Linear Aerospike Nozzle Minor (Autosaved)

LINEAR AEROSPIKE
NOZZLE
AND
CFD ANANLYSIS
INDEX
• 1. The basic definitions
• 2. Bell Nozzle
• 3. Aerospike Nozzle
• 4. Aerospike Engine
• 5. Why is engine called aerospike ?
• 6. Types of an aerospike nozzle
• 7. Why is there a spike ?
• 8. Efficiency at all altitudes
• 9. Significance of mach lines
• 10. Adavntages
• 11. Disadvantages
• 12.SSTO
THE BASIC DEFINITIONS TO BRUSH UP
WITH:-
1. What do we understand by linear ?
2. What is a nozzle ?
3. What do we understand by CFD?
4. What is an aerospike ?
What is a bell nozzle ?
The bell shaped nozzle is probably the most commonly used shaped rocket engine nozzle. It has a high angle
expansion section (20 to 50 degrees) right behind the nozzle throat; this is followed by a gradual reversal of
nozzle contour slope so that at the nozzle exit the divergence angle is small, usually less than a 10 degree half
angle.
The bell or contour shape is designed to impart a large angle expansion for the gases right after the throat. The
nozzle is then curved back in to give a nearly straight flow of gas out the nozzle opening.
What is an aerospike nozzle?
Aerospike nozzles are rather unique, in that they are somewhat of a reverse version of the standard bell nozzle.
Instead of using a shroud to contain the exit flow, aerospikes direct the flow along the exterior of the nozzle.
The interesting thing about the aerospike nozzle is that it overcomes problems with varying back-pressure by
simply using the local atmospheric pressure to control the flow area.
Instead of using a physical shroud to contain the exhaust flow, the outer boundary is defined naturally by the
local back-pressure. This results in a smoothly varying exit flow area which is always optimized as back-
pressure changes.
What is an aerospike engine ?
It is a type of rocket engine that maintains its aerodynamic efficiency across a wide range
of altitudes . It belongs to the class of altitude compensating nozzle engines. A vehicle with an
aerospike engine uses 25–30% less fuel at low altitudes,where most missions have the greatest
need for thrust. Aerospike engines have been studied for a number of years and are the baseline
engines for many single-stage-to-orbit (SSTO) designs and were also a strong contender for
the Space Shuttle main engine. However, no such engine is in commercial production, although
some large-scale aerospikes are in testing phases.
The terminology in the literature surrounding this subject is somewhat confused—the

term aerospike was originally used for a truncated plug nozzle with a very rough conical taper
and some gas injection, forming an "air spike" to help make up for the absence of the plug tail.
However, frequently, a full-length plug nozzle is now called an aerospike.
Why is the engine called an aerospike?
The aerospike engine is so named because the nozzle resembles a spike. A plug nozzle is a
truncated aerospike nozzle.
Aerospike comes from the idea of introducing an additional flow into the base region of the
truncated spike, forming an "aerodynamic spike" with the base flow. Basically the base flow
helps fill in the area underneath the base and helps make up for the performance loss from
truncating the nozzle. The word Aerospike is actually a Rocketdyne trade name that refers to,
usually, a truncated spike nozzle with a base flow.
What are the two types of an aerospike nozzle
?
There are two types of aerospike nozzles. The first of which is the toroidal aerospike. The characteristic
spike gave the nozzle its name. Exhaust flow is directed from a toroidal shape around the exterior of the
nozzle towards the spike, which results in a flow that expands to the optimal diameter as local pressure
varies.
The second type is linear aerospike, seen here. This is a wedge-shaped nozzle, which has a linear exhaust
profile. Linear aerospikes are exceptionally odd looking, but very effective. Exhaust is directed inward
from a series of ports along each side of the wedge, and expands to an optimal flow area as local pressure
varies.
Why is there a spike ?
The answer is that the solid wall is the surface area upon which the axial component of the wall pressure pushes
against to produce the thrust. If you didn't have a nozzle wall against which to push, there would be no thrust
produced.
The beauty of the aerospike nozzle is that you can truncate it and the thrust which is developed by the base
pressure build up almost entirely makes up for the thrust loss due to the decrease in nozzle surface area.
What is efficiency at all altitudes ?
The key to a conventional bell nozzle’s level of performance is its width. At high pressure -- i. The key to a
conventional e. sea level -- the gasses are more tightly focused, so a bell nozzle with a narrow interior surface
works best. At low pressure i.e. higher altitudes -- a wider interior woThe key to a conventional bell nozzle's
level of performance is its rks best as the gasses will expand farther.
Since the width of the bell nozzles can't change to match the atmospheric pressure as the rocket climbs, bell
nozzles are normally designed to provide optimum performance at one certain altitude or pressure. This is called
a "point design," and engineers accept the performance loss the nozzle will encounter at any altitude other than
the one it was designed for.
What is the difference between an aerospike
nozzle and a bell shaped nozzle ?
What is the significance of mach lines in the
designing of an aerospike nozzle ?
What are the advantages ?
• Smaller nozzle: The truncated spike can be far smaller than a typical bell nozzle for the same
performance, as shown below. In addition, a spike can give greater performance for a given length.
• Superior performance: Altitude compensation may result in greater installed performance.
• Less risk of failure: The aerospike engine uses a simple gas generator cycle with a lower chamber
pressure than typical rocket engines reducing the risk of a catastrophic explosion. Although low
chamber pressures result in reduced performance, the aerospike's high expansion ratio makes up for
this deficiency.
• Lower vehicle drag: The aerospike nozzle fills the base portion of the vehicle thereby reducing a
type of drag called base drag.
What are the disadvantages?
•Cooling: The central spike experiences far greater heat fluxes than does a bell nozzle. This problem can be
addressed by truncating the spike to reduce the exposed area and by passing cold cryogenically-cooled fuel
through the spike. The secondary flow also helps to cool the centerbody.
•Manufacturing: The aerospike is more complex and difficult to manufacture than the bell nozzle. As a result, it
is more costly.
•Flight experience: No aerospike engine has ever flown in a rocket application. As a result, little flight design
experience has been gained.
SINGLE-STAGE-TO-ORBIT
A SSTO vehicle reaches orbit from the surface of a body using only propellants and fluids and without
expending tanks, engines, or other major hardware. The term usually, but not exclusively, refers to reusable
vehicle .To date, no Earth-launched SSTO launch vehicles have ever been flown; orbital launches from Earth
have been performed by either fully or partially expendable multi-stage rockets.
The main projected advantage of the SSTO concept is elimination of the hardware replacement inherent in
expendable launch systems. However, the non-recurring costs associated with design, development, research
and engineering (DDR&E) of reusable SSTO systems are much higher than expendable systems due to the
substantial technical challenges of SSTO, assuming that those technical issues can in fact be solved.

Linear Aerospike Nozzle Minor (Autosaved)

Uploaded by

Copyright:

Available Formats

Linear Aerospike Nozzle Minor (Autosaved)

Uploaded by

Document Information

Original Description:

Original Title

Copyright

Available Formats

Share this document

Share or Embed Document

Sharing Options

Did you find this document useful?

Is this content inappropriate?

Copyright:

Available Formats

Linear Aerospike Nozzle Minor (Autosaved)

Uploaded by

Copyright:

Available Formats

LINEAR AEROSPIKE

The terminology in the literature surrounding this subject is somewhat confused—the

You might also like