Posts Tagged‘rtg’

An Armchair Scientist’s Mission To Europa.

If there’s any place in our solar system that we’d want to start seriously looking for life it’d be Europa. The dust covered snowball of a moon likely contains a vast subsurface ocean, one that is kept liquid by the giant gravitational forces of its host planet Jupiter. This makes Europa a great candidate for life as we know it as once we find water it’s inevitable that we find life shortly thereafter. The challenge with Europa though is getting to that subsurface ocean to study it as it could be covered in several kilometers of water ice, not something you can simply puncture through. Whilst there are numerous people more qualified than me on this subject, many of them actually working in the aerospace industry, with NASA asking for ideas for a potential mission to Europa I figured I’d throw my 2 cents in.

Europa

So the total budget for the potential mission is a cool $1 billion and whilst that sounds like a lot of money projects that I’d consider simpler than my idea (like say Curiosity which was $2.5 billion) but I think there’s potential to build a platform that could fuel further missions. With that in mind this initial mission is likely only to be a scouting mission, one that will give us the most detailed picture of Europa possible so that the follow up mission can choose the perfect site to land on and commence the search for life in its vast underground ocean. My proposal then is to develop a compact nuclear reactor (not a RTG) to power a scouting craft laden with instruments to analyse the gravitic field and surface of Europa. This craft will be able to find the point at which the surface ice is the thinnest and identify potential landing sites for the second generation craft: a cryobot that will punch through to the ocean below.

Putting a nuclear reactor into space might sound like the plan of a crazed sci-fi nerd but there’s actually been dozens of small prototype reactors launched into space with all of them proving to be safe and reliable. The power capabilities of such a reactor are far beyond that of what a small satellite would usually require however attempting to melt through kilometers of ice will require power of that scale. Thus it would make sense to fund research into developing the power supply first and then validating it on the scouting craft. Then, once that mission is successful, the reactor can be scaled to the appropriate dimensions for the cryobot mission and even used in other deep space programs.

Having such a generous amount of power available also opens up the opportunity to using instruments on the scouting craft which would not be feasible, typically. Things like high-power antennas (which could function as a relay for the follow up mission), radar imagers or bigger and better versions of other instruments. My knowledge on the power requirements of various instruments is limited but I know that even the most advanced RTGs, like the one in Curiosity, produce a measly 125W. Being able to draw on several kilowatts, an order of magnitude more power, seems like it would open up many opportunities that just weren’t possible previously.

I’m probably vastly underestimating how much it would cost to develop such technology, especially in today’s nuclear hostile political environment, but if we’re serious about actually digging under Europa’s surface I don’t see what our other options would be. Melting through giant sheets of ice is no small task and one that has requirements that far surpass anything we have currently. Using that $1 billion mission to set ourselves up for future exploration seems like the best bet especially considering how many other applications a safe, small nuclear reactor would have.

The Next Generation Mars Rover Ready For Launch.

The Mars rovers Spirit and Opportunity are by far one the most successful mission we’ve ever had on another planet. Designed for a total mission time of only 90 days they have gone on to outlive that deadline numerous times over and if it weren’t for an insidious soil trap they’d both still be running today. Whilst Opportunity might still be running a good 7 years after it made planet fall that doesn’t mean that it’s capable of performing all the tasks we want to do and so NASA has been busy designing a replacement rover. It’s quite something to behold and it just recently hit a very important milestone.

The next rover’s official name (dubbed Curiosity in a contest to name it, much like its predecessors) is the Mars Science Laboratory and considering its payload that’s fairly apt. Compared to the Mars Exploration Rovers it’s quite the beast being 5 times more massive and carrying 10 times the scientific payload. To put that in perspective the MSL will be about the same size as the Mini Cooper, the MERs combined would only equal it in length. Such size does present some challenges for getting it down on Mars however, but the guys at NASA have devised a really ingenious way of making sure it arrives safely.

Many are familiar with the way that the MERs made their landing on Mars. They used a combination of aero-breaking (basically parachutes) combined with inflatable bags on the outside that allowed them to bounce over the surface until they landed safely. The MSL is just too heavy for that kind of landing to work so NASA has devised a multi-stage descent that utilizes aero-breaking, retrorockets and a crane system to drop it safely on the surface. I could try and explain it to you but its far more impressive to see in video:

Compared to the way the MERs landed this does seem like an extremely overcomplicated way of landing but given the constraints it’s the best option available. NASA is stepping into unknown territory here so until the landing is confirmed I can see everyone being on tenterhooks.

Keen observers would have noticed something different about the MSL when compared to its MER cousins, most notably the distinct lack of solar panels. The MSL gets all of its power from a radioisotope thermoelectric generator (RTG), the same device that’s powered Mars landers and the extremely long lived Voyager probes. These devices work by using the heat from radioactive decay of an element, usually enriched plutonium, and generating electricity via a thermocouple. The RTG on board Curiosity will generate around 125W of power when its launched, dropping to 100W only after 14 years in service. The mission time frame is slated for just under 2 earth years so the RTG is more than up to the job and there’s the tantalizing possibility that this particular rover could be working for a very long time to come.

The MSL’s payload is simply staggering so I won’t recreate it fully here but there are a few interesting pieces that I’d like to highlight. The first is the MastCam which is a high definition camera that will sit on top of Curosity’s mast. It’s able to take 1.92 megapixel images and 10fps 720p video in true colour, something that other rovers have had to fudge with their black and white cameras with colour filters. There’s also ChemCam which has an infrared laser capable of vaporizing rock at 7 meters then analysing the resulting plasma ball, which is just plain cool (lazers, IN SPACE!).

The milestone I was hinting at earlier was that the MSL has just been sealed up in its payload faring, ready for the trip to Mars:

With its launch window opening in less than two months, the Mars Science Laboratory was matched up with its heat shield at Kennedy Space Center’s Payload Hazardous Servicing Facility on Wednesday, Oct. 5.

The completed MSL rover, a.k.a. “Curiosity,” had already been fitted onto the “back shell powered descent vehicle” — a revolutionary landing mechanism that will first deploy parachutes to slow the capsule’s descent and then use rockets to hover above the Martian surface as it carefully lowers the one-ton rover down on cables before finally launching itself away to fall at a safe distance.

The launch is scheduled to happen between November 25th and December 18th this year with the rover reaching Mars sometime in August next year. After that it will begin its 1 martian year mission, which is just a hair under 700 earth days. With the rover being fitted into the fairing now it signals that NASA has quite a good shot at hitting that launch window, especially when they’re using the tried and true ATLAS V launch system.

Curiosity really is a testament to what NASA is capable of when they put their minds to it. Everything about the new rover is boundary pushing and I’m sure that much like its predecessors it’ll continue to serve NASA and humanity long after its initial mission is completed. It’s going to be agony waiting for the landing confirmation but we’ve got a year and a long trip through space before we have to start worrying about that. 

Power in Space.

One thing that’s always a big issue for any project in space is how you’re going to power whatever you’re sending up there. As it turns out the methods that we use to generate power up in space are extremely varied and in fact many of them paved the way for technologies we now use back here on earth. However there are still some advances to be made and if we are to return to the moon and beyond there will have to be a breaking down of some old barriers in order to enable us to go further into space.

Many of the initial space craft that were sent up just had your traditional chemical batteries in them. For the most part these worked well, and since they had been around for such a long time they were a proven technology (something that is critical in any space endeavour). As time went on and missions became much more ambitious NASA moved from batteries to fuel cells and were the first to fly these in a space craft on their Gemini missions. Fuel cells are advantageous because not only do they produce power, but typically a decent amount of heat and water as well. In fact they are still used to power the space shuttle and will typically produce around 500 litres of water on whilst in space. This is invaluable as that’s 500Kg less water they have to bring with them and 500Kg more they can take into orbit.

Satellites are another matter entirely. Since they don’t need any of those bothersome human things like water and heat fuel cells aren’t the right choice for them and the majority of artificial satellites in orbit around earth and our nearby neighbours use good old fashioned solar power. At the distance we are from the sun the available power is somewhere in the order of 1400W/m² but that drops off dramatically as we reach further out into the solar system. In fact the amount of power available past mars is so little compared to where we are that there is only one mission currently scheduled to Jupiter that uses solar panels called Juno.

So what do we use when we want to explore the deep reaches of space? The current technology used in most missions is called a Radioisotope Thermoelectric Generator (RTG) which in essence uses heat from decaying radioactive material to provide heat and electricity. In the past they’ve coped a lot of flack for using these as environmental groups lament the potential for damaging the environment and spreading nuclear material across the earth. NASA has done extensive research on the matter but still runs up against endless red tape whenever they try to use one. The usefulness of these devices really can’t be overstated as they’ve given us such missions such as Voyager 1, which has been going strong for over 30 years and is slated to last for at least another 15. This kind of technology is going to form the basis of any mission that attempts to leave our solar system.

NASA has begun to make inroads into producing small nuclear reactors that would be used to power a moon base. For any kind of long duration time in space us humans need quite a lot more power than our robotic counterparts and we won’t be able to use RTGs to satisfy this requirement. Whilst I do understand some of the environmental concerns if I was going to trust anyone sending nuclear material into space it would be NASA, as they have a long track record of getting hazardous materials out of our atmosphere without incident. Unfortunately the environmentalists haven’t seen it that way, and continually put up roadblocks which inhibit progress.

Eventually though I’m sure we will be able to power our space based devices using nuclear power without the worry and red tape that we have now. As time goes by NASA and other space agencies will prove that the technology is sound after repeated launches and the controversy will be nothing but a memory. It is then we can start to look further out into our solar system, and hopefully, beyond.