At our current max speed (692,000 km/hr, stated max speed of Parker Space Probe), it would take about 173,000 years to get to that planet.
We could instead choose to Wait and grow our tech. By picking a constant annual growth rate and then doing some calculus to find the minimum, we can calculate the shortest possible time it will take for us to arrive there.
One common recommendation for annual energy growth rate is 1.4%, and then taking the square root to get velocity growth rate since velocity has a square root relationship with energy.
By plugging that in, we can minimize our time by growing for 1020 years, and then traveling for 144 years, for a total time-from-now at 1164 years.
Another paper estimated an annual velocity growth rate of 4.72%, quite a bit faster. Plugging that in, it says we should wait 195 years for a travel time of about 21 years, or 216 years overall. This is of course incorrect since it assumes being able to travel FTL. So if you instead look at how long it would take to get to light speed travel at that rate, you're looking about about 159 years, or arriving at the planet at a time-from-now of about 270 years.
Of course, if you're seeking to minimize time-from-now from the perspective of a traveler, maybe you'd take off sooner. Kind of a tradeoff - less time to wait for the traveler, more time to wait for the home planet. I haven't figured out that part of the math yet.
Energy growth is due to end sooner or later.
First, in the real world, any long term exponential growth is actually the upward branch of an S (that plateau at some point) or of a bell curve (that falls down after a peak).
Second, with such an energy growth rate we'll boil the ocean from heat dissipation long before we reach the stars.
I always thought that was a very well thought out aspect of The Expanse: spend half the trip accelerating, then flip the ship around and spend the other half slowing down (aka accelerating in the opposite direction).
> I always thought that was a very well thought out aspect of The Expanse: spend half the trip accelerating, then flip the ship around and spend the other half slowing down (aka accelerating in the opposite direction).
With current technology you would not do this, since that means using extra fuel that weighs a lot and thus increases the force required for the same amount of acceleration as you'd get with less fuel and less burn.
Of course that changes drastically if the fuel required for more acceleration (and its container) is very light-weight. I would assume fusion or fission based thrusters would be better in this regard, however I think currently those produce very little acceleration in a vacuum compared to combustion thrusters.
Since the rocket equation is a function of the effective velocity times the natural log of the wet/dry mass ratio, changes in exhaust velocity matter more than changes in propellant mass: you're better off with heavier propellant moving faster, than lighter propellant moving slower.
Ion drive engines tend to use xenon (a heavy nobel gas) for this reason. Unfortunately, xenon is rare even on Earth, and extraordinarily rare in space -- tanking up on a road trip would be difficult.
Going later to optimize for time is one aspect of deciding how to spread throughout the galaxy. Another question might ask, which is the most risk reducing strategy? And the answer might be completely different.
Personally, I think that if humanity progresses that far technologically, without destroying itself, we probably won't care that much about habitable planets or planets with water. We'll just live in space and harvest the energy and resources that are available nearby. There are a lot of other planets much closer to us than K2-18b. We could just build bases in orbit around those stars, harvest asteroids for minerals and hydrogen for fusion power.
Alpha Centauri would "only" take 22 years to reach at 0.2c (plus some time for acceleration and deceleration). You could leave earth and live to see that solar system, and you could travel there on a ship that is basically a large city that will just park itself in orbit around the star on arrival, acquire resources, and start building something bigger.
This will make the 22 year trip to Alpha Centauri more palatable.
1000 year trip in a single lifetime will require some life extension as well
Perhaps not ships containing humans, but some kind of other tiny ship containing a replicator machine and DNA for humans.
For 0.999c, it would only take around 71 days to reach Alpha Centauri from Earth (as seen from the ship). That's pretty mind boggling.
It seems the issue with fusion is that it actually works much better at scale. But the same could be said about nuclear reactors - it obviously is much harder to build a compact one.
If, overlooking the details, we were able to build a cubic meter sized "fusion box" that outputs 276W, then it would take about 2 million of them to produce a reasonable output for a power plant of 600MW. And it would take up about half the volume of NASA's vehicle assembly building, ignoring any support structure needed. That's not unimaginably huge, but it's pretty large compared to other types of power plants, I would think.
So assuming we solve all the technical problems to capturing the power source of the stars using handwavium or perhaps generously donated alien widgets, I wonder if it might still be uneconomic.
I take your point though - hypergrowth cannot be sustained - and estimating that exponent is fairly valueless if volatility is too high. This is all just math fun that won't be valuable if we bump along for hundreds of years and then all of sudden make a massive discovery.
Most scenarios I've explored - low velocity growth rate, nearby planets/stars - the Wait Calculation tells you to stop researching and start launching long before your tech gets to significant fractions of light speed.
First of all, you're right that this won't really impact your answer at insignificant fractions of light speed. You mentioned that using the 4.72% growth rate, the equation tells you to wait until you've passed the speed of light, and I thought it might be interesting to more accurately model the energy required at relativistic speeds.
So the same way that you used the classical mechanics equation for kinetic energy, E=mv^2/2, ignoring mass and solving for v, to get v=sqrt(2E) and approximating to v=sqrt(E), I thought you could manipulate the relativistic equation similarly.
Now, having gotten a solution from WA, I'm starting to think that I overestimated the effect on accuracy that changing the equation would have. I want to approximate the solution by ignoring some terms or changing an nE to an E^2 or something, but I think that might negate any gain in accuracy.
So to answer your questions more directly, I was attempting to address the error you get when the calculation tells you to wait until you can travel above or near the speed of light, and I only included mass in my equation to try to communicate it to you more accurately, with the assumption that when actually using it you would ignore the mass.
Anyway, I hope I at least clarified my previous comment, even if it turned out not to be very useful! If anyone has a better understanding of how to better model relativistic speeds I'd love to hear their explanation.
Pouring more energy into acceleration won't make you move faster (even subjectively) but it will shorten the way. (From the outside, it looks like time dilation.)
Cosmology involves distances that are so great that it seems like it's pouring a whole bunch of smart people's efforts down the drain in an ultimately futile waste of brain power that will never amount to anything much at all. Besides, when we get faster than light travel we can just pick up exoplanet research where we left off and it will actually be practical and probably far more efficient with the computers and such we will have developed by then.
I think it depends on what one wants to get out of the research. If the goal is a commercially realizable product on a shortish time horizon (say < 50 years), then cosmology may not be the best approach. But the justification for cosmology and much of astrophysics is typically that it is a probe of fundamental science and the acquisition of knowledge for its own sake. In which case whether we can ever travel to other planets or galaxies is moot, since it's the physical understanding and knowledge that's the goal.
Many before me have used the example of relativity, which when proposed, seemed to have little practical value. But GPS wouldn't work without relativistic corrections. 100-120 years ago one could've made a similar statement about fundamental physics and work on relativity. But if we'd abandoned it because of a lack of immediate relevance then we wouldn't have workable GPS today. The benefits of fundamental research (in many areas, not just astrophysics) are often quite difficult to forecast.
FTL requires numerous things to be true about our universe, that all signs say are not.
If we're in a physics simulation, we don't experience at the rate that the simulation is processed. One "tick" of the simulation could be processed in one second of the host universe, or one hour: and we wouldn't feel the difference. We are processed at the same tickrate as the rest of the universe, so we experience the passage of time at the same rate that the simulation flows.
The speed of light isn't just the speed of light, it's the speed of causality. It just so happens that light moves pretty well at that "speed limit" (in a vacuum). We could ask our computational hosts to increase or decrease c, and we still wouldn't be able to travel any faster than it.
Would probably be a heck of a refactor to get it working without bugs though.
> What does speed of causality mean? And how is light so close to that?
Take a look at this video by PBS Space Time on the topic:
You may need to go down the rabbit hole and watch the earlier videos on relativity and related topics.
Here, I found a copy: https://emperybooks.com/wp-content/uploads/2018/06/Greg-Egan...
Leaving SciFi aside, our communication technology will be up to the task of relaying information comparatively quickly (light speed or faster), and parallel societies could be built in neighboring solar systems.
What we know of this reality is so limiting compared to what we can imagine.
Good dreams. Many of us have them.
I also like to dream the knowable remains much larger than the currently understood too.
This is actually a central theme of the Zones of Thought novels by Vernon Vinge where a character in the far future describes our current time as the "Age of Failed Dreams" (GAI, nanotech etc.) - turns out that he is wrong but for rather neat reasons....
The Expanse series by James S. A. Corey;
The Commonwealth and Void trilogies by Peter F. Hamilton, and the Night’s Dawn trilogy also by Peter F. Hamilton;
The Dune saga by Frank Herbert.
I think I liked it in the end, though not as much as his other books, but can absolutely understand people would dislike it.
It's the culture with more detailed worlds and villains.
I don't think measuring progress is tivial enough to make that assumption. It's also unfair to blame a fascination with deep space for any slower progress, things are more complicated than that.
Getting humans onto anther planet asap is one of the most important things one can pursuit for humanity. The earth is a giant single point of failure
if we get FTL, we'll be able to pick up that research before we left off ...
Well, at least they're not making people click ads ...
or observe civilizations broadcasting knowledge in a loop: motivation? perhaps the faster they can get others up to speed, the faster others might contribute knowledge back which may some day save their civilization.
Just because we build more power plants or sell more tractors doesn't imply a corresponding improvement in spacecraft technology.
The Wait Calculation seems to make even less sense than the Drake Equation - which is at least correct in theory even if the actual variables have so much uncertainty it is useless.
This is your mistake. It's an approximation that works well only at low speeds.
Where does this come from? Does it even hold water when compared to past data? Looking at some Wikipedia data for the past 20-30 years, it seems that the increase in speeds is much higher:
Given the total journey would be ~40,000 days the 230 days of acceleration probably isn't going to impact things too much. Even if you brought it back to 1g acceleration, it's still only around 700days out of 40,000.
That'd be fun to add, though. I'm not really sure what human-safe acceleration is - people here assume it's in the 1g-3g range. (That seems like a lot to me though, particularly for a long period of time - I think anything more than a fraction of g would be wildly uncomfortable.)
Having said that, the distance and duration means that only a small portion of this journey would be under acceleration, the rest would be in zero g.
Spending a century in zero g would probably have a bunch of strange side effects and almost certainly mean that the people alive when they arrived wouldn't be able to stand the planets gravity.
This exact topic is what about 80% of The Expanse is about.
Edit: Of course, at constant 1g acceleration, at day number 354 we reach 1c. Don't know if we should start coasting before we reach 1c or just the hell with it and see what happens if we keep accelerating.
> Don't know if we should start coasting before we reach 1c...
Don't worry about it. Your rocket would need to expend an infinite amount of energy to accelerate to c. The energy stored in your finite-sized rocket is finite. At a certain point it becomes futile to keep trying to accelerate -- though I suspect that the impacts of space dust will eventually cause a significant amount of drag
I'm not sure what you mean by this. You could also say "the slower you get, the more energy it takes to maintain constant acceleration". Constant means ongoing, so as long as it is constant, you are going to have to expend more energy.
Unless you mean that somehow, you could determine your absolute speed by how much you accelerate for a given expenditure of energy, but wouldn't that violate relativity?
Edit: Oh... I guess not. :) I got confused with the extra g's we'd need to escape earth, but that's so short-term that it can be ignored. Yeah, I think 1g would be perfect.
1. This planet probably doesn’t have a solid surface
2. Being in the “habitable zone” doesn’t mean a planet is habitable
3. The detection is of water molecules, chances are the water only exists as vapour in the atmosphere of this small gas giant.
4. If you ask 10 astronomers about this you will get 11 opinions
She said to me "Yeah sure, but who cares? What it really tells us it's that it's possible to do this in linear time at all. That might not have been true, and now we know we might find a faster linear algorithm."
(All of this is paraphrased because it's been over a decade).
The point is: we have found another planet with water. We now know this is possible! We know that it's probably not super uncommon (or else we wouldn't have found one so soon). That's what's amazing about this.
So what if it's not perfect, it's a great discovery!
Whether it's common is still unclear, given that so far there's a big bias towards detecting large exoplanets that are close to the host star.
Sometimes N=2 is not that different from N=1 though. Specifically when you don't think the situation is necessarily that rare, you just don't have a big population to choose from. That's the situation here.
Astronomers expect to find other Earth-like planets. We suspect rocky planets aren't that rare, we know planets at comparable distances from the star are not that rare, and we know H20 is plentiful in space. The problem is one of detection. The smaller the planet, the harder it is to detect water, so most of what we've found so far is gassy giants.
A good analogy is the fact that I don't know anyone who shares my birthday. That doesn't mean I would be amazed if I were to find someone did share my birthday, cuz I have no reason to suspect my birthday is particularly rare. I just don't know that many people.
Whereas finding a second one tells us a lot. So that's why I say we are in more like the N=0 case, and that finding a second earth-like planet puts us in the N=1 case.
True. Being a spooky near twin of Earth isn't necessarily enough.
The air inside popcorn factories is basically identical to the Earth's atmosphere, but breathing in diacetyl, a butter flavor you'll find in that air, will kill you a few months or years later.
Popcorn lung really undermined my naive view that we would one day be able to run a scan or a sniff test on a planet and then just breathe without assistance.
You have an identical twin to Earth with slightly different dust composition and it could shred our lungs. We are highly, highly tuned to our home.
Which doesn't mean we can't go anywhere. But it won't just be advances in travel speed that will get us off world. It may also require drastic modifications to the human organism.
People land on a planet, go "I wonder if the atmosphere is breathable?", then open their helmet and take a deep breath.
But I think by the time anyone is arriving on a planet around another star, it will be with biotechnology that allows adaptation to a rather wide variety of environments.
Does "habitable" mean "habitable for humans"? I thought it didn't, but after reading some dictionary definitions, i believe it does. On the other hand looking at the planetary habitability wikipedia page it's clear that it means "life-friendly". No wonder many people are confused.
Of course a planet with 8-9 times the mass of earth is not very friendly for humans, ignoring all the other possible issues (pressure, chemical composition, radiation, flares etc)
So, there could be "super-earths" with life similar to ours, even intelligent, and they would never be able to participate in a space-faring society.
It’s almost entirely arbitrary, but roughly based on luminosity of the star.
I'm not entirely clear on the deciding factors, but it's probably mostly density.
Rough napkin formulas below. Apologies for formatting)
F(g) = GMm/(r^2)
Volume of a sphere = (4/3)pir^3
mass of a planet = density volume
given that G, 4/3 and pi are constants, it comes just to density multiplied with diameter.
That's why the gravity on the surface of neutron stars is so high, even when the mass is the same as our Sun.
If Neptune is 57 times the volume of Earth and Jupiter is 1321 times the volume of Earth, then Jupiter is 23 times the volume of Neptune.
So the relative difference between Neptune and Jupiter is less than half the relative difference between Earth and Neptune.
As another illustration, let's take a different trio of objects: a golf ball, the Moon, and the Earth.
Using very round numbers, it is safe to say that the volume of the Moon is about one zillion golf balls.
The Earth is about 50 times the volume of the Moon, so the Earth is 50 zillion golf balls.
Clearly, the difference between 50 zillion and 1 zillion is much greater than the difference between 1 zillion and just 1 golf ball, by a factor of nearly 50.
Or is it? If you ask anyone on the street, they won't have to calculate anything, they will tell you that the Earth and Moon are much more similar in size than the Moon and a golf ball. That's because they are using relative sizes, not absolute.
 - https://www.nasa.gov/mission_pages/station/expeditions/exped...
If you do it in a country that doesn't allow you to be declared legally dead when you are out of contact for a couple centuries, and if the institutions involved don't collapse, and if the interest on the account outpaces inflation, sure.
What percentage of the banks that were around 222 years ago have not failed?
So it might not be that far fetched, assuming that the banks keep your accounts open after more than 100 years without use.
I was just pointing out that it might be somewhat possible for banks to exist for a span of time big enough for this.
Seems like your best bet would be to park your money with several very old banks: https://en.wikipedia.org/wiki/List_of_oldest_banks_in_contin...
Also might want to think about purchasing bonds: https://en.wikipedia.org/wiki/List_of_oldest_banks_in_contin...
Lloyds bank founded 1765
Barclays founded 1736
I doubt any banks in the new world are as old.
You're on a grass field, sitting on one of those riding lawnmower thingies, with a broken throttle. It's moving at a fixed speed of 1mph. You can't ever change its velocity. But you can steer it. If you are going precisely east-west, then it means you're not going north-south. The more you go north-south, the less you'll be going east-west. If you're going precisely north-south, it means you're not going east-west at all. One direction is traded against the other.
Pretty straightforward, right?
So here's the analogy: that grass field is a "dimension" in the same way that "spacetime" is a "dimension". The two "directions" of spacetime aren't "east-west" and "north-south", but "space" and "time". These are inherently traded against each other. The more you're moving through one, the less you're moving through the other.
So what about that constant-velocity rideable lawnmower? That's "c" -- the speed of light. You're always traveling at this velocity. If you are sitting still in space, then you are nonetheless moving through time. Your rate of movement through time is "c". But as soon as you start moving through space, it means you are moving less through time. This is exactly the same tradeoff as moving north-south vs. east-west. If you devote 100% of your "c" to moving in the direction of the "space" axis, then it means you're not moving on the "time" axis at all.
(This is basically all it means for something to be a "dimension": different axes that are traded against one another.)
This analogy can be used to understand quite precisely how movement relates to time dilation. (It also helped me understand e=mc^2. Why is "c" there? What does the speed of light have to do with the embodied energy of matter at rest? Answer: nothing is ever at rest; all static matter is moving through through time at the velocity of "c", and obviously that movement must have kinetic energy.) But it's not a completely perfect analogy. Weirder relativistic effects like length contraction and frame dragging need much weirder analogies.
This may not be a problem for some definitions of time, but for the notion of time which goes from past to future, I don't think the analogy holds very well.
As far as we have observed, the same is not true with (the common-language definition of) time - I can't go back to the moment I was born, for example.
If my understanding is correct, this same condition exists inside the photon limit of a black hole. Technically you're still in navigable space -- not inside the singularity yet -- and can move in any direction. But to actually escape the black hole would require accelerating faster than the speed of light.
Again, if my understanding is correct -- and I'm definitely not a phycisist by any stretch of the imagination -- our movement through time is exactly the same phenomena. We can slow our velocity through time (by moving through space instead), but we can't escape our local reference frame without moving faster than the speed of light. If we could exceed the speed of light, then we would be moving into spatial regions which are otherwise causally inaccessible to us; in other words, we'd be going backwards in time.
So: if we could go FTL, we could escape from black holes, visit parts of the universe beyond the locally-observable limit, and go backwards in time. I think (IANAP) that these are all describing precisely the same thing.
Dunno if this helps. The lawnmower analogy has definitely broken down by this point.
Also, it makes me think: if our experience of time is navigationally equivalent to the experience of space for someone getting sucked into a black hole, does that imply the existence of a higher-dimensional universe where ordinary, non-accelerating time is as fully navigable as our ordinary "non-accelerating" space? And in that higher-dimension universe, are we living near the surface of some kind of singularity? Do the inhabitants of that universe wonder about how sad it must be for poor creatures like us, forced to live on a time gradient which inexorably slopes in just one direction, the way we might commiserate the fate of those sucked into a black hole?
From the perspective of an object accelerating, newtonian physics works totally intuitively. If you had a rocket that could accelerate at 1g indefinitely, you just go faster and faster and faster and you get to any destination you want (even far away!) pretty quickly. And it would be a rather comfortable trip! You'd have Earth-like gravity the whole way.
It's really only the observer's perspective that things get confusing. When an observer watches something accelerate, they see it never going faster than the speed of light, no matter how fast it "actually" goes.
The trick is time. Time for slow things passes faster than time for fast things. A clock on a very fast rocket ticks much more slowly than clocks on (relatively) stationary things. That's how the paradox is solved.
Let's say you wanted to visit the Andromeda galaxy, which is around 2,500,000 light years away. If you had a rocket that could travel at 1g indefinitely, you'd get there in a comfortable 29 years! However, observers on Earth would see the trip taking around 2,500,000 years.
If you'd like to play with these numbers yourself, feel free to check out this neat calculator (not made by me)
Time might not even exist in and of itself.
It is worth adding for the sake of clarity that light has no perspective or frame of reference because photons are non-inertial.
And for that reason they don't experience distance either. So the term 'sun-kissed' isn't actually that far off...from the photon's perspective the sun IS giving you a kiss.
Spend twice as long on boats though (32 years) and you can do about 10,000 light years.
And what if you drove your ship straight into a super-massive black hole?
There's a short story about the Big Rip
I should make a kickstarter, but I am already in my jammies.
But granted, all people I know would be dead and some I could find in the history books maybe..
Where you would also be, at that stage.
You might come back to discover that after several generations without oversight your trust has invested in bombing children and enriching the fund managers. I dunno.
All of Europe has gone through multiple revolutions, USA was only 30 years old back then so you wouldn’t have considered it ... that leaves what, the UK? Any parts of Asia that survived since 1797?
Nothing is risk-free, diversify! The likeliest outcome aside from coming back to nothing is you come back to an institution that is nothing like what it started.
Maintaining 1g of acceleration for a useful amount of time would require an extraordinary amount of propellant.
All of those estimates are tongue-in-cheek and are accurate if your energy expenditure is actually unlimited.
Not really that long.
Travelling at that speed (0,00064c - no relativistic effects) would take ~170,000 years.
If we could pull that trick so easily, we already would have.
I just realized I have no real concept of how many stars there even are within, say, a 100 light year radius of our sun (I guess that's a more realistic thing to find out than the number of planets).
A quick search provided some estimates and they're kinda... disappointingly low, at around 20000 stars. That's a number where some "1% of 1% of 1%" kinda filter quickly ends up in a scenario where a planet fitting all our criteria might simply never be in reach. For something more "realistic" (I know, heh!) like 20 light years, there are only 150 solar systems. I've seen different numbers and have no idea how they're calculated but for the usual astronomic scales which quickly go into "billions" territory, it seems we're kinda stuck with a comparably small list of candidates.
It might cheer you up to think that's the only reason the human race happens to be the one in our neighborhood that made it into space, without being stepped on by an Old One.
It could well be the universe is filled with life, but the dominant mode is underground chemo/radiotrophic microbes on planets without stars.
The implications for the Drake equation are pretty big.
Rockets without any promise of ever being able to break orbit are good for what, war? Would you keep developing them? Would you give up dreams of the stars? Would you look for intelligent life you couldn't ever possibly meet?
Nuclear rockets don't seem to be very hard. They're somewhat dangerous if they explode, but they aren't very hard. Fairly solid prototypes were built decades ago and there's little to suggest they couldn't have been made production-grade . We'd have them now if we didn't find the risk/reward to be too highly slanted to the "risk". Other species and other ecosystems may come to different conclusions, e.g., an ecosystem already more exposed to radiation and evolved to deal with much higher levels of it may judge it much less "risk" for some radionuclides to be scattered across the landscape in case of failure.
What can be more of a problem is being in a place where you have no obvious access to technology at all. However smart our cetacean buddies may be, it is not clear even at this point in the 21st century what path to technology they could possibly have from their starting point. "The literature", a.k.a. "science fiction" has hypothesized breeding programs to develop various tools, but it's still not entirely clear how they'd get from "breeding useful jellyfish" to, well, anything like technology as we know it. It's possible we're just not solving this problem because we don't have to, maybe there's some easy path with the right development path, but it's still not clear what that would be.
: One of my markers for "the space age is truly here" is when we lift a nuclear rocket into space, sans fuel, and fuel it with space-sourced radionuclides. Earth-bound citizens will still complain, because "NUCLEAR BAD!", but their complaints will be ignorable at that point.
I spent a day once trying to figure out what the Bronze Age would be like for marine creatures. Oxidation is less of a problem but galvanic action is huge. Fire pretty much doesn't work, which blocks a whole bunch of precursors like ceramics.
The big problem with marine technology isn't that it's totally impossible, it's that there's vast gulfs between various achievements and little sign that continued progress on some matter will lead somewhere. You could raise jellyfish to be transparent and lens shaped and build some telescopes, but how do you figure out that's a thing that might be a good idea? You might be able to turn an ocean vent into a forge, but how do you figure out that's a good idea? We had a path where we noticed certain rocks in a fire ooze useful metal, for instance. We didn't deduce from first principles the Periodic Table, guess the properties of metals from logic and maybe our interactions with (very soft!) silver and gold, determine it was likely that some of those colorful rocks are metallic salts, and then determine they might be useful to mine. We found they were useful to mine, then after thousands of years of civilization built on top of the resulting tools, only then figured out the why of a lot of those things.
This is one of those places where it's really a good idea to understand that despite the pretty Just So stories where science pre-dates engineering, in reality, engineering extremely frequently has predated science, at times by centuries. How are water-bound creatures going to figure out enough engineering to even get science going?
Certainly, as I said, they can breed things, but how do they even know where to try to go? How do they maintain the discipline to breed things over hundreds or thousands of generations? How do they get to genetic engineering?
There may be answers to this question but they sure aren't obvious.
Is there any combination of tricks that can realistically push the envelope there? For example can we use a space elevator to start higher/faster (or, I don't know, balloons? a catapult or railgun or something?), laser power delivery from the ground, so we don't have to carry all the fuel, and an orbiting way-station for refueling, etc.?
From the reference article:
> Travelling from the surface of Earth to Earth orbit is one of the most energy intensive steps of going anywhere else. This first step, about 400 kilometers away from Earth, requires half of the total energy needed to go to the surface of Mars.
Which means that if we use something like a balloon/blimp in the first stage, it would be a lot more energy efficient.
Anyone knows why it's not done that way already?
Also, whatever happened with the plane+rocket Virgin Galactic project?
If you go straight up far enough you’ll be out of Earth’s gravity well.
You’ll still need acceleration to escape the solar gravity well, but you’ll never need horizontal acceleration necessary for Earth orbit.
Launching from stationary altitude doesn’t save much at all
While you could theoretically do this by accelerating directly up, You still have to accelerate somehow.
Space elevator ideas usually have the hop-off point all the way out at geosynchronous orbit to solve the velocity problem. Which is.. a really tall elevator.
So a balloon/plane/blimp/very high building will only help very marginally.
Realistically, but not plausibly unless its an emergency, Thermonuclear bombs:
These methods will all help with the first 1% of your problem, getting off of the earth.
But you need so many orders of magnitude more energy to reach the kinds of velocity needed to get to another star in less than a million years. It's just an unfathomable amount of energy per kg. Put simply: if you can get to another star, getting off the planet is nothing.
As a KSP engineer would say, it "needs more boosters" https://i.redd.it/zuymxc5bb7s21.jpg
Maybe it implies that every interstellar mission is just an in-flight rescue mission.
I would imagine the atmospheric pressure would be the most noticeable consequence of this.
The article notes that the planet is substantially larger:
> K2-18b is very unlike our home world: It’s more than eight times the mass of Earth, which means it’s either an icy giant like Neptune or a rocky world with a thick, hydrogen-rich atmosphere.
And the Wikipedia article for "Super-Earth" mentions something relevant:
> a planet with 2 Earth-radii and 5 Earth-masses with a mean Earth-like core composition would imply that 1/200 of its mass would be in a H/He envelope, with an atmospheric pressure near to 2.0 GPa or 20,000 bar
For comparison, the atmosphere on Earth (sea level) is approximately 1 bar.
It looks like the apparent atmospheric pressure on such a planet might be similar to being approximately 200 kilometers below the surface of the ocean on Earth. For additional perspective, the Mariana trench is (I believe) the lowest point on the planet, and is only like 11 kilometers deep.
So I guess what I'm saying, is that the apparent doubling of one's weight would be an insignificant concern in the grand scheme of things.
Assuming we could generate a sufficiently focused laser or other communication mechanism to communicate over 111 light years (which we can't), currently we have no known material that we could build the comm device out of that would survive a 111 light year trip to another solar system intact enough for the device to actually function.
Still a bit wishy-washy since it involves magical technology that we have no idea how to build, and if we had the communications technology we would probably have the materials science too, but hopefully that gets the point I was originally trying to make across.
Cosmology is so cool... too bad we do not have time for that: we cannot even cure the common cold!
Cosmological bimetric model with interacting positive andnegative masses and two different speeds of light,in agreement with the observed acceleration of the Universe
It sounds like you get anti-gravity for free along the way to getting superluminal travel.
Assuming chemical propulsion and no refuelling at the destination.
"If the radius of our planet were larger, there could be a point at which an Earth escaping rocket could not be built. <snip> That radius would be about 9680 kilometers (Earth is 6670 km). If our planet was 50% larger in diameter, we would not be able to venture into space, at least using rockets for transport."
So we have an "or" assumption, not "and", with an additional and assumption about refuelling. That's how I read it.
The atmosphere can also be much more shallow than earth.
Also I was more referring to winged flight than balloons balloons might be a problem of their own if the pressure at ground level is too high for them to inflate normally.
Between earth and Venus there are a lot of options so if the atmosphere is similar to earths sans the water vapor I’m not entirely sure flight would be actually easier I can probably do some napkin maths over the weekend for this.
The savings you get when launching from say an aircraft at 40,000 feet mainly come from not having to go through max-q at sea level the relative amount of propellant you’ll need to get to orbit is the same you can just use a smaller rocket but it doesn’t help to overcome the rocket equation trap.