Orion nuclear pulse mod Orion nuclear pulse mod for Kerbal Space program, alpha version 0.18. Download here. Instructions are in the readme file.

Late breaking news: Dogmatic Pyrrhonist made an improved version of my mod, use that instead:

After playing with Kerbal Space Program for a while, and having more fun than a human being should be allowed to have, I noticed a lack. In the game, you construct your rocket out of components. There was a nice selection of solid fuel rockets, liquid fuel rockets, an ion drive, and even a NERVA like solid core nuclear thermal rocket.

But the Orion nuclear pulse rocket was conspicuous by its absence.

I searched the mods made by other players, but there was no Orion. That was odd, there were mods for almost everything else. I searched the forums. There I found that there had been quite a few attempts, but none of them made it to a workable form. Which showed that players wanted one, but it was too difficult to make. Orion propulsion does not operate like other rockets, the Kerbal engine is not set up to handle it. One would have to write from scratch an Orion engine handler.

In the same spirit that led me to create this Atomic Rocket website, I got that stubborn "well FINE!" look in my eye, and decided to write my own. Once again there was something I really wanted, the experts on the topic were not interested in creating it, so I was forced to do it myself.

It did not matter that I barely knew how to play the game, and knew nothing about making mods or programming in the C# language. I knew enough of the game, was already skilled at making mesh models with Blender 3D, and C# had a similar syntax to C++ and other languages I did know. What I didn't know how to do I would simply just have to learn.

But the point was that the author of the Atomic Rockets website was going to have his Atomic Rocket mod, come hell or high water.

It has taken me about a month, but the mod is close to being finished. So, there.

Video of the legendary Scott Manley giving his review of the Orion mod. See his other Kerbal videos here.

USAF 10 meter Orion

by Anglave



You can follow some of my trials and tribulations in this forum thread.

The big break-through came from a gentleman who goes by the handle NovaSilisko. He was such a good mod-maker that the Kerbal team hired him. He had been working on his own Orion plug-in before he was hired, and he gifted me with the source code. It still sits at the core of my plug-in, though heavily modified and with other functionality added.

As a baseline, I modeled my engine after the 1960 USAF study for an Orion with a 10 meter pusher plate. My primary source of data was Aviation Project Review vol 1 no. 3 by Scott Lowther.

Programming the plug in was a matter of trial and error. Mostly error.

One of the trials resulted in a most amusing error. The idea was that one of the ways the Orion is different from a conventional rocket is how it shocks the entire spacecraft, instead of giving a steady pressure. So I programmed the plug-in to instantaneously transmit the shock of each nuclear explosive to all the other parts of the spacecraft. Therefore a spacecraft with inadequate bracing would get shaken to pieces.

This worked well enough with the 1 kiloton bombs, but was giving some problem with the 5 and 15 kiloton. On the launch pad I tried a 15 kt bomb, the jolt made the control cabin shoot off the engine like an atomic powered champagne cork. It made an altitude of about five thousand meters before plummeting to its doom. Meanwhile the engine, bereft of a cockpit, made an altitude of about two meters before it crashed. I tried again after tying down the control cabin with numerous struts to no avail. Well, that was not acceptable.

In an attempt to fix this, I changed the programming from ForceMode.Force to Forcemode.Impulse. That was the trial, boy was it an error.

On the launch pad I tried a 15 kiloton bomb. The jolt kicked the rear of the cockpit.

The cockpit detached and made the jump to lightspeed! Blasted thing was moving so howling fast it developed a plasma sheath. It was burning up in atmospheric reentry in reverse. The apogee was 92,000 freaking meters!

So I went back to the drawing board and found another way to fix the problem. Of course I fully expect some other evil KSP modder to take this phenomenon and weaponize it.

I threw in some fun effects as well. There are several types of bomb so one can customize the load-out to fit the delta-V requirements of a given mission. Each bomb burst illuminates the surroundings like a camera strobe. Other ships that are close to the blast are given a savage shove (an aircraft parked within 300 meters of the launch pad was blown clear over the horizon). Other ships that are too close are merely destroyed. This can come in handy when clearing orbital debris (I had to tone it down when a tester inadvertently blew up an asteroid). But you had better equip your Orion spacecraft with an auxiliary propulsion system if you want to dock to another spacecraft or space station. You do NOT want to dock to a station using a propulsion system that utilizes nuclear explosives. Not if you care about the station.

Most importantly, I made the plug-in "data-driven". This means that users can make their own Orion parts without having to do any computer programming. Non-programmers can customize their new ship parts by simply editing the text configuration file, instead of having to actually reprogram my plug-in. All the important customizable bits are controlled by the data in the text file, not hard-coded in the software. However as per the Kerbal rules, the source code of my plug-in is supplied with the mod, for security purposes. So any programmer who does wants to play with the code can do so.

I did find some valuable insights into Orion spacecraft by actually playing with the mod in the game. The bomb magazines are exceedingly dense, you need lots of attitude control jets in order to turn this monster. And even then it maneuvers like a pregnant hippo. But when you use the engine, it has shocking amounts of thrust and delta-V. Extended space missions that strain the limits of chemical rockets are trivially easy with the Orion. This is true in the real world as well, it is just that in the game the Kerbals did not sign a nuclear test ban treaty in 1963. The Kerbals are also immune to the dire effects of radiation as well. Immune to g forces as well, it is disturbing to see the g meter jolt from zero to 20g and back every second.

It is nice to get recognition. Somebody noticed my thread about the mod on Reddit here and here. The famous Bad Astronomy guy had this to say.

The response I've gotten to the creation of my mod is generally along the lines of "OMG! I'VE WANTED AN ORION MOD EVER SINCE I GOT THE GAME!" Although there are a smattering of players who complain that the texturing I've applied to the Orion does not match the other stock parts. For them, I've supplied information with the mod to allow them to alter the texture to their heart's content.

Warning: computer programming geek speak to follow. if you are not interested in the details, skip to the pictures below.

Modeling the engine in Blender was relatively easy. Doing the pusher-plate animation was not too hard. Learning to program in C# was not a challenge. Writing the plug-in was a nightmare because the programmers of Kerbal have not gotten around to writing full documentation for the Kerbal API (they are concentrating their efforts on finishing programming the game, as is right and proper). The only way to figure out how to do anything is by sifting through the on line forums, examining other mod's code, and asking lots of questions. And by doing lots of trial and error.

To keep my sanity, I had to set up a SVN source control system, a Bugzilla bug tracker, and a crude homebrew build manager made of Python scripts. This let me revert to prior working versions when the latest trial resulted in error, keep track of testers bug reports, and automate the complicated process of assembling all the little pieces into a working mod. But I was going to have my Orion. Blast it.

I rent my SVN and Bugzilla space from SVN Repository dot com.

I would like to thank those people who gave me help in creating this mod, including but not limited to NovaSilisko, Cerverus, boosterspice, Hremsfeld, redteddy23, Anglave, TheCardinal, and Scoundrel.

And thanks to the many playtesters, including but not limited to Canopus (first test pilot for Project Orion), SufficientAnonymity, Markarian421, s20dan, Vaccer, Mecha Pants, Rune, lyndonguitar, zirgon, mushroomman, khyron42, Fyrem, czokletmuss, Leonov, and hoojiwana.



by lyndonguitar





















Jebidiah's wildest dream come true

Like I said: there are a couple of odd bugs, but the bottom line is that I have my Orion mod.