In aviation circles, the talk of the future involves phrases like "space planes" and "hypersonic atmospheric flight vehicles." A group presently in the spotlight is from Germany; they are carrying a roadmap for low-cost space access which involves calling upon the air passenger market for fast-travel flights.
Welcome to the world of SpaceLiner, which, when fully developed, could have dramatic impact in global aerospace. The DLR Institute of Space Systems said this suborbital, hypersonic, winged passenger transport idea is under investigation at DLR-SART. (DLR is a German aerospace research agency and it evaluates complex systems of space flight. SART is Space Launcher Systems Analysis.)
SpaceLiner is a rocket-propelled intercontinental passenger transport, described by the institute as a two-stage vehicle powered by rocket propulsion.
Guy Norris, Los Angeles-based senior editor for Aviation Week, described it as a rocket-powered system that incorporates a flyback booster and other dual-use technologies which could also be applied to "architectures for launching payloads into low Earth orbit." Conceived as a winged airliner carrying 50 passengers from Europe to Australia in 90 minutes, Norris added that, to serve a potentially larger market, DLR has also outlined a 100-seat version that would be capable of one-hour intercontinental and transpacific missions.
The concept being laid out in detail sounds like a business feasibility study as much as a technical initiative. The backdrop for all this lies in the cost factor in space transportation. This has been a key challenge. Production is one of the main cost drivers due to the very low manufacturing numbers of stages and engines. If the number of launches per year were to be increased, manufacturing and operating cost of launcher hardware would shrink. Without a new market application for space technology no improvement is to be expected, said the Institute. What could ignite a larger market?
"A new kind of high-speed transport based on a two-stage Reusable Launch Vehicle (RLV) has been proposed by DLR under the name SpaceLiner," they stated.
Liquid hydrogen and liquid oxygen will be used as propellants. They said the combination was both powerful and eco-friendly."
The reusable vehicle would be accelerated by 11 liquid rocket engines—nine for the booster and two for the passenger stage, operated using the cryogenic liquid oxygen and hydrogen.
Mark Prigg in the Daily Mail said that "Engineers predict that advances in materials could be combined with new cooling technologies and heat shielding to safeguard the SpaceLiner's structures against the intense heat of hypersonic flight."
The passenger cabin could function as an autonomous rescue capsule that could separate from the vehicle in case of an emergency, allowing the passengers to return safely to Earth.
The SpaceLiner could play a cost-cutting role by stimulating large production runs of reusable rocket engines and booster vehicles.
Martin Sippel, leader of the SpaceLiner project at DLR's Space Launcher Systems Analysis group, talked to Aviation Week about these plans.
"We could increase hundredfold the number of launches and, as it is a reusable vehicle designed for between 150 and 300 flights, you have serial production of engines. If you have 11 engines per vehicle then you would build 2,000 engines per year or so. That's a huge production run, and that was the motivation."
The concept involves a two-stage, vertical-takeoff configuration of a large unmanned booster and a manned stage designed for 50 passengers, for example, and two crew members. The fully-reusable vehicle is accelerated by a total of eleven liquid rocket engines (9 for the booster, 2 for the passenger stage), which are to be operated using cryogenic liquid oxygen (LOX) and hydrogen (LH2).
After engine cut-off, the orbiter stage is to enter a high-speed gliding flight phase and be capable of traveling long intercontinental distances within a very short time. Altitudes of 80 kilometers and Mach numbers beyond 20 are projected, depending on the mission.
Long-distance trips such as Europe –Australia could be accomplished in 90 minutes. An intercontinental route between Europe and North-West America could be reduced to flight times of slightly more than one hour.
We are talking about a new era, potentially, of rocket-based, ultra-fast transportation as a new application for launch vehicles.
The group mentioned other intercontinental missions, which potentially could generate market demand.
With SpaceLiner travel, the thinking is that production rates of the reusable launch vehicles and rocket engines could increase hundredfold.
What's next on their roadmap? Norris said that early concept reviews would take place around 2016-17; the next review, in 2019-20. After that, Norris described various next steps before building the first hardware in 2030. Flight tests of the prototype could begin in 2035, with service entry in the 2040s. "It sounds a long way off into the future but we need to achieve our 2020 goal of funding, otherwise we cannot keep these later dates," Sippel said in Aviation Week.
Space Launcher Systems Analysis
The SART (Space Launcher Systems Analysis) group has the task of examining all types of future space launch systems and the thereof required engines by means of modern, computer-aided methods, while also utilizing the Concurrent Engineering Facility (CEF) at the DLR Institute in Bremen. One of the fundamental aims is to reduce the cost of access to space through the identification of viable technologies. Activities range from stand-alone preliminary studies to critical analysis and assessment of foreign concepts. Thanks to integrated vehicle and engine analysis performed within a single group, SART fills a unique position within the German space sector.
Together with its continuous strive to improve simulation techniques, SART also participates in the analysis of new technologies such as the currently investigated ceramic combustion chamber. Another key aspect of SART's role is the professional support provided in the definition of the German space development strategy.
SART held the system leadership for the ASTRA 2 concept (reusable booster, namely the LFBB for a future variant of Ariane 5) and works in close cooperation with industry (EADS Astrium, MT-Aerospace) as well as with DLR Institutes in Cologne, Braunschweig, Stuttgart, and Lampoldshausen on the initial outline that makes further steps in launcher development possible.
Moreover, through internal workshops innovative proposals are developed by the SART-team. These proposals intentionally diverge from conventional ideas. The visionary concept SpaceLiner under study by SART aims at creating an ultrafast passenger transport capable to cover distances like Europe-Australia within 90 minutes. The patented "in air-capturing" method by which a reusable booster stage is captured by a towing-aircraft and then returned to the launch site is another example.
SART is currently involved in different EU funded studies of hypersonic fligh like LAPCAT, ATLLAS, and FAST20XX. WOTAN and VENUS are projects that aim to develop new proposals for future expendable launcher concepts and SART is participating in the federating project "Upper Stage", coordinated by the DLR Institute for Space Systems, Bremen.
SART analyses take place in a frame of national and international cooperation.
History of development
First proposed in 2005, the SpaceLiner is under constant development.
Different configurations in terms of propellant combinations, staging, aerodynamic shapes, and structural architectures have been analyzed. A subsequent configuration numbering has been established for all those types investigated in sufficient level of detail. The genealogy of the different SpaceLiner versions is shown in the following figure. The box marks the configuration trade-offs performed in FAST20XX in 2009/10. These configuration studies supported the definition of the next reference configuration SpaceLiner7.
At the end of 2012 with conclusion of FAST20XX, the SpaceLiner 7 reached a consolidated technical status.
The general baseline design concept consists of a fully-reusable booster and passenger stage arranged in parallel.
The two-stage, vertical-takeoff configuration concept consists of a large unmanned booster and a manned stage designed for 50 passengers and 2 crew members. The fully-reusable vehicle is accelerated by a total of eleven liquid rocket engines (9 for the booster, 2 for the passenger stage), which are to be operated using cryogenic liquid oxygen (LOX) and hydrogen (LH2).
Sketch of SpaceLiner 7-2 launch configuration with passenger stage on top and booster stage positioned below
The concept design also foresees the passenger cabin to function as an autonomous rescue capsule which can be separated from the vehicle in case of an emergency, allowing the passengers to return safely to Earth.
After engine cut-off, the orbiter stage is to enter a high-speed gliding flight phase and be capable of traveling long intercontinental distances within a very short time. Altitudes of 80 kilometers and Mach numbers beyond 20 are projected, depending on the mission. Flight times of the SpaceLiner from Australia to Europe should take just 90 minutes or no more than 60 minutes on the Europe – California route.
Acceleration loads for the passengers on these missions are designed to remain below those of the Space Shuttle astronauts, with a maximum of 2.5 g being experienced during the propelled section of the flight.
Several other shorter intercontinental missions exist, which potentially generate a larger market demand. For this reason a SpaceLiner configuration derivative has been studied, which could transport up to 100 passengers. In order to keep the number of different stage configurations at the lowest possible level, the potentially interesting flight destinations have been divided into three classes:
Class 1: Reference mission (up to 17000 km) Australia – Europe with 50 passengers orbiter and large reference booster
Class 2: Mission (up to 12500 km) e.g. Dubai – Denver with increased 100 passengers orbiter and large reference booster
Class 3: Mission (up to 9200 km) e.g. Transpacific with increased 100 passengers orbiter and reduced size booster
These three mission classes could be served flexibly by a suitable combination of four different vehicles (however with a lot of commonality in subcomponents such as engines): 50 and 100 passenger orbiter stages, and large and shortened boosters.
Several advanced technologies are required for the realization of the SpaceLiner which are currently under investigation at DLR and with international partners.
A few examples:
The SpaceLiner 7 achieves an excellent hypersonic L/D of 3.5 up to M=14 without flap deflection, assuming a fully-turbulent boundary layer. Mach contours of SpaceLiner 7-1 passenger stage at M= 10, angle of attack alfa = 6° from ESA-ESTEC Euler CFD- calculation:
Staged combustion cycle rocket engines with a moderate 16 MPa chamber pressure have been selected as the baseline propulsion system. The engine performance data are not overly ambitious and have already been surpassed by existing engines such as the SSME or RD-0120. However, the ambitious goal of a passenger rocket is to considerably enhance reliability and reusability of the engines beyond the current state-of-the-art.
The maximum acceptable temperature of any passive TPS on the SpaceLiner is 1850 K. The leading edge and nose areas exceed this limit and need advanced active cooling.
In those areas where the heatflux and temperatures exceed those values acceptable for CMC, transpiration cooling using liquid water is one potential technical option. This innovative method has been experimentally tested in DLR’s arc heated facility in Cologne using subscale probes of different porous ceramic materials.
MAKS: Germany’s hypersonic SpaceLiner concept solidifies
Ten years after the project was conceived, the German Aerospace Centre’s SpaceLiner could soon enter a new design phase with a “mission definition review” planned for 2016.
The idea is to produce a two-stage, reusable hypersonic space vehicle that could transport 50 passengers from Europe to Australia in 90 minutes.
Leonid Bussler of the German Aerospace Centre’s Space Launch Systems Analysis (SART) group says the project is currently in “Phase Zero,” where the range of vehicle concepts are narrowed down to a single, baseline configuration through wind tunnel testing and performance trade-offs.
The mission review, which will be scrutinised by an outside panel of experts, marks the transition to Phase A, where the team moves forward to a preliminary design under a single concept.
The latest concept, dubbed SpaceLiner 7, was singled out in 2012 and a model was on display at Russia’s MAKS air show in Moscow this week.
Bussler tells Flightglobal that SpaceLiner 7 is “very close” to the final configuration the team expects to move forward with.
It’s comprised of an 84m booster stage powered by nine liquid oxygen/liquid hydrogen rocket engines, and a twin-engine passenger stage that would travel at hypersonic speeds to the edge of space before descending to its final destination.
“We are not relying on any air-breathing propulsion; we are using rocket propulsion,” he says. “Both stages are reusable. The same engine is used on the booster stage and the orbiter.”
Bussler says there are still many obstacles to overcome, like developing a thermal protection system capable of overcoming the extreme temperatures experience in hypersonic flight.
The other piece is regulatory, since there is currently no way to certify this type of spaceplane for commercial passenger transport, and it must transit through several countries on decent. The group is also a long way off deciding which countries would launch and receive the vehicles.
“The operation would have a fleet of about 40 vehicles flying on different connections,” Bussler says. “It’s a hyper-fast transport possibility, but it has a touch of tourism because every passenger would go to the edge of the atmosphere and to the edge of space and become kind of a space tourist.
“But it is intended for commercial use by people who need to go fast from one continent to another.”
Under the concept, the booster would reach an altitude of 246,000ft (75km) at speeds of 3.7km/s (approximately Mach 14), and the second stage would peak at 262,500ft and reach speeds of 7km/s (Mach 24).
The sealed cockpit and passenger compartment will be designed to separate in an emergency, and each seat might be encapsulated to overcome any loss of cabin pressure.
SART’s “cautious target” is to have SpaceLiner in operation by 2045.
Space tech meets aviation: The hypersonic revolution
London to Melbourne in 90 minutes? Paris to San Francisco in under an hour?
That's travel at 25 times the speed of sound -- or barely enough time to take in an in-flight movie.
Few areas of aviation generate wilder predictions than hypersonic flight -- but a team in Germany might just have cracked it.
Hypersonic means speeds of Mach 5 or over, or more than five times the speed of sound. Supersonic is Mach 1, or the speed of sound.
Since the withdrawal of the Concorde in 2003, commercial aviation has remained purely subsonic, but that could change in the coming decades.
Take new aircraft concepts like the Japanese HYTEX, capable of speeds of Mach 5, or the European Lapcat-II, expected to reach Mach 8.
Then there's the nascent space tourism industry, with companies such as Virgin Galactic and XCOR Aerospace hoping to take a select few on leisure trips to the edge of space.
Researchers at the German Aerospace Center (DLR) are taking their own approach.
A team has applied space technology principles to propose what is possibly the world's most advanced hypersonic airliner concept to date.
The result of 10 years of ongoing research by the Space Launcher Systems Analysis (SART) department at the Institute of Space Systems in Bremen, the SpaceLiner is a revolutionary hypersonic spaceplane concept capable of flying some 50 passengers across the globe at speeds of up to 25 times the speed of sound.
It's based on a two-stage concept, not unlike the Space Shuttle, where both the booster and passenger stages start in an upright configuration.
Propelled by 11 rocket engines during launch (nine on the booster stage and two on the passenger stage) the system accelerates into the mesosphere using traditional cryogenic rocket propulsion.
Once the booster stage is empty, the smaller passenger vehicle separates from the booster stage and continues accelerating, flying autonomously, just like an aircraft -- except that it does so while reaching astonishing speed of up to Mach 25.
After reaching a maximum altitude of about 80 kilometers, the passenger stage commences a gliding descent towards its destination.
Not only is the SpaceLiner concept incredibly fast, it's also environmentally friendly.
It uses liquid oxygen and liquid hydrogen (LOX/LH2) propellants so only water vapour is produced.
Most of the flight processes will be fully automated, but there would still be two pilots to monitor all onboard and flight procedures -- and to provide reassurance to passengers.
Re-usability is key
Traveling at Mach 25? Better choose one of the shorter in-flight movies.
With performance like this, it'd be possible to go from Europe to Australia in 90 minutes.
The SpaceLiner hopes to capture a slice of the existing very-long-haul premium air travel market, but this will only be possible if costs can be brought down to a reasonable level.
Up until now everything that relates to space travel has been prohibitively expensive, which explains why this field has remained the preserve of a handful of governments and ultra-rich individuals.
SART researcher Dr. Olga Trivailo explains that the high costs are "due to limited technology application and, thus, demand, which underpins low production rates of space systems."
One of the keys to lowering costs, and a cornerstone of the SpaceLiner project, is re-usability.
The SpaceLiner vehicle is designed to be fully re-usable, from the system's engines, to the passenger vehicle and the booster stage, which would be able to return independently to the launch site after separating from the passenger stage.
The rocket engines are expected to withstand at least 25 launches, while both stages might last up to 150 cycles.
The DLR engineers have avoided relying on any untested technology.
It'd add too much complexity, risk, and development time to what is already an extremely complex project.
A laboratory for new ideas
The SpaceLiner's passenger stage will start off in an upright position, meaning that seating arrangements will need to differ from those of conventional airliners.
During the first 10 minutes of flight, passengers will experience forces of up to 2.5G -- 2.5 times their body weight on Earth, or about half the G forces you'd get on a roller coaster.
There's no need for passengers to undergo special training as they would with space travel, but the advent of hypersonic flight still presents a great opportunity to test new passenger cabin concepts.
Architects and designers have been brought into the SpaceLiner project to help devise the passenger experience of the hypersonic era.
Wealthy investors will be needed to make the concept work.
The hypersonic flight market
Even if costs can be brought down, hypersonic flight is likely to remain a premium product, at least at the beginning.
The number of potential routes flown by the SpaceLiner would be limited to intercontinental distances of more than 9,000 kilometers, where the time-saving would be most beneficial.
Potential routes could include Australia to Europe, as well as linking destinations in the Far East, Europe, America's West Coast and the Trans-Pacific market.
The SpaceLiner would need space ports to be strategically located close to main population centers and business hubs in order to capture business traffic, while at the same time being sufficiently removed from densely populated areas in order to minimize noise issues during take-off.
Coastal locations are the most desirable so that the starting phase can occur over water.
SART has already identified several suitable launch sites in Europe, Australia and the U.S. that meet these criteria, with the Netherlands' north coast being a particular favorite.
How will we fly in 2050?
It will take some time to fly hypersonic
According to SART's own estimates, SpaceLiner flights are still a few decades away, maybe as much as 30 years.
If it's ever to become a reality, the SpaceLiner will need the involvement of the aerospace industry as well as investors with deep pockets.
Dr. Trivailo estimates that the SpaceLiner would require an initial investment of 28 to 30 billion euros ($30 to 32 billion) to make it to the prototype stage.
But there's a lot more to the SpaceLiner than flying passengers faster across continents.
By designing a fully reusable space system for regular passenger traffic, SART researchers hope that their work will make space travel more cost-effective.
If their space hardware went into serial production, costs might be brought down and space travel would be more accessible to more people.
Don't pack your suitcase just yet, but affordable space tourism could be that little bit closer to reality.
Quelle: Business Traveller