Kerbal Space Program and the F1 Engine

[smartcooky]

First question: Anyone here have KSP? If so, can you tell me how much freedom you have to build your own rocket? Are you stuck with the game's available modules and engines or can you build using your own designs or other real world prebuilt components such as F1 or J2 engines or an STS SRB or a S1-C  booster stage?

Second Question: More about F1 engines really, Can an F1 in the form it was used in the Apollo Program, be relit after it has been shut down?

[Zakalwe]

Second Question: More about F1 engines really, Can an F1 in the form it was used in the Apollo Program, be relit after it has been shut down?

IIRC it used hypergolics* in a burst cartridge to start the ignition. The cartridges were ruptured by a feed off the high pressure fuel line? Once expended there'd be no way to start a second ignition.


*triethylboron with triethylaluminium

[Zakalwe]

Just found this:
"At T minus 8.9 seconds, a signal from the automatic sequencer fires four pyrotechnic devices. Two of them cause the fuel-rich turbine exhaust gas to ignite when it enters the engine bell. Another begins combustion within the gas generator while the fourth ignites the exhaust from the turbine.

Links are burned away by these igniters to generate an electrical signal to move the start solenoid. The start solenoid directs hydraulic pressure from the ground supply to open the main LOX valves. "

(Source: https://www.awesomestories.com/asset/view/F-1-Engine-Propulsion-of-the-Saturn-V-Moon-Rocket)

So, the pyro igniters would be consumed, as well as the electrical links that signal the valves to start the flow of LOX.

[QuietElite]

I have KSP.

You have many different fuel tank and engines part. You can tweak the position of your parts and can also clip them into each other so that you can recreate with some creativity the look of real world rockets or to build your own unique rocket. However there are limitations because the parts themself cant be really tweaked except things like the fuel amount in a fuel tank,etc. Recreating a N-1 rocket for example is basically impossible with stock parts since you cant really build these spherical fuel tanks of it.

The good thing is that there are plenty of mods which some of them are crucial even for players that dont like modding.

I recommend to use Realism Overhaul which is a whole collection of mods to make the game more realistic (it is in the real solar system and not the KSP solar system, you have to deal with real chemical fuels and their (dis)advantages, ullage concerns when starting a rocket engine, random engine failures, boil-off of cryogenic fuels,etc.).

Realism Overhaul also has a mod called procedural parts where you can really change the fuel tanks in their size, shape and texture to build your rocket as you like.

The FASA mod is also important if you want realistic rockets since it contains many parts from Mercury to Apollo and other stuff from this era. It has parts like the F-1 engine and stages of the Saturn rockets as example.

I only play the Realism Overhaul version of the game since some time and really like it. You could also use just some of these mods on their own but I really recommend the whole thing if you like realism and better options for tweaking parts.

[Allan F]

And if you download the game through Steam, you can keep different versions and different set of mods in separate directories. And keep them totally separated.

I've spent a few thousand hours in the game. Remember to use the 64-bit version, which you have to select either by starting the game through steam or by starting the game directly from the directory in which you keep it.

[smartcooky]

Thanks for the replies about KSP everyone, and thanks Zakalawe for your answer about F1. It rather pole-axes the idea I had.

A couple weeks ago I happened across an article about the early days of the Space Shuttle design, and it mentioned something called "Saturn-Shuttle", in which a modified S1-C booster would be used to launch the shuttle orbiter.. The configuration was booster + the orbiter's fuel tank on top with the Orbiter itself on the side.

With all these successful landings of Stage 1 boosters and talk of Big F.... Rockets from SpaceX, it got me to thinking how feasible it would be to launch the Shuttle Orbiter on top of a hugely modified S1-C stage. The stack would be as follows.

1. The modified version of the S1-C (call it S9-A) would be much wider and taller, with nine F1 engines (eight in an octaweb configuration and one in the centre a la Falcon  9)

2. The Shuttle Orbiter would be parked on top of the S9-A, with an interstage faring.

3. The Orbiter would be modified with a shorter payload bay, the saved space becoming additional fuel tanks for the final kick into orbit.

The plan would be two-stage to orbit, with the S9-A Stage 1 recovered back to the Cape using the single centre F1 engine for boostback, reentry and landing burns, and Stage 2 being the Orbiter itself. My plan is rather foiled by the fact that an F1 engine cannot be relit so a different centre engine would have to be used (F1B perhaps... can that be relit?)

The Orbiter + payload + on board fuel weighs 230,000.
Nine F1 engines will deliver  13.5 million pounds of thrust, so it was a matter of working out how heavy a fully-fuelled S9-A would be. I don't think I'd have any trouble getting it off the ground, but I have an idea velocity might be a problem, with the Orbiter carrying so little fuel, Stage 1 might have to be going so fast that it could not be recovered, and the stack structure would have to be enormously strong to withstand MaxQ.

I thought I might be able to experiment with it in KSP, but that is sounding like it won't be straightforward.
Anyway, it was just a thought.......

[VQ]

Real-world, that sounds like assigning too much dV to the first stage. Maybe add a smaller external tank for the shuttle so the first stage doesn't need to be so enourmous? That would leave everything reusable except for the small ET. The SSME's could get smaller, too, to assign more mass budget to the fuel.

Modifying an F-1 to be restartable doesn't sound impossible, so I do not think that is the key feasibility problem with your plan.

[Zakalwe]

The gas generator also ran it's fuel very rich. I believe that after every firing it had to be stripped down and the carbon buildup cleaned out.

[bknight]

Is the program on a leased basis? What kind of setup is required to run?

[Allan F]

KSP is bought through Steam, and is updated regulary free of charge. Once you buy it, you own it. It requires a good deal of ram, if you want to add mods. And you need a low-end graphics card, like a GeForce 750. Make sure you run the 64-bit exe, though.