S4 - A demonstrator of HYPLANE, a single stage suborbital spaceplane and a hypersonic business jet
Introduction
In recent years, some private enterprises have been approaching Space Flight with a relatively low-cost philosophy. Available survey studies assessed the potential market for suborbital vehicles, showing that there is a potential sizable market for suborbital tourism. Number of people willing to pay around 200 k€ for this experience could be in the order of 50,000, just 15 years after the market start [[1], [2], [3]]. This market is of course much larger than the one related to orbital space tourism missions. In the case of ISS, in fact, only 7 people had the opportunity, up to now, to perform this experience paying from 20 M$ to 52 M$1,2 even though some companies are talking about offering such an adventure at lower prices, both around the Earth and the Moon.
Secondary markets directly linked to the commercial sub-orbital flights will include microgravity research, high altitude aerospace technological testing and development, astronauts training, remote sensing and so forth. Although many believes that such situation will rapidly evolve toward much more interesting business numbers, this market size still does not support definitively the development of a new aircraft/spacecraft, and this is the reason why only pioneering enterprises are playing this role today.
On the other side, today's business world is becoming faster and faster and it requests a transportation system to follow these needs adequately. The business jet market represents, today (before the COVID-19 pandemic), the aviation industry segment with the largest growing potential [4]. In particular, high-speed point-to-point flights address in large part the segment of urgent business travel for passengers as well as fast cargo transportation for special goods/products such as mail and express, pharms, valuables live, perishable goods, transcontinental organ transport.
The aviation industry has always brought enormous social and economic benefits to the whole world, facilitating people traveling and connecting, allowing business growth and increasing prosperity of countries. There is a move today that brings the reintroduction of civil supersonic flight [5,6] closer to reality, which will boost these positive effects. However, these benefits may have side effects on the environment and on people that leave in the proximity of airports. Despite aviation is accountable for only 2% of the total human-caused greenhouse gas emissions, the sector has decided to take responsibility and lead the way for a greener aviation.
Let us remember that Concorde [7] was the last supersonic commercial aircraft and its programme ended in 2003 also because of its impact on environment larger than other types of aircraft. On top of this, it is required to understand the effects that the introduction of new and greener supersonic aircraft would have on the ATM and, in general, on safety [5,6]. The ICAO Committee on Aviation Environmental Protection (CAEP) is developing a Standard for future supersonic aircraft, and discussions continue on the sonic boom measurement schemes and procedures. The goal is to establish technical flight test procedures for enroute (sonic boom) noise certification. These would be in addition to the certification requirements for the landing and take-off (LTO) conditions. It is anticipated that the certification of a supersonic aeroplane could occur in the 2025 timeframe.
Most of supersonic or hypersonic commercial designs have tended toward large aircrafts (e.g., Antipode, Skreemr, Spaceliner, Zehst, Skylon, Stratofly, Virgin Galactic Mach3 and others), characterized by hundreds of tons of mass and hundreds of passengers. This has up to now resulted in very expensive operational concepts and “none of the concepts was economically sustainable over its whole life cycle” as reported in Ref. [8]. In addition, the system concepts have been often very complex with – for example – different types of engine simultaneously installed on the aircraft, requiring very long time to reach the required Integration and System Readiness Levels (Stratofly targets a TRL 6 in 20353). It is the authors' belief that this situation will persist for some decades still needing substantial R&D effort and technological/market maturation. On the contrary, the development of small supersonic/hypersonic aircrafts offers much better perspectives from both technical and economical points of view, as also indicated in Ref. [7], as the advanced development stage of Aerion's AS2 and Boom's XB1 business jets gives evidence of.
The scientific and industrial background of the members of the Campania Aerospace District (DAC) includes leadership and participation in projects like USV, Phoebus, Hytam, IXV, Lapcat, Space Rider, Hexafly, Hyplane, Stratofly. Based on this heritage and coherently with the Smart Specialization Strategy of its Region, DAC is supporting the HYPLANE concept focusing on enhancing technologies compliant with small supersonic/hypersonic business jet for passenger transport and suborbital aircraft for tourism and microgravity experimentation, training as well. A dedicated working group is in place at DAC, formed by representatives of industries (large enterprises as well as SMEs), several research organizations and universities.
The concept of a small hypersonic plane was originated from these considerations, in the perspective to satisfy very special requirements of both sub-orbital space flight and ultra-fast transportation [1,[9], [10], [11], [12]], addressing the action “safer and greener aviation in a smaller world”, inspired by the following targets of the European Commission's Space Strategy for Europe4 and Aviation Vision5:
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Maximize the benefits of space for society and the EU economy, by promoting the exploitation of altitudes between Flight Level 600 (= 18 km) and 100 km, which are currently underused;
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Contribute to a more competitive European aerospace sector, through the development of a very innovative concept for commercial aerospace transportation;
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Reinforce Europe's competitiveness and autonomy in accessing high altitudes in a safe and environmentally friendly manner, by making aircraft cleaner and quieter to minimize transport's systems' impact on climate and the environment;
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Make Europe the safest air space in the world and provide the best products and associated services in air transport, carrying travellers and their baggage from door-to-door, safely, affordably and quickly.
Section snippets
The HYPLANE concept
HYPLANE (see Fig. 1) is a new concept of ramjet-based hypersonic small transportation system conceived to offer suborbital space flights for space tourism perspectives as well as very fast flights, shortening time to connect two airports within the door-to-door target in the frame of the “urgent business travel” market segment. The concept is based on the access to space from stratospheric reference altitudes (30+ km) as safe as today's commercial air transportation.
The reason to propose the
Configuration
HyPlane is a delta-wing hypersonic airplane for a suborbital space tourism mission and for urgent business travels, so it must have the highest possible aerodynamic efficiency. There are two major reasons for a high lift-to-drag ratio: the first is the general requirement of minimization of the thrust and the second is a higher manoeuvrability of the aircraft.
HYPLANE is a concept of hypersonic spaceplane able to offer access to suborbital space and stratospheric flights as safe, convenient and
Ambition
The philosophical ambition of the designers is to contribute in closing the gap between aeronautics and space. They in fact believe that it is the key to dramatically decrease the costs of access to space and consequently support the already born expansion of humanity in space [19,32]. Present available technologies, which eventually require only some enhancements, fully support the implementation of the mentioned philosophy for the access to the suborbital space, and this is the reason why
Impact
Overcoming some technological and administrative barriers (e.g., ATM regulations and procedures) the high-speed aircraft development will result in benefits for the users that can be divided in: (a) economics, i.e. High Net Worth Individuals (HNWI), for whom time is money, and (b) social, all the population that will benefits from “fast cargo transportation” availability. There is also a third group of users in a sense, which is composed of managers and exploration spirits. For all of them,
The S4 demonstrator
It has already been said that the market estimates with specific regards to the suborbital part are encouraging but still not robust or even credible because of lack of data (the segment is still at its inception). This is the main reason why the entire suborbital flight industrial scene today dominated by left few pioneering rich entrepreneurs.
The way to pursue the game is to reduce the initial investment by focusing on somewhat limited performances and non-certified commercial products. This
The suborbital test polygon (STEP)
One of the issues in developing the access to suborbital space is commonly felt to be the identification and realization of spaceports. The perimeter of spaceports in terms of requirements is very wide and still not standardized. One of the reasons is that the sector is still at its beginning and space is available for different ideas or solutions. A first distinction must be done between institutional and commercial infrastructures, the first including all space launch site on Earth as well as
Concluding remarks
Space Tourism market will start and spread all over the world guaranteeing much cheaper ticket price than offered today. Meanwhile, it is clear that aviation will relatively soon evolve to include high speed systems. They will guarantee much better opportunities for fast transportation of individuals and goods using many of the world small-medium airports.
In this scenario, new aerospaceplane designers and manufacturers will emerge worldwide as well as new airline companies offering such
Declaration of competing interest
The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.
Acknowledgements
The HYPLANE project has been conceived by Gennaro Russo and Raffaele Savino. The company Trans-Tech Srl and the University of Naples Federico II have conducted the feasibility and preliminary design activities, with the self-funded support by several public and private entities in Italy and abroad.
The authors are specifically grateful to the members of the DAC Working Group Hypersonics, and among other: Giorgio Fusco (Aerosoft), Michele Visone (Blue Engineering), Roberto Vitiello (MBDA Italia),
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