Lakeroadster's Lifting Rocket

[cjvannucci]

It looks cool, but aerodynamically and structurally speaking is a stretch. Good luck on timing the motors. I secretly hope I get to eat my words

 

[Nytrunner]

Fortunately tractor motors are a relatively proven concept for safe flight during boost. As long as the burnout CG is forward enough, it should coast fine too.

What are your structural concerns? Have you seen Lake's fillets?

 

[Crawf56]

Anticipation...…..

 

[lakeroadster]

It looks cool, but aerodynamically and structurally speaking is a stretch. Good luck on timing the motors. I secretly hope I get to eat my words

Thanks for checking out "The Lifting Rocket". As a fellow rocketeer once said "It'll either go or blow, either way it'll be spectacular."

Anticipation...…..

I keep getting distracted by stuff like this....

A computer desk I designed and am building. It fits in the corner of our great room, small enough to not block windows, and designed to not block the hydronic baseboard heat system. Staining and poly are next.

My model rocket hobby endeavors are all about the journey, not the destination

 

[mbeels]

Even more anticipation

 

[lakeroadster]

Forgive me... it has been over 4 months since my last confession.....

I had some time to work on the Lifting Rocket today. I used some 3/16" dia. poplar dowel rods to make the strut rods that attach the fin can section to the canted cluster section.

I used a 1/8" dia. drill bit, then a 13/64" dia. bit and then a chain saw sharpening file to cut the openings into the canted cluster. A machinists file worked well for removing the spar urethane from the balsa ply fins.

The strut rods were still slightly larger than the gap in balsa ply fins so I chucked them into a drill and used sandpaper to remove just enough material so that they were a nice snug fit between the fin plys.

 

[neil_w]

Nice (and nice to see you back at it)

 

[Daddyisabar]

KUTGW!

 

[mbeels]

Alright, good to see updates again, it's really coming together at this point.

 

[BABAR]

It almost is starting to look like a rocket!

 

[neil_w]

I think that when this is all finished it’ll still almost be starting to look like a rocket.

 

[Rktman]

Superb! Such beautiful precision.

 

[lakeroadster]

Now that The Lifting Rocket is nearing completion I've been able to get some "As Built" weights. I've modified the Open Rocket designs to account for the heavy glue fillets I used. Final weight appears to be about 1.25 lbs without motors or parachutes.

It appears the Cargo Bay (which weighs 6.2 ounces) at the back of the rocket is a huge air brake. The Cargo Bay is removable and when it's not used during flights the apogee is 1,151 feet.

With the Cargo Bay, Apogee is 798 feet.

Both simulations assume (3) clustered D-12's, and a single D12 at the base of the rocket.

I mean, sure I expected it would effect the apogee some, but that is pretty dramatic.

Is the drastic change due to the aero drag of the larger diameter Cargo Bay transition?

I'm trying to determine what configuration I want for the initial launch. I'd like to have it fully assembled with the Cargo Bay. That way if things go horribly wrong at least all the flight hardware will have made the maiden voyage.

Then again I could load in (4) E motors and let the big hog root. That's a 2,266 ft apogee without the cargo bay... and 1,771 ft with the cargo bay.

Your thoughts on this would be sincerely appreciated.

 

[Nytrunner]

The extra 3/8 lb is non negligible with the aft pod and assorted hardware. And if the flow manages to reattach after the payload bay and canted motor mounts, the pod makes it separate again adding to drag effect.

You've got plenty of thrust to get it off the ground, but i wouldnt be surprised if your actual altitudes are lower due to all the fiddly bits that just cant be accounted for in OR

 

[neil_w]

It appears the Cargo Bay (which weighs 6.2 ounces) at the back of the rocket is a huge air brake. The Cargo Bay is removable and when it's not used during flights the apogee is 1,151 feet.
...
Is the drastic change due to the aero drag of the larger diameter Cargo Bay transition?

As Nytrunner said, 6.2 oz is a significant fraction of a 1.2 lb rocket.

Ways to explore the data:
1) Remove the cargo bay and put 6.2oz of additional weight in the nose. Check sim altitude.
2) Put cargo bay back but override all its components to zero mass. Check sim altitude.
3) Restore cargo bay component masses and change its diameter to match main airframe. Check sim altitude.

All this should give you an idea of the relative contributions of the different characteristics of the cargo bay on projected altitude.

[edit: probably easier to do those in the reverse order I listed them ]

 

[lakeroadster]

As Nytrunner said, 6.2 oz is a significant fraction of a 1.2 lb rocket.

Ways to explore the data:
1) Remove the cargo bay and put 6.2 oz of additional weight in the nose. Check sim altitude................................. Apogee 843 ft ..... vs 798 ft = 45 ft higher
2) Put cargo bay back but override all its components to zero mass. Check sim altitude......................................... Apogee 938 ft ..... vs 798 ft = 140 ft higher
3) Restore cargo bay component masses and change its diameter to match main airframe. Check sim altitude.... Apogee 827 ft .... vs 798 ft = 29 ft higher


All this should give you an idea of the relative contributions of the different characteristics of the cargo bay on projected altitude.

[edit: probably easier to do those in the reverse order I listed them ]

 

[jqavins]

My thoughts on run in a different track. The altitude with 4 x D12 is nothing to be ashamed of. As long as you've got sufficient rod exit speed, launch that puppy.

 

[lakeroadster]

My thoughts on run in a different track. The altitude with 4 x D12 is nothing to be ashamed of. As long as you've got sufficient rod exit speed, launch that puppy.

53 ft/sec.... per Open Rocket.

 

[neil_w]

1) Remove the cargo bay and put 6.2 oz of additional weight in the nose. Check sim altitude................................. Apogee 843 ft ..... vs 798 ft = 45 ft higher
2) Put cargo bay back but override all its components to zero mass. Check sim altitude......................................... Apogee 938 ft ..... vs 798 ft = 140 ft higher
3) Restore cargo bay component masses and change its diameter to match main airframe. Check sim altitude.... Apogee 827 ft .... vs 798 ft = 29 ft higher

OK, so most of the difference is the weight, a some is drag. Only a small amount is drag due to the enlarged body of the cargo pod. Not too surprising.

 

[Daddyisabar]

Trust in thrust. Canted motors lose efficiency the greater the degree of cant. So like Spock to Kirk in the Wrath of Kahn: E's can seem like D's. We are going to launch on 3 D's.

Wink wink nudge nudge say no more!

The canted tractor motors will forgive the sin you have in tow.

Blessed are the tractors!

Thus endith the lesson.

 

[lakeroadster]

Blessed are the tractors!

Thus endith the lesson.

Grasshopper thanks the Master.

 

[kuririn]

Did you ever decide on a name for the rocket, other than the lifting rocket?
Star Hauler X-3?
The Tractor Extractor?
LR Inc. Load Master?
Vulcans never joke.

 

[dhbarr]

Safety Tractor
Iapetus x Clymene
Paul Anderson 1957
Traisun

 

[BABAR]

Three’s Company, Four’s a Cloud

 

[neil_w]

Personally I kind of dig “Lakeroadster’s Lifting Rocket”.

 

[lakeroadster]

It's all good... I mean, after all, what's in a name?

TLR is how I have the files labeled ... as in "The Lifting Rocket"

 

[Daddyisabar]

Grasshopper thanks the Master.

View attachment 400800

Great to see the Aliens using a 4020 John Deere row crop with ROPs! Nothing runs like a Deere!

Aliens know tractors rule.

 

[lakeroadster]

Great to see the Aliens using a 4020 John Deere row crop with ROPs! Nothing runs like a Deere!

Aliens know tractors rule.

Go "Green" or go home...

We've got a 265 that went from mowing 5 acres every 3 days for 10 years... to light "Mule" duty since we've moved.

 

[lakeroadster]

Cut, bent and Installed the cargo bay strut rods & clevises.... then did a little photo shoot.

I still need to paint the hammered copper finish on the body tubes... which should break up all the white.

Also still need to build the launch support assembly to hopefully prevent motor igniter leads from getting tangled during launch.

It's all about the journey... not so much the destination.

But all in all... it's looking pretty true to the CAD Model.


Launch Support

 

[jqavins]

Trust in thrust. Canted motors lose efficiency the greater the degree of cant. So like Spock to Kirk in the Wrath of Kahn: E's can seem like D's. We are going to launch on 3 D's.

But remember also that the loss of thrust (and thus impulse) is merely according to the cosine of the cant angle. These look like - what? about 10°. That would mean only about 1.5% loss. At 20° you lose 6%. So it would take a tiny baby E to look like a D. (An Estes E12 would have to be canted about 43° to look like a D.)