8900 - 21/12/2007 3:34 AMQuotekhallow - 21/12/2007 6:21 PM[8] Expendable rocketProbably the best choice in today's economic climate. I just don't see a more reliable solution replacing expendables until launch volume goes up substantially.please note that it's a prediction by 2100, not current situation It seems unlikely that the launch demand will be the same 100 years later
khallow - 21/12/2007 6:21 PM[8] Expendable rocketProbably the best choice in today's economic climate. I just don't see a more reliable solution replacing expendables until launch volume goes up substantially.
MTKeshe - 26/12/2007 11:19 PMThe prototype system producing gravitational field force is shown in this linkhttp://www.keshetechnologies.com/keshe_gravity.htmlThe system is exactly half sphere.Through tests with full sphere prototypes. http://www.keshetechnologies.com/dynamic_reactors.html
Frediiiie - 29/12/2007 10:37 AM"go to www.emdrive.comthis is the most promising tech i've seen in years. It obeys all laws of physics, is funded by the US government and there is a video of a demonstrator that is shown to work."The wikipedia article explains the basic problemhttp://en.wikipedia.org/wiki/EmDrivephysics as currently understood does not allow violation of mass conservation or energy conservation.If someone wants to claim that (like emdrive) then there is a whopping great burden of proof on them.
tnphysics - 29/12/2007 6:52 AMThe EmDrive is nonsense. It violates momentum conservation. Hence it is impossible.
My favorite future propulsion technology is NTR, either the nuclear lightbulb type or a fusion type if that is possible. It is the only high-thrust, high-Isp propulsion candidate out there.
Not enough to reach LEO. Once in space-yes, but VERY slow. Same uses as ion drive, but limited to ionosphere.
Quote from: tnphysics on 05/02/2010 03:25 amNot enough to reach LEO. Once in space-yes, but VERY slow. Same uses as ion drive, but limited to ionosphere.It's a given that rockets will be needed to reach LEO in the foreseeable future. No one can predict the usefulness of a propulsion system that to them is only theoretical. While electrodynamic propulsion is theoretically possible, there is no generally accepted method of achieving it. A tether that is several km. long and that conducts tens or hundreds of Amps. could produce a very large force by acting against the Earth's magnetic field. A different method may similarly produce large forces outside of the ionosphere. It is not impossible.
Quotetnphysics - 29/12/2007 6:52 AMThe EmDrive is nonsense. It violates momentum conservation. Hence it is impossible.If I understand the concept, it uses the entire rest of the universe as a reaction mass. In other words accelerates but pushing the rest of the universe in the opposite direction. That would not violate conservation of momentum. QuoteMy favorite future propulsion technology is NTR, either the nuclear lightbulb type or a fusion type if that is possible. It is the only high-thrust, high-Isp propulsion candidate out there.That said, I agree that the nuclear lightbulb type or fusion probably the best possibility out there. That's like saying unobtanium is needed given today's economy isn't it?Now while it may be technically true that NTR is the only high thrust high Isp propulsion; Solar thermal has higher Isp than solid core NTR and can acheive as much as .1 gee. By using a series of thrusts at perigee, an STR can still take advantage of the Oberth effect especially if lower Isp used for final thrust by increasing H2 mass flow rate. Overall the efficiency can come very close to NTR for something like Mars with only a week or two more time getting away from Earth. I was once told that the problem with STR tech was that it was too inexpensive. The use of advanced concentrators can greatly increase STR performance. By using a tech I call inflation insitu-form with deradable elements, I believe concentrators with specific power in excess of 100KW/kg could be formed. These concentrators would inflate to shape once on orbit and UV would degrade some parts and harden others to form a mirror with holes smaller than visible light wavelengths. Such concentrators would be able to exceed the thrust of solid core NTR at higher Isp and much lower cost. The concentrator can also be used for concentrator type PV which has efficiencies approaching 40% at around 1 KW/kg. It can also be used for high baud communications, radio telescope, ISRU solar furnace and other applications.Sol
Well, I'm looking at the Air Launched Sortie Vehicle concept that the USAF had been considering in the early 1980's. It uses an FDL-7 type spaceplane with the rocket engines on it and some fuel supply, with an underbelly drop tank, all mounted to the dorsal side of a large transport plane like a 747 that would have its engines modified to have afterburners on them.Once I get a concept modelled in 3d I'll post some pics.
Quote from: GreenGlow on 05/02/2010 08:24 pmQuote from: tnphysics on 05/02/2010 03:25 amNot enough to reach LEO. Once in space-yes, but VERY slow. Same uses as ion drive, but limited to ionosphere.It's a given that rockets will be needed to reach LEO in the foreseeable future. ... Electrodynamic tethers can actually be used for getting to LEO.The hanging type ED tether can start with a tether only a few km long and grow to one thousands of miles long as more tether modules are added. ...Sol
Quote from: tnphysics on 05/02/2010 03:25 amNot enough to reach LEO. Once in space-yes, but VERY slow. Same uses as ion drive, but limited to ionosphere.It's a given that rockets will be needed to reach LEO in the foreseeable future. ...