magestorm Posted February 22, 2006 Share Posted February 22, 2006 Where did you get those figures? I seen the escape velocities for many planets, and that's way wrong for earth. Besides, we are not talking the escape velocity to full space, just to LEO range. This is about 8km/sec, or 22,400km/hr. Not exactly the best speed, being aproximately Mach 22. However, by accelerating a mass to around mach 5 or so WOULD make it so the transport would require a lot less energy. And if you say bull on that, then why did the Ansasi X prize winner use a similar concept? True, you had a plane carry the ship to a high altitude and speed, but this could easily be replaced with a launching sled on a supersonic or even hypersonic transport. And since the shuttle reenters at mach 26, it is possible to reach these speeds without going crazy. Also, constructing this at a higher altitude than sea level would in effect reduce the speed needed to escape. If a sled were launched from Denver, its altitude would cause the needed delta v to be reduced to 7km/sec, instead of 8km/sec. Please also note that one could even use the slingshot effect of earth's natural rotation at the equator. Because of the rotation, one can reduce the needed delta v by another 1km/sec. So a mountain range at least 1km up, and at the equator would equal a needed speed of Mach 19. Sources for figures: www.nasa.gov Link to comment Share on other sites More sharing options...
TetsuoShima Posted February 22, 2006 Share Posted February 22, 2006 Where did you get those figures? I seen the escape velocities for many planets' date=' and that's way wrong for earth.[/quote'] My figures where not exact, I'll give you that, but they certainly were not wrong, I said over 40000 km/h and that is a completely correct statement. In fact YOUR conclusions are wrong AND you don't decently check what I say... Besides' date=' we are not talking the escape velocity to full space, just to LEO range. This is about 8km/sec, or 22,400km/hr. Not exactly the best speed, being aproximately Mach 22. However, by accelerating a mass to around mach 5 or so WOULD make it so the transport would require a lot less energy.[/quote'] Okay and you accuse me of not having correct figures??? :stare: You'd better check yours, especially when you've got one misinterpretted and one incorrectly calcutated... In fact, that 8 km/s (or 28800 km/h, even though it is closer to 27500 km/h due to rounding, but certainly not 22400 km/h which is closer to 6 km/s) is the speed at which sattelites generally travel in low earth orbit, it is not the same as the speed necessary to get them there! In fact, to get them there with a powered shuttle, you need about 35000 km/h, however, since what you're proposing is using, shal we call it a shotgun, to get there, in which case you need far greater starting velocity, in fact upon further investigation it seems that my previous quick calculation was not just a little low but very much low, so much even so that you still need over 200000 km/h to get in LEO riding the shotgun, in fact, the numbers for LEO and GEO differ, but not 'that' much simply because the force Earth exerts on objects is higher, the closer they are and since the density of the air is highest closer to the Earth. You are right that you don't need full escape velocity, but LEO is absolutely not the best place to start a construction yard or a relay station, it would be like creating a constrution site in the middle of the highway, best to take that stuff higher up. It would take more enrgy to take it there straight away, but it would also have some serious advantages (like not being in the way of all other satelites and not needing a transfer station, I don't know what is more efficient (take the LEO or not), I don't have enough data to calculate that) And if you say bull on that' date=' then why did the Ansasi X prize winner use a similar concept? True, you had a plane carry the ship to a high altitude and speed, but this could easily be replaced with a launching sled on a supersonic or even hypersonic transport.[/quote'] Sure and why not use transporter and do away with current technology altogether... :p As for the Ansasi X prize, I have to apologise, I've never heard of it... And since the shuttle reenters at mach 26' date=' it is possible to reach these speeds without going crazy. Also, constructing this at a higher altitude than sea level would in effect reduce the speed needed to escape. If a sled were launched from Denver, its altitude would cause the needed delta v to be reduced to 7km/sec, instead of 8km/sec.[/quote'] You keep forgetting that little thing called air friction, very convenient, especially when you consider you don't have an engine and multple force trying to stop you from reaching your destination, why not for get a few, and in this case (since you have no engine) the most important one. Please also note that one could even use the slingshot effect of earth's natural rotation at the equator. Because of the rotation' date=' one can reduce the needed delta v by another 1km/sec. So a mountain range at least 1km up, and at the equator would equal a needed speed of Mach 19.[/quote'] Yes, and then you have all this help and you still have to beat (I'm not in the mood to take out my calculator again) more than 150000 km/h (friction is very important at high speeds, double the speed, quadruple the friction force, so you can imagine how I get these huge numbers) I don't know what the future holds, but I can tell you that this 'railgun' is not going to be for the next 10-20 years. After that, who know... Link to comment Share on other sites More sharing options...
Tenebrae Posted February 22, 2006 Share Posted February 22, 2006 Pray tell magestorm, where did I say nay - I said it would present some technical issues. That means higher cost and longer before it could be introduced. Let's just say I'd feel confident saying I won't be going to sample moon cheese via railgun before my 40th birthday. Link to comment Share on other sites More sharing options...
magestorm Posted February 22, 2006 Share Posted February 22, 2006 What rock have you been living under? It has been all over the news, and due to the winner expanding on the science, they are building a commercial model of the winner, and starting a launch facility right in the heart of New Mexico. However, that is neither here nor there. The issue is that you are looking at the trees, instead of the forest. You say it is going to take years to build. And the problem is???????? Besides, if there is that big of an issue, reduce, reuse, recycle. Use a railgun to propel a ship to mach 5-8, then fire the ship's engines at the right moment. Yes, you'd still need engines. But, the ammount of fuel needed would be a LOT less than in conventional rocketry, as 80% of fuel burned is in the first minute of liftoff. This is because the ship has to start from a dead stop. Then, it has to push enough to get going. Not just the ship, but the massive fuel tanks as well. This means that you're carrying more fuel than would be required if the ship was already in motion. However, 40000km/hr is way too much delta v to reach escape velocity. That's more than enough to breach the solar system. You'd only need about 2/3 of that at most to reach escape velocity into a stable orbit. Link to comment Share on other sites More sharing options...
TetsuoShima Posted February 23, 2006 Share Posted February 23, 2006 What rock have you been living under? It has been all over the news, and due to the winner expanding on the science, they are building a commercial model of the winner, and starting a launch facility right in the heart of New Mexico. However, that is neither here nor there. The issue is that you are looking at the trees, instead of the forest. You say it is going to take years to build. And the problem is???????? Besides, if there is that big of an issue, reduce, reuse, recycle. Use a railgun to propel a ship to mach 5-8, then fire the ship's engines at the right moment. Yes, you'd still need engines. But, the ammount of fuel needed would be a LOT less than in conventional rocketry, as 80% of fuel burned is in the first minute of liftoff. This is because the ship has to start from a dead stop. Then, it has to push enough to get going. Not just the ship, but the massive fuel tanks as well. This means that you're carrying more fuel than would be required if the ship was already in motion. That's true, but it also depends on the efficiency of the 'rail gun' in comparison to ordinary rocket engines. If they can make them equally efficient in energy usage, then you'd have allready the advantage of the lower weight as you mentioned, if they can increase the efficiency, well then it would be even better. Taken into account that you'd be sending a ship up with a 'rail gun' and engines, that would indeed mean that you're starting speed could be a lot lower (than the 150000 I previously mentioned), since both friction and the fact that you'd be carrying an engine that could be ignited at the right time, possibly even immediately after takeoff, it would take some calculation to see what would be the optimal points, but having an engine onboard changes things a lot. Depending on the amount of kinetic energy you give the vessel at start and how much you still plan on giving it while it's underway, the needed initial speed can be anything between 0 km/h (no help from 'rail gun') to over 150000 km/h (no engines). The most efficient initial velocity can no doubt be decently calculated if you have enough information... The only 'real' problem I can see, is that to make it as profitable and efficient as possible, it would have to be a non-manned vessel (especially if you take into account the enormous electromagnetics fields that will be involved in the launch). But even that is not a 'real' problem... Since you could have 'ordinary' spacecraft to get crew up there and with a spacestation up there, that would not have to be very frequent. However, 40000km/hr is way too much delta v to reach escape velocity. That's more than enough to breach the solar system. You'd only need about 2/3 of that at most to reach escape velocity into a stable orbit. Okay, let me write it down for you, because I really am correct about the escape speed of Earth being geater than 40000 km/h. formula to calculate: v = (2*g*r)^0.5 with g = the acceleration of gravity at the Earth's surface ~ 9.8 m/s² and r = the Earth's radius ~ 6.4E6 m you get v ~ 11200 m/s = 11.2 km/s = 40320 km/h if you take into account my approximations of g and r, you get an acceptable approximation of the escape velocity of Earth meaning: 11E3 m/s = 11 km/s = 40E3 km/h, because there are only 2 digits in the approximate numbers. Now, that wasn't to hard and apart from the approximation of g and r the calculation 100% mathematically correct. I could write down how I got to that original formula, but since I can't input integrals on this board, that is kind of hard, suffice to say it is deduced from the fact that the weight of an object of mass m at the surface is g*m and the weight of this object at height s above the center of the Earth is g*m*(r/s)². This means that the energy needed to lift this object from height s above the Earth's center to height s + ds, is g*m*(r/s)² *ds. You can then integrate this between r and infinity to calculate the total energy needed to lift the object to infinite height. Then you can take the obtained value and since it is equal to the amount of kinetic energy the object needs in order to escape, you can deduce the given formula for escape velocity. You can easily use this same method to calculate the initial speed needed to reach a certain height without engines. This method however is only correct in an atmosphere-free environment, since friction will make for the largest part of initial speed needed once you take it into consideration. Even at LEO there is a 'decent' amount of friction. And you need to take into account that this speed is only in the z-axis, so when you reach speed 0 (in other words, the height you aimed for), you fall straight back down, to overcome this, you need to also have the correct speed (to maintain a certain orbit) at a different angle and this means that the actual speed has to be greater then the speed calculated by the above method if you plan on actually staying up there. However, the size of this vector is nearly negligable (depending on how accurate it needs to be) in comparison to the speed that needs to be added due to friction. btw, to reach escape velocity for this solar system (from Earth's position), you need a speed of over 156000 km/h, but if you play your cards right and launch something relative to the Earth in the direction of the Earth's orbital motion, this number gets a lot less: about 49000 km/h. I cannot tell just like that if it would be better or worse to sent it all up to LEO or MEO or GO (HEO doesn't seem like a good idea imo), but I'd guess they'd be better off putting a 'reception station' in a higher orbit than LEO. In any case, given time, money and resourcefulness, it could be a good idea to implement it as a means of giving vessels ' a kick in the butt' on lift-off, but as a sole means of transportation (without engines), it is virtually useless imo. With engines and the right 'balance' however, it would definately be an improvement over current ways. *edited typo* Link to comment Share on other sites More sharing options...
Beawulf Posted February 23, 2006 Author Share Posted February 23, 2006 Interesting stuff. Incidentally the speed required to start a scramjet engine is about mach 5, so a railgun style launching system is probably the most suitable for this task. However the scramjet has limited use as it requires atmosphere to function. The highest speed a scramjet has reached is just shy of mach 10, they believe it can reach mach 15. Still not enough to maintain a circular orbit (7.9km/s or mach 23.8) but could still be used to get the craft to a considerable height. Since it uses the atmosphere to obtain the oxygen, the weight of fuel carried is considerably lower, making it feasible to use in conjunction with another engine. speaking of fuel and SpaceshipOne (winner of the ansari x prize), did you know it runs on rubber and nitrous oxide? I found this quite interesting considering those two components are inert. I'd love to see some technical details on the engines, but I imagine that is a closely gaurded secret (being a business venture) Anyone got more information on that? edit: was just reading more about the scramjet to see what the maximum altitude it can function at is... (still looking) and read that the projected maximum speed is actually up to mach 25 which would be sufficient to get the job done. I also read that the engine functions better higher in the atmosphere than where it is denser. another edit: apparently Virgin Galactic is calling SpaceShipTwo, the VSS Enterprise and the next one the VSS Voyager WOOHOO! hehe :D Link to comment Share on other sites More sharing options...
magestorm Posted February 23, 2006 Share Posted February 23, 2006 Your figures make for some wonderful fiction there, but they simply are not true. For one, you are again calculating escape velocity to break totally away from Earth's orbit, not entering into orbit. You also are not taking into consideration that you are calculating from sea level, not from an altitude. A for effort, but an F in making simple mistakes. Link to comment Share on other sites More sharing options...
Beawulf Posted February 23, 2006 Author Share Posted February 23, 2006 geez, this is meant to be a lighthearted discussion of our visions for the future. lighten up. Link to comment Share on other sites More sharing options...
TetsuoShima Posted February 24, 2006 Share Posted February 24, 2006 Your figures make for some wonderful fiction there, but they simply are not true. For one, you are again calculating escape velocity to break totally away from Earth's orbit, not entering into orbit. You also are not taking into consideration that you are calculating from sea level, not from an altitude. A for effort, but an F in making simple mistakes. I think you simply either didn't read it properly enough or didn't understand it thouroughly enough. lol :D Anyway, if you arguement better wat part you fail to understand, preferably with your own interpretation and calculations besides them, I can maybe make you understand where your error lies. :D Link to comment Share on other sites More sharing options...
Tigerplayer Posted February 27, 2006 Share Posted February 27, 2006 IMO spaceships and stations alike, will need lots of emergency systems, even vessels as small as virgins SS1 will at least need an emergency pod with the shielding needed for reentry, parachutes and/or rocket engines, considering that there is no air in space. Space stations used for civillians will need to be stuffed with escape pods, auxilliary backup systems etc. They will need even more safety than those today (ISS?). Some things that should be considered with the escape pods: 1) They will either not need to be controlled or be controlled by a computer, so that the people inside the pods do not have to wait for a crewmember to control the pod. 2) They need to have compliment for at least one or two families or more. 3) general rules for the station itself. Eg. no more civillians aboard than the pods can handle, minus the pods needed for the crew 4) they need a small case or package with food and first aid kits, in case somebody is wounded. 5) the pod's systems are checked at least daily Link to comment Share on other sites More sharing options...
magestorm Posted February 27, 2006 Share Posted February 27, 2006 I agree. multiple redundancies should be a mandatory thing, along with enough escape pods to cover 1.5 times the capacity of the ship or station. However, once multiple stations are in orbit, you won't need to have reentry pods for stations. All one would need is just to get to the next closest station. This could even be automated. Link to comment Share on other sites More sharing options...
Tigerplayer Posted May 26, 2006 Share Posted May 26, 2006 magestorm.... you are quite incorrect. What if there was a high amount of solar wind activity? Solar winds are known to have fried the systems in sattellites, if one space station is exposed to the solar winds, it is in great danger of having all its systems fried or at least damaged, even if there are many stations, this is too great a risk. The pods can be programmed to send a distress signal to all nearby stations. Only if an affirmative answer is given to the pod it will fly to the station, but if a negative signal (in case of an emergency on that station as well) is sent to the pod, then it still needs to be suitable for reentry, even if this scenario is unlikely. When designing space station emergency systems, you will still need to take the most unlikely scenarios into account. In periods of high solar wind activity, noone should be on the station except for an extremely small skeleton crew no more than three or four persons, just to be safe. Especially because the solar winds can knock out quite a few systems including those for life support. Even if the station is filled to the brim with countermeasures and backup systems it is still too dangerous, especially now and the near future where Earth's magnetic field is starting to flip over. The magnetic field is what keeps the solar winds away from us and our technology. The solar wind is kinda like an EMP bomb when hitting a piece of machinery. Every chip and other component is going to get fried because of the high amount of energy transported with it Link to comment Share on other sites More sharing options...
SCOLancer Posted May 30, 2006 Share Posted May 30, 2006 Why not just use mag levs like the japs have in their new trains or some of the new rollorcoasters thats seems a good idea even for the lift into orbit Link to comment Share on other sites More sharing options...
VonHelton Posted June 3, 2006 Share Posted June 3, 2006 are there any resources on the moon? Helium 3 is on the Moon. This can be used as fuel for spaceships! B) Link to comment Share on other sites More sharing options...
Tigerplayer Posted June 11, 2006 Share Posted June 11, 2006 are there any resources on the moon? Helium 3 is on the Moon. This can be used as fuel for spaceships! B) not only Helium-3 is on the moon, also a number of minerals that are quite rare here on earth can be found up there. Not only can it be used for spaceships, but also to start a fusion reactor :D Link to comment Share on other sites More sharing options...
bones2097 Posted June 22, 2006 Share Posted June 22, 2006 yeh lets start minning the moon,,, reduce its mass & gravity & then it would really become moon base alpha!! :) Link to comment Share on other sites More sharing options...
Tenebrae Posted June 22, 2006 Share Posted June 22, 2006 I actually read up about Helium-3 the other day. It's not really going to do anyone any use for a while. At the moment we can't even get regular fusion to a break-even point, the fusing point of Helium-3 is actually substantially higher than regular helium... so, even once we get fusion working - it'll be a while before he3 can be used in the process efficiently. Link to comment Share on other sites More sharing options...
Antipodean Posted June 22, 2006 Share Posted June 22, 2006 yeh lets start minning the moon,,, reduce its mass & gravity & then it would really become moon base alpha!! Umm - wouldn't that bugger up the tides & cause a global environmental disaster... And isn't the very orbit of the moon contingent on the moons mass - a lighter moon would propbably swing off on its own trajectory... as the gravitational attraction between 2 bodies is contingent upon their mass? something like that? Link to comment Share on other sites More sharing options...
Tenebrae Posted June 22, 2006 Share Posted June 22, 2006 You'd be messing with a lot of stuff. Presumably, most of that mass from the moon is going to head to the Earth? Of course, I think it would take a great deal of time for a significant enough amount of mass to be exchanged between the Earth and the Moon to actually make any change. Link to comment Share on other sites More sharing options...
Arktis Posted June 22, 2006 Share Posted June 22, 2006 Oxygen is especially abundant making up around 50% of the moon' date=' obviously this isnt the form of a gas but is bonded with other minerals (sillicone, aluminium, titanium, iron, magnesium, calcium, sodium) infact almost everything is bonded with oxygen. [/quote'] oxygen is the most abundant element in the earth. theres bloody tonnes of it! No way, dude. Hydrogen. It's the simplest and most abundant element. Oxygen is actually the second most abundant element on earth. And yeah, mining the moon is just stupid because in the long term, you're most certainly going to end up screwing up the earth's tides. Link to comment Share on other sites More sharing options...
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