From Hypersonics to Space Planes: A New Era

The US Defense Department's DARPA is resuming efforts to develop a hypersonic "X-plane (HX). DARPA's plans are ambitious, and will require very rapid innovation and development in order to meet its schedule -- achieving a rocket launched hypersonic craft by the year 2016.

Wired

The hypersonic X-plane (HX) will launch using a disposable rocket stack, unlike previous models which have used space launch rockets, then begin its hypersonic glide. The plan is for the "highly manoeuvrable" vehicle to be recoverable, meaning it will either return to Earth with the help of a parachute, or possibly land on a runway.

Darpa is reigniting the hypersonic flight research with the intention of launching future missions ranging from "space access to survivable, time-critical transport [troop deployment] to conventional prompt global strike." _Wired

Wired

Development of the Skylon spaceplane has passed a critical milestone following tests on the key component for its Sabre engine.

The engine, being developed by Reaction Engines Ltd, looks set to revolutionise not only space travel but also air transport around the world.

It promises to allow a new generation of aircraft to fly from one side of the Earth to the other, e.g. the UK to Australia, in just four hours instead of the 22 or so needed nowadays.

But it will also provide sufficient boost to send the Skylon spaceplane into orbit where it could deliver satellites or link up with the International Space Station.

What makes Sabre different from other aircraft engines is a revolutionary ability to switch from an air-breathing mode to that of a rocket engine.

This hybrid function will allow it to power aircraft at up to five times the speed of sound within the atmosphere or directly into Earth orbit at 25 times the speed of sound. _Wired

Hybrid engines of this type may provide a crucial weight savings in the early stages of the development of workable hypersonic craft. Engineers need to be cautious in avoiding excessive complexity in this new type of engine. KISS (Keep it simple, stupid!) is the key, as far as it is possible.

The type of craft pictured above has been discussed by Brian Wang in multiple articles. It is powered in multiple ways: by chemical rocket, air-breathing propulsion, by MHD, and by dense plasma focus fusion -- all of which should combine to allow it to travel at very high velocities. It will require significant development of several components, including the focus fusion module, before it becomes practical.

The Stratolaunch air launch system pictured above allows for a very versatile approach to orbital insertions. The huge carrier craft serves as the "first stage" of the launch system, carrying the launch craft to altitude and providing a wider range of opportunistic launch attitudes than is conveniently possible for fixed launch sites.

Ideally, all components of the system would be reusable, to save on costs. There are several tradeoffs to be made in terms of launch platforms, launch attitudes, propulsion strategies: pure vs. hybrid vs multiple etc., numbers of propulsion stages, orbital vs sub-orbital flight, method of terrestrial return, and so on.

Hypersonic flight inside the Earth's atmosphere is very punishing, physically. Better types of outer covering materials are needed to provide greater durability for multiple flights. Alternatively, inexpensive spray-on outer skins may be applied prior to each flight, which will naturally ablate in the course of the flight.

An earlier Al Fin article on this topic

Space Planes and Supersonic Biplanes

DVice features two stories here and here, dealing with the next generation of space planes and supersonic atmospheric craft. First, 5 spaceplanes you may want to keep an eye on:

1. Virgin Galactic

The heavy hitter in commercial suborbital flight right now is definitely Virgin Galactic. Its White Knight Two carrier aircraft and Space Ship Two passenger spacecraft are currently undergoing flight testing. WK2 has undergone 78 flight tests, and SS2 has done 16 glide tests. The rocket engine is being test-fired on the ground (with the most recent firing lasting the full duration that SS2 would need to make it to orbit), and Virgin plans for a fully integrated flight of SS2 later this year, which should reach 110km at Mach 3.5.

Looking farther ahead, Virgin Galactic's Vice President of Special Projects William Pomerantz said that it's "actively exploring" both point to point suborbital transportation (sweet!) and flights to low Earth orbit. As far as we know, this makes Virgin the first company to talk about point to point flights: you shouldn't go expecting a suborbital commuter flight yet, but it's exciting to think about taking a rocket plane into space to travel across the world.

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2. XCOR Aerospace

XCOR's Lynx rocketplane is undergoing hardware integration, which means that they're sticking a bunch of operational bits together to make the final spacecraft. XCOR COO Andrew Nelson promised that a prototype would be "off the ground toward the end of this year," and since Lynx is self-powered, that suggests a flight with the engines lit up and everything (although probably not to space).

XCOR also announced their first passengers and payload: researchers from SWRI (sponsors of the NSRC conference) along with some science experiments including a bio-harness for astronauts, something about asteroid regolith, and a small telescope. This highlights one of the other major markets for suborbital spaceflight besides tourism: it's possible to get some series science done in a few minutes of high-quality microgravity, and since it's not something we can replicate on Earth, suborbital flights are the going to be the cheapest way to make it happen.

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3. Blue Origin

Bretton Alexander, the director of business development and strategy over at Blue Origin, made it clear that the recent loss of its test vehicle was unfortunate, but that it "always expected to lose it during flight testing." The rest of the panel very deliberately backed Alexander up on this, saying that they all expected to lose test vehicles at one point or another and that it was just part of the process. Still, potential space tourists should certainly be aware of the risks: getting into space does generally involve sitting on top of a barely controlled explosion, and while it's probably one of those things that'll end up being safer than driving a car, we imagine that strapping yourself into a rocket is probably one of the most nerve-wracking things that a human can do.

Blue Origin is currently building its next vehicle, which will have a capsule on top that separates from the propulsion module in flight. The module will come to a powered landing, while the capsule coasts up to space (spending 3-5 minutes in microgravity) before using parachutes to land. Long term, this will be an orbital (not just suborbital) launch system, but nobody is talking about selling tickets for an orbit or two quite yet.

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4. Masten Space Science Systems

Masten is focusing primarily (let's just go ahead and say exclusively, at least for now) on cargo flights as opposed to passengers. Just over a week ago, their Xaero rocket (which is functionally complete) made a short-hop test flight, and CEO Joel Scotkin says that Masten is ready to start FAA testing, gradually increasing fuel tank size and target altitude, with flights to five or six kilometers happening in the "very near future.

To hit 20 kilometers, they'll need a bigger rocket, and parts are currently on order for what will be called "Xaero20." 100km+ suborbital flights should happen within a few quarters, and Masten has been secretly working on a suborbital lunar lander demonstration vehicle called Xeus, which you can see in the picture above. Xeus won't be going to the Moon, but it will be proving a testbed for the technologies that will one day take private industry to the lunar surface, asteroids, and beyond.

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5. Armadillo Aerospace

Armadillo has been working on a rocket called Stig B (after The Stig from Top Gear), which should be complete in under 70 days. Stig B is tall and skinny, and a "six pack" of them will likely be used to launch payloads (including people). Neil Milburn, a VP at Armadillo, said that they hope to make a first flight in May of this year, but that they're still working on a few different options for re-entry, including a supersonically-deployed balloon to slow down followed by steerable parachutes to make a landing somewhere near the launchpad.

Long term, Armadillo will be partnering with Space Adventures to develop a crewed vehicle codenamed "Hyperion." It may look something like the concept in the picture above, and it'll make vertical takeoffs and landings, taking two passengers into space. Hyperion will only seat two people, meaning that no pilots will be on board: it'll be under autonomous control the whole time, making for a "personal and intimate" experience. Yeah, use your imagination on that one.

Via NSRC

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When an airplane is in flight, it's continuously pushing a series waves of air out of the way in front of it, the same way that a boat moving through water is pushing out a bow wave. These waves of air travel at the speed of sound, and as long as the airplane is going slower than that, the waves can get out of the way of each other and people on the ground will just hear a regular airplane noise when the plane passes overhead.

Sonic booms happen when an aircraft starts going fast enough that the waves of air (pressure, really) that it's producing can't outrun the aircraft anymore, and they all stack up on each other, forming a single shockwave of sound at the front of the plane which can be decidedly unpleasant for anyone on the ground who gets smacked with it. And then they get smacked again by another, trailing shockwave, formed by the negative pressure at the rear of the aircraft. This is where that distinctive "double boom" comes from.

Misora (the honorific name for "sky" in Japanese) is a conceptual design for an entirely new sort of supersonic aircraft, from the Institute of Fluid Science at Tohoku University. As you can see, it's a biplane, a type of aircraft that went out of style back in the 1930s since two wings create tons of drag, generally making high speeds difficult. If you're clever, though, you can arrange those two wings to reflect shock waves back at each other, taking the positive pressure shockwave and the negative pressure shockwave and zeroing them both out. Without shockwaves, you get supersonic airspeeds with no booms at all.

As far as getting to supersonic speeds with two wings, a group from MIT and Stanford has come up with a design that uses smooth inner-wing surfaces combined with bumpy wing edges to reduce drag so much that it should be possible to develop a supersonic biplane that can travel at Mach 5 while simultaneously using half as much fuel as a conventional supersonic aircraft. Mach 5, for the record, is nearly 4,000 mph, which is fast enough to make the hop from LA to New York, or New York to London, in under an hour.

IFS Biplane (PDF), via LiveScience and Gizmodo

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Electromagnetically Levitated Space Launch Tube Must Be Tethered to Maintain Its Connection to Earth

Dr George Maise invented the Startram orbital launch system along with Dr James Powell, who is one of the inventors of superconducting maglev - for which he won the 2002 Franklin Medal in engineering. Startram is in essence a superconducting maglev launch system. _Gizmag

When we think about space elevators and other high altitute electromagnetic space launch methods, we are typically concerned about creating materials that are strong enough to support the weight of the massive launch apparatus. The Startram approach to cheap, high frequency space launch turns this thinking on its head, by utilising a form of electromagnetic levitation which requires the launch apparatus to be tethered to prevent it from whipping out into space.

All Images Courtesy of Gizmag

It's easy to levitate objects electromagnetically. If you push enough current through two conductors in opposite directions, the conductors will be subject to a force pushing them apart. The more current the greater the force. With the advent of superconducting cables being developed for superconducting power grids, it is now possible to construct cables which can carry hundreds of megamps of current. These amperages are sufficient to supply a levitating force of 4 tons per meter of startram guideway, even when the conductors are separated by 20km.

...One of the challenges of the Space Elevator concept is to engineer tethers that have breaking lengths (i.e. the length of tether can attain before it breaks under its own weight) of thousands of kilometers. Startram tethers, in contrast, needs tethers with breaking lengths of only tens of kilometers, which is well within the specifications of modern fibers. _Startram Technology

The Startram launch tubes are evacuated in order to reduce friction losses from air resistance during high velocity launch. According to the developers, the system can be built using existing materials and technologies.

The scope of the project is challenging. A launch system design for routine passenger flight into LEO should have rather low acceleration - perhaps about 3 g's maximum, which then requires 5 minutes of acceleration to reach LEO transfer velocities. In that period, the spacecraft will have traveled 1,000 miles (1,609 km). The maglev track must be 1,000 miles in length - similar in size to maglev train tracks being considered for cross-country transportation.

Like a train, the Startram track can follow the surface of the Earth for most of this length. Side forces associated with the curvature of the surface can be accommodated by the design, but not the drag and sonic shock waves of a craft traveling at hypersonic velocity at sea level - the spacecraft and launching track would be torn to shreds.

To avoid this, the Startram track must be contained inside a vacuum tube with vents to allow air compressed in front of the spacecraft to escape the tube. A vacuum equivalent to atmospheric conditions at an altitude of 75 km (about 0.01 Torr) should suffice for the efficient operation of the Startram launch system. Rapid pumping to achieve this pressure will be provided by a magnetohydrodynamic vacuum pump.

If the entire Startram tube is at sea level, on exiting the tube the spacecraft will suddenly be subjected to several hundred g's due to atmospheric drag - rather like hitting a brick wall. To reduce this effect to a tolerable acceleration, the end of the Startram vacuum tube must be elevated to an altitude of about 20 km (12 miles). At this height, the initial deceleration from atmospheric drag will be less than 3 g's, and will rapidly decrease as the spacecraft reaches higher altitudes.... how do we hold up the exit end of the Startram vacuum tube? Well, the tube already contains superconducting cable and rings. Powell and Maise realized that the tube could be magnetically levitated to this altitude. If we arrange that there is a superconducting cable on the ground carrying 200 million amperes, and a superconducting cable in the launch tube carrying 20 million amperes, at an altitude of 20 km there will be a levitating force of about 4 tons per meter of cable length - more than enough to levitate the launch tube. _Gizmag

Sandia National Laboratories has carried out a '"murder-squad" investigation of the Startram concept, whose purpose is to find any flaw in a proposed project. They gave Startram a clean bill of health. Estimates suggest that building a passenger-capable Startram would require 20 years and a construction budget (ignoring inflation and overoptimism) of about $60 billion.

Why take on such an enormous project? Simple - $50 per kilogram amortized launch costs. The total worldwide cost of developing and using rocket-based space travel is more than $500 billion. The Space Shuttle program cost about $170 billion. The International Space Station has cost about $150 billion to date. _Gizmag

If access to space can be made safe and routine, humans will suddenly find ways to make space travel and habitation safe, sustainable, and profitable. The challenge of surviving and prospering in space is the type of challenge which malaise-laden modern humans need, to revive a much needed sense of transcendence and open-ended overcoming.

Startram website

Why it is so important for people of the western world to find their way into space

More: Brian Wang is also beginning to look at this exciting space launch technology

Lighter than Air Craft for Orbital and Sub-Orbital Duty

The above vision for lighter than air-to-orbit, from JP Aerospace, has been circulating for 7 or 8 years now.

So far, the closest that JPAerospace has come to slipping the surly bonds of Earth, was with its Tandem balloon aircraft, which reached an altitude of 18 miles recently. Not so bad for a $30,000 project.

This is the JPAerospace Tandem launch, seen from multiple camera angles. The view from space is tacked on to the end of the video.

To become a reality, JPAerospace's "city in space" and lighter than air orbital launch, will need some big money backing. The US defense establishment is developing lighter than air observation platforms to be based at the edge of space, but there is no indication that the Pentagon wants to achieve orbit using lighter-than-air craft.

Spanish company Zero2Infinity is developing a lighter-than-air sub-orbital tourism concept, called inbloon. The goal is to take tourists to the edge of space inside a pressurised capsule, and allow them to stay there for almost 2 hours, appreciating the splendour of the planet below.

Zero2Infinity, based in Barcelona, Spain, hopes to start taking people up to near-space as early as 2013. Balloons cannot go as high as rockets, but in theory at least they should be far safer, since passengers won't be sitting on tonnes of explosives. Their environmental impact is also far lower than that of smoke-belching rockets.

López-Urdiales was inspired by his father, an atmospheric physicist who was involved in sending probes to Titan and Mars. "I've always seen him working, seen all the excitement of years of work going into a flight. That's what got me excited about space in general," he says. Then, in 2000, his father told him about how the Huygens probe that explored Titan was tested by dropping a prototype from a balloon around 40 kilometres up. "After our conversation, I thought if there's going to be space tourism, then let's try this way," he says.

There is no doubt that it is possible, because it has been done many times before. In the 1950s and 1960s, more than a dozen crewed balloons journeyed to near-space. In 1957, for instance, Joe Kittinger of the US air force ascended to a height of 29 kilometres in a capsule attached to a helium balloon. He enjoyed the ride so much that when ordered to descend, he replied: "Come and get me."

Zero2Infinity hopes to spread that joy to the civilian population. The company has carried out several test flights of uncrewed balloons, and earlier this year got the funding needed to carry out its first flight carrying people.

The plan is to use a massive helium "bloon", as the company likes to call it, to carry a pressurised capsule with space for two pilots and two passengers up to 34 kilometres above the Earth. You can book now - but at €110,000 per ticket, you'll need a little spare cash. _NewScientist

The video below juxtaposes the plans of Richard Branson's suborbital space tourism flights via rocket, beside the "inbloon" lighter than air suborbital tourism concept.

Bringing Down the Cost of Space Launch w/ Reusable Spacecraft

SpaceX Reusable Rocket (TechnologyReview)
Imagine how much it would cost to fly from San Francisco to London if the airlines had to destroy every airliner after each use. But that is the same basic logic that is used for space launch, where spacecraft typically do not survive the journey, requiring a new craft to be built for each trip. But what if you could re-use all parts of your craft, with rapid turnover between launches. Shouldn't that bring down the cost of space exploration and development?

NASA's space shuttle is the only orbital reusable launch vehicle that's flown to date, and it was retired this summer after falling far short of its original goals to launch frequently and inexpensively—the agency projected it would fly up to 50 missions per year at an operating cost of $10.5 million per flight. It turned out that the shuttles flew less than five times per year at an operating cost 20 times that.

SpaceX's approach is to convert the two stages of the Falcon 9 rocket into independent vehicles capable of making return landings at their launch site. The first stage, after separating from the rest of the rocket, would fire its engines to guide itself back to the launch site, extending a set of legs from its base to land vertically. The upper stage, outfitted with the heat shield that SpaceX developed for its Dragon spacecraft, which was designed to transport cargo and eventually crews to and from the space station, would reenter after deploying its payload in space. It would also use its engine for a powered vertical landing.

Musk is backing up his speech with development work. SpaceX has been quietly building an experimental vehicle called Grasshopper to test the vertical landing technology. Grasshopper is a Falcon 9 first stage outfitted with a single engine and landing legs to allow it to take off and land vertically.

...SpaceX is not the only company actively working on an orbital reusable launch vehicle. Blue Origin, the secretive aerospace company founded by Amazon.com CEO Jeff Bezos, has NASA funding to mature the design of a space vehicle that could be launched on existing expendable rockets, such as the Atlas V. Eventually, though, Blue Origin plans to replace the Atlas with its own reusable orbital launch vehicle, and is using part of the $22 million Commercial Crew Development award it received from NASA earlier this year to work on an engine for that rocket.

"We intend to fly our own Blue Origin reusable launch vehicles that will take [our] space vehicle up and make that system much more affordable," said Rob Meyerson, program manager at Blue Origin, at AIAA Space 2011. The company has not disclosed development schedules or other technical details about its planned vehicle. However, the support the company has from NASA, coupled with the financial backing provided by Bezos, makes the company's effort worth watching.

This is not the first time companies have shown an interest in building reusable launch vehicles. In the late 1990s, several companies, including Kistler Aerospace and Rotary Rocket Company, had ambitious plans for orbital reusable launch vehicles, but their projects never materialized.

What's the difference this time around? Charles Lurio, a space industry consultant and publisher of The Lurio Report newsletter, says current companies have made more progress than earlier firms, including building and flying hardware. "They have a fair shot at making it work," he says, "but nothing's guaranteed." _TechnologyReview

Originally published on Al Fin, the Next Level