Project for my Rocket Propulsion Class

[theplayingdead]

Hi everyone! I'm new to the forum, so I'm sorry if this is not the place.

I am taking rocket propulsion this semester and we have a term project which I want to demonstrate in KSP.

The mission objective is that we have 2 astronauts and 4 tourists which we will take to 110 km (361,000 feet in freedom units) with a rocket and come back. We don't need to have an orbit. Tricky part is that we will attach rocket to a plane. So that, plane will take us to 10 km (30,000 feet). From then, rocket will launch itself from the plane and reach 110 km altitude. Rest is free fall (without burning hopefully).

I have installed real solar system and realism overhaul mods. My question is that can I demonstrate my project with the current mods installed? Is there a stock plane I can use? (I will create the rocket myself). Most of the stock planes don't work with the realism overhaul mods due to different sizes.

Thanks in advance!

[DerekL1963]

Welcome to the forums!
 

2 hours ago, theplayingdead said:

I have installed real solar system and realism overhaul mods. My question is that can I demonstrate my project with the current mods installed? Is there a stock plane I can use? (I will create the rocket myself). Most of the stock planes don't work with the realism overhaul mods due to different sizes.

You can demonstrate your project in KSP, yes.  It won't bear much relationship to reality, but you can demonstrate it.

The problem isn't whether or not you have the appropriate mods installed (in fact you can demonstrate your concept in stock).  The problem is that KSP is a low fidelity simulator no matter how many or what what mods you have installed.  Particular concerns for your project are the lack of fidelity in modeling the atmosphere, and the extremely wonky way that engines work (ISP varies with altitude).

It'll make for a cool presentation, but I don't think you'll get much in the way of useful engineering information.

[Tyko]

24 minutes ago, DerekL1963 said:

extremely wonky way that engines work (ISP varies with altitude).

....but ISP DOES vary with altitude  -  technically it's the atmospheric pressure, but that's tied to altitude. 

Also, "imperfect" /= "low fidelity". It gets a lot right, more than most simulations that aren't designed for industrial or research applications. The atmosphere is challenging. The OP would have higher "fidelity" if they stuck to a rocket and skipped the plane portion. either way it's an effective demonstration of many of the concepts even if it's not accurate enough for NASA.

Edited October 30, 2018 by Tyko

[DerekL1963]

6 minutes ago, Tyko said:

.but ISP DOES vary with altitude -technically it's the atmospheric pressure, but that's tied to altitude. That's a real thing

I stand corrected...  Then what is the wonky backwards thing?  I knew there was one.
 

8 minutes ago, Tyko said:

either way it's an effective demonstration of many of the concepts even if it's not accurate enough for NASA.

I specifically said he could demonstrate his concept in KSP.  But I also pointed out the potential pitfalls in using it as a simulation tool rather than a demonstration (or more accurately presentation) tool.  KSP is what it is, and isn't what it isn't...  And that's something that someone taking (I presume) a college level course needs to know so he can make an informed decision as to how much time to invest in learning the peculiarities of the game and what he can expect to get out of that investment.

Why you're taking me to task for making it clear what KSP can and cannot do is beyond me.

[Tyko]

1 minute ago, DerekL1963 said:

I stand corrected...  Then what is the wonky backwards thing?  I knew there was one.
 

I specifically said he could demonstrate his concept in KSP.  But I also pointed out the potential pitfalls in using it as a simulation tool rather than a demonstration (or more accurately presentation) tool.  KSP is what it is, and isn't what it isn't...  And that's something that someone taking (I presume) a college level course needs to know so he can make an informed decision as to how much time to invest in learning the peculiarities of the game and what he can expect to get out of that investment.

Why you're taking me to task for making it clear what KSP can and cannot do is beyond me.

You claimed ISP was "extremely wonky" when it wasn't - I see you edited your post on that. I believe I'd heard that they handled atmospheric effects on rocket engines differently early on, but that was changed before I started playing when 1.0 released - so a few years ago. 

 

[DerekL1963]

1 minute ago, Tyko said:

You claimed ISP was "extremely wonky" when it wasn't - I see you edited your post on that.

Huh?  No, I didn't edit my post.  (Scroll up and look.  The forum software adds a note when you edit a post - the same as it did when you edited yours.)

[Tyko]

20 minutes ago, DerekL1963 said:

Huh?  No, I didn't edit my post.  (Scroll up and look.  The forum software adds a note when you edit a post - the same as it did when you edited yours.)

That wasn't an accusation. It's helpful to sometimes clean up errors. When I scanned it I missed it  

[theplayingdead]

12 hours ago, DerekL1963 said:

It'll make for a cool presentation, but I don't think you'll get much in the way of useful engineering information.

This is basically the reason actually. I'm doing it just for fun. And also showing the g force, dynamic pressure values from the flight recorder can be valuable to some point. 

I don't an extreme simulation anyway. Thank you for the interest!

[Pecan]

19 hours ago, DerekL1963 said:

I stand corrected...  Then what is the wonky backwards thing?  I knew there was one.

IIRC Originally KSP changed fuel consumption rate with pressure rather than isp but it was changed years ago.

[Pds314]

On 10/30/2018 at 2:54 PM, Tyko said:

....but ISP DOES vary with altitude  -  technically it's the atmospheric pressure, but that's tied to altitude. 

Also, "imperfect" /= "low fidelity". It gets a lot right, more than most simulations that aren't designed for industrial or research applications. The atmosphere is challenging. The OP would have higher "fidelity" if they stuck to a rocket and skipped the plane portion. either way it's an effective demonstration of many of the concepts even if it's not accurate enough for NASA.

I'm not sure it's "not accurate enough for NASA" if we are including realism mods. Apart from the radiation pressure,  ground effect, the oblateness of rotating planets and moons, and wind currents, none of the external ballistics things KSP with mods actually models would be particularly useless to NASA, especially back in the 60s and such when NASA was doing everything on slide rules and computers the size of refrigerators with less computing power than GameBoy color. Now, structural physics and plumbing wise, even the Germans had KSP beat in the 40s, but that's a different topic.

Could NASA have run a real-time aerodynamic model with the accuracy of FAR in the 1960s? Probably not, considering that basic things like the area rule were not discovered in Germany until 1943, not known by anyone in the US until 1947, and not widely or fully understood even by Whitcomb himself until 1951. Aerodynamics has progressed since then and FAR and whatnot reflect this. Computing power has also progressed and it is highly unlikely that NASA would have been able to run realtime (or any) simulations that could throw as much computing power into determining aerodynamic forces on a flexing vehicle in flight, especially if it was unorthodox in its design.

NASA really didn't use some kind of high efficiency computer model for their aerodynamics back then. models were limited and idealized. Their method of testing the more complex aerodynamic designs was largely restricted to physical testing in a wind tunnel.

Some PARTS are modeled badly, and so is structural physics, but that's a rather different issue.

Particularly for putting a rocket-boosted capsule in the upper atmosphere from a plane, I think the NASA of the 60s would probably LOVE to have something like realism-modded KSP and a computer that could handle it. It would have saved them huge amounts of effort and time and reduced the necessary number of wind tunnel tests and human pencil and paper and slide rule computations enormously.

Like, let's remember, even in the 70s, the early Soyuz rockets used the "point at space and turn on rocket" method. There was no computer system controlling the lower stage. NASA was a little bit more computerized by then but not by much. Certainly the idea of modelling a rocket in flight with no windtunnel testing would have been daunting and probably involve resorting to a pretty huge degree of approximation.

Edited November 1, 2018 by Pds314

[Tyko]

17 minutes ago, Pds314 said:

I'm not sure it's "not accurate enough for NASA" if we are including realism mods. Apart from the radiation pressure,  ground effect, the oblateness of rotating planets and moons, and wind currents, none of the external ballistics things KSP with mods actually models would be particularly useless to NASA, especially back in the 60s and such when NASA was doing everything on slide rules and computers the size of refrigerators with less computing power than GameBoy color. Now, structural physics and plumbing wise, even the Germans had KSP beat in the 40s, but that's a different topic.

Could NASA have run a real-time aerodynamic model with the accuracy of FAR in the 1960s? Probably not, considering that basic things like the area rule were not discovered in Germany until 1943, not known by anyone in the US until 1947, and not widely or fully understood even by Whitcomb himself until 1951. Aerodynamics has progressed since then and FAR and whatnot reflect this. Computing power has also progressed and it is highly unlikely that NASA would have been able to run realtime (or any) simulations that could throw as much computing power into determining aerodynamic forces on a flexing vehicle in flight, especially if it was unorthodox in its design.

NASA really didn't use some kind of high efficiency computer model for their aerodynamics back then. models were limited and idealized. Their method of testing the more complex aerodynamic designs was largely restricted to physical testing in a wind tunnel.

Some PARTS are modeled badly, and so is structural physics, but that's a rather different issue.

Particularly for putting a rocket-boosted capsule in the upper atmosphere from a plane, I think the NASA of the 60s would probably LOVE to have something like realism-modded KSP and a computer that could handle it. It would have saved them huge amounts of effort and time and reduced the necessary number of wind tunnel tests and human pencil and paper and slide rule computations enormously.

Like, let's remember, even in the 70s, the early Soyuz rockets used the "point at space and turn on rocket" method. There was no computer system controlling the lower stage. NASA was a little bit more computerized by then but not by much. Certainly the idea of modelling a rocket in flight with no windtunnel testing would have been daunting and probably involve resorting to a pretty huge degree of approximation.

I totally agree with you. I was responding to the post further up that claimed KSP was "low fidelity" and i was supporting KSP as a really solid platform. When I said "not accurate enough for NASA" I was referring to current times, not 60 years ago. So, we are both in agreement on this.

Edited November 1, 2018 by Tyko

[Pds314]

Just now, Tyko said:

I totally agree with you. I was responding to the post further up that stated KSP was "low fidelity" and i was supporting KSP as a really solid platform. When I said "not accurate enough for NASA" I was referring to current times, not 60 years ago. So, we are both in agreement on this.

I mean, to be sure, KSP can't do everything NASA does now or then, but yeah, the idea that NASA or the Soviet space program of the 60s were using really good computer modelling for their external ballistics is pretty wrong.

[Pds314]

Like, if they could reverse engineer it, the US of the 60s would consider even KSP's very limited networking, hashing, and cryptographic code to be worth more than a literal mountain of oil being controlled by a western-friendly capitalist dictator and could probably change the balance of power in the cold war. 

Data structures and algorithms used by KSP? They would be of considerable value too. Some of them were important and not known in the US until after the fall of the USSR. Many made big O improvements to what was known then and many were not available to ANYONE until the 70s or 80s or later.

Even the graphical front end of KSP would be extraordinarily valuable in 1960 on a "this changes international politics" sort of level.

Edited November 1, 2018 by Pds314

[Norcalplanner]

With RSS and RO and appropriate RO-configured parts, I would say yes, you should be able to get in the ballpark showing whether your design concept might possibly work.

[KerikBalm]

Is this a 4 year university course?

What are the exact requirements?

Ksp would be enough to show, close enough, that a vessel with a given mass ratio, a given thrust and Isp profile, a given payload, and a given drag coefficient, can more or less reach the desired altitude and return the payload safely.

It doesn't allow you to simulate a tank design, nor an engine design, nor a capsule design, nor a parachute design... etc.

You'd have to do that work outside of KSP and then enter the parameters... Realism overhaul will give you parts with parameters close to real life... but a lot depends on what exactly they want you to do for this term project.

[theplayingdead]

20 minutes ago, KerikBalm said:

Is this a 4 year university course?

What are the exact requirements?

Ksp would be enough to show, close enough, that a vessel with a given mass ratio, a given thrust and Isp profile, a given payload, and a given drag coefficient, can more or less reach the desired altitude and return the payload safely.

It doesn't allow you to simulate a tank design, nor an engine design, nor a capsule design, nor a parachute design... etc.

You'd have to do that work outside of KSP and then enter the parameters... Realism overhaul will give you parts with parameters close to real life... but a lot depends on what exactly they want you to do for this term project.

Yep it is 4 year university course. There are a lot requirements, I'm not planning on doing an exact simulation. There are requirements like nozzle area ratio, diameter etc. There is also a g limit for astronauts. 

Most of the work of the project will be done on paper. We will also calculate some thing in Matlab. Demonstrating in KSP is just for fun, but you are correct. I should finish project on paper then start in KSP.

[wumpus]

10 hours ago, Tyko said:

I totally agree with you. I was responding to the post further up that claimed KSP was "low fidelity" and i was supporting KSP as a really solid platform. When I said "not accurate enough for NASA" I was referring to current times, not 60 years ago. So, we are both in agreement on this.

Near as I can tell, NASA was basically using patched conics for all ~20th century simulations.  Certainly they did for the Voyager flights, which certainly made gravity assists known to the public.  I think the "weird ways to abuse gravity" (https://en.wikipedia.org/wiki/Interplanetary_Transport_Network)  weren't pushed until the 1990s.

As far as the computational power that NASA had, the absolute most powerful computer of the Apollo era was the CDC6600, and that wasn't available until September 1964 (no idea if NASA had one.  Only 50 were made and sold at over $2,000,000 a pop).  The thing had a *most* a megabyte of space (all hand crafted core memory, I really don't think NASA or the contractors used anything else) and could run (with extremely carefully assembler, and expect *everything* run on a CDC6600 to be hand crafted assembler) 2 MIPS (that *might* be 2 MFLOPS, but I'm not willing to bet it).

So I really don't think NASA could run FAR even if they had the code.  They didn't have computers capable of it.  I'd also assume that all the software knowledge to be found in the source code to be abstract theoretical use only: they couldn't run it on their computers and most of it was for relatively theoretical interest only (networks were small enough to be trivial).  Fun fact: the error-correcting code used in SSDs and I think at least one TV specification (and probably a *lot* of wireless use) is called LDPC.  It was invented by one Robert Gallager and used for his doctoral thesis (1960) as a possible means of achieving Shannon's theoreticly perfect error correction code (Shannon showed that it could exist by randomly generating enough codes until it magically appeared.  A system that obviously scales poorly).  Gallager later went on to "write the book" on error correcting codes, where he didn't even bother to include his own code because no conceivable computer could use it.  Much later (1990s) somebody invented the "turbo codes": these were codes that could essentially achieve Shannon levels of correction and simply changed everything (the jump in performance was so high plenty of guys in the field insisted it was a hoax).  Since they were patented, there was a certain reason to try to find other methods of achieving the same thing (since it was clearly possible).  Eventually somebody dug up Gallager's LPDC codes that were now possible to run.

So even if you dumped a ton of 21st century software tech on Apollo era computer scientists, it might make more than a few deep level changes in fundamental assumptions but in practical aspects there would be a great likelyhood that everything would be forgotten before it could be put to use.

[DerekL1963]

11 hours ago, Pds314 said:

I'm not sure it's "not accurate enough for NASA" if we are including realism mods.

I am completely certain that, even with realism mods, it's not "accurate enough for NASA".  There's not one mod out there that models shockwaves and their interaction with the aircraft for example.  (They don't simulate actual airflow at all for that matter.)  No do any of the mods (I am given to understand) simulate body lift.  Nor do any of the mods deal with the airflow to an intake changing with speed, altitude, and angle of attack.  (You stick an intake on, you've got Intake Air and Bob's your paternal sibling.)  The list of things realism mods don't simulate (or only simulates in an extremely simplified fashion) is much, much longer than the list of things it does.
 

11 hours ago, Pds314 said:

Particularly for putting a rocket-boosted capsule in the upper atmosphere from a plane, I think the NASA of the 60s would probably LOVE to have something like realism-modded KSP and a computer that could handle it. It would have saved them huge amounts of effort and time and reduced the necessary number of wind tunnel tests and human pencil and paper and slide rule computations enormously.

Nope.  Not only does KSP (even modded) not properly simulate the aerodynamics of the aircraft+rocket...  (There's zero aerodynamic interaction in KSP between the aircraft and the rocket.  KSP literally doesn't care how close the rocket is mounted to the aircraft - in real life this is vitally important.)  It emphatically does not simulate one the hardest parts - the separation dynamics.  (The aforementioned aerodynamic interaction, among other things.)  Nor does KSP accurately  simulate the structural dynamics (the 'twang' the dropping vehicle experiences when it suddenly becomes tons lighter).   etc... etc...

So yeah, KSP can seem "accurate enough" if you have a limited understanding of the issues...  But once you do understand the issues, that illusion vanishes like a soap bubble in a thermonuclear fireball.

(And I must say, I don't grasp the point of setting up and knocking down the "NASA in the 60's" strawman.)

[wumpus]

4 hours ago, DerekL1963 said:

(And I must say, I don't grasp the point of setting up and knocking down the "NASA in the 60's" strawman.)

I'd be impressed if KSP could outperform a 1960's wind tunnel and various other physical modeling systems.  Just because they didn't have computers, doesn't mean they couldn't design rockets.  There did exist one computer in Germany while the V-2 was in use (the Zuse machine), but that was more an "art project" and presumably the officials would confiscate it as a "waste of valuable materials" if they ever found it.  I've been reading "Rockets and People" off and on (volume 2 started with mostly descriptions of political offices, and got rather dull), and computers didn't seem to be critical to early Russian rocketry.  NASA might have been able to simulate flow inside of a rocket nozzle, but from what I've heard they simply constructed the models and kept blowing them up until they could build a single nozzle for an F-1 engine.

KSP hardly cares about that, all it has to bother with is working "LEGO" pieces.  And nothing about KSP rocket designs are all that realistic (except maybe the balance of fuel, thrust, and mass.  Certainly not any structural issues).  Mission simulation might be pretty good, but still I'm not aware of popular "reliability issue" mods where things tend to go wrong (gyro failure!) and you have to diagnose things with limited diagnostics and hour-long pings.  I've heard detailed reports of NASA teams dealing with issues from Chandler, and it sounds nothing at all like a game of KSP.

That said, while KSP isn't good enough for NASA (cue "four words you can't say at NASA").  Good enough for theplayingdead's class/classmates?  I'd certainly hope so.  I can't imagine the class in rocket science that couldn't be improved with KSP.

[Nich]

Pros:

KSP is the most cost effective, highest fidelity simulation a college student could afford.  If you are using it for pure demonstration purposes you should be fine.

Cons:

Project will appear unprofessional because it is based off a game.  You will need to have lots of other documentation to show the soundness of your design.

 

At the end of the day you need to ask your self what is the purpose of the assignment?  Are you using KSP as a short cut?  If so you will likely be deducted points.  How long do you have to complete the project?  If it is a semester long senior project I would not spend more then 5% of my time on KSP.  If it is less then a month I would think it would be fine.  If you use the derived equations (which in them selves are only approximations) from class to design a craft and test it in KSP.  You should be fine for any BS program.  I only have a BS in Aerospace engineering so I do not know know about masters or post doc work.

At the end of the day you need to make an outline of the work you want to do (including KSP) and run it past your professor to make sure it is within the scope of the project.

[Drethon]

44 minutes ago, Nich said:

Pros:

KSP is the most cost effective, highest fidelity simulation a college student could afford.  If you are using it for pure demonstration purposes you should be fine.

Cons:

Project will appear unprofessional because it is based off a game.  You will need to have lots of other documentation to show the soundness of your design.

 

At the end of the day you need to ask your self what is the purpose of the assignment?  Are you using KSP as a short cut?  If so you will likely be deducted points.  How long do you have to complete the project?  If it is a semester long senior project I would not spend more then 5% of my time on KSP.  If it is less then a month I would think it would be fine.  If you use the derived equations (which in them selves are only approximations) from class to design a craft and test it in KSP.  You should be fine for any BS program.  I only have a BS in Aerospace engineering so I do not know know about masters or post doc work.

At the end of the day you need to make an outline of the work you want to do (including KSP) and run it past your professor to make sure it is within the scope of the project.

I think this is a pretty good way of looking at it.  Using KSP as purely graphical simulation to kind of show in the background as you discuss the real physics will probably work.  Using it for a physics simulation, needs a very careful analysis.  If you can show where KSP works for real world and doesn't, you could have something neat, you could also have a lot of tangential work that doesn't really add much value to the project

[theplayingdead]

6 hours ago, Nich said:

Cons:

Project will appear unprofessional because it is based off a game.  You will need to have lots of other documentation to show the soundness of your design.

There is a HUGE misunderstanding in the thread. I will not make a presentation based on KSP. We, as a group, will do everything on paper by looking at equations and studying on the topic. We will never use KSP to make a design. I will demonstrate on KSP AFTER the work is finished. We will decide everything based on the things we have learned in the class.

Even though I have installed RSS and RO, I know that KSP can not be used professionally or as a simulation. It is just for fun for the project. We will maybe use a 1 minute of footage from the KSP in our presentation. Main reason I want to do this is that I want to play KSP with an objective and fun thing for the whole class. 

So my main question remains, is there any craft file for stratolauncher plane? I realized that I wasn't very clear in my description. Sorry for that!

[wumpus]

23 hours ago, Nich said:

Pros:

KSP is the most cost effective, highest fidelity simulation a college student could afford.  If you are using it for pure demonstration purposes you should be fine.

Cons:

Project will appear unprofessional because it is based off a game.  You will need to have lots of other documentation to show the soundness of your design.

 

At the end of the day you need to ask your self what is the purpose of the assignment?  Are you using KSP as a short cut?  If so you will likely be deducted points.  How long do you have to complete the project?  If it is a semester long senior project I would not spend more then 5% of my time on KSP.  If it is less then a month I would think it would be fine.  If you use the derived equations (which in them selves are only approximations) from class to design a craft and test it in KSP.  You should be fine for any BS program.  I only have a BS in Aerospace engineering so I do not know know about masters or post doc work.

At the end of the day you need to make an outline of the work you want to do (including KSP) and run it past your professor to make sure it is within the scope of the project.

Note: if you are doing something covered by Orbiter, Orbiter will be a better simulation.

I'd also recommend that KSP (with RSS/RO) would be a great quick and dirty means of doing a sanity check after coming up with "correct" thrust, mass, and delta-v values on a spreadsheet.  This is especially good if you are limited to using existing engines (which would exist in RSS/RO).  Things don't always work in KSP straight off the spreadsheet.  Real rocket science will be even worse straight off the spreadsheet (regardless how accurate you might have made the spreadsheet).

And it is absolutely ideal for visualization in your presentation.  Just include all the calculations and don't rely on KSP (especially KSP's 32 bit float's done in Unity's physics simulations).

[the rest is on the rocket]

I'd think that a Stratolaunch should exist.  You might simply cheat and hack the thrust/lift of a B-52/L1011 (both have launched Pegasus, so at least one should have a file around somewhere), at least until everything is finished.

I'd avoid tying a launch to Stratolaunch (mostly IRL, an academic project is fine).  The biggest issue used to be that your rocket is essentially at a dead end because your mass is defined by the plane itself and there is no where to grow.  Well that *was* the biggest issue, the new biggest issue is that without Paul Allen, who's going to keep paying to make it fly?  Even Orbital (who was founded on such an approach) hasn't been all that interested in supplying a rocket for Stratolaunch.