The past few days has been good to me. I'm taking 20 credits at Tacoma Community College, goal being an university transfer degree in engineering so I can go to University of Washington to obtain a bachelor's in aeronautics and astronautics. The classes look much more interesting than what I had at Rochester Institute of Technology - Intro to Philosophy is actually going to have debates in the last few weeks of class! RIT did not have these, which shows me that, while it isn't a half-bad school, it is alarmingly egg-headed.
Other than Intro to Philosophy, I'm taking Intro to Psychology, Psychology of Human Sexuality, and Calculus I. Three of these four I am repeating from the Institute in order to raise my GPA. Once I complete Calculus I satisfactorily, I should be able to get to the real meat of my degree.
Tuesday, September 25, 2007
Thursday, September 20, 2007
Mars Oracle Sample Return & Ballistic Hopping w/ Carbon Dioxide ISRU
More than a year ago, a private consortium called MarsDrive posted a design contest for a robotic sample return mission to Mars. The rationale for this mission is that it's very expensive to send any payload beyond Earth's orbit, hence the laboratories we can put on Mars will have to be very small. With the limitations of robotic technologies and the long radio delay between Earth and Mars, even the best robotic mission we can send will never compare to what humans can do in a fully-equipped laboratory. If we can just get a few grams of Martian soil (referred thereafter as regolith) and rocks and bring them back, we could analyze them for years on end. With this data, it will support an eventual human presence on Mars.
There's just one other thing. Mars enthusiasts will already know what I'm talking about, but I'm writing this mostly for the layperson. The amount of fuel required to get to Mars and back is no mean number. There is no way we can do this mission, much less a human trip, if it carries all of its own propellant. That's where In-Situ Resource Utilization (ISRU) comes in play. A decade ago, Dr. Robert Zubrin came up with a way to manufacture a number of propellants on the Martian surface from liquid hydrogen and indigenous carbon dioxide. This method cuts the amount of propellant brought to Mars by a huge factor. Since then, almost all sample return concepts have included ISRU.
Now for the contest. Even with ISRU, a Mars sample return mission will still carry a stratospheric price tag and a huge burden of risk. Simply put, we haven't yet launched a payload from Mars. There are many things that could go wrong, and testing all the potential points of failure has its own astronomical budget. This is why MarsDrive decided to post this contest, to bring out the most innovative and cost-effective sample return plan. There are six of us competing and each one of us have posted an entry very different from the others. So far, we're on our second-generation plans. I admittedly went into this contest without knowing the faintest thing about space mission design, having completed only two years of mechanical engineering at Rochester Institute of Technology, so my first draft was a bit embarrassingly... amateurish. But since MarsDrive posted ALL of our first-draft entries, I've gotten a good look at each of them and concluded that two of them were much better than mine and the rest worse (much less thought out). That put mine in the middle. Not bad for someone who's completed only half of his education, right?
So after an interminable delay in which MarsDrive couldn't get its judges together (lucky stroke for me!), they gave us a three-month window of opportunity to update our entries. They're all due at the start of November. I've been working tirelessly to come up with a much better plan than the ones who "beat" me last time. My first draft included a ballistic hopper that runs on indigenous carbon dioxide, but I erroneously combined it with the ascent vehicle. Bad judgment on my part. So this time, I'm separating it from the ascent vehicle (to increase performance on both vehicles) and introducing a number of things that will make the mission even more cost-effective than my competitors.
I have called my design plan Mars Oracle. Based on this name, the two vehicles of this mission are the return vehicle (Delphi) and the ballistic rocket hopper (Socrates). The ballistic hopper has its own documentation in aerospace circles, as it is already being considered for future Mars rover missions because of its potential to investigate a wide array of sites separated from each other by distance and impassable terrain. I thought it would be perfect for a sample return mission for that reason (can get a much more diverse assortment of samples)
Instead of a rover that runs under its own power, I chose a design based on one of the studies done by the European Space Agency. It is a small rover that runs on caterpillar tracks, like a tank, and is capable of reconfiguring itself from a roving position to a drilling position. Because of mass reasons, It does not run under its own power. Instead, it gets all of its power and communications through a tether connected to the hopper (and return vehicle). That way, this rover can be carried by the hopper very easily. I envision this mini-rover to weigh the same as Sojourner did, but with a much greater instrumentation-to-mass percentage because it doesn't have to carry solar panels, antennas, etc etc.
After much agonizing, I eliminated liquid hydrogen from the ISRU scheme. It's a bitch to store on Earth (hydrogen economy advocates listen up!), even worse in space, and very little better on Mars. Because of its low molecular weight, it can leak out of a solid-metal tank. This so-called boil-off forces the mission to carry a greater amount than necessary, and it embrittles metal in the process. To make matters worse, liquid hydrogen is an ultra-cryogen, meaning that it must be stored at infernally cold temperatures. How cold, you ask? Well, as cold as space can get, but that's not half of it, because space can get uncomfortably hot sometimes. Not even Mars can get as cold as liquid hydrogen has to be, which leads to thermal management complexities that, while can be done, are still unnecessary. And even after all of this, it can still boil off! Even with zero-boil off storage technologies, there's the extremely low density to contend with, which leads to heavier and bigger tanks for the equivalent amount of fuel.
I won't name my choice of fuel for fear of my competitors peeking in. But rest assured that it's much more dense than liquid hydrogen, burns very well in carbon dioxide, and easily storable in space and on Mars (i.e., it doesn't boil off). It's a bit on the toxic side, but that won't be a problem for these technicians on the launchpad.
All in all, I think Mars Oracle has the potential to be much more robust and leaner than its competitors. But we'll see how the judges decide on that come May.
There's just one other thing. Mars enthusiasts will already know what I'm talking about, but I'm writing this mostly for the layperson. The amount of fuel required to get to Mars and back is no mean number. There is no way we can do this mission, much less a human trip, if it carries all of its own propellant. That's where In-Situ Resource Utilization (ISRU) comes in play. A decade ago, Dr. Robert Zubrin came up with a way to manufacture a number of propellants on the Martian surface from liquid hydrogen and indigenous carbon dioxide. This method cuts the amount of propellant brought to Mars by a huge factor. Since then, almost all sample return concepts have included ISRU.
Now for the contest. Even with ISRU, a Mars sample return mission will still carry a stratospheric price tag and a huge burden of risk. Simply put, we haven't yet launched a payload from Mars. There are many things that could go wrong, and testing all the potential points of failure has its own astronomical budget. This is why MarsDrive decided to post this contest, to bring out the most innovative and cost-effective sample return plan. There are six of us competing and each one of us have posted an entry very different from the others. So far, we're on our second-generation plans. I admittedly went into this contest without knowing the faintest thing about space mission design, having completed only two years of mechanical engineering at Rochester Institute of Technology, so my first draft was a bit embarrassingly... amateurish. But since MarsDrive posted ALL of our first-draft entries, I've gotten a good look at each of them and concluded that two of them were much better than mine and the rest worse (much less thought out). That put mine in the middle. Not bad for someone who's completed only half of his education, right?
So after an interminable delay in which MarsDrive couldn't get its judges together (lucky stroke for me!), they gave us a three-month window of opportunity to update our entries. They're all due at the start of November. I've been working tirelessly to come up with a much better plan than the ones who "beat" me last time. My first draft included a ballistic hopper that runs on indigenous carbon dioxide, but I erroneously combined it with the ascent vehicle. Bad judgment on my part. So this time, I'm separating it from the ascent vehicle (to increase performance on both vehicles) and introducing a number of things that will make the mission even more cost-effective than my competitors.
I have called my design plan Mars Oracle. Based on this name, the two vehicles of this mission are the return vehicle (Delphi) and the ballistic rocket hopper (Socrates). The ballistic hopper has its own documentation in aerospace circles, as it is already being considered for future Mars rover missions because of its potential to investigate a wide array of sites separated from each other by distance and impassable terrain. I thought it would be perfect for a sample return mission for that reason (can get a much more diverse assortment of samples)
Instead of a rover that runs under its own power, I chose a design based on one of the studies done by the European Space Agency. It is a small rover that runs on caterpillar tracks, like a tank, and is capable of reconfiguring itself from a roving position to a drilling position. Because of mass reasons, It does not run under its own power. Instead, it gets all of its power and communications through a tether connected to the hopper (and return vehicle). That way, this rover can be carried by the hopper very easily. I envision this mini-rover to weigh the same as Sojourner did, but with a much greater instrumentation-to-mass percentage because it doesn't have to carry solar panels, antennas, etc etc.
After much agonizing, I eliminated liquid hydrogen from the ISRU scheme. It's a bitch to store on Earth (hydrogen economy advocates listen up!), even worse in space, and very little better on Mars. Because of its low molecular weight, it can leak out of a solid-metal tank. This so-called boil-off forces the mission to carry a greater amount than necessary, and it embrittles metal in the process. To make matters worse, liquid hydrogen is an ultra-cryogen, meaning that it must be stored at infernally cold temperatures. How cold, you ask? Well, as cold as space can get, but that's not half of it, because space can get uncomfortably hot sometimes. Not even Mars can get as cold as liquid hydrogen has to be, which leads to thermal management complexities that, while can be done, are still unnecessary. And even after all of this, it can still boil off! Even with zero-boil off storage technologies, there's the extremely low density to contend with, which leads to heavier and bigger tanks for the equivalent amount of fuel.
I won't name my choice of fuel for fear of my competitors peeking in. But rest assured that it's much more dense than liquid hydrogen, burns very well in carbon dioxide, and easily storable in space and on Mars (i.e., it doesn't boil off). It's a bit on the toxic side, but that won't be a problem for these technicians on the launchpad.
All in all, I think Mars Oracle has the potential to be much more robust and leaner than its competitors. But we'll see how the judges decide on that come May.
welcome
Welcome to my blog. I'm Eric Shear, an aspiring aerospace engineer, first-time author, libertarian/anarchist, and freethinker. Here, you'll find my rants on almost about everything, including my projects. Because I do have a number of them going on right now.
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