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J Engineering ISSN: 2168-9792

Editorial Open Access Human Spaceflight and Hypersonic Re-entry Vehicles: Looking Backward to Step Forward Raffaele Savino* Department of Aerospace Engineering, University of Naples Federico II, Italy

The main elements characterizing cutting-edge research and tech- Waiting for Single-Stage-To-Orbit (SSTO), expendable launchers nology in future human spaceflight and space exploration will certainly appear to be sufficiently reliable; what is still lacking is a reentry air- be related to the development of new access-to-space and atmospheric plane that is as simple and as light as a glider and that can land at any reentry systems. conventional airport within a large footprint. The termination of the Space Shuttle program corresponds indeed Hypersonic slender vehicles concepts are not new. Many studies to a radical change of the scenario for human space flight activities. began worldwide on winged, fully reusable launchers and hypersonic Along with the Russian Soyuz and the Chinese Shenzhou reentry cap- spaceplanes (HOTOL in the United Kingdom, Saenger in Germany, sules, the Shuttle was the only available human-rated vehicle able to Star-H in France, National Aerospace Plane and HL-20 in the USA, provide human access to Space. Continuous utilisation of the Interna- Hermes in Europe). Most of these concepts were abandoned due to lack tional Space Station and new exploration programmes will require new of funding or to the unavailability of materials able to withstand ex- space vehicles for access-to and reentry from space. tremely high temperatures. The most ambitious space missions for humans call ever more for a In particular, since early 60’s NASA developed studies on the XL-20 safe return, at least from Low Earth Orbit (LEO). Human space explo- Dynasoar, a large hypersonic reentry glider concept, based on a high ration, Space Station operations, and future space tourism will have all lift-over-drag winged vehicle, able to dissipate the very high initial ki- an obvious common denominator, which is also a necessary require- netic energy by means of a long reentry maneuver. However, as soon ment: a safe re-entry. as President J.F. Kennedy announced the decision to send a man on the Moon, and bring him back on Earth in a decade, all resources were The short term solution of a capsule-like return vehicle convinced addressed to the Apollo program led by Von Brawn and his Huntsville most nations to choose ballistic or semi-ballistic vehicles adopted for group, and the Dynasoar was canceled. The main reason was essentially long time, with all the operational constraints and limitations that this due to the available thermal protection materials that at that time were choice may bring. An example is the reusable Dragon commercial cap- ablative (as nylon phenolic or quartz) and not reusable, impacting very sule, developed by SpaceX, successfully launched to the ISS and recov- much on the vehicle payload and on the efficiency of the entire system. ered from orbit on 25 May 2012. Exploitation of aerodynamic lift forces suggests new and more comfortable ways of crossing the atmosphere. High lift, low wing loading reentry vehicles, as recently proposed in The development of a winged vehicle as a crew return system appears Europe, may represent the right answer for the future demands of space to be the most appealing breakthrough in terms of safety, comfort, ex- exploration, Space Station operations, and space tourism. The definitive penses and flexibility. Shuttle retirement and the necessity to serve the International Space Station (ISS) does not give much time to develop new Crew Return Ve- It is the authors’ opinion that the future in this field will reserve in- hicles (CRV), and it appears more adequate to start everything from the novative solutions to revolutionize space transportation, reaching space scratch. Attention should be given to the increase of the gliding capac- by conventional airplanes, similarly to the Space Ship One launched by ity during the reentry phase, in order to obtain a more maneuverable Scaled Composites for its first flight on October 4, 2004. system similar to today civil aviation, looking at the minimization of If we take a look into our future, the most likely customer for hu- the risk associated with the traditional way to reenter from space and man space transportation will be space tourism, and it is highly unlikely to the strong mechanical loads coupled to high heat fluxes occurring in that any tourist will be willing to make a high risk and uncomfortable relatively short reentry time. return to Earth in a stone-like capsule; a piloted, glider-like vehicle with Such scenario represents a first step toward new solutions for both horizontal landing would appear to be the only option. reentry systems from LEO and reusable launchers (RLV). The new con- figurations will be based on the utilization of ultra-high-temperature ceramic materials, today partially available, able to sustain very high

*Corresponding author: Raffaele Savino, Department of Aerospace Engi- neering, University of Naples Federico II, Italy, Tel: +390817682357; Fax: +390817682351; E-mail: [email protected]

Received July 18, 2012; Accepted July 19, 2012; Published July 20, 2012

Citation: Savino R (2012) Human Spaceflight and Hypersonic Re-entry- Ve hicles: Looking Backward to Step Forward. J Aeronaut Aerospace Eng 1:e106. doi:10.4172/2168-9792.1000e106

Copyright: © 2012 Savino R. This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted Figure 1: Artist concept of a high-lift-over-drag spaceplane attached to the use, distribution, and reproduction in any medium, provided the original author and International Space Station (ISS). source are credited.

J Aeronaut Aerospace Eng ISSN:2168-9792 JAAE, an open access journal Volume 1 • Issue 2 • 1000e106 Citation: Savino R (2012) Human Spaceflight and Hypersonic Re-entry Vehicles: Looking Backward to Step Forward. J Aeronaut Aerospace Eng 1:e106. doi:10.4172/2168-9792.1000e106

Page 2 of 2 surface temperatures, in the order of the radiative equilibrium tempera- From the other side, the research group of the University of Naples ture associated to the atmospheric reentry. proposes to study a new manned hypersonic vehicle, able to reenter from ISS as a glider, following a number of joint DIAS (University of Relevant knowledge has been developed in Europe during the last Naples) and OHB-System (Bremen) studies. decade, to create the conditions for a real leadership in the field, thanks to the recent EXPERT and IXV projects. Coherent with this logical The very recent activities at Stratolaunch Systems (Huntsville) and line, from one side the IXV ESA project will probably be reoriented the Space Port (New Mexico) confirm the renewed interest for manned to guarantee a launch with Vega, the injection into a low Earth orbit, missions that will take full advantages of the aerodynamic lift forces the execution of some mission critical operations, and a fully autono- during both the ascent and re-entry phases of airplane-like vehicles. mous unmanned re-entry capability, including horizontal landing on Current studies at the University of Naples in Italy try to combine an airport. Along the same line, in Italy, CIRA and ASI are looking at the high lift-over-drag spaceplane and the air launch concepts, by the development of an unmanned reentry vehicle, to be developed in means of a flying launch pad, as proposed by Burt Rutan in USA, to collaboration with JAXA. provide a safe and comfortable human trip to/from the ISS (Figure 1).

J Aeronaut Aerospace Eng ISSN:2168-9792 JAAE, an open access journal Volume 1 • Issue 2 • 1000e106