One of my "interior fuel column" designs

One of my “interior fuel column” designs

Imagine a game that has no guns, no victory conditions, no boss battle, no cut scenes, no blood, no frenetic music, cars, babes, monsters or gold and instead encourages you to learn about things like apogees, perigees and ascension nodes? Renew your hope in the future of humanity because such a game exists, is popular, educational and fun.

Years ago I reviewed computer games for a national newspaper. It was in the far distant past dominated by titles like Lemmings, Jet Fighter II, Ultima VII. It takes something very special to get me interested in these dull days of endless first-person shooters, and that is the intriguing Kerbal Space Program (KSP).

It isn’t a new game, the first release was in 2011, which means it’s mostly bug-free, has a active community of players, and has plenty of creative mods to install. Despite being two years old the developers say the game is still in its alpha stage and plan many enhancements.

The gist of the game is simple: You’re in charge of the Kerbal Space Program, which is basically current-day chemical rocket technology. KSP has a fictitious solar system but you can consider Earth to be Kerban, the Moon is the Mun, Mars is Duna, Eve is Venus, etc etc. Names aside, what you’re really running here is an early 21st-century space program with the wondrous difference that money is irrelevant.

That just leaves realistically modelled physics as your enemy.

Your first step is to simply get a rocket into orbit. When you’re starting out that’s pretty hard in itself. KSP doesn’t easily give up its secrets. How many stages do you need; what amount of fuel per stage; should you include some strap-on solid boosters; where should the stabilizers go; should you build a single-person capsule, or plan ahead and start with the larger three-person capsule?

Then there’s the dynamics of the flight: Should you throttle up all the way, or restrict the power and go for a slow turn to orbit? What’s the best height to turn? What’s a good altitude for a stable orbit? Those questions will keep you occupied for some long time. Along the way you’ll also learn to appreciate apogees, perigees, the periapsis and apoapsis of an orbit, your craft’s Delta-V and ascension nodes.

YouTube is full of Kerbal videos, I found this one to be pretty typical of how you can expect your early experiments to go:

Once you’ve made orbit – and can repeat the feat at will – you ponder the next step. A flight to the Mun (Moon), or perhaps a space station in Kerban orbit? A crewed Mun flight is appealing, yet fraught with difficulties. If you’ve only just conquered orbital missions then chances are your booster technology hasn’t got a lot of slack in it to increase the payload for a Mun lander. In that case perhaps you should pause the exploratory urge and build a better heavy booster?

I got stuck on heavy boosters for a long time. How innovative can you make your design to get that little extra into orbit?

For Kerban zealots the so-called “asparagus staging” method is the mark of an experienced player. Instead of a basic Saturn-V-style multi-stage booster you use a cluster of boosters – ideally six or eight – which are sequentially dumped in pairs. Fuel from the first pair is used to power all the engines on the rocket, which means the fuel is used extremely fast. Those two boosters are then jettisoned, and all the engines then draw their fuel from the next two boosters, and so on. The idea is that you don’t lift multiple half-empty fuel tanks.

Is it a hack? Maybe, although in reality in does make sense, and the amount of work involved to set up “asparagus staging” in the game certainly doesn’t make it feel like a cheat – you work for the result.

In my case I tried to take it a step further. Instead of sequentially dumping entire booster pairs with their engines, why not just sequentially dump fuel tanks and keep all the engines running?

Now you have an engineering and design problem: How do you design a rocket to keep all its engines but dump most of its fuel tanks? Eventually I got on the idea of an outside ring of engines set around a totem-like tower of fuel tanks. Every engine feeds off the bottom-most tank, which is then dropped in sequence through the core of the rocket.

Sounds good, but that leads to issues bracing the structure since the power is concentrated on the outside ring and the mass in the central core. Then there’s the distressing tendency of many non-standard rocket designs to spin….

And all this before I’ve even got to the Mun.

Which is part of the appeal of KSP: you can concentrate on whatever part of the space program you like. It may be booster design, space stations, long-range probes, crewed lander missions to the outer planets, rovers, complex docking missions, spaceplanes and reusable shuttles, or plotting fuel-efficient gravity slingshot missions. There’s no victory conditions in KSP, you just explore space to the best of your technical abilities.

After I got over my initial booster-fixation I did land a modest mission on the Mun, plant the Kerban flag and suitably inspirational plaque, then head home again (for a hard landing at 6 metres/sec – I should have fitted more chutes).

Just like Apollo, the appeal faded after a few repeat missions and I contemplated the next phase. A Mun base perhaps? Technically challenging but not all that useful in terms of exploring the solar system. A direct flight to Duna (read: Mars)? More appealing and also far more challenging in terms of fuel and orbital mechanics. I thought the solution to that might be to first set up a space station and position a generous fuel supply in orbit so I had plenty for the Duna mission. Yes, although that now meant I had to practice docking manoeuvres and redesign my basic Mun lander to take a docked and fuelled sister-ship.

Maybe I should just work on that super-heavy booster again and bypass all the messy space-station docking?

These decisions are tough enough in a game where money is no object, and it’s given me more sympathy for NASA dealing with the added headaches of changing administrations, tight budgets, internal frictions, shifting goals, public opinion and critical technical paths.

Back on Kerban I’m designing boosters again, trying to slip into that sweet spot of maximum payload to orbit. Note that merely strapping on more and more solid boosters is not a solution.

The worst part of this game is that it gives you a running total of time spent playing. I try not to look at that, after all my next heavy booster with its cunning bottom-to-top fuel-routing may just be the one to get me to Duna.

Official site:
There’s a free demo version with just enough features to get you hooked…

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