Are Aerospikes Better Than Bell Nozzles?

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BBowmaster

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I wish someone would build and fly an aerospike. Especially a linear aerospike. His analogy to rotary gasoline engines is good. There are specific applications where rotary engines are superior to piston engines. Maybe aerospikes have similar niches we’ll discover when more of our time is spent on things besides getting from ground to LEO.
 

MClark

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It's been done. A round one.
One was 15 or so years ago by a guy who worked with us as a consultant, Rodney Beyer.
I believe the propellant was a K550 and was launched at Salt Flats.
Rodney literally wrote the book on rocket motor ignition,
NASA TN D-132, 1959. Beyer, Rodney B., and Fishman, Norman: Solid Propellant Ignition Studies with High Flux Radiant Energy as a Thermal Source. Prog. in Astronautics and Rocketry. Vol. 1 - Solid Propellant ...
 

mpitfield

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This is an excellent general informational video for anyone who wants a slightly deeper dive into some of the physics involved in our hobby motors.
 

aerostadt

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There is a good table of contents screen a couple minutes into the video, which I thought was good. I skipped ahead to about 41:30 to see the discussion of pro's and con's and future of the aerospike.
 

Winston

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Startup Tries to Revive Interest in Aerospike Rocket Engines
NextAero, an advanced manufacturing startup in Australia, is 3D printing aerospike engines for satellite launch vehicles
18 Dec 2019

https://spectrum.ieee.org/tech-talk...change-the-course-of-aerospike-rocket-engines

To build its first rocket engine within four months in 2017, NextAero turned to additive manufacturing, also known as 3D printing. ProjectX, an aerospike combustion engine, relies on compressed natural gas and gaseous oxygen for fuel. The proof-of-concept engine has water channels below its surface for active cooling and multiple combustion chambers separated by fins to hold the spike. It produces 4 kilonewtons of thrust at sea level—small compared to the 7,607 kilonewtons of thrust from SpaceX's Falcon 9 rocket, which the aerospace company described as "thrust greater than five [Boeing] 747s at full power," or the 2 meganewtons of thrust of the Raptor engine that will power SpaceX's in-development Starship spacecraft.

The aerospike design comes with the benefit of increased engine efficiency. As the rocket travels through the atmosphere, the spike allows it to expand the plume, giving it extra thrust—about 25 to 35 percent more than conventional rocket engines of the same size, according to Bell.



The only successful flight involving the design so far is NASA's Dryden Aerospike Rocket Test in 2004, which saw the launch of two solid-fuel rockets with aerospike nozzles. As NASA wrote in its report about the flight: "Although the advantages of the aerospike nozzles are well understood through analysis and ground test data, a shortage of actual published flight test data has precluded use of these nozzles in current as well as next generation space launch vehicles. In addition, the configuration of an aerospike nozzle presents unique challenges to the designer and fabricator."

Pointy End Up? With Aerospike Rockets, It's Down, Too!

https://www.nasa.gov/missions/research/aerospike_rocket.html

 

aerostadt

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In the 1990's there were lots of new rocket concepts including aero-spikes. The only concept that was not proposed then, but survives until now is Space-X's Falcon 9 that uses rocket landing for first stage.
 

kuririn

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If jet engine designers can create variable area nozzles for fighter planes, why not for rocket nozzles?
Adjustable leaves expanding or contracting to maximize efficiency of the exhaust plume.
 

aerostadt

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If jet engine designers can create variable area nozzles for fighter planes, why not for rocket nozzles?
Adjustable leaves expanding or contracting to maximize efficiency of the exhaust plume.
As I recall at about 41 minutes into the video of the first post the presenters give the pro's and con's of aero-spike nozzles. In order for an aero-spike nozzle to make a good contribution to a flight it has to burn as long as a bell nozzle over an appreciable change in altitude. I would think that heat transfer for such a long duration burn would pose unique problems for a an aero-spike nozzle, especially, an annular aero-spike nozzle. Perhaps, a linear aero-spike would not be so bad. Offhand I don't know if much work has been done in this area. In a jet plane engine exhaust the conditions are not as extreme. A jet engine brings in so much nitrogen with the incoming air that the exhaust does not get as hot.
 

0011001100

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If jet engine designers can create variable area nozzles for fighter planes, why not for rocket nozzles?
Adjustable leaves expanding or contracting to maximize efficiency of the exhaust plume.
Temperature and combustion products. Some of the combustion products are highly corrosive and would likely destroy the mechanism very quickly.
 

Rob702Martinez

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I wish someone would build and fly an aerospike. Especially a linear aerospike. His analogy to rotary gasoline engines is good. There are specific applications where rotary engines are superior to piston engines. Maybe aerospikes have similar niches we’ll discover when more of our time is spent on things besides getting from ground to LEO.
Indeed.......
IMG_20181006_012956_763.jpg
 

dhbarr

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Sure, McDonnell and DC-X were in the running, but it pooped out.
I only meant that the vertical landing w/ fast reuse, while being a staple of old sci fi, was seriously investigated and successfully executed in the early 90's.
 

aerostadt

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I only meant that the vertical landing w/ fast reuse, while being a staple of old sci fi, was seriously investigated and successfully executed in the early 90's.
Yes, you are right McDonnell did set a new trend for vertical rocket take-off and landing. I did forget that and, of course, the sci-fi lore like "Rocky Jones" did it all the time on TV in the 1950's. Actually, NASA did some rocket landing on the moon with Surveyor and Apollo. I was thinking of Kistler with their 2-stage rocket in the 1990's that planned to land both stages with parachutes. Even that did not come to pass. The DC-X only got to 40,000 feet and zero velocity at that altitude. Obviously, they developed the guidance for take-off and landing. Space-X really perfected things with recovering at first stage altitudes and speeds and even developed grid fins. They developed an operational basis to land on a barge at sea and even fly back to Florida to land on solid ground. We are still waiting for some kind of operational aero-spike.
 

Nytrunner

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We are still waiting for some kind of operational aero-spike.
We may be waiting awhile.

As an an older senior engineer on my previous project was fond of saying "the juice hasn't been worth the squeeze"
 

aerostadt

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Someone is planning a short aerospike suborbital flight. Hopefully, this will happen and will be in the near future.
 

boomtube-mk2

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Personally I'm hoping that somebody out there is experimenting with, or at the very least trying to develop, the technology that will replace rockets altogether.

As much as they are fun to play around with, they are the technological equivalent of the
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In fact, not even that.
 

jqavins

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"Technological equivalent"? What is your operational definition of "equivalent"? How are "obsolescent and long overdue for replacement" and "replaced by improved versions a century and a half ago" equivalent?

That said, yes, rockets should not be the method of choice for lifting stuff from Earth's surface to space.
 

Antares JS

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I would think that heat transfer for such a long duration burn would pose unique problems for a an aero-spike nozzle (...)
This is precisely the reason aerospikes have not taken off. They are theoretically more efficent, but the cost/benefit doesn't work out given the hassle involved. Remember Firefly was going to use aerospikes but ended up sticking with conventional engines after the bankruptcy because the aerospikes were too costly to develop.

That said, yes, rockets should not be the method of choice for lifting stuff from Earth's surface to space.
Then what method do you suggest?
 

Antares JS

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Personally I'm hoping that somebody out there is experimenting with, or at the very least trying to develop, the technology that will replace rockets altogether.

As much as they are fun to play around with, they are the technological equivalent of the
View attachment 483686
In fact, not even that.
I find this analogy ludicrous. This is like saying we need to replace cars with something else because they are all technologically equivalent to the Model T. No sir, a modern diesel engine is not technologically equivalent to that, a Tesla Model S is not technologically equivalent to the Model T, and the Falcon 9 is not technologically equivalent to Goddard's Nell.
 

boomtube-mk2

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Rockets are the technological equivalent of early steam locomotives.
The first liquid fuel rocket was launched in 1926.
Ninety-five years ago and we are still using the same technology.
Fuel go Boom! Rocket go up.
Yes, we have improved on the materials and electronics, the ability to land the booster is impressive but it doesn't change the basic tech. for getting stuff into orbit.

Personally I'm not sure there is anything that can replace rockets, the "Space Elevator" is pure Science Fiction with the emphasis on fiction and even if it could be built, it probably wouldn't be allowed to be built.
As for "Anti-Gravity" . . . there's nothing we can even hang our hat on with regards to a theory allowing for Anti-Gravity.
It makes me wonder if this is the real reason why some civilization hasn't already colinized the Galaxy; getting out of the home-world's gravity well is prohibitively costly in both energy and economic terms.
 

jqavins

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Then what method do you suggest?
Ah, indeed, there's the rub. I don't have a good answer. Things like space elevators and orbiting cables and others that have been discussed in gross concept all have major technical hurdles in front of them, some of which may well be impossible to overcome. And I don't know which. I maintain that there must be something better than burning tons and tons of fuel in a vehicle that is many time more likely to blow up* than contemporary ground, air, and sea vehicles can't be the best way to get to space in the long term. And, like boomtube-mk2, "I'm hoping that somebody out there is experimenting with, or at the very least trying to develop, the technology that will replace rockets altogether", even though I can't say what that will be.

EDIT: OK, I was ninjad. I still argue against the word "equivalent". The fundamental similarity between the rockets of today and Nell is actually greater than that between early steam locomotives and the locos of today, which don't use steam at all, but that's an unnecessary digression.

It makes me wonder if this is the real reason why some civilization hasn't already colinized the Galaxy; getting out of the home-world's gravity well is prohibitively costly in both energy and economic terms.
I believe the reason that no one has colonized the galaxy is that there is no more reason to think FTL travel is possible than that anti-gravity it. Probably less.

* Not very likely, yet many time more likely than cars, planes, and ships.
 
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boomtube-mk2

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Tesla Model S is not technologically equivalent to the Model T,
Well there is a technological shift between the Tesla and the Model T. The Model T used an internal combustion engine while the Tesla uses an electric motor.

The Nell used a liquid fuel rocket motor and the Falcon uses a liquid fuel rocket motor.
The Falcon is more advanced but it is the same in its use of a rocket motor.
My thoughts is that we need the difference between the steam locomotive and the diesel-electric locomotive.
The first is an external combustion engine with a very low efficiency while the latter is an internal combustion engine combined with electric traction motors that is vastly more efficient.
With regards to putting stuff into space, we haven't yet made that technological leap between the "Steamer" and the DE Locomotive.
 
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