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.


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.

Saturday, April 6, 2019

Bridenstine's Why The Moon Matters

Back in December 29, 2016 Bridenstine made a blog post "Why The Moon Matters". Bridenstine was representative of Oklahoma at the time.

Sadly the post was taken down when Bridenstine left his post as representative and became NASA administrator. But I recently found the post using the Wayback Machine.

Bridenstine's reasons were pretty the same arguments made by lunar scientist Paul Spudis (RIP).

I post it here for historical reference. Copying and pasting:

Jim's Blog

Why the Moon Matters

by Rep. Jim Bridenstine

f t # e
Washington, December 29, 2016 0 comments
On July 20, 1969, the free world won the space race when an American flag was planted on the Moon. Twelve Americans walked on the Moon during the Apollo program, resulting in a treasure trove of knowledge not only about the Moon, but about the universe.  Even better, by demonstrating the United States’ political, economic, and technological prowess, it played a part winning the Cold War. In 1983, Ronald Reagan introduced the Strategic Defense Initiative to defend the free world from nuclear ballistic missiles. While many called it destabilizing, and even suggested it was impossible to achieve, the Soviet Union took it very seriously, made every effort to eliminate it, and spent whatever it took to compete. They eventually went bankrupt.  SDI, while not fully implemented, was a geopolitical success built on the technical credibility provided by Apollo. As Ronald Reagan predicted, “We win. They lose.”

Through SDI, the Brilliant Pebbles program was born as a space based system to track and destroy ICBMs. Years later, in 1994, a Brilliant Pebbles satellite was repurposed to orbit and map the Moon. That mission, called Clementine, tested military sensors and made history when it provided evidence of lunar water ice. Later experiments by NASA and other space agencies indicated billions of tons of water ice at each lunar pole.

This single discovery should have immediately transformed America’s space program. Water ice not only represents a critical in situ resource for life support, but it can be cracked into its components, hydrogen and oxygen, to create the same chemical propellant that powers rockets.

All of this is available on a world that has no atmosphere and a gravity well that is 1/6th that of Earth. In other words, standard aerodynamic limitations do not apply, permitting the placement of the propellant into orbit either around the Moon or around the Earth.

From the discovery of water ice on the Moon until this day, the American objective should have been a permanent outpost of rovers and machines, with occasional manned missions for science and maintenance, in order to utilize the materials and energy of the Moon to drive down the costs and increase the capabilities of American operations in cis-lunar and interplanetary space.

Water ice on the Moon could be used to refuel satellites in orbit or perform on-orbit maintenance. Government and commercial satellite operators could save hundreds of millions of dollars by servicing their satellites with resources from the Moon rather than disposing of, and replacing, their expensive investments. Eventually, the customers of Direct TV, Dish Network, internet broadband from space, satellite radio, weather data, and others could see their bills reduced and their service capacities greatly increased.

While most satellites are not currently powered by liquid oxygen and liquid hydrogen, next generation satellite architectures could utilize lunar propellant if low-cost in-orbit servicing were available. Commercial operators will follow if the United States leads with its own constellations.  Such leadership would require a whole-of-government approach with the interagency support of the newly reconstituted National Space Council. The objective is a self-sustaining, cis-lunar economy, whereby government and commercial operators save money and maximize the utilization of space through the use of lunar resources.

This is also the first step for manned missions deeper into our solar system. A permanent human presence on other celestial bodies requires in situ resource utilization. The Moon, with its three-day emergency journey back to Earth, represents the best place to learn, train, and develop the necessary technologies and techniques for in situ resource utilization and an eventual long term human presence on Mars. Fortunately, the Space Launch System and Orion will start testing in 2018. This system, with a commercial lander, could quickly place machines and robots on the Moon to begin the cis-lunar economy. With the right presidential guidance, humans could return in short order as well; this time, to stay.

There are other economic benefits to a permanent presence on the Moon. Utilization of lunar oxides for in situ additive manufacturing (3-D printing) could sustain and develop lunar operations. If economical, we should pioneer the extraction of highly valuable platinum group metals and the ability to transport them back to Earth. The development of practical solar power satellites that beam energy directly to all areas of the Earth is made possible through the use of the resources of the Moon. Research on this concept is already being done in Japan, as well as at the Naval Research Lab here in the United States. The United States government should lead the way in retiring risk for these endeavors with the intent to empower commercial companies to sustain the cis-lunar economy. This could fundamentally alter the economic balance of power on Earth.

As the cis-lunar economy develops, competition for locations and resources on the Moon is inevitable. The Chinese currently have landers and rovers on the Moon. The United States does not. Very soon, the Chinese will be the first of humanity to explore the far side of the Moon and place robots at the poles. As my friend Congressman Bill Posey says, “They are not going there to collect rocks.” China has its own manned space station. The United States’ commitment to the International Space Station ends in 2024. China has a domestic capability to launch its Taikonauts into orbit. The United States relies on Russia. American adversaries are testing antisatellite weapons and proliferating satellite jamming, spoofing, and dazzling technologies. It is time for the United States to re-posture and assert true space leadership.

It must be stated that constitutionally, the U.S. government is required to provide for the common defense. This includes defending American military AND commercial assets in orbit, many of which have the dual role of providing commercial and military capabilities. The same applies for assets on and around the Moon. The U.S. government must establish a legal framework and be prepared to defend private and corporate rights and obligations, all keeping within the 1967 Outer Space Treaty. The United States must have cis-lunar situational awareness, a cis-lunar presence, and eventually must be able to defend freedom of action in space. Cis-lunar development will proceed with American values and the rule of law if the United States leads.

Space utilization has transformed the human condition, including how we communicate, navigate, produce food and energy, conduct banking, predict weather and perform disaster relief. While many of these gains are a result of private investment and commercial markets, they are only possible because the United States government took the lead and retired risk for these capabilities. Today, we are experiencing a space renaissance. The first launch of the Space Launch System is less than two years away. In 2021, we will use the Orion capsule to send astronauts beyond low Earth orbit for the first time since the 1970s. Commercial launch vehicles are maturing and commercial deep space habitats are currently in development. A renewed focus on utilizing the Moon can help further these advances and achievements. The choices we make now can forever make America the preeminent spacefaring nation.

Wednesday, March 13, 2019

Orbital Mechanics Coloring Book 2nd edition

Now Available at our online store

Hopefully it will soon be available on Amazon as a Kindle book.

I am not happy with this coloring book. Pages should be opaque enough that images on the other side don't show through. I had failed to specify heavier weight paper when printing this book.

So I am cutting the price of this book from $5.00 to $2.00. I will print a version with better quality paper when I can afford to.

New in the second edition

Given 24 more pages I can add a lot of extra stuff. I've kept most of the original 40 pages and added:

Page 18

In the section on Kepler's 2nd Law I've added a visualization that helps show r X v is twice the area swept out over a given time period. That specific angular momentum is twice the area of the ellipse per orbital period.

Page 22

Page 22 attempts to portray my visualization that helps me remember centrifugal acceleration is ω2r.

Pages 28 and 29

Attempts to explain radians and to show circular motion is ωr where ω is angular velocity in radians.

Pages 30 to 35

Are devoted to orbital vertical tethers. I am going to try to start calling these Sarmount tethers as I have recently learned Eagle Sarmount proposed these in the 1990s.

Perhaps science fiction device but I like them any way. The geometry and math associated with these is pleasing, in my opinion. Here are two pages from this section:

Pages 49 - 51

Are about the Oberth Benefit and EML2

Pages 51 - 52

Are about the rocket equation and mass fractions.

Pages 53 to 63

Looks at thrust vs exhaust velocity, dynamic pressure and the need to make a rapid ascent from a planetary surface to avoid gravity loss.

Page 64

Resources that have helped me. Books, websites, forums. Atomic Rockets, NasaSpaceflightForums, Space Stack Exchange, Tough SF and others. I am adding to this list as more occur to me.

Inside back cover

My favorite equations. The Vis Viva Equation will be at the top. I've been thinking of making a reference sheet to pin to the wall next to my computer. This would serve.

Here is the coloring book as of  March 2020 (6.4 MB pdf, not too big). Reviews would be appreciated. Steven Pietroban invested a fair amount of time looking over the first edition and found many small errors and a few substantial errors. Given my tendency to make misteaks, I'm sure there are errors hiding in my more recent effort. A heads up would be much appreciated if you see something wrong.

My email is hopd at cunews dot info.