Rakaydos Posted July 31, 2015 Share Posted July 31, 2015 The question is, if the device is losing mass (detectable or not, at the moment), would it make for a viable method of propulsion anyway?Depends on the ISP... Link to comment Share on other sites More sharing options...
Streetwind Posted July 31, 2015 Share Posted July 31, 2015 In that scenario, there would be an Isp figure dependant on the amount of mass the drive ablates per time, and a total amount of mass the drive can ablate before becoming inert - which, when combined with payload, would define the total amount of dV it can put out. Wheher or not it would be a viable method of propulsion would depend on that dV figure. If its thrust per power invested is a little higher than current-gen electric drives, then it would have to be able to put out ~5 km/s dV with payload in order to be viable. That would prescribe either tiny payloads, or an unrealistically high Isp.In short, I don't think it would be viable. Link to comment Share on other sites More sharing options...
K^2 Posted July 31, 2015 Share Posted July 31, 2015 (edited) Given power/thrust ratio, the current upper bound on ISP is 0.45c/g. Or about 30,000 times that of a conventional rocket. Talking about it being "not viable" is silly.Now, this would require 100% energy efficiency. That's not likely. Based on ion drive performances, most we could expect from an electrodynamic drive like this is 10%. That still puts us at 0.15c/g. If the EM Drive is to generate 45μN of thrust, it would require a mass flow of 1μg/s. That's tiny, but still within our capability to measure with the right setup. It's just going to be really hard to get rid of all possible sources of contamination.If EM Drive is just a new kind of ion drive, it's actually a pretty good one. We might be able to benefit from it.Edit: Fixed some math. Edited July 31, 2015 by K^2 Link to comment Share on other sites More sharing options...
Streetwind Posted July 31, 2015 Share Posted July 31, 2015 K^2, my response was to Aanker pondering a kind of drive that works by ablating itself. I make no attempt to predict or comment on the actual nature of the actual test article. Link to comment Share on other sites More sharing options...
Nuke Posted July 31, 2015 Share Posted July 31, 2015 i like to think of it as a potential cross between a hybrid rocket engine and an ion drive. or rather an ion drive running on a as of yet undetermined solid fuel. Link to comment Share on other sites More sharing options...
K^2 Posted July 31, 2015 Share Posted July 31, 2015 K^2, my response was to Aanker pondering a kind of drive that works by ablating itself.Any drive works by ablating itself. Solid boosters, quite literally. Liquid rockets in a more figurative way, but it's still the same principle. The only quetion is how good the ISP is, and if measured results are accurate, we're looking at something that's as good or better than ion drives. Link to comment Share on other sites More sharing options...
Streetwind Posted July 31, 2015 Share Posted July 31, 2015 Yeah sure, by redefining what I said into a completely different meaning that better suits your needs, all rockets are self-ablating.Sigh. I should have known better than expecting rational conversation in this thread, I really should. It's not like I haven't been here before. (This is the part where I go away for a month or two, only to come back later and post something, making the same mistake again.) Link to comment Share on other sites More sharing options...
ZetaX Posted July 31, 2015 Share Posted July 31, 2015 Yeah sure, by redefining what I said into a completely different meaning that better suits your needs, all rockets are self-ablating.I have to side with K^2 here: you are the irrational one in this case (mostly by ignoring the actual argument on a basis of "I said something different [despite it being a special case of yours/covered by you]").There essentially is no formal reason to differentiate between ablation-based and reaction mass-based rockets. They should be the same in regard to everything relevant to its job as a means of acceleration. Even more, an ablation-based engine is definitely a special case of a reaction mass one, so everything that applies to the latter automatically does so to the former. Link to comment Share on other sites More sharing options...
Sean Mirrsen Posted July 31, 2015 Share Posted July 31, 2015 (edited) Any drive works by ablating itself.Propellers don't. There essentially is no formal reason to differentiate between ablation-based and reaction mass-based rockets.To a scientist, maybe. To an engineer, an engine that ablates itself is significantly inferior to an engine that uses reaction mass, because it cannot be easily "refueled", and if the dimensions of the engine are constrained for a given optimal performance level, you have to basically carry spare engines along if you want to extend the dV reserve. Edited July 31, 2015 by Sean Mirrsen Link to comment Share on other sites More sharing options...
Aanker Posted July 31, 2015 Share Posted July 31, 2015 I guess the only major difference in principle between ablation and other reaction mass power is the method that drives the reaction mass to exhaust velocity. In f.e. a chemical rocket, it is the chemical reaction (well, I guess specifically temperature and pressure) whereas with ablation it is some direct energy source that shoots off the material (i.e. a laser or, as I merely speculated here, microwaves or some thermo-electric-magnetic interaction thingy). Link to comment Share on other sites More sharing options...
magnemoe Posted July 31, 2015 Share Posted July 31, 2015 Given power/thrust ratio, the current upper bound on ISP is 0.45c/g. Or about 30,000 times that of a conventional rocket. Talking about it being "not viable" is silly.Now, this would require 100% energy efficiency. That's not likely. Based on ion drive performances, most we could expect from an electrodynamic drive like this is 10%. That still puts us at 0.15c/g. If the EM Drive is to generate 45μN of thrust, it would require a mass flow of 1μg/s. That's tiny, but still within our capability to measure with the right setup. It's just going to be really hard to get rid of all possible sources of contamination.If EM Drive is just a new kind of ion drive, it's actually a pretty good one. We might be able to benefit from it.Edit: Fixed some math.If its an ion drive using ablating the efficiency sound surprisingly high, should be worth looking into just for this, should also be easy to significantly improve performance as the current design is accidental. However to check ablating as an source would be simple. Put an plate behind the engine connected to the engine frame and it would stop the trust from ablating or out-gassing. Link to comment Share on other sites More sharing options...
PB666 Posted July 31, 2015 Share Posted July 31, 2015 Given power/thrust ratio, the current upper bound on ISP is 0.45c/g. Or about 30,000 times that of a conventional rocket. Talking about it being "not viable" is silly.Now, this would require 100% energy efficiency. That's not likely. Based on ion drive performances, most we could expect from an electrodynamic drive like this is 10%. That still puts us at 0.15c/g. If the EM Drive is to generate 45μN of thrust, it would require a mass flow of 1μg/s. That's tiny, but still within our capability to measure with the right setup. It's just going to be really hard to get rid of all possible sources of contamination.If EM Drive is just a new kind of ion drive, it's actually a pretty good one. We might be able to benefit from it.Edit: Fixed some math.Tagging onto this, there are articles posting on this topic online claiming "Moon in 4 hours", "Mars in a month", "Pluto in 2 years". I would just like to point out that while the efficiencies might appear at present to be quite high as K2 eluded to, the absolute thrust they can generate just before their electronics goes kaput is a tiny fraction of what the Apollo command module can generate. http://www.rt.com/uk/311088-space-travel-engine-revolution/ http://www.wired.co.uk/news/archive/2015-07/24/emdrive-space-drive-pluto-missionhttp://www.wired.co.uk/news/archive/2014-07/31/nasa-validates-impossible-space-driveI should point out that the drive has not been validated until it has been tested in the vacuum of space. If it is an ablater, it means it is cannibalizing itself, this means that it would not be able to sustain acceleration and deceleration required to land on Pluto. 1. No landings on any celestial, excepting things like 67P (which ~5 m/s is escape velocity) - No moon landings, no mars landing - you still have to bring all your deceleration fuel and a thruster with you. 2. Of course all that fuel weighs, ion drives will also not help with landings. So basically it still has to carry about 60% of the mass of the vessel in fuel for landings and re-ascents.3. It still requires an internal source of power beyond the orbit of the asteroid belt, which also weighs. 4. Of course it is virtually useless until is supercedes the drag in LEO. Link to comment Share on other sites More sharing options...
Mazon Del Posted July 31, 2015 Share Posted July 31, 2015 Not quite sure what you are referring to when you are talking about the absolute thrust they can generate before the electronics die.If you are referring to the capacitors that die with pretty much every test, that is because it was decided that it was far cheaper for the current test article to just buy a box of non-vacuum rated caps and change them out every test, than it was to buy the required vacuum rated caps. Note: This behavior was already investigated and nullified as a possible source of the thrust. Link to comment Share on other sites More sharing options...
K^2 Posted July 31, 2015 Share Posted July 31, 2015 Shame. If this turned out to be an ion thruster eating cap electrolyte for propellant, it'd be kind of cool. Link to comment Share on other sites More sharing options...
Surefoot Posted July 31, 2015 Share Posted July 31, 2015 Exciting times. Funny that kind of news coincides with my watching of Steins;Gate, an SciFi anime series where a "time machine" is built out of a microwave oven.. Really looking forward to seeing larger scale, better built experiments on this principle. Link to comment Share on other sites More sharing options...
Mazon Del Posted August 6, 2015 Share Posted August 6, 2015 Another article brought to my attention. https://hacked.com/emgate-wars-continue-publication-peer-reviewed-emdrive-paper/WARNING: The article is rather clearly pro-EMDrive and so is not exactly impartial in its discussion. Also, it doesn't really add anything new.Also...it is calling the current discussion about if it works or not EMGate....so. much. hatred. Link to comment Share on other sites More sharing options...
vger Posted August 6, 2015 Share Posted August 6, 2015 Also...it is calling the current discussion about if it works or not EMGate....so. much. hatred.I hate to sound like a tyrant, if I ruled the world, but I would ban the use of "gate" as a suffix. It's REALLY getting old. Link to comment Share on other sites More sharing options...
PB666 Posted August 6, 2015 Share Posted August 6, 2015 I hate to sound like a tyrant, if I ruled the world, but I would ban the use of "gate" as a suffix. It's REALLY getting old.Sounds like you are trying to create a KSP-forumgate here. Link to comment Share on other sites More sharing options...
ZetaX Posted August 6, 2015 Share Posted August 6, 2015 I hate to sound like a tyrant, if I ruled the world, but I would ban the use of "gate" as a suffix. It's REALLY getting old.But... Stargate¿ Link to comment Share on other sites More sharing options...
Stargate525 Posted August 6, 2015 Share Posted August 6, 2015 I hate to sound like a tyrant, if I ruled the world, but I would ban the use of "gate" as a suffix. It's REALLY getting old.I just really want another conspiracy at the Watergate, so they have to call it Watergategate. Link to comment Share on other sites More sharing options...
Mazon Del Posted August 6, 2015 Share Posted August 6, 2015 I am pleased that someone with the name Stargate in their user name was the one to suggest that. Link to comment Share on other sites More sharing options...
vger Posted August 6, 2015 Share Posted August 6, 2015 Considering how many scandals happen in Hollywood every week, we actually have a LOT of "stargates" on this planet. Link to comment Share on other sites More sharing options...
ZetaX Posted August 6, 2015 Share Posted August 6, 2015 Scandal! Vega once again twinkles towards Polaris! Link to comment Share on other sites More sharing options...
vger Posted August 6, 2015 Share Posted August 6, 2015 (edited) Scandal! Vega once again twinkles towards Polaris!In other news, C.O. Momentum has pressed criminal charges against E.M. Drive. C.O. Momentum was heard to say, "I have never been so violated in my life." Edited August 6, 2015 by vger Link to comment Share on other sites More sharing options...
Rakaydos Posted August 6, 2015 Share Posted August 6, 2015 In other news, C.O. Momentum has pressed criminal charges against E.M. Drive. C.O. Momentum was heard to say, "I have never been so violated in my life."E. M. D. protests his innocence, saying the world just doesnt understand their relationship. Link to comment Share on other sites More sharing options...
Recommended Posts