How high did your LOC Warlock go on a big motor?

... and I thought I was nutso thinking I would fly my Warlok on a K550.

What two programs are you using that give you diverging results?

Rocsim & Splash

oops... hit the button too soon...

Rocsim says it goes high but Splash says it hits some invisible barrier after burnout and slows down *fast*...

Do your recall how high the K550 pushed your Warlock?

Andy

That's probably when the fins come off, and the airframe collapses...

tah

Not yet. :-)

I haven't gathered the courage to fly it, Andy. Actually it's not the boost that worries me much, it's looking for it in the nearby forest that gives me pause.

Is that what Tweak reported with his? Surely *he* has insight into this.... :-)

Andy

I don't own a Warlock model, but I've seen them fly and they do slow down quickly. They have lots of base drag and if built stock (i.e. light weight) they don't coast well. This is a good thing if you fly on a small field. The two programs must treat the drag force simulation differently. Maybe Splash uses different CD for power-on and power-off? I don't think RockSim does that.

-Jeff Taylor

What are the specs of the Warlock? I have a homemade rocket sim program I can run your specs through and see if that leans towards one prediction or the other.

One program might be taking into account the fact that Cd and drag equations diverge when you go supersonic. (i.e. stagnation pressures)

Dave

Hello David,

I reckon sorta like what Jeff said, the Warlock is like a Big Daddy on steroids. It's probably unlikely people would fly the Warlock/M1315W combination but it probably would represent "a corner" of the types of HPR flown.

Well, here's the results my program got for the Warlock on an M1315:

Max alt (AGL) 6630 ft / 2028m Max speed 731mph / 327 m/s

What did your other two programs predict?

Dave

Hello Dave,

Been out awhile.

Rocsim comes up with Amax = 3118m Vmax = 417 m/s

What was interesting was the drag coefficients as Jeff suggested. According to rocsim, the base drag is darn near the normal drag coefficients (!!!) and that the overall drag really scootches up there around transonic.

Splash lets you fiddle with both the axial and base drag independantly as a function of velocity. What I'm doing now is running rocsim to get drag parameters, checking for a reasonably close altitude & velocity curves using wRasp, and then hammer around with the drag coefficient gains {leaving the Cd(axial)/Cd(base) ratio alone} with Splash until I get a profile that matches reasonably well before moving on to the monte carlos.

The Warlock is truly an odd duck. On some runs, I can get it to come down faster terminally than I can get it to go up. On other splash runs where I hold everything else constant, I can get the Warlock going higher on a K250 than with an M1315. I've no idea what the folks at LOC had in mind when they came up with that design but I'm now seriously pondering adding one to the fleet after I move out the wife's washing machine.

Thanks for helping me untangle this.

Andy

Hm, I'd be skeptical of your drag coefficient properties. The K250 weighs 2.2kg (1.6kg propellant). The M1315 weighs 5.7kg (3.5kg propellant), but has 2.5 times the impulse and over 3.5 times the average thrust (over the first 3 seconds) that the K250 does. I'm estimating the Warlock to be 144oz (dry, w/o engine case or prop) and a dia of 7.675in. The M1315 should produce a higher altitude and velocity than the K250.

I'm getting a max altitude of 1,477m and a top speed of 151m/s on the K250.

What drag coefficient properties are you using?

Dave

Hey Dave,

You snipped and quoted my message out of context but that's okay...

I used the drag coefficients from rocsim (.11 for base drag and .12 surface both profiled as a function of mach) not necessarily because they are correct but because it's from a method that others should be able to repeat independantly.

Take care, Andy