R2K

I wonder how much it erodes? Would it be more tolerant of erosion than a typical nozzle? I mean it is thicker...

Also... what about landings? I would be afraid of it breaking or burning a hole in something

edwardw

After 3 firings, and cleaning the buildup from it I could see only a tiny bit of erosion on the lip of the spike. The pintle didn't have any. When measured it was about .002".

As for landings, I'm just doing the up part. The flyer is responsible for the down part If you break it I guess you'll just have to buy another

Edward

UncleVanya

Finally! I've been looking for a rocket where the fins need to be swept back to protect the nozzle - things are finally right in the world.

Just Jerry

If you don't use the fins to protect the nozzle, one can put a rod out the back (well attached) with a very blunt end for landing drag addition. It pokes into the ground and reduces forces on other rearward projecting parts.

I urged that on the huge Mars Lander rocket.

Just Jerry

UncleVanya

What a great idea. What do you suggest to use on smaller MPR and HPR rockets? Have you seen a wooden dowel work? I'd assume that it would be lighter than a threaded rod. It would probably need to be setup for replacement in the event of a hard landing.

MACH5

When O When will we see the hybrid motors for sale and all certified/ready to go ??

Can't wait to be the first guy on the block with a Alpha Hybrids Rocet Motor !!


Darin

4spacecowboy

congrats on the aerospike and flight:O) here was ours in 2006, no flight yet.

http://en.wikipedia.org/wi...e_2006_mach_daimonds.jpg

Anthony Cesaroni

True "aerospikes" do not produce mach diamonds as they are optimally expanded.

Anthony J. Cesaroni
President/CEO
Cesaroni Technology/Cesaroni Aerospace
http://www.cesaronitech.com/
(941) 360-3100 x101 Sarasota
(905) 887-2370 x222 Toronto

4spacecowboy

then... you might want to tell rocketdyne, EaC, and a few others that they shouldnt have claimed that their engines/motors were not true aerospikes (look at their pics):

http://en.wikipedia.org/wiki/Aerospike_engine

also, the pic i posted was just a split second pic of the motor building up to full thrust which does not have mach daimonds during full thrust as the chamber pressure had reached its designed pressure. i had done an AIAA paper on aerospikes and aware of an aerospikes true optimization. since 2006, i have become a professional rocket propulsion engineer myself and continuing work on outside of the company on hybrid and bipropellant aerospike applications.

4spacecowboy

on another note, i admire cesaroni's work with aerospikes and look forward to seeing more public work in the future.

4spacecowboy

here is an additional pic of the same firing at design conditions:

http://en.wikipedia.org/wi...une_2006_full_thrust.jpg

Anthony Cesaroni

No idea what EAC or Rocketdyne were up to in design terms or the final results. There really shouldn’t be any mach diamonds regardless of the Pc profile AFAIK.

30 milliseconds after voltage detect.



100 milliseconds and full Pc.



Range.



CFD at M 1.95.




Anthony J. Cesaroni
President/CEO
Cesaroni Technology/Cesaroni Aerospace
http://www.cesaronitech.com/
(941) 360-3100 x101 Sarasota
(905) 887-2370 x222 Toronto

Steve_Shannon

4spacecowboy,
Congratulations on getting an aerospike design to work. Looking at other aerospike designs, the aft end of the spike asymptotically converge the axis of the spike. The one you used is almost convex in this area (see below). Could that be the reason for the mach diamonds? Are you expelling pressure through the core of the spike?

4spacecowboy

actually, at the time of the spike, i chose a conical spike (45/15deg) for ease of machining. there was no truncation or base bleed.

regarding mach daimonds, the nozzle was based off the same throat area and half angle for sea level conditions provided with the de laval conical nozzle from west coast hybrids.

Regarding Mr. Cesaroni's response, the CFD that i had resulted from the ideal aerospike, but same conditions were:



the only difference between the ideal nozzle was that the one fabricated was purely conical and not an ideal isentropic curve. Past research has shown that with half angles up to 30 deg only, show about 1% loss in performance regarding ideal vs conical.

after going through each image from the footage, this was the only pic with mach diamonds and the rest of the images showed the following pic from the link provided in the previous post.

the thing about flow separation from a nozzle wall is dependent on the pressure difference from the current atmospheric conditions and the pressure of the gas being expelled.

the fact that exhaust pressure starts at 0 before arriving at design conditions, there can be a difference (over/underexpansion and other variables). also, at some point in the time line of the hybrid motor in operation, the exhaust pressure does change depending on the motor design variables (type, propellants, nozzle design, etc.)

According to theory, an aerospike is slightly less efficient than a bell designed for any given fixed altitude, yet it outperforms that same bell at almost all other altitudes.

There are many points to address regarding the theoretical and true behavior of ideal aerospikes, truncation, base bleed, (shape of spike), and etc. Maybe instead of saying its not a:

'true' aerospike, but more the fact that it was not an

'ideal' contoured aerospike which is true.

i accepted the 1% loss due to the contour shape in the case of my machining experience, availability of a CNC, turnaround times for the independent study, and costs effectiveness since it was out pocket at the time.

an ideal isentropic plug nozzle was preferred, but never the less, it was a working aerospike. since a few years ago, further work has been done to improve those losses in performance. with new capabilities, an 'ideal' truncated aerospike with base bleed are undergoing difference nozzle variations.

4spacecowboy

for clarification on the forum, the pictured graphite aerospike with partial truncation of the tip is not the aerospike i designed. our aerospike was a stainless steel full length conical spike plug nozzle.

Mike Fisher

I've never seen mach diamonds in any of my aerospike tests or flights. Mach diamonds indicate a loss of efficiency or non-optimum design. The video of the eac aerospike is of a non optimized design. Derek Deville agrees with that assessment and I believe that they do now have the bugs worked out.

aerostadt

I suspect that a high performance aerospike nozzle will be designed using the method of characteristics similar to a bell-shaped nozzle. The idea is that compression waves and expansion waves tend to coincide and cancel each other out. Thus, there is turning with no oblique shocks (and consequentially no shock diamonds. Even though oblique shocks are weak and the loss of total pressure is low, no oblique shocks represents ideal performance.) One might think of an aerospike nozzle as the outside of a bell-shaped nozzle wrapped around an axis. The resulting aerospike contour has a surface concave toward the axis.

Bob

4spacecowboy

I agree with with Mike and Aerostadt, but as i said before that the diamonds only showed within less of a second of ignition. After that, the motor was running at full design conditions for that motor.

Also stated earlier, that design of the nozzle at the time was a conical nozzle due to costs and availability of machinery and had agreed and known it was not an 'ideal' aerospike nozzle, but still was an 'true' aerospike nozzle never the less. All other video stills from the same test showed no signs of mach diamonds at that test.

Chamber and exit pressure do change briefly in the ignition sequence which could have contributed to that image shown. It was also stated in the paper that ideal performance losses were predicted for this nozzle at the time of the study.

My conversation was just the intent to state that yes it was a working aerospike nozzle, but not the most efficient or optimal one. It was the very first aerospike nozzle we had designed and tested in 2006 to show a compatibility design for a hybrid propulsion system. Since then, 'ideal' aerospike nozzle designs have been implemented and should be able to show results by summer 2009.