July 7, 2015

Kerbal Space Program

 Kerbal Space Program moved into full release early this year.  Although the makers, Squad, will continue with patching and minor improvements, they say the game includes all the features they hoped to include.  Which I think makes this a good time to finally give my opinion on the game.  If you haven't heard of it, Kerbal Space Program is an excellent game available at a quite reasonable price for download on their site or on Steam.  Some friends of mine downloaded the game a while back for free, I was busy at the time and didn't get it.  I feel very foolish for that now, and gladly spent the $20 to download it last year.
 The game is available for Windows, Linux, and Mac, which I am grateful for since it means I don't have to reboot into Windows and can just use my regular Linux partition to play the game when I have time, something in depressingly short supply.  However, the other week I had my wisdom teeth removed, which meant a few days with nothing to do but launch little green men into space.
 Of course I'm not a game reviewer, I'm a starship engineer.  And that's how I want to look at this game.  So first let's go over the basics of the game.  In Kerbal Space Program, or KSP for short, you take control of  the space program for a group of people called Kerbals.  Hence the title.   Kerbals are small green creatures with large heads, tremendous enthusiasm, and no sense of self-preservation.  They will happily fly whatever insane creations you design in your efforts to explore the solar system.

 Your job in KSP is to design, build, and fly the vehicles that the little green men use to explore their solar system.  To accomplish this you put together a vehicle from stock components available in a generally easy to use Vehicle Assembly Building.  Individual components fit together a bit like LEGO pieces, each one performing some important function for your spacecraft.  Fuel tanks, engines, crew capsules, science experiments, antennae, parachutes, decouplers, a huge collection of parts is available for designing spacecraft both practical and ludicrous.

A simple rocket in the Vehicle Assembly Building
  Building a spacecraft is a complex balancing act of  competing requirements.  More fuel will get you further, but at the expense of more weight and greater cost.  Powerful engines can lift you higher and faster, but consume fuel faster.  More scientific packages mean greater payout and more research development, but also add weight to the vehicle.  Each part serves a specific purpose, and is fitted to the vehicle in a very simple and easy to use manner.  There are some oddities in how the VAB chooses to position parts in some cases that leads to frustration, but usually things run fairly smoothly.

  The game now has three modes: career, science, and sandbox.  In sandbox mode all of the flight components are available from the outset.  In science mode you have to earn additional components.  By building vehicles and completing missions you gain Science, you then spend Science to unlock new branches in the tech tree.  Unlocking a new technology grants you new parts you can use to build bigger, better ships and accomplish new missions and get more science.  So, though your first vessel might just be a crew module, solid rocket engine, and a parachute; eventually you are able to design massive inerplanetary vessels to carry large numbers of Kerbals to establish extraplanetary outposts.  Along the way you will learn more about how to control and design your spacecraft.
  Science unlocks technologies in the tech tree and is gained by sending Kerbals and experiments to new locations and retrieving data from those missions.  You can transmit the data back, but lose a sizeable amount of its value over physically retrieving specimens.  Kerbals record their thoughts on each location, both from the safety of the crew capsule and from performing Extra Vehicular Activities.  On the surface of other bodies Kerbals can also collect surface samples to be analyzed back at the space center.
The Tech Tree
 In career mode not only do you gain Science, you must also balance Funds and Reputation.  These are gained by accomplishing Missions, which are made available from various sources.  In this mode all rocket components have an associated cost, you spend your gained funds when you launch each vehicle.  Now your objective isn't just to build a vehicle capable of accomplishing your mission, but also to do so under budget.  You get a small advance from each contract, but must pay a penalty if you aren't able to accomplish the mission within a given time.
Kerbal Space Center it its early days
 Reputation in career mode is also gained by accomplishing your assigned Missions.  A higher reputation allows you to take on more difficult, higher reward, missions.  Failing to accomplish your mission in a reasonable time frame costs you reputation.
  The game also allows you to manage aspects of how your program is run.  From the administration building you're able to set policies that impact how you gain rewards.  Here you can choose to trade some percentage of your incoming Funds, Reputation, or Science for a smaller amount of one of the others.  For example, Unpaid Interns increase the science you gain, but at the cost of reducing your reputation gains.
  As time goes by you can upgrade buildings at the space center to improve their abilities.  Better launch pads can accommodate larger spacecraft.  An upgraded tracking center can track more vehicles and detect new objects in space.  Advancing your research center gets you access to more advanced branches of the tech tree.  Every building can be upgraded, and every building can be damaged by careless flight.
Simple spacecraft on the launch pad
  Once you've built your ship you have to fly it.  Here the game really shines, with fairly accurate orbital mechanics to describe your vehicles' movement.  Strictly speaking the game uses a patched conic and sphere of influence approximation, rather than multi-body physics, to speed computation time.  It's a simplification, true, but it hardly detracts from the game as this approximation is valid during most regimes of real flight.
Another simple spacecraft in suborbital flight
 The game has an orbit screen that shows what body you are in orbit about, your altitude above it, your periapsis and apiapsis, and will show your projected course if you are on an escape trajectory.  You can plan maneuvers in advance, orient your spacecraft, and fire to get the delta-v you need to change your orbit.
The same spacecraft's trajectory
  You fly to collect science and complete missions.  Missions are found back at your space center and have very specific requirements.  Usually they're things like collect data at this location or use a particular part at a specific altitude.  Some can be more involved, like rescue an astronaut stranded in orbit.
  To collect science you carry Kerbals and experiment packages to unfamiliar locations.  There are dozens of possible biomes, vague areas and altitudes, where you can perform multiple experiments.  Trained astronauts will collect crew reports, EVA reports, and surface samples.   Spacecraft can be equipped with a variety of scientific experiments, each of which produces new and interesting data in each new environment it is used in.
Kerbal collecting useful EVA data in Kerbin's deserts

  The other week I had the lovely experience of getting my wisdom teeth removed, which left me a few days with nothing but painkillers and Kerbals to pass the time.  It gave me the opportunity to finally start a new game and really enjoy KSP since it hit full release.  I've known this game was amazing since alpha, and it's even more incredible now.

Remember kids: This is your rocket on drugs
  If I was still teaching spacecraft systems I would seriously consider KSP as a teaching tool.  The game breaks down all the crucial factors of spacecraft performance, in a colorful and fun way.  Every vehicle has to balance competing demands for thrust, fuel efficiency, power production, power consumption, capability, and weight.  Once launched designers must consider aerodynamic effects, orbital mechanics, landing locations, and reentry.   Designers can build standard vehicles to complete a variety of tasks, tackle multiple missions at once, or try to build dedicated vehicles for each mission.
 Kerbal players will come away from the game with an intuitive understanding of spacecraft design concerns and orbital mechanics.  You learn through the game, without ever realizing it, the meaning and importance of thrust-to-weight ratios, specific impulse, electrical power systems, ascending and descending nodes, patched conics, eclipse time... the list goes on and on.  It's almost impossible to play the game and not learn something new about spacecraft.

 The tradeoffs that Kerbal designers must take into account are greatly simplified, as are the physics and environments they must deal with, but they really do cover the concerns of real spaceflight.  The game manages to perfectly balance accuracy, silliness, and fun gameplay.  If you like video games or spacecraft at all Kerbal Space Program is definitely worth giving a try.

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