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# Tag Info

80

Nonrelativistic solution The variables used will be $x$ for the distance travelled $v$ for velocity $a$ for acceleration ($1~\mathrm{g}$) $t$ for the time $c$ for the speed of light. Non braking Assuming the velocity you arrive at does not matter we take the equation $$x = \frac12 a t^2\ .$$ Solve for $t$: $$t = \sqrt{\frac{2x}{a}}\ .$$ (Let’s ...

42

Velocity relative to what? There's no central universal point to measure velocity at, so your answer is likely going to change based on your frame of reference. New Horizons did indeed have the fasted launch velocity of any spacecraft that has left Earth (relative to Earth): After three years of construction, and several delays at the launch site, New ...

38

Spooky This one is subjective. To some, just finding an abandoned spaceship would be spooky. I'll say there's probably not a lot that has to happen to evoke this feeling. Rusted Actually, unless your spaceship never had a breathable atmosphere or the atmosphere was vented before the spaceship was abandoned, rust is totally possible on the inside and ...

38

It is not only how fast the airfoil has to travel, but also how large the airfoil must be to even have fluid-dynamics-like behavior. Because of the low density of particles in the interstellar medium, a normal-sized wing will not act as an airfoil. It will be more like bouncing tennis balls off the wing every so often. The Knudsen number quantifies when ...

32

Voyagers are still active, and albeit they don't have the power required to run all the scientific equipment onboard and some of it stopped working by now, they still transmit telemetry data streams towards the Earth that is picked up by NASA JPL's 70-meter antenna at Goldstone, California, part of the Deep Space Network. Quoting from Wikipedia on Voyager ...

28

Caves Any large body where you can survive on the surface to begin with can be used for caves, artificial or natural. This observation isn't off-topic because you ask about holding in atmospheric pressure. Moon caves can hold 1 atmosphere of pressure about 60 meters below the surface with no stresses on the surrounding rock. I'm using very simple math ...

25

Why the Pioneers didn't last as long: The Pioneers were a low-budget mission just to test if flying to the outer planets was feasible They used a smaller radio transmitter (8 W vs. 23 W) and antenna (2.7 vs 3.6 m diameter) so their signals are weaker The Pioneers used a smaller, earlier design Radioisotope thermoelectric generator as their power source (...

22

The most fuel efficient way to leave the solar system at present, is to launch into a trajectory that (like that used for Gallileo) may well involve one or several gravity assists from Earth or Venus, but which eventually gets you to Jupiter. If you can get to Jupiter you can almost certainly do so in such a way as get a slingshot into a solar escape ...

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Original Answer Given Alcubierre's math, and White's calculations, it's a viable avenue of research to pursue. Whether or not it is practical as FTL, and given the expected maximum apparent speed of about 10 times the speed of light (White), and that the math says it should be able to be done, an attempt to implement a prototype series should be of immense ...

21

The speed of the probe doesn't change with regard to the assisting body. It is direction that is changed. If a hyperbolic orbit about the sun comes in with a Vinfinity of 5 km/s, it will exit with a Vinfinity of 5 km/s. Unless it happens to swing by a planet. From the planet's point of view incoming and outgoing speed are also the same. Again, it's ...

21

The expression $v_e = \sqrt{\frac{2Vq}{m}}$ is a non-relativistic approximation. This is quite valid when the exhaust velocity is small compared to the speed of light, which is the case for ion thrusters made to date (exhaust velocity is on the order of $10^{-4}c$). A more precise expression is $${v_e}^2\left(1+\frac{2Vq}{mc^2}\right) = \frac{2Vq}m$$ No ...

20

The fastest way to leave the Solar System is to pass by as many of the Gas Giants as you can, and use their gravity to slingshot you faster. As there are no planets outside of the ecliptic, it would not be advantageous to avoid the ecliptic plane. This holds true until we start to get really fast space probes. Furthermore, passing by the planets would give ...

19

Zero. Voyager 1 has left the solar system, and is therefore an interstellar spacecraft. I'm not sure what qualifies a ship, but there is no reason why it would take any humans. Nor do yachts (or cars) need humans for navigation, for that matter. Interstellar space is particularly dull. You'll be travelling for many years with absolutely nothing ...

19

The core of your question is about real, "normal" engine exhaust velocities. The fastest we get so far from practical, in-production engines is about 4,440 m/s, Space Shuttle main engines with liquid oxygen and liquid hydrogen as propellants, producing water as the exhaust product (https://en.wikipedia.org/wiki/Specific_impulse). That speed is limited by the ...

18

We currently cannot track Pioneer 10 or 11. Someone on the XKCD forum calculated how much radiation the Voyager probes emit besides their radio transmissions. The heat they give off is emitted as infrared light: We have a power source of 420 W at 1.78×1010 km, which gives a brightness of 1×10-19 Wm-2, or an apparent magnitude of 28. That is just ...

18

It's theoretically possible to collect fuel from near empty space, the bussard ramjet is an example of an engine built to do just that. The principle is that you use magnetic fields to collect and concentrate hydrogen atoms from the near vacuum of space, and then a fusion rocket would turn some of this into propulsion for speed and a fusion reactor would ...

17

No. What a gravity assist does is change the velocity with respect to other objects, but not the one you were approaching. Nasa provided a nice diagram to assist with understanding this. In fact, in more ordinary terms, it could be though of as the below diagram shows. The baseball is thrown at the train at 30 miles per hour. From the view point of the ...

17

There are two major reasons you may be going outside the ecliptical plane: You want to get to a particular star. You want to put the Sun on a direct line between your craft and another point in the sky (usually a star system or an interstellar probe to that star system) to exploit Sun's gravitational lens (that is, your destination starts around 550-740 AU ...

16

In addition to what John provided, it's also worth noting that given the scale of tens of thousands of years, the stars will actually move. This is clearly shown in a Wikipedia article. As can be show, Alpha Centauri will only be 3 Light Years away in about 30,000 years. Okay, so the fastest mission I've heard of using nearly obtainable technology is the ...

16

You are forgetting Pioneer 10, Pioneer 11, and New Horizons. Pioneers 10 and 11 respectively operated for 28 years and 16 years after completing their primary missions. New Horizons, which has yet to perform its primary mission (Pluto flyby in July 2015) or secondary mission (TBD flyby of a Kuiper belt object) will reach the heliopause in about 2047. No ...

16

The total antimatter in the van Allen belts is estimated to be 160 nanograms. Annihilating that with matter would produce a whopping 8 kW-hr of energy. A quarter of a gallon of gasoline has that much energy. The star ship would be better off getting a quick spurt from a gas station pump before heading out.

16

No, the power collected by solar panels is reduced by the square of the distance from the light source. At the Earth's distance from the sun, the energy of sunlight is about 1300 watts per square meter, of which something like ~30% can be converted to electricity by solar panels. Once the sun is far enough away to be "just another star", the total ...

15

It's partly the same issues as the launch problem. If you put more fuel in the fuel tanks of the rockets, you then increase the mass. Then to lift that fuel you need to add a bit more fuel to lift that fuel, and so on and so forth. A similar problem exists with the current propulsion system on probes but before I go into that I'm going to (very briefly) ...

15

This is a repository community-wiki post with references to current work on Alcubierre drive at NASA (Harold White) and in other places. Harold White. Warp Field Mechanics 101 (2011). http://hdl.handle.net/2060/20110015936 Harold White. Warp Field Mechanics 102 Energy Optimization (2013). http://hdl.handle.net/2060/20130011213 (See also YouTube videos: http:...

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No, as far as I can tell NASA got it right. Voyager 1 isn't going fast enough to reach AC +79 3888's current position in 40,000 years -- but the star is coming to meet it. Assuming the current speed is 17 km/sec (as stated in the first paragraph if this Wikipedia article, and that it won't slow down much beyond that, it should cover approximately 1 light-...

15

There are incredible, mindboggling distances involved in merely reaching an exoplanet. Alpha Centauri Bb, the closest known exoplanet, is 4.365 light years away. That's 41,295,000,000,000 km (25,660,000,000,000 mi), or 276,000 AU (the distance from the Earth to the Sun). Voyager 1 has left most of our solar system behind and is traveling a blistering 17.3 ...

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Currently functional and proven technology is limited to basically no interstellar travel at all. To reach one of our stellar neighbors (like Proxima Centauri), one of the fastest space probes we have now, New Horizons, would take 54000 years. There are multiple proposed methods of sending spacecraft interstellar distances (in shorter time spans) such as: ...

14

Hefty gravity wells can give a healthy Oberth benefit. Doing a burn deep in Neptune's well makes sense. Suggesting an Oberth maneuver near a Pluto sized object is pretty silly. Don't know if Randall Munroe knows this. Maybe that's part of his joke. Heading all the way back from the Kuiper belt to the inner solar system take 30 years. Then back out another ...

14

There is an answer on wikipedia: Rogue planet: It is calculated that, for an Earth-sized object at a kilobar hydrogen atmospheric pressures in which a convective gas adiabat has formed, geothermal energy from residual core radioisotope decay will be sufficient to heat the surface to temperatures above the melting point of water.[13] Thus, it is proposed ...

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