MRX-01 Goliath

The Rocketry Forum

Help Support The Rocketry Forum:

This site may earn a commission from merchant affiliate links, including eBay, Amazon, and others.

lancehunter17

Member
Joined
Sep 16, 2012
Messages
11
Reaction score
0
This is my first Tread if I did something wrong Sorry!

MRX-01 Goliath has a 2.6in dia body, it's going to be an Air-start rocket. Two strap-on boosters (D12-0) will lift it and after they fall off a sec later the main engine (E9-6) will fire. Recovery is going to be like Quests Superbird. I'm also going to make the main engine mount removable, so I won't have to run wires from the ignitor to the timer. I first make the rocket in Google Sketchup, then got a 30 day trail of RockSim.

Length: 48.55"
Diameter: 2.6"
Width: 15.88"
Velocity ~97.5 mph
Altitude~818 mph

Rocksim
MRX-01 Goliath 3D.jpg
MRX-01 Goliath.jpg
MRX-01 Goliath 2.jpg

Sketchup
Goliath 5.jpg
Goliath 4.jpg

Fins
Left Wing https://lancehunter17.deviantart.com/gallery/?offset=48#/d4bxa4a
Upper Fins on Body https://lancehunter17.deviantart.com/gallery/?offset=24#/d4llnqd
Nacelle Fin https://lancehunter17.deviantart.com/gallery/?offset=24#/d4lloh6
 
Very cool. How are you planning or releasing the boosters? What are you planning to use for a staging timer and power source?
 
Welcome to TRF. :)
You design looks cool! I'm a little concerned about the (relatively) very low velocity, and it looks like you need a little more nose weight with the 0.98cal marginal stability according to your RS file. Of course, the nose weight will make it go slower, so it'll need to be more stable, and so on and so forth. But, if you're not set on the proportions as they are, just making the main airframe tube a little longer should solve that problem.
I'd say it's definitely a workable design. I'm excited to see what you do with it!
 
Cool design. Will you put simulated nozzles on the exterior pods (the ones without engines)?
No I Don't Plan too.
How are you planning or releasing the boosters? What are you planning to use for a staging timer and power source?
Yes I plan on releasing the boosters with clips Strap on.jpg the size is wrong I'm going to have to up scale it and make the hook out of aluminum. The Staging timer I was going to use a Perfectflite miniTimer3G https://www.perfectflitedirect.com/products/miniTimer3G.html but they aren't making them any more so I am waiting for the replacement to come out.
5/21/2013 UpDate Perfectflite came out with a new Staging timmer the miniTimer4G
You design looks cool! I'm a little concerned about the (relatively) very low velocity, and it looks like you need a little more nose weight with the 0.98cal marginal stability according to your RS file. Of course, the nose weight will make it go slower, so it'll need to be more stable, and so on and so forth. But, if you're not set on the proportions as they are, just making the main airframe tube a little longer should solve that problem.
I'm not really going for height I'm more of a looks guys, and no I'm not set one on the proportions and I can easy make the airframe long i have no problem with that. However my book say a stable rocket is between 1cal-2cal and at .98 that's pretty close and two the Booster come off very quickly and the stability goes to 1.5-1.75cal.
 
Last edited:
True, 0.98cal is very close to 1cal, but moving at less than a hundred MPH the airflow over the fins might not be enough to ensure an entirely stable flight. Even though the booster are not attached for very long, the amount of time that they are attached for is plenty long for the rocket to assume a trajectory in which you do not want your sustainer going after second stage ignition.
Anyway, it sounds like you know pretty well what you're doing, for the most part. Just make that airframe a little longer to get up towards 1.2cal, or better yet a little higher, (since slower moving rockets generally have to be more stable because of the decreased airflow experienced at lower speeds) and you should be good to go. :)
 
True! and thanks for the advice :D, I will make the airframe longer. When day I'll buy Rocksim and then I'll be able to know just how long the airframe need to be.
 
Coming in late to this thread, but...

1. That is REALLY friggin' cool.
2. Don't use D12-0s. Use D12-Ps. The -0s will light the tubes on fire, as they're meant to light an upper stage. The -Ps are plugged so once it burns out, it becomes dead weight.

Best of luck with the build - give us an update when you can!
 
2. Don't use D12-0s. Use D12-Ps. The -0s will light the tubes on fire, as they're meant to light an upper stage. The -Ps are plugged so once it burns out, it becomes dead weight.

Hey Dave thanks for coming :) I can't use -Ps I need the Boosters to fall off and they will only fall off after the nose cone has been ejected. and the rushing air pulls them off.
 
Update: a few months ago I figured to Estes has released E boosters! I'm so excited! Now I'll have less of a worry of lift off. I have also been at Apogge Rocket looking over the PerfectFlite MiniTimer4 Staging Timer and Apogee says to use the First Fire Jr. Igniter however that igniter say is requires 12v to work will Apogee has a 9v hooked up to the time, and I'm afraid the 9v won't be able to ignite it So I'm thinking of puting a second 9v on paralle to double the amps. What are any ones thought? and does anyone have any played around with that Staging timer?
 
I would imagine a Q2G2 or a Q2G2 with "help" would work just fine for airstart of a bp motor, and they have a really low all fire current. I ground tested one with my RRC3 powered by a 9V, the time between current and fire was almost imperceptable and the voltage dipped about 3% for <<1 sec.
 
Agree with a Q2G2. And with BP no "help" should be required. The Q2G2 will work fine with a 9V battery
 
Hey Dave thanks for coming :) I can't use -Ps I need the Boosters to fall off and they will only fall off after the nose cone has been ejected. and the rushing air pulls them off.
You can make them fall off when they burn out, then they can deploy a recovery if you use one. I've built one like that (didn't fly it yet)
https://www.rocketryforum.com/showthread.php?59540-First-cluster-and-first-separatable-boosters
I based on this guy's design, my only modification was a safety thread to hold the booster in place on the ground.
https://www.rocketryforumarchive.com/showthread.php?t=40270
https://www.youtube.com/watch?v=QSVjOT1Y45U
 
I would imagine a Q2G2 or a Q2G2 with "help" would work just fine for airstart of a bp motor, and they have a really low all fire current. I ground tested one with my RRC3 powered by a 9V, the time between current and fire was almost imperceptable and the voltage dipped about 3% for <<1 sec.

I do agree with you however I might once and awhile want to but an composite 24mm in sometimes! :)
 
You can make them fall off when they burn out, then they can deploy a recovery if you use one. I've built one like that (didn't fly it yet)
https://www.rocketryforum.com/showthread.php?59540-First-cluster-and-first-separatable-boosters
I based on this guy's design, my only modification was a safety thread to hold the booster in place on the ground.
https://www.rocketryforumarchive.com/showthread.php?t=40270
https://www.youtube.com/watch?v=QSVjOT1Y45U

I have research the friction fall-away booster and i just like the idea of the boosters being hooked so there is no way it can come off as I carry it to the launch pad. But Thank You for the input! :)
 
Ok I have been doing some revising to Goliath. Now its a 3" DIA rocket. Still an Air-start but with Estes new 29mm Boosters it will Fly faster. Loaded with the largest engines it has a 1.23 CAL and after the booster fall off jumps to 2.42 CALMRX-1 Goliath Revised 2D Base Loaded.jpgMRX-1 Goliath Revised 2D Side Booster Gone.jpgMRX-1 Goliath Revised 2D Side Loaded.jpgMRX-1 Goliath Revised 3D 1.jpgMRX-1 Goliath Revised 3D 2.jpgMRX-01 Goliath Revised 3D 3.pngMRX-01 Goliath Revised 3D 4.pngMRX-01 Goliath Revised 3D 5.pngMRX-01 Goliath Revised 3D 6.png
Not for sure how to upload the Rocksim file hopefully I did it right here-> View attachment MRX-1 Goliath Revised.rkt
 
Airstarts are great fun, but I'd have serious concern about the off-center thrust from your boosters. That thing will, at best, arc over and prang under power. At worst, it will loop until it shreds. Still a cool flight, be sure to video!
 
Old thread, but have you made any more progress?

Looks like you have some time under your belt using SketchUp, I've modeled a couple, but not to the detail you have. Very cool!
 
I personally would make the vertical fins more vertical, even though it is saying 1 caliber of stability, it sure looks like lateral stability in the side view will be marginal especially if you have any non uniform ignition of the offset motors, that's just my mindsim talking....Maybe put a vertical fin on each booster, it won't hurt to have some extra margin.
 
Old thread, but have you made any more progress?

Looks like you have some time under your belt using SketchUp, I've modeled a couple, but not to the detail you have. Very cool!
Sadly no I have not. One my family and raising my three boys (all under the age of 5) takes up most of my time. Second I don't have the space (garage/shop) to start this project. Hopefully one day I build Goliath. And Im no expert at Sketchup but thanks!:)
 
Back
Top