been working on a new air-breathing engine, SABRE , which used alternative designs to work around (and improve upon)

7744-414: Was released from the back of the engine, with a small amount drawn off to reheat the air in the spill ducts in a ramjet arrangement to produce "negative intake momentum drag". To prevent the pre-coolers from icing up, the first pre-cooler cooled the air to around 10 degrees above freezing point, to liquefy the water vapour in the air. Then liquid oxygen (LOX) would have been injected into the airflow to drop

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