Sorting Ullage Rockets and Retro Rockets

Which craft do I model: Apollo 8, 9, 11, 13, or 15? Not so trivial a decision, if I really want to have a reasonably accurate model.

The S-IC stages had retro rockets. All of these missions used 8, except for Apollo 15, which used only 4.

Some of the S-II stages used ullage rockets: 4 on all of these except 15, none on 15.

If I model Apollo 15, how much will I need to muck with the wraps ("2nd Stage Aft Skirt and Interstage" wrap for the ullage rockets, "Thrust Structure" wrap for the retros)? Can I even make these mods, or is it 4 ullage rockets and 8 retros, period?

4TNC Flight Report

4TNC turned out pretty well!

A B4-2 had the right delay, but not quite enough thrust. The flight seemed to be, well, mushing (in the sense that an airplane can be mushing: descending on the back side of the power curve, not stalled, but not exactly flying well) for about 10m after clearing the launch rod.

A C6-5 produced a nice flight: good altitude, good speed off the launch rod.

A note on flying at Moffett: build those fins strong: that concrete's pretty hard!

4TNC

What do you do when you want to build a rocket quickly, for a tight launch deadline, and you don't have any kits available that fit the bill, and you want something just a little different?

How about a variant on the standby 3FNC and 4FNC designs: 4TNC, using tubes instead of fins? Yup, 4 Tubes and a Nose Cone. We'll see how she flies: RockSim predicts around 50m on a B4, 120m on a C6.

Out of Planned Hold

Out of the planned hold, for about a week now. Minor diversion to get a new rocket designed and built in time for this Saturday's LUNAR launch at Moffett Federal Airfield.

Despite the diversion, work continues on the Saturn V. The primary structure of the lower section of the rocket is completed. Along the way, I learned a nice technique for making tube couplers for arbitrary tubes (assuming you have enough extra from a spare tube): section a piece of the tube so it just fits inside "itself," retaining the tab that's extra, and use the tab as the bonding surface for the two pieces.

Filleting the forward centering ring of the motor mount proved a challenge: it's very far down in the body tube, and tough to reach. There's likely more glue on it than really needed, but I'd rather lost 10' of flight altitude and keep the rocket together.

Planned Hold

T minus who-knows-how-much and holding. We're in a planned hold, a construction hiatus due to other planned activities.

The shock cord is on the motor mount, though, and the aft motor mount centering ring is ready for installation. The after motor retainer has arrived (addition to kit); I'll install that as I install the after centering ring.