Nose Cone Experiments

[AaronLS]

While drag and lift models, as well as stack drag occlusion, were all mentioned in the release notes, nose cones did not get a mention. Many of them list the same drag rating, and in the past it was stated mass was related to drag.

So I have done some tests with nose cones that I thought I'd shared. I placed 4 basic fins at the bottom of a RT-10 rocket booster, and launched it without a nose cone, let it run out of fuel, and observed what altitude it reached, then did the same with various nose cones.

[TABLE=class: outer_border, width: 600]

[TR]

[TD]Test Case[/TD]

[TD]Max Altitude (m)[/TD]

[/TR]

[TR]

[TD]No cone[/TD]

[TD=align: right]8100m[/TD]

[/TR]

[TR]

[TD]Aerodynamic Nose Cone[/TD]

[TD=align: right]10500m[/TD]

[/TR]

[TR]

[TD]Advanced Nose Cone - Type A[/TD]

[TD=align: right]15000m[/TD]

[/TR]

[TR]

[TD]AE-FF1 Air Stream Protective Shell (tiny shallow fairing)[/TD]

[TD=align: right]9050m[/TD]

[/TR]

[TR]

[TD]AE-FF1 Air Stream Protective Shell (very large fat fairing)[/TD]

[TD=align: right]flipped[/TD]

[/TR]

[TR]

[TD]AE-FF1 Air Stream Protective Shell (sharp fairing, picture below)[/TD]

[TD=align: right]18500m[/TD]

[/TR]

[TR]

[TD]Small Nose Cone (Note: this does not match rocket diameter)[/TD]

[TD=align: right]8850m[/TD]

[/TR]

[TR]

[TD]Tail Connector A (Reversed. We laughed at it, then with stone cold determination, it showed us that it has been waiting its whole life to be a nose cone.)[/TD]

[TD=align: right]24200m[/TD]

[/TR]

[TR]

[TD]Ram Air Intake[/TD]

[TD=align: right]12850m[/TD]

[/TR]

[TR]

[TD]MK1 Cockpit (very heavy, not really a fair test of drag)[/TD]

[TD=align: right]13500m[/TD]

[/TR]

[TR]

[TD]Mk1 Inline Cockpit with Tail Connector A (reversed)[/TD]

[TD=align: right]17750m[/TD]

[/TR]

[TR]

[TD]Ram Air Intake with two side mounted XM-G50 Radial Air Intakes[/TD]

[TD=align: right]7750m[/TD]

[/TR]

[TR]

[TD]Tail Connector A (reversed) with two side mounted XM-G50 Radial Air Intakes[/TD]

[TD=align: right]9350m[/TD]

[/TR]

[TR]

[TD]Mk1 Command Pod[/TD]

[TD=align: right]11550m[/TD]

[/TR]

[TR]

[TD]Mk1 Command Pod with Tail Connector A (reversed, Note: diameter mismatch)[/TD]

[TD=align: right]17800m[/TD]

[/TR]

[TR]

[TD]Mk1 Command Pod with Small Nose Cone (matches diameter, sort of)[/TD]

[TD=align: right]13750m[/TD]

[/TR]

[TR]

[TD]Mk1 Command Pod with Mk16 Parachute[/TD]

[TD=align: right]12400m[/TD]

[/TR]

[/TABLE]

Disclaimer: While a high altitude is clearly better, the numbers aren't proportional. A nose cone that is only slightly better will produce a disproportionately larger number since it was able to get the rocket into thinner air more quickly, and further from Kerbin's gravity.

One thing with the sharp fairing, is it matched to the angle of the drag "wisps" that are deflected at high speeds. So maybe these are more than graphical embellishments, and actually have some indication of the ideal deflection angle of a nose cone.

If I were to do this test a little more scientifically, I'd have found a way to add extra weight when using lighter cones, so that all of the builds weighed exactly the same. I think the weight played a very minor role here though. For example, the best run of the AE-FF1 performed much better than the "tiny shallow fairing" which weighed slightly less. It also performed better than the lighter Advanced Nose Cone.

Then I took a tail connector, reversed it and put it on top to function as a nose cone. I did it only as a silly footnote in the table. I expected the rocket to flip over, but it didn't. Not only that, it performed better than all the other nose cones! I imagine if I made a fairing that matched the tail connector, it'd do almost as well or better.

Note: the rockets are tipped over in pictures because I waited for the ascent meter to 0, their ascent was straight up, but only guided by the fins.

I was also surprised that an air intake performed better than the basic nose cone. I incorrectly assumed they generated lots of drag. The radial intakes do seem to generate considerable drag though, which probably also corresponds to why they overheat and blow up quickly on high speed planes.

The Mk1 Cockpit performed well, and probably was hindered by the fact that it weighs ALOT more than any of the cones tested, but I ran it out of curiosity. For a better comparison, I then ran an inline cockpit with the best performing nose cone, for a better comparison in that weight range. The Mk1 weighs 1.28t. The Mk1 Inline weighs 1.03t and the reversed Tail Connector A weighs .2t, making a very close total of 1.23t. So from that test it seems anytime I want to use a Mk1, I'm probably going to put a giant nose on it and use the inline cockpit

Ever seen that Portlandia skit "put a bird on it"? My new motto is "put a reversed tail connect on it".

I wonder if you can make a protective fairing that "noses" in on the reversed tail connector's performance, and also provides enough of a cylinder at the base to house a probe.

This new info should help me make some serious improvements to my high speed planes. I suspect the best design is inline air intakes with reversed tail connectors as a nose cone.

Edited May 4, 2015 by AaronLS

[Red Iron Crown]

Great testing, thanks for sharing your results. Welcome aboard!

[Xaver]

Thank you. That tail connector

[Khazar]

Nice experiment and surprising results. I rarely use cones at all, because I thought they don't make much difference. Seems I was quite wrong. What was the approximate speeds your vessel reached ?

If I were to do this test a little more scientifically, I'd have found a way to add extra weight when using lighter cones, so that all of the builds weighed exactly the same.

Why not to add fuel tank on top of solid booster ? As there is no liquid fuel engine it wouldn't produce any thrust and you could change mass by setting the amount of fuel.

[Alshain]

If I were to do this test a little more scientifically, I'd have found a way to add extra weight when using lighter cones, so that all of the builds weighed exactly the same.

Look up a mod called NRAP Adjustable Test Weight. You can customize it's mass but I think it's meant to be on the front of the rocket (for testing lifter designs). You might be able to make it really small and then put it in an inter-stage fairing somehow.

[OhioBob]

Nice work, AaronLS.

I started doing some similar tests by computing the drag coefficient from the terminal velocity. I've only tested three shapes so far, here's what I got:

My results are in agreement with yours in that the shapes with the lowest drag coefficients attained the greatest altitude.

Edited May 4, 2015 by OhioBob

[worir4]

Thanks for this! I appreciate it.

[AaronLS]

Nice experiment and surprising results. I rarely use cones at all, because I thought they don't make much difference. Seems I was quite wrong. What was the approximate speeds your vessel reached ?

Why not to add fuel tank on top of solid booster ? As there is no liquid fuel engine it wouldn't produce any thrust and you could change mass by setting the amount of fuel.

I believe it was only the last update that made this change, although they didn't mention it directly.

The reverse tail "cone" runs out of fuel at about 7200m and is going 970 m/s at that moment, producing quite the flare.

The fuel tank idea is good.