MichaelPoole

May 6, 2022

16 hours ago, Spacescifi said:

Although doing so would be more fuel costly then going slower.

This is why. Also, when you need to transport people, you transport people. When you need to colonize moons of Uranus, you transfer people. Drones may get from A to B faster but you are not sending robotical probes, you are sending coloniste. You have a point, partially, If this was an actual Expense type scifi, then human physiology would be a great limit in acceleration especially for low gravity humans.

Except it is not. It lacks the high G, high specific drives of it. In Mnemosyne, as in the real world, high Isp, high thrust drives are rare - most used drives would still classify as "torchships" by modern standards but generally most civilian vessels have accelerations below 0.5 G. Many military vessels can use high accelerations but it **drastically** cuts fuel efficiency. Most of the ships in my settings use fusion drives for which you can increase the thrust by throwing in inert reaction mass (as opposed to fusion fuel) into the exhaust but that correspondingly decreases specific impulse aka fuel efficiency. Most of Mnemosyne ships put their crew in suspended animation for longer voyages also. It is not like "robots" are invulnerable to space dangers either, they need maintenance and special radiation hardened chips which are typically 2 decades behind their consumer counterparts.

I do have a page with some ship designs it in which I will post once I make it Wattspad ready.

5 hours ago, SunlitZelkova said:

One thing though- it is pretty unlikely nuclear war will actually cause a lowering of global temperatures, let alone limited nuclear war described in the 2060s.

Thank for for feedback but according to whom? I do not like the "follow the latest papers" style of hard scifi which pretends to be 100 percent accurate by exactly parroting often low quality scientific papers (which often directly contradict each other) and retconning itself endlessly to be as "real as possible". Nuclear winter is something still considered possible by many scienticists and from what I see on wiki, while a 2018 model predicted little cooling, another model a year after that predicted rather intense cooling, so I take these with a grain of salt. Besides, the cooling in Mnemosyne is far, far lower scale than the old nuclear winter scenarios predicted. Plus, is a long standing scifi and science trope tbh and I like it.

Geoengineering lacks the "humanity accidentally resolved one problem by causing another" vibe I was going for in that part tbh.

Don't get me wrong though, I appreciate the feedback !

May 5, 2022

I updated the setting and posted it on Wattspad:

https://www.wattpad.com/myworks/230084104-mnemosyne-a-portrait-of-the-solar-system-in-the

Used Docdroid for my new version of the Ra planetary system for now as Wattspad does not display the pictures I had in the text:

https://docdro.id/DRcjrYn

June 23, 2020

10 hours ago, SOXBLOX said:

Cool! Thx for the explanation. I look forward to seeing more of this!

Thanks for your feedback . Btw folks, what do you think about the Ra solar system and the planet Satis?

June 22, 2020

7 hours ago, KSK said:

If Mercury to Pluto in a month or two isn’t ‘torchship performance’, it’s close enough in my book.

I mean, it isn't Heinlein style torchship performance which took a trip to Pluto in four days and can do brachistochrone trajectories to other stars, it also depends on what ship we are talking about, not all ships in my settings can do a Mercury-Pluto brachystochrone.

EDIT - Another limiting factor when it comes to acceleration for some modified subsets of humanity is actually biology - for example the Mirandan tweaks preferred gravity/ acceleration is around 0.01 G(!) because that's roughly the gravity of Miranda and other "just large enough to be round" bodies in the Solar system (before you say that this is very limiting, keep in mind this includes the vast majority of Solar system bodies - ultra-low G conditions that would lead to total muscular atrophy and bones crumbling like chalk in modern Earth-living humans are not just tolerated but optimum for them).

This could of course lead to a huge military disadvantage which is why I plan to arm them with sophisticated high G defense drones, it would also fit the... weird relationship I plan for the Uranians to have with the Hegemony, they're supposed to be kind of a "hippy brother" to the Hegemony (I intend them to be descended from the same group of refugees who made the Hegemony but unlike them, these guys didn't take to the path of hate and veangance and make an abandoned, angry AI their leader) but one still needs to defend themselves...and their evil brothers are willing to sell them tech...

Low acceleration also means their ships can be much bigger and more efficient.

June 22, 2020

4 hours ago, SOXBLOX said:

The part about Mercury developing antimatter tech is interesting as well. Also, it seems your ships aren't torchships, right? You said they drift, have hibernation systems, etc. Curious as to why you rejected torchdrive tech...

Most ships can actually do brachystochrone trajectories up until a certain distance, but at a relatively low level of acceleration compared to ships in some sci-fi settings that accelerate at 1 G for months (that being said, compared to current or even near future ships, they absolutely are "torchships", as well as by the wider rather than narrow ProjectRho and Orion's Arm definition). This is fusion tech, for which typical "torchdrive" level of performance would be unrealistic. Also, most ships are variable specific impulse/thrust ratio, meaning some can actually produce bone crushing acceleration, but your fuel tank will run out a lot faster. No ship needs to use Hohmann transfers, remember, brachystrome flip n burn vs Hohmann transfers are 2 extremes - plenty of high energy, fast trajectories available that aren't really brachystrochrone.

I actually put some ship specs here https://www.dropbox.com/s/tx6l95els5bf5j6/ShipdesignsREDONE-WIP.rtf?dl=0 though I didn't put it on Wattspad, will do later. A lot of the time, hibernation is used to save costs on food, oxygen etc... or make tiny craft with little supplies viable (I gotta recalculate how long my best ships took to cross between Mercury and Pluto but it was something like 40-70 days). Sometimes, hibernation is part of a sneaky military strategy - the Persecutor one man pirate (well, privateer, they are legal and state ran craft of the Hegemony) spacecraft are often drifting for months with their pilots in hibernation, pretending to be derelict craft or innocent traders. Many people who smugly declare how there is no stealth in space forget that there are other ways to hide your ship than to be completely invisible (and that actual historical pirate ships had no stealth capabilities but I digress.

June 21, 2020

Thank you for all feedback so far

4 hours ago, KSK said:

The worldbuilding for your mid-27th century Solar system is very interesting too. I like the way you have the Hegemony on the one hand, with all the tensions that they cause and then, on the other hand, Europa is effectively fenced off as a planetary scale national park. It shows both the best and the worst of humanity very well.

Indeed I don't want to make my setting either too grimdark or too Trek-style optimism, though some people might say I lean a bit on the grimdark side, but I'd say not too much. Hell, even the Hegemony mostly left old prejudices behind - even though it its case it replaced them by just not viewing any other group as really people.

June 21, 2020

1 hour ago, SOXBLOX said:

Very interesting! I like the US-China Pact thing. Also, I'd suggest moving the exploration of Ceres closer to the beginning of manned spaceflight in your 'verse.

I gotta admit I was a bit inspired by the CoDominium from Jerry Pournelle's books which was an union of USA and USSR https://en.wikipedia.org/wiki/CoDominium#Formation_of_the_CoDominium I'd say my union is ultimately more likely though considering that beyond surface squabbles both states are capitalist and authoritarian (though China to a far higher degree, don't want to start a political discussion though) and dependent on each other. As for Ceres, note that it's the third visited Solar system body after Moon and Mars - beginning of manned spaceflight in my verse was in 1961 as until present day it's our verse. If anything, I'd say 2090 is optimistic for a first manned Ceres mission.

June 21, 2020

Put it all on Wattspad now too, if you guys prefer that. I'm looking for general feedback:

https://www.wattpad.com/myworks/230084104-mnemosyne-a-portrait-of-the-solar-system-in-the

https://www.wattpad.com/myworks/230086250-the-ra-planetary-system

June 20, 2020

Hello folks, so I'd like to show my worldbuilding project + a planetary system I'd like to eventually incorporate into it. It takes place in the 27th century and is reasonably hard SF, but not "diamond hard". It's a work in progress and the general technological level is advanced fusion/early antimatter drives, strong but not transsapient AI, extensive human genetic tweaking for different conditions is used etc. I'd like to hear some feedback, ask me questions etc. For the reasons of lenght I present it as Dropbox links, keep in mind you don't need to be a Dropbox user or have it installed at all to take a look on it (.rtf is the WordPad format btw).

https://www.dropbox.com/s/si6vhxzbn7yw40g/Mnemosyne-WIP.rtf?dl=0

https://www.dropbox.com/s/tx6l95els5bf5j6/ShipdesignsREDONE-WIP.rtf?dl=0

https://www.dropbox.com/s/b8ozmydqdibb9a9/Satis.rtf?dl=0

Some pictures of the Ra/Satis planetary system:

https://imgur.com/a/mUf47Un

EDIT - I'm not sure this is the right subforum for this but I don't know where else to put it. I'd like to ask admins to please move it to the approperiate section if this isn't the right one.

February 2, 2018

4 minutes ago, SnailsAttack said:

when people in sci-fi movies take their helmets off on other planets with absolutely zero knowledge of any of its atmospheric or biological properties.

that excrements could be composed of 98% nerve gas and space aids for all you stand-up guys know

Now this is a legitimate complaint (through IMHO, this is justified in space opera as most planets visited are civilized in some way and their properties mostly known).

February 2, 2018

[snip]

What's with the ridiculous hate for Interstellar? I'd put it in one of the best movies ever made. "You can make enviroment controlled enclosed spaces on Earth, why go to space?" well making enviroment controlled habitats for a small crew is 1 thing, for whole humanity is other. Yes, it is not quite scientifically accurate, but people here seem to be obsessed with hating it.

Not about Interstellar now, but in general, many people here seem to think that only present day science qualifies as "possible". By that standard, Jules Verne should have written about steam engines, smog and abject poverty, with no airplanes or water purification. And there were many people at that time who would prove to you with elaborate theories and justification why a good living standard for most people is impossible, how the internal combustion engine is impossible, how heavier than air flight is impossible etc. Yes, things like wormholes are speculative, but you are wrong to make claims like "nothing can go through them". First, as of now, they are theoretical, second, metrics that would allow for wormhole travel are allowed by theory: https://en.wikipedia.org/wiki/Wormhole#Traversable_wormholes . Can we make them now? Of course not, but we cannot make ANY wormholes right now.

Now, I'm not saying that stuff like interstellar spaceships flying like WW2 airplanes are realistic, far from that. I am just puzzled by the amount of hate that people here seem to have for "80 percent accurate" fiction. You're the type of people who'd drone on endlessly how the internal combustion engine is a stupid idea and how people could never travel in vehicles whose engines are effectively in a constant state of explosion in the 19th century. It is science FICTION, not a crystal ball, it includes speculative science else it's not science fiction. It may or may not turn out to work, or it may work in a different way (for example Baxter's Manifold series had foldable portable computers by 2010, we didn't get foldable ones yet, but the average smartphone has more power than your average laptop from 2009). Of course, some things are just plainly done, but normal people are not going obsessive over them.

I think some people just enjoy to be "that guy" and instead of using their supposed brainpower to actually improve science they go to online boards to explain why x isn't possible, even if they turn out to be wrong later. It isn't a new phenomena, after all, The Times called airplane research a waste of time and stated rockets cannot fly in a vacuum. An IBM executive stated in 1943 that the world will never need more than 5 computers.

On topic, The Core crosses my suspension of disbelief, and I really like Farscape, which is completely soft scifi, but I like the characters, story, and refreshing lack of technobabble. I would put many ridiculous disaster movies into "the science is too bad" category as well. But overall, if I'm watching a soft scifi series, I honestly don't care about the "scientific accuracy". What mildly irritates me in some space opera is Star Trek style technobabble, for example the endless contradictory statements about Warp Drive - Farscape just says the ships go FTL using "hetch drive", and leaves it at that, without making 3 incompatible Warp factor schemes and complete repurposed bovine waste like the Threshold episode where the crew mutates into salamanders and slugs after going to "infinite velocity".

December 23, 2017

19 hours ago, kerbiloid said:

Hide contents

The total Space-X program is a super-expensive advertisement project of martian rocket-shaped pendants for the Tesla windscreen.

What is that even supposed to mean?

January 29, 2017

Hlasim sa :). Skoda, ze je tu tak malo ludi. Myslel som ze v SR a CR hra KSP viac ludi. Radsej pisme bez diakritiky aby nam vsetky posty zas nepokazila zmena forum softwaru.

On 13. 9. 2016 at 5:05 AM, Vanamonde said:

Over the years and forum software transitions, the title of this thread has become scrambled. Would some nice person supply us with a corrected version so we moderators can edit into the original post? Please specify which language this is, because I'm afraid I do not recognize it.

Thank you, kyklop.

Every post here with diacritics is scrambled, is there any way to make them readable again? And Osel is right, it is a mix through in a sense that some members post in Slovak and others in Czech - the languages are very similiar, but they are not mixed within the posts themselves - Slovaks here post in Slovak, and Czechs in Czech. Both languages are easily understandable to both nationalities, but I will try to make a list of SK posters here so you can restore the diacritics somehow, because some letters are different (Slovak has no ř, ě, ů and Czech has no ľ, ĺ, ô, ä):

Slovak:

Osel, kyklop, Thomassino, Jovzin, EvilotionCR2, me

Czech:

Everybody else here.

January 26, 2017

11 hours ago, KerikBalm said:

We had a forums thread like this before.

The rate at which the atmosphere would last is about a million times less than that....

I have never seen such low estimates. The lowest ones I have seen are in thousands of years which is long for a human. Usual ones are around 10k-100k years, top one I have seen was 100 million.

3 hours ago, kerbiloid said:

Every moon has such atmosphere which it deserves.

_{If I had a 1 money unit every time when they tell me so...}

(Silently watches at a close binary star picture...) Of course, the upper gas layers disturbed by the Earth gravity would mostly dissipate aside, not fall down to the Earth.
But anyway, lunar orbital speed at its upper atmosphere height will be comparable to the heat speed of molecula.

Binary stars and the Earth-Moon system are not really comparable,

January 25, 2017

On 23. 1. 2017 at 6:19 PM, AeroGav said:

The big problem is how do you keep the atmosphere in, without building a roof as others have pointed out.

The earth has higher gravity, and a strong magnetic field, which help to stop the solar wind stripping it away. Given a monstrous power system, could we create an artificial magnetic field for the moon, that'd repel charged particles and protect the atmosphere?

It would only be unstable on geological timescales, no roof needed. I believe it was calculated that it would last like 100 million years.

Quote

- The lunar atmosphere will be permanently being sucked out by the Earth, because it would be thousands kilometers high.

Physics do not work that way.

January 25, 2017

5 hours ago, 78stonewobble said:

Or just that where the solar system formed was somewhat rare in gases, but rich in rocks?

So possibly unlikely, to very unlikely, but not completely impossible?

I don't think it is very unlikely at all considering we already discovered such a planet. Way too much of this is theory, it reminds me of the oceans of oil theory of Venus or how Jovian moons were supposed to be barren cratered rocks before Voyager.

January 24, 2017

3 minutes ago, DoctorDavinci said:

True, however it had no large biological entities onboard ... metals, ceramics and other compunds used in the design and construction of spacecraft can sustain much more stress than us 'squishy' types

You realize it accelerated at milliGees? The thrust it used was less strong than a touch of a feather. I was not talking about the type of "constant thrust" that would involved accelerating half of the way and braking the half, but the ion drive spiral type.

This:

Quote

The Martian doesn't contain an example of a spacecraft that provides constant 1g thrust. The Hermes, the interplanetary spacecraft in The Martian, uses an ion drive to achieve non-Keplerian orbits because it's a very mass-efficient way of doing it, but an ion drive like that doesn't have enough thrust to provide 1g throughout any part of the journey.

I wanted to say Dawn had a similiar system like in the Martian.

January 24, 2017

Is 0.6 percent of perchlorate really such an insourmountable obstacle to you?

https://en.wikipedia.org/wiki/Perchlorate#On_Mars

Quote

The analyses on three samples, two from the surface and one from depth a of 5 cm (2.0 in), revealed a slightly alkaline soil and low levels of salts typically found on Earth. Unexpected though was the presence of ~0.6% by weight perchlorate.

January 24, 2017

On 22. 1. 2017 at 5:39 PM, eloquentJane said:

The Martian doesn't contain an example of a spacecraft that provides constant 1g thrust. The Hermes, the interplanetary spacecraft in The Martian, uses an ion drive to achieve non-Keplerian orbits because it's a very mass-efficient way of doing it, but an ion drive like that doesn't have enough thrust to provide 1g throughout any part of the journey. The Hermes included centrifuges to simulate gravity, and would not have them if such a high acceleration could be provided by the engines for the entire journey. Additionally, the interplanetary transfers in The Martian took months to complete. With constant acceleration of 1g halfway to the destination and then the same in the other direction for the rest of the journey, getting between Earth and Mars would take mere days. However, such a maneuver would require the expenditure of enough fuel to equal hundreds of kilometers per second of delta-v, or possibly even millions of meters per second depending on how far apart the two planets are. This isn't yet realistically achievable even with VASIMR engines. The only possible way it could be done based on currently proposed technology is with fission/fusion propulsion, but even that would be at a push (and it would be much more efficient to use a high-energy transfer and stick to Keplerian orbits, and just add a centrifuge or two onto the spacecraft to simulate gravity).

This way of inter-system travel was already used by the Dawn probe to Ceres and Vesta btw.

January 24, 2017

1 hour ago, kerbiloid said:

Btw, as perchlorates mean chlorine, it's not only poisonous, but also corrosive.

Now, perchlorates are corrosive (through I don't even know if they were even conclusively proven to exist in the Martian soil), but "perchlorates mean chlorine", what? Are you implying that a molecule with chlorine it it = chlorine? Salt also "implies chlorine", besides, I don't think a base structure made of titanium or something will be ruined by something found in fertilizer?

January 24, 2017

The problem with "theoretical models" is that they are often wrong. Don't get me wrong, they are useful tools, but nothing more. In this case, a planet is proven to have a mass, radius and density that mean it lacks a huge hydrogen envelope, yet is as massive as Uranus, so I am gonna believe the empirical evidence. There were plenty of models showing Pluto must be geologically dead too.

January 24, 2017

On 22. 1. 2017 at 5:24 PM, ColKlonk2 said:

Not only that, the ground is also poisonous, so going underground is not a solution.

Take it or leave it, we're not going to Mars anytime soon, no matter what Elon Musk and others like you to believe

Why would the ground being poisionous prevent anything? Nobody is going to eat the soil.

January 24, 2017

What struck me when reading about the "super-Earth" type of exoplanet is that many people seem to assume these planets are either like terrestrials in our Solar system, or mini-Neptunes/Gas Dwarfs. Reading more about this struck me as I realized an "in-between" exoplanet type probably exists and many of the superterrestrials discovered to this date. These two papers https://arxiv.org/abs/1606.08088 https://arxiv.org/abs/1311.0329 are rather enlightening on this matter. For example of what struck me:

Quote

On the other hand, if we assume a more typical low-mass planet with a 5 M Earth-like core, then to be 2.0 R it would need 0.5% of its mass in a H/He envelope. This may not sound like much, but it corresponds to 20 kbars of hydrogen and helium, 20× higher than the pressure at the bottom of the Marianias Trench. Moreover, the temperature at the bottom of such an envelope would be 3000 K, even for ages of several Gyr. We believe that such a planet is more properly classified as a sub-Neptune. As a result, 2.0 R is more of a quite hard upper limit for the size of a envelope-free super-Earth and most of the planets between 1.75 and 2.0 R are likely to be H/He rich sub-Neptunes.

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Assessing the impact of thermodynamics for the case of Kepler 11b is more difficult, because the expected steam envelope is not modeled. If the gas pressure and temperature at the bottom of the envelope were, respectively ≈ 1 GPa and ≈ 1000 K, then Rc would be 5% larger than the value listed in Table 4

Also, on Wiki

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Whether or not the primitive nebula-captured H/He envelope of a super-Earth is entirely lost after formation also depends on the orbital distance. For example, formation and evolution calculations of the Kepler-11 planetary system show that the two innermost planets Kepler-11b and c, whose calculated mass is ≈2 M_⊕ and between ≈5 and 6 M_⊕ respectively (which are within measurement errors), are extremely vulnerable to envelope loss.^[68] In particular, the complete removal of the primordial H/He envelope by energetic stellar photons appears almost inevitable in the case of Kepler-11b, regardless of its formation hypothesis.

This basically suggests that there is a class of planet that:

- has a solid or molten lava surface

- at the same time, has an atmosphere that is H/He rich, and while FAR lighter than Neptune (for this reason I would say calling them sub-Neptunes is not really accurate as the pressure and temperature, as high as they are, are orders of magnitude lower than those in the water mantle of Neptune), still much denser, hot and crushing than Venus (pressure on the surface of Venus is 9 MPa, the pressure on a hypothetical 5 ME/2 Earth radius planet is 2 GPa or 222x as much as on Venus, one of the theoretised pressures for Kepler 11b is 1 GPa). Now, these planets have some unimaginable surface conditions, but unlike Neptune, you can still say there is a surface there, and to compare, the pressure at the top of the water mantle of Neptune is 200 GPa or 100-200x as much as at the surface of these planets (the temperature at the top of Neptune's mantle is 3000 K). In case of Kepler 11 b, this atmosphere is likely to be steam/supercritical water (a sort of an inbetween phase between liquid and gas).

So, basically, there are probably many planets that are not really terrestrials as we know them from our Solar system, but not ice dwarfs like Neptune let alone gas giants like Jupiter. Of course, if we ever get there, exploring them would be the ultimate challenge of building landers, but the chemistry and processes (as they might feature processes we know from Neptune along with terrestrial geological phenomena like volcanoes) might be very fascinating. 55 Cancri is also sending some rather interesting signs that it is probably something we have not seen yet:

http://www.space.com/32416-super-earth-55-cancri-e-super-hot-weather.html

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To help solve the mysteries of 55 Cancri e, astronomers used NASA's Spitzer Space Telescope to monitor infrared emissions from the exoplanet for 75 hours total during the summer of 2013. The resulting thermal map revealed a strong difference in temperature between the planet's dayside and nightside.

55 Cancri e is tidally locked, meaning it always keeps the same face pointed at its star. On the dayside, temperatures on 55 Cancri e can reach about 4,400 degrees Fahrenheit (2,427 degrees Celsius). On the nightside, temperatures can dip to about 2,025 degrees F (1,107 degrees C).

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The nightside's relatively cooler temperatures suggest that 55 Cancri e does not possess a thick atmosphere that could carry heat from the dayside to the night side, Demory said. It also suggests this planet is not covered with a large envelope of water, ruling out the possibility that supercritical fluids envelop 55 Cancri e, Demory added.

About halfway between the dayside and the nightside, the researchers discovered that 55 Cancri e possesses a hotspot. They suggest this hotspot might be due to lava flows, and because the planet is hot, this lava may flow better than it does on Earth, behaving more like water does at room temperature and less like solid rock.

http://news.nationalgeographic.com/2015/05/150506-volcano-planet-space-cancri-astronomy/

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Volcanism, however, could also dim the planet, and the astronomers consider that to be more likely. “We know it happens all over our own solar system,” says Madhusudhan. “We see evidence for it on Venus, Mars, [Jupiter’s moon] Io, all kinds of solid bodies. That’s the natural explanation.”

The idea is that powerful eruptions would spew massive plumes of gas and dust into the planet’s atmosphere, masking the hot surface and making the planet appear cooler. The eruptions would have to be more powerful than anything ever seen, but there's a chance that's possible. 55 Cancri e orbits so close to its parent star, with a “year” lasting just 18 hours, that it it could be flexing under tidal forces generated by the star’s gravity. The heat from that flexing could keep the planet’s interior molten, which might drive the eruptions.

Yet, despite the temperature differences suggesting a thin atmosphere, one was indeed discovered, and it is a hydrogen/helium one with a mix of... probably hydrogen cyanide:

https://www.spacetelescope.org/news/heic1603/

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Using observations made with the Wide Field Camera 3 (WFC3) on board the NASA/ESA Hubble Space Telescope, the scientists were able to analyse the atmosphere of this exoplanet. This makes it the first detection of gases in the atmosphere of a super-Earth. The results allowed the team to examine the atmosphere of 55 Cancri e in detail and revealed the presence of hydrogen and helium, but no water vapour. These results were only made possible by exploiting a newly-developed processing technique.

“This is a very exciting result because it’s the first time that we have been able to find the spectral fingerprints that show the gases present in the atmosphere of a super-Earth,” explains Angelos Tsiaras, a PhD student at UCL, who developed the analysis technique along with his colleagues Ingo Waldmann and Marco Rocchetto. “The observations of 55 Cancri e’s atmosphere suggest that the planet has managed to cling on to a significant amount of hydrogen and helium from the nebula from which it originally formed.”

So here is some conflicting evidence. On one hand, the large temperature variations and possible evidence of volcanic ash blocking emissions suggests a relatively thin atmosphere. On the other hand, spectral evidence suggests a hydrogen/helium atmosphere. On one hand, the planet is 8.63x as massive as Earth, so it could have gathered a H2/He envelope. On the other hand, it is on an extreme torch orbit, worse than Kepler 10b and Corot-7b, which have practically no atmosphere, according to transit data. Yet this one has, yet no H2O was detected (while for a Neptune like planet it is the major component), drastic temperature variations, possible volcanism... yet it apparently retained some light gases. The radius is 2x of Earth, mass 8.63x of Earth, so it is much denser that the 5 ME/2 Earth radius hypothetical "borderline" planet. That would suggest it has a hydrogen atmosphere, but one with a lower surface pressure than 2 GPa. Basically, what I am saying is that some exoplanets might have hydrogen/helium atmospheres that have high pressures, but have not retained the extensive hydrogen envelopes like Neptune or Jupiter. I think planets like this might be frequent in torch orbits, as the gravity holds SOME of the light gases, but not everything. The result might be an unholy Venus/Neptune hybrid with features common to both ice giants and terrestrials.

But this does not end, apparently, some planets managed to grow to Neptune like masses while being so dense that they are clearly fully terrestrial and free of any H/He envelope:

https://www.eurekalert.org/pub_releases/2014-06/hcfa-afa053014.php

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Astronomers announced today that they have discovered a new type of planet - a rocky world weighing 17 times as much as Earth. Theorists believed such a world couldn't form because anything so hefty would grab hydrogen gas as it grew and become a Jupiter-like gas giant. This planet, though, is all solids and much bigger than previously discovered "super-Earths," making it a "mega-Earth."

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Kepler-10c was known to have a diameter of about 18,000 miles, 2.3 times as large as Earth. This suggested it fell into a category of planets known as mini-Neptunes, which have thick, gaseous envelopes.

The team used the HARPS-North instrument on the Telescopio Nazionale Galileo (TNG) in the Canary Islands to measure the mass of Kepler-10c. They found that it weighed 17 times as much as Earth - far more than expected. This showed that Kepler-10c must have a dense composition of rocks and other solids.

"Kepler-10c didn't lose its atmosphere over time. It's massive enough to have held onto one if it ever had it," explains Dumusque. "It must have formed the way we see it now."

The planet likely has a superheated ocean of water, but no helium or hydrogen:

https://en.wikipedia.org/wiki/Kepler-10c

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Kepler-10c has a mass of 15–19 Earth masses. With a radius only 2.35 (2.31 to 2.44) times that of Earth (and so a volume 12–15 times that of Earth), and a density higher than Earth's (6–8 g cm−3), it is unlikely to contain significant amounts of hydrogen and helium gas. Outgassed or accreted hydrogen-rich atmospheres would have been lost over the 10.6 billion-year lifetime of the Kepler-10 system. Instead, the composition is likely to be mainly rocky, with a water fraction of 5–20% by mass. The bulk of this water is likely to be in the form of high-pressure "hot ice" phases.

However, there are also apparently planets as light as Earth with an extensive light gas envelope:

http://www.nature.com/news/earth-mass-exoplanet-is-no-earth-twin-1.14477

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Astronomers have discovered an extrasolar planet with the same mass as Earth, but the resemblance ends there. Not only is the planet too warm for liquid water to exist on its surface, but it also has a radius 60% larger than Earth, suggesting a vast, puffy atmosphere of hydrogen and helium.

https://en.wikipedia.org/wiki/Gas_dwarf

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The smallest known extrasolar planet that is likely a "gas planet" is Kepler-138d, which has the same mass as Earth but is 60% larger and therefore has a density that indicates a thick gas envelope.

So, apparently, planets can be Neptune sized and terrestrial, Earth sized and with a huge gas envelope, or anything in-between. This is also why I don't really like when people throw terms like "super-Mars", "super-Earth", "super-Venus", or "super-Mercury". I think there is a very big factor that determines what a planet is like and that is - how exactly did it form and in what conditions. A planet is more that its orbital parametres.

Sorry if this got too long. Just had an urge to air my thoughts and stimulate a discussion. I personally feel that the obsession of astronomy about finding "Earth-like" planets limits our horizons and knowledge. I am fascinated by bizzare planets, even those that probably have no life (through the soup like atmospheres of "borderline" planets might have surprises waiting for us...), and think apart from the joy of knowledge and aesthetics (when we eventually manage to photograph them) they might eventually offer a lot to humanity.

EDIT - In addition, planets like the ones with a big, but not quite ice giant atmosphere (like the "sub-Neptunes" mentioned in the paper) might offer life bearing conditions if they are rogue planets:

https://en.wikipedia.org/wiki/Rogue_planet#Retention_of_heat_in_interstellar_space

Quote

It is calculated that, for an Earth-sized object with a kilobar atmospheric pressure of hydrogen, in which a convective gas adiabat has formed, geothermal energy from residual core radioisotope decay will maintain a surface temperature above the melting point of water.[15] Thus, it is proposed that interstellar planetary bodies with extensive liquid-water oceans may exist. It is further suggested that these planets are likely to remain geologically active for long periods, providing there is a geodynamo-created protective magnetosphere, with possible sea floor volcanism providing an energy source for life.[15] Thus humans could theoretically live on a planet without a sun, although food sources would be limited. The author admits these bodies would be difficult to detect due to the intrinsically weak thermal microwave radiation emissions emanating from the lower reaches of the atmosphere, although later research suggests that reflected solar radiation and far-IR thermal emissions may be detectable if such an object were to pass within 1000 AU of Earth.

January 24, 2017

On 19. 1. 2017 at 4:57 PM, p1t1o said:

Whatever combination works best with KSP physics.

It could even have full-blown planets orbiting it, SOIs would be much smaller, yes I can see it being an interesting environment to add to KSP.

Question: what is the luminosity of a neutron star like? Would it shine like a sun or be more a dull glow? Or even dark?

The surface of neutron stars is millions of degree high, so a bright dot.

By the way, try Universe Sandbox 2. A pulsar at a range of several thousand kms will not just tear humans apart, but super-Jupiter sized planets will start to break apart in seconds. Earth would be literally destroyed in seconds by the heat and tidal forces, when I put it like 10 000 km from the Crab pulsar it went up to 20 000 degrees Celsius in a few seconds.

If you were in a spaceship really close to it, you would probably experience the fastest death possible for a human being. Your neurons would be plasma before you registered anything.

That being said, due to their small size, they are not unthinkably bright. PSR B1257+12 for example has planets around it and a luminosity of 5.2 Solar, much of which is gamma and X rays. If Kerbol was in a binary system wirh the pulsar being in the Oort cloud, it would probably not be disruptive and would be seen as just a random suspiciously bright blue star in the sky. At that distance the ionising radiation would be very weak too, courtesy of inverse square law. The reason why it is more destructive than the Death Star from close up is because it would be like approaching Sun's core at a lesser distance than between New York and Tokyo.

That being said, I am not sure how complex life on Kerbin survived the supernova explosion that made this pulsar.

January 22, 2017

To people saying stuff like "Super-Mars", I seriously doubt a superterrestrial planet orbiting outside the "habitable zone" will be like Mars at all, the whole thing that makes Mars a cold, uninhabitable desert is the low mass and associated volatile and atmospheric loss. A large planet recieving Mars-like heat might even be warmer than Earth, if it has a thick atmosphere, and I think we should shift the whole habitable zone outwards for higher mass terrestrials. Hell, EARTH might have been habitable if it was on a Martian orbit - it might have been covered by ice, but the ice would be a few meters thick, like arctic ice, not Europa ice kilometers thick, easily allowing for sunlight shining through and complex life. Some food for thought http://www.worlddreambank.org/L/LYR.HTM http://www.worlddreambank.org/O/OISIN.HTM . Also, consider 300 million years ago, when the Sun was slightly weaker, the Earth was covered by a carboniferous forest and had more O2 and CO2 in the atmosphere - it might be that planets orbiting around the edge of the traditional habitable zone are actually the most tropical ones, as that allows a lot of CO2 in the atmosphere. Earth's biosphere has been gradually reducing atmospheric CO2 as the Sun is brightening (apart from man, who increases it), and eventually, what will kill all plants of the present type on Earth will not be heat, but CO2 starvation.

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