3D-printed Aerospike Rocket Engine • Hacker News Board

Re: 3D-printed Aerospike Rocket Engine

#31

Post by avmich » Wed, Jan 29, 2014, 5:49 PM UTC

Gravityloss wrote: post #30

Pet peeve: this is a spike nozzle, not an aerospike. The aerospike engine has a truncated physical spike that is extended by an "aerospike" that is formed by the pressurized turbine exhaust. It's still crude and early, but it's very nice that people are actually building rocket stuff! Too bad ITAR is a problem...

I think you're wrong. Spike nozzle has the spike which extends the whole length until flow from different sides converges. Aerospike is truncated but the circulating gas doesn't need to come from turbine; neither X-33 nor Spiral projects dropped turbine exhaust through the spike.

Re: 3D-printed Aerospike Rocket Engine

#32

Post by avmich » Wed, Jan 29, 2014, 7:29 PM UTC

Geee wrote: post #27

Hey nadirkazan. With 3D printing, could it be possible and affordable to make really tiny rocket engines for other uses, like radio controlled flying things? I'm thinking something like a moon lander, but smaller (really small, quadrocopter size). I would buy that :)

The problem is not so much building as it is cooling small engines. Scaling works against you here. You can download a good simulating tool for liquid fuel rocket engines - http://www.propulsion-analysis.com/ - it will show how, when you're decreasing engine size and fuel flow it becomes not enough fuel to cool of the engine.

Spike nozzle is particularly problematic around the throat, which has bigger area than for a regular bell-shaped nozzle.

Re: 3D-printed Aerospike Rocket Engine

#33

Post by nadirkazan » Wed, Jan 29, 2014, 7:53 PM UTC

Geee wrote: post #27

Hey nadirkazan. With 3D printing, could it be possible and affordable to make really tiny rocket engines for other uses, like radio controlled flying things? I'm thinking something like a moon lander, but smaller (really small, quadrocopter size). I would buy that :)

Hi. Theoretically yes, and we started there, but as someone mentioned, it has really low efficiency and will work only for few seconds. It would be expensive, and people are likely to stick with solid rockets for heir simplicity.

Re: 3D-printed Aerospike Rocket Engine

#34

Post by nadirkazan » Wed, Jan 29, 2014, 7:56 PM UTC

infogulch wrote: post #26

nadirkazan wrote: post #21

Earlier quoted context omitted.

I am the creator of this Kickstarter project. Kickstarter mostly is used to promote the project. We're actually in fundraising mode in Boost accelerator before Demo Day 11th February. I agree with you that Kickstarter is not the best venue to raise money for highly technical project.

Ah, that explains why the Kickstarter page looked so..., well, sloppy. (No offence.) It seems as if one requires an entire marketing department to start a "proper" kickstarter these days.

This was done mostly to attract attention and publicity. Our team at Boost accelerator is fundraising 500k.

Re: 3D-printed Aerospike Rocket Engine

#35

Post by nadirkazan » Wed, Jan 29, 2014, 8:01 PM UTC

mkw5053 wrote: post #16

This timeline is not realistic. No discussion of a control system at all for guidance and (more difficult) stability.

This project is for engine only. We are separately raising 500k to build a rocket and develop our GNC software.

Re: 3D-printed Aerospike Rocket Engine

#36

Post by Crito » Wed, Jan 29, 2014, 8:06 PM UTC

nether wrote: post #18

VladRussian2 wrote: post #3

is it subject to ITAR?

I don't know. When I was in university we had similar projects going on (scratch-fabricated hybrid rocket motors, not aerospikes though) and I know there were non-citizen students participating. Didn't seem to be a problem.

I think the issue would be that they intend this engine to be the upper stage of a satellite launch platform. ITAR kicks in when you get up to that capability I believe.

Re: 3D-printed Aerospike Rocket Engine

#37

Post by Gravityloss » Thu, Jan 30, 2014, 12:32 AM UTC

avmich wrote: post #31

Gravityloss wrote: post #30

Pet peeve: this is a spike nozzle, not an aerospike. The aerospike engine has a truncated physical spike that is extended by an "aerospike" that is formed by the pressurized turbine exhaust. It's still crude and early, but it's very nice that people are actually building rocket stuff! Too bad ITAR is a problem...

I think you're wrong. Spike nozzle has the spike which extends the whole length until flow from different sides converges. Aerospike is truncated but the circulating gas doesn't need to come from turbine; neither X-33 nor Spiral projects dropped turbine exhaust through the spike.

NASA CR-1998-207923 The Control System for the X-33 Linear Aerospike Engine by Jerry E. Jackson, Erich Espenchied, Jeffrey Klop

"A secondary flow (turbine drive gases) is exhausthed throug the nozzle base and adds to the recirculating flow to increase the base pressure and the overall nozzle efficiency."

http://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/1998017...

Had to curl it, since pdf.js always froze before loading it. For some reason the column layout is broken so quoting the text required quite a lot of hand editing.

Re: 3D-printed Aerospike Rocket Engine

#38

Post by Gravityloss » Thu, Jan 30, 2014, 12:33 AM UTC

avmich wrote: post #32

Geee wrote: post #27

Hey nadirkazan. With 3D printing, could it be possible and affordable to make really tiny rocket engines for other uses, like radio controlled flying things? I'm thinking something like a moon lander, but smaller (really small, quadrocopter size). I would buy that :)

The problem is not so much building as it is cooling small engines. Scaling works against you here. You can download a good simulating tool for liquid fuel rocket engines - http://www.propulsion-analysis.com/ - it will show how, when you're decreasing engine size and fuel flow it becomes not enough fuel to cool of the engine. Spike nozzle is particularly problematic around the throat, which has bigger area than for a…

A heat sink engine could work in pulsed operation.

Re: 3D-printed Aerospike Rocket Engine

#39

Post by avmich » Thu, Jan 30, 2014, 6:58 AM UTC

Gravityloss wrote: post #38

avmich wrote: post #32

Earlier quoted context omitted.

The problem is not so much building as it is cooling small engines. Scaling works against you here. You can download a good simulating tool for liquid fuel rocket engines - http://www.propulsion-analysis.com/ - it will show how, when you're decreasing engine size and fuel flow it becomes not enough fuel to cool of the engine. Spike nozzle is particularly problematic around the throat, which has bigger area than for a…

A heat sink engine could work in pulsed operation.

True. However this mode isn't very useful when you need to lift something from Earth - or just to keep it in the air.

Re: 3D-printed Aerospike Rocket Engine

#40

Post by avmich » Thu, Jan 30, 2014, 7:00 AM UTC

Gravityloss wrote: post #37

avmich wrote: post #31

Earlier quoted context omitted.

I think you're wrong. Spike nozzle has the spike which extends the whole length until flow from different sides converges. Aerospike is truncated but the circulating gas doesn't need to come from turbine; neither X-33 nor Spiral projects dropped turbine exhaust through the spike.

NASA CR-1998-207923 The Control System for the X-33 Linear Aerospike Engine by Jerry E. Jackson, Erich Espenchied, Jeffrey Klop "A secondary flow (turbine drive gases) is exhausthed throug the nozzle base and adds to the recirculating flow to increase the base pressure and the overall nozzle efficiency." http://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/1998017... Had to curl it, since pdf.js always froze before l…

Thank you. However, turbine exhaust can't provide much thrust - both flow and speed aren't large. So the spike nozzle doesn't get much thrust from turbine gases - yet it can get it from chamber gases.