Project Vessel Parameters MFD

[Nemoricus]

Oh, they write the expected parameters just fine. It's just that they don't read them correctly.

EDIT: OH! Doh! I didn't check for the end of the MFD block, so the read code was falling through to the second one. No wonder I was getting weird results. I'll have to see if checking for the end of the MFD block fixes the problem.

EDIT2: And it does! Thank you tblaxland. I'm very grateful for all of the help that you've given me so far. I don't think that I would have made it to this point without your advice and the State Vector MFD's source code.

 

[Nemoricus]

Vessel Parameters MFD is just about ready for a release.

The current version is available here, for anyone who wants to test it.

If no major problems are found, I plan to release the MFD this Tuesday.

 

[Nemoricus]

Given that no one has downloaded the latest version or said anything about it, and in the absence of any bugs that I have found myself, I'm going to go ahead and release Vessel Parameters MFD tomorrow.

 

[tblaxland]

I've only had the briefest of looks, but here are some comments:

On the subject of your zip package:

1. Remove the top level directory so the Modules, OrbiterSDK, etc, directories are at the top level. This makes it easier for users to extract the addon straight into their Orbiter directory.

2. Put the readme into a directory called "Doc". This stops users Orbiter root directory from becoming cluttered.

3. Your code files appear in the OrbiterSDK directory, I think you intended to put them in OrbiterSDK\Samples\Vessel Paramters MFD (also note typo).

4. You have no copyright notice. Your call, but I find it best to put something in there to remove ambiguity with regards to your intentions, one way or the other.

On the MFD itself:

5. Something other than IS prefix notation would be nice in addition to the current scientific notation (no big deal though).

6. BurnTimeCalc and your MFD show different delta-V (tested with stock Deltaglider with 45.7% main fuel, the difference was about 1100 m/s).

Good work mate

 

[Nemoricus]

1. That was due to the compression software. I might be able to fix that.

2. Better yet, I'll put it in a Vessel Parameters MFD subfolder under a Doc folder. I like it when add-ons have the courtesy to keep all of their documentation in one easy to find place.

3. Oops. That's a mistake. Fixed.

4. I meant to ask about that, but it slipped my mind. What sort of thing would be good for this? Personally, I don't care if people decide to use my material, just as long as they credit me for making it in the first place.

5. That shouldn't take too long to code. I may want to change total thrust so that it outputs in Newtons, not kilonewtons, just to simplify things.

6. There's no good way to calculate that number. It depends on too many things. I just take the total mass of propellant currently in the tank, the current mass of the vessel, the current mass of the vessel minus the mass of the propellant in the tank, and the highest ISP from the thrusters connected to the tank. From there, it's just Tsiolkovsky's equation.

If you can think of a better way to do this, I'd love to hear it. By the way, which one gives the higher estimate?

 

[tblaxland]

1. That was due to the compression software. I might be able to fix that.

I recommend 7zip.

I use the 7zip command line interface and batch file to automatically package up the addon. I only started doing this recently but it works pretty well. You can see it in Sextant MFD on BitBucket.

2. Better yet, I'll put it in a Vessel Parameters MFD subfolder under a Doc folder. I like it when add-ons have the courtesy to keep all of their documentation in one easy to find place.

I agree.

4. I meant to ask about that, but it slipped my mind. What sort of thing would be good for this? Personally, I don't care if people decide to use my material, just as long as they credit me for making it in the first place.

I've been using the LGPL lately. To be honest, I could insist that you release this under LGPL too (since it is based on StateVectorMFD) but I won't.

NASSP is licensed under GPL, but I don't consider that it is suitable for an addon to a non-open source project (ie, the Orbiter core).

5. That shouldn't take too long to code. I may want to change total thrust so that it outputs in Newtons, not kilonewtons, just to simplify things.

There is a function in State Vector MFD for that purpose.

If you can think of a better way to do this, I'd love to hear it. By the way, which one gives the higher estimate?

No better way from me. BurnTimeCalc is higher.

 

[Nemoricus]

Since this is all freeware (gratis, that is), I see very little point in quibbling over licenses. It's not like there's any money in this. I'm just doing this to provide something useful and to sharpen my own skills while I'm at it. For the same reason, I want this to be open source so that somebody can take it and learn something from it. If that means improving upon my work, that's absolutely fine by me.

I'll have to look into the LGPL, but I'll probably end up using it. If I find any problems with it, I'll let you know privately so that we can work something out. The fact that you won't insist on my using it doesn't mean that I should just blatantly ignore the fact that State Vector MFD is licensed under it. I doubt that any problem will come up, though.

Does the total delta-v from all of the Delta Glider's tanks come out to something like BurnTimeCalc's numbers?

 

[tblaxland]

Does the total delta-v from all of the Delta Glider's tanks come out to something like BurnTimeCalc's numbers?

No, still less. With both tanks full:

[FONT=Courier New]Vessel Parameters MFD
[/FONT][FONT=Courier New]Tank 1: 29910 m/s
Tank 2:   992 m/s
        -----
Total:  30902 m/s

BurnTimeCalc MFD 1.42a
Total:  32031 m/s[/FONT]

EDIT: I should add that adjusting the Tank 2 quantities in the Scenario Editor effects the BurnTimeCalc total value so it is taking both tanks into account.

 

[Nemoricus]

Hmm....I wonder if BurnTimeCalc's value is taken by using the mass of all of the propellant in the vessel and the ISP of the main engine. Does that work out to about the right number?

If so, the discrepancy is probably due to my assumption that only the propellant resource being looked it is used to depletion.

 

[tblaxland]

Hmm....I wonder if BurnTimeCalc's value is taken by using the mass of all of the propellant in the vessel and the ISP of the main engine. Does that work out to about the right number?

Yes.

If so, the discrepancy is probably due to my assumption that only the propellant resource being looked it is used to depletion.

Yes, that explains the difference. For example, using 600 kg of RCS fuel when the main tanks are empty (BTC's assumption) will yield more dV than when the main tanks are not empty (your assumption). I don't see that any change is needed.

 

[Nemoricus]

Ah, good. Both MFDs use valid but different assumptions. I needed to put delta-v in somewhere and the Tanks display mode looked like the best place to put it, hence my using only that tank to depletion assumption. It works out correctly, though, which is the important detail.

My quest to add SI notation to my MFD is going smoothly. There were two amusing moments in this.

The first was when I realised that metric tons and megagrams are the same magnitude.

The second was when I had my mass being displayed, with complete validity, in grams while in exponent mode. It was the right number, but not what I wanted. It needed to be in kilograms. That's been fixed.

---------- Post added 08-11-2009 at 12:30 AM ---------- Previous post was 08-10-2009 at 11:54 PM ----------

Okay, I just finished adding SI notation to my add-on.

RC 3 is here. I haven't updated the documentation, but the only thing I added was a button to switch between exponential and SI notation. Should be self-explanatory.

I need to sleep, so if nothing crops up between now and when I wake up, it will be released as 1.0. I'll just need to toss in the license and update the documentation and it's good to go.

Again, many thanks, tblaxland.