47

If you don't want or can't afford ejecting matter, you are left with solar sail: since photons carry momentum, reflecting photons can allow you to harvest that momentum and use it to move. Expand reflective leaves in a suitable way, and use the light coming from the star at your advantage. Mind of two consequences: If you reflect the photons, you are not ...


19

I'll just go for the bonus points about rotation. As long as the organism can change its shape, it's perfectly possible for it to rotate freely while maintaining net zero angular momentum throughout the rotation. That is, it can rotate without expending any mass and without anything to push off of. Cats do this quite regularly in order to land on their feet, ...


13

Ion thruster. https://www.nasa.gov/centers/glenn/about/fs21grc.html Technically this is also venting matter, but "venting" to me implies large quantities. Kinetic energy = mv2. Energy increases as the square of the velocity. By ejecting small particles you minimize mass loss. By ejecting them very very fast you maximize kinetic energy. A creature in ...


9

Low energy forms of propulsion would include Yarkowsky propulsion (basically, you heat the area opposite to the direction you want to go, as much as possible) and both electrostatic and electrodynamic propulsion and attitude adjustment. Solar wind sails are another possible way. Your organism should be able to measure the electric and magnetic fields ...


7

For the sake of convenience let’s start with the assumption that your population will desire a North American urban population density and a globally averaged diet. The city of Austin TX has approximately 1,000,000 residents and a surface area of approx. 800 km^2, for a density of about 1,250/km^2. The City of New York (5 boroughs) NY also has a surface ...


7

Lasers Admittedly, they don't have to be coherent, just a directed light beam. You can gather energy from starlight and emit it opposite the direction you want to go. In principle it works just like any other drive, except, photons do not have rest mass, so you won't lose any of your precious materials in the asteroid. Yet photons still carry momentum so ...


4

Capture the solar wind and use it to power an ion drive. This will be very-low thrust, but it is feasible. Sources vary, but the density of the solar wind at Earth orbit is about 4 particles per cubic cm (electrons, protons and alpha particles). You could have the organism capture the solar wind continuously, and only use it for thrusting occasionally, ...


4

It is an interesting question. Firstly, because of the science-based tag, it is unlikely that any planetary body could rotate at anywhere near the limiting rotational velocity. Most planetoids in the solar system have a period more than about 2 hours - anything faster is generally very small (sub 1 km) although there are a few exceptions (one object 400 km ...


4

I'm calling a bit of a frame challenge with this answer. The point of Scylla and Charybdis was to create an ethical dilemma for Odysseus - the original 'rock and a hard place'. Scylla would lead to the definitive deaths of a few crew members. Charybdis, on the other hand, may lead to the deaths of everyone, or the deaths of no one. It's an interesting ...


4

Grey Goo Scylla is a disc of grey goo, multiple thousands of light years in diameter. It is the remnant of an ancient civilization, technology far more advanced than your characters possess. They can't disable it, they can't destroy it. Maybe it was created by a race that lived on your targeted spiral arm for defense. Or by their enemies as a cage. ...


3

Any answer will depend on the size of the black hole (BH) and the speed of the faster-than-light (FTL) drive. Let's start with an extreme example: a galactic mass BH and a 1,000 c FTL drive. The diameter of the BH is four light hours. The fleet of FTL vessels can travel through the BH in a wide variety of angles and directions as long as they don't go below ...


3

If Albucierre drives exist, does this imply that communications can travel no faster than the Albucierre driven vessels? Yes. But that doesn't actually mean anything. Because Alcubierre drives can travel through time. If the only technology in your setting not backed by modern hard science is the Alcubierre drive, then there is no other technology in your ...


3

Not necessarily. The Alcubierre metric merely describes a space-time that is compressed in front of your spacecraft and expanded behind it. The assumption has always been that the warp field comes from the craft inside the bubble, but this isn't required to be the case. An interesting thing about the Alcubierre metric is that it looks almost identical to the ...


3

I found information in this article helpful to the question presented. The Solar Wind Power Satellite as an Alternative to a Traditional Dyson Sphere and Its Implications for remote Detection. And while this answer does not focus on if a Dyson harrop satalite could generate the kinds of power reported, this answer addresses two potential issues with the ...


2

Disclaimer: I am completely disregarding time and space dilation in this post because those only start to make a difference for napkin calculations when you really approach light speed, and I am dealing with fractions of up to 2% of it. Some pedant calculations would move the travel times a few fractions of a second up or down at most. I feel that is ...


2

It depends on whether you're willing to go into the realm of sci-fi, or you want to stay with the pure unadulterated science. If you want something realistic, then the best options were already mentioned previously by people here: solar sail, photon or, ion drives(they use thrust, but minimize matter used). However, if you're willing to go for something ...


2

Your being could utilize the Interplanetary Transport Network (ITN), which is a collection of gravitationally determined pathways through the Solar System that utilize low-energy transfer to minimize fuel use. Low-energy transfer trajectories are paths in space where orbit around one mass is exchanged for orbit around another at points in spacetime where ...


2

There are two general requirements - power and space. Power 1,000,000 humans need about 2,000 calories per day each plus energy for day-to-day functions. Total up the calories and convert it to something workable, and we have a total of 96.85 MW. That is a lot, but that pales in comparison to energy. The average US household uses 900 kWH per month, giving ...


1

As long as you have warp bubbles allowing you to go through event horizon, you can plausibly have them protect you from all possible time dilatation effects (if they don't, you are opening quite a can of worms: you might even end up time travelling to the past when moving faster than light). If the technology does not protect you, you will (seen by an ...


1

My one question for Charybdis is: are there black holes that erratically/periodically vary the radius of their event horizon? The radius of a black hole is determined by its mass, angular momentum and charge. Since neither of those can vary erratically due to conservation laws, nor can the radius of a black hole's event horizon. The only way those can ...


1

An additional problem is how to stop rotation. Differences in albedo (reflectivity) and (inevitable in a vacuum) offgassing rates on the surface of asteroids has been known to cause them to spin up to the point of breaking apart. A method for redistribution of mass,changing of shape, or off-axis propulsion (for rotational acceleration) would be necessary to ...


1

One detail about Alcubierre drives, which we handwave away as quickly as the setting allows for convenience, is the trouble with controlling the warp from within the warp. The most "practical" way to achieve this (for definitions of "practical" that involve megastructures) is to build what amounts to a tunnel or track, or analogous system, that controls the ...


1

A nuclear powered, supercritical steam rocket is probably your best bet. However, you're dealing with some serious engineering problems here, not the least of which is reaction mass. These kinds of travel paths are known as brachistochrone paths (for shortest time-distance), and require a lot of acceleration. The good thing though is this acceleration ...


1

You don't have to exceed light speed The good news: You don't need to go faster than light, light can go from one end of the solar system to the other in less than a day. If you're going that fast, you can pretty much ignore orbital mechanics (at least until you slow down). The bad news: Speeding up and slowing down takes a lot of energy. Speeding up and ...


1

I feel like I'm missing something about your question. If you want to be able to write faster-than-light travel into your world only using technology that has only been verified feasible by real-world scientists, I'm not sure what to tell you. I guess you'll have to wait and see before you start writing your story. You're writing future science fiction. ...


1

I doubt this will ever be seen, being such an old thread...but I had an idea recently, and this thread came up during an intellectually curious search. Space racing could be done really soon, in my opinion, using the same basic theme as FPV drones. Pilots would be on Earth, and have nice equipment which would point to space. A course would be launched into ...


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