Google the N.O.T.S. system from the late 50's, all solid air launched system weighted 900kg + aircraft, payload 1kghttp://www.astronautix.com/lvs/propilot.htm
This is the basic issue, what are the benefits of "constellations of nanosats" to the warfighter. There is very little a constellations of nanosats can do for a warfighter aside from comm. and there are many other spacecraft than can do that.Optics are too small for reconnAperture too small and orbit too low for sigint.
Comms might be reason enough. It's not just a question of whether you have comms, but how much you have. When every soldier, vehicle, drone, and camera has realtime video, the bandwidth requirements would be mindnumbing.
Quote from: IsaacKuo on 08/17/2010 08:49 pmComms might be reason enough. It's not just a question of whether you have comms, but how much you have. When every soldier, vehicle, drone, and camera has realtime video, the bandwidth requirements would be mindnumbing.And nanosats aren't going to be able to help. They are low power, low bandwith. Also how many nanosats would be required for a constellation? Probably too many to use this method of launch.
1)Nanosats could be used for safely deorbiting other sats. The military might find this useful after the situation involving the deorbit of USA193.
At 10 kg (estimated) the Kestrel Eye reconnaissance satellite may just fit on a MNMS launch vehicle.Fact sheethttp://www.smdc.army.mil/FactSheets/KestrelEye.pdf
Quote from: A_M_Swallow on 08/19/2010 05:29 amAt 10 kg (estimated) the Kestrel Eye reconnaissance satellite may just fit on a MNMS launch vehicle.Fact sheethttp://www.smdc.army.mil/FactSheets/KestrelEye.pdfThere are some basic holes. How many spacecraft will it take to be "on demand"? Tdon't know the answer but it will be too many to be launched by MNWSWhat if there is multiple users wanting to task a satellite?How does one know when a satellite is available?Small spacecraft aren't going to have the power and bandwith to push the data to the user.The 10 minute cycle is too fast for the spacecraft to react.
I think multiple users is a non issue... It is a matter of juggling priorities.I also feel if you are taking single snapshots you you are not going to be running into much of a bandwidth issue. Especially if it is transmitting directly to the ground station.
Could it be used suborbitally for single-shot surveillance? Just a thought.
Quote from: Robotbeat on 08/19/2010 05:30 pmCould it be used suborbitally for single-shot surveillance? Just a thought.Spensive...
{snip}At a reasonable altitude, that should be able to get you something that has a decent view on a pretty frequent basis. Nowhere near as good as the AF birds when they're actually overhead, but having 30-72 satellites in the constellation means you're a lot more likely to get intelligence on demand a lot better.
Quote from: jongoff on 08/19/2010 02:15 pm{snip}At a reasonable altitude, that should be able to get you something that has a decent view on a pretty frequent basis. Nowhere near as good as the AF birds when they're actually overhead, but having 30-72 satellites in the constellation means you're a lot more likely to get intelligence on demand a lot better. The bane of the small observing satellite is:+ Aperture size+ Pointing ability+ Data rate (really rate is limited by available xmit power/antenna gain)Ideally you have all three, though by definition a small satellite cannot have a large aperture. To make up for the limited space for optics require extreme pointing capabilities, which generally isn't available in a small sat.The optics are generally why optical observation birds are the size that they are.
Quote from: jimvela on 08/19/2010 07:09 pmQuote from: jongoff on 08/19/2010 02:15 pm{snip}At a reasonable altitude, that should be able to get you something that has a decent view on a pretty frequent basis. Nowhere near as good as the AF birds when they're actually overhead, but having 30-72 satellites in the constellation means you're a lot more likely to get intelligence on demand a lot better. The bane of the small observing satellite is:+ Aperture size+ Pointing ability+ Data rate (really rate is limited by available xmit power/antenna gain)Ideally you have all three, though by definition a small satellite cannot have a large aperture. To make up for the limited space for optics require extreme pointing capabilities, which generally isn't available in a small sat.The optics are generally why optical observation birds are the size that they are.So, for something like the KestrelEye, do you think they're being overoptimistic in their spec sheet (I think they claimed 1.5m resolution), or just leaving out details? You're definitely in a better position to know on things like this than most.~Jon
resolution=1.22*(altitude)*(wavelength)/(aperture diameter)They mention 10 inches as roughly the aperture diameter, which is about .25 m, and for a minimum altitude of 200km (2E5m) and a wavelength of about 500nm (5E-7m) , we should get a diffraction limit of about:1.22*2E5m*5E-7m/.25m=1.22*.1m/.25=.488m
Quote from: Robotbeat on 08/20/2010 04:19 pmresolution=1.22*(altitude)*(wavelength)/(aperture diameter)They mention 10 inches as roughly the aperture diameter, which is about .25 m, and for a minimum altitude of 200km (2E5m) and a wavelength of about 500nm (5E-7m) , we should get a diffraction limit of about:1.22*2E5m*5E-7m/.25m=1.22*.1m/.25=.488mPure angular resolution isn't the only factor that defines system resolution. Using only angular resolution implies that your detector is an array of points, which is never the case.Typical detectors are CCDs, and the size and sensitivity of the individual pixels are a major contributor to the overall system capability. Most of the detectors used for this type of application have surprisingly large pixels, and surprisingly long integration times.
You also start to be limited by things like geolocation accuracy and repeatability when you start talking about responsive (near real time) tasking. If you can image 1Kmx1Km at .4M resolution, but can only geolocate and point with 12Km accuracy, then you could end up shooting useless targets and/or not know exactly where you imaged.
Pure angular resolution isn't the only factor that defines system resolution. Using only angular resolution implies that your detector is an array of points, which is never the case.Typical detectors are CCDs, and the size and sensitivity of the individual pixels are a major contributor to the overall system capability. Most of the detectors used for this type of application have surprisingly large pixels, and surprisingly long integration times.You also start to be limited by things like geolocation accuracy and repeatability when you start talking about responsive (near real time) tasking. If you can image 1Kmx1Km at .4M resolution, but can only geolocate and point with 12Km accuracy, then you could end up shooting useless targets and/or not know exactly where you imaged.
I imagine this is well off into the realm of science fiction at this stage, but maybe you could have cloud of small sensors that could function as an interferometer. Quite a few challenges but possible in principle. Then you could get fantastic resolution and the system would be insensitive largely to the loss of a few components.
1. Geolocation is an interesting issue, and one that I'd solve with a combination of cheap MEMS accelerometers (again, cell-phone tech) for pointing and 2. real-time updates on the orbit from Space Command for position. There are probably other ways too, but the trick is remembering that computing is cheap and light, while specialty sensors (e.g. startrackers) are heavy and complex.Communications is probably through a mesh network, like many ground-based sensor nets. Specifically, you'd have one or two sats imaging at a time, and the rest acting as relays to a ground station or geosync com sat...
-the Army doesn't build space systems, doesn't really have the expertise, and always faces the risk of the Air Force stomping on their programs and getting them shut down. -the goal seems pretty ill-defined. What exactly is this going to do? Why is that necessary? And is there reason to believe that it can be done better with a space system than with terrestrial systems? Or by other similar existing space systems? And that also touches on issues of turf. Before the US Army starts operating its own reconnaissance satellites, they will have to talk to the guys at the National Reconnaissance Office, who will fight them tooth and nail unless they are convinced that this new approach is a) necessary, b) a good idea, c) won't undercut existing NRO programs, and d) is better done by the Army than the NRO.
I believe that this is where the Falcon 1 entered the picture, with an original launch cost of around $5 million apiece. (Anybody know what the list price is for a Falcon 1 now?)
If a foe sets off an EMP, or otherwise removes the majority of US satellites from usefulness, you can bet that the army would rather have a bunch little crappy cameras with them in the field,
Quote from: go2mars on 08/26/2010 08:53 pmIf a foe sets off an EMP, or otherwise removes the majority of US satellites from usefulness, you can bet that the army would rather have a bunch little crappy cameras with them in the field,And those in the field would not be able to find the targets because a. GPS would be knocked oub. Comsats would be too
I imagine that the army would be interested in having a few backup batches of GPS (even if relatively crude) and comm sats available for those reasons. If most of your bombs and UAVs suddenly become useless, you're kind of screwed, aren't you? t.
Quote from: Robotbeat on 08/26/2010 09:19 pmI imagine that the army would be interested in having a few backup batches of GPS (even if relatively crude) and comm sats available for those reasons. If most of your bombs and UAVs suddenly become useless, you're kind of screwed, aren't you? t.This can't replace comsats and GPS spacecraft
I realize that, but they could replace something like the ORBCOMM network (~40kg microsats), and the satellite phone LEO constellations are able to do crude positioning within a few kilometers, though obviously that precision leaves much to be desired.
This can't replace comsats and GPS spacecraft
Wow, kilometer accuracy.Look, this is not a replacement for GPS. And it's not a replacement for traditional comm. The key question is what is it good for?
1-If a foe sets off an EMP, or otherwise removes the majority of US satellites from usefulness, you can bet that the army would rather have a bunch little crappy cameras with them in the field, ready for quick-launch than nothing at all. Plus at 10 kg, they would be smaller targets if it was ground based ASAT. If the satellites are taken out/blinded by other little enemy satellites (rumoured to exist), then you might be able to have more cameras to launch than they have of little predator satellites. 2-It also could be used to test technologies for small hypersonic ground-ground or ground-air missiles (scram/ram).
Quote from: Blackstar on 08/26/2010 04:44 pm I believe that this is where the Falcon 1 entered the picture, with an original launch cost of around $5 million apiece. (Anybody know what the list price is for a Falcon 1 now?)Falcon 1 is a lot bigger/less transportable. It costs $10.9 million for 1010 kg. This other system is talking about ~10 kg. One needs liquid oxygen, the other just needs ethane and nitrous oxide. Far different uses/mobility levels.
Quote from: go2mars on 08/26/2010 08:53 pm If the satellites are taken out/blinded by other little enemy satellites (rumoured to exist), then you might be able to have more cameras to launch than they have of little predator satellites. 1-If a foe "removes the majority of US satellites from usefulness," then we won't need an army. Any foe capable of doing this would have to be pretty damned capable. After all, the US military currently has over 100 operational satellites in orbit. That's a lot of stuff to take out.As for EMP? An EMP is a nuke. If a foe uses a nuke, do you think we are going to need that army? Do you think that a foe would use the nuke for an EMP and then not nuke the army? (Do you think a foe would waste a nuke on an EMP unless they had a lot of them?)And note that although the individual satellites might be simpler, if you put a whole bunch of them into space, you've created a complex constellation that has to be controlled and used effectively. How do you do that against a foe that has an EMP?
If the satellites are taken out/blinded by other little enemy satellites (rumoured to exist), then you might be able to have more cameras to launch than they have of little predator satellites.
Quote from: Jim on 08/26/2010 09:56 pmThis can't replace comsats and GPS spacecraftIt's worth repeating (I'm sure Jim knows this, so I'm repeating this for everybody else): GPS is the size it is because they couldn't make it any smaller. They've tried. The equipment, the altitude and power requirements, all drive it to the size that it's at....
Quote from: go2mars on 08/26/2010 08:53 pmQuote from: Blackstar on 08/26/2010 04:44 pm I believe that this is where the Falcon 1 entered the picture, with an original launch cost of around $5 million apiece. (Anybody know what the list price is for a Falcon 1 now?)Falcon 1 is a lot bigger/less transportable. It costs $10.9 million for 1010 kg. This other system is talking about ~10 kg. One needs liquid oxygen, the other just needs ethane and nitrous oxide. Far different uses/mobility levels.You've missed my point here. I was not trying to compare Falcon 1 to this other system. I was pointing out that ORS, and Falcon 1, were touted as wonder systems that would do many of the same things that people here are saying that this new technology will do. And they did not do that. Falcon 1 did not achieve its cost goals. My point is that if you're going to try and predict what will happen here, then the ORS experience is a good guide--it promised a lot, did not deliver, and now is either in a state of limbo, or even decline (when measured against the original promise).I'm not opposed to small satellites. But small inevitably means less capable. You have to ask if those lower capabilities are still worth the cost. ORS has been going for almost a decade now and still has not demonstrated that to such an extent that they've convinced a lot of people. You can manufacture a better dog food, but the proof is if the dogs come running to eat it.
Why would the Army be in charge of this system? I thought the USAF was in charge of SLV's and ballistic missiles. The army currently is only tasked with air defense (ie Patriots) and attack munitions (MLRS)
