IAC-14.D2.4.5 A Technical Overview of a SKYLON Based European Launch Service Operator Mark Hempsell, Reaction Engines Limited, Building D5, Culham Science Centre, Abingdon, Oxon, OX14 3DB United Kingdom, [email protected] Julio Aprea1, Roger Longstaff2, Giorgio Ferrari3, Steven Hens4, Sebastian Soller5, Roger Dewell6, Dan Ahearn7, Catriona Francis8 Between 2012 and 2014 an industrial consortium led by Reaction Engines conducted a feasibility study for the European Space Agency with the objective to explore the feasibility of SKYLON as the basis for a launcher that meets the requirements established by ESA for the Next Generation European Launcher. SKYLON is a fully reusable single stage to orbit launch system under active development. The purpose of the Study, which was called SKYLON Based European Launch Service Operator (S-ELSO), was to support ESA decision making on launch service strategy by exploring the potential implications of this new launch system on future European launch capability and the European industry that supports it. The launch operator requirements centred on geostationary transfer orbit missions and the Study’s main technical focus was on producing concept designs to demonstrate the feasibility of a complete launch infrastructure consisting of SKYLON, a reusable upper stage, and payload carriers. The requirement was for S-ELSO to operate from Centre Spatiale Guiana. The Study showed that the provision of new facilities, like SKYLON servicing buildings and a 5.9 km runway, and the links with existing CSG services such as payload preparation and propellant supply were feasible. The study showed an operational infrastructure fully able to meet European launch system requirements could be operational by 2024. I INTRODUCTION and an altitude of 28 km, at which point the engine can switch to a staged combustion pure rocket mode SKYLON using liquid oxygen as the oxidiser. SKYLON (Figure) a fully reusable single stage to orbit spaceplane that can take off from a runway reach low earth orbit with a payload of 15 tonnes at 300 km altitude. Once the mission is completed then it returns to earth for a runway landing [1]. It is under active development and is planned to reach operation in the early 2020s. SKYLON is the result of 30 years of technology development and design studies. It is based on an air-breathing engine concept called Figure 1: The SKYLON Spaceplane SABRE, which uses a combination of a pre-cooler heat exchanger to cool incoming air, and a turbo- The technical feasibility of the SABRE compressor to raise the air pressure high enough to engine was primarily centred on the pre-coolers and then be fed as the oxidiser into a rocket engine whether they could be made for the mass required for combustion chamber to be burnt with liquid a flight system. The demonstration of the technology hydrogen. The air-breathing mode of the SABRE was completed in 2012 with the completion of a test engine can be sustained to a little beyond Mach 5 programme on a test heat exchanger using flight 1 European Space Agency, France, [email protected] representative modules (Figure). The impact of the 2 Reaction Engines Ltd, United Kingdom, [email protected] SABRE engine on the overall system is that the 3 Thales Alenia Space, Italy, [email protected] mass fraction needed to achieve orbit in a single 4 QinetiQ Space Nv, Belgium, [email protected] 5 Airbus Defence and Space, Germany, [email protected] stage is raised from around 13% for a pure rocket 6 Grafton Technology Ltd, United Kingdom, [email protected] vehicle to around 23%. 7 42 Technology Ltd, United Kingdom, [email protected] 8 Jacobs Engineering UK Ltd., United Kingdom, [email protected] 1 The Study was entitled S-ELSO (SKYLON based European Launch Service Operator) and was split into two separate activities, one exploring the technical and schedule aspects and the other exploring the business aspects both financial and economic. It was started in 2012 and the final report was delivered and final presentation held in June 2014. This paper gives an overview of the technical conclusions of S-ELSO, a separate paper reports the conclusion of the business study [3]. Figure 2: The Technology Demonstration Pre-cooler on the Test Stand II S=ELSO REQUIREMENTS SKYLON Based European Launch Service Operator As part of its on-going work in launcher development ESA generated a set of requirements Given that SKYLON is a venture based in the United for a next generation European launch system. Kingdom, it is natural that the British Government These requirements were published as a through UK Space Agency should take an interest in Specification that was included in the Request for the potential of the concept and its technologies. Proposal for the Feasibility Study for a New Although the majority of the funding has been European Launch Service (NELS) [2]. These through private equity investment a significant requirements were redrafted for the S-ELSO study public contribution has been made through ESA [4] in part to clarify the requirements where they technology development programme. Further the were ambiguous and also to reword some UK Space Agency has also placed direct consultancy requirements which had wording applicable to an contracts with ESTEC to perform technology expendable launch system to wording that was more evaluation of both SKYLON and SABRE. in line with a reusable launch system solution. It was with this background that Reaction Overall these requirements represented a Engines with an industrial team of 5 subcontractors minimum capability to sustain autonomous European and 2 supporting consultancy teams (Table 1) made a operations and that would reduce that capability from proposal to the ESA Launcher Directorate to perform that currently available with Ariane 5. This a study which would assess the degree to which a minimalist approach meant large LEO payloads and SKYLON based commercial European launch human spaceflight capability were not included. The service provider could meet the requirements that S-ELSO Study’s technical goal was to compare that ESA had generated for the Next Generation minimum capability as defined by the specification European Launcher [2]. The Study was designed to with the capability provided by the proposed S- examine the technical schedule and financial ELSO infrastructure. All the requirements were met feasibility against that specification with the purpose and the overall capability was well matched, but it of supporting ESA decision making on launch should be emphasised that the S-ELSO infrastructure service strategy by exploring the potential would inherently have other capabilities that were implications of this new launch system on future not included in the specification. This would mean European launch capability and the European that with S-ELSO Europe would not lose any overall industry that would support it. capability with the introduction of the post-Ariane 5 system, but instead gain new capabilities, such as the Table 1: S-ELSO Study Team ability to return payloads. Company Study Role Technical Study The dominant requirement was for a 6.5 tonne Reaction Engines Prime payload capability into Geostationary Transfer Orbit Airbus DS Subcontractor SOMA Engine Grafton Technology Subcontractor Spaceport (GTO). A payload capability to an 800 km Sun QinetiQ Space Subcontractor Payload carriers Synchronous Orbit (SSO) of 4 tonnes was also Thales Alenia Space Subcontractor Upper Stage Jacobs Consultant Spaceport defined. Operations in Medium Earth Orbits (MEO) 42 Technology Consultant Payload Interfaces and Low Earth Orbit (LEO) were required but no performance was specified. The requirements were Business Study Reaction Engines Prime supported by a mission model showing frequency the London Economics Subcontractor of the various missions included in the Specification and the likely mass distribution of GTO payloads. 2 The payload accommodations in terms of available envelop and loads were set to be similar to Ariane 5 but with a reduction in shock loads. The original NELS specification adopted a similar size as Ariane 5 approach to reliability, availability and responsiveness. However in the context of a reusable launcher these values are extremely low and also do not cover the ability of a reusable system to abort and return intact. So the S-ELSO specification was revised to offer higher values in all these areas as shown in Table 2 Table 2: SKYLON Operational Characteristics Current ELV SKYLON Statistically proven Mission Abort n/a <1/100 on 400 test flights Due to the impact of Payload Loss 1/50 – 1/70 <1/20,000 full abort capability Driven by the Turnaround months 2 days aeroshell inspection Could be days if Responsiveness > 1 year weeks operator required it Full launch Flexibility Limited Yes campaign in less than a week Reattempts On time Limited Yes opportunities hours apart The NELS requirements defined a first flight in 2020, but foresaw a 3 to 4 year transition to full operation. This would be the pattern for an expendable system and where launcher was an exclusive partnership between the manufacturer and the operator. In the case of S-ELSO, SKYLON has to undergo an extensive test flight programme before it is certified as operational and, because S-ELSO would be only one of many customers, it is not possible to exploit these for commercial gain. Thus the S-ELSO specification defined the date of operational service as 2024. Other requirements included; a lifetime of 20 years, costs to be competitive with Falcon 9 and Proton, operation from CSG (Kourou), low environmental impact, European autonomy III S-ELSO INFRASTRUCTURE SKYLON was designed to only reach LEO, whereas the key requirement for the next generation European Figure 3 – S-ELSO Flight Elements launch system was to launch payloads into GTO, so in order to create a complete infrastructure able to The Study identified a need for two payload meet the customer’s defined needs, additional carriers, one for small payloads and another for elements.