Don’t ask me why I need to know this. Just assume I’ve made a theoretical breakthrough with my managing editor and we need the data fast.
What sort of force would be required to accelerate a mass of 1000 tons (2000 lbs for the metrically inclined) to C?
Assuming, as I know it is, that actually accelerating to C is impossible. How close could we get?
Should we be able to do so how long would it take us to get to Alpha Centauri using our mythical drive?
What speed would we be moving when we needed to start decelerating on the way? And how much force would that require?
My managing editor, who is an idiot and reading over my shoulder, wants to know whether intergalactic conquest is in his future and what plans he should make for his future?
How many G’s could a cherry 1971 Dodge Charger withstand? He says it’s the only thing he loves and wants to take with him.
What do you mean by “what sort of force”? How much energy perfectly applied? What could be done to do it? Theoretically we can use basic rocketry with enough fuel or
We can get arbitrarily close to C. Any velocity less than C can be done in theory.
At C? Alpha Centauri is 4.37 light years, so it would take 4.37 years at the speed of light. The closer you get to the speed of light the closer to that number it would be. Of course, don’t forget about stopping once you get there.
Unanswerable question. Not enough information. But possibly halfway, if we accelerate evenly across the entire distance.
You can let him know that our fleet of intergalatic rats will be approaching Earth in apporixmately 17.9 standard solar years. We can accept surrenders from any earth nation in advance if they desire to negotiate early. I can accept negiated payments and/or bribes in Dollars, Euros, Pounds, Yen, Whiskey, Berklium, or Tritium, and of course the cheese beloved by our new rodent masters. Standard galatic currencies and will be accepted in the new regime, but the primitive Earth economy can’t yet handle Ghedenian Karn or Aeljos Ignis.
:dubious: Uh, yeah. Tell him it can handle 7.38 G’s, but only if it’s braced by a BTU mark 12.6 vector-specific concussive absorbing material. I just made that up, but he doesn’t need to know that.
You can get arbitrarily close to C.
Assuming we are in the vacuum of space and the only force operating in the one the mythical drive then any continuously applied force will increase your speed forever. The rate of increase of your speed will go down the faster you are going. Until we nail down how much force is applied and if it varies we cannot answer any of the other questions.
This calculator will help with some of your questions. The Mopar, unfortunately, will be toast above 5 gs or so (unless it’s a momentary exposure to those forces).
You might be able to gleen a few more answers from this thread.
As close as you please/as much as your amount of energy will allow, you just can’t actually reach C.
From the point of view of an observer on Earth your trip will take aprox 4.3 years. From YOUR reference frame the trip will appear to be considerably shorter, depending on just how close to C you get.
2-4: These questions are all interdependent, though if your speed is limited to slightly less than **c[b/], the fastest you will get there is about 4.3 years. The amount of force depends on your rate of acceleration, and your rate of acceleration depends upon how much force you can apply. For most real world propulsion problems we tend to look more at impulse than acceleration, mostly because it integrates nicely.
5: Don’t bet the farm on intergalactic conquest. Commercial strip mall investment may be prosaic, but it’s also profitable.
6: Not enough. It depends on how you restrain it and what kind of sleeper shoring you use, but most structures in roadable vehicles are built to withstand only low frequency accelerations in the 2-3 G range, as more than this will start breaking parts off of the passengers. If you submerge the car in pressurized Jello and keep the impulse rate from being too intense you can probably get about an order of magnitude more capability from it (although you’ll probably break anything glass just from stress redistribution) but it’ll be an awful mess at the other end, plus they probably don’t have Chevron stations on Alpha Centuri’s hypothetical life-supporting planet.
Assuming Newtonian physics, it would take about a year to accelerate to C at an acceleration of 1 G, and another year to brake to a stop. The distance covered would be approximately a light year. So a trip to Alpha Centauri is going to take more than 5 years. Since you can’t actually travel that fast, it will take a bit longer, depending on how much energy you are willing to expend.
The “2000 pounds” thing was to make sure were wouldn’t be using metric tons. Not that it would be the entire weight.
Tom, the Managing Editor from Hell (and mopar enthusiast), has provided further clarification.
He chose the 1000 ton figure as a figure approximately half the weight of the space shuttle (don’t ask me why).
Assume the sort of acceleration that the shuttle could produce. But also assume an infinite fuel supply.
He’s not into strip malls. He’s assuming conquest because of his incredibly cool car. Admittedly, from the response I see, if the opposing alien army is composed of mid-20s college girls he’s going to win because of the car. It’s just that powerful.
Sub-question: Assume THE CAR (as it’s called) can hit more than 140 (it has, resulting in both a spectacular display of speed and one HELL of a speeding ticket). How long THEN would it take him to drive, assuming interstellar charger capability, to get to Alpha Centauri?
Note, also that we’re here working at 8:45PM putting the issue together. Tom, indeed, may have snapped.
I’m getting a total trip length (earth frame) of 5+ years, onboard your ship only 2.3 years will have passed with a mximum velocity of .98 c @ an accelleration rate of 2 G’s.
Some quick back of the envelope calculations (well, sticky note and Google calculator calculations) using straight Newtonian physics, I come up with a total energy expenditure of 7.3510396 x 10[sup]17[/sup] MJ. Assumptions are 1000 tons (of the 2000 lb. variety), accelerating at a continuous 2g’s and neglecting piddling things, like getting out of the Earth’s gravity well.
Now, I understand that a 1971 Dodge Charger doesn’t give a rat’s ass about some metric MegaJoule crap, so I did a little further calculation. Let’s assume that Gary T. and Rick were called in and tuned your boss’s car to within a gnat’s whisker of it’s life, so that it could use 100% of the energy in a gallon of gas. If we then hooked your boss’s penis compensator up to a 998 ton Space Winnebago (to carry all of the underage teenage girls who were impressed by the car and will be of legal age by the time they arrive [warning: summers there are brutal and the shopping pretty much sucks]), you would need a shade over 5.6 quadrillion (5.61148061 x 10[sup]15[/sup]) gallons of gasoline for a one-way trip. And at $3.75 a gallon (yeah, it’s going to need premium), you’re probably going to max out the Citgo card.
So Rhubarb for those calculations did you assume that the 5.6 quadrillion gallons of gas plus the oxygen to burn it had to be transported on the rocket also? Or did you assume the gas and reaction mass magically appear as needed on the Charger?
Note that 2 years and 4 months at 2 G will make you a lot older than you would have been if you’d stayed home and spent the 5 years frolicking and etc.
I’d recommend 1 G acceleration and the heck with the extra transit time.
Now if you’re hoping to drive from here to there, at 140 MPH, that’ll take longer.
1 light year = 5,878,499,810,000 miles (if I’ve got my zeros right). Call it 17 million years at 140 MPH–if you don’t have to stop for gas, sleep, repairs, etc.
Pshaw, those are just details. I couldn’t decide whether to put a Niven-style transfer booth in the gas tank, or to transport the gasoline to a microwave laser cannon in heliosynchronous orbit and beam the power to the Charger.
For the purposes of this exercise, I just modeled the whole thing on an infinitely long treadmill. Jonathan, 140 mph is a velocity, not an acceleration. It’s okay to assume infinite gas tanks and Space Mopars, but let’s keep the physics real, okay?
Let’s take The Car and attach it to a bank of Big Ass Ion Thrusters with a specific impulse of 9000s[sup]1[/sup] in an orbital dock. We hang a pair of solar sails off the passenger doors to provide electrical power, and fill up the 998-ton-capacity fuel tank packed with solid Xenon. The fuel tank is made from drop-forged Handwavium and has no mass but nearly infinite strength and stiffness, and also has great heat shield properties. Your boss, the intrepid pilot, has planned ahead and shaped the fuel tank to double as a reentry vehicle once he reaches the nearest habitable planet[sup]2[/sup], eliminating the need to start braking so early.
Ion engines are highly efficient but very low thrust, so we’re also going to strap on a pair of Space Shuttle Solid Rocket Boosters, axially aligned with your center of gravity. This will quickly get you up to a pitifully irrelevant speed and start your trip with a thrill, at which point the ion engines can slooooowly accelerate you for the rest of the trip. Your total starting mass is really close to 2 million kilograms, but don’t sweat it - you’ll be losing mass real quick. A quick check of the owner’s manual reveals that you will be getting 12.5 mega-Newtons of thrust per booster, or thereabouts, for the first 124 seconds, at an efficiency of 269 seconds. Once you ditch the SRB you’ll weigh the previously-stated 1000 tons, and you’ll be moving at about 2,000 meters per second[sup]3[/sup].
Now we engage the Ion Engines. The mass flow rate is ludicrously low; with only one thruster your 998 tons of Xenon will last you 3.7 millenia. I called for a bank of Big Ass Ion Thrusters above, so we’ll make it a bank of 5,000 engines and you only need to spend 276 days accelerating. (We ignore the fact that strapping them together in parallel is not going to generate ideal thrust.) As you consume and expel fuel the unholy chariot you have assembled will become easier and easier for the engines to accelerate, resulting in more zoom-zoom. Assuming relativistic effects haven’t kicked in by that point, you could conceivably reach a speed of 0.15% of the speed of light, meaning it would take you only about 2400 years from that point to coast to Alpha Proxima.
Reverse-engineering the problem, you could probably choose a number of engines that would generate two g’s at startup (probably on the order of 2 million of the little buggers) and then start turning them off throughout flight, slowing your fuel consumption but leaving your acceleration constant. You’d start out ejecting 15 kg/s of xenon, leaving you with only 16 hours of thrust at your starting rate… but by selectively shutting down engines until you get to 26,000 (bare minimum) you could extend your fuel time to many days and still maintain 2g’s of acceleration. Haven’t figured out what your top speed would be, because I’m up too late.
We do this because it’s much more fuel efficient than the Space Shuttle Main Engine, and there’s no gas stations between here and there. Also I’ve had a hard-on for ion engines since the first time a TIE fighter swooped across my line of sight in a cinema.
Something orbiting Alpha Proxima, hopefully. Otherwise you show up to the Proxima system and everyone’s already gone to the dance and you can’t get a ride and now Becky will never think you’re cool.
I’m worried about bolting on more than two of these things, because it would mean that near the end you’d get some pretty wicked peak acceleration. Given Stranger’s advice earlier, I’ve probably already trashed The Car.
