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.






12 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.