A space race challenge. Orbiter vs. Reentry

IDNeon

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OK.. first. The idea of this challenge is to make everyone better, not to tear one down.

The challenge isn't one target, it's many.

Find historical flights that aren't already "missions" (conditions and parameters already exist in the game) and the attitudes and burn rates they used. The angles of orbit they burned from....everything that can be feasibly followed...

And see how accurate the flight is without deviating or correcting it.

For instance, following every burn for Apollo 15...the Moon's position at launch can be approximately known so can wait for it to be where it was during launch day...then proceed.

With REENTRY ... I haven't played with Mission planner. If you can't just set the correct moon-earth parameters, then just time elapse.

That would give an interesting stress test on REENTRY's memory because at 280+ flight hours I think it started to get lag. It's obviously not necessary to optimize for a 15 day flight for missions that took only 6 days?

If you can set mission parameters. Do things like "moon rise at Jun 10. Then set the moon to where it is Jun 5th and time elapse to see when the moon breaks the horizon.

Let's TEST your long distance super massive particle physics too....not everything has to be done in flight. 😏
 

N_Molson

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Well I think if you have the patience and skill to go through a whole NASSP mission (there are tutorials), you'll be very close of the real figures.
 

IDNeon

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Well I think if you have the patience and skill to go through a whole NASSP mission (there are tutorials), you'll be very close of the real figures.
I want to not use any mission though because to be fair, I don't know exactly what's under the hood to make the mission work.

If the flight contains only two parameters, where the moon was relative to the Earth, for a given historical launch. Then beginning that flight and following the flight as true to history will demonstrate a lot about the fidelity of each sim.

To get the tests into accurate configuration may be tricky.

I don't know if there is a simple way to tell each sim where the moon is relative to the earth to fit historical mission conditions.
 

N_Molson

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I don't know if there is a simple way to tell each sim where the moon is relative to the earth to fit historical mission conditions.

This is called Orbital Elements. Those for Apollo are publicly available. Orbiter scenarios (what you would call "missions") are meant to work with those.

Read Orbiter.pdf from the "doc" folder, and also look in the "technotes" subfolder.
 

IDNeon

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This is called Orbital Elements. Those for Apollo are publicly available. Orbiter scenarios (what you would call "missions") are meant to work with those.
Understood. But what I think would be best is to eliminate the remaining "human" elements.

For instance if in Orbiter I put in the correct orbital elements for a given historical flight, does the space craft programs get automatically configured for that flight.

P01,P02 and V75 seems to control the EPO burn. Astronauts didn't write and I put the data themselves though they could if needed for certain failures.

Take the programs out and fly the attitude manually.

That's basically what I'm saying.

Take the parameters out and prove them.

For instance if the orbital parameter is exactly something on T-00.

Then go back a day, time elapse 24hours. Prove it.

If the orbital parameter is custom. Do the burn calculations and determine what flight plan SHOULD be. Fly it. See how accurate that is.

There can be a lot of challenges to demonstrate in each sim and each sim's limits can also be pushed.

K...I'm going to focus on my 8ball work I been doing. I think I'm on to something there or off my rocker.
 

IDNeon

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Maybe start there...
It's more fun to actually do something than to prove something through code and math.

The sims can code and math all they want.

But outside of government and private industry Sims, you're not going to get more STRESS TESTED than Microsoft Flight Simulator or X-PLANE, and they are getting slapped down all the time by Real World Pilots for "this doesn't feel like how it actually should." And those people have to be very nitpicky about very specific things, and both are supposed to be very decent for a simulator.

So why would you suggest to me I don't know the scientific method when what I'm saying is test the simulators against known parameters.
 

N_Molson

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It's more fun to actually do something than to prove something through code and math.

But it has no objective value, it is purely subjective and prone to error. That's why there is a scientifc method. So that experimental data has an objective value.

In short : doing something alone does not prove it is true, because you always do it in a specific set of conditions. In other words, maybe it was just good luck. That's where scientific method is necessary.

Karl Popper did an amazing work on those questions, from Wiki :

Falsification and the problem of induction​

Among his contributions to philosophy is his claim to have solved the philosophical problem of induction. He states that while there is no way to prove that the sun will rise, it is possible to formulate the theory that every day the sun will rise; if it does not rise on some particular day, the theory will be falsified and will have to be replaced by a different one. Until that day, there is no need to reject the assumption that the theory is true. Nor is it rational according to Popper to make instead the more complex assumption that the sun will rise until a given day, but will stop doing so the day after, or similar statements with additional conditions. Such a theory would be true with higher probability, because it cannot be attacked so easily:
  • to falsify the first one, it is sufficient to find that the sun has stopped rising;
  • to falsify the second one, one additionally needs the assumption that the given day has not yet been reached.
Popper held that it is the least likely, or most easily falsifiable, or simplest theory (attributes which he identified as all the same thing) that explains known facts that one should rationally prefer. His opposition to positivism, which held that it is the theory most likely to be true that one should prefer, here becomes very apparent. It is impossible, Popper argues, to ensure a theory to be true; it is more important that its falsity can be detected as easily as possible.

Popper agreed with David Hume that there is often a psychological belief that the sun will rise tomorrow and that there is no logical justification for the supposition that it will, simply because it always has in the past. Popper writes,

I approached the problem of induction through Hume. Hume, I felt, was perfectly right in pointing out that induction cannot be logically justified.[45]
 
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IDNeon

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I see what you're taking issue with.

Molson - the scientific method is a tool that can be used to derive an exact answer.

This "challenge" isn't meant to derive am exact answer.

It's meant to see who can fly the historical mission with only basic parameters and all the rest is user defined in flight.

And it's pass/fail, and doesn't care if the user is competent or not. It's in good fun.

The Olympics aren't a science.
 

Urwumpe

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Molson - the scientific method is a tool that can be used to derive an exact answer.

As some blue-collar guy constantly sitting around academics and playing the nasty jester, let me correct your sentence according to my personal experience:

The scientific method is a tool that can be used to derive much smarter questions.
 

n72.75

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Speaking from the NASSP perspective, I very much doubt anything is going to come close from a "simulating apollo" standpoint for a while.

Orbiter provides:
*State propagation using RK8 the numerical stability of which is documented on one of the technotes.
*Zonal gravity model up to J5 (NASSP may eventually release a tesseral harmonic plugin but we're not close to letting that one out in the wild yet)
*An implementation of the NRLMISSE earth atmosphere model.

And that's just orbiter. I have nothing against Reentry, seems like a cool game, but I doubt it does this.

NASSP I can almost guarantee that nothing apart from the original apollo spacecraft and a few simulators that were contemporary with them, can get the results we do.

We run an emulation of the apollo guidance computer, yaAGC from the virtualagc project. This allows us to run the exact software (if we have it) that was flown on a particular mission. In many cases we do have the software or have made reconstruction from memos and checksum.

We also run a physical simulation of fluid, electrical, and thermal properties for most of the inboard systems (pre J-mission at least). This is based on a heavily modified version of SPSDK, which we continue to improve.

Our maneuvers are calculated by a simulation of the origional NASA RTCC routines, which also continues to be improved.

Our sources for this stuff are a vast library of documents avaliable on the virtualagc site, and at their archives.org connection. These are scans of original apollo documentation, drawings and reports. Some of these come from NTRS, a fair number of which we have requested(successfully) be put back on the public site, some come from NARA, and others come from private collections.

Again nothing against Reentry, but I doubt it does all of this (although I've never played it, full disclosure).

The nassp project takes accuracy very seriously. It's as much about the fun of flying apollo as it is historical accuracy.
 

IDNeon

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Speaking from the NASSP perspective, I very much doubt anything is going to come close from a "simulating apollo" standpoint for a while.

Orbiter provides:
*State propagation using RK8 the numerical stability of which is documented on one of the technotes.
*Zonal gravity model up to J5 (NASSP may eventually release a tesseral harmonic plugin but we're not close to letting that one out in the wild yet)
*An implementation of the NRLMISSE earth atmosphere model.

And that's just orbiter. I have nothing against Reentry, seems like a cool game, but I doubt it does this.

NASSP I can almost guarantee that nothing apart from the original apollo spacecraft and a few simulators that were contemporary with them, can get the results we do.

We run an emulation of the apollo guidance computer, yaAGC from the virtualagc project. This allows us to run the exact software (if we have it) that was flown on a particular mission. In many cases we do have the software or have made reconstruction from memos and checksum.

We also run a physical simulation of fluid, electrical, and thermal properties for most of the inboard systems (pre J-mission at least). This is based on a heavily modified version of SPSDK, which we continue to improve.

Our maneuvers are calculated by a simulation of the origional NASA RTCC routines, which also continues to be improved.

Our sources for this stuff are a vast library of documents avaliable on the virtualagc site, and at their archives.org connection. These are scans of original apollo documentation, drawings and reports. Some of these come from NTRS, a fair number of which we have requested(successfully) be put back on the public site, some come from NARA, and others come from private collections.

Again nothing against Reentry, but I doubt it does all of this (although I've never played it, full disclosure).

The nassp project takes accuracy very seriously. It's as much about the fun of flying apollo as it is historical accuracy.
Your answer makes me want to bother with the NASSP install which I heard was a pain ...

But also can you say the Space Shuttle missions are equally as accurate or simulated as you just described?

Also for both Apollo and Shuttle do all the systems get simulated as well? Or just ones necessary for flight?
 

N_Molson

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Your answer makes me want to bother with the NASSP install which I heard was a pain ...

No, as long as you know to extract an archive and read simple instructions, you should be fine.
 

n72.75

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NASSP isn't too hard to install, but there are a few step. The official install guide is here: https://www.orbiter-forum.com/threads/nassp-8-installation-guide.36801/

As far as what systems we do and don't simulate, I can't speak to the shuttle addons SSU and SSV, because I dont developcfor them. For NASSP, it might be easier to list what we don't simulate. And even then almost everything is simulated, it's just a question of the level of detail.

If you had questions about the implimentation of a specific system in the LM or CSM, I'd be happy to discuss the implimentation.

Here's a copy of the CSM-104 (Apollo 9) systems handbook, if you want to look https://www.ibiblio.org/apollo/ApolloProjectOnline/Documents/CSM 104 Systems Handbook 19690124.pdf

The project is also free and open source, and if you want to look through our code you're encouraged to do so.
 

Urwumpe

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NASSP isn't too hard to install, but there are a few step. The official install guide is here: https://www.orbiter-forum.com/threads/nassp-8-installation-guide.36801/

And its much more easy, since you can essentially keep the installation folder most of the time and just extract the build ZIP file into it. I rarely discovered any problems that required starting with a fresh installation.

And if this happens: Just prepare the installation folder for NASSP once, ZIP it, shove it onto your external HDD or where ever you like otherwise. Now you only need to unzip two files for a new fresh test environment.
https://www.orbiter-forum.com/threads/nassp-8-installation-guide.36801/

As far as what systems we do and don't simulate, I can't speak to the shuttle addons SSU and SSV, because I dont developcfor them. For NASSP, it might be easier to list what we don't simulate. And even then almost everything is simulated, it's just a question of the level of detail.

I don't want to count as spokesperson for SSU, since I am away far too often and too long from development. Ask DaveS maybe, since he is the longer constant there.

But I can talk about my own motivation to join this project (by random events, since I was actually a Soyuz and CCCP fleet guy at that time):

I want to preserve the memory of this spaceflight program and the vision of it. The dreams and plans that people had with the Space Shuttle, even if politically unrealistic. As such, I want to show the Shuttle in SSU as it really was. Not better. Not easy. Not modern. But something that really had potential for building an infrastructure in space. Not flying itself to the moon, but letting other spacecraft fly to the moon way cheaper than possible with Apollo, and more often. Build Space Station Freedom. Or the Modular Space Station before it. I want to show, why this program actually changed spaceflight as we know it, even if people today consider it a failure. I want to let other people have as much fun learning about the past technology as we had researching for SSU.

For this, I want to simulate any subsystem, including the crew and the ground. Not the minimum set of subsystems needed for getting something that feels like a coarse Shuttle. But actually even unflown concepts and improvements, that had been supposed to make achieve its performance goals. I want to simulate the computers of that time realistic enough (despite all holes in our knowledge since this is military hardware), that people can today understand, why its more advanced computer system was actually a step back compared to Apollo in terms of useability. And why these limits in the most central component of the Orbiter were so bad. And why this actually meant that crew resource management in the Space Shuttle was way more important than for Apollo.

Currently, we have a too strong emphasis on ground systems for my taste, but again, I am not the spokesperson of SSU. I am merely a minor contributor.

Yeah, my vision about SSU isn't about being user-friendly. Or for beginners. Maybe the SSV project will do this, which is a fork of SSU.

Yeah, and for getting this done, its clear that it can only work as open-source software and without money being involved. Its essentially a science project or a virtual museum. Any kind of ownership beyond our contributions would doom it. We are open to contributions. But right now, we need a lot of work for boring debugging of what is there, before we can add new features.
 

DaveS

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Currently, we have a too strong emphasis on ground systems for my taste, but again, I am not the spokesperson of SSU. I am merely a minor contributor.
I think that is on me, as I have had great interest in the Ground Support Systems (GSS) of the Space Shuttle for a very long time. So I've pushed the focus there for a very long time. It took GLS leaving the project and starting his own project to make me realize my own flaws. I'm trying to stay within the the limits of the designated roadmap from now on.
 

Urwumpe

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I think that is on me, as I have had great interest in the Ground Support Systems (GSS) of the Space Shuttle for a very long time. So I've pushed the focus there for a very long time. It took GLS leaving the project and starting his own project to make me realize my own flaws. I'm trying to stay within the the limits of the designated roadmap from now on.

Well, its a team effort, so either all are to be blamed, or nobody.


And again, I already said it a while ago, its mostly a problem of keeping the development in balance there. If we add too many new features, in a short time, we also need time afterwards fixing the technical debts that we discovered there and prepare for the next set of features. And we have a lot of TD accumulated there.

Also: I think the road map isn't cast in stone. It was a suggestion from my side how I would fix things to get straight back to business.
 

Urwumpe

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So how does SSU simulate internal systems state, fuel cells, glycol loops, etc?

All of the examples: Not at all right now. All thermal and life support topics are still TODO. We have some simple calculations around using boyles law to get tank pressures calculated, but nothing really sophisticated.

Maybe in ten years, at the current velocity. We don't even have a real SW architecture left to implement such systems, its all down in lava cake, we have dozens of instances where different code is used for solving the same problem.

I just try to turn the RSLS code into something that isn't modern art.
 

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A goal of mine (and @rcflyinghokie13) eventually is to upgrade SPSDK to something we can call a 2.0 version. It's already pretty much a sub-module and wouldn't take much (after we're done making a few major changes to things like supercritical fluids), to have a "release" of sorts.

We also have some really useful things like the connector class, that allows us to send messages between vessels, which is how we do things like LEM pressurization/power, VHF and rendezvous radar signal strength, and docked vessel stages.
 
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