I've been writing a computer simulation for a small satellite launcher, and have discovered a mistake in my code!
The mistake isn't quite relevant to the question I want to ask, but related.
I've been modelling aerodynamic drag in the lower part of the atmosphere as constant * airdensity * velocity * velocity.
I realise that the constant will vary according to the design (area, shape), but I was wondering whether anyone could point me to, or give me some idea of, the size of the drag forces on something like Scout or Titan II.
Nichola...@aol.com wrote: > I've been writing a computer simulation for a small satellite > launcher, and have discovered a mistake in my code!
> The mistake isn't quite relevant to the question I want to ask, but > related.
> I've been modelling aerodynamic drag in the lower part of the > atmosphere as constant * airdensity * velocity * velocity.
> I realise that the constant will vary according to the design (area, > shape), but I was wondering whether anyone could point me to, or give > me some idea of, the size of the drag forces on something like Scout > or Titan II.
> Many thanks,
> Nicholas Hill
Drag coefficient is a function of Mach number and angle-of-attack, so you would have to have that information in order to obtain anywhere meaningful results.
Use one of the standard atmosphere models to get the density and temperature profiles, since speed of sound is a function of temperature.
> Drag coefficient is a function of Mach number and angle-of-attack, so > you would have to have that information in order to obtain anywhere > meaningful results.
> Use one of the standard atmosphere models to get the density and > temperature profiles, since speed of sound is a function of temperature.
> -- > Remove _'s from email address to talk to me.- Hide quoted text -
> True enough - but do you know of any formulae that give values for > drag co-efficient?
> > Drag coefficient is a function of Mach number and angle-of-attack, so > > you would have to have that information in order to obtain anywhere > > meaningful results.
> > Use one of the standard atmosphere models to get the density and > > temperature profiles, since speed of sound is a function of temperature.
> > -- > > Remove _'s from email address to talk to me.- Hide quoted text -
> > - Show quoted text -
You'd be better off at getting that classified information from North Korea, or perhaps China.
You could use our Saturn 5 formula as a how not to fly-by-rocket, that is unless using them NASA/Apollo (aka DARPA) conditional laws of physics. . - Brad Guth
In article <a47bdf24-6d97-433e-87ff-c9a74de09...@j22g2000hsf.googlegroups.com>,
Nichola...@aol.com wrote: > True enough - but do you know of any formulae that give values for > drag co-efficient?
A CFD program should probably help you get first-second order drag curves.
> > Drag coefficient is a function of Mach number and angle-of-attack, so > > you would have to have that information in order to obtain anywhere > > meaningful results.
> > Use one of the standard atmosphere models to get the density and > > temperature profiles, since speed of sound is a function of temperature.
> > -- > > Remove _'s from email address to talk to me.- Hide quoted text -
Nichola...@aol.com wrote: > True enough - but do you know of any formulae that give values for > drag co-efficient?
>> Drag coefficient is a function of Mach number and angle-of-attack, so >> you would have to have that information in order to obtain anywhere >> meaningful results.
>> Use one of the standard atmosphere models to get the density and >> temperature profiles, since speed of sound is a function of temperature.
>> -- >> Remove _'s from email address to talk to me.- Hide quoted text -
>> - Show quoted text -
There isn't any simple one-size-fits-all formula for the Drag Coefficient. It depends on the vehicle's diameter (frontal area) length, nose shape, tail shape, whether the body has straight or curved sides, whether it's stepped in between stages, whether the rocket motor(s) are burning or not, and the effects of transonic and supersonic flow.
A good place to start would be Ashley and Landahl's "Aerodynamics of Wings and Bodies",
-- Pete Stickney Any plan where you lose you hat is a bad plan
I quite agree - but all I am after really is some order of magnitude figure. Air drag is significant, but might be called a 'second order' effect. To put it another way - I know this is going to vary from vehicle to vehicle as you quite rightly say - but what effect does air resistance have on the size of payload? 1%? 10%? My current program ignores air resistance altogether, and I am just curious as to the size of error this introduces.
> There isn't any simple one-size-fits-all formula for the Drag Coefficient. > It depends on the vehicle's diameter (frontal area) length, nose shape, tail > shape, whether the body has straight or curved sides, whether it's stepped > in between stages, whether the rocket motor(s) are burning or not, and the > effects of transonic and supersonic flow.
> A good place to start would be Ashley and Landahl's "Aerodynamics of Wings > and Bodies",
> -- > Pete Stickney > Any plan where you lose you hat is a bad plan
