3D printing rocket engines

[guckyfan]

I understand rocket engines are usually made of copper because it can easily  be machined with the cooling channels and also has good heat conduction properties. However copper is not a very strong material and also not very heat resistant.

Making them of Inconel is very hard to do because the material cannot be machined in the same way. However assume that 3D printing advances enough to make printing large engines feasible. Would Inconel even be a suitable material? It is strong so it should be possible to make the combustion chamber and the regeneratively cooled part of the nozzle much lighter. At least that would be my uneducated guess.

But how would the material react to thermal cycles as the heat conduction capacity is much smaller? Thinner walls would only in a small part compensate for the lower conductivity. So what's your thought, would Inconel be a suitable material for large engines, especially if they are to be reusable and go through very many cycles?

I am thinking of the Raptor engine but it really is a general question.

Some guesswork figures. I have seen estimates the Raptor may have a weight of ~7 tons. Would 4 tons for combustion chamber and nozzle be right? There was mention of printers able to print 1kg/h. Assume that advancing technology makes 10kg feasible. That would give a time of 400 hours for printing one engine. That translates to ~20 engines per year. With high reusability from the beginning this may be enough so one or two printers could do the job.

There was also the price of 500$/kg Inconel powder. That would bring material cost to just 2 Million Dollars per engine but with that much demand prices may even drop.

[R7]

SuperDraco

[guckyfan]

SuperDraco

Yes, I am aware of that. But it is a very different size and very different task. I would not presume an Inclonel-Raptor will be an efficient design because SuperDraco is.

[R7]

F-1

The tubes comprising the thrust chamber were heavily jacketed at the combustion chamber and were reinforced by a series of bands around the nozzle. The thrust chamber's tubes were constructed of Inconel X-750, a high-temperature, heat-treatable, nickel base alloy. 178 primary tubes, hydraulically formed from 1-3/32 inch outside diameter Inconel-X tubing, made up the chamber body above the 3:1 expansion ratio plane (approximately 30 inches below the throat centerline plane). At this point, the tubes bifurcated, or split in two. Two one-inch-outside-diameter secondary tubes were spliced to each primary tube and formed the chamber from the 3:1 to the 10:1 expansion ratio plane.

Nothing wrong with Inconel as material for big engines. Challenge is to construct big enough 3D printer.

[go4mars]

Nothing wrong with Inconel as material for big engines. Challenge is to construct big enough 3D printer.

I read somewhere that EOS has one big enough to print aircraft wings in titanium or Inconel.

[docmordrid]

Nanfang Ventilator Co. of China has one that can print a diameter of 2.1 x 6.0 meters up to a mass of 300 tonnes. Mainly steels, including stainless, but it seems size is becoming less of a factor almost weekly.

[R7]

Cool. Is the surface quality of these big machines adequate for coolant channels and nozzle wall without post-processing?

Also are there machines that can print aluminium alloys? Lower melting point sure but way superior thermal conductivity and specific strength. Might cope with cryogenic coolants and/or something additional deposited on hot wall to reduce Al structure temperature.

[guckyfan]

Is the surface quality of these big machines adequate for coolant channels and nozzle wall without post-processing?

I think the surface quality correlates not with size but with printing speed. Maybe using several "print heads" parallel can help with speed instead of raw power of one print head. I imagine special printers can be designed for objects with mainly rotational symmetry. Let the print head or heads rotate plus radial linear instead of two linear movements. That should help with print quality. On a wide diameter several printheads fit. Going to the center less radial linear heads can be placed.

[guckyfan]

Also are there machines that can print aluminium alloys? Lower melting point sure but way superior thermal conductivity and specific strength. Might cope with cryogenic coolants and/or something additional deposited on hot wall to reduce Al structure temperature.

Since Aluminium can be machined as easily as copper I think it would already be used if it had advantages over copper.

[docmordrid]

The XCOR Lynx 5K18 engine has been used to test an aluminum nozzle. Co-developed with ULA as part of their joint projects.

http://xcor.com/press/2011/11-03-22_XCOR_and_ULA_demonstrate_rocket_engine_nozzle.html

[Prober]

F-1

The tubes comprising the thrust chamber were heavily jacketed at the combustion chamber and were reinforced by a series of bands around the nozzle. The thrust chamber's tubes were constructed of Inconel X-750, a high-temperature, heat-treatable, nickel base alloy. 178 primary tubes, hydraulically formed from 1-3/32 inch outside diameter Inconel-X tubing, made up the chamber body above the 3:1 expansion ratio plane (approximately 30 inches below the throat centerline plane). At this point, the tubes bifurcated, or split in two. Two one-inch-outside-diameter secondary tubes were spliced to each primary tube and formed the chamber from the 3:1 to the 10:1 expansion ratio plane.

Nothing wrong with Inconel as material for big engines. Challenge is to construct big enough 3D printer.

See how they re did the F-1 with some modern day toolsets.  http://forum.nasaspaceflight.com/index.php?topic=33141.msg1175892#msg1175892

[docmordrid]

Nothing wrong with Inconel as material for big engines. Challenge is to construct big enough 3D printer.

I read somewhere that EOS has one big enough to print aircraft wings in titanium or Inconel.

And SpaceX has an existing relationship with EOS - one of their printers is used to build SuperDraco.

I'd be shocked of they didn't try printing at least some Raptor parts.

[Prober]

Nothing wrong with Inconel as material for big engines. Challenge is to construct big enough 3D printer.

I read somewhere that EOS has one big enough to print aircraft wings in titanium or Inconel.

And SpaceX has an existing relationship with EOS - one of their printers is used to build SuperDraco.

I'd be shocked of they didn't try printing at least some Raptor parts.

I remember years ago some announcement of a new method to make titanium (outside or before 3D printing).

The claim what they could make Titanium out the door as cheap as steel.

[docmordrid]

And now Metalisys is making moves with 3D metal printer alloys.  If they're for real it'll be real interesting.

[sdsds]

http://www.businessweek.com/articles/2013-11-27/general-electric-turns-to-3d-printers-for-plane-parts

Each Leap engine will contain 19 metal 3D-printed fuel nozzles.

Not rockets, but "high-bypass turbofan" engineering is pretty close.

[Prober]

And now Metalisys is making moves with 3D metal printer alloys.  If they're for real it'll be real interesting.

they are for real.

 “The Metalysis process could reduce the price of titanium by as much as 75 per cent, making titanium almost as cheap as specialty steels. We believe that titanium made by the Metalysis process could replace the current use of aluminium and steel in many products. This world-first for a titanium 3D printed component brings us a step closer to making this a reality.” - See more at: http://www.themanufacturer.com/articles/metalysis-low-cost-titanium-powder-to-3d-print-automotive-parts/#sthash.vaw08xUO.dpuf


Believe a Ukraine Univ. also has something with Titanium.  btw: Ukraine & Titanium is a story more.

Another thought.......think of the Shuttle we could have had with more Titanium to work with at a low cost.

[baldusi]

I understand rocket engines are usually made of copper because it can easily  be machined with the cooling channels and also has good heat conduction properties. However copper is not a very strong material and also not very heat resistant.

AIUI, MCC are usually made out of Inconel, but have a copper lining applied on the inside. Combustion is not homogeneous, and the heat transfer characteristics of copper allow for heat to transfer to the colder parts and thus use more surface area. I think that I've also seen some regeneratively cooled MCC with the inner part, the one that has the channels milled, made out of copper, an the external part of some steel. Since the cooling channels are at higher pressure than the MCC interior, strength shouldn't be such an issue. And the channel walls work as copper radiators, which have excellent heat transfer characteristics.
Now, what would be extremely interesting is if you could 3D print with multiple metals. You could make the lining and add heat pipes. And I've always wondered about fiber wrapping the MCC and Nozzle with kevlar or such. But we're far from that technology yet.

[docmordrid]

Now, what would be extremely interesting is if you could 3D print with multiple metals. You could make the lining and add heat pipes. And I've always wondered about fiber wrapping the MCC and Nozzle with kevlar or such. But we're far from that technology yet.

You can use >1 material with some new devices, and Epson announced a few weeks ago a 5 year plan for a large scale  multi-material industrial printer for production. There was also talk of printing cars.

[TrevorMonty]

Now, what would be extremely interesting is if you could 3D print with multiple metals. You could make the lining and add heat pipes. And I've always wondered about fiber wrapping the MCC and Nozzle with kevlar or such. But we're far from that technology yet.

They do make a printer that can be used to blend 4 different metals. In the article Prober posted they were using it to create alloys, for testing their properties.

This printer may be able to do mix metals but there would be huge amount of wastage. All the unused metal powders would be mixed and couldn't be recycled.

[Adaptation]

This printer may be able to do mix metals but there would be huge amount of wastage. All the unused metal powders would be mixed and couldn't be recycled.

They could be separated.  Cyclone classifier should work well if they have different densities.  Magnetic separation could also work if some of the metals are magnetic and others aren't.  Depending on particle size you could also do froth flotation. 

To get a good quality of separation you'd probably want to sent it to someone who would specialize in it and 99.9999% (or whatever) purity may not be feasible.