The Curiosity rover landed on Mars a few weeks back. To do this it went through a complicated atmospheric entry procedure to slow down from orbital velocity before deploying a very large parachute capable of providing an effective drag force in the thin Martian atmosphere. Curiosity made it to the surface safely, and did so largely because it’s the beneficiary of about forty years of experience in successfully – and not so successfully – landing stuff on Mars. But probe landings were not always so refined.

The first probe to successfully reach the surface of another solar system body was Luna 2. Note that I say “successfully reach the surface of” and not “land on” because Luna 2 didn’t land on the Moon. Instead it was pretty much fired into it; when Luna 1 missed the Moon by 6000 km because of a mis-timed engine burn just hitting the target was seen as a success. There wasn’t a huge amount left of Luna 2 after the impact (or at least I assume so; it’s not like we can just send someone up there to check), but believe it or not the Soviets did actually intend for some of it to make it through intact. The rear-facing side of the probe contained several Soviet pennants as well as a small explosive charge designed to fire just before impact and slow the pennants down to the point where they wouldn’t be vaporized on contact with the lunar surface, so who knows? Maybe there’s a couple of burnt and twisted Soviet flags up there who have had to live for the last half century without the PR benefit of a full colour photo of Buzz Aldrin standing next to them.

That’s a hard landing. The space race demanded that one or the other of the competing nations eventually perfect a method of soft landing whereby the landing craft (and the occupants) made it through intact. The Americans plumped for the method documented on here last week, testing it extensively with their Surveyor series of lunar probes: a retrorocket fired to slow the Surveyor craft down from orbital velocity and the descent was handled automatically by attitude thrusters and doppler radar. It might sound sophisticated compared to the Soviet efforts, but it was far from perfect to begin with as two of the seven Surveyor spacecraft (unintentionally) crashed into the moon. Still, as a method of prototyping the lunar lander mechanism the Surveyor program was a great success and contributed immensely to all twelve Apollo astronauts that actually landed on the moon getting back alive.

NASA was taking things comparatively slow and steady compared to the Soviets (although they too fired a bunch of Ranger probes into the moon in 1964 and 1965 so it’s not like celestial target practice was a purely Russian conceit). After a frenetic series of failed attempts – likely because they were trying to beat the Surveyor program which successfully touched down later the same year and so weren’t fully testing everything – the Soviets got Luna 9 to make a soft landing on the Moon in 1966. This pioneered the landing bag method whereby a huge bag inflated just before impact to cushion the spacecraft and slow it down to the point where it could survive the landing, just like the airbag in a car. Sounds a bit crude, but more refined versions of the concept are used in pretty much every single probe that lands on Mars these days; the picture above is the Pathfinder landing bags being tested, although they’re much smaller than Luna’s as Pathfinder also had the benefit of a parachute to slow it down.

(The Soviets did eventually switch to the Surveyor method of attitude-adjusting engines controlling descent when they wanted to do some serious lunar exploration; Luna 17 disgorged the terrifying Lunokhod 1 rover upon landing, which made history as the first mobile robot explorer of another planet)

That’s how you land on the Moon. It’s both easier and harder than landing elsewhere because the lack of atmosphere preclude the use of parachutes/other atmospheric maneuvers while simultaneously allowing very efficient RCS systems to control descent. Landing on Mars is a pretty well-worn path thanks to the Viking and Pathfinder landers, the Spirit/Opportunity/Curiosity rovers and so on; thanks to the relatively forgiving environment they all use the same method of protecting the payload in an aeroshell, slowing descent using parachutes and then cushioning the landing with airbags. But what if we want to go somewhere a little more… exotic?

As far as I’m aware the only other solar system bodies we’ve managed to land probes on are Venus and Titan. I’m actually kind of surprised we went for Venus at all when there’s other much lower-hanging fruit to be found out there; Venus is one of the most hostile environments in the solar system with a surface pressure of close to 100 bar (that is, 100 Earth atmospheres) and a temperature of about 450 degrees Celsius. That the Soviets managed to get half a dozen probes down there at all was a massive achievement. That they actually got pictures back was nothing short of astonishing. Still, it’s not like the Soviets ever took half-measures when it came to space exploration; the Venera landers weighed several tons, which in probe terms means they were armoured like tanks. To get such a heavy load through the thick Venusian atmosphere at all they had to do this:

During descent, heat dissipation and deceleration were accomplished sequentially by protective hemispheric shells, three parachutes, a disk-shaped drag brake, and a compressible, metal, doughnut-shaped, landing cushion.

And even then the longest a Venera probe ever lasted on the surface of Venus was just short of two hours before it succumbed to the hellish environment and stopped transmitting. Now Venus is spoken with in the same hushed tones as Ravenholm: we don’t go there any more.

Then there’s Huygens, the only man-made probe that ever made a landing in the outer solar system. Compared to Venus, Titan is a paradise with a reasonably thick methane atmosphere you can deploy a parachute in, but which won’t crush the probe once it’s down on the surface. Huygens only transmitted for about two hours; however, it was a probe on a budget and that’s all it was designed to do. The only complication facing Huygens was the fact that it landed on a “shoreline” adjacent to a large dark area that may or may not have been a huge ocean of hydrocarbons. If it had been an ocean, and if Huygens had landed in it, it would have been an even shorter mission than intended; while the possibility that the probe might land in a liquid environment had been considered, it was only designed to transmit for a few minutes before sinking below the sub-zero waves.

We’re pretty good at landing stuff in oceans thanks to the space race, though, to the point where it’s actually the least of our worries as long as we can plan for it. In fact, as the Venera Venus landers show we can land probes pretty much anywhere with a solid surface as long as we know about the environment they’re going to be landing in. Again, this demonstrates the iterative nature of spaceflight; you need to make a lot of failed attempts in order to gather the data you need to make the successful one. Even smashing a probe into a planet a la Luna 2 yields some useful data in that it proves you can hit the target. Luna 9 just landing on the moon was of great interest because it proved the moon had a solid surface you could walk around on (it was thought that the dust on the lunar surface might be so deep it would effectively constitute quicksand). So really there are no true failures in probe spaceflight.

(Except for Beagle 2, where they don’t even know what happened to it.)

The post Probe Landings. appeared first on The Scientific Gamer.

Baron von Awesome asks

How likely is this?

http://www.bbc.co.uk/news/health-17439490

I can’t be bothered to listen to the full programme so I demand that you do the hard work for me. I’m expecially interested in how he plans on getting the fuel to Mars if he wants to refuel there.

I’m thinking he’s living on another planet already when he suggests the average person could afford it at half a million dollars.

I am disappointed to read this article because I thought SpaceX was doing quite well on the whole “Not being a complete laughing stock” thing up until this point. Their Dragon capsule is a nice piece of engineering, it’s going through the teething troubles all new spacecraft go through but it’s recently made a successful flight to the ISS, and it does have the capacity to potentially go to Mars at some point (albeit with some significant redesign and development required). You don’t achieve all this by being utter morons, and so I can only assume that the CEO of SpaceX doesn’t believe a word he’s saying here and is just trying to drum up publicity (and investment) because nearly every assertion he makes is complete balls.

Oddly enough the one assertion that isn’t is the one you bring up: refuelling on Mars. You don’t need to take fuel to Mars to refuel. The fuel is already there. The most common types of rocket fuel are a mix of liquid hydrogen and liquid oxygen, two elements that are particularly abundant throughout the solar system in the form of frozen water ice. Mars has ice caps, so the fuel is potentially just sitting there waiting for us if we can just refine the stuff.

However, then he goes completely off the rails by saying we can build a spacecraft that is “completely reusable”. Hey, you know what else was supposed to be completely reusable? That’s right, it was the Space Shuttle, and that thing ended up costing more than disposable capsules because it had to undergo extensive maintenance every time it came back from a mission to ensure it could make another one without killing everyone on board. Making your spacecraft reusable does not necessarily make it cheaper, and the concept of a reusable Mars spacecraft really does boggle the mind. Christ, it’s not like popping out to the shops in your car for a pint of milk and a loaf of bread. It’s Mars. He’s talking about something that even NASA won’t have the practical capacity to do for a decade or more, and which will require significant R&D investment. Justifying that is bad enough when you’re government-funded, but a private spaceflight company will have to recoup the R&D cost somehow, and the only way they can is by folding it into the price they charge for trips out to the Red Planet and back.

So while there is fuel on Mars, saying that we can reduce the cost of interplanetary space flight to just fuelling and refuelling the spacecraft is insane. The aerospace sector has all sorts of hidden costs associated with it, which is why military procurement contracts often have very optimistic cost-per-unit projections made as part of the bid process that soon balloon up to several times the original estimate after the ink is dry and reality begins to bite. Research, maintenance, establishing the necessary mechanical expertise, manufacturing procedures and industrial base, as well as the money that will be required to overcome any genuinely unforeseen problems that crop up during the development process – all of these things will cost cold, hard cash, and all of these things are going to have to be factored in to the cost of a ticket.

This is why his estimated price of half a million dollars per person is absurd. It’d cost at least that much in terms of life support technology and the salary you pay to ground control teams (yes, you can’t automate everything just yet) to keep them alive during the trip. This is saying nothing of the fact that a trip to Mars would be acutely uncomfortable for astronauts trained to deal with the rigors of space travel; anyone shelling out half a million dollars is probably going to want some creature comforts that don’t involve, e.g., having to stick their dick into a vacuum cleaner every time they want to pee for eighteen months. Bone degradation? Muscle atrophy? Radiation poisoning? These are not problems you can throw money at to make them go away. Going to Mars is something that has real risk attached to it; it’s the sort of thing that you pay people half a million dollars to do, and I really think you’d have problems charging people even that tiny amount once you’d explained all the bad things that could happen to them as a result of the trip.

The problems involved in opening Mars up to space tourism really do boggle my mind. They’re an order of magnitude greater than commercial trips to the Moon, and this guy thinks we’re going to have the capability to offer these low-cost flights in – at worst – fifteen years time? No he doesn’t. He can’t. If he does, he’s an idiot who doesn’t understand his industry, and while I admit this would not exactly be unprecedented for a company CEO the success Dragon has had so far indicates there is at least somebody at SpaceX who knows what they’re doing, and who would have stormed into the room and wrestled the microphone away from this guy if they thought he had any serious intention of actually trying to do this stuff. It’s a pure PR puff piece, a chance for SpaceX to big itself and its industry up in the media, and nothing more.

The post Two Weeks. appeared first on The Scientific Gamer.

A month or two back there was a news article (or several) about how spending long-duration flights in space caused astronauts’ eyesight to deteriorate. Since “long-duration” in this case means flights of over a month in low earth orbit the doctors who published the study were rightly concerned about the effect a longer trip in space might have on the astronauts making it; any exploration of the solar system outside of the Moon’s orbit is going to involve flights lasting many months, meaning that this symptom of time spent in low-G environments – which wore off after the astronauts had spent a week or two back on Earth – might suddenly become a hugely relevant problem. However, while I completely get that this is a bad thing that must be avoided or mitigated if at all possible, when you stack it up against the other hazards involved in true long-duration space flights it starts to look positively benign. If only cataracts were the worst an extended journey in interplanetary space could do to us. Unfortunately it’s not quite that simple.

The list of things that can go horribly wrong during even a routine flight up to the ISS in LEO is a very long and varied one. Mostly they revolve around some kind of catastrophic equipment/craft failure like the Columbiadisaster, and despite being only a few hundred kilometres away from the surface of the Earth the chances of astronauts surviving such a catastrophic failure are not particularly higher than they would be if they were in orbit around Mars. However, while spacecraft are complex they are also some of the most rigorously tested machines in history with multiple failsafes; the only reason the shuttle had any fatalities was because of its reusable nature, and the US (at least) has zero other in-flight astronaut fatalities despite making numerous trips to the moon. This makes flights to LEO reasonably safe, and even the moonshots weren’t that hazardous. Modern-day spaceflight isn’t as risky as you might think, and there’s no equipment-related reason why, if the appropriate precautions were taken, a Mars mission wouldn’t be equally as safe.

So if we were to hypothetically spend some astronauts out to Mars, we could be fairly certain that their own spacecraft wouldn’t kill them. That’s good, because there’s a lot of other stuff that can either kill or cripple them in unpleasant ways. Probably the primary concern is cosmic radiation. This is exactly the same as “normal” radiation you’d find spewing out of a breached nuclear reactor – i.e. incredibly dangerous and deadly. There’s a region of space surrounding the Earth called the Van Allen belts which is highly radioactive, but the moonshots proved that astronauts can pop through the belts very quickly without suffering any long-term ill effects. Interplanetary space features a moderate level of background radiation, and Mars astronauts would spend enough time in interplanetary space (9-12 months each way) to have a higher risk of developing radiation-related diseases such as cancer. The big problem, however, is coronal mass ejections, or “Sun burps” as I once described them to a class of ten year olds.

Coronal mass ejections are exactly what it says on the tin: the Sun vomits forth a whole bunch of harmful particles and electromagnetic waves that sleet throughout the Solar System and blanket everything in high-energy radiation. If you’re on the surface of the Earth you usually won’t notice a CME since you’re protected from harmful cosmic radiation by the magnetosphere. All you’ll see are some very pretty aurorae if you happen to live at the correct latitudes. Anyone who happens to be situated higher up in the Earth’s atmosphere – high-altitude planes, astronauts in LEO – are at slightly greater risk but their exposure, if any, will be very short term and almost certainly harmless. Astronauts in interplanetary space are in for a whole world of hurt, however; toutside the magnetosphere there’s nothing to protect them from cosmic radiation, and while the skin of their spacecraft should block some of it high-frequency gamma waves will go right though the spacecraft and the astronauts inside it, shredding their DNA and probably causing horrific organ failure within 72 hours. In other words, being caught unprotected in interplanetary space when a CME hits is like staring an unshielded nuclear reactor in the face, turning anyone unlucky enough to do so into a walking corpse.

What can we do about CMEs? We can’t predict them, so while it’d probably be a good idea to launch a Mars mission in a period of low solar activity to try and minimise the risk we also have to make sure that if one does happen it doesn’t spell instant death for the astronauts on board. The only way to do this is shielding, and lots of it. Only very dense materials like lead provide adequate shielding against gamma radiation, and the drawback of this is that dense materials are also heavy. Getting enough lead into orbit to shield the entire spacecraft is completely out of the question; the best we could do is a radiation-shielded chamber that the astronauts could retreat to when a CME occurs. The good news is that CMEs travel at the speed of the solar wind and take several days to reach the Earth, so the astronauts would have plenty of warning that one was coming up, and since they only last a matter of hours it’s entirely feasible to have them shelter inside the chamber for the duration.

So the radiation problem is one which can be overcome to the extent that we can be fairly sure the astronauts won’t die en route, although they’d be at significantly higher risk of developing cancer than the average person. A trickier problem is muscle and bone deterioration in low-g environments. When you’re walking around on Earth your body is under constant tension in order to counteract the force of the Earth’s gravity. You may not notice it, but your muscles are constantly doing work just to keep you standing upright. Remove the gravity and the muscles stop doing the work, and since muscles are lazy bastards they will immediately start to waste away. Worse is the fact that since bone grows in response to taking loads, no load means the body starts to reabsorb bone minerals and the bones begin to atrophy. This is potentially far more serious than muscle atrophy, which can be reversed in a few months on the ground; bone atrophy can take years to correct, and the longer you are in space the worse the degree of atrophy. A two-year round trip could inflict permanent skeletal damage to the astronauts involved.

Happily there is also something we can do about this, and that something is an absolute crapload of exercise. The daily schedule of an astronaut usually features at least 2-3 hours of workouts in order to give muscles something to do and stop them from getting weaker, and this has had good results in counteracting muscle atrophy. No-one has (as far as I know) come up with a decent solution to bone atrophy, although the effects can be ameliorated by having astronauts wear elastic braces that compress their limbs and provide some of the mechanical stress that’s missing in a weightless environment. Importantly the space endurance record of 437 days is longer than a one-way trip to Mars would be, and the guy who did that recovered fully from his experience¹ thanks to a punishing exercise regimen that he stuck to religiously. It is possible to send people to Mars and back without having their bones shatter the moment they set foot back on Earth.

Finally there is the psychological component, and this is one that’s less understood. It is possible to find people who can survive over a year spent in a small tin can without going crazy; that part is no problem. The tricky part is finding a group of people who can spend over a year in a small tin can without killing each other. There are some indirect comparisons you can draw with nuclear missile submarines, which at the height of the Cold War were submerged for months at a time, but even the cramped confines of a submarine would look positively roomy when compared to the living space available to a prospective Mars astronaut. Being stuck in such an environment with the same faces day in, day out, for two years is a significant psychological burden to carry, which is why there’s a number of studies currently going on to see what happens to people in those conditions. For example, Mars 500 was an experiment which locked six volunteers in a Mars craft mockup for 500 days in order to test both the psychosocial effects of that confinement and the ability of the volunteers to adequately deal with any complications that might arise, like a medical emergency. Mars 500 concluded successfully, but while I’m no psychological expert I suspect that no Earth-based mockup will be able to adequately reproduce the feeling of isolation that being several million miles from Earth will create. The true effects of this one aren’t going to be fully known until we actually do it.

Anyway, when weighed up against muscle wastage, bone disintegration, possible irradiation, higher cancer chances and the ever-present risk of going nuts, some slight vision impairment starts to seem a little bit trivial. Certainly I don’t think an astronaut, when presented with the chance to go to Mars, will say “Well I could do that, but on the other hand it might damage my eyesight!” Spaceflight is full of risks, and they are used to taking them. One more isn’t going to make any difference whatsoever.

1. Nearly all the spaceflight endurance records are held by Russians; this is because Russians are intrinsically crazy. Also because one of the main reasons for them putting Mir up there was so they could investigate what long-duration spaceflight would do to people, I guess. But mostly because they’re crazy.

The post Each New Frontier. appeared first on The Scientific Gamer.