Stoke Space Technologies: General Company and Development Updates and Discussions

[Darkseraph]

https://spacenews.com/stoke-raises-seed-round-to-work-on-fully-reusable-rockets/

WASHINGTON — A startup founded by a group of former Blue Origin and SpaceX employees has raised a seed round of funding to support their effort to make a fully reusable launch vehicle.

Stoke Space Technologies announced Feb. 25 it raised $9.1 million in seed funding in a round led by venture funds NFX and MaC Ventures. Several others funds and individuals participated in the round, including Y Combinator; Seven Seven Six, a new fund established by Reddit co-founder Alexis Ohanian; and Liquid2, a fund that previously invested in satellite manufacturer Astranis.

Stoke, based in the Seattle suburb of Renton, Washington, has no shortage of ambition. Its goal, the company said in its announcement of the funding round, is “100% reusable rockets designed to fly daily” that it claims could reduce the cost of space access by a factor of 20.

“We’re still in ‘reusability 1.0’ and it’s time to go to ‘reusability 2.0,’” Andy Lapsa, co-founder and chief executive of Stoke, said in an interview, citing efforts by SpaceX to recover and reuse the first stage of its Falcon 9 launch vehicle. “In reusability 1.0, these are things that can be reused but they’re not necessarily things that are operationally efficient to reuse. Reusability 2.0 is the next step, where we’re now focused on operations and quick turnaround.”

In that vision, both the rocket’s upper and lower stages would be reusable and able to be turned around quickly for another launch. “If it’s designed to fly daily and be turned around quickly, there’s a whole lot of things you are not doing,” he said, such as tearing the vehicle down between flights and doing detailed inspections. Such a vehicle would instead rely on automated checks with a minimum of labor and maintenance.

The nine-person company is currently focused on the vehicle’s upper stage. While SpaceX has demonstrated the ability to routinely reuse first stages and other companies, like Blue Origin, are following a similar path, second stages are more challenging because of their higher velocities and energies. SpaceX for a time pursued an effort to make the Falcon 9 second stage reusable, but eventually abandoned that. “The second stage is the last big domino to fall in reusable rockets,” he said.


.....

So, another startup enters the reusable launcher arena, this time focusing on making the second stage reusable with some new engine configuration that helps shield the vehicle in re-entry. Interesting!

[edzieba]

The description of a second stage nozzle design that "achieves high area ratio gas expansion within a form factor ten times shorter than traditional bell nozzles" and "[accommodates] deep throttle operation in the presence of atmospheric pressure" that "integrated into the vehicle base, the engine nozzle serves as an actively cooled metallic heat shield" sounds very much like the old plug-nozzle/truncated-aerospike concept. A horizontal-flow/'tray' nozzle would fir the 1/10 length parameter, but as far as I am aware the horizontal flow concept has never existed outside of paper engines (unlike other aerospike designs).

[Asteroza]

To the untrained eye, is a potential advantage of a horizontal flow nozzle be that the combustion chamber could be fed rather directly by centrifugal turboumps mounted on the engine center?

[edzieba]

The description of a second stage nozzle design that "achieves high area ratio gas expansion within a form factor ten times shorter than traditional bell nozzles" and "[accommodates] deep throttle operation in the presence of atmospheric pressure" that "integrated into the vehicle base, the engine nozzle serves as an actively cooled metallic heat shield" sounds very much like the old plug-nozzle/truncated-aerospike concept. A horizontal-flow/'tray' nozzle would fir the 1/10 length parameter, but as far as I am aware the horizontal flow concept has never existed outside of paper engines (unlike other aerospike designs).

Their website is now online, and it is indeed a plug nozzle on their reusable second stage. Second stage is a big capsule (base diameter wider than booster) with the plug nozzle acting as the heatshield, and re-closeable fairings.
A twitter post also shows a hot-fire test of their engines, in what appears to be a fixed array:
https://twitter.com/stoke_space/status/1431009842630594561
A whiteboard visible in their promo video shows some sort of LH2 pump.

[vaporcobra]

Also some good views of standalone testing and sizing of the mystery engine from handling. Looks about the same size as Launcher's E-1 and is definitely also fully or mostly 3D-printed - probably out of a copper alloy, too.

S2 also looks to be ~12-15 ft wide at its base. If it's using a plug aerospike design and Stoke is aiming for something similar to Firefly's original Alpha S1 with a bunch of really small engines clustered around a plug, Stoke could fit like 50-60 of those small hydrolox (?) engines in a circle, which would actually result in a fairly substantial 50+ ton-thrust upper stage just assuming that that engine is in the ~5 kN range.

Edit: Should add that the curious triple-engine test almost makes me think that the goal is to have just one or a few large staged combustion pumps (presumably derived or taken from the mystery S1 engines but maybe not) power dozens of plug nozzles. Not sure why else they'd do a test like that with engines without powerpacks.

[JEF_300]

These guys are super cool. Their CEO was one of the people working on BE-4 from the beginning apparently, and their whole team is made up of former SpaceX and Blue Origin employees, and just looking at the images (sketches really) that we have of their rocket, you can see the influence of both companies.

There's a video on the front page of their site which basically introduces them, and is worth watching, so I'll link it again: https://www.stokespace.com

There is also an interview between one of the initial investors and the CEO:

[JEF_300]

That white board image does list "GH2" and "LH2" on it, which not only basically confirms that we're talking about hydrolox here, but also suggests that those little engines will be expander-cycle engines. Or GH2 could be a simplification for the gas mixture that comes out of the fuel preburner, but I doubt that. Trying to discern exactly what combustion cycle is depicted in the diagram on that white board is mostly hopeless, but it looks to me mostly like a pretty bog-standard, RL-10 style Closed Expander, that is neither Dual nor Split.

On twitter, when they posted that image of the test firing, they claimed that it was the highest performance engine in small launch. If they were measuring by specific impulse, the use of hydrogen alone would make that true. If they were referring to TWR, then that's very impressive; and it would need to be impressive on it's own, because it won't be impressive when they're all attached to a big, heavy plug nozzle.

[edzieba]

Also, the lower half of that diagram could be depicting a pintle injector.

[JEF_300]

Another image of what appears to be that same set of test engines on the stand. They seems to have cleaned up the mixture ratio, because the exhaust is a lot cleaner.

EDIT: Also, is it just me, or is there a little blue plume to one side of each of the main plumes? Turbine Gas?

[russianhalo117]

Another image of what appears to be that same set of test engines on the stand. They seems to have cleaned up the mixture ratio, because the exhaust is a lot cleaner.

EDIT: Also, is it just me, or is there a little blue plume to one side of each of the main plumes? Turbine Gas?

Interaction with the water film cooling and metal reflection below the exhaust. All three appear different for POV camera angle. This is only an initial response aas I need more time to analyse. It is possible that individual injectors can create the effect.

[Blackjax]

Cross posting from the general thread.

Stoke are starting with reuseable 2nd stage then booster. Strange way of doing things for startup. Better to build booster first along with low cost expendable 2nd stage and start earning money, then tackle more difficult reuseable 2nd stage. While recovering 2nd stage is quite feasible the issue is more what is payload hit and cost of turning stage around.

https://www.geekwire.com/2021/breakthrough-energy-ventures-leads-65m-funding-round-for-stoke-spaces-reusable-rocket-stages/

They hadn't really been on my radar until now, but this is a non-trivial amount of money.  Not enough to field a full vehicle IMHO but perhaps enough to give us an idea of whether they can build a solid set of engines a vehicle might be built around.

[whitelancer64]

Stoke Space raises $65 million for reusable launch vehicle development

https://spacenews.com/stoke-space-raises-65-million-for-reusable-launch-vehicle-development/

[M.E.T.]

Stoke Space raises $65 million for reusable launch vehicle development

https://spacenews.com/stoke-space-raises-65-million-for-reusable-launch-vehicle-development/

Another one🙄

[su27k]

Stoke are starting with reuseable 2nd stage then booster. Strange way of doing things for startup. Better to build booster first along with low cost expendable 2nd stage and start earning money, then tackle more difficult reuseable 2nd stage. While recovering 2nd stage is quite feasible the issue is more what is payload hit and cost of turning stage around.

https://www.geekwire.com/2021/breakthrough-energy-ventures-leads-65m-funding-round-for-stoke-spaces-reusable-rocket-stages/

It is how Starship - the only fully reusable LV in development - is being developed, so in retrospect not that strange. The article says "Stoke previously won Small Business Innovation Research awards from NASA and the National Science Foundation for a “novel rocket engine configuration” intended for upper stages and planetary landers", so they could be thinking flying the 2nd stage as spacecraft or lander on other LVs first.

[Robotbeat]

Stoke Space raises $65 million for reusable launch vehicle development

https://spacenews.com/stoke-space-raises-65-million-for-reusable-launch-vehicle-development/

Another one🙄

Starting with upper stage reuse.

No one else is doing that right now except SpaceX, although Relativity has announced plans and Blue and Rocketlab are likely to eventually go there.

I think it’s appropriate.

[Hug]

Stuff from their first investor presentation.
https://twitter.com/jenekuns/status/1457849962692165635

[Blackjax]

So they are basically aspiring to compete with Rocketlab Neutron and both of them are attempting to leapfrog Firefly, ABL, and Relativity with a next generation approach to launch cost and operations.

[PM3]

So they are basically aspiring to compete with Rocketlab Neutron and both of them are attempting to leapfrog Firefly, ABL, and Relativity with a next generation approach to launch cost and operations.

Neutron is a different animal, not fully reusable and much larger.

iRocket Shockwave is similar to Stoke - fully reusable, 1500 kg to LEO. Founded two years earlier, should be some steps ahead.

[Blackjax]

So they are basically aspiring to compete with Rocketlab Neutron and both of them are attempting to leapfrog Firefly, ABL, and Relativity with a next generation approach to launch cost and operations.

Neutron is a different animal, not fully reusable and much larger.

iRocket Shockwave is similar to Stoke - fully reusable, 1500 kg to LEO. Founded two years earlier, should be some steps ahead.

Fair point on the size difference but that said it'll ultimately come down to a question of how many acrtual payloads in the Neutrons addressable market that these smaller vehicles could handle lofting and compete for.

I had a quick look at the iRocket website and didnt see anything obvious about the size of their funding.  How much competition there is depends on how likely either company is to have enough funding to get a vehicle into commercial operation.  Any idea how much funding they have compared to Stokes?  Closest I could find was a vague mention:

https://forum.nasaspaceflight.com/index.php?topic=51430.msg2307217#msg2307217

[GreenShrike]

So they are basically aspiring to compete with Rocketlab Neutron and both of them are attempting to leapfrog Firefly, ABL, and Relativity with a next generation approach to launch cost and operations.

Neutron, if it goes fully reusable, will most likely need a respin of its booster. Stoke, by going fully reusbale first, saves a bunch of money and time that would otherwise be wasted on an expendable upper stage and the booster tailored to it. (Though, in SpaceX's view, that doesn't count as waste, that counts as "experience". Of course, SpaceX has a lot more money to throw around, so....)

If the cards fall right, they may have a light-class fully reusable launcher in the same time frame as Rocket Lab and Firefly have partially reusable medium launchers, or a while longer when Relativity has a fully reusable medium/intermediate.

It's a gamble, but when you're so far behind, I guess you may as well try taking a shortcut.

The upper-stage-as-a-capsule design looks neat, as is using the annular aerospike as a heat shield. Maybe bleed hydrogen through the spike's cooling channels and out the aerospike to provide a cooling buffer? All that hydrogen is obviously going to be bulky, though.

If they have multiple combustors for the spike, perhaps they can get to an appropriate landing thrust by only running a subset of them?




Attaching archival copies of the investor presentation pics.