The race to the Moon is on once again, but unlike the space race in the 1960s this time it is fuelled not by national prestige but by cold, hard cash.
When President Barack Obama called a halt to US plans to return to the Moon, it paved the way for private enterprises to fill the void.
The US Constellation programme was launched in 2004 by then-president George W Bush after the Columbia space shuttle mission ended in disaster with the death of all seven crew members in 2003.
Since then Nasa has faced growing pressure to cut its budget as the US government's debt soared and the US buckled under the deepest economic crisis since the Great Depression of the 1930s. The agency has also seen dwindling political support, with its White House and congressional paymasters reluctant to fund the type of expensive manned space exploration that saw the agency put 12 men on the Moon.
Nasa is estimated to have already spent a little over $9bn on Constellation, including $3.5bn on the component Ares 1 programme and $3.7bn on the Orion programme.
With that announcement the attention has shifted to a competition launched two years earlier by the X Prize Foundation, for a private company to put a robot on the Moon. The Google Lunar X Prize has a $30m prize fund, $20m of which goes to the winning entry. To claim the prize you have to send a robot to the Moon and have it travel 500m while sending video, images and data.
In total there are 29 teams vying for the award, encompassing 17 nations and four continents. In prime position at the moment are a US collaboration between Astrobotics Technologies and Carnegie Mellon University. Their robot, the Red Rover – named after CEO and chief technical officer Dr William 'Red' Whittaker, a leading world expert on building robots with the intelligence to select their own path through unstructured environments – already has a launch vehicle booked. Astrobotics have a berth on a launch from commercial space carrier SpaceX on its Falcon 9 launcher for December 2013.
'In the very beginning it started out with me and David Gump,' John Thornton, Astrobotic's chief engineer and senior research engineer at Carnegie Mellon University's Robotics Institute, says. 'We started building a team to imagine what a Moon rover would look like and how we might get there.'
Eight months into the project, the team considered using a mothballed Phoenix II launch vehicle for the Moon shot. However, that vehicle presented several challenges primarily around the low payload ability. 'You can't get a whole lot of mass up into orbit and then up towards the Moon in that vehicle,' Thornton says. 'We had to use a multi-stage space craft. There was a trans-lunar injection stage, that means the period going from the Earth to the Moon, and then we had a braking stage and a final stage, so we had to use several stages to try to optimise the efficiency. We also had to do big weight-saving programmes and make cuts to try and get the mass to work. At one point we decided it was just going to take too much, it didn't quite make enough sense and we really didn't have much of a plan to how it would last in the longer term.'
At that point the focus switched back to the Falcon 9. 'What we quickly realised with the Falcon 9 is that we could be very comfortable with mass margins. It also gives us the capability to bring up to 100kg of payload to the Moon's surface. This all means that we were then able to create a business around bringing payload to the surface of the Moon.'
The Falcon 9 upper stage will sling the lander with the Rover on a four-day cruise to the Moon. It will then orbit the Moon to align for landing. The spacecraft will land softly, precisely and safely using technologies pioneered by Carnegie Mellon University for guiding autonomous cars. The Rover will explore for three months, operate continuously during the lunar days, and hibernate through the lunar nights.
The Rover will only form part of the payload of the mission; other space is being sold to companies such as Nasa. The mission has 220lb of payload capacity available for customers and the company is discussing payload terms with space agencies, corporations and universities.
Hot and cold
One of the major obstacles for the Rover will be the huge variation in temperature between the scorching lunar day and frigid night. It is such an extreme environment; the Sun is out for 14 days where the temperature is above boiling point for liquid nitrogen, and then down for 14 days where it is about -180°C, classified as cryogenically cold. The robot beats the heat by keeping a cool side aimed away from the Sun to radiate heat off to the black sky. It travels toward or away from the Sun without turning its radiator into the light. Only the solar cells on the hot side ever face the Sun. The robot can travel north and south by tacking like a sailboat.
'The Rover is around 80kg and the design starts with the thermal case to deal with the extremes of temperatures,' Thornton says. 'When you're designing a Rover for the equatorial locations on the Moon you have to start with a thermal design. That is why the Rover has a large white radiator on one side and a fairly large solar array on the other.
'Any good design has to start with that; when you factor in how much power has to come into your solar array and then how much has to go back out into space to keep the robot cool, that basically sizes your robot. The robot will take about 120 watts of power on average and it will take the size of robot that we have now to make that happen.'
Another innovation is a lunar-specific drive train. Unlike Mars rovers that have motors in the hub of each wheel, the Astrobotic lunar rover tucks two motors inside the body of the robot where they are safeguarded both from heat and the abrasive lunar dust. Each motor drives one side of the robot's wheels using a chain drive, like a bicycle. The chain drive mechanism has been tested in a Carnegie Mellon vacuum chamber to ensure that it does not experience 'cold welding' – a process where materials sometimes merge or weld to each other when touching in a hard vacuum.
'There are two reasons that we wanted to keep the motors away from the wheels. The first is due to the regolith [Moon dirt] being extremely abrasive and sharp and if that gets into the gears it can damage them,' Thornton explains. 'Also, because if we are able to put the motor at the shoulder of the robot we could do a final drive with chains, keeping the motor inside the chassis allowing us to regulate the temperature.'
Key to the design are tailored composite structures made from carbon fibre tape and resin. Many aerospace designs use composite materials to achieve high strength at low weight; composite parts being shaped for the lunar machine have the added ability to transmit heat from the hot to the cold side with more efficiency than copper or other metals. The team has fabricated several of the most complicated and high-stress components and subjected them to both thermal and stress tests. The thermal tests instrumented keys pieces with thermocouples to measure the heat flow from hot end to cold end. The flexure test documented how much pressure a piece can withstand before buckling.
Thornton's experience from his work on the Boeing 787 Dreamliner formed the basis of the Rover's composite structure. 'The Dreamliner is where it all started,' Thornton says. 'Some of it came from an unusual programme at Carnegie Mellon called Buggy – three-wheeled race cars that look like torpedoes. The idea of this was to put a girl inside of it, push it up a hill, and then push her down a hill. It's a five person relay team and, basically, the fastest time wins.
'I was head mechanic on a team for three years doing that and ended up building a lot of composites in structures. That's what got me the Boeing job, which escalated and started the composites programme at Carnegie Mellon that then got composites into this space programme.'
Landing on the Moon
There are a few potential landing sites but one tantalising possibility is in the Sea of Tranquillity, near the Apollo landing site. 'That would be really cool because we could end up landing next to Apollo 11 or one of the other Apollos,' Thornton says. 'If you think about it, half the people on this planet have never seen something land on the Moon. We could create a whole new Apollo moment for a brand new generation.'
The other potential landing site is what is known as a skylight, although some people just call them pits. These are places where there is a ceiling collapse inside a tunnel, or a lava tube, on the Moon leaving a pit around 30-60m across and almost 30m deep. 'These are really interesting places because if there is a cave to be found in these pits it would be a great place to go in and get away from micro-meteorites, from radiation and be able to regulate your temperature,' Thornton explains. 'When you're looking at settling on the Moon for more than a few days this could be a prime position to investigate.'
Once the lander is on the Moon's surface, the Rover will deploy via an ingenious ramp mechanism. The Rover will be sitting atop the lander, breakable bolts pop, two ramps deploy either side of the Lander and then the Rover will choose the safest way, north or south, to start its journey. Control is taken by the US-based ground station, probably in Pittsburgh. This control will consist of a computer over the Internet that is in communication with the Rover via satellite.
'The computing of these machines has really grown since the vehicles used in the Apollo missions,' Thornton says. 'They had no more computer power than your average pocket calculator and now we have orders of magnitude better computers available than that.
'The technical challenges are not the same as they were in the Apollo days. Then the technology was all that mattered because you had to build all sorts of [new] instruments. What is interesting is that all of those pieces, parts and even the software already exist and our challenge is just to put them together in a smart way to use them to land on the surface of the Moon. One of the most challenging parts is the integration of the technology.
When Eagle landed on the Moon on 20 July 1969, America officially won the race to the Moon. If Red Rover achieves that feat two years hence, the price will be a bit more rewarding. Aside from the $20m Google Lunar X Prize, the team will have assured a huge slice of future Moon payload business. *