XCOR and the Lynx rocket

[john smith 19]

My 1000lb engine under construction uses 3 inch turbine runs at 30000 to 60000 RPM, not 1/4 inch turbine at millions of RPM. Same sized model aircraft gas turbine runs at 60000 to 120000 RPM, with 24 hrs life before disassemble repair.

Firstly congratulations on actually building such an engine. It will be most instructive.

What I neglected to mention about the MIT Micro-rocket engine programme was its stated goal of a T/W ratio of 1000:1. 

What  do you expect the T/W ratio of your engine will be? model gas turbines are IIRC somewhere in the 2-3:1 T/W ratio range.

Indeed the XCOR nonburnite is a fluoropolymer that can't burn, rather than marginally compatible.
Maybe worthy for SpaceX to buy it?
https://xcor.com/propulsion/nonburnite/

I think anyone whose business involves building LOX tanks where there is any kind of mass issue could have an interest in this IP.

[Katana]

My 1000lb engine under construction uses 3 inch turbine runs at 30000 to 60000 RPM, not 1/4 inch turbine at millions of RPM. Same sized model aircraft gas turbine runs at 60000 to 120000 RPM, with 24 hrs life before disassemble repair.

Firstly congratulations on actually building such an engine. It will be most instructive.

What I neglected to mention about the MIT Micro-rocket engine programme was its stated goal of a T/W ratio of 1000:1. 

What  do you expect the T/W ratio of your engine will be? model gas turbines are IIRC somewhere in the 2-3:1 T/W ratio range.

Indeed the XCOR nonburnite is a fluoropolymer that can't burn, rather than marginally compatible.
Maybe worthy for SpaceX to buy it?
https://xcor.com/propulsion/nonburnite/

I think anyone whose business involves building LOX tanks where there is any kind of mass issue could have an interest in this IP.

Expected T/W ratio around 50, where model gas turbines nowadays around 10
http://www.jetcatamericas.com/

[john smith 19]

Expected T/W ratio around 50, where model gas turbines nowadays around 10
http://www.jetcatamericas.com/

while 50:1 is respectable for a home brew effort (and would be excellent if you were using LH2) it's not exactly cutting edge for an expendable rocket engine.

I'm quite surprised they are that good. That's the same as a Trent 900 for the airbus.

I presume the short operating times and overall life time mean they cna afford to operate with much smaller safety margins.

[Katana]

Expected T/W ratio around 50, where model gas turbines nowadays around 10
http://www.jetcatamericas.com/

while 50:1 is respectable for a home brew effort (and would be excellent if you were using LH2) it's not exactly cutting edge for an expendable rocket engine.

I'm quite surprised they are that good. That's the same as a Trent 900 for the airbus.

I presume the short operating times and overall life time mean they cna afford to operate with much smaller safety margins.

By scaling law, small turbomachines are less efficient but have better T/W than large counterparts.
Those small engines are scaled down version of centrifugal turbojets in 1940s~1950s with T/W = 2~3.
https://en.wikipedia.org/wiki/Power_Jets_W.2
https://en.wikipedia.org/wiki/Rolls-Royce_Nene
Turbine material and fabrication technology are based on automobile turbochargers. Difference on life compared to automobile turbochargers come from differences on bearings.

[Robotbeat]

Can we Kickstarter XCOR back to life?

[woods170]

Can we Kickstarter XCOR back to life?

Please no. Just put that thing out of it's misery.

[whitelancer64]

Can we Kickstarter XCOR back to life?

Not at the funding levels required. The most successful gofundme / kickstarters ever wouldn't make a dent for funding a project like Lynx. Also keep in mind that historically, aerospace crowdfunding efforts have failed miserably.

[Lars-J]

Can we Kickstarter XCOR back to life?

Why? What were they doing that needs to revived? They failed for a reason.

[Robotbeat]

Can we Kickstarter XCOR back to life?

Why? What were they doing that needs to revived? They failed for a reason.

Could give the expendable smallsat launchers a run for their money.

[Robotbeat]

Id convert Lynx to a smallsat launcher from the get go. I'd get rid of the pilot and make it a drone.

XCOR had a bunch of IP relating to extremely reusable engines. I'd leverage that.

XCOR makes way more sense than most NewSpace startups.

[Lars-J]

Can we Kickstarter XCOR back to life?

Why? What were they doing that needs to revived? They failed for a reason.

Could give the expendable smallsat launchers a run for their money.

How? With Lynx? After several years they never even assembled a prototype, never rolled one inch on a runway.

XCOR had a bunch of IP relating to extremely reusable engines. I'd leverage that.

Can you quantify "extremely reusable"? I've googled, but all test result claims of high re-usability that I have found stem from 2011(!), but lacking details.

[Robotbeat]

2011 is closer to when XCOR was in their prime.

[Robotbeat]

Y'all suck. 

[Tomness]

Let the past die. Kill it, if you have to. It's the only way to become what you were meant to be. - Kylo Ren

[ChrisWilson68]

XCOR makes way more sense than most NewSpace startups.

Yeah.  Like zero is ten times better than zero.

[savuporo]

XCOR makes way more sense than most NewSpace startups.

Yeah.  Like zero is ten times better than zero.

Because startup companies like Planet , BlackSky, GeoOptics, Satellogic , Spire and many others are all just fun and hobbies, not people who have built completely new businesses, revenue streams and customer bases on orbit. Right ?

[meekGee]

XCOR makes way more sense than most NewSpace startups.

Yeah.  Like zero is ten times better than zero.

Like zero is better than NaN.

The SmallSat and suborbital markets have still to show that there's anything there other than exponentially increasing viewgraphs...

But with XCOR, the engineering approach, the reusable engine, the company itself - all were more appetizing than the other players in the field.

But, fail it did, the founders have moved on, and that's the end of that.

[Gliderflyer]

Can you quantify "extremely reusable"? I've googled, but all test result claims of high re-usability that I have found stem from 2011(!), but lacking details.

Keeping things to publicly available information, they basically eliminated thermal-cyclic fatigue from the chamber. Most regeneratively cooled engines yield and plastically deform on startup and shutdown, which limits them to 100 or so firings before the chamber breaks from the low-cycle fatigue. Eliminating this increases the number of starts an engine can do, well up into the thousands. "Reusable Rocket Propulsion for Space Tourism Vehicles" has a decent (if old) overview. There were a few other tricks, but thermal-cyclic fatigue was one of the big ones.

[john smith 19]

Keeping things to publicly available information, they basically eliminated thermal-cyclic fatigue from the chamber. Most regeneratively cooled engines yield and plastically deform on startup and shutdown, which limits them to 100 or so firings before the chamber breaks from the low-cycle fatigue. Eliminating this increases the number of starts an engine can do, well up into the thousands. "Reusable Rocket Propulsion for Space Tourism Vehicles" has a decent (if old) overview. There were a few other tricks, but thermal-cyclic fatigue was one of the big ones.

Thanks for that. That understanding, what's really important in making a low maintenance, fast turnaround vehicle, is part of what XCOR going out of business will lose.  Jones may be one of the best practical rocket engine engineers of his generation.

Historical note. When the British were looking at upgrading the engines on the Black Arrow LV they were looking at scrapping the tube wall cooing and reverting to the system in the paper, to eliminate impurities in the tubes creating gas bubbles in them and triggering burn through.

Having read up on the situation with the SSME walls (which were a Copper alloy) I've often wondered abut a channel wall and outside sheath being joined at the bottom end. As the liner heats up instead of the coolant (whatever it is) spraying more-or-less randomly on the inside wall it becomes constrained to only flow in the channels. IOW Don't fight the thermal wall growth, use it. That wall is going to be very thermally stressed whatever happens.

[EDIT There was also a NASA paper on heat pipe cooling of a thrust chamber to spread the heat from the hot parts to the cooler ares, given lower stress gradients, which I though was quite clever but did not give you the energy boost you got from tapping the heat from the wall metal ]

[john smith 19]

Id convert Lynx to a smallsat launcher from the get go. I'd get rid of the pilot and make it a drone.

Actually that was one of the markets they were looking at, with a pod housing an expendable US replacing the
passenger.

XCOR had a bunch of IP relating to extremely reusable engines. I'd leverage that.

Very true.  They emphasize the long-EZ but a lot of that work was done for the Rocket Racing League, which sadly never happened.

XCOR makes way more sense than most NewSpace startups.

True, they were very pragmatic about doing stuff that got them closer to their ultimate goal.

Part of it was it turned out that their ultimate goal was very hard. IIRC Jeff Greason commented CFD could not be entirely trusted. You needed wind tunnel testing. That's how they learned about tweaking the pilot/passenger layout on Lynx.

The other issue was that what they wanted to get funded was 2 generations away from a full TSTO spaceplane. This was IMHO a recognition of how far they felt they were from understanding all the issues, but it was not what investors wanted to hear. There were also issues with the fabricators whose "can-do" attitude turned out to be more a "can-not" do in the end

It seems in startup land setting realistic goals is good, but setting unrealistic goals is much better.