Search found 12 matches

by dgsharp
Sat Mar 29, 2008 2:35 pm
Forum: Ramjet forum
Topic: ramjet vehicle performance estimation tool
Replies: 17
Views: 12758

Unfortunately I haven't been able to touch any of my code in a while. Your project sounds cool, very similar to what I had planned as soon as I had some hobby money again (bloody bills!!!), not to mention free time (heh). Anyway. I have 2 separate tools, a spreadsheet ("ramjet calcs") and a Java pro...
by dgsharp
Thu Jan 10, 2008 11:58 pm
Forum: Rocket forum
Topic: Nozzle Geometry
Replies: 5
Views: 3422

Re: nozzle

Keep going, it looks like you're doing good work! One nice thing is that the nozzle geometry really isn't going to kill you if you don't get it perfectly optimized though. You can usually get away with cutting almost any sort of nozzle (like using a stepped bit, a chamfering tool, or even just drill...
by dgsharp
Thu Jan 10, 2008 11:19 pm
Forum: Ramjet forum
Topic: ramjet vehicle performance estimation tool
Replies: 17
Views: 12758

Re: drag

Hey Aaron, thanks for the note. I actually didn't know the ARTS2 came with that software. That's very cool -- frankly if I had known that I probably wouldn't have bothered with writing my own software. Granted, it's nice to have the code so I can make it do anything I want (and it's been a good lear...
by dgsharp
Sat Dec 29, 2007 4:41 am
Forum: Ramjet forum
Topic: ramjet vehicle performance estimation tool
Replies: 17
Views: 12758

Re: drag

Hi WebPilot, thanks for the comments! Let's see..... >Each model was tested at three airspeeds: 80, 100, and 120 km/hr. > >Now I ask you, Dave, what are the Mach numbers for these speeds? I ran my program against that same data set and checked the Mach numbers against the calculator from NASA's webs...
by dgsharp
Fri Dec 28, 2007 2:32 am
Forum: Ramjet forum
Topic: ramjet vehicle performance estimation tool
Replies: 17
Views: 12758

Re: drag

Ok, my program now calculates Reynolds numbers vs time for input flight data. For the characteristic length I went ahead and used the frontal area as suggested by the link below, but let me know if you have any better ideas for that (another one of the links further down in this post seems to sugges...
by dgsharp
Thu Dec 27, 2007 3:37 am
Forum: Ramjet forum
Topic: ramjet vehicle performance estimation tool
Replies: 17
Views: 12758

Re: determining drag model, HELP!!

Hi WebPilot, thanks for the reply! Having a merry Christmas here too. (Oh man, free time... Gotta love it.) > 1. the equation > >FD = CD × ½ × rho × V² × A > >is fine for incompressible flow over a body - e.g. water. > >Remember though, > >CD = f(Re) > >or the drag coefficient is not a constant, it ...
by dgsharp
Wed Dec 26, 2007 7:42 pm
Forum: Ramjet forum
Topic: ramjet vehicle performance estimation tool
Replies: 17
Views: 12758

Re: determining drag model, HELP!!

Merry Christmas! Please excuse my usual long-windedness: So I have been spending a bit of time putting together a program for using empirical altimeter data to determine the Cd vs Mach number of a vehicle. I've got a really good start but I'm hitting some glitches and hoped somebody could help me tr...
by dgsharp
Wed Dec 05, 2007 3:47 am
Forum: Ramjet forum
Topic: ramjet vehicle performance estimation tool
Replies: 17
Views: 12758

determining drag model -- feedback requested

Ok, here's what I'm thinking right now as a way to determine a drag force model empirically. Any suggestions are appreciated! I (or somebody else) put together a tool that reads in rocket motor thrust curves (such as from thrustcurve.org) along with flight data in the form of altitude (or accelerati...
by dgsharp
Fri Nov 30, 2007 11:29 pm
Forum: Ramjet forum
Topic: ramjet vehicle performance estimation tool
Replies: 17
Views: 12758

ramjet vehicle performance estimation tool

I am developing a simple but hopefully useful Excel spreadsheet to help me in my attempt to build a self-sustaining ramjet. (It will be boosted up to speed by a rocket, so it will be launched vertically.) I'm no expert at any of this, but I'm doing the best I can with what I know. Right now it basic...
by dgsharp
Fri Nov 30, 2007 10:44 pm
Forum: Ramjet forum
Topic: how to use RJSC?
Replies: 4
Views: 3707

Re: how to use RJSC

I emailed Glenn and asked him the same question, and hopefully he won't mind that I am re-posting the relevant parts of his reply. This seems like a good start. If anyone has anything to add to it that would be much appreciated. I'll list out the remaining parameters that I don't think are explained...
by dgsharp
Wed Nov 28, 2007 1:09 pm
Forum: Ramjet forum
Topic: how to use RJSC?
Replies: 4
Views: 3707

how to use RJSC?

Hi guys, newbie Dave here, I just introduced myself over in the introductions sticky about how to improve the website. I've downloaded RJSC from Glenn Olson's website, and it seems really cool. The only problem is that I can't find any sort of documentation about it, so I don't know how to determine...
by dgsharp
Wed Nov 28, 2007 1:00 pm
Forum: How to improve this site
Topic: New Members
Replies: 49
Views: 28482

Re: new members

This is my first post, so hopefully I don't goof it up too bad. ;) Ok, my name is Dave, I've been lurking for maybe a week or so and have read many of the old posts. I live in New Jersey at present, though I grew up in the Middle East and went to school in Indiana. I work for a major defense contrac...