Up End Aerospikes?

[Sparkyflyer14]

Really not sure where to post this...

Found this video about aerospikes. Would this idea of an aerospike be feasible on model rockets? It seems like a novel idea if it is cutting drag by 50%. Or would this only apply to supersonic vehicles? What are your thoughts. I couldn't find any other threads since all that would come up were flamy end aerospikes.

Thanks ahead of time!

 

[aerostadt]

Off the top of my head I would say it is chiefly intended for helping in supersonic flow. A blunt nose cone as shown in the first post will have a detached shock ahead of the main body without the spike. This is a bad situation because the detached shock will look something like a normal shock ahead of the nose cone. Such shock is a strong shock with a large large static pressure rise just behind the shock and a large loss in stagnation pressure (which causes a poor recovery pressure on the aft end of the missile). The spike is to promote an attached oblique shock at the tip of the spike. An Oblique shock can be a weak shock with less static pressure rise and less loss in stagnation or total pressure.

 

[Hobie1dog]

not usable for us

 

[Tim51]

IIRC G.Harry Stine specifically counsels against any spikes or needle noses on model rockets for safety reasons. As Scott Manley explains, the practical application of the spike arose specifically in relation to the need to fit a taller, wider, blunter nosed SLBM (Trident) into launch tubes the same length as those purposed for Polaris/Poseidon - in other words, where an aerodynamically optimised NC shape (a Haack or whatever) was impossible. For a supersonic HPR, any putative need for such a spike would be better served by simply using an optimised shaped NC instead.

 

[GrouchoDuke]

Sears-Haack/VK/C=0 nosecone & be done with it. Unless it's for fun or research, then have at it!

 

[OverTheTop]

A forward aerospike was a feature on some Copenhagen Suborbital vehicles.
https://en.m.wikipedia.org/wiki/Copenhagen_Suborbitals

 

[3stoogesrocketry]

Depending on your vehicle , shorter rounder nose cones sometimes work better then longer ones. Back 15 years ago when bowling ball lifting was still a event , I did alot of aero-research on bowling balls. The main design Geoff Elder and myself came up with was the "ball on a stick" design . Looking back to nature , think of a falling rain drop . Blunt round front with a skinny longer tail . Now this theory stops working at a certain speed as others have mentioned , but anything under about mach .85 and your good. Granted 8 pound balls on a I motor to 2000 feet is alot different then a LPR , but they principal is the same .

 

[aerostadt]

Both the Mercury Redstone and the Atlas Redstone had an aerospike on top of the escape tower. The idea of a an aerospike on top of a rocket has long ago fallen by the wayside.

 

[StreuB1]

The TLDR on Scott's video is simply put....

"How to make a blunt body perform not as a blunt body"

As previously stated, there is no practical application in our world of rocketry.

Outside of merely theoretical, these things don't scale very well below a certain threshold unless you are developing some extreme velocities. Where the extreme velocities can then exploit the benefits of a forward leading spike causing a flow "shadow" for the trailing blunt body.

What I mentioned above is exactly what these things are doing. They are creating a flow shadow for the blunt body to exist within. Easiest way to think about it. The smaller the blunt body, the smaller the shadow, the harder it is for the leading geometry to create the initial shock which when causes the resultant shadowing affect. Atmospheric density would need to increase or velocity would need to increase dramatically to offset the small scale of the article in question.

 

[StreuB1]

BTW, I miss bowling ball lofts!!!!

 

[StreuB1]

BTW2

There is a corollary to this which helps to envision how base drag works and why short fat rockets perform far better on fast hot motors compared to slower burning motors.

Why does a Minie Magg rock on an H550 but is pathetic on an H180? Instantaneous velocity. You are creating a flow shadow (the rocket) very rapidly which helps create a rapidly increasing low pressure zone in the flow shadow region (the area behind the rocket) which helps stability as it pulls the CP backwards rather dramatically.

 

[StreuB1]

Both the Mercury Redstone and the Atlas Redstone had an aerospike on top of the escape tower. The idea of a an aerospike on top of a rocket has long ago fallen by the wayside.

Indeed!!! They were to negate the impossibly complex flow instabilities caused by the traction motors support tower. The spike effectively shadowed the entire tower and motor.

 

[SolarYellow]

Blunt round front with a skinny longer tail . Now this theory stops working at a certain speed as others have mentioned , but anything under about mach .85 and your good.

The B/PNC-20B may be the best nose cone Estes has ever made for the speed regimes 99% of model rockets fly in. Too bad the only way to get one from them for a BT-50 tube is to buy a Super Orbital Transporter.

 

[bwayne64]

This guy has a Bt 20b and Bt 60 3d model. If you have a printer, or know someone. You could scale the 20 up or the 60 down, ; )

https://cults3d.com/en/3d-model/various/bnc-20b-nose-cone