"Goldilocks" Planet Found, Could Possibly Support Human Life

Of course it is, but that is just another way, in more general terms* to describe keeping one face turned towards is sun. It is the gravity gradient that makes ALL the spin orbit resonances possible including the 1 to 1 spin orbit.

I was focusing on how the 1 to 1 spin orbit was achieved, the mechanism, not just desribing or re naming the phenomena of keeping same side turned towards the sun.

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* More general in that it includes for example two spins per orbit.

 

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I meant spin-orbit resonances other than 1:1!

 

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Certainly other than 1:1 is possible. In fact, as I recal, we have several examples in our solar system.

I am too lazy to look up but as I recall either Mercury of Venus is in a 3:2 resonance lock. Some of the moons of other solar system planets are in higher order and or 1:1 resonance locks (and of coursed there is Earth's moon)

In general the orbiting body is more likely to be in a spin orbit resonance lock the closer it is the body it orbits. This is because the gravity gradient (falling off as inverse cube) decreases more rapidly than the inverse square gravity field. Again, spin orbit locks are due to the gravity gardient, and some lack of mass uniformitiy in the orbitng body.

 

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It's a red dwarf, so its mass is more compact then our sun, but it likely weighs less then our sun. When it was a main star, it weighted less then our sun. The gravitational pull is likely more then our sun, but not by much, so it rotates around the star faster. I think the reason for the 37 day year is more due to the small orbit rather then gravitational pull and speed...

(The red dwarf is a remanent of a main sequence star that is smaller/less dense then our sun. It lost a lot of its mass after its red giant phase, but what is left is more dense then our sun.)

By the sounds of it, it seems like it lacks a satellite to stabilize its orbit. There might be other implications to this other then the lack of rotation

 

So, what would happen if we really did find an Earth-like planet 20 light-years away? I guess we would have to mount an international expedition to it...

 

No shit totally was not aware of that, or was I?

Oh I see, no one reads.

Yeeeaah figured that but considering the large size of the other planets in this system and their very tight orbits I though something other then tidal lock was as distinct possibility. Maybe we could calculate how much tidal forces the other planets exert on Gliese 581g

The very first thing we would need to do is get a telescope up in space that can detect earth sized planets around stars that are 25 light years to us or less (about 100 stars) and actually take spectra of those planets to determine their atmospheric compositions and temperatures. Right now the best we got is Kepler and it will only detect earth size worlds in stars too remote for us even to imagine traveling to them.

 

Dammit, I need to study this stuff again, seems like I might be getting a bit mixed up...

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Question: isn't that more like the description of a "brown dwarf"? I thought there was another type of star that was smaller then a white dwarf and resulted from a red giant? Sort of like....

- smallest density: main sequence -> red giant -> red dwarf
- medium density: main sequence -> red giant -> white dwarf (our star)
- high density: main sequence -> red giant -> neutron star


I thought brown dwarfs were not considered stars (too small, not dense enough to reach ignition) but rather proto-planets!? Aren't brown dwarfs the only ones that remain as dwarfs for their entire existence?

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It would be the 1400s all over again....

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... well, sort of....

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As far as present theory goes, less massive stars don't always swell into Red Giants, they can just slowly use up their fuel. In any case, they become a white dwarf afterward. However, less massive stars spend a much longer time in the main sequence, and a star 0.31 the mass of our Sun would stay in the main sequence for some 18 billion years. There are no present models that have stars passing through a red dwarf stage when it is not in the main sequence.

Nope. While there is a debate about where to draw the line between large gas giants and small brown dwarfs, Brown Dwarfs can range up to 80 times the mass of Jupiter, and brown dwarfs greater than 13 times the mass of Jupiter can fuse deuterium (they just don't undergo hydrogen fusion.)

 

I guess that's where they draw the line? Hydrogen fusion....

 

Between brown dwarf and red dwarf, yes.

 

Those are pretty large rocky planets to be in such a tight orbit around such a small star, seems like there wouldn't be so much material that close to form so many rocky bodies.. but then again M class stars are pretty small maybe they have extra material leftover.. I believe they rotate pretty fast too maybe that is going to end up being common for these stars.

Still its not expected to say the least.. I say lets build a probe and power it by detonating nukes behind it. Project Orion! I don't think nuclear fallout in space will hurt anything, wish they would have built that ship! Frustrating knowing we'll never know whats out there eh.

 

It is a long trip with lots of time for modest G force to achieve great speed.

If you are "going nuclear" I am almost sure the mass would be much more efficiently used as a small light weight reactor making electric power to accelerate some ion beam (which gets neutralized after it has high velocity) probably just protons would be best, but for light weight stored in NH3 tank(s) or stored in H2O if there are humans on board not able to 100% recycle the CO2 they exhale. Also then safety favors the H2O as even a very tiny leak of NH3 will kill them (If they don't kill themselves first to end the NH3 irritations.) With an ion beam you can get much higher specific impulse and that is what counts for a long trip.

I will just briefly mention the huge increase is spaceship mass required to both with stand the nuclear explosions and be structurally strong enough to not be "pan-caked" by huge forces applied to it rear.

 

Or you could just use a nuclear salt water rocket.

 

well its a big ship design for sure.. but still its probably the fastest thing we could actually make right now. Check this out if you haven't yet..

(hate having to wait to post links lol) google project orion nuclear propulsion and check the info.. yeah its massive but I don't think its as dangerous as people think.. its nuke anxiety I tell ya lol.

 

Thanks for this link, where I read:
"...NSWRs would generate continuous rather than pulsed thrust and may be workable on much smaller scales than the smallest feasible Orion designs (which are generally large, due to the requirements of the shock-absorber system and the minimum size of efficient nuclear explosives).
The vessel's exhaust would contain radioactive isotopes, but these would be rapidly dispersed after traveling only a short distance; the exhaust would also be travelling at high speed (in Zubrin's scenario, faster than Solar escape velocity, allowing it to eventually leave the Solar System). This is however, little use on the surface of a planet, where a NSWR would eject massive quantities of superheated steam, still containing fissioning nuclear salts. ..."

My first reactions is: Yes this is the way to go into deep space with a controlled, continuous modest acceleration, but of course some more conventional rocket is needed for the initial "leave Earth" phase.

I had a thought, not yet evaluated, for improvement. Instead of H2O, perhaps NH3 would get higher specific impulse. Certainly the Hs are nearly perfect moderator for themalizing the neutrons, and I assume (by pure guess - to lazy to look up) the neutron capture cross section on N is not much worse than that of O. What do you think of this mod, ElectricF?

 

Well the salts would have lower solubility in ammonia so it might not be able to achieve criticality.

I think uranium or plutonium metal stored in very long very thin rods kept far from each other in a scaffolding would work for storing the nuclear fuel. Then liquid hydrogen could be used as propellant. Robots would dissemble the scaffolding in flight and feed the rods into a small priming reactor where the rods would be be melted down and injected into the hypercritical reactor turning into a fissioning plasma, added hydrogen gas would be injected to add neutron moderation and keep the reactor from melting down (which would be cooled with liquid hydrogen) and of course a superconducting nozzle would direct the fissioning plasma out as thrust. It would have lower thrust to weight then the salt water design but still certainly more then any other high ISP engine design, and have several times higher specific impulse then the salt water design. It could almost be done today, all the technology is developed enough that there are no show stopper unknowns, except for the AI. For interstellar flight that will take at least decades and certainly centuries (assuming 5% the speed of light it will take 400 years to get to this star system) a sophisticated AI and robotic systems will be needed to keep the ship in working order and deal with any problems, either that or human generational crew would need to be sustained and that certainly would weigh a titanic amount. We should have such AI within 50 years, but also within 50 years we will hopefully have fusion as well (though fusion has been 50 years away since 1950!). Assuming the best aneutronic fusion is possible the fuels could be a whole lot cheaper, safer and easier to handle then U235,U233 or Pu239 metal rods or salts, just hydrogen and boron would be needed for the best aneutronic fusion fuel and would likely provide even higher ISP then even my nuclear plasma rocket design. The only downside will be much lower thrust to weight ratio and that a fusion engine will likely need to run for years to bring the ship up to speed.

 

If true, why not use an emulsion? If the heavier molecules (or very tiny particles?) tended to settle out and go critical when in Earth's gravity magnet stirring (like in Chemical flask) on tank bottom could be used until in very low G - Just the thrust - or continued, if need be.

That would be more massive due to the safety scaffolding weight compared to a NH3/U235 emulsion + boron rod and, as you note, there is the "small priming reactor where the rods would be be melted down" to add weight too with your suggestion.

If without the boron the emulsion is just super critical, then as the emulsion is sprayed out a long nozzle the neutron flux increases, but that takes a time comparable to the nozzle transit. (Sort of like Fermi watching the neutron flux increase in man's first fission reactor while standing over it with his bucket of borax.) If well designed it should work with a reasonable U235 burn fraction (at least as good as a power plants fuel rod I would guess). One would probably need to inject more liquid mass thru walls of the nozzle to fully use the heat release and cool the nozzle walls.

I am OK with liquid H2 in space as keeping it cold is easy there, but how do you get it off earth without a lot insulation (some more weight)? For this reason I think the exhaust gas is mainly neutral hydrogen plasma* with some O or N added. There will, in either case a lot of radiation from the minority molecules (O or N) so perhaps to avoid too much radiative heat loss the nozzle continues farther behind as a simple reflective cylinder. I.e. a small part of the thrust is radiation pressure.

In controlled fusion it is extremely important to not let the plasma hit the vacuum wall - the slightest amount of not fully ionized contaminate will quench it by radiative loss in mico-seconds or less. I am only guessing that the radiation pressure is a "small fraction" but each O or N may make a million photons and they have, I think, infinite ISP so perhaps we want this radiative push. It would be a man-made star we could optically track** all the way to its destination star and send mid-course corrections as needed. (No need for it to have big transmitter and associated antenna that might not unfold as planned.)

* At that point, the "nozzle" has become a rather simple magnet coil*** with decreasing turns / meter to make a divergent field (insider a reflective cylinder?).

** Earth based radar would also be used as long as possible to get accurate range/speed (Not velocity) data. The optical data would give the trajectory.

*** Aluminum wire is better than copper from a mhos/kg POV but one would need to look into their neutron flux damage rates.

 

Perhaps, it add complexity to the system though.

There would be no need for neutron absorber mass or a fuel tank mass (accept for the hydrogen fuel tank of course), the fissionable scaffolding could support its on weight and structure in flight. The primer reactor is a tiny addon and does not even need to be, just a heating element to melt the rod down so it can be injected into the hypercritical core.

Far more, this a burn fraction like an advance nuclear bomb, most of the fissionable material must undergo fission to make the engine efficient.

You could inject liquid hydrogen, need it anyways for the superconductors.

That been well mastered since Apollo, even before with the centaur and atlas rockets and stages.

I'm not sure what the nozzle shape and parameters will be, your guess is as good as mine. I can guess the ship will be very long and thin, to minimize chances of impacting interstellar dust at relativistic speeds and to minimize the size of the impact shield against that dust. Segments in my ship would be shield-fissionable scaffolding-cargo & flight control-cryogenics plant-LH2 tanks-more fissionable scaffolding-nonfissionable scaffolding-Nuclear plasma engine. As the ship burns fuel the fissionable scaffolding is cannibalized and hydrogen fuel tanks are ejected overboard.

Not sure what your getting at.

 

Have you forgotten about your "Robots would dissemble the scaffolding in flight and feed the rods into ... " (a melting system, which will be very complex, if not impossible, to handle solid U turning into liquid uranium)

Get real. Handling solids is always at least 10 times more complex than simply ejecting a liquid, especially if that solid becomes a very hot liquid in the process. Even on Earth: Contrast a fork lift to a pump.

Which do you think weighs more a liquid H2 tank and its refrigerator or a water like tank for the NH3 U235 emulsion?

As far as the boron rod vs scaffollding which can support its the speed of sound shaking a lift rocket goes super-sonic in the earth's upper atmosphere the weight advantage is clearly to stiff, very light weigh, boron rod (or just a 10 micron layer on the inside of the tank could keep the boron weight to a few grams). I am sure of this as boron has a huge neutron absorption cross section.

BTW, the neutron cross section is measured in "Barns" the reason being that when Boron's was first measured (100s of times larger than any yet measured) some one exclaimed : "My God that is bigger than a barn!" and the unit was named.

I strongly doubt that. The real problem is not the efficiency in use of U235, but can you absorb and use the released heat in the heating the exhaust. I would not be surprise if even fission only 1% U235 fission released more heat than you can handle - Remember we are talking about releasing years of power plant heat in minutes at most.

If you have any superconductors, OK and are using liquid H2, but I don't get that complex (or heavy). I.e. I suspect that for much less lift off weight simple Al wire (Of perhaps 000 diameter) is much better for the magnet part of the nozzle. Remember we will have more heat than we can transfer to the exhaust. With outer space as the "cold temperature" even solid state generators might be the light weight choice for electric power.

Of course. I have no doubt one can lift off liquid H2. My point was there is no need to add that system's weight. You must have a tank full of what will be come the exhaust gas in any case. If that tank holds NH3 it holds considerable more Hydrogen per unit volume than if it hold pure H2. I.e. the smaller, tank needing no super insulation, needing no refrigeration cooling system, etc. will weigh less despite the nitrogen in.

Also that N may give an extra photon thrust with infinite ISP, which protons cannot. I am only guessing that the radiation pressure is small fraction but perhaps not - see my prior discussion - It might be a big help, especially for optical tracking.

I won't comment on ship shape and internal design - need to know its fuel etc first, but tend to agree with your unquoted comment on that.

From my decade of experience in the controlled fusion problem, I am very impressed how much heat energy can be converted into radiation by some not fully ionized atoms in the exhaust plasma. So much so that more than half seriously I suggest that perhaps radiation pressure may be significant part of the thrust - If the engine were not to jet out any mass , only radiation from impurities in the plasma thru cooled quartz window(s) you have an infinite ISP rocket system. I.e. sort of like solar sailing without the need of a near by sun.