Sunday, August 25, 2019

Wish list for space video games.

Kerbal Space Program

The Kerbal Space Program has demonstrated video games can be a very effective teaching tool.

It used to be very frustrating trying to talk about orbital mechanics. Use a word like "perigee" and eyes would glaze over as the audience tunes out.

But now there are many KSP players who are comfortable with terms like The Oberth Benefit, Bi Elliptic Transfers and other what use to be arcane, esoteric notions.

I'm hoping for more scientifically accurate games to make their way into pop culture.

Wish Number 1: Shotgun N-body simulations

Readers of this blog may know I'm a little obsessed with EML2 (Earth Moon Lagrange 2).

Many of my delta V numbers from EML2 assume dropping from EML2 using the Farquhar route and then insertion to a transfer orbit when moving ~11 km/s at perigee.

The Farquhar Route

However Farquhar's well done graphic is a simplification. A ship departing from from the EML2 region would not depart from a point. Rather it would drop from a halo or lissajous orbit about EML2. There are a multitude of possible orbits in this region.

Dropping from different parts of a halo orbit will result in different longitudes and latitudes for a perigee. And if you're doing a perigee burn for injection to a Mars transfer orbit, you want to be at a specific location and heading a specific direction when making your burn. 

Years ago Tom Powell helped me build a shotgun Java n-body sim from Bob Jenkins' code. blast many pellets in the general direction of your target. See which pellets pass closest and then narrow the shotgun blast.


Above is an attempt to show the shotgun concept. A fellow going by the handle "Impaler" was annoying me in a space forum. First I blast the varmint with broad scattering of buckshot. Then I more thoroughly pepper his backside by narrowing the blast between pellets 5 and 7.

By successively narrowing buck shot from earth to EML2 I found this route 3.1 km/s route from LEO to EML2:


The sim included earth, moon and sun. A lunar swing by boosts apogee on the way out. And then sun's tidal influence serves to raise perigee to EML2 altitude.

There are some serious limitations to my shot gun sim. There are only a few very limited scenarios that Tom Powell and I set up, very specific times and places. I would like to be able to have the user get location and velocity of a body at any time. I under stand there's software called SPICE that does this but I don't know how to use it.

Also JAVA seems obsolete. It's very difficult for me to use my own pages any more.

And my sims cans only specify the initial burns. Once you have a transfer path to a location it'd be nice to be able to do burns to park at that location.

I would use such a tool to learn how to move between different loosely bound lunar orbits.

Perhaps dropping from one EML2 halo orbit during a launch window wouldn't put the perigee in the right place for an injection burn. How much delta V would it take to move to a more favorable halo orbit?

Supposedly there are heteroclinic paths between halo orbits EML1 and EML2. A shotgun sim might help a player find these paths.

Halo orbits about EML1 and EML2 are part of a family of orbits that also include Near Rectilinear Halo Orbits (NHROs). If a lunar gateway is placed in an NHRO, it'd be fun and useful to explore different lunar orbits you could enter from an NHRO.

Wish Number 2: Tunneling on small bodies

For planets and large moons we are limited to exploiting only the thin outer shell of a body. Heat and pressure prohibit us from tunneling deeply.

But the entire volume is accessible for a small body.

If we could exploit the entire volume of Ceres, the dwarf planet could make Trantor look like Dogpatch.

I am hoping some planetary scientists and geologists could build tools to guesstimate how deeply we could tunnel given a body's surface temperature, radius and mass.

Wish Number 3: Tensile towers on small bodies

Also known as space elevators.

I'd be so happy to see a world building game use something like Wolfe's spreadsheet to examine effort and materials needed for various elevators. The user could input tensile strength, planet's angular velocity and body mass to examine various scenarios.

For example given Ceres' high angular velocity and shallow gravity well, Ceres synchronous orbit is only 706 kilometers above Ceres' surface. Materials needed for a Ceres or Vesta elevator are only a tiny fraction of what a Clarke Tower from earth or Mars would need.

Besides elevators from synchronous orbits it would also be good to enable users to build from planet-moon L1 and L2 points. 

The Mars Phobos and Mars Deimos are the moon elevators I like most. But elevators from L2 or L2 are usable in any family of tide locked moons.

Various tethers enabling ZRVTOs between Saturn's moons.

A gas giant's family of moons with tethers could be a rich setting for dramatic stories.

Hohmann trip times and launch windows between moons are on the order of days and weeks so it'd be possible to have a fast paced story without resorting to implausible engineering.

Dramatic situations might include missing a tether catch and being trapped in an orbit that won't rendezvous with a  tether catcher until the passengers have died from using up air, food or water. Or terrorists could sever a tether. There are many possibilities.

Wish Number 4: Compressive towers on small bodies.

Given lower gravity it's possible to build taller structures even given constraints imposed by a material's compressive strength. Likewise, sky scrapers are less plausible if a body has greater surface gravity.

I'd like the user to be able to specify a material's compressive strength and body gravity to get maximum plausible height for structures.

This would be especially useful for elevators between mutually tidally locked bodies like Pluto and Charon. Compressive towers built from the surfaces of Pluto and Charon could extend a fair distance towards Pluto-Charon-L1 and the also the Pluto Charon barycenter. This would considerably reduce the stress on the elevator and thus reducing the mass of the materials needed.

Wish Number 5: Thermal management.

This section dded on 9-8-19 on the suggestion of Winchell Chung and other thoughtful readers. There's three thermal management subjects I'd love to see a game address.

Limits to population growth

Earlier I mentioned a fully exploited Ceres volume could be a megapolis that makes Trantor look like Dogpatch. In the comments below Jim Baerg noted big populations generate heat. How would a growing population dump heat?

A good world building sim would take thermal management into account as a barrier to population growth.

Stealth

Infra red signature could make military craft visible. A topic Chung talks about in his Atomic Rockets page.

Rocket propulsion.

Nuclear power electricity generation for ion propelled rockets would generate considerable waste heat. Dumping waste heat requires big radiators which make for a poorer power source alpha. There are other heat sources that need radiators to dump waste heat. These should be counted when calculating mass requirements for a space ship.


Any other ideas?

Well made multi user games could be a way to educate as well as stimulate interest in space exploration. If a reader has any other suggestions please comment. I screen comments for spam but I eventually post what I believe are worthwhile comments. It's unlikely an actual video game developer will ever read these but there's no harm in day dreaming.






26 comments:

Jim Baerg said...

"But the entire volume is accessible for a small body."

But that may be irrelevant to how many people can live there. There will be a certain minimum amount of heat generated by each human the the required life support. That heat will need to be radiated away. So to use all of eg: Ceres for human living space it would need to be dismantled & made into zillions of eg: O'Neill cylinders.

Nydoc said...

I think Kerbal Space Program can do most of these things. There are community-built add-ons including ones that simulate tensile physics. There is a whole community of folks who can help you to install mods and answer your questions. This will often include the developers themselves.

For a more realistic Kerbal experience I would suggest getting the Real Solar System (RSS) mod and the Principia mod for N-body physics. There's a great team at Private Division writing KSP2 right now so I'm very optimistic that we will see even better mod support in the future.

Hop David said...

Nydoc, happy to hear about the KSP add ons that simulate tensile physics. In the RSS mod have they extended elevators from Phobos? — That's one of my favorite scenarios.

I've heard about the Principia add on that simulates n-body physics. My complaint is that it's time consuming to find a route. I don't know of a way to predict trajectories in n-body scenarios. So the best way to find a route (so far as I know) is trial and error. And shotgun sims are a way to quickly do many trial and error scenarios and refine your parameters as you progress.

The outer regions of our moon's Hill Sphere: EML1 and EML2, Near Rectinear Halo Orbits, the heteroclinic pathways between these, -- I believe this realm will become a very useful region of space. Shotgun sims could quickly give users a feeling for navigating this space. An army of users comfortable with moving about the outer regions of the moon's Hill Sphere would be a great asset in an effort to open the solar system as a frontier.

Loren Pechtel said...

Sorry this is rather off topic but I found a paper I think you would be very interested in and I see no other way to contact you: https://arxiv.org/abs/1908.09339

A lunar space elevator with current materials--and extending down to about geosynchronous height (but far below orbital velocity.) Considerable fuel savings over going all the way by rocket and given the tyranny of the rocket equation that really adds up.

gbaikie said...

--Wish Number 4: Compressive towers on small bodies.

Given lower gravity it's possible to build taller structures even given constraints imposed by a material's compressive strength. Likewise, sky scrapers are less plausible if a body has greater surface gravity.

I'd like the user to be able to specify a material's compressive strength and body gravity to get maximum plausible height for structures.--

It seems you could have pretty tall structures in the Atmosphere of Venus. Roughly because things can float. Or if don't want to go into space, in Earth's ocean one could make very tall structures. So if had section of cylinder filled with air and same pressure as water depth, there is little stress, though the taller one compartment of air is, it give more stress. And you have the force of buoyancy to deal with- but that's not much of problem- if add enough mass so equals the displacement of the water.
Of course all different atmospheric pressure is a problem if you humans are moving about with this structure.

But getting more back to topic, you can use compressed air in vacuum environment {space} to counteract the force of gravity which you trying to overcome with a material's compression strength, though works easier within atmosphere or ocean {though space doesn't have any wind or currents to deal with}.

Hop David said...

Great suggestion Bbalkie!

Compressive towers could also make a big difference on low gravity elevators like from Ceres or between Pluto and Charon. If a large portion of an elevator's "foot" could be a compressive tower, that reduces stress on the part that needs tensile strength. And since the feet are in the steepest part of the gravity, that's what really jacks up an elevator's taper ratio.

gbaikie said...

Regarding:
"Years ago Tom Powell helped me build a shotgun Java n-body sim from Bob Jenkins' code. blast many pellets in the general direction of your target. See which pellets pass closest and then narrow the shotgun blast."

I am interested in planetary trajectories which aren't hohmann.
An example, is if in LEO orbit, 400 by 400 km, and shoot a bullet up or down.
It seems if point a gun at "middle of earth" {or straight down] the bullet should hit the Earth. It also seems possible if aim straight up, the bullet could hit Earth. But if misses Earth the orbit should be both higher and lower than 400 km above Earth surface [or an elliptical orbit] And we could assume bullet travels at 1000 m/s. {Though also can consider higher velocities such as 2 or 3 km/sec].
If shoot bullet straight ahead or straight behind the path of orbit, that would be hohmann transfer trajectory, and any other direction, isn't. And the most efficient {requiring least amount of added velocity] hit earth's atmosphere or go to highest orbit, is to use hohmann.
Now shoot bullet at 1 km/sec in direction of orbit, it will raise the elevation of the orbit and it will come back to the 400 km elevation- at perigee- {and going 1 km/sec faster at the 400 km elevation}.
If shoot the bullet straight up {or 45 angle up {{either forward or back}}] the orbit will go lower than 400 km {and higher than 400 km}. And it's the issue that it cause lower orbital elevation, the thing, I think is important.
It's important because what I want to do is planetary trajectory to Mars in which the return falls closer to the sun than Earth orbital distance from the Sun.
Or starts at Earth orbital distance from Sun and goes to Mars orbital distance and then returns to say, Venus orbital distance from the Sun.

from Earth Moon is full. From LEO one increases velocity to say 16 km/sec, and going the direction of a trajectory which will pass within say 10,000 km of the Moon.
And seems to me it's going to go further from Sun than Earth orbit and return to orbital distance closer to sun than Earth's orbit.
Of course, instead if one applies the Delta-v in direction of earth's orbital path {hohmann transfer], the trajectory with that much velocity will be a solar escape [or least get to Jupiter distance].

But in terms of spacecraft, one start at high earth orbit which highly elliptical with perigee of 200 km or should be going around 10 km/sec at perigee. Musk's Starship fully fueled, and uses about 5 km/sec delta-v of that rocket power at perigee. And with Oberth effect should be total 16 km/sec {or more}. {Apparently Starship is being designed for 6.7 km/sec of delta-v from LEO or from LEO fully fueled- it can land 100 ton payload on lunar surface.

So, it is hohmann type transfer from Earth to Moon {except it's fast flyby of Moon} but in terms of leaving Earth Hill Sphere or in terms hohmann planetary trajectory, it's not a Hohmann. Or it's perpendicular to Earth orbit around the Sun.**
And idea is, if it's given enough delta-v, it resembles something like a Venus to Mars hohmann transfer orbit.
For purpose of getting from Earth to Mars quicker {by travelling a shorter distance as compared to Earth to Mars hohmann transfer}.

** It's not "really" perpendicular, but as one pasts the Moon, the Moon and Earth will be between you and the Sun. And you would be flying thru Earth/Moon L-2 and Earth/Sun L-2.
Or if draw diagram of solar system, Venus to Mars hohmann trajectory crosses Earth orbital path at angle around 30 degrees.

Loren Pechtel said...

@gbaikie: In your scenario you won't hit the center of the Earth but I think the bullet gets destroyed in fire anyway.

Note that in terms of efficiency one never wants to go in the wrong direction unless it's to make a gravity maneuver. It takes less energy to go from Mars to the Earth than to go from Mars to any point closer to the sun than Earth. With manned spaceflight you might choose such a trajectory anyway because it could be faster or because you're not at the right time for the minimum energy transfer. The delta-v costs have a major tendency to skyrocket anytime you do less than the best course, though.

One suggestion for playing with such things: Kerbal Space Program models such things well enough. You'll need the mod that provides Earth's solar system, I forget what it's called.

gbaikie said...

"In your scenario you won't hit the center of the Earth but I think the bullet gets destroyed in fire anyway.

Note that in terms of efficiency one never wants to go in the wrong direction unless it's to make a gravity maneuver. "

Hohmann is most efficient.
Yes, a gravity assist is not a hohmann trajectory.
And gravity assist allows one get somewhere faster {because it's not hohmann} though gravity assist also transfers energy {can slow or go faster- a way to gain delta-v}.

And I am interested in getting to Mars quicker {or get anywhere faster than one can get with hohmann transfer]. Currently we are getting quicker to Mars, because one adds elements which are not hohmann transfers {Patched conic}.
Any way to get to mars faster is not using a hohmann transfer. Whether ion, nuclear rockets, solar sailing, etc.
And people often associate going to Mars faster, by using a hohmann transfer which might be a hohmann transfer which would reach say Jupiter, but as gets near Mars orbit distance, one brakes, or say aerocapture, hitting Mars at high velocity and with atmosphere to brake.
This is NOT what I am taking about.
I am talking about a trajectory which travels a significantly shorter distance to get to Mars, as compared to Mars hohmann or even shorter distance than "Jupiter type" hohmann which slow down at Mars.

gbaikie said...

I shorten post, as it would not post. Adding rest:

Another often mentioned fast way to get to Mars is using "some kind of rocket" which can accelerate at constant 1 gee acceleration for halfway to Mars and turn around slow down the remaining distance at constant acceleration of 1 gee. That is also non hohmann transfer- and also not what I am talking about. But one could say it's more similar {to what I mean] than compared to hohmann or "Jupiter type" hohmann.
One way it's similar is it's "old school", or it the way one would imagine to get to Mars, before the idea of hohmann transfer was "invented" or discovered: "It was invented by a German scientist in 1925 and is the most fuel efficient way to get from one circular orbit to another circular orbit"

https://tinyurl.com/yaank2x6

Hohmann transfer is neat invention, but I want faster way to go Mars. And any faster way one can imagine, is not a hohmann transfer.
And non hohmann transfers are done, any time one using a ion Engine or any low thrust engine. Though one sort do a hohmann transfer, with low thrust if use multiple orbit and only fire the ion engine at the perigee the orbit- and the shorter the time of thrust the more it's like a hohmann transfer. But most Ion engine uses have constant thrust time of hours and days/weeks {or that is a not a hohmann transfer}. Or said differently Ion is great rocket, but one normally do not does get the efficiency one can get with hohmann transfers. Same applies to nuclear rockets which have lower thrust than one can get with chemical rockets. Or roughly if you like nuclear rockets, then you not going to use hohmann transfers.
I am a not fan of nuclear rockets, unless it's a Orion nuclear rocket, and also "like" the crazy, saltwater nuclear rocket- see, Zubrin madness.
And I think we get to Mars fast without nuclear rocket or ion rockets. And a major element of doing this, is related to not starting the trip to Mars from LEO.
Start from high earth, and/or a highly elliptical orbit with perigee at low orbit distance.
Or you could/can start in LEO, then make a highly elliptical orbit, and then when you return back to being near Earth, you then go to Mars. {{but a highly elliptical earth orbit, is a high earth orbit}}

"It takes less energy to go from Mars to the Earth than to go from Mars to any point closer to the sun than Earth. "
Yes, but it's shorter distance in terms of hohmann transfer, to go from Venus to Mars, than from Earth to Mars.
And what talking about is getting to, a Venus to Mars hohmann transfer, but starting at Earth.
Or it's an even shorter distance to Mars as compared to Venus to Mars hohmann transfer.

And yes, it takes more energy, to get to this Venus to Mars hohmann from Earth distance, as compared to hohmann transfer for Venus to Mars and obviously a lot more than Hohmann transfer from Earth to Mars. And more energy than Earth to Mars hohmann + patch conic transfer.
Plus I want to do Venus to Mars trajectory starting from Earth: Plus add to Venus to Mars hohmann, a patched conic {shorten distance even more] And that more energy than without the patched conic.
This of course only applies to crewed spacecraft.
Or sent cargo/or no crew payload, using Earth to Mars hohmann or with patch conic added to it {shorten time to about 7 months rather than 8.4 months}. Or send non crew, using ion engines from high Earth orbit, to Mars. {with ion engines, it doesn't help much to do elliptical orbit with low perigee- so you can send cargo from Earth L points to Mars L-points}.

gbaikie said...

Well, that seemed to work.
Anything else...hmm:
"With manned spaceflight you might choose such a trajectory anyway because it could be faster or because you're not at the right time for the minimum energy transfer. The delta-v costs have a major tendency to skyrocket anytime you do less than the best course, though."

Well I don't think it skyrockets beyond the capability of chemical rockets.
And by making a shorter trip to Mars with crew, one has other things which add efficiency.
What suggesting is for NASA to plan on getting it's crew to Mars in 3 month or less.
Such a shorter trip would be better for crew morale.
One can get less GRC radiation. Which a believe will major barrier for sending crew to Mars- mainly due to "political" aspects of planning on causing astronauts to get higher career level of radiation.
I think trying to get crew to Mars as fast as possible, will have less political Resistance.
And I think the highest cost of Mars mission is not sending crew {whether slow or fast} rather it's the cost all the other stuff needed to support/enable crew mission.
All the measures need to provide safety and "peace of mind" to crew, includes mission abort options and options related to numerous possible medical emergencies. And you have all this stuff, at one end or the other and seems shortening the transit time {where there no means of being able to anything but continue until you reach Mars {or back to Earth} would reduce mission risk.
Anyhow, to do this, what needed is to get more rocket fuel to earth orbit.
Now, SpaceX's Starship is not designed to do this, but it seems capable of doing it. And it seems to be an overkill to do it. Starship is designed to send 100 people/100 tons to Mars surface from LEO. And it can do this because it's designed to refuel in orbit.
For this fast transit I am talking about, you don't need the 100 tons or 100 crew, but needs to be refueled in high orbit, should allow it send small crew plus overkill of stuff, and should allow to get to Mars in 3 months or less. And cost per seat should 50 to 100 million per seat- or roughly what Russia charge per seat to get to ISS. And another 50 to 100 million per seat to return crew from Mars orbit to Earth surface [in short time period- though I think getting crew fast to Mars from Earth is more important then Mars to Earth].
And this is in context, of Manned Mars exploration program of yearly budget of 4 to 5 billion per year.
And I think stay time on Mars, should goal of about 4 years- or crew going faster to Mars is small part of entire yearly Mars budget. Or somewhere around 100 million per Mars crew per year- a bit less than current crew cost of ISS per year.

gbaikie said...

Another thing about NASA fast explorational crew to Mars is you might just do this for first crews to Mars.
One aspect of going to Mars is the long term effect of microgravity on the Crew, will affect their physical ability.
Or if you return from ISS, one should not drive a car for about 1 month. Maybe some crew could safely drive within a week, but I believe 1 month is the "general rule".
So with first crew to Mars, one want them to be in a better physical condition, when they land on Mars and travel to base, AND doing activity within the base.
And if you already have crew at the base, when new crews arrive, the new crew would have less need of requirement to be immediately physical capable [being able to drive a car or similar type capability}.

Another factor is the GRC radiation received by crew in transit varies a lot depending on whether it's Solar Min or Max. So might use slower travel time when the GRC radiation is low and fastest when high.
And other factor has to do with Earth to Mars launch windows, being able to go fast to Mars, widens that window.

gbaikie said...

--A good world building sim would take thermal management into account as a barrier to population growth.--

Well, when considering our solar system could have a human population of trillions- I didn't think thermal management would be problem. But as general matter living in space environment does have this problem.

Many think the space environment is cold and it isn't- vacuum of space has no temperature.
If look at Earth, it doesn't have shortage in terms of cooling potential. The atmosphere perhaps, but Earth has cold ocean. That it has cold ocean, is why we in an Ice Age. But it's thought that Earth had a much warmer ocean in the past and Earth was not in an Ice Age.
It seems that the Earth is roughly a huge ball of molten rock, yet on it's thin skin, it has ocean which has average temperature of about 3.5 C, and would seem to me to indicate that our Earth has some clues of how one could keep things cool.
In simple terms, it seems if most of planet was not molten ball rock, one could imagine Earth as possibly having a colder ocean.

Now, it seems an important element which makes Earth ocean cold, is gravity. And do you need as much gravity as Earth has in order to have ocean as cold as it is?
Or you could replace the rock with water and you would have less gravity, does that make it less cold or warmer. So keep continents and islands by having them float on the ocean, so looks like Earth and has far less gravity.
One problem is that cold polar water falls, and it seems it would fall to center of the "Earth". So solve that problem you also ocean basins. And if you building ocean basins, what best basin which causes the ocean to be the coolest- or does it matter much?

But to make it all easier, even if this fake Earth was warmer, it seems you simply have it far enough from the sun, so that ocean was as cold or colder than average of 3.5 C.

So you have ways of using less water, but if had enough water, to cool like Earth does, it doesn't seem you could problem with thermal management.

Or just put 2 km deep ocean on Mars and add some atmosphere and Mars shouldn't have thermal management problem. And moons of Jupiter shouldn't have thermal management. Or they did, move them so the have less tidal heating with Jupiter.

It could be more difficult than this, but if one could figure out the exact reasons that Ocean is so cold, such lessons could be used for thermal management of spacefaring civilization.

gbaikie said...

Re: "It could be more difficult than this, but...."
I was thinking and main reason Ocean {or atmosphere} works well with waste heat- is they add surface area. Or reason waste heat a problem in space is because anything "adding surface" is "expensive".
Apply this idea, Venus is easy/cheap place to do "thermal management"- because it has thick atmosphere. If worried about planet heating up, Venus is best place.
And this is accordance with my idea that Venus is a good fortress. Or you hit Venus with 100 km diameter space rock, it's not much of problem. Whereas Earth would be incinerated- or it's an extinction event.
Now if you trying to cool the blazing hot air temperature of surface, that could be problem. But you live in the sky of Venus. And if living in sky of Venus the entire surface could be molten rock and it's not a particularly difficult problem for you. Or there will always be lots of colder sky to live in- in terms of 1 to 1/2 to atm of atmospheric pressure.
Mars is "thermal management" only in sense it's expensive- and atmosphere is too thin to use effectively- it's not much better than a vacuum. But ok, as every is not expensive.
If you are spacefaring civilization stuff is cheaper in space than on Earth- but even same price it's not much of problem.
You can't have human settlements on Mars if water is expensive- even if weren't talking thermal management- humans use a lot of water and make food, you need water.
So on Earth, the use of water is for thermal management, residential use, and largest use for growing food. But expensive water on Mars, dooms you even you just consider "residential use". Anyways, mars water at $1 per kg is still expensive, but it's cheap enough for Mars settlements and $10 per kg, seems quite iffy. But in terms thermal management, Mars water at $10 per kg, would make thermal management less of problem in context the high cost anything beyond Earth surface.
In terms of the Moon. Lunar water can be as high as $500 kg. If Moon can't have water as cheap as $500 per kg, I have said and will say, it's not viable destination. But at $500 per kg, the moon is not viable destination human settlements, though it's fine for lunar tourism. And great for lunar bases. The price of water is not issue in terms exploratory cost. I don't think NASA should waste tax dollars mining for anything on the Moon or Mars, rather NASA's job is to determine whether water could be available to be mined.
Lunar water mining will eventually lower price of lunar water and lunar electrical power, when there available at far lower price, then you could have settlements on the Moon.
But getting back to thermal management and assume Mars water is more expensive: $10 per kg or $10,000 per ton, or 1000 tons costs 10 million dollars. Thousands of tons water used to cool a nuclear reactor, is costing some small fraction of the cost of a nuclear reactor send to Mars. And cooling reactor without water, will cost more then money spend trying to do it without water. Plus you have warm water- the waste heat can be useful on this cold desert planet.
But of course $1 per kg {or less} makes it cheaper to generate electrical energy from nuclear reactor in addition to lower other cost of other aspects of living on Mars.
And Mars as civilization would need hundreds of billion tons of water PER year- but we can start with a few towns on Mars. And billion tons of available $1 per kg mars water, will be more than enough to start a town.

Loren Pechtel said...

@gbaikie A 100km rock is just as deadly on Venus as on Earth.

And even if water is $500kg it can still be used for thermal management, you just need to be careful to recover it all. Consider: I'm writing this on a computer with water cooling for the CPU. The whole water cooling unit came as a sealed assembly, one part fastens to the CPU like any heat sink but it has a power wire, one part goes in a fan hole, two hoses connect them. I'm not even sure the liquid inside is water. There are also heat-pipe based coolers, the coolant is continually boiled off by the CPU's heat. It just condenses back to liquid not far away.

gbaikie said...

"And even if water is $500kg it can still be used for thermal management, you just need to be careful to recover it all."

Getting electrical on the moon, is pretty easy in terms harvesting solar energy- though probably want to cool solar panels with water, as cooler panels are more efficient.
Mars even though it gets 60% less sunlight at it's distance compared to Earth distance, gets comparable amount of solar energy as compared the Earth surface.
Earth surface only gets solar power for about 25% of the day due mostly to Earth's thick atmosphere which dramatically reduces solar energy when the sun is 30 degree or lower above the horizon. With Mars with it's thin atmosphere, one get solar energy when sun rises above horizon in the morning until sunset {or average of 12 hours per day [50% of the day]}.
Mars also has somewhat similar advantages, as lunar polar region- or terrain feature can allow higher 50% per day. The lunar polar regions areas where you get 85% of the time with sunlight. I am sure what percentage is on Mars polar regions, but mean could site on Mars which give 55% to 60% sunlight per year. And in polar region summer longer daylight than night, in summer season on Mars one equal lunar 85% {year around] and winter season of course, you have far less. So do things which were energy intensive in the months of summer. And it's similar to polar lunar in in terms having grid which encircles the polar region. With Moon with such grid which provides solar power 100% of the time, you a few sites tens of km apart, and Mars it a lot more sites and spaced hundreds of km apart, could get some solar power, 100% of the time.
There Lunar polar region is far better than Mars- and Earth surface is solar simply can't serve as primary source energy for anything- it "needs magical batteries"} .
What is similar to lunar polar region is SPS [Space Power Satellite] in GEO- which are something like 95% of time, but unless using the energy at GEO, you have beam the power somewhere. So since lunar polar region doesn't need to beam power anywhere, it's better.

But it would hopeless to beam lunar power to Earth. Instead in future when lunar costs lower, significantly, you make SPS on the Moon, and put them in GEO, which then beams power to Earth {though by that time one also GEO SPS to provide power to uses in GEO- so factories in GEO, which can use the very cheap power, and then ship products to Earth surface {or elsewhere}.

But anyhow, one argue that nuclear energy on Mars is better than Mars solar. [Though one also argue that nuclear energy on the Moon might better or at least be competitive with lunar solar.] And Nuclear energy has a lot waste heat {and waste heat as hot water on Mars could be use for homes and/or Greenhouse heating]
One could grow food on the Moon, but Mars would export food. And one probably get to the point of getting cheaper Mars food on the Moon, then cost to grow food on the Moon.
US is a superpower because of it's farming, and Mars likewise will be a superpower, because of it's farming. And the Moon can build SPS for Earth and Mars.

gbaikie said...

Say you were living on the ocean on Earth, on a cheap platform that is stable in Cat 5 {or 6} hurricane. And you could safer than anywhere on Earth, and particularly safer than on beach in Cat 5 {or 6} hurricane. But significant threat anywhere on Earth is floods. And you don't have problems with floods in an Ocean. If you in deep water, tsunami aren't problem. Though certainly a problem anywhere near a beach. And earthquakes aren't a problem. One could have house fires, but not forest fires. Tornadoes in form of waterspout, might be problem. Wiki, Waterspout:
" While it is often weaker than most of its land counterparts, stronger versions spawned by mesocyclones do occur."
So, maybe. But, anyhow. One problem with living in Ocean is lack of electrical power. And if Earth had SPS, that could solve the lack available electricity.
Though another way to get electrical power would be have nuclear powerplants in the ocean.
And having nuclear powerplants also depend having safe location or a cheap platform that is stable in Cat 5 {or 6} hurricane and doesn't earthquakes, floods, etc is important.

Now a general problem with the ocean is corrosion due to saltwater. There serious problems saltwater corrosion even if near an ocean, as in on a beach within 100 meters of ocean. And this have be included in design aspect in order to have a cheap platform.
So, another thing, which isn't exactly a solution to saltwater corrosion, but it's related to it, is that you could have freshwater lake on the ocean. And fresh lake might better place for nuclear powerplant.
But people living in a ocean also need fresh water. So can have power and water.
You need waste disposal {garbage and sewer service}. Which reminds that the materials used for the cheap platform could be waste glass or even waste plastics. But if nothing else, it could be concrete. Or major way cheap platform could be cheap is how they are made, rather material used. But having make out living corral might sound neat- but how you do this cheap, is not clear to me- but it seems possible some way could developed so it's cheap if there is enough market demand for living in the ocean. But anyhow waste glass would work if using waste glass was comparable cost to using concrete- or that people would pay more for it to made from waste glass {or waste plastic}.
Next major thing would be transportation. Travelling by water is typically, slow.
But there quite few solutions to this- currently. But I am talking of future with either SPS or nuclear plants in the ocean. So time wise within two decades is unlikely.

Let's start with future where lunar water mining is occurring on the Moon- which might occur within 2 decades. And within two decades you could have sub-orbital travel which just isn't just going up to 100 km elevation for joyrides.
And you could rockets being typically launched from the Ocean.
Or it seems launching rockets from land areas, only makes sense, if government is "subsidizing" rocket launching areas. And launching rockets at rate of about 2 per month- and it appears, we are moving away from that. And sub-orbital from ocean for similar reasons makes more sense from ocean to ocean zones.
So a part of the transportation solution of living in ocean could be sub orbital travel.
But there other things also.

Loren Pechtel said...

@gbaikie You can avoid all hurricanes by staying close enough to the equator.

gbaikie said...

You could live at equator.

You want to launch rockets which going into orbit from the equator.
At equator you can launch directly into a zero inclination orbit which can't do from anywhere else on Earth. And zero inclination is where a lot satellites are in Geostationtary orbit.

If you launch a rocket at say at around 28 degree latitude {Kennedy Spaceport- KSC} your lowest launch inclination is 28.5 degrees. And what is done. is you do a GTO {Geostationary transfer orbit} and then change the inclination near apogee to the zero inclination and then circularize the orbit to be in GEO- and the change of inclination cost you significant amount of delta-v.
From Equator you don't pay this penalty of changing inclination.
And get max amount of spin from Earth which lowers the delta-v cost to get to orbit. Or if at equator and want to launch into to 28.5 inclination orbit, you can do it even slightly easier than compared from 28.5 latitude launch.
Or you can launch to any inclination at equator and requires the least amount delta-v. Unless, you want Retrograde orbit where earth's spin works against you.
Or wiki:
"Artificial satellites in low inclination orbits are rarely placed in retrograde orbit.This is partly due to the extra velocity (and propellant) required to launch into orbit against the direction of the Earth's rotation."
https://en.wikipedia.org/wiki/Artificial_satellites_in_retrograde_orbit
But if only slightly retrograde as wiki says, that a sun-synchronous orbit could be, it doesn't have much penalty {wherever you launch from}.

In terms living near launch site, you don't want live downrange- within hundreds of miles. And don't want live in landing zone of incoming spacecraft- within hundreds miles {sonic booms}.
And seems that on ocean you want the landing area which is down range from rocket launch site.
And if not downrange, 20 miles from launch site, would be ok.

We have heard the loud noise from Saturn V launch but it seems a Starship launch is going to be even louder. And in future, could have even bigger rockets than the 5000 ton Starship.
{But I think if launched from pipelauncher, the rocket could make less sound for those near the ground {or water}- which could be regarded as slight disadvantage to those who watch rocket launch launches.}

gbaikie said...

Does launching from the Moon {to say, Mars} make any sense?
{{throwing rocks or shotgun Java n-body sim}}
Obviously, it doesn't make any kind of sense if rocket fuel is not available on the lunar surface, so the assumption is that rocket fuel available on the Moon.
Assume LOX is $1000 per kg and Liquid Hydrogen is $8000 per kg.
7 kg of 6 parts LOX and 1 part LH2 is 6000 + 8000 = 14,000 equals $2000 per kg of rocket fuel.
So, you have to spend the extra delta-v to enter lunar orbit and land on lunar surface, but the rocket fuel used up can be replaced- at price of $2 million per ton.
You get less Oberth Effect if launch from Moon as compared to LEO.
But you don't need much delta-v to go to Mars- mostly, it's getting out of Low Earth orbit
From LEO takes 4.1 km/sec to get to Mars distance. Does it take less than 4.1 km/sec get from lunar surface to Mars?
If toss a rock from a Mars distance and hit to Moon wherever it's in it's orbit, it wouldn't have a large impact velocity hitting the Moon. Whereas throwing rock from Mars at something in LEO, it's always going impact at much larger velocity.
A few space rocks have minimal impact velocity in regards impacting the Moon.
The Moon and Earth have average impact velocity of about 20 km/sec, but least velocity impact with Moon is near Moon's escape velocity.
Such low velocity impactors would be rocks with orbits of a similar inclination of Earth orbit.

gbaikie said...

Just going over wish list, again:
--Wish Number 2: Tunneling on small bodies

For planets and large moons we are limited to exploiting only the thin outer shell of a body. Heat and pressure prohibit us from tunneling deeply.--

Roughly, it seems Earth is most limited in terms a thin outer shell. One could argue the Earth ocean provides a form of access to "Earth depths". And it's huge pressure or more of matter of human not wanting to live in high pressure environment. What is max pressure human live in:
"That maximum pressure people can withstand is surprisingly high. People have worked at pressures more than 70 times normal atmospheric pressure (which equals 70 times 14.7 pounds per square inch). It may be possible to go higher but high pressure gasses are narcotic or hallucinogenic so people exposed to them wouldn’t be able to get much useful done."
https://www.quora.com/What-is-the-maximum-atmospheric-pressure-a-human-can-survive

Humans not wanting to have hallucinogenic effects, how unusual! So about 1000 psi or pressure at 700 meter of water. So if lived at 700 meter under water, one vehicles which go deeper more easily {less structural strength of vehicle is needed}. If living at 700 meters, you have higher density of gases in your lungs or you could say one is effectively making the human lungs larger. Metaphorically, it's like growing wings. A problem is the water is very cold at 700 meters. And sunlight is rather dim down there. You could pipe in sunlight- but could warm water as warmed water rises. Hmm, but doesn't rise fast, could have domed city with sunlight piped in. But does tend to isolate you from rest of the world- it take weeks to safely come to the surface- a long journey. But if not so much at surface, it's less of problem.
Back to Earth and it comparatively thin outer rocky shell. Compare to Venus or Jupiter's highly hot and volcanic Io, Earth might be as thin skinned. Both Mercury and Mars should be quite thick. Both are assumed to be quite old. There is theory that Mercury's crust was "scraped off" from very large impactor body- or one might say Mercury was the smaller body which hit something as big or bigger. But I don't think either planet has as much in terms of radioactive heating as Earth has, and doesn't have tidally heating from our large Moon and doesn't have as much primordial heat remaining as the Earth does.

gbaikie said...

The other part I cut because was too long to fit:
Playground of crust depth should Europa and mention Ceres. Both could called frozen water worlds. I happen to think Mars could at somewhat close to a frozen water world, but perhaps closer could be frozen water which doesn't have a dry rock mantle:
"The mantle lies between Earth's dense, super-heated core and its thin outer layer, the crust. The mantle is about 2,900 kilometers (1,802 miles) thick, and makes up a whopping 84% of Earth's total volume" Two quotes to consider:
"Electrical conductivity data suggest the normal upper mantle is essentially dry and its water content is less than 100 ppm or ∼100 ppm" and
"The amount of water in the Earth's mantle equals that in all of the oceans, and some scientists have hypothesized that the water in the mantle is part of a "whole-Earth water cycle". The water in the mantle is dissolved in various minerals near the transition zone between Earth's upper and lower mantle."
Are both true. 100 ppm of water reminds of the dryness of the Moon. 100 ppm is not mineable lunar water. A 1000 pmm is .1%. .01% is pretty darn dry. But 84% of Earth which is quite dry is going to have a lot of water involved. It's thought plate tectonic "caused" it to be drier, so easy to assume Mars would be wetter. Or only real question is how much wetter.
And saying I think it possible to be a lot more wetter. And don't imagine oceans of Mars escaped into space, but the sunk into Mars. And such small amount surface water at the imagine or thought to be at the surface billions of years ago was small fraction of water that was in the crust- and Mars mantle.
Or turn off Earth's tectonic activity. And wait 1 billion years. What does Earth look like?

gbaikie said...

TRAPPIST-1 solar system wiki:
https://en.wikipedia.org/wiki/TRAPPIST-1#cite_ref-Delrez2018_8-0

Looks like to me, it could be alien made starport.
It's red dwarf sun with 7 planets which very close to the star.
Nearest planet something that looks like Venus with a lot water then Earth has has year of
36.261 hours and furthest planet has year of 450.43 hours.
I think all are habitable by humans, but of course I think Venus and Mercury are habitable by humans. All 7 planets are thought to tidally locked. {Better place to live, IMO if truly tidally locked- Mercury was not truly tidally locked rather than being a 3:2 spin–orbit resonance, it would be better]. But most of these 7 planets are roughly earth like in terms mass and thought to have atmosphere. Anyhow, in terms being starport the types of planets doesn't matter. What is significant is they all very close to the same inclination and largest difference is 89.56 degree inclination [nearest planet} and 89.89 degree inclination {the third plant from star}.
And our problem with Mercury is it's Orbit inclination (deg) 7.00 compared to Earth 0.0 inclination {it's 0.0 degree because the humans live on- and 7 planets inclination of about 89.56 inclination are because it's not where humans living. A 7 degree difference is huge difference particularly if planets are orbiting fast. And these 7 planets are orbiting pretty fasts. Mercury went closest to sun {fastest} is 58.98 km/sec.
The closest planet is going 81.149 km/sec, and second one out is going: 71.944 km/sec
and third one is: 59.8498.
Fourth one: "TRAPPIST-1e is the one with the greatest chance of being an Earth-like ocean planet and the one most worthy of further study with regard to habitability" - wiki
Orbital velocity: 52.23 km/sec
Fifth one:
"TRAPPIST-1f is an Earth-sized exoplanet, meaning it has a mass and radius close to that of Earth."
Orbital period 9.206690 days
orbital velocity: 43.4435 km/sec
Not done velocity of two other planets.

Why is it starport? They have small orbit, they going 10 to 9 km/sec faster, if leaving from the most inner planet, you going a lot launch windows to other planets.
Plus it seems they also will eventually all line in straight line. Which is not particularly useful, in comparison Sol doing this, it's fairly rare. But more important then a straight is having them in the right place at the same time, or having 3 or 4 of them being in right place at right time- so you leave and hit 3 or more for a gravity assist. But also applies when entering the system if arrive at proper location at proper time, you can gravity assist to slow down rather than speed up.
So, it makes a good starport. Now if want to use atmospheres to slow down, lots of them appear to large atmospheres, you also hit a series of planets atmospheres.
And also it seems use the star itself. It's a bit larger than our Jupiter but a lot massive, "about 84 times more massive." And temperature of "2,511 K (2,238 °C; 4,060 °F"

gbaikie said...

Star travel of 4+ lightyears is impractical. But for TRAPPIST-1 solar system, it seems star travel could be a lot easier.
TRAPPIST-1 has better gravity hole:
26,695‬ earth masses
At it's surface 76597 km radius
escape velocity: 527.081 km/sec
More distance:
26695‬ earth masses
100,000 km radius
escape velocity: 461.2995
Vs Sol:
333000 earth masses
Sun radius: 696340 km
escape velocity:617.418 km/sec
Used this calculator:
https://tinyurl.com/ya7r7c9o
Our Solar probe going to a very hot region 9.86 solar radii or 6.9 million km
Sun distance: 6,900,000 km
escape velocity: 196.1397 km/sec

I tried to use Sol from Jupiter and it seems the faster you approach the sun, the less time there is for Sun's gravity to add velocity. Or you fall from Jupiter distance, one get significant amount velocity added before getting to Mercury distance.
Red dwarf has same problem. But if coming into star system, such "loss" is a gain- if approach star fast, it adds less velocity, and on leg out, you brake. So approach star so don't exceed say, 460 km/sec.
Could reach outer planet [9.27 million km from star} going say 500 km/sec, and when pass inner planet distance {1.73 million km] be going less than 450 Km/sec
1.7 million divided by 450 is 3777.7 Second or about hour from sun, and as guess fairly easy to keep below 450 Km/sec and brake after hitting the sun distance brake by 30 km/sec and end up at planet distance [9.27 million km from star}.
Could be entering system at +1000 Km/sec at 1000 AU distance, but as get closer to outer planet distance, you will have slowed down to 500 km/sec. And then in about 1 day time period before at docked at 9.27 million km from star. Or having these planets and Sun, could save more than 300 km/sec of delta-v. If doing something similar with Sol system, the quickest you dock in system might about 1 month and would not save as much as 300 km/sec. Though if didn't want save delta-v, you could brake to whatever distance and not waste any time before docking.
And leaving TRAPPIST-1 system, you can save another +300 km/sec and not require a lot time to do it.
Could have situation of space aliens leaving from Sol like sun, and go less than 1 light speed distant a red Dwarf system, refuel. And leave the Red dwarf system faster than the same starship left the Sol type system.

Earth had a red dwarf star get quite close to Sol:
Scholz's star, 78,500 years ago was 0.82 lightyears from Sol.
Gliese 710, in 1.28 million years will be 0.178 lightyears from Earth
https://en.wikipedia.org/wiki/List_of_nearest_stars_and_brown_dwarfs
And space aliens might have better timing than we have.

gbaikie said...

I have been thinking more lately about ocean settlements and I seemed to stumbled across idea
of how to do it, which seems different than I have seen. And my idea [or trick] is to focus
on stopping ocean waves. This was related the idea making a freshwater lake in the ocean and making ocean homes which hurricane proof.
And roughly it would use buoy spars {which kind of similar pipelauncher} to create perimeter
that acts like floating breakwater. So idea is improve the surface ocean environment by stopping ocean waves and creating having freshwater lake within enclosure {again, roughly using a bunch of anchored buoy spars]. Also got provide electrical power, water, sewage treatment, and having transportation system to the mainland- and want make settlement fairly close to mainland, such 10 to 20 km away. So transportation to nearby towns {or hospitals} is fairly quick.

C Oda said...

The graphics and paper referenced here: https://physics.stackexchange.com/questions/571480/properties-of-orbit-type-diagrams might be of interest to you!