#atomic rocket

The Schwilca-4 rocket from my Star Trek Lower Decks fic Surviving Schwil. It shares a propulsion bus in common with the several cargo rockets which travelled in constellation with it, but it's the only one that also has to be able to return to the Ocean after the mission is done.

A launch vehicle I recall from home. I don't remember the name, but I'm sure "nuclear" was in there somewhere.

Here's what I told our friend Sofia about it.

left: overview of the entire launch vehicle. since i don't know mellanish anymore i don't know what it's called. Drawing a blank. Anyway. It's a nuclear rocket. The first stage is a cluster of solid rocket motors which gets the rocket flying fast and high and out of the thickest part of Gymnome's atmosphere, where the solid core nuclear thermal rocket can take over.

The rocket uses a water tank for propellant during stage 2A (the initial burn), because although the efficiency (Isp) is low for a waterlogged NTR, the thrust is as high as conventional hydrogen/oxygen chemical rockets but in a much smaller tank size. (this is because SCNTRs and Chemical rockets are both constrained in temperature to about the same amount, and so the thrust power is the same and all that can change is the mass flow rate.)

Once the rocket has accelerated up such that it no longer needs to worry about falling down, the vehicle can switch to Stage 2B, and start running hydrogen through the NTR. The thrust is lower, but the velocity gain per unit mass of fuel is much higher due to the fact that the hydrogen can be accelerated to a higher speed than the water. (with all that pesky oxygen).

It was noticed at some point that these rockets were really well suited for orbital refueling. This is still fairly early all things considered so that kind of infrastructre had been thought about a lot, but not actually built. The first time it was tried was in a sort of self contained way.

on the right you can see a diagram of the upper stage with a different payload, which I think was maybe used OH! I thought it was an ice giant probe or something but I bet this was from after the Zaldans left and the space program was rushing to figure out why, so they needed something to zip over to Oldsky around Omen real fast. Maybe. Point is, you need a small payload going very fast.

normally with an LH2/LO2 chemical rocket you would just build a small upper stage that can fit on top of the lower stage, and use that to kick the payload. But for whatever reason they decided to make good on the theoretical refuelability use case of the rocket stage in a goofy self-contained way.

They just added a hydrogen tank (which was actually straight off of an LH2/LO2 chemical rocket upper stage), and plumbed it into the water tank. They plumbed it into the water tank instead of the LH2 tank because, well probably partly just to show that they could. But also because of the ullage gas (shown in transparent orange in the diagram). Ullage gas, usually helium, fills up the empty part of a fuel tank to keep the propellant from boiling away as it's used. There's separate spheres of helium used for the job. With propellant still inside of the main hydrogen tank, but the water tank totally emptied (aside from the little reservoir used for cooling the reactor on startup and shutdown), it would be easier to force the hydrogen into the water tank than to simply refill the hydrogen tank.

at least, that was the theory.

it didn't work, but i don't recall why. If I had to guess, some component was overlooked when testing the water tank and associated plumbing's ability to work with frigid liquid hydrogen.

Guzcomic 7: Oh No.

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Impeller announced that their hard-science space combat simulator, Starfighter Inc. has joined the small number of computer games to have been awarded the coveted “Seal of Approval” by the renowned hard science fiction reference site Atomic Rockets, and joins the illustrious company of Kerbal Space Program, Independence War, and Children of a Dead Earth. See details here: http://www.projectrho.com/public_html/rocket/sealofapproval.php#id–Computer_Simulation–Starfighter_Inc

The studio also released details on two upcoming opportunities to interact with the development team: a Starfighter Inc. Q&A is scheduled on Twitch this evening at 9PM Eastern (Fri., 03/31) at https://www.twitch.tv/impellerstudios and a Reddit AMA on the game’s narrative is scheduled for tomorrow at 1PM Eastern (Sat., April 1) at https://www.reddit.com/r/IAmA/.

Some highlights from the dev team’s recent Reddit AMA (aka Ask Me Anything) titled: “How do you make hard science space combat fun?“, which lasted several hours and shot to the 2nd most popular AMA last weekend:

How realistic is Starfighter Inc. going to be? Spaceships move according to Newtonian physics – no friction to stop you once your engines are off, you need to use your engine to decelerate and it takes just as long, etc. Components are modeled according to their physical properties which influences their mass and destructibility – they have the expected density, yield stress, heat capacity, sublimation heat and so forth. Waste heat is treated according to actual thermodynamics – all parts that use power generate waste heat which has to be moved to radiators, which emit according to their emissivity and temperature according to the actual Stefan-Boltzmann law. Weapon requirements are based on conservation of energy – projectile weapons are modeled based on the requisite kinetic energy, the strength of a bomb or nuke is according to its real-world yield, etc. The pilot reactions are based on medical data – you can be knocked out by centrifugal force from rotating too quickly or suffer from radiation sickness… Our job is to figure out the implications of the relevant principles, and figure out how to express that in an intuitive manner.

Why are starfighters being used instead of long range missiles or unmanned drones?

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Long range missiles can be shot down, disabled or outrun just by running for long enough, and if you’re willing to give a missile a more fuel efficient nuclear drive to keep up, you might as well strap a gun on it to turn it into a drone/fighter and save the cost. Moreover, both missiles and drones can be hacked or knocked out via EMP, where a human pilot could at least serve as a failsafe.

Why are the starfighters fighting at such close ranges? Current missions take place in the gaps of the rings of Saturn which really are only tens of kilometers across, and carriers can deliver fighters on-site eliminating much of the distance anyway. All weapons do better at close range – projectiles (from guns and missiles) because there’s less time for the target to evade or attempt to shoot down or disable them, lasers because they lose focus and intensity with distance. Improving this involves upsizing so much that only capital ships could carry them, ships which are overkill for almost any situation and whose involvement could spark open war.

How do spaceships fly? There’s no friction to slow ships down, so once you take your hand off the throttle, you’ll keep flying in the same direction. Slowing down is accomplished via retrothrusters or flipping 180 and using the main engine, and takes just as long as getting up to speed. As a result, ships do not bank; instead, they must persistently thrust towards the center of the desired arc, with an enormous turning radius that only grows with speed. They can point any way they want while moving; motion is independent of heading. Best of all, there are no artificial speed limits; you can accelerate as long as you have propellant to thrust.

What governs ship design? #gallery-0-8 { margin: auto; } #gallery-0-8 .gallery-item { float: left; margin-top: 10px; text-align: center; width: 33%; } #gallery-0-8 img { border: 2px solid #cfcfcf; } #gallery-0-8 .gallery-caption { margin-left: 0; } /* see gallery_shortcode() in wp-includes/media.php */

Several physical principles must be respected – radial symmetry must be maintained for balance which impacts engine placement, kinetic weaponry must be placed near or through the center of mass to reduce recoil-induced spin, and the same goes for the cockpit to reduce centripetal force on the pilot – all the while keeping ship system placement and modularity in mind. Furthermore, each ship must have a unique aesthetic while still maintaining the feel of the intended corporate manufacturer.

How do the various game mechanics arise? There are pretty much two deciding factors on game mechanics – does it describe something that is physically possible, and is it fun? If only one applies, fix until both do. Most mechanics arise from studying the actual physics and exploring the implications.

Sound in space? That’s the Decision Support System (DSS) at work, simulating visuals and audio to improve combat awareness. As a system it can be disabled like any other, at which point the gameplay returns to the bleak eerie silence of the void – or at least, as close as it gets. Some sounds are transmitted from within the ship.

Have you heard of these titles? A lot of good media references were brought up in the AMA – novels like Honor Harrington and the Hyperion Cantos, games like Allegiance, Independence War and Freespace, and TV series like The Expanse. Starfighter Inc.shares elements with several franchises that everybody has been waiting to see come to life.

About Impeller Studios & Starfighter Inc.

Starfighter Inc. is a hard-science PC & VR multiplayer space combat sim in development by Impeller Studios, a 20+ international team. With rigorous attention to scientific detail, this game is set in a plausible future 200 years from now. Players are mercenary pilots who fulfill contracts for corporations and other organizations that have settled into our solar system. A rich background narrative provides context for the events and battles the players are part of.  The development team is led by industry veterans Jack Mamais (MechWarrior 2, Crysis), David Wessman (X-Wing and TIE Fighter series), Rusel DeMaria (original X-Wing and TIE Fighter fiction), and Tim Hoffman, who is overseeing the overall look and feel and renowned for his visual effects work on film and television projects like Rise of the Planet of the Apes, Thor: Ragnarok, Spiderman: Homecoming, Serenity and Game of Thrones. Tim has also worked in the games industry for many years as an art director and visual effects specialist on games like MechWarrior 2: Ghost Bear’s Legacy and Heavy Gear 2.

For additional information on the project, please see:

Kickstarter: https://www.kickstarter.com/projects/impellerstudios/starfighter-inc-0

https://impellerstudios.com/

http://starfighterinc.gamepedia.com/Starfighter_Inc_Wiki

https://www.facebook.com/impellerstudios/

https://twitter.com/ImpellerStudios/

https://www.twitch.tv/impellerstudios