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Sunday 1 May 2016

SpaceX's Dragon 2 - opening up the solar system?

Elon Musk, founder of SpaceX, announced recently that he plans to launch aprivate (unmanned) mission to Mars. The core of the mission will be SpaceX's Dragon Two capsule, an upgrade on the Dragon One model currently flying missions to and from the ISS. Dragon Two - which is currently undergoing testing - will be capable of ferrying up to seven crew to ISS.
That's cool enough, but the design isn't limited to ISS flights: It's designed to land on any world with a solid or liquid surface.

Above: A mock up of dragon two, on display at a SpaceX facility.

In conjunction with SpaceX's planned Falcon Heavy rocket it could put four tonnes of equipment on Mars, land on the Moon, or even put a payload onto one of the Moons of Jupiter.

Above: SpaceX's recent landing of it's Falcon re-usable booster.

Musk, it seems, isn’t content with less than the whole inner solar system - and he aims to make Dragon Two the standard interplanetary delivery vehicle.

Above: Dragon Two tests it's propulsive landing engines.

In September we'll find out more details of the planned Mars mission. The internet is already alight with speculation on it, so instead I thought I’d try looking at some of the ideas being raised for using Dragon Two to explore the rest of the solar system.

First, some caveats: Putting humans onto another world -possible excepting the Moon or a small asteroid - with just a Dragon Two isn't really an option because many months in a capsule the size of a big shower cubicle isn't great for astronaut psychology.
Plus Dragon 2 is designed to land on these worlds, not take off again... which is also bad for astronaut psychology*.

The Moon:

Above: An Apollo astronaut . Will humans return to the Moon any time soon?

If you can do a rocket powered landing on the Martian surface you can certainly manage one on the Moon. Dragon Two could land large loads of sensors and instrumentation, heavy duty  rovers, multiple small rover, supplies and equipment for a lunar base, or robots to build one. There's a lot still that we don't understand about the Moon, and scientists are very eager to get exploring:

  • ISRU (In-Situ Resource Utilisation): This is one of the big enabling technologies we'll need to develop if dreams, like Elon Musk’s, of expanding into the solar system are ever to be realised. Experiments with using lunar resources for construction and science are also high on peoples list: It would take far less energy to build and launch a vessel from the Moon than it does from Earth.

Above: The strange 'Ina' formation, which seems to have erupted in the last million years.

Although Musk himself is focussed on Mars, a lot of folks who'd like to begin exploring the Moon again are paying close attention to the Dragon two.

Near Earth asteroid:

Above: An artists impression of an asteroid being transformed by 3D prinitng. Courtesy of NASA.

Dropping a major payload onto a near Earth asteroid with Dragon two would be even easier than landing it on the Moon. With missions like NEAR, Philae, and Hayabusa, we've learned a lot about landing on such teeny objects, and there’s lots of reasons to do so: The possibility of extracting resources from them, studying their geology (which would tell us about how the solar system formed), and even sending a manned expedition are all on the cards – not to mention learning how to move a dangerous one.

But one possibility being bought up  is that we could use a Dragon two to kidnap one: It's been known for a while that small space rock s - only a meter or less wide - can and do get caught in Earth's gravitational field, becoming 'quasi moons'. A heavily modified Dragon two capsule could track one of the smaller ones down and bring it back to Earth intact. Only tiny amounts of guaranteed uncontaminated  asteroid material have been returned to earth to face the full battery of scientific investigation.


Above: Marathon valley, Mars.

You could write a book on the science that scientist want to do on Mars - and plenty of people have. Amongst the most exciting things a Dragon two could land on the Martian surface are :
  • Landing equipment and supplies for a manned mission: Any future 'boots on Mars' effort will have to include a long stay on the Martian surface - partly to make the time and money well spent, and partly because orbital mechanics dictate that there are better an d worse times to make the crossing. So dropping supplies onto the surface with Dragon 2, ahead of the main event, would make the whole thing more do-able.

  • An unmanned sample return mission: The large payload mass that Dragon 2 could put on the Martian surface means it might be able to deliver the mission that, in many space geek’s eyes, is the next best thing to a manned landing: A mission where carefully selected Martian rock and/or soil is collected by a rover, returned to the capsule, and then launched back to Earth. It's a huge technical challenge, but having a proven system that can land enough equipment on the Martian surface would clear the first big hurdle

  • Send a greenhouse: Dreams of terraforming Mars rest on the idea that, with some do-able modifications, the Martian environment could support plant life from earth. One mission being floated around the 'net is landing an inflatable greenhouse, and experimenting with growing living things on Martian soil. That might also give any manned missions the handy knowledge of how to grow their own supper while on the red planet.

  • ISRU experiments: Much like on the Moon, this means learning to use native resources of another world, such as ground ice, minerals in the soil and rock, and even the gasses in the air, to build, maintain, and power human activities.


Above: the surface of Venus, as seen by a short lived Russian lander.

If you can go to Mars you can get to Venus - but the morning star planet has the most challenges of any world Dragon two could reach: The surface pressure is over ninety atmospheres, and the temperature is four hundred degrees Celsius plus. Probes have made it to the surface before, but haven't lasted long. However there's a lot of interesting science to be done at Venus, as Europe’sVenus Express spacecraft showed, and which Japan's Akatsuki is now following up on:

  • The atmosphere is a complex mystery of interacting chemical processes.

  • The atmosphere also contains a layer, at 70km altitude, which is actually the most Earth like environment in our solar system, and might one day be suitable for a manned visit by a balloon bourns space craft.

As well as the possibility of landing some kind of hardened probe on the Venusian surface, Dragon 2 could be used to drop a serious balloon mission into the atmosphere. Venus air is less like earth's atmosphere, and in many ways more like our oceans - there are plenty of mysteries, and even speculation of airborne bacteria, that could be explored without needing to go near the hellish surface.

The moons of Jupiter:

Above: An artists impression of Jupiter, seen below the plane of its moons.

In general outline Jupiter's system of moons resembles its own miniature solar system - and each of the four main moons (Io, Europa, Calisto, and Ganymede) has its own unique character. A Dragon two mission to any of them would be able to carry less than a Mars mission, and would need radiation shielding... but there’s a lot to do there:

The most volcanic world in the solar system, Io's surface is a complex and ever changing smorgasbord of lava lakes, gigantic volcanoes, and complexsulphur based chemistry. A lander mission to Io would open up a window onto one of the most fascinating and alien environments in the solar system, not to mention being an enormous technical achievement.

The other world in Dragon 2's range which could easily have a whole book written on it, Europa has had astrobiologists practically drooling ever since it became clear that there's an ocean beneath the icy crust. Kept liquid by the heat from Io-like volcanoes, how far below the ice the ocean lies is upfor debate. Jumbled regions of ice called chaos terrain suggests that there are areas where it can break through to the surface. More evidence of the ocean reaching the surface emerged last year, when a plume of water vapour was seenshooting up above the surface by Hubble. A lander mission in then right spot could give us a chance to sample ice that was once water in the ocean - and if that ocean supports life the evidence for it could be right there to be picked up.

Although it doesn't receive the same amount of tidal heating as Europa, Callisto may well have its own internal ocean, albeit at over 150 km depth. it's surface is ancient, and something of a mystery - it's not clear exactly how old it is, or if it ever interacted with the internal liquid layers. Organic compounds have been detected on the surface, suggesting that there's scope for life-like chemistry to have gotten started if the surface did have contact with the ocean.

Yet another world with an internal ocean, Ganymede is the largest Moon in the solar system, and like Io and Europa, has a hot core capable of driving geologic activity. The cores churning gives the moon a planet like, magnetic field, and it even has its own faint aurora's. Ganymede’s surface is broken into brighter and darker areas, possibly indicating that some areas were changed by cryovolcanism - which would mean that a lander on Ganymede might have a large selection of material from the internal ocean to study.

Above: An artists impression of the surface of Io, near a lava lake.

Being a jack of all trades will undoubtedly give the Dragon two capsule some disadvantages compared to a probe customised for a particular destination, but Musk's ambitions overall seem to be driving down the cost of space travel via standardisation and re-usability. And, if it works, it might help open a new age of exploration....

*Although, in all seriousness, a one-way manned mission has been suggested.

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