Per PHOENIX and ASTRA

Citation

Obersteiner, M. (2001), "Per PHOENIX and ASTRA", Aircraft Engineering and Aerospace Technology, Vol. 73 No. 4. https://doi.org/10.1108/aeat.2001.12773daf.001

Per PHOENIX and ASTRA

Per PHOENIX and ASTRA

Reusable launcher systems: new impulse for space

In practically all spheres of human life, the utilization of space is gaining in importance. Satellites with such varying applications as, for example, communications, Earth observation and monitoring of the environment directly affect our daily lives. The International Space Station that is now being built in orbit will be a unique research centre. Its utilization is destined to lead to new types of products and processes for applications on Earth – and beyond.

In general, international space activities are characterised by two developments. On the one hand there is a growing need to transport payloads to various positions in orbit. On the other hand, the number of countries that offer launch services is increasing. Not only the USA but also Russia and China are systematically expanding their capacities, developing existing launcher systems further or are already working on the development of new systems. To safeguard its competitive position and its own sustained, independent access to space, Europe must intensively face up to this development process.

The market, too, demands new concepts for transport technologies. To hold their own against the international competition, all market players must substantially lower the present level of cost. One path in this direction is to increase the payload capacity of the European launch vehicle Ariane 5. Even so, European launch providers need at least one additional option to be able to offer cost-efficient and flexible launching services also in the long term.

The result of numerous studies is the concept of a reusable launch system. With its future European space transportation investigation programme (FESTIP), the European Space Agency (ESA) has created the basis for this and will be working out corresponding approaches to the development work in further preliminary programmes. To prepare and expand the technological strengths of German companies and institutes with this aim in mind, the German national programme ASTRA (selected systems and technologies for future space transport system applications) has been initiated as a supplementary measure. ASTRA promotes German system competence in this technological field with the objective of being able to submit competitive offers in the development phase of a new European transport system.

ASTRA focuses on the development and testing of the demonstrator to prove the system and the technology – PHOENIX. Jointly financed by private enterprise, the Federal German government and the governments of the Laender (Federal German States) PHOENIX makes a decisive contribution to verifying the operational capability of a future space transportation system.

The ASTRA Programme

The German national programme ASTRA was launched in the year 2000 under the lead of the German Aerospace Centre (DLR). Among other things the programme includes system studies and technology developments with the target of starting the phase of the European development of a concrete launcher system in the year 2004. The programme is funded with some 40 million Euro, and about 40 per cent of this figure is earmarked for the development of the test launcher PHOENIX.

The basis of ASTRA is the knowledge that return, landing and renewed use of a transport system are indispensable prerequisites for autonomous European activities in this field. However, until now Europe has lacked the necessary system competence for re-usable systems, which is considerably further developed in some other countries – above all in the USA. Complete system competence, some aspects of which are available from the Ariane programme, requires:

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  launch (flight preparations, payload integration, ground infrastructure);

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  ascent (trajectory control, staging);

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  delivering the payload (necessary mechanisms and upper stages);

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  return (re-entry technology, trajectory tracking and telemetry, manoeuvring in the hypersonic range);

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  landing (correction of re-entry trajectory deviations);

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  re-use operations (inspection, maintenance and repair, transport back to the launch site).

ASTRA came about on the initiative of European's number one space company Astrium and is exemplary for a future-oriented technology programme on a public-private partnership basis. To safeguard their own competitive ability in the long term, the participating companies (Astrium, MAN-Technologie, OHB-System and Kayser-Threde) are investing substantial funds of their own. Central co-ordination and management, especially within the framework of the development of PHOENIX, is the responsibility of Astrium Space Infrastructure Division in Bremen.

From the public sector, substantial promotional funds are being provided not only by the Federal government but also by the Federal State of Bremen; also involved in the programme are the Centre of Applied Space Technology and Microgravity (ZARM) at the University of Bremen as well as three special research departments of the German Society for the Advancement of Scientific Research (DFG) at the Technical Universities of Aachen, Munich and Stuttgart. Astrium itself contributes comprehensive know-how, for example in the fields of flight control and re-entry technology. Within the framework of a co-operation between Europe and the USA, the Astrium Space Infrastructure Division is, for example, deeply involved in the preliminary development of an astronaut rescue vehicle for the International Space Station. The corresponding technology demonstrator X-38 has already successfully completed several test flights; among other things these also used a system delivered by Astrium that ensures the automatic landing of X-38 by parafoil with high precision.

The demonstrator: PHOENIX

Many of the technologies necessary to develop a re-usable space transportation vehicle have already been tested or are currently at an advanced stage of development. The next step necessary on the way to producing an operational system is now the construction of the demonstrator PHOENIX. Although computer simulations and wind tunnel tests greatly facilitate design, in view of the large number of different physical forces that act during the flight through the atmosphere as well as influences that are theoretically only very difficult to predict, the results of practical experience remain the most important foundation for further development work.

The test launcher, which is being built at the Astrium site in Bremen, is just under seven meters long, has a wingspan of 3.8 meters and a weight of 1,200 kilograms. The fundamental design of the system follows the experience that has already been gained with comparable flight vehicles – such as for example the US Space Shuttle: the wings and control surfaces of the system configuration that is to be tested have, for example, been reduced to the absolutely necessary minimum dimensions. The body is designed to provide the biggest possible internal payload capacity so that even relatively large communications satellites can be transported. The generously dimensioned tail area offers sufficient room to accommodate propulsion systems with high thrust.

During the flight tests, PHOENIX will initially have no propulsion system of its own. The objective of the tests is to find out how the vehicle behaves during a steep landing approach and the subsequent automatic touch-down. To this end, PHOENIX will be flown to a height of some 3,500 meters by a helicopter and then dropped. A GPS-based navigation system and sensors on board – for example, a radar altimeter – control and monitor the flight path and measure all the relevant data. The evaluation of these data later forms the basis for the system design of the operational system.

The development and integration of PHOENIX and the flight experiment as the true objective of the demonstrator project require a financial outlay of DM31.5 million. Private enterprise (Astrium and the medium-sized Bremen aerospace company OHB-System GmbH) are contributing DM14.8 million of their own towards this sum. As it is a question of a project that will mainly be implemented at the aerospace site of Bremen, the state of Bremen is also contributing DM10.5 million. The remaining costs will be covered by the Federal Ministry for Education, Science and Research and by the German Aerospace Centre DLR. The development, integration and testing of PHOENIX are scheduled for completion by the end of the year 2003.

The future: HOPPER

Parallel to the PHOENIX project, Astrium is already working on the concept and initial design of the operational system: HOPPER.

HOPPER is distinguished by a high degree of re-usability and comparatively low mission costs. Above all the experience gained with the US space shuttle is being taken into account here. The biggest cost factors connected with operation of the shuttle vehicle are the expensive maintenance of the heat shield as well as the extremely powerful propulsion systems. New materials and reduced performance requirements for the propulsion systems will substantially reduce the maintenance for the HOPPER. A further contribution to cost reduction is the horizontal launch of the HOPPER: on a skid sled running on an approximately four kilometre long track, which, due to its favourable position near the equator is to be set up at the European Space Centre in Kourou/French Guiana. The concept of the skid sled is being investigated within the framework of ASTRA and is oriented to the emergency running system of the maglev high-speed train Transrapid.

In general, the plans envisage the use of as many existing technologies as possible to substantially reduce the costs of HOPPER as compared with an entirely new development. This also includes using a further development of the present Vulcain-type propulsion systems from Ariane.

During a typical mission, HOPPER reaches an altitude of 130 kilometres only a few minutes after launch. At this point the payload – as a rule a satellite together with an upper stage – is jettisoned from the tail of the HOPPER; after ignition of the upper stage, the payload is delivered to the planned position in low-earth or geostationary orbit. Meanwhile, HOPPER automatically returns to Earth, but due to its trajectory it cannot land back at the launch site. It is planned to use external landing sites in the territory of ESA member states, possibly on the Azores or other islands in the Atlantic. The shuttle vehicle is then transported back either by ship or, as a future alternative, directly and fast from the landing site to the launch site with the aid of the Cargo Lifter that is currently being developed.

Should any technical problems arise in a propulsion system during a launch, the propellant on board of HOPPER can be pumped out over water. HOPPER then returns to Earth at one of the external landing sites without it being necessary to give up the payload for lost.

The use of HOPPER as a re-usable European space transport system is capable of realisation by the year 2015.

Michael Obersteiner