1 W/1 N would be quite a space-drive. But to do useful propulsion it just has to beat the competition. Consider VASIMR - at full throttle the drive gets 1 N/125 kW. And that's just jet-power, the actual electrical efficiency is worse. If the MLT can get 1 N/kW and keep that up for weeks, then it'll be pure "Buck Rogers" between here and Mars.
Am I wrong in the impression that that would imply minimally-scaled (IOW cheap) probes to many different targets for the price of and in a fraction of the travel time of a single mission today? That the more advanced stages of MLT tech (e.g. those needed for SSTO payloads and manned missions) wouldn't be required to push such small probes?
Quote from: Cinder on 09/26/2009 10:30 amAm I wrong in the impression that that would imply minimally-scaled (IOW cheap) probes to many different targets for the price of and in a fraction of the travel time of a single mission today? That the more advanced stages of MLT tech (e.g. those needed for SSTO payloads and manned missions) wouldn't be required to push such small probes?Cinder:You are on the right trail. Any propulsion technology that can provide an order of magnitude improvement in performance in one or more important performance parameters like specific power (Watts/kg), specific thrust AKA Specific Impulse Isp (seconds) or my thrust to power figure of merit Newtons per Watt is a paradigm changer. Right now the best energy limited ion or plasma rocket engine like VASIMR can provide 1 N/40 kW input power with an Isp of ~5,000 seconds. If we can build reliable and long-lived M-E drives that produce 1.0 N per 4.0 kW we have a game changer for robotic solar system space drives. If we can build an M-E drive that can produce that 1.0 N for only 400W of input power, that means we can now produce 10,000 Newtons (2,258 lb-f) for 4.0 Mega-Watts. That’s not quite a one gee space drive that could lift your Toyota Corolla off the ground, but when tied to a Lerner 5.0 MW Dense Plasma Fusion (DPF) reactor, we are getting very close to same. And finally with three orders of magnitude improvement in the M-E drives, we would only need 40 watts to produce that 1.0 Newton of force, so the total power required to lift the Corolla off the ground is now on the order of 500 kW which means that a DPF reactor tied to four 10,000 Newton M-E drives would be one hell of a hot rod that could produce 4 gees of acceleration all the way to Mars and back!
NOTE: 75 horsepower = 100 kW. Thus a 500 kW car engine is 375 hp, which is pretty typical for your top of the line sports cars.
I suspect, when working ME thrusters are developed, the efficiency will vary based on the direction of thrust.Let me explain what I'm talking about.There is a certain amount of energy associated with an object in orbit. I do not believe that a ME will be capable of pushing an object on the ground into orbit using less energy than is associated with the energy of that orbit.Therefore, although a ME thruster may have some non local characteristics, it will most likely have some local characteristics depending on the gravitational potential well it is operating in.Just a gut feeling with nothing behind it, other than the feeling that conservation of energy must hold even for a ME thruster.
There is a certain amount of energy associated with an object in orbit. I do not believe that a ME will be capable of pushing an object on the ground into orbit using less energy than is associated with the energy of that orbit.
The locality of conservation laws is the basis of modern physics.
Quote from: mlorrey on 09/27/2009 01:23 amNOTE: 75 horsepower = 100 kW. Thus a 500 kW car engine is 375 hp, which is pretty typical for your top of the line sports cars. au contraire, but 1 metric hp = 75 kgf.m/s (735.5 W) and an old-school horse-power is 550 ft.lb/s (745.7 W.) Thus 75 hp isn't 100 kW, but just 55.164 kW. That's still pretty respectable. I have heard of a car with 750 hp under the hood. Of course what actually is converted into power on the road is substantially less due to thermodynamic & drive-train inefficiencies. Better efficiencies are possible, but for rather different engine configurations.
You know, these conversion factors don't really matter when we're nonchalantly throwing out improvements of three orders of magnitude.
Quote from: Robotbeat on 09/28/2009 06:27 pmYou know, these conversion factors don't really matter when we're nonchalantly throwing out improvements of three orders of magnitude.
Quote from: Star-Drive on 09/29/2009 03:21 amQuote from: Robotbeat on 09/28/2009 06:27 pmYou know, these conversion factors don't really matter when we're nonchalantly throwing out improvements of three orders of magnitude.Isn't it 4 orders of magnitude over what has been demonstrated?And that actually puts it currently into the "less technically certain than the space elevator" column, as that only requires a 2 order of magnitude improvement in demonstrated materiel properties like tensile strength.Anyway, it does seem kind of premature to assume that expending lots of resources in the direction of capacitor research could necessarily produce these results.
Quote from: cuddihy on 09/30/2009 02:40 amQuote from: Star-Drive on 09/29/2009 03:21 amQuote from: Robotbeat on 09/28/2009 06:27 pmYou know, these conversion factors don't really matter when we're nonchalantly throwing out improvements of three orders of magnitude.Isn't it 4 orders of magnitude over what has been demonstrated?And that actually puts it currently into the "less technically certain than the space elevator" column, as that only requires a 2 order of magnitude improvement in demonstrated materiel properties like tensile strength.Anyway, it does seem kind of premature to assume that expending lots of resources in the direction of capacitor research could necessarily produce these results.You haven't been looking at the equations? The chief gain is not from boosting cap K, it's from increasing the frequency of the driver to above the MHz range, refining it and getting the kinks out.
Quote from: Lampyridae on 09/30/2009 04:24 amQuote from: cuddihy on 09/30/2009 02:40 amQuote from: Star-Drive on 09/29/2009 03:21 amQuote from: Robotbeat on 09/28/2009 06:27 pmYou know, these conversion factors don't really matter when we're nonchalantly throwing out improvements of three orders of magnitude.Isn't it 4 orders of magnitude over what has been demonstrated?And that actually puts it currently into the "less technically certain than the space elevator" column, as that only requires a 2 order of magnitude improvement in demonstrated materiel properties like tensile strength.Anyway, it does seem kind of premature to assume that expending lots of resources in the direction of capacitor research could necessarily produce these results.You haven't been looking at the equations? The chief gain is not from boosting cap K, it's from increasing the frequency of the driver to above the MHz range, refining it and getting the kinks out.Actually if one could come up with a dielectric with a WELL BALANCED set of cap dielectric parameters for the M-E MLTs, like a relative permittivity of ~1,000, a magnetic permeability of ~20, a well controlled piezoelectric response, a dissipation factor of less than 0.5% at 10 MHz in a dielectric that had a 1,000 hour or greater operating lifetime under full power conditions, we would be ready to start building levitating M-E test articles. As noted, nobody in the high energy cap storage business is thinking about this kind of cap parameter mix until we show them it’s worth their time and money to do so. And to do that we first have to make a convincing M-E demonstration using COTS parts and a much more optimized MLT or rotary M-E drive design and that will just take a lot of time (years) using our existing resources.