Would it be possible for lifeforms on high gravity worlds to develop space travel?

[Spaceception]

I've read somewhere that if intelligent aliens arise on planets with radii of 1.5 Earths and higher, they wouldn't be able to go to space because the gravity would be too high, is that true? And if so, would it really be impossible? Could there be other ways to get into space that would work under high gravity? Or would the aliens be stuck on their planet forever, until some other aliens gave them a space elevator or something?

Edited April 17, 2016 by Spaceception

[Andem]

47 minutes ago, Spaceception said:

I've read somewhere that if intelligent aliens arise on planets with radii of 1.5 Earths and higher, they wouldn't be able to go to space because the gravity would be too high, is that true? And if so, would it really be impossible? Could there be other ways to get into space that would work under high gravity? Or would the aliens be stuck on their planet forever, until some other aliens gave them a space elevator or something?

It would have a similar composition to earth, albeit scaled up. Unfortunately, the atmosphere would also scale and would be quite dense, so Imagine putting Eve's atmosphere on 64k Kerbin with only the stock parts to work with. Surely not impossible, but likely you would only have enough fuel for a few such immense rockets. I may be wrong tho...

A space elevator would be an immense task on Earth, the Moon, Ceres, even Eros could cause you some trouble. Trying to assemble one on a super earth first try would be nigh near impossible unless you have near-magical technology.

Edited April 17, 2016 by Andem

[Frybert]

Moved a science thread to science subforum.

[Spaceception]

8 minutes ago, Frybert said:

Moved a science thread to science subforum.

Thx.

[Motokid600]

The lifeforms themselves would be MUCH bigger. I even dare to say that bipedal lifeforms may be impossible on high gravity worlds. These aliens would walk on four or more legs and be incredibly stocky and heavy. So if they did advance to the point where they start developing rockets.... Sure. It would just take a much bigger rocket.

However I'm not sure how such creatures could get to that point. Because I know for a fact that humans standing up at one point was a huge stepping stone in our evolution. We'd still be apes if not for that. Would we be as advanced as we are? I don't think so.

[A Fuzzy Velociraptor]

2 hours ago, Motokid600 said:

The lifeforms themselves would be MUCH bigger. I even dare to say that bipedal lifeforms may be impossible on high gravity worlds. These aliens would walk on four or more legs and be incredibly stocky and heavy. So if they did advance to the point where they start developing rockets.... Sure. It would just take a much bigger rocket.

Actually they would probably be smaller because of the square-cube rule. A smaller creature would have an easier time supporting itself. Also there isn't any reason they couldnt develop in a different manner maybe looking almost drawven, to quadrupedal (or more feet), having some sort of prehensile tail or tentacles or even being aquatic. There are any number of ways that a creature could develop given its circumstances.

Anyway, I don't see any reason why it wouldn't be possible for them to develop space capability. Certainly some things like SSTO would be nearly impossible but just getting to orbit likely wouldn't be much more difficult at all. Assuming the planet in question has a density comparable to earth and a mass 1.5x that of earth and that earth's radius is 6371km using R=(1.5*r_e)^(1/3) (this can be found by setting the two densities equal and using the volume of a sphere) the new planet's radius is 7293km. Using a simplified vis-viva equation for a circular orbit (v=sqrt(1.5mu/R), assuming that the gravitational constant is the same everywhere in the universe and a 400km orbit the orbital velocity may be found to be about 8.8km/s. This is higher than earth of course and we can probably expect higher gravity drag and higher aerodynamic losses. Even if those loses totaled 4k it would require 12.8km/s of delta V. It is quite a lot, but it isn't impossible given that that number is a little less than what we require to launch something to GEO.

Of course there would be engineering challenges to address but even most of those could be dealt with. At launch engines would likely be less efficient than on earth and would either require a higher chamber pressure, earlier staging, or expanded use of altitude adapting nozzles. Though it really depends on how much their standard atmospheric pressure is. If they were only a 2atm, it likely wouldn't pose too much of a challenge except that engines would either have to run on a higher pressure or run less efficiently. If it were in the range of 20 then it would be quite a challenge though that could likely be overcome through launching from a high altitude, airlaunching, or accelerating through some other method. One thing that would be interesting, given that they would likely resort to higher chamber pressures they might never encounter engine coking below 5MPa.

[Motokid600]

Interesting. One things for sure is that changing the gravity either way really would result in truly alien-looking creatures. I just figure a high gravity world would have everything really low to the ground including plants and animals. They'd be built to spread their weight out over as much surface area as possible. Where as for low gravity worlds... look at Avatar. Discounting the floating rocks they actually made a VERY good depiction of life on such a planet. Everything grows really tall and skinny.

[Spaceception]

20 minutes ago, Motokid600 said:

Interesting. One things for sure is that changing the gravity either way really would result in truly alien-looking creatures. I just figure a high gravity world would have everything really low to the ground including plants and animals. They'd be built to spread their weight out over as much surface area as possible. Where as for low gravity worlds... look at Avatar. Discounting the floating rocks they actually made a VERY good depiction of life on such a planet. Everything grows really tall and skinny.

 Off topic for a sec, could the floating rocks exist?

 

Alrighty, back on topic, what would the lifting capability be for a rocket the size of SLS on the high gravity world?

Edited April 17, 2016 by Spaceception

[AngelLestat]

50 minutes ago, Spaceception said:

 Off topic for a sec, could the floating rocks exist?

If there is something as unobtanium (super conductor at earth temperatures) or normal superconductor material in a planet that is cold enough to sustain that effect, then you only need a high magnetic flux... then yeah.. it can happen..   Chances increase if this planet is like the one in the movie, orbiting a gas giant (magnetic flux between the two, both tidal lock).

  

[magnemoe]

1 hour ago, A Fuzzy Velociraptor said:

Actually they would probably be smaller because of the square-cube rule. A smaller creature would have an easier time supporting itself. Also there isn't any reason they couldnt develop in a different manner maybe looking almost drawven, to quadrupedal (or more feet), having some sort of prehensile tail or tentacles or even being aquatic. There are any number of ways that a creature could develop given its circumstances.

Anyway, I don't see any reason why it wouldn't be possible for them to develop space capability. Certainly some things like SSTO would be nearly impossible but just getting to orbit likely wouldn't be much more difficult at all. Assuming the planet in question has a density comparable to earth and a mass 1.5x that of earth and that earth's radius is 6371km using R=(1.5*r_e)^(1/3) (this can be found by setting the two densities equal and using the volume of a sphere) the new planet's radius is 7293km. Using a simplified vis-viva equation for a circular orbit (v=sqrt(1.5mu/R), assuming that the gravitational constant is the same everywhere in the universe and a 400km orbit the orbital velocity may be found to be about 8.8km/s. This is higher than earth of course and we can probably expect higher gravity drag and higher aerodynamic losses. Even if those loses totaled 4k it would require 12.8km/s of delta V. It is quite a lot, but it isn't impossible given that that number is a little less than what we require to launch something to GEO.

Of course there would be engineering challenges to address but even most of those could be dealt with. At launch engines would likely be less efficient than on earth and would either require a higher chamber pressure, earlier staging, or expanded use of altitude adapting nozzles. Though it really depends on how much their standard atmospheric pressure is. If they were only a 2atm, it likely wouldn't pose too much of a challenge except that engines would either have to run on a higher pressure or run less efficiently. If it were in the range of 20 then it would be quite a challenge though that could likely be overcome through launching from a high altitude, airlaunching, or accelerating through some other method. One thing that would be interesting, given that they would likely resort to higher chamber pressures they might never encounter engine coking below 5MPa.

1.5 times the mass of earth would not give 1.5 g, you must go far larger. 
Else I agree in smaller creatures would work better.
Space would probably require more advanced technology than today. 

Dense air would make flying easier even with the higher gravity up to flying intelligent creatures. 

Tails or tentacles would probably not be very strong, yes elephants are strong but they are also very large so its not so impressive.
Its also less likely to be good manipulators. 
An six limbed creature would have benefits here. 

[magnemoe]

17 minutes ago, AngelLestat said:

If there is something as unobtanium (super conductor at earth temperatures) or normal superconductor material in a planet that is cold enough to sustain that effect, then you only need a high magnetic flux... then yeah.. it can happen..   Chances increase if this planet is like the one in the movie, orbiting a gas giant (magnetic flux between the two, both tidal lock).

  

Problem is that the field strength would have to be idiotic strong so strong it would affect anything including living creatures.
One quote was ripping the hemoglobin from your body, that is just as unrealistic, it would levitate you long before this
Note that an less extreme version is plausible, keep the mountain on the ground much like the inspiration in China, but have it far thinner and higher as the magnetic field stabilize and also reduce the weight some. 

[A Fuzzy Velociraptor]

1 hour ago, magnemoe said:

1.5 times the mass of earth would not give 1.5 g, you must go far larger. 
Else I agree in smaller creatures would work better.
Space would probably require more advanced technology than today. 

Dense air would make flying easier even with the higher gravity up to flying intelligent creatures. 

Tails or tentacles would probably not be very strong, yes elephants are strong but they are also very large so its not so impressive.
Its also less likely to be good manipulators. 
An six limbed creature would have benefits here. 

Apparently the actual question proposed was 1.5 times Earth radius not 1.5 Earth mass.

It is easy enough to fix, the calculations weren't difficult. If we assume that this new planet maintains a similar density to earth then the mass of the planet will be 1.5^3 or 3.38x Earth mass. If we assume a 500km orbit (though at this point the atmosphere may be starting to get thicker than this then using the simplified vis-viva equation and our starting assumptions to be sqrt(3.375*3.986E5/(1.5*6371+500)) then we find we need a horizontal velocity of 11.56km/s. Gravity drag and aerodynamic drag will certainly be higher than on Earth. Even then vehicles with 15-16km/s available delta V are available. Certainly they would struggle miniaturizing their satellites and manned space systems would be quite expensive, though it would not be impossible. Though actually I have a fairly decent comparison for what 10km/s vs 15km/s does to an available load, our Dyeus H system is expected to carry 150kg to LEO but would likely only be able to carry 5kg to a C3 of 1.78 (which would be 15km/s, about 1km/s more than LLO). Probably the largest issue they would struggle with is the atmospheric pressure at low altitudes which would either cripple efficiency or require massively increasing chamber pressures in order for rockets to actually be effective. They would likely need to use some other system for the first stage.

Edited April 18, 2016 by A Fuzzy Velociraptor

[cubinator]

Moar booster?

Orion drive?

Ok, maybe a *small* Orion drive...

I'm sure they'd find a way. There's only one kind of object that it's impossible to get to space from, and that's a black hole. A 1.5 Earth radius planet is nothing compared to one of those.

Also, @Spaceception, could you clarify: When you said "1.5 Earth radius", did you mean the radius is 1.5 times that of Earth, or did you mean you could fit 1.5 Earths inside the radius of the planet?

Edited April 18, 2016 by cubinator
Il hatel the mobilel editorl

[Spaceception]

34 minutes ago, cubinator said:

Moar booster?

Orion drive?

Ok, maybe a *small* Orion drive...

I'm sure they'd find a way. There's only one kind of object that it's impossible to get to space from, and that's a black hole. A 1.5 Earth radius planet is nothing compared to one of those.

Also, @Spaceception, could you clarify: When you said "1.5 Earth radius", did you mean the radius is 1.5 times that of Earth, or did you mean you could fit 1.5 Earths inside the radius of the planet?

The radius of 1 in a half Earths.

[max_creative]

Put them on 50 nukes and ignite them all at the same time?

[A Fuzzy Velociraptor]

16 minutes ago, Spaceception said:

The radius of 1 in a half Earths.

What?

Is the radius of the planet you are looking for 9557km or 19113km? If you mean the latter you are talking about a planet literally 27 times the mass of the earth assuming it is similar density to earth which is almost the combined mass of Uranus and Neptune.

Edited April 18, 2016 by A Fuzzy Velociraptor

[HebaruSan]

I think I may have found the original claim to the contrary (emphasis added), thanks to reddit.

https://www.reddit.com/r/space/comments/1b1pjc/if_earth_was_50_larger_in_diameter_we_would_not/

http://www.nasa.gov/mission_pages/station/expeditions/expedition30/tryanny.html

Quote

If the radius of our planet were larger, there could be a point at which an Earth escaping rocket could not be built. Let us assume that building a rocket at 96% propellant (4% rocket), currently the limit for just the Shuttle External Tank, is the practical limit for launch vehicle engineering. Let us also choose hydrogen-oxygen, the most energetic chemical propellant known and currently capable of use in a human rated rocket engine. By plugging these numbers into the rocket equation, we can transform the calculated escape velocity into its equivalent planetary radius. 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 he's specifically concerned with payload fractions. I.e., whether you'd hit diminishing returns from adding moar boosters before you got to the 15-16 km/s that you'd need. I don't have enough intuition on this to opine either way.

[Elukka]

Right now some species from a small planet or moon is debating whether spaceflight is possible on a planet as large as Earth. You'd not only need a complex bipropellant rocket, it'd need to be some mad contraption made of multiple rockets stacked on top of each other!

Our launch vehicles are designed the way they are because they make sense for Earth. A species living on a different planet would come up with solutions to fit their situation. It is harder to reach orbit from a larger planet but physics allows enough ways to do it that practically speaking, if there's a will, there's a way. For example, on a planet large enough that chemical rockets can't do it, you might shoot for nuclear thermal rockets instead. If the atmosphere is exceedingly thick, like on Venus, you might do balloon launch.

Edited April 18, 2016 by Elukka

[magnemoe]

15 minutes ago, Elukka said:

Right now some species from a small planet or moon is debating whether spaceflight is possible on a planet as large as Earth. You'd not only need a complex bipropellant rocket, it'd need to be some mad contraption made of multiple rockets stacked on top of each other!

Our launch vehicles are designed the way they are because they make sense for Earth. A species living on a different planet would come up with solutions to fit their situation. It is harder to reach orbit from a larger planet but physics allows enough ways to do it that practically speaking, if there's a will, there's a way. For example, on a planet large enough that chemical rockets can't do it, you might shoot for nuclear thermal rockets instead. If the atmosphere is exceedingly thick, like on Venus, you might do balloon launch.

Another issue, an small species weighting less than 10 kg will find manned spaceflight easier than an elephant sized one. 

An mars sized moon would be the easiest thing to lift of from, might need to be an bit larger to keep the air but the planet will help here, tidal forces for heating, and you have all the other moons to visit. 

Edited April 18, 2016 by magnemoe

[RenegadeRad]

This is a really interesting topic *grabs popcorn*

I think they could use Airship like tech, using large hydrogen, helium balloons to get their pod into space, and detach at a certain point and ignite to reach orbit, or it might be an SSTO airship... Maybe, this is just a random thought I had.

One thing to think on the other hand, they possibly may not be able to create planes itself, so space travel sounds too far... As I said, they might use air ship technology.

[cubinator]

3 hours ago, magnemoe said:

Another issue, an small species weighting less than 10 kg will find manned spaceflight easier than an elephant sized one. 

Not necessarily. Each one would build on it's own scale, so ants would build ant-sized rockets and elephants would build elephant-sized rockets, just like humans build human-sized rockets instead of ant-sized or elephant-sized ones. Then you end up with similar scale issues, because it would be really hard and expensive for ants to build, say,  a human or elephant-sized rocket. So ants would have the same issues with payload fractions, just on ant scales instead of human scales. They'd have just as much trouble going to space in their tiny rockets as we would in our huge ones.

[Spaceception]

9 hours ago, A Fuzzy Velociraptor said:

What?

Is the radius of the planet you are looking for 9557km or 19113km? If you mean the latter you are talking about a planet literally 27 times the mass of the earth assuming it is similar density to earth which is almost the combined mass of Uranus and Neptune.

I mean the planet is 50 percent wider than Earth

[magnemoe]

18 minutes ago, cubinator said:

Not necessarily. Each one would build on it's own scale, so ants would build ant-sized rockets and elephants would build elephant-sized rockets, just like humans build human-sized rockets instead of ant-sized or elephant-sized ones. Then you end up with similar scale issues, because it would be really hard and expensive for ants to build, say,  a human or elephant-sized rocket. So ants would have the same issues with payload fractions, just on ant scales instead of human scales. They'd have just as much trouble going to space in their tiny rockets as we would in our huge ones.

Fair point however probes would be pretty much the same size for all, yes its some factors here, an elephant would not care so much for miniaturization, no big deal carry an 10 kg laptop and would need an larger keyboard while an small species would be natural better at building smaller stuff and need miniaturization a lot. Still as technology develop this would even out a lot, yes the elephant probe is still three times as heavy than the cats but an manned moon landing would still be harder for them.
 

[Turf]

Perhaps they would find the highest point in their planet to be used as a launchpad, or just build a tall, sturdy launchpad to start higher.

And they have to orbit at faster speed.

So, helium balloons will probably be one of their ways to go to space. Helium is expensive in Earth, with larger Earth would gives them more atmosphere, which would give them more helium, but a ludicrous amount of helium to lift such heavy rocket. And, I've concluded, they must have much more expensive space traveling prices.

[AngelLestat]

17 hours ago, magnemoe said:

Problem is that the field strength would have to be idiotic strong so strong it would affect anything including living creatures.
One quote was ripping the hemoglobin from your body, that is just as unrealistic, it would levitate you long before this
Note that an less extreme version is plausible, keep the mountain on the ground much like the inspiration in China, but have it far thinner and higher as the magnetic field stabilize and also reduce the weight some. 

I imagine you get that info from this blog:
http://www.thegeektwins.com/2010/05/flawed-science-of-avatar-floating.html

There is a lot of people wanting to look smart just criticizing everything they found.
But the problem is that they took only 5 to 10 min to reach a verdict, sometimes with the first evidence (or flawed logic) they found.
If there is a problem you want to solve, is easier to found variables or circumstance in where it does not work, harder is to find in which range of circumstances will work.

In that blog, he does not make any math, he does not have anything to compare, he just make his verdict in a site which science is a weird topic.

Here there is another dude that tries to make their own calculation reaching a value of 6 tesla.
https://www.quora.com/Would-the-floating-mountains-of-Avatar-really-be-able-to-float-If-so-how

But I believe he is also wrong..  I can not prove it with math because I don't know so much on superconductivity and magnetic fields.
He takes into account just the field pressure in unit of area, like if only the mountain-block base area is the only thing that matters (I am not so sure about that) this mean that after that the field disappear? no.. because is conservative.  
That formula takes into account the left or right scenery?

What if you have more superconductors above?  Those does not generate quantum locking?  why?
Is the magnetic strength (tesla) what matters or the field intensity (amper/meter)?
Here is explained the difference between those effect (meissner and Qlocking), which are also related to (type 1 and type2).
https://en.wikipedia.org/wiki/Flux_pinning
"On a simple 76 millimeter diameter, 1-micrometer thick disk, next to a magnetic field of 350 Oe (28000 amp/meter), there are approximately 100 billion flux tubes that hold 70,000 times the superconductor's weight.
That same disk, if made two milimeters thick could support 1,000 kilograms, the weight of a small car.
In a superconductor three inches in diameter, there exist an estimated 100 billion flux tubes when placed over a magnetic field."

So if each piece of  superconductor can support its own weight and more in a decent field strength, why the mountains can not float?
Jupiter has a magnetic field that goes from 1Tesla=10000gauss to 10 gauss (orbit), earth magnetifc fields goes from 0.25 to 0.75 gauss.
http://hypertextbook.com/facts/1999/AleksandraCzajka.shtml

Someone may said, the mountains are far from surface, but comparing with how far the magnetic flux travels, that distance is like 1mm or less from a normal magnet.
Well, I hope someone with real knowledge on superconductors solve this issue, the parameters to have into account are:
-% of superconductor material in the mountain, gravity and magnetic flux.
-If the planet is cold enough we don't need hypothetic materials. 
-A planet with superconductor materials would have a powerful magnetic field.
-Magnetic flux can travel from a moon to the planet and back (tidal lock)