Flying wing aircraft, rocket aircraft, electric aircraft, when it comes to the aircraft of the future, manufacturers usually do not skimp on a variety of exotic designs. However, in practice, they are primarily engaged in the modernization of existing models, since the risks associated with a real technical revolution always seem to be quite large. At the same time, the air transportation market is constantly growing. Until now, market volumes have doubled every 15 years, and it looks like this trend will continue for at least another 20 years. First of all, thanks to the economic development of countries with economies in transition, including China.
Sooner or later, the evolutionary path of development in the field of air transportation should be replaced by a revolutionary path, the modernization of existing aircraft is costing their manufacturers more and more. The effectiveness of modernization of existing aircraft is approaching a physical limit, with this statement Rolf Henke, Head of the Air Services Department at the German Aerospace Center (DLR), agrees. Modern aircraft are becoming very difficult to improve. Considering this, 2 problems arise: all new experimental projects at the time of their implementation may show worse results in comparison with the old ones tested; however, manufacturers still have little incentive to start making their mind-blowing concepts a reality.
Fantastic ideas are currently needed only for public relations. So, for example, employees of the German Aerospace Center are demonstrating their new SpaceLiner project. This name was given to the project of a rocket plane, which is fueled with oxygen and hydrogen and is able to deliver passengers from Australia to Europe in 90 minutes. But even in the medium term, such extraordinary projects are unlikely to play any significant role in the air transportation of goods and passengers. The head of the German Aerospace Center Hencke admits that fantastic supersonic aircraft are likely not the solution to future problems.
Despite this, the Space Systems Institute of the German Aerospace Center continues to promote its own concept of a hypersonic airliner. Scientists from a number of European countries, including Germany, Austria, Belgium, Spain, Italy, the Netherlands, France and Sweden, have completed the next phase of research to develop the future of high-altitude high-speed transport, created as part of the Fast20XX project. The results of this project should be embodied in 2 programs for the creation of hypersonic aircraft SpaceLiner DLR and ALPHA Innovation GmbH. Before 2050, such aircraft are unlikely to take to the skies, but the technologies necessary for their creation are already being created.
One of the most important issues in the creation of such vehicles is the cooling of the hull. After acceleration, due to friction against the planet's atmosphere, the SpaceLiner case will be exposed to heating up to +1800 degrees Celsius. To cool the leading edge of the wings and nose of a hypersonic aircraft, German engineers propose to use active cooling based on porous ceramic materials with water circulating inside them. The rest of the aircraft's fuselage is planned to be covered with more traditional materials.
Today, porous ceramics and an evaporative cooling system have already been successfully tested in the plasma tunnel at the DLR laboratory in Cologne. In addition, work is being carried out on computer modeling of air flows near the aircraft. This work is very important, since SpaceLiner will reach very high flight altitudes, at which atmospheric pressure is extremely low and conditions exist that are very different from those experienced by conventional subsonic passenger aircraft.
In turn, the ALPHA project is distinguished by SpaceLiner and is a transport system, which should include an Airbus A330 carrier aircraft, as well as a hypersonic vehicle launched from it. A small vehicle with one pilot and two passengers on board must separate from the carrier aircraft at an altitude of 14 km, and then independently gain altitude up to 100 km. Thus, ALPHA is primarily a transport for suborbital scientific and tourist flights.
SpaceLiner will be able to transfer up to 50 passengers from Australia to Europe in 90 minutes or 100 passengers from Europe to California in 60 minutes. In order to keep within this time frame, the aircraft must fly at a speed of M = 24 or 25,200 km / h, while the flight is performed at altitudes up to 82 km. Martin Zippel, who is the project coordinator at the German Aerospace Center (DLR), said that SpaceLiner is a kind of second coming of the Space Shuttle, but with a fundamentally different task. It is worth noting that a comparison with shuttles, which even during the development period were considered not the most successful project, speaks of the confidence of the Germans in the implementation of their plans.
Currently, there is information that SpaceLiner will use vertical take-off, using closed-cycle rocket engines on oxygen and liquid hydrogen for this. Its length is expected to be about 70 meters, a wingspan of 40 meters, maximum take-off weight in the region of 1250 tons. The maximum flight range is estimated at 16,500 km. In terms of numbers, we have a typical German project: expensive, fast and at the same time expensive again. If you count it, it comes out somewhere from 12, 5 to 25 tons of aircraft weight per 1 passenger. However, the creators of the spacecraft do not hide the fact that they are not going to transport regular visitors to the establishments for the distribution of free soup. The project for the construction of this aircraft is commercial, according to them, in the next 10 years, the German Center for Aviation and Cosmonautics will be able to find commercial partners to implement its plans.
Currently, there is very little specifics around this project. Only a few details are known. In particular, it is reported that after acceleration - the active part of the trajectory and the beginning of planning, the situation with the ship's controllability will be better than that of the shuttles due to the implementation of a higher aerodynamic quality of the apparatus. Someone is puzzled by the pointed nose of a hypersonic airliner. It has been known for a long time that at speeds above M = 5 it does not give any significant advantages over the rounded one.
However, the German developers are beaming with optimism: the final shape of the new aircraft has not yet been determined and can be significantly adjusted. At the same time, the Germans are going to be guaranteed to bypass their competitors from other countries, who are going to use open-cycle hypersonic engines that take air from the Earth's atmosphere. True, such aircraft need to carry less fuel, and this makes such projects cheaper, but DLR prefers to keep silent about such trifles. At the same time, the closed cycle is best suited for high flight speeds and is already well developed, while fundamentally new technologies will not need to be created. The developers emphasize that they are not going to increase the efficiency of the engine, they preferred to focus their efforts on reusing it.
SpaceLiner at the time of separation of the first stage
The first stage of the hypersonic SpaceLiner, after the fuel has been worked out, will descend to the ground by parachute not far from the launch site (thanks to the vertical takeoff of the vehicle). On the ground, the stage can be prepared immediately for restarting. The multifaceted nature of the first stage of the apparatus is an indispensable condition for the German project. The spacecraft's built-in engines will only provide a constant speed already at a high part of the trajectory.
Based on the available information, this project raises a lot of questions. At such speeds, the flight taking off and landing over densely populated areas is excluded: and the descent first stage will strive to fall in the wrong direction, and will not be allowed to overcome the sound barrier. It turns out that sub-spaceports will have to be built in a desert area. In this regard, with Australia and California, the developers, of course, guessed, but where they will find such a terrain in Europe. If you build spaceports at sea, how long will it take to get to them, and wouldn't it be easier then to revive the old Concordes?
The aerodynamic shape of the vehicle is also unclear, which at the moment can be called traditional. Since the time when shuttles were designed, tens of years have passed and now it is already obvious that their shape was not the optimal solution. Meanwhile, SpaceLiner is clearly close to them now. The Germans may repeat the story with the Me-262 fighter. A car with the speed and motors of a new era and the aerodynamic design of the previous one. So far, the prospects for launching the SpaceLiner project by 2050 seem rather vague.
