19 replies to this topic

[DLuders]

To add to my collection of Flying Lego Rockets, I flew my Lego Technic "Death Star Booster Rocket" on an Estes C6-5 model rocket motor today. It flew to ~300 feet (~90 meters) before the ejection charge popped off the Lego Death Star "11x11 Hemisphere" 98114 + 98115 (from the current Lego 9676 set).      The rocket consists of only 36 Lego pieces (no gluing). Eight 2780 "Technic Pins with Friction" hold the 64782 "Technic Panel Plate" Box Fin assembly together. Using 8 more "Technic Pins with Friction", four 32278 1x15 Technic Liftarms clip onto the gray 32324 "4x4 Technic Brick with Open Center" (placed upside-down to accommodate the black 3709b "2x4 Technic Plate with 3 Holes"). The Death Star hemispheres have studs on the top and bottom to press onto the Technic Plate.

I had to carve the cardboard rocket motor casing with a knife a bit, to enable it to fit inside the "4x4 Technic Brick with Open Center". Remove just enough (about 1/4") on four sides of the top of the motor casing, to make a square-sided shape that is fairly loose. You want the motor's ejection charge to deploy the Death Star (via the holes in the Technic Plate) AND push itself off of the rocket frame at apogee. The motor hangs down; make sure it is aligned well for straight thrust.

The black rocket frame and Death Star both impacted the earth hard     , but everything just pops together for more flights! Nothing was cracked or broken. You can remove the minor black soot on the Death Star and Technic Plate by using White Vinegar.

The rocket can also fly on an 18mm C6-3 motor (with a 3-second delay). Holes in the edge of the 5x11 Technic Panel Plates allow you to place the rocket on a standard 1/8" launch rod (as shown in the picture).

I know that Blakbird is a model rocketeer -- are there any others who have flown rockets AND are Lego fans too?  My SPokane Area Rocket Club (SPARC) NAR Section 626 buddies like to see unusual "Odd Rocs" like this.

@ Alasdair Ryan:  I want you to note that I made my OWN MOC!  

Edited by DLuders, 16 April 2012 - 02:14 PM.

[dr_spock]

Didn't you say you'd make a MOC only after Blackbird makes one?    

Do you have a video?

[DLuders]

@ dr_spock:  I know that Blakbird can make a MOC like this, since I know that he's flown HIGH POWER rockets at Mansfield, Washington.  

No, I don't have a video.  The rocket "wiggled" a bit on liftoff (since the motor was not perfectly vertical in its mount).  I did not dare fly it twice at an officially-sanctioned National Association of Rocketry (NAR) event, since rockets are NOT SUPPOSED TO come back down in a ballistic, "Lawn Dart" fashion!    

When designing flying Lego Rockets, there are these considerations:

a) STABILITY (the "Center of Gravity" must be ~1 body diameter ABOVE the "Center of Pressure" for it to be stable.
b) WEIGHT (the heavier the rocket, the lower/slower it flies).
c) AIR RESISTANCE (the Lego 11x11 Death Star is not very aerodynamic; there is a lot of drag).
d) COMPLEXITY (more parts --> more weight; I wanted it to be SIMPLE so others could build it).
e) MODEL ROCKET MOTOR SIZE (I wanted it to fly on an Estes C6-5 motor, which is a common size).

[timslegos]

Good to see you building something   , i am sure more will follow...

tim

[DLuders]

Another design consideration is the rocket's RECOVERY method:

a)  Most model rockets have either a PARACHUTE or STREAMER to slow the rocket's descent.  Alas, TLG does not make a parachute.  Even the Lego Sails are not large enough to handle a weighty Lego rocket.  I could use a yellow LEGO shopping bag (from an official Lego Store), but I would have to cut the plastic and some "Lego purist" would object.  

b)  A "tumble recovery" is what I intended, but the rocket "came in ballistic" and smashed into the ground at high speed.  So, I had a "bucket recovery" instead (where the pieces are collected in a bucket for reassembly).  

Yes, I intend to build more MOCs, but I have yet to find a Lego AFOL who builds REAL FLYING LEGO ROCKETS like me.  I know Blakbird can do it.... (hint, hint!)  

[dr_spock]

DLuders, on 15 April 2012 - 01:34 AM, said:

@ dr_spock:  I know that Blakbird can make a MOC like this, since I know that he's flown HIGH POWER rockets at Mansfield, Washington.  

No, I don't have a video.  The rocket "wiggled" a bit on liftoff (since the motor was not perfectly vertical in its mount).  I did not dare fly it twice at an officially-sanctioned National Association of Rocketry (NAR) event, since rockets are NOT SUPPOSED TO come back down in a ballistic, "Lawn Dart" fashion!    

I wonder if splitting the death star in half at the apogee could work as a couple of crude parachutes on the decent.  

[Zblj]

Interesting idea! Were the panles burned?

Edited by Zblj, 15 April 2012 - 09:58 AM.

[DLuders]

The bottom 11x11 hemisphere of the Death Star was only slightly melted; the bottom end of the lightweight panels were covered with a light coating of soot (from the Black Powder ejection charge in the Estes rocket motor).  The 2x4 Technic Plate did not melt.  The ejection charge lasts only a fraction of a second, and the melting point of the ABS plastic is around 375 degrees F. (190 degrees C.), per this Eurobricks topic.     Everything cleans up with White Vinegar (which has a mild cleaning action).  I packed a single sheet of Estes flame-resistant wadding into the end of the C6-5 motor (where the ejection charge is) to reduce the scorching.

  

The Death Star    hemispheres clip together with "tabs" that form an interlocking, scalloped shape around the edge.  There is no "halfway point" where the two halves are lightly connected, so that a parachute inside can deploy when the motor's ejection charge goes off.  Here are the 98114 and 98115 parts; the connecting tabs are faintly visible.  The top and bottom holes (in between the 2x2 studs) are only the size of a Technic Pinhole.  I MAY be able to rig up and internal strut (made from a Technic Axle) to hold the hemisphere halves barely apart upon takoff, but easily separable at apogee:



On the next flight, I was going to SHORTEN the long Technic Liftarms (from 1x15 to 1x13), so the "Center of Gravity" is a bit lower.  That way, after the rocket deploys the Death Star at apogee, the rocket body will be less stable upon descent and will "tumble" instead of coming down ballistically.  Here is a pic of the rocket on the ground, before I did my "bucket" recovery.     The 11x11 ball remained intact, but the black rocket body popped apart via the Technic Pins.  Everything just snapped back together -- no broken or bent parts:



Besides the Death Star, one could also launch two other kinds of "planets" -- Tatooine and Naboo (all currently available on Shop.Lego.com):  

     

Edited by DLuders, 16 April 2012 - 02:16 PM.

[RohanBeckett]

Something like this, I'm guessing?



can you trim the tabs a bit, so they don't clip as strongly?


I too used to fly estes rockets when I was younger too... unfortunately, the motors cost quite a bit out here in Australia.. so launches we definitely saved for good weekends!  I do remember chasing a many drifting parachuted rocket over several km's of fields/paddocks!

RB

[DLuders]

@ RohanBeckett:  That's a good solution -- a piston plunger that pops off the top of the Death Star!      The 9676 "TIE Interceptor & Death Star" set comes with this useful 2376 "Black Tile, Round 2 x 2 - Lifting Ring" part:



Now, the challenge is to make a LIGHTWEIGHT piston plunger assembly that extends up into the 11x11 ball.  There is plenty of room for a non-Lego parachute inside the ball....  

[DLuders]

  

I rebuilt my Lego Technic Death Star Booster Rocket's body, to make it lighter.  You can see how I carved off the top of the cardboard motor casing so that it fit into the 4x4 Technic Brick with Open Center.  Instead of 1x15 Technic Liftarms, I used four 2637 1x16 Technic Links.  The thinner profile and lighter weight of the link allowed the rocket to climb to ~400 feet (~120 meters) on an Estes C6-3 motor.  The 3-second delay is more suited to this rocket, and the Death Star ball was deployed at rocket apogee.     You can see how I carved the top of the cardboard Estes rocket motor casing, to enable it to fit inside the 4x4 Technic Brick with Open Center.

Here's a short YouTube video of the launch:

  

The flexible Technic Links absorbed the shock better than the liftarms.  Even though I lowered the rocket's "Center of Gravity" by 3 studs (via a lower attachment point on the Box Fins), the booster still came down in a "ballistic" manner.  I will fly it again using shorter, 6247 1x11 Technic Links.  I want the booster to "tumble" down, so I need to make the rocket "unstable" AFTER it spits its motor at apogee.

Edited by DLuders, 16 April 2012 - 02:22 PM.

[Sariel]

OMG, it's raining Death Stars :) You sir, are crazy in a good way.

[KEvron]

yer gonna put your eye out!

good to see you finally mocing it up a bit.

KEvron

Edited by KEvron, 16 April 2012 - 07:59 AM.

[Alasdair Ryan]

Very nice,there is a lot of grumpling in that video (you are showing your age when to bend over).

[DLuders]

@ Alasdair Ryan:  No, that's my son operating the video camera.  He's a Lego AFOL and rocketeer too.  I'm doing the 5-4-3-2-1 countdown (off camera) and running in a red sweater to see it smash into my garden patch.

[Alasdair Ryan]

Well you can tell your son that he is not ageing well.

[Alasdair Ryan]

BUMP

In this Eurobrick's topic Brickstarrunner made a lego Reliant Robin Rocket based from one of the Top Gear episode's.




Download LDD File

Now david do you happen to have rebuilt your rocket...........If so do you think you could launch the lego Reliant Robin into the air?

[DLuders]

Alasdair Ryan, on 21 April 2012 - 01:40 PM, said:

...do you think you could launch the lego Reliant Robin into the air?

Yes, I could launch it into the air, but it would probably come down as a "Lawn Dart" like the Top Gear rocket did!    



Thanks for sharing Brickstarrunner's LDD file -- I had not seen it before.  If I were to build it in real bricks and attempt to launch it, I was thinking about using two 57792 "Vehicle, Tipper Drum 3 x 6 x 10 Cement Mixer Half with 4 Technic Pin Holes" parts to act as an Estes D "motor mount".  The interior is just about the right diameter for a D12-5 motor.  



The tricky part is that the Reliant "shuttle" and the real Space Shuttle have theirs own thruster rockets, to keep the rocket from tilting in the direction of the extra weight.  Most likely, the Lego rocket would end up being a "Sky Writer":

[DLuders]

Yesterday, I flew my shortened Lego Technic "Death Star Booster" rocket on an Estes C6-5 motor.  I used four 6247 1x11 Technic Links to move the weight downwards.  The total number of Lego parts is now 28.  The YouTube video displays what I wanted it to do -- tumble back to earth softly.  The "Center of Gravity" is now close to the "Center of Pressure":    

  

Edited by DLuders, 22 April 2012 - 09:23 PM.

[dr_spock]

DLuders, on 21 April 2012 - 02:09 PM, said:

Yes, I could launch it into the air, but it would probably come down as a "Lawn Dart" like the Top Gear rocket did!    

The tricky part is that the Reliant "shuttle" and the real Space Shuttle have theirs own thruster rockets, to keep the rocket from tilting in the direction of the extra weight.  Most likely, the Lego rocket would end up being a "Sky Writer":

That brings back memories.  I used to have a space shuttle model rocket.  The rocket engine goes into the fuel tank.  At apogee the shuttle is supposed to detach and glide down.  A parachute would open to bring down the fuel tank and boosters.  I can't remember who made that kit back in the 1980s.