In May 2008, two men climbed into a 40-ton submarine docked at an abandoned Copenhagen shipyard. One of the men had built the 58-foot-long sub in his spare time, and inside they chatted about the future. It involved rockets – big rockets.

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Follow Copenhagen Suborbitals' progress on ROCKET SHOP

Learn more about the new space race on OPEN SPACEAlthough it was the first meeting between Kristian von Bengtson and Peter Madsen, the submarine's creator, the duo emerged with a daring plan: to launch themselves into suborbital space using custom-built contraptions. And with that, Copenhagen Suborbitals was born.

Co-founders von Bengtson, an aerospace scientist and former NASA contractor, and Madsen, an entrepreneur and aerospace engineer, have a lot to be proud of since they founded their non-profit space program four years ago. In June 2011, for example, Copenhagen Suborbital's army of volunteers successfully built, launched and recovered a 31-foot-tall rocket – the largest "amateur" launcher ever built – with a crash-test dummy tucked inside.

That first prototype ended its flight two miles up, and the organization has yet to check off their ultimate goal: sending a person more than 60 miles above the Earth, a height widely considered the boundary of outer space. But now they are creating a bigger, better and badder space vehicle to get there.

"We have gone from having a crazy idea on a submarine to a smoothly run organization that builds rockets and spacecraft, and has experience with big launches," said von Bengtson, who also blogs about the project for Wired at Rocket Shop. "It feels like we have become a part of a new era in space. I wouldn't trade that for anything. Not for millions of dollars."

"I think we're watching something that may be bigger than we realize it is."

– Keith CowingBuilding rockets to launch people to the edge of space without a government's help isn't a new idea. Commercial companies like Virgin Galactic and XCOR Aerospace, for example, are each developing their own vehicles to grant customers several minutes of zero-gravity and an amazing view of the Earth from space.

Copenhagen Suborbitals, however, is a radical departure from such private spaceflight efforts. It has no board of directors to please, no shareholders to answer to and no strategic timelines to follow. Its members don't care about competition. Even the notion of selling a ride doesn't factor into von Bengtson and Madsen's vision.

"The actual flight is not really what drives us. It's the whole process of building, encountering problems and designing solutions," von Bengtson said. "The actual launch will be somewhat of a sad thing for everyone."

To date, Copenhagen Suborbitals has performed about 50 static rocket-engine tests, in which the machine is secured to the ground to study its performance. The two co-founders build and test their own hardware at the outfit's headquarters, which moved in August 2009 to the abandoned shipyard in downtown Copenhagen where Madsen's sub is docked. (Their former headquarters: a barge anchored in the Port of Copenhagen.)

The TM65 Tordenskjold – Copenhagen Suborbital's third liquid-propellant rocket engine – secured to a static test rig. The engine is expected to create about 200,000 horsepower of thrust. Photo: Copenhagen Suborbitals

It's a full-time effort for both men. Von Bengtson says he now supports himself primarily through speaking engagements, lectures and other appearances. The roughly $100,000 in Copenhagen Suborbital's annual operating budget trickles in from online donations and corporate sponsors.

"This covers the cameras, postage stamps, fuel, building maintenance, everything that makes the organization run," von Bengtson said. Copenhagen Suborbitals received another $200,000 to $400,000 worth of donated high-tech electronics, machining tools and other expensive devices from engineering firms, aerospace hardware makers and other companies.

"For a manned space program, these budgets are absolutely ridiculous," he said. "I bet it wouldn't cover the annual cost of coffee at NASA. But we make it work."

The team pays no salaries because it enlists the help of about 30 local volunteers. Their ranks include pyrotechnicians, space medicine experts, mechanical engineers, divers, electricians and a mix of other professions required to build, test and launch rockets at sea.

The organization needs ocean-faring experts because they can't launch from land – no European government will allow them to. "This is a major obstacle for any amateur, or anyone at all, to launch big rockets. Nobody wants it in their backyards," von Bengtson said. "Thankfully we found a unique way to get around this."

Maritime organizations ultimately worked with Copenhagen Suborbitals and approved launches from the Baltic Sea east of Denmark. In September 2010, the team attempted their first seaborne launch of a 31-foot-tall rocket-spacecraft assembly called HEAT 1X Tycho Brahe. A crash-test dummy was seated in the top of the spacecraft, which was capped by a transparent spherical dome.

They towed a floating launch pad into the middle of the Baltic Sea, steadied the rig with the 40-ton submarine, assembled and fueled the rocket, and then pulled the trigger. But nothing happened. The team later discovered a power supply to a hair-dryer – a surprisingly cost-effective means to thaw icy fuel lines – but not the hair dryer component itself, had stopped working. The failure blocked liquid fuel from reaching the engine's combustion chamber.

Copenhagen Suborbitals spent more than 9 months refining Tycho Brahe's design (including ditching the hair dryer for an industrial-strength heater) and went for another launch on June 3, 2011. This time their rocket ascended nearly 2 miles into the sky before controllers cut the engines (launch starts at minute 3:52 in the video below). A parachute partially failed to deploy, but the team managed to recover their spacecraft and its deadweight passenger.

"That was a big moment for us. We had to prove to ourselves that we were capable of launching a rocket this complex and see if this project was actually possible," von Bengtson said. "It was a huge boost."

The Danish team has since kept itself busy with designing a taller, girthier rocket body, a more powerful liquid rocket engine and a roomier, better-equipped spacecraft named "Beautiful Betty," which is modeled after an Apollo-era capsule.

To get the job done, they're using common yet effective materials like cork, soda-carbonating cartridges and life vest inflation tubes. Their bootstrapped approach has also led them to crowd-source designs of some spacecraft elements – including the hatch, control panel wiring and inflatable landing bag design. They have even scanned and posted idea sketchbooks and open-sourced their mission control software.

So far, so good.

"It's a kind of crazy approach, but what they're doing isn't anything that requires magic. It's pretty low-tech and low-performance, but their concepts are workable," said Ben Brockert, a mechanical engineer at Armadillo Aerospace who has eagerly followed Copenhagen Suborbital's progress for years.

"They're certainly not the laughing stock of the community," he said. "That they build actual, functioning hardware lends them a lot of credibility."

Brockert said he does wonder if, after three, five or 10 years, Copenhagen Suborbitals can cling to its motivation. "Anyone who starts out doing ambitious things like this finds out everything takes way longer than you expect," he said. "They might get tired in a few more years."

Keith Cowing, editor of NASAWatch.com, said Copenhagen Suborbitals has yet to convince anyone that they've built something safe to fly in. Spine-severing vibration, blackout-inducing acceleration and catastrophic hardware failures could each doom a would-be passenger.

"But the fact that I'm not making fun of this and worrying about detailed technical aspects is fascinating. We don't giggle at it anymore," said Cowing, a former biologist who did payload integration for NASA and has completed suborbital scientist astronaut training.

"In the past few years, it's no longer considered lunacy to try and build a rocket ship that you or someone could get into and take you to edge of space," he said. "I think we're watching something that may be bigger than we realize it is. Copenhagen Suborbitals is an extreme example."

Peter Madsen applies a finishing polish to a rocket engine piece. Photo: Copenhagen Suborbitals Thomas Pedersen

Von Bengtson acknowledged the danger of stepping into a spacecraft built outside the realm of extreme quality control seen at NASA-contracted aerospace firms. But having lives on the line, he noted, is exactly what keeps him, Madsen and the volunteers focused and motivated.

"This is dangerous, but life is dangerous, too. I was riding my bike to work today and was almost hit by a car," von Bengtson said. "I believe you can be daring without being foolish. We will know every single piece of this rocket and spacecraft when it's done."

Karla von Bengtson, an animated film director, Kristian's wife and the mother of their two children (ages 4 and 6), said Kristian is a wonderful father and husband – despite attending a never-ending stream of late-night meetings with his volunteers to accommodate their day jobs.

"I really don't care what he does for a living as long as he's very passionate about it. I didn't marry Kristian to be with someone who never does anything about his passions," Karla said. "Although I'm sure a lot of women would hate his career choice."

One big sacrifice for the von Bengtson family each year is the summer. That's when it's best to launch rockets at sea, Karla said, but it always falls on her birthday and summer vacation time. "So, for the last four years, I haven't had my birthday," Karla said. "I don't like rocket season."

Karla said she's very cognizant of the danger her husband faces in the business of building and launching rockets. She's most concerned, however, about his day-to-day well-being. "I sometimes worry that his effort could grow too big for him. He can't just say 'I'm the boss' and buy people he needs to get things done," Karla said. "He has to build everything himself with the help of volunteers."

Von Bengtson is loathe to peg even an approximate year for the pinnacle of Copenhagen Suborbitals' existence. "Maybe between five to 10 years from now," he said. "It's impossible to know."

But if and when Copenhagen Suborbitals is ready to put a human inside its contraption, who goes first?

"Peter will. I'll let him test the spacecraft and then I'm going to follow in his footsteps," von Bengtson said.

That decision was made at the beginning of their adventure four years ago, below the water in the hull of Madsen's do-it-yourself submarine.

Copenhagen Suborbitals co-founders Kristian von Bengtson (left) and Peter Madsen (right). Photo: Bo Tornvig

Video: The June 3, 2011 launch of HEAT 1X Tycho Brahe. Launch video starts at 3:52. (frumperino/YouTube)