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Show HN: Rocket Launch and Orbit Simulator(donutthejedi.com)
125 points by donutthejedi 15 hours ago | 35 comments

I (17y/o) have been developing a rocket launch simulation that allows the user to explore what it's like launching a rocket from earth and putting it into orbit. This idea originally started as an educational simulation but as i've gone more down the rabbit hole the more i've wanted to make it realistic. The problem is that I've never had a formal orbital mechanics class or anything like that so I don't know what I'm missing, what I currently have implemented is:

  Variable gravity
  Variable Atmospheric drag (US Standard Atmosphere 1976)
  Multi-stage rockets
  Closed-loop guidance / pitch programs (works well within ranges 350km to 600km)
  Orbital prediction and thrusting options to change your orbit.
The feedback I'm looking for is: UI improvements and possible future physics implementations that I can work on.

Current code and physics can be found at: https://github.com/donutTheJedi/Rocket-Launch-Simulation

MadnessASAP 9 hours ago | parent | next [-]

What did you use for closed loop guidance? If you aren't aware of it NASA has a lovely paper called UPFG "Unified Powered Flight Guidance" [1] used for the space shuttle. This was implemented and made more universal for KSP (of course) by Przemysław "Noiredd" Dolata as PEGAS "Powered Explicit Guidance Ascent System" [2]

If it's your thing you could try implementing it and getting a single continuous burn to final orbit.

Awesome work BTW!

[1] https://ntrs.nasa.gov/citations/19740004402

[2] https://github.com/Noiredd/PEGAS

Edit: I now see it's on your roadmap, so I guess it is your thing.

donutthejedi 6 hours ago | parent | next [-]

For this model I kinda just made up my own system to play around with it, while it wasn't very effective it was pretty fun. That being said thanks a lot for the recommendations, I wasn't very aware of the options I had for it.

lamontcg 7 hours ago | parent | prev [-]

I've got another kos-PEG implementation here as well, along with a really extensive bibliography:

https://github.com/lamont-granquist/KSP-KOS-PEG/blob/main/li...

mstank 15 hours ago | parent | prev | next [-]

This is awesome, great work! There’s a huge audience for something like this based on the popularity of Kerbal Space Program.

Biggest low-hanging fruit UI improvement would be mobile responsiveness. It was a bit challenging testing on my phone.

donutthejedi 15 hours ago | parent [-]

Awesome, thanks alot, thats a great idea to work on

MeetingsBrowser 12 hours ago | parent | prev | next [-]

This is really neat and pretty fun to play around with!

How accurate are the simulations? I'm able to get orbit by turning 45 degrees as soon as I launch and then doing some minor burns at the height of the initial trajectory.

I don't feel like this strategy would work in real life.

donutthejedi 12 hours ago | parent | next [-]

Its fairly accurate as far as I can tell. Your right about the fact that It wouldnt work in real life due to the dynamic pressure your exerting on your rocket, using your method you get to about 150 kPa, Falcon 9 usually maxes out around 35 kPa so it would explode. Also it is a fairly fuel inneficent way of getting into orbit, but yes it is possible

Intralexical 11 hours ago | parent | prev | next [-]

Subtracting gravity losses, the largest effect of your 45 degree thrust vector would be sideways acceleration. Which is generally what you want, to get up to speed as quickly as possible, instead of wasting energy ascending vertically.

We just don't do it on Earth because we need to get out of the atmosphere first for efficiency and structural reasons. But on the moon or another vacuum body, "diagonal kick followed by minor circularization burns at apogee" is pretty close to the optimal strategy. Even on Earth, it's similar to the trajectories proposed by SpinLaunch and other "space cannon" concepts.

GalaxyNova 12 hours ago | parent | prev [-]

I think it would, given that there is no air resistance.

caetris24 13 hours ago | parent | prev | next [-]

I think it's a good start, but the user experience and the color theme make the simulation cumbersome to absorb. Maybe you can do a theming exercise with an AI. The zoom feature is highly sensitive. It's not intuitive at first on what the user should do or take away from the simulation. The events feature is great, and essential.

Looking forward to seeing the next iteration. Nice work.

brookman64k 15 hours ago | parent | prev | next [-]

Why is it launching with a horizontal velocity? It initially moves to the right even when pointing up perfectly.

donutthejedi 15 hours ago | parent [-]

Thats due to the rotation of the earth, for the purposes of the simulation the earth is rotating at 408 m/s (earths rotation at cape canaveral) so thats why It appears its going sideways

brookman64k 14 hours ago | parent | next [-]

When the rocket launches it already moves with earth's rotation at that latitude (and is stationary with respect to the ground). That's in fact the reason why many rocket launch sites are near the equator: Free velocity.

mholt 15 hours ago | parent | prev | next [-]

Don't rockets also start with the same horizontal velocity though, since nothing canceled it out when it got off the launch pad?

It would be like jumping, and finding yourself ~250-400 meters away from where you lept by the time you landed.

That said, neat project, and way fun learning experience. Good job.

DetroitThrow 15 hours ago | parent | prev [-]

But the rotational velocity of the rocket is going to be very similar to Earth's at the launch site. Eventually the rotational velocity between ground and the rocket will begin to noticeably differ, but the launch trajectory starting at 408 m/s would look terrifying if it were that way in real life.

donutthejedi 14 hours ago | parent | next [-]

I found the problem, It appears that I had the earth staying stationary but gave its rotational velocity to the rocket, What i think needs to happen is I need to also be rotating the earth so the inertial frame stays the same. Thanks for bringing this up

donutthejedi 15 hours ago | parent | prev | next [-]

Good point, I implemented that very early and hadn't really thought about it, let me look into the true solution, thanks

sfblah 14 hours ago | parent | prev [-]

I was able to fiddle with the settings so it launches in the air a bit and then hits the city. All by just going vertically. Pretty funny.

zamadatix 12 hours ago | parent | prev | next [-]

How much AI was used vs manual lines?

donutthejedi 12 hours ago | parent [-]

Around 90% AI for syntax, I did alot of debugging manually. For implementing new features I would design them and do the reasearch then have a AI write lines for me and verify the work

zamadatix 9 hours ago | parent | next [-]

It's a quick path to having something to play with but I'd encourage folks specifically wanting to learn something new or create something for a portfolio to try to have it be more the other way around: write 90% by hand, implement the features yourself, and have AI help you with the research and debugging (but not try to automatically write the code to fix the bugs). AI is really great at all of the things listed, but I guarantee if you were in an interview and someone asked you about this project your responses about how and why everything works would be 2x-3x stronger.

If this was your 3rd time implementing an orbit simulator and you just wanted to get the bulk done quick so you could move on to work on new stuff then that's when having AI write the bulk & doing checking really works best as you're already an expert in what needs to be done rather than trying to learn about what needs to be done from someone/something else doing it for you.

I say this as an orbital dynamics simulator in C++ having been one of my first big projects I put in a portfolio myself :). And I also like to use AI often, I'm not an AI hater in general, just I like to use in certain specific ways sometimes.

Feedback on the UI side: It'd be cool if the stars used more random positions rather than sine/cosine looking patterns. There are lots of different approaches one could try (from simple random positions to very complex types of clustered randomness and brightness variation to realistic star maps). My suggestion would be to ask AI what types of approaches could be taken and try implementing whichever approach sounds the most fun!

donutthejedi 6 hours ago | parent | next [-]

I completely agree with what your saying, with one caveat. If I understand how the underlying physics and dynamics are working but don't know how to write the code then theres no world where I could make something like this. The way that I see it is that AI is a tool that really depends on the person.

If I were to be someone who just tells AI "implement drag" and lets it do it then sure, im not learning, but if I do my research outside and just use AI to translate what I give it into the language of computers I feel like im not only building something cool but im understanding whats happening because AI is just translating.

So basically while yes I do believe that AI can be harmful if you approach it inproperly, it helps novice programers implement cool things by just using english.

forgotpwd16 2 hours ago | parent [-]

>If I understand how the underlying physics and dynamics are working but don't know how to write the code then theres no world where I could make something like this.

You could learn coding same way as you learned the physics and dynamics. Programming and physics aren't mutually exclusive. Actually every physicist is (was?) required to know (multiple) programming (languages).

>If I were to be someone who just tells AI "implement drag"

That'll mean at least you understand drag. Could do even worse, regards to learning at least rather result, prompting something like "make a cool-looking physically-realistic 2d rocket launch simulator", which we're at point that will most certainly return a functional app.

>but im understanding whats happening

Do you though? You depend on AI correctly translating your natural language input to code. Though arguably this is something LLMs excel at, since math (logic) also plays role you've to be able to at least read and review the resulting code for correctness. (Assuming you actually care about the physical accuracy that is.)

shireham 8 hours ago | parent | prev [-]

Curious what age bracket you’re in? I understand where you’re coming from, but I don’t think it will be the paradigm for the future. My own experience is that you actually learn a lot by having AI write piecemeal code and then do overall review.

tgig 6 hours ago | parent [-]

He is 17

pwndByDeath 9 hours ago | parent | prev [-]

This breaks my heart, software modeling orbital mechanics is something I do for fun from time to time.

arnonejoe 14 hours ago | parent | prev | next [-]

Looks super awesome. Strong work! It showed the karman line at 98-99km. Maybe a tiny tweak needed.

headcanon 14 hours ago | parent | prev | next [-]

I'm sure that city just *loves* being downrange of the launch site :)

JK, nicely done! lots of fun to watch.

TeMPOraL 13 hours ago | parent [-]

Fortunately for it, that city is mounted on some antigrav sled and moves around to always stay ahead of the launch vehicle, safe from my totally not intentional attempts at crashing into it.

Completely unrelated bug: pitch control can go down only to -5 degrees.

donutthejedi 13 hours ago | parent [-]

Took the anti grav sleds off, might be possible to crash into now idk

tgig 15 hours ago | parent | prev | next [-]

Did you do all the math yourself?

donutthejedi 15 hours ago | parent [-]

yup, derived most of the equations myself then double checked them before implementing them. That being said all of the positining is done through time steps and not so much equations

seabass-labrax 12 hours ago | parent [-]

Nice work! Had a "blast" playing it ;)

Teever 13 hours ago | parent | prev | next [-]

This is really neat.

I've been toying with the idea of building something similiar but with a bunch of different space stuff, like a calculator for different rotating space station geometries, mars/lunar cycler orbits, or solar shade sizes/distances.

It's been many years since I've done this kind of stuff in school and it's great to be able to refresh yourself on this stuff. The kind of UI you're using makes it really friendly and approachable, like a game.

fartfeatures 14 hours ago | parent | prev [-]

Much better than KSP2