3 ms·

What you might "gain" in reduced complexity by getting rid of the arm you loose massively in being able to power the whole system efficiently in one go. If you

What you might "gain" in reduced complexity by getting rid of the arm you loose massively in being able to power the whole system efficiently in one go. If you split the 10.6 pounds of plutonium across N smaller drones you would need to duplicate N Radioisotope Thermoelectric Generators (RTPs), power electronics, batteries, radios, cameras, computers and probably a half a dozen other things I haven't thought of yet. This probe is going to be going for at very least 10 years - probably quite a lot longer, all because of the design choices around how it's powered.

todayiamme 14y ago
Again do we need all of those systems? Why can't you have two dedicated machines for earth communication and the rest communicate via a HF radio protocol? You don't need a RTG if it's say sojourner size and packs one payload on a standardised mobile base, solar panels will work just fine. Since you have redundancy built into the swarm you can skimp on a lot of things including computing power. Remember you can use group decision making for more complex "choices" and if you lose a few drones due to unforeseen obstacles, then objectively it shouldn't matter, so you don't need a lot of LIDAR and stuff as well. As far as heating and shielding goes then the smaller size actually works to your advantage. I don't see any reason why someone shouldn't make this. Yes these probes will be disposable, but that's the entire point. They can be used and thrown away opening doors to risk taking that we haven't really seen before.
- deeringc 14y ago
  > Again do we need all of those systems? Yes. Like I've said above the explicit purpose of this mission is to gather advanced scientific data which requires comparatively bulky instruments and high power availability. Because it is so ridiculously expensive to get anything to Mars you want it to last as long as possible. "Disposable drones" make absolutely no sense when it costs so much to launch them into orbit, transport them 60 million km across the solar system, and then enter the Martian atmosphere and land in a coordinated place on the surface. Each gram you get to that point costs many thousand dollars. You don't just plan your strategy around losing a bunch of them - that would be many hundreds of millions of dollars down the drain. Using a decaying nuclear isotope to power your probe you will get many multiples more bang for buck compared to solar powered probes which so far have maxed out at about 5 years. The solar concentration of a Martian winter is extremely low, and this problem is exasperated the smaller the probe and the resulting battery that it can carry. Just like in computing and electronics, physical and mechanical distributed systems are inherently complex - more so than monolithic systems.
  - todayiamme 14y ago
    >>> Yes. Like I've said above the explicit purpose of this mission is to gather advanced scientific data which requires comparatively bulky instruments and high power availability. Because it is so ridiculously expensive to get anything to Mars you want it to last as long as possible. "Disposable drones" make absolutely no sense when it costs so much to launch them into orbit, transport them 60 million km across the solar system, and then enter the Martian atmosphere and land in a coordinated place on the surface. Each gram you get to that point costs many thousand dollars. You don't just plan your strategy around losing a bunch of them - that would be many hundreds of millions of dollars down the drain. <<< I've thought about what you have said and I think that we are measuring the likelihood of success in different ways. I'm measuring it in terms of the likelihood one pair of devices will complete the outcome at the cost of all the others and, if I am correct, at some level you are measuring it in terms of reducing the possibility of a loss while achieving the mission objectives. I think that we can afford to build disposable machines because if they are tiny and can fit within say a 50 cm cube (which is the diameter of curiosity's wheel) the mass of each machine will also be radically less. Curiosity weighs 899 KG, a well designed vehicle base could weigh as less as 1 KG with instrumentation we could work with the assumption of 2 KG. That is around 450 rovers! If they are divided into teams of say 6 and are dropped off using some method at discrete intervals then you have 75 teams exploring the martian surface. If each team explores during just the warm martian months (I'm working with assumption of 400 sols) with a rate of a very conservative .5 m^2 explored in a day then all of the teams combined will explore 15000 m^2 in the course of a single mission. That's huge. Further, in this scenario, if individual units fail at some point then the entire mission won't be jeopardised and that number will roughly stay the same. I think that if the units are allowed to be autonomous (again because they are disposable) then you could rapidly increase the area explored and get more out of a single mission. In this scenario the success of the mission has now bifurcated from the functioning of a single device and because of that you are free to pursue several orthogonal benefits such as these which ultimately reduce costs. I think that if you factor in a decrease of launch costs due to company's like SpaceX, then this ought to become even more attractive. natep linked to a wonderful article ( http://www.dau.mil/pubscats/ATL%20Docs/Mar-Apr10/ward_mar-apr10.pdf http://www.dau.mil/pubscats/ATL%20Docs/Mar-Apr10/ward_mar-ap... ) on this which argues the point in a much better way. >>> The solar concentration of a Martian winter is extremely low, and this problem is exasperated the smaller the probe and the resulting battery that it can carry. <<< One of the main uses of the battery during winter months is to keep the processor warm. If the assembly is small enough then you should be able to use just insulation, a very small heater and perhaps a long lasting exothermic reaction which proceeds slowly over time. The amount of heat generated by such a reaction would be too small for something like curiosity, but perhaps it might work for a very small machine? Again since tolerances are low you shouldn't you be able to use a wider variety of batteries which store more per unit volume? I might be wrong on all counts, but a smaller design and lowered tolerances might actually work to our advantage. >>> Just like in computing and electronics, physical and mechanical distributed systems are inherently complex - more so than monolithic systems. <<< I'm actually not that into computing and electronics, I used to build physical systems and how they fail fascinates me. My designs failed so often upon meeting the real world that I realised the only way to know if something would ever work was to actually implement it IRL. If you can carry out a mission at one-tenth of the cost then you can do that much more willingly and learn from unforeseeable failure modes much more quickly. It should be an answer to this problem than the other way around.
- natep 14y ago
  "I don't see any reason why someone shouldn't make this." You are exactly the kind of person that should build your own lander if you don't see this. And please, stop asking all of these questions in bad faith. I applaud deeringc for engaging with your specific points, but I can't bring myself to do this, since it seems to me like you assume all aerospace engineers are uncreative drones that can't think outside the box and see the obvious solution you've reached from your armchair. Have you ever built a multiply-redundant, space-worthy, swarm-based system before? Have you built something that's any one of those three? If not, I don't have a problem with you thinking about them, but I do have a problem with your attitude. Edit: to clarify, I mean the attitude that comes across from your writing style. I have no idea what your qualificaitons are, how much thought you've put into this, how receptive you are to the idea that you're wrong, whether or not you recognize that everyone has more "unknown unkowns" than anything else, or what your actual attitude is. All I have are the words you write here. And my natural response to snark is more snark. And if you think you're the first person to think "wouldn't it be great if not every spacecraft didn't have to have to re-solve the problem of power, communications, and computation?" I first heard the idea proposed in a 2009 talk[1] by someone who has been an insider for over 20 years. Some gems I remember from that talk: * Having an identical copy is not redundancy * Complexity is inherently more succeptable to failures * Cars have been widely successful because of gas stations and repair shops. Spacecraft have to drag around their own * We could create a ring of satellites, each dedicated to providing comms to earth, wireless power, computing power, or whatever. Users of the system would just need to build a structure, interfacing components, and their instrument and launch it into a nearby orbit. [1] Abstract: http://www.spacecraftresearch.com/files/Fleeter.pdf http://www.spacecraftresearch.com/files/Fleeter.pdf
  - todayiamme 14y ago
    > You are exactly the kind of person that should build your own lander if you don't see this. Once I have the financial resources, I actually plan to do so. > Have you built something that's any one of those three? To answer that yes I have, which is a completely orthogonal fact to my original comment because I am advocating reducing the qualifications of "space-worthiness" through the use of multiple copies. After reading your comment I decided that there had to be some respectable source who had advocated this earlier at some point and with some research I found this paper written by Rodney Brooks called Fast, Cheap and Out of Control : A robot invasion of the solar system outlining the same concept; http://people.csail.mit.edu/brooks/papers/fast-cheap.pdf http://people.csail.mit.edu/brooks/papers/fast-cheap.pdf > I mean the attitude that comes across from your writing style. Yes, I agree that my comments could look snarky under the weight of your assumptions, but I was doing my best to be genuine and engage in an honest discussion > I have no idea what your qualificaitons are, how much thought you've put into this, how receptive you are to the idea that you're wrong I'm actually quite certain that I'm wrong most of the times, but I don't know how I'm wrong and discussing, building things are the only ways to find out. > whether or not you recognize that everyone has more "unknown unkowns" than anything else Yes I do and it is a terrifying thought. > or what your actual attitude is. I'm doing my best to learn as much as I can and to never judge. (judgement takes up too many mental resources) > And if you think you're the first person to think "wouldn't it be great if not every spacecraft didn't have to have to re-solve the problem of power, communications, and computation?" I'm not and I would love to do more than just think and actually build things. > * Having an identical copy is not redundancy Can you please explain why? Is it because the failure points remain the same?

todayiamme 14y ago

Again do we need all of those systems? Why can't you have two dedicated machines for earth communication and the rest communicate via a HF radio protocol? You don't need a RTG if it's say sojourner size and packs one payload on a standardised mobile base, solar panels will work just fine. Since you have redundancy built into the swarm you can skimp on a lot of things including computing power. Remember you can use group decision making for more complex "choices" and if you lose a few drones due to unforeseen obstacles, then objectively it shouldn't matter, so you don't need a lot of LIDAR and stuff as well. As far as heating and shielding goes then the smaller size actually works to your advantage. I don't see any reason why someone shouldn't make this. Yes these probes will be disposable, but that's the entire point. They can be used and thrown away opening doors to risk taking that we haven't really seen before.

deeringc 14y ago
> Again do we need all of those systems? Yes. Like I've said above the explicit purpose of this mission is to gather advanced scientific data which requires comparatively bulky instruments and high power availability. Because it is so ridiculously expensive to get anything to Mars you want it to last as long as possible. "Disposable drones" make absolutely no sense when it costs so much to launch them into orbit, transport them 60 million km across the solar system, and then enter the Martian atmosphere and land in a coordinated place on the surface. Each gram you get to that point costs many thousand dollars. You don't just plan your strategy around losing a bunch of them - that would be many hundreds of millions of dollars down the drain. Using a decaying nuclear isotope to power your probe you will get many multiples more bang for buck compared to solar powered probes which so far have maxed out at about 5 years. The solar concentration of a Martian winter is extremely low, and this problem is exasperated the smaller the probe and the resulting battery that it can carry. Just like in computing and electronics, physical and mechanical distributed systems are inherently complex - more so than monolithic systems.
- todayiamme 14y ago
  >>> Yes. Like I've said above the explicit purpose of this mission is to gather advanced scientific data which requires comparatively bulky instruments and high power availability. Because it is so ridiculously expensive to get anything to Mars you want it to last as long as possible. "Disposable drones" make absolutely no sense when it costs so much to launch them into orbit, transport them 60 million km across the solar system, and then enter the Martian atmosphere and land in a coordinated place on the surface. Each gram you get to that point costs many thousand dollars. You don't just plan your strategy around losing a bunch of them - that would be many hundreds of millions of dollars down the drain. <<< I've thought about what you have said and I think that we are measuring the likelihood of success in different ways. I'm measuring it in terms of the likelihood one pair of devices will complete the outcome at the cost of all the others and, if I am correct, at some level you are measuring it in terms of reducing the possibility of a loss while achieving the mission objectives. I think that we can afford to build disposable machines because if they are tiny and can fit within say a 50 cm cube (which is the diameter of curiosity's wheel) the mass of each machine will also be radically less. Curiosity weighs 899 KG, a well designed vehicle base could weigh as less as 1 KG with instrumentation we could work with the assumption of 2 KG. That is around 450 rovers! If they are divided into teams of say 6 and are dropped off using some method at discrete intervals then you have 75 teams exploring the martian surface. If each team explores during just the warm martian months (I'm working with assumption of 400 sols) with a rate of a very conservative .5 m^2 explored in a day then all of the teams combined will explore 15000 m^2 in the course of a single mission. That's huge. Further, in this scenario, if individual units fail at some point then the entire mission won't be jeopardised and that number will roughly stay the same. I think that if the units are allowed to be autonomous (again because they are disposable) then you could rapidly increase the area explored and get more out of a single mission. In this scenario the success of the mission has now bifurcated from the functioning of a single device and because of that you are free to pursue several orthogonal benefits such as these which ultimately reduce costs. I think that if you factor in a decrease of launch costs due to company's like SpaceX, then this ought to become even more attractive. natep linked to a wonderful article ( http://www.dau.mil/pubscats/ATL%20Docs/Mar-Apr10/ward_mar-apr10.pdf http://www.dau.mil/pubscats/ATL%20Docs/Mar-Apr10/ward_mar-ap... ) on this which argues the point in a much better way. >>> The solar concentration of a Martian winter is extremely low, and this problem is exasperated the smaller the probe and the resulting battery that it can carry. <<< One of the main uses of the battery during winter months is to keep the processor warm. If the assembly is small enough then you should be able to use just insulation, a very small heater and perhaps a long lasting exothermic reaction which proceeds slowly over time. The amount of heat generated by such a reaction would be too small for something like curiosity, but perhaps it might work for a very small machine? Again since tolerances are low you shouldn't you be able to use a wider variety of batteries which store more per unit volume? I might be wrong on all counts, but a smaller design and lowered tolerances might actually work to our advantage. >>> Just like in computing and electronics, physical and mechanical distributed systems are inherently complex - more so than monolithic systems. <<< I'm actually not that into computing and electronics, I used to build physical systems and how they fail fascinates me. My designs failed so often upon meeting the real world that I realised the only way to know if something would ever work was to actually implement it IRL. If you can carry out a mission at one-tenth of the cost then you can do that much more willingly and learn from unforeseeable failure modes much more quickly. It should be an answer to this problem than the other way around.
natep 14y ago
"I don't see any reason why someone shouldn't make this." You are exactly the kind of person that should build your own lander if you don't see this. And please, stop asking all of these questions in bad faith. I applaud deeringc for engaging with your specific points, but I can't bring myself to do this, since it seems to me like you assume all aerospace engineers are uncreative drones that can't think outside the box and see the obvious solution you've reached from your armchair. Have you ever built a multiply-redundant, space-worthy, swarm-based system before? Have you built something that's any one of those three? If not, I don't have a problem with you thinking about them, but I do have a problem with your attitude. Edit: to clarify, I mean the attitude that comes across from your writing style. I have no idea what your qualificaitons are, how much thought you've put into this, how receptive you are to the idea that you're wrong, whether or not you recognize that everyone has more "unknown unkowns" than anything else, or what your actual attitude is. All I have are the words you write here. And my natural response to snark is more snark. And if you think you're the first person to think "wouldn't it be great if not every spacecraft didn't have to have to re-solve the problem of power, communications, and computation?" I first heard the idea proposed in a 2009 talk[1] by someone who has been an insider for over 20 years. Some gems I remember from that talk: * Having an identical copy is not redundancy * Complexity is inherently more succeptable to failures * Cars have been widely successful because of gas stations and repair shops. Spacecraft have to drag around their own * We could create a ring of satellites, each dedicated to providing comms to earth, wireless power, computing power, or whatever. Users of the system would just need to build a structure, interfacing components, and their instrument and launch it into a nearby orbit. [1] Abstract: http://www.spacecraftresearch.com/files/Fleeter.pdf http://www.spacecraftresearch.com/files/Fleeter.pdf
- todayiamme 14y ago
  > You are exactly the kind of person that should build your own lander if you don't see this. Once I have the financial resources, I actually plan to do so. > Have you built something that's any one of those three? To answer that yes I have, which is a completely orthogonal fact to my original comment because I am advocating reducing the qualifications of "space-worthiness" through the use of multiple copies. After reading your comment I decided that there had to be some respectable source who had advocated this earlier at some point and with some research I found this paper written by Rodney Brooks called Fast, Cheap and Out of Control : A robot invasion of the solar system outlining the same concept; http://people.csail.mit.edu/brooks/papers/fast-cheap.pdf http://people.csail.mit.edu/brooks/papers/fast-cheap.pdf > I mean the attitude that comes across from your writing style. Yes, I agree that my comments could look snarky under the weight of your assumptions, but I was doing my best to be genuine and engage in an honest discussion > I have no idea what your qualificaitons are, how much thought you've put into this, how receptive you are to the idea that you're wrong I'm actually quite certain that I'm wrong most of the times, but I don't know how I'm wrong and discussing, building things are the only ways to find out. > whether or not you recognize that everyone has more "unknown unkowns" than anything else Yes I do and it is a terrifying thought. > or what your actual attitude is. I'm doing my best to learn as much as I can and to never judge. (judgement takes up too many mental resources) > And if you think you're the first person to think "wouldn't it be great if not every spacecraft didn't have to have to re-solve the problem of power, communications, and computation?" I'm not and I would love to do more than just think and actually build things. > * Having an identical copy is not redundancy Can you please explain why? Is it because the failure points remain the same?