Space Vehicles Go Green – Reusable Launch Vehicle Concepts

In launch vehicles these days, it’s all about reusability. SpaceX recently tried to reignite its first stage booster, which is the initial step toward landing it vertically on the ground. If this first stage is landed successfully, it can be used again and again. DARPA is calling for proposals for a “reusable hypersonic vehicle with costs, operation and reliability similar to traditional aircraft.” Companies will propose their ideas on Monday October 7th.  Across the Atlantic, Reaction Engines is developing the SABRE engine, a radical engine for the Skylon spaceplane. Each design has the same intention, lowering the cost of access to space by reusing vehicles over and over again.

SpaceX has taken the most traditional approach to launch vehicles, using a vertical launch system and powerful rockets to get payloads into orbit. However, this system has not been reusable in the past. To add reusability to their system, SpaceX intends to have the massive first stage of the rocket land itself on the launch pad. The company is currently exploring the vertical landing technique through the Grasshopper research project, which completed a 325 meter leap test on June 14. While SpaceX’s system is not fully reusable, they are working toward that goal.

On the opposite extreme, Reaction Engines in the U.K. is developing a fully reusable spaceplane known as Skylon. Unlike SpaceX, which uses multiple stages of rockets to get into space (dropping used ones, such as the first stage, along the way), Reaction Engines wants their spaceplane to get into orbit using a single stage. To achieve this lofty goal, Reaction Engines is developing SABRE (see picture), a revolutionary rocket engine that uses atmospheric air as rocket oxidizer for a portion of the trip. Reaction Engines explains that SABRE sucks in atmospheric air through an inlet and then cools it to nearly liquid, basically generating its own oxidizer. However, once the Skylon exceeds Mach 5, the engine morphs into a typical rocket engine, using its own oxidizer stored onboard. This design allows Skylon to carry less liquid oxygen than a typical launch vehicle, saving space and weight for other essentials. With this radical engine, Skylon could be the start of a whole new family of launch vehicles.

In contrast, DARPA’s XS-1 spaceplane design concept seeks to be a melding of the traditional and radical. The radical part of the design is a suborbital spaceplane that can launch just like an aircraft, from the ground. This distinction is important because SpaceShipOne, a successful suborbital spaceplane, launched from a flying “mothership” airplane in 2004. The XS-1 concept, according to the proposer’s day announcement, is a reusable suborbital space plane with a (more traditional) secondary stage that would launch payloads into their required orbit. DARPA’s goal is ten flights in ten days, which would be a radical departure from current launch timeframes.

Although the goal of reusability is shared across these programs, the designs are completely different. They each also have their own timeframe. SpaceX is already conducting preliminary tests. The other two space planes are still in the concept phase. While parts of SABRE, such as the precooler system, have been tested, the Skylon system is years from launching. The XS-1 design is still flexible, so there’s no telling when it may be ready to fly. This flexibility shows how DARPA recognizes that they are many different ways to make reusable launch vehicles. The plethora of designs in development right now shows that reusable space vehicles are likely to be the next way to access space.

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XCOR Aerospace Borrows “Several Hundred Years of Experience” for its Piston Driven Rocket Pumps

On Monday, the partnership of XCOR Aerospace and the United Launch Alliance announced that they had adapted an old technology, the piston, into a high technology pump for liquid hydrogen rocket fuel. “…We have successfully operated our liquid hydrogen pump at design flow rate and pressure conditions,” said XCOR CEO Jeff Greason in a recent press release. The liquid hydrogen pump tested earlier this week is just one pump in a new family of piston driven fuel pumps. Flight Global reports that the company has already tested a rocket engine setup with their piston pumps, using the system to fire liquid oxygen and kerosene in March of this year.

So, why use an old automotive technology in the relatively new field of rocket development? Pistons provide a different way to drive fuel and oxidizer into the combustion chamber, where the chemical reaction that produces thrust occurs. Other current rocket technologies use a gas generator system (pump fed) or high pressure tanks (pressure fed) to drive the fuel and oxidizer into the combustion chamber (see below). The pump fed rocket relies upon reacting some of the fuel and oxidizer in a high temperature turbine, which generates the power for the pump system. Pressure-fed systems are simpler, using a high pressure gas (usually something nonreactive) to push the fuel and oxidizer into the combustion chamber. Both the pump fed and pressure-fed systems are fairly heavy, due to the gas generator and the large pressurization tanks. All three technologies have benefits and deficits, but XCOR argues that the piston pumped engines will cost less to manufacture and be easier to operate.

All three engine designs are competing to maximize thrust and reliability while keeping the mass of the system low, often leveraging other technologies to reach that goal. XCOR’s piston engine, the company explains, utilizes automotive technologies and a patented thermodynamic cycle to maintain a high specific impulse (a measure of thrust efficiency) and an easy start-stop feature. Like automobiles, XCOR’s pumps can run at a higher rpm than the original design, so the piston pump can be fitted to a larger rocket and pump more fuel if necessary. These pumps are a way toward an adaptable and reliable system through tweaking proven automobile technologies. Likewise, the pump fed rocket borrows high temperature, low mass materials from other industries, like aircraft engine manufacturing, to maximize the efficiency of the turbine and keep the mass low. Even the pressure-fed system draws from another industry, the materials industry, to create lighter tanks of new and exotic materials (such as carbon fibers).

Other non-aerospace technologies are also entering the aerospace sector. Designers are using enhanced video game graphics to simulate engineering tasks. Leveraging the developments of other industries is a great way for rocket propulsion and aerospace to progress with tight budgets. By utilizing automotive developments, XCOR flew through its first small piston rocket pump development, “taking fewer than four weeks from initial design to demonstration,” according to the site. Borrowing some concepts from other industries can help other companies do the same.

ScramSpace Grapples with Scramjet Testing Challenges

Yesterday, an Atlas V and an Antares rocket both roared off of the United States eastern coast and into space. However, in a remote area of Norway, another rocket launch didn’t go as planned. ScramSpace, a scramjet developed by researchers at the University of Queensland, disappeared over the Atlantic Ocean without sending back the hoped-for data. Scientists were left to clean up the two rocket sections that launched ScramSpace skyward and head home.

What’s the difference? How can complex orbital missions like the Atlas V and Antares be successful when a scramjet flight so easily goes awry? Part of the difference is the physics, which makes scramjets harder to test. While both rockets and scramjets are means of achieving high speeds, they differ in design. Scramjets squeeze high speed (greater than Mach 5) air into a small tube, compressing and heating it. Then a fuel is injected into the airstream. They only work above Mach 5. In contrast, rockets supply their own fuel and oxidizer (air is an example of an oxidizer, oxygen is another), mixing them to cause the explosive reaction that gets them moving. The physics of rockets is fairly well understood after years of launch. Scramjets have not had the luxury of so many tests, mainly because testing scramjets is difficult.

First of all, the testing setup for scramjets is tricky. Unlike rockets, which can be ignited at any speed, scramjets only work when they are already traveling at Mach 5 or greater. Since no research planes currently achieve these speeds, rockets are required. ScramSpace, the University of Queensland explains, uses a two-stage rocket to send the scramjet into space. Then the test is completed as the scramjet accelerates toward Earth (see graphic at top). Other projects, like the X-43 and X-51 projects in the US, launch the scramjet from a B-52 bomber, accelerate it with a rocket and then perform the experiment, according to NASA. These tests are not simple or easy to do.

Plus, once you get to Mach 5, the conditions are nasty. At high speed, aerodynamic heating causes the scramjet to experience extreme temperatures. This means that scramjets require high temperature alloys to simply maintain their structural integrity. The physics also get complicated at hypersonic (above Mach 5) speeds. Shockwaves bounce around inside the scramjet tube and must be “swallowed” correctly in order to achieve maximum thrust. In an ABC Catalyst special, a ScramSpace engineer explains that the air must also rush into the inlet at the right angle. Extensive ground tests help scientists determine these conditions, but they don’t depict how the vehicle will react in actual flight.

The test setup also leaves very little room for error. In the same ABC short video, a ScramSpace engineer explains how vital proper controls are to the experiment, demonstrating how reaction thrusters are used to properly align the craft in space. If improperly aligned, the ScramSpace vehicle would not work correctly. U.S. projects have also had difficulties controlling scramjets at high speeds. An X-51 WaveRider scramjet failed to ignite when one tiny fin (of four) became loose before the ignition, according to Zach Rosenburg. Controlling the vehicles is difficult and the conditions at Mach 5 and above leave little room for error.

Despite all these difficulties, scramjets have accomplished some amazing test flights. The third test of the X-43 still holds the world record for an air breathing engine (as opposed to a rocket engine, which carries its own “air” or oxidizer). According to NASA, it achieved a speed of Mach 9.6, and, theoretically, scramjets can go even faster, reaching Mach 14 or 15. That’s almost fast enough to reach space! The last test of the X-51 Waverider flew successfully for over 6 minutes, according to Space Ref. This was huge accomplishment for a test period that is typically 5-15 seconds.

Overcoming the difficulties of scramjet flight is difficult, not impossible. Perfecting scramjets is challenge worth taking on. Since scramjets use atmospheric air as the oxidizer, instead of carrying big oxygen tanks as rockets often do, they offer great weight savings over rockets. Yet, funding for scramjets is often limited. The ScramSpace team is heading back the University of Queensland, according to a recent report, not to begin building again, but to be disbanded. Once perfected, scramjets can become the transportation of the future, streaking through the skies at speeds above Mach 10, but they face many physical and budgetary challenges in the near future.

NASA Has a History of Crashing Helicopters for Science

In a video reminiscent of Discovery Channel’s Mythbusters, NASA dropped a 45 ft long Marine CH-46E helicopter fuselage into the dusty ground at NASA’s Langley Research Center. NASA reports that the helicopter, having plummeted from 30 feet in the air, smashed into the ground at 30 mph. This was a simulation of a survivable crash, but the 15 crash-test dummies locked inside did not have a smooth ride. At the conclusion of the video posted by NASA, one almost expects to hear Mythbuster Adam Savage giggle.

Perhaps smashing things does make NASA engineers giggle; they have a history of crashing helicopters and other experimental aerial vehicles. In 2009, the U.S. Army donated an MD-500 helicopter to NASA, according to a NASA press release. What did NASA do with it? They crashed it (“for science”). The initial test had a “deployable energy absorber,” a Kevlar honeycomb design originally intended to cushion space capsules. Miraculously, the helicopter survived the first test relatively intact, thanks to the new technology.

Four months later, NASA explained that it had dropped the helicopter a second time. This time, however, the MD-500 had no honeycomb cushion. As a result, the helicopter was too damaged for further testing. Engineers had recorded over three times the “g” forces compared to the previous test with the cushion. The picture below shows the windscreen shattered and the skids bent. It was destructive testing, indeed.

However, unlike Mythbusters, NASA conducts the tests for more than the wanton destruction and cool video footage. In the 2009 and 2010 tests, NASA was able to demonstrate that the honeycomb cushion designed for space capsules could also increase the survivability of a helicopter crash. It worked so well that they were able to simulate another crash for comparison.

Last week’s crash test of the much larger CH-46E helicopter also provided useful crash data. Unlike the 2009-10 tests, this time NASA crashed the unmodified helicopter first. Although the test already had scientific use as a basis for which to compare a future test of a composite airframe, additional experiments abounded. The Navy, Army and FAA all contributed different crash test dummies. CONAX Florida Corporation DBA Cobham Life Support tested a restraint system in the cockpit. Unlike Mythbusters, NASA now has 350 different instrumentation points to analyze, as well as high speed camera data.

Destructive testing, like NASA’s recent helicopter crash, is not only fun and entertaining, but extremely useful. New technologies, like the honeycomb cushion, can be tested and vetted for future use. The cost, however, is high. Not everyone has the money available to conduct these necessary tests. With NASA facing flat budgets for the next few years, we wonder ‘who will crash our helicopters for us in the future?’

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Repurposing Spacecraft not a Novel Idea, but a Cost-Effective One

On August 15th, NASA officially issued a call for help, in the form of scientific white papers, in hopes of repurposing the crippled Kepler spacecraft. The telescope, which had led the charge in finding exoplanets, planets orbiting distant stars, has been unable to function due to issues with two of its four reaction wheels. These wheels, which, NASA explains, are used to point to distant galaxies, are vital to Kepler’s scientific mission, studying distant stars for the changes in light intensity that would signal a planet passing between Kepler and the star. Without the ability to point correctly, the spacecraft’s main mission is compromised. Rather than letting it drift in space, NASA is trying to repurpose the satellite to save money, a strategy that the space agency has used in years past.

NASA had success with repurposing two of the THEMIS spacecraft in 2010, according to an old press release. Originally intended to study the magnetosphere, the little understood magnetic field that surrounds the Earth, two THEMIS spacecraft were diverted toward the moon after finishing their original mission. Once in lunar orbit, the spacecraft began a new mission, ARTEMIS, studying the effect of solar wind on the moon’s surface. By simply sending the fueled spacecraft to another location, NASA scientists were able to get valuable new data, without spending much extra money.

“Using two repurposed satellites for the ARTEMIS mission highlights NASA’s efficient use of the nation’s space assets,” said Dick Fisher, director of the Heliophysics Division in NASA’s Science Mission Directorate at the agency’s headquarters in Washington. With its budget shrinking, NASA is doing all that it can to avoid the high cost of building and launching spacecraft.

NASA is not alone in trying to save money through repurposing satellites. John Keller reported in late January that the U.S. Defense Advanced Research Projects Agency, aka DARPA, is also looking to repurpose spacecarft, by recycling components from non-operational satellites. Defunct spacecraft often have still useful antennae and sensors. Building and launching these components is costly, in terms of both manufacturing and fuel. By recycling parts already up there, DARPA can lower the cost of a new satellite.

Using new ideas and clever innovations to repurpose or recycle spacecraft is both cost effective and a strong move toward sustainability. The junkyard of decommissioned satellites can instead become a useful tool shop for those with innovative ideas.

With Sequestration Grounding Blue Angels and Thunderbirds, Civilian Jet Teams Steal the (Air) Show

After years of performing at SeaFair in Seattle, the airbox was conspicuously absent of the thundering presence of the Navy’s Blue Angels. Instead, spectators were treated to a red, white and blue spectacle by a civilian jet team, the Patriots. This has become a common sight since the Navy’s Blue Angels and the USAF’s Thunderbirds stopped performing at air shows due to sequestration budget cuts. With the military teams grounded, civilian jet teams, like the Patriots and Black Diamonds, have had the opportunity to wow crowds with their unusual planes and comparable maneuvers.

Although the Patriot’s Aero-Vodochody L-39C’s can’t match the supersonic speed of the Blue Angel’s F-18’s or the Thunderbirds F-16’s, the planes unique characteristics make for a great show. The Patriot’s website details an unusual maneuver known as the Tail Slide, where the L-39 stalls and fall back toward the earth. You won’t see that at a Blue Angels or Thunderbirds show. Additionally, the slower speed of the L-39’s makes it possible for the pilots to turn around using less space, so the planes return to the show area more quickly. The L-39’s may lack the bone-rattling power of the supersonic American fighter jets, but they still have entertaining maneuvers to offer expectant crowds.

In fact, the Patriots and other civilian jet teams can duplicate many of the maneuvers expected by Blue Angels and Thunderbirds followers. Of the seven maneuvers listed on the Thunderbirds site, the Patriots show replicates six of them with accuracy. The L-39 formation completes the diamond opener and loop in their show sequence. Both shows feature an opposing knife edge maneuver and calypso, difficult two-plane formations where the planes fly close together and inverted. There are a few moves that the civilian teams can’t copy, due to their planes’ capabilities, but the non-military teams have invented some of their own formations as well. You would never see the Blue Angels draw a heart with an arrow through it, but the Patriots do it at most shows.

Another different aspect of civilian jet teams is that they have a wide variety of aircraft available for purchase, allowing them to maintain multiple types of aircraft. Although the Blue Angels showcase F-18’s and the “Fat Albert” C-130 Hercules, the Black Diamond civilian team has three different aircraft – L-39’s, Mig-17’s and a CT-33 listed on their page. An abundance of aircraft types allows the Black Diamond team to create unique maneuvers, such as their “Make a Wish Roll,” where a Mig 17 barrel rolls around the diamond formation. Many air show buffs often attend in order to see different planes, and the Black Diamond civilian team delivers more planes per show than either military jet team.

While your eardrums may not tremble when the -L39’s enter the airspace, civilian jet teams are thrilling spectators at venues across the country. As one of few alternatives while the military jet teams are grounded, the civilian teams like the Patriots have been running a full schedule of shows this year. If the Blue Angels and Thunderbirds get off the ground anytime soon, they may find new competition for airshow performances.

Rocket Hobbyists Show Off Unique Designs in Bonneville

Although the multi-million dollar rockets roaring off the launchpad often have similar shapes and designs, you’re bound to find some unique rocket designs at the Utah Rocket Club (UROC) Hellfire 18 event at the Bonneville Salt Flats. Unbound by needs of payload capacity and insertion points, model rocket designs probe the limits of design, often adding their own signature style.

Some rockets are designed simply to have a unique look. One was modeled after a chess piece. Another resembled a supersonic plane, built entirely from aluminum. One hobbyist showed off his glistening blue carbon fiber lined body tube, christened the Mockingjay after the iconic symbol of The Hunger Games. When pressed about the use of carbon fiber, he simply replied that he thought it looked the best.

However, not everyone cares about style; one hobbyist found practical reasons to modify his design. At a prior launch, one of his rockets plunged through the front window of a car due to a parachute deployment failure. Determined to make his rockets’ landings safer, this enterprising designer made two rockets of foam and balsa wood. Using a FUNNOODLE ® foam pool noodle as the body tube and nose cone and fins made of sturdy balsa, these rockets don’t need a successful parachute deployment anymore. When they smack the concrete-hard surface of the Bonneville Salt Flats, they simply bounce, ready for another launch as soon as the motor is replaced.

The diversity of designs is astonishing compared to large-scale rocket designs, even if the success rate isn’t as high. One can only hope that the commercial launch vehicles created by the likes of SpaceX, Blue Origin and Orbital Sciences will someday have as much diversity as one crate of rockets sitting in the blistering Utah sun. Who wouldn’t want to launch into orbit on a rocket shaped like a chess piece?

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