# Software?

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#### tmcqueen

##### Active Member
It looks like a lot of people are using RocketSim. I have tried both the demo version of RocketSim and SpaceCad 3, and I like them both. SpaceCad has the added bonus of being about 2/3 the price of RocketSim. Does anyone have any compelling reason to pick one over the other?

#### cls

##### Well-Known Member
rocksim is more widely used. you can get 1000+ rocksim design files from EMRR! rocksim has a bigger parts library. rocksim can be made to do more, including tube fins and other wacky fin designs, and boost gliders. rocksim will show you all the numbers, at every millisecond of the flight.

I have both. mostly I use rocksim but I use spacecad for a few things that rocksim doesn't do, mostly for printing parts templates. when you're just starting out, spacecad is easier and faster for real quick n dirty designs, and better for new rocket designers, like kids.

support (fixing bugs in the software!) for rocksim has been better than for spacecad.

##### Well-Known Member
Originally posted by tmcqueen
It looks like a lot of people are using RocketSim. I have tried both the demo version of RocketSim and SpaceCad 3, and I like them both. SpaceCad has the added bonus of being about 2/3 the price of RocketSim. Does anyone have any compelling reason to pick one over the other?
If you really....and I mean really experiment with both programs, you'll begin to see what seperates them. Some of my pet peeves of SpaceCad are:
-Centering ring patterns do not take into account motor tubes.
-It only allows you to design symetric fin patterns.
-It will not print out larger fin patterns (all though I have heard this problem is being fixed)
-The data base of items and materials that it comes with is somewhat limited when compared to RockSim
-Motor database is also somewhat limited. (Try and pull up an Estes C11!)
-When designing fins, you are limited interms of the number of "points" or shape you can make the fin.

Some of my likes!
-Very easy to use
-Cheaper than RocSim
-Easy to navigate
-Cheaper than RocSim

Try out the demos until you can't see straight...then make your decision!
Good Luck!

#### teflonrocketry1

##### Well-Known Member
I recommend RockSim! Think of the money this program costs as an insurance policy for your rockets. By running simulations and knowing if a given flight is stable and having an idea where a given rocket will land, you will recover more flights and fly more safely. Besides the basic three or four fins and a nosecone designs, RockSim can simulate much more complex rockets. Since RockSim is written in XML format there is much more to come in the form of add-ons and synergistic softwares. I think RockSim is worth the investment especially if you are going to be flying and simulating more complex designs such as; asymmetric fin arrangements, fins attached to fins, fins at angles not through the main body tube centerline, tube fins, ring fins, parallel staged models, pop pod boost gliders, and even side pods! You can even use RockSim to simulate worst case senarios, like deployment failure, and sustainer ignition failure.

If you really have a problem with spending money on software why not try the freewares like VCP and WRASP. That's how I started out. I got rockSim because it allowed me to predict the coefficient of drag on a given model as well as accurately simulate the effects of wind speed and launch rod angle on flights. VCP can handle the simulation of the CP some more complex designs such as asymmetric fins tube fins and ring fins.

Bruce S. Levison, NAR #69055

#### Micromeister

##### Micro Craftman/ClusterNut
TRF Supporter
This is not intended to start a discussion, which it almost certainly will so I will state for the start this will be the only post I will make to this thread. I see far to many folks here and in other forums, quoting rocksim results as if they were the final word and absolutely correct. WARNING That is not ture!!!!

If no one else will, I will state that rock-sim along with all computer programs have to make certain unavoidable assumptions that create the potential for errors. Do Not rely on any computer simulation as the last word in your assessment of a models stability. Model rocket cd's are a very difficult things to calculate. EXTREME care must be used while imputing data in rocksim. Small errors in data entry WILL cause false static margins and potentially unstable models. Sloppy modeling of parts, errors in material weights and omitted parts and/or placements can and will cause results that can, will and have cause unsafe and unstable models. CHECK, CHECK, CHECK all results before flight testing any model designed in any of these sim or graphic programs, Try to test unproven models in isolation. Not at public launches.
Also be warned all rocksim altitude simulation are off by 10 to 20 percent from real world results.
Rocksim, wrasp, winroc, VPC, SpaceCad and RocketCAD are all good tools, and that is what they are TOOLS, not the gospel.
This warning isn't ment to discourage there use but to alert everone, please do not simply believe ANY of them as being absoultely correct.. THEY ARE NOT. no not one.
While Rocksim is much better in 7.1 than before it still has major flaws and limitations. At some future date and improved version Rocksim-x may be worth the 85.00 they are asking. until then keep testing and checking the results.. AeroCFD is a good program for design work and worth the money they are asking, can't say the same for Rocksim. Like all computer programs there is a learning curve, keep trying and learning but Don't trust them with the farm.
Hope this helps to open our collective eyes a little.

#### cls

##### Well-Known Member
Micromister, you are correct in noting the fundamental law of computers: garbage in, garbage out! a simulation is only as good as the the accuracy of its inputs.

how many times have we thought "well the computer says X so it must be true". many people, even experts and folks that should know better, are regularly fooled by computers because the results are so precise: "max altitude = 1093.128 feet". what does the .128 feet really mean anyways?

that said, with a bit of work I can routinely get rocksim to 95% of the "real world" flight. it takes patience and care: weigh everything that goes in to the rocket; set up rocksim's launch conditions exactly, even launch rod length, your latitude & altitude & barometer & temperature; everything.

spacecad could probably get closer than the 85 to 90% if it had as many "knobs".

much of the time that level of accuracy is "good enough". but don't be fooled by the precision of the results.

(glad to hear something positive about finsim, I will check it out! thanks)

#### teflonrocketry1

##### Well-Known Member
As a scientist I keep an eye on the details when I create a model rocket stability or flight simulation. The largest source of error in any of the computer flight simulations, no matter what the software program, is the 20% tolerance limit in the manufacturing the rocket motors! To control for this, when I conduct a flight to confirm a simulation, I choose motors that are from the midrange in that motors weight and all from the same manufacturing lot. I also make sure to program in the motors exact weight and the spent casing weight by creating a custom motor file for it. In addition to this, I make more than one flight with a given motor size and I carefully measure and program in all the variables such as: wind speed, ambient temperature, launch pad height above sea level, humidity, barometric pressure, launch rod angle from vertical (read from the dial indiactor in my launch pad) and etc. I also weigh the rocket and use this flight weight that accounts for wadding and etc. and confirm the exact CG location and match the simulation to it. I doubt anyone else goes to all this trouble.

I say RockSim is very accurate. Based on my Adept A1 altimeter measurements the altitude accuracy of RockSim is within +/- 25 feet and using a tape measure the landing diatance from the pad accuracy is +/- 50 feet. I don't think this margin of error is that bad. Of course it takes a bit of time to make all the necessary meaurements and fine tune the simulation.

Has anyone else ever tried to cover all the variables and check the accuracy of Rocketry simulation software?

Bruce S. Levison, NAR #69055

#### rkt2k1

##### Well-Known Member
Bruce,

Sounds like you have the next subject for your Rocksim article series. Having put out the dollars for the software , I would love to see an article on how to improve the accuracy of the similations!!

#### Micromeister

##### Micro Craftman/ClusterNut
TRF Supporter
To answer you question Bruce, Yes several of us log all the data you mentioned.

A study is underway at present comparing all the available altimeters & software sim programs against actual tracked flights on the same vehicle at the same time powered by the same motor. The data so far is very interesting but is not yet completed. This data will be completed, compiled and presented at this years Naram R&D.. should open some eyes.
Just and observation, what lead you to believe your adapt A1 is any more reliable or accurate than the software or the 20% verient in motor production? Actually it is one of the "more accurate" of the bunch, but you'll have to wait for the study completion for a more complete outcome.

I must again remind everyone out here, DO NOT take any programs answer as proof positive of a models stability or air worthyness. check Check CHECK! always fly unproven designs in isolation or in very limited launch setting.

#### illini

##### Well-Known Member
I'll throw in my 2 cents. I agree with Micromister. My Ph.D. thesis was in computational fluid dynamics (large eddy simulation of turbulence in compressible channel flows), and for the last several years I've developed and conducted analysis with various simulations for DoD. I have never yet come across any simulation that is a truly good substitute for the real world...including those that I've written. That is, without a *significant* calibration effort I would never claim that any simulation was a good absolute predicter of the real world. At best, I use simulations to make relative comparisons such that I can compare simulated results with other simulated results. Even then I am always careful to qualify my results based on the inherent assumptions of the simulation software AND those I imposed while setting up the simulation. Also, since every simulation differs in its assumptions, I can almost never compare the results of one simulation with the results of another unless I am comparing both with experimental data. Although I make my living in modeling, simulation and analysis, I always view simulations and simulation results with a skeptical eye.

That being said, I am a user of Rocksim. I like the design tools and static stability analysis, but agree with Micromister that it is not the final word even if I weigh every part. More detail does not equal more accuracy. Therefore, I treat the stability analysis as the approximation it is. I use the flight simulation for relative comparisons as I iterate my designs, but don't pay much attention to the absolute altitude prediction other than as an approximation. I usually ignore the recovery part of the simulation. Maybe I'm overly skeptical, but I see too many variables there to trust that I could get the simulation to reliably predict the landing spot of my rockets. In my opinion, Rocksim is performing extremely well if results are reliably found to be within +/- 20%

Just my overeducated, but experienced 2 cents.

#### cls

##### Well-Known Member
Micromister, I am VERY interested to see the results of your altimeter study!

we haven't bought one yet because we haven't really needed it. but I would like to build some rockets that do need it it's difficult to really figure out which one is the "right" one and which would be most reliable. I haven't kept stats but many HPR failures I've seen seem to relate in some way to the electronics.

that sure makes me respect what the professionals do when a big launch goes well.

#### rstaff3

##### Oddroc-eteer
Originally posted by illini868891
....I like the design tools and static stability analysis, but agree with Micromister that it is not the final word even if I weigh every part. More detail does not equal more accuracy. ....
I'm not sure that this is the case at all. Depends what details you are talking about. More detail of individual masses are not where a person's energy should be spent. Other details like entering a realistic value for the wind speed make a big difference.

teflon, please convert the +/-'s you gave early to a % of total altitude. TIA

#### illini

##### Well-Known Member
Don't get me wrong. I *like* simulations. Without simulations I'd probably have to *work* for a living. Without question, there are some circumstances where a more detailed model will give better results. However, there are a lot of situations where I've seen people spend a lot of time entering details that will improve accuracy of results by 1% when the error bars inherent in the simulation are 20%. There's also the question of what you want to learn from Rocksim simulations. Predict absolute altitude? Predict landing point? In my opinion, a good simulation will at least capture the trends such that a relative comparison is possible. Making claims of absolute performance based on Rocksim (or anything else) is dangerous. Claims of relative performance...I'm more comfortable there.

I'll be *very* interested to hear more about MM's NARAM R&D report. Would also love to hear of any other data points where people have compared simulations with experimental data.

#### rstaff3

##### Oddroc-eteer
I didn't mean to come across being argumentative. I agree with your, and micromister's, general assertions about the use of simulations. You do have to understand your model and what limits its accuracy.

BTW it's not micro's report, but rather from another member of NARHAMS.

cls - This report will be very useful I'm sure. However, it may not show what altimeter is 'best'. Most altimeter failures are probably due to interconnection or igniter/current draw issues. Others may be due to design issues, some of which won't necessarily be evident on tests based on mid-power rockets, as I believe the R&D report is.

#### illini

##### Well-Known Member
No argument perceived, just good ol' technical discussion! Whoever is conducting the R&D, I, for one, applaud the effort to perform some V&V (validation and verification) with regard to the sims. That's a report I'll be looking for.

Its true that rocketry sims have the *potential* to be more accurate than the types of sims I work with. This is due to rocketry sims dealing purely with physics (I don't get that luxury). However, they still make a number of assumptions (like micro pointed out) to make the equations of motion tractable. As micro mentioned, AeroCFD is one way to reduce the impact of those assumptions by introducing an honest-to-goodness flow solver to improve the drag calculations. However, while AeroCFD removes some assumptions it retains others. My limited reading on AeroCFD indicates that it is an ideal fluid solver using a panel method. Ideal fluids are inviscid and incompressible. Inviscid means it won't capture any skin friction drag, turbulence, separation, vortex shedding (common for cylindrical bodies at non-zero angle of attack), etc. Incompressible means that results become suspect for speeds above ~ Mach 0.3. Long winded, but this is just to illustrate some of the inherent assumptions. My point? 'taint no such thing as absolute accuracy from one of these sims, and if there was you couldn't afford it or the supercomputer necessary to run it.

Now I don't doubt that someone can generate a specific design that, when flown with the attention to detail that teflon puts into his validation efforts, will perform almost precisely as predicted by Rocksim. However, I don't believe for a moment that this is true for the set of all possible designs. Further, only a very small subset of all flights are flown with such attention to detail. Therefore, I assert that for the typical flight of a typical design, simulated performance is not likely to be very accurate. How accurate can we expect? This is what I'm hoping to find out from that NARAM R&D report.

Does this mean Rocksim (or any other sim) is bad? NO!!! (Remember, I *like* simulation!) What it means is that sim users must be aware of their sim's limitations and use it accordingly. This, I think, was Micro's original point and I agree with it without having to see any NARAM R&D data.

#### teflonrocketry1

##### Well-Known Member
Originally posted by rstaff3
teflon, please convert the +/-'s you gave early to a % of total altitude. TIA
The flight data was for an Estes Hijax which was simmed to reach around 720 ft AGL on a C6-5. So +/- 3.5% for altitude and +/- 6.9% for distance from the pad! The number of flights was only three so the data are not that significant.

It took several days of preparation to make these flights and simulations. It was difficult to find the right selection of motors and then to find and/or calibrate the weather data and instruments. The rocket itself was weighed to the nearest 0.1g before each flight, and the CG over-rode to the exact preflight CG. For the flight simulations, the dimmensions of the entire model was measured with a vernier caliper and steel ruler. I find the fin dimmensions are important for getting an accurate simualtion especially the span dimmensions; all three fins were measured and the average value for the dimmensions was used. The rocket was waxed with Future Floor Wax to give a "gloss" finish. The vent holes for the altimeter bay were 1/8 inch in diameter located 120 degrees apart. The altimeter was shielded from stray wind currents with foam rubber.

The Adept A1 altimeter was chosen since it was selected for the TARC competitions. I also cheked out its accuracy using the vacuum chamber and syringe set up that you can purchase to "calibrate" it! Since the volume of the chamber is known you can pull out a specified volume of air and calculate the decrease in pressure or apparent altitude. The altimeter seemed to agree within 5% of the calculated altitude.

Bruce S. Levison, NAR #69055

#### rocket72175

##### Well-Known Member
I also think Rocksim is very accurate and mostly sensitive to the input details. I don't know about all the lateral moment of inertia calcs, but to the best of my knowledge, there are no assumptions in the flight trajectory equations to make them "tractable". The motion simply follows F=ma, which amounts to basic ODEs that are readily solved by numerical schemes, like Runge Kutta. There are no inherent 20% error bands in the computations, since they have been readily solved to machine accuracy for 60+ years.

Drag modeling is a stumbling block, but the main reasons for any lack of correlation between sims and observations are the facts that design levels are never apples to apples and variation is rarely accounted for. The effort that Teflon puts towards these factors pay off handsomely.

Hardware tests and measuring equipment have their own error bands - calibration, fixturing, human input, etc. Just because a transducer of some sort reported a number doesn't mean it is the "real world."

Ken

#### illini

##### Well-Known Member
At the risk of being redundant, repeating myself, and saying the same things over and over again, you might want to take a look at the following lecture notes from MIT. I think lecture 16 has most of what's pertinent. Note also that the drag equations in Rocksim are rule-of-thumb approximations. To do better than rule-of-thumb you need to solve the equations of fluid dynamics...tightly coupled PDE's. Apogee offers AeroCFD that solves a reduced form of the Navier-Stokes equations, making steady-state ideal fluid assumptions to make the equations more *tractable* so that they can quickly solve the resulting potential flow equations with a panel method.

Bottom line is this: to state that Rocksim is *accurate* or *not accurate* is grossly oversimplifying things. You start here: what questions do you want to answer with Rocksim??? Do you want to predict altitude with absolute precision? Are you willing to conduct wind tunnel tests of your model to precisely determine Cd throughout the flight envelope and weigh all engines so that you will fly only with those that are identical to Rocksim specs? If so, then there is some chance that Rocksim will do what you want.

Personally, I don't fly that way. My models are built by hand, not by machines with low tolerances. I grab an engine out of my field box, ram it in my model, and fly it. It goes up and comes down. I repeat this several times and that is my day flying rockets. Never once do I recall saying to myself, "by gum, Rocksim said my rocket would fly to 732.6 feet and it did!"

I use Rocksim to answer the following questions:

1) Is my design likely to be statically stable?
2) What engines/delays are good for my model?
3) What recovery device is appropriate for my model for the field and conditions I'm flying in?
4) If it is a competition model, which design will fly higher or stay up longer?

For the first question Rocksim is reasonably accurate, but I still take precautions for that first flight.

Rocksim is accurate at helping me choose engines and delays.

Rocksim is sufficiently accurate to help me choose the right recovery device, although a specific flight may experience wind gusts or thermals that carry my rocket off the field.

Rocksim is generally sufficiently accurate to capture the trends that will help me choose between one competition design or another, but I don't trust it enough to let it have the final say.

All in all, Rocksim is accurate enough to give me the answers to my questions. Whether it is accurate enough for your purposes depends on what questions you are asking. The NARAM R&D report that's been discussed will be extremely valuable if it helps us determine which questions Rocksim can answer and to what degree of precision.

#### rstaff3

##### Oddroc-eteer

I use Rocksim to answer the following questions:

1) Is my design likely to be statically stable?
2) What engines/delays are good for my model?
3) What recovery device is appropriate for my model for the field and conditions I'm flying in?
.....

[/B]

These are really what I use Rsim for and have found it to work great.

'Nuff said on New Years Day! Hope you all have a good one! Now off the the TV whare the only stability I care about is in a ovate piece of pig skin

#### rocket72175

##### Well-Known Member
Originally posted by illini868891
...Are you willing to conduct wind tunnel tests of your model to precisely determine Cd throughout the flight envelope and weigh all engines so that you will fly only with those that are identical to Rocksim specs? If so, then there is some chance that Rocksim will do what you want.
Yes. This is the point. If you do all these things, then there is a *very good* chance that you will be happy with the correlation (if that is your goal). However, many people accept the "default" values in the software, then complain that the sim and observation don't agree to some expected tolerance.
Originally posted by illini868891
...The NARAM R&D report that's been discussed will be extremely valuable if it helps us determine which questions Rocksim can answer and to what degree of precision.
We'll know more when the report is complete, but it sounds to me like a bunch of data from altimeters, computer programs, and optical tracking - all of which will have different results. Now what? All have their own problems. Data statistics and interpretation will be key to this report. To paraphrase: "Nobody believes the simulation except the one who did it. Everybody believes the measurement except the one who did it."

#### illini

##### Well-Known Member
Originally posted by rocket72175
All have their own problems. Data statistics and interpretation will be key to this report.
On this we have no disagreement. The statistics will be key. Unfortunately, it will be very difficult for the investigators to achieve the numbers of flights necessary to be statistically significant unless there is some sort of group effort.

To paraphrase: "Nobody believes the simulation except the one who did it. Everybody believes the measurement except the one who did it."
As one who works with simulations on a daily basis, believing the sim is dangerous regardless of who did it. Same goes for measurements. That's why we have the system of peer review. Unfortunately, you are right that sims usually receive much more scrutiny than experiments. Partly this is due to people's lack of understanding of the sims. The other part is that simulation results are highly dependent on the sim user, and trusting the user is difficult (for good reason, imo)

#### teflonrocketry1

##### Well-Known Member
What really gets me is the fact no one has yet mentioned base drag or body lift! These are RockSims and most simulation softwares smoking guns! Currently the RockSim doesn't have any way to handle these important factors. This is why you can't simulate things like spool rockets and Sputniks. I think the lack of a base drag or body lift correction is responsible for a good part of the inaccuracy in my flight simulations. Athough it can handle base drag, I can't seem to get AreoCFD to simulate spool shaped rockets or even a more complicated design either. I doubt any of the simulation programs will place a CP aft the of the rocket body as I suggested may be true for spool shaped rockets.

I think everyone realizes that with any simulation; if inaccurate measurements go in, then inaccurate results come out. That being said, I have examined hundreds of simulations and I find that most people won't go to the trouble to make accurate measurements. Before you talk about the accuracy of a simulation program, youy have to know the accuracy of the measurements that you are putting into it. You also need to know and address the error introduced by any other assumptions that you are going to make. For example, I can measure wind speed at the launch site to about a 5% accuracy, but I am not sure about wind variability and the accuracy of its measurement.

Bruce S. Levison, NAR #69055

#### illini

##### Well-Known Member
You're right, we haven't specifically discussed those forces, although they were implicit in my statements regarding assumptions that reduce the 6-DOF equations to the "Rocksim equations".

You are also precisely correct in your statements regarding accuracy of inputs. The variability of the environment vs. the variability in the sim is precisely why I say I would never claim that Rocksim could precisely predict the landing point for any given flight. Variability exists in nature and Rocksim models this to some degree. Taking landing point as an example, the best we could hope for from Rocksim is to generate statistics from a large number of runs so that we could predict a mean landing point and a radius defined by standard deviation or CEP (circular error probable). Then fly under identical conditions of environmental variability and compare the distribution of touch down points with the predicted CEP. Unfortunately, Rocksim allows you to examine each simulation independently but provides no mechanism for generating statistics from a collection of simulations. And, the real environment isn't likely to be sufficiently cooperative that you could conduct enough flights to be statistically meaningful before conditions change.

The thing is, the simulation is a model of the environment (duh!). The equations may be precisely correct (or impact of assumptions be minimal) so that precise predictions can be made. But if the environment being modeled has variability (e.g., wind, turbulence, thermals, engines, etc.), then the sim is an accurate model of the environment only if it models such variability and provides tools to assess the impact of such variability via statistics. In my opinion, Rocksim would be a much stronger program if it did more to model variability (in construction, engines, environment, for example) and took more of a statistical approach than the current "independent deterministic simulations" approach.

Just another 2 cents (probably up to around a quarter by now).

#### rocket72175

##### Well-Known Member
Rocksim version 7 includes switches for variable/random weather conditions. I believe the intent is "virtual competition", and not rigorous variablility analysis. SPLASH is geared more to the variability/probability of the flight performance.

For a pc-based design and simulation software, Rocksim offers a lot that appeals to the masses. From casual observation, most users seem more interested in the design features rather than the flight simulation. My guess is that more elaborate simulations are not demanded by hobbyists and not justified in the business model. Surely such enhancements would escalate the price well beyond the $90 that already generates many complaints. #### illini ##### Well-Known Member Originally posted by rocket72175 For a pc-based design and simulation software, Rocksim offers a lot that appeals to the masses. From casual observation, most users seem more interested in the design features rather than the flight simulation. My guess is that more elaborate simulations are not demanded by hobbyists and not justified in the business model. Surely such enhancements would escalate the price well beyond the$90 that already generates many complaints.
Spot on. Exactly my point. Read back through this thread and you'll see that I'm not complaining about Rocksim accuracy. It answers the questions I most want answered. What I have a problem with - and this extends far beyond Rocksim and into my professional life - is claims of accuracy that aren't justified or even necessary. Use it for what it is, warts and all, and you have a fine tool that I think is well worth the \$90. Don't claim it to be what it is not. As I said in a previous post, we couldn't afford the simulation or supercomputer necessary to run it that measures up to what some people think Rocksim is capable of. Rocksim is a fine piece of software, but getting the most out of it requires understanding the underlying assumptions. This is true for all sims I've come across, many of which have high price tags and large development teams.

#### Gus

##### Well-Known Member
While I appreciate all the real science involved in these discussions, let me add a different perspective.

When I was a kid my rocket design process involved scraping together the remnants of my last launch, gluing together the mix-and-match components that produced something that "looked about right" or maybe just "really cool", and then taking it to the pad stuffed with the biggest motor the body tube and my allowance would accept. Launch was always a "duck and cover" event, which was a major part of the fun.

As a (marginally) more responsible adult, I'm just trying to make sure that what I take to the pad won't decapitate my kids. RocSim has been 100% accurate in meeting my goal!

In addition, the program has taught this non-rocket-scientist an awful lot about what makes a rocket fly. The wealth of information about the program and all the free stuff on Apogee's site has taught me an incredible amount, and has made my mostly off-the-shelf kits way better fliers. It's also sparked a real interest in and appreciation for the real-world boosters that put us into space.

If you're coming at this from the perspective of someone who already knows an incredible amount about the science involved and are looking for the "perfect" simulation, then I suppose virtually nothing will absolutely fit the bill.

But if you're coming at it from a perspective like mine (basic knowledge and wanting to learn more) then RocSim is worth way way more than what I paid for it.

RocSim, EMRR, and all of you involved in this forum make this hobby massively better than it was when I was a kid.

#### illini

##### Well-Known Member
Great insights, Gus. Thanks! Another great example of Rocksim answering the questions you want answered. And a great reminder that fundamentally it is all about *learning* something. Rocksim is *very* good for that (as TARC'ers would surely testify).

#### rstaff3

##### Oddroc-eteer
Gus, welcome onboard and thanks for the input. I find it interesting that even though you have a different background than some of the previous posters, you pretty much summed up and confirmed where this thread was going. (my opinion of course)

#### Chilly

##### Well-Known Member
Has anyone used this? I have the demo but some input would be appreciated.

Here's how I see things:
RocSim is way too expensive for my needs. If I were to get into scratchbuilding it'd be more useful.
wRASP is nice but I can't seem to save any data. The results vary wildly from RocSim also - is one more accurate than the other, or do I need to pay more attention to the parameters I've set?

So if RocFlight is a good balance between the two, it'd be a good deal for 25 bucks. Any opinions?

#### teflonrocketry1

##### Well-Known Member
Originally posted by Chilly
Has anyone used this? I have the demo but some input would be appreciated.

Here's how I see things:
RocSim is way too expensive for my needs. If I were to get into scratchbuilding it'd be more useful.
wRASP is nice but I can't seem to save any data. The results vary wildly from RocSim also - is one more accurate than the other, or do I need to pay more attention to the parameters I've set?

So if RocFlight is a good balance between the two, it'd be a good deal for 25 bucks. Any opinions?
If cost is a problem whay not master one of the freewares? As for WRASP pay careful attention to the directory where you save your .rsp files, if you are not careful you will end up having to do a search for them. Just search for files named *.rsp. If you just typed in a file name with no directory extensions your newly created .rsp file the file will be stored in your root (c:\) directory!

There are many other softwares and freewares you can use to simulate rocket stability and flight. Visit Mark Fisher's web site for descriptions, compairisons and links to them at:

http://fly.to/mrhq

He doesn't compair them to RocFlight though. I started out using WRASP (for flight simulations) and VCP (for stability simulations) both are classic programs (freewares) that have a lot to offer.

Bruce S. Levison, NAR #69055