On Tuesday, Stoke Space announced the firing of its first stage rocket engine for the first time earlier this month, briefly igniting it for about two seconds. The company declared the June 5 test a success because the engine performed nominally and will be fired up again soon.

"Data point one is that the engine is still there," said Andy Lapsa, chief executive of the Washington-based launch company, in an interview with Ars.

The test took place at the company's facilities in Moses Lake, Washington. Seven of these methane-fueled engines, each intended to have a thrust of 100,000 pounds of force, will power the company's Nova rocket. This launch vehicle will have a lift capacity of about 5 metric tons to orbit. //

Lapsa and Stoke, which now has 125 employees, have also gone for an ambitious design in the first-stage engine tested earlier this month. The engine, with a placeholder name of S1E, is based on full-flow, stage-combustion technology in which the liquid propellants are burned in the engine's pre-burners. Because of this, they arrive in the engine's combustion chamber in fully gaseous form, leading to a more efficient mixing.

Such an engine—this technology has only previously been demonstrated in flight by SpaceX's Raptor engine, on the Starship rocket—is more efficient and should theoretically extend turbine life. But it is also technically demanding to develop, and among the most complex engine designs for a rocket company to begin with. This is not rocket science. It's exceptionally hard rocket science. //

Dtiffster Ars Praefectus
8y
3,002
Subscriptor

deadman12-4 said:
How is a big bulky weight penalty on your second stage good for reuse?

The extra drymass that come from the low density hydrolox is partially mitigated by it's Isp. If the upper stage was expendable, the more than double the volume (and thus likely cost) would be a bad tradeoff for what is close to a push in performance for payload to LEO. But as a reusable upper, hydrogens much better heat of vaporization vs methane and the really low ballistic coefficient are definitely big wins. The low ballistic coefficient combined with lift from their asymmetric design means they can shed velocity very high in the atmosphere where they can reradiate a lot of it back into space. And then when they get lower they use the excellent heat carrying capacity of the hydrogen to protect them from high heat fluxes. From an integrated system perspective, the trades start to make a lot of sense. //

greybeardengineer Ars Tribunus Militum
5y
12,948

Malmesbury said:
Seems like yesterday that Henry Spencer was telling us (and we all agreed) that developing new rocket engines for new launchers was a terrible idea. It would always cost billions. Even warming over old engines was fraught.

And it seemed to be true - see the J2-X comedy.

And no one could match the Russian engines from the Forgotten Years.

Now we have slack handfuls of rocket nerds creating orbital class FFSC engines.

That, right there, is New Space

Once a leadership company achieves something new and very difficult it does two important things: 1) it tells entrepreneurs and investors that it can be done, and 2) a cadre of engineers and managers is created familiar with the technology who are free to move on and disseminate the general understanding of the new technology elsewhere.

As someone once said the greatest secret of the atomic bomb was that it can be built and that it works. Same goes for ORSC. :sneaky: //

That, right there, is New Space

It's quite an accomplishment to blow past the performance of the Soviet/Russian/Ukrainian ORSC engine designs. //

jandrese Ars Legatus Legionis
22y
12,795
Subscriptor++

Bad Monkey! said:
This is amusing considering how long it took BO to get a not terribly ambitious staged combustion engine into production, yet Stoke is all of four years old. Did BO lose all the good ones to Stoke?

Blue Origin is run like an old Aerospace company, which is more risk adverse and slow to develop. Rockets are hard, and being able to prototype designs and work out problems is an enormous productivity boost. Years and years of experience shows that trying to do everything on paper first before building the rocket results in very slow and expensive development. Building engines and blowing up your first half dozen is much faster and cheaper and leads to a better product in the end. //

Wickwick Ars Legatus Legionis
14y
34,700

deadman12-4 said:
How does resources matter. We are talking about a 50 year improvement in technology. This has nothing to do with it being a "commercial" company. Look at China - it'd be embarrassing for them if their engines also didn't blow away old soviet stuff.

I'm not saying "soviet stuff is bad cause its soviet", we need to realize its 50 year old tech. Worshiping it is silly. Everyone should be able to do better than 50 yr old tech, no matter who made it. Its strange how soviet tech is a sacred cow. Its just tech made by someone like anything else. It was good for its time, but that was half a century ago.

You seem to think that "technology" improving just makes everything easier. Sometimes, someone's expertise matters more than technology.

Pratt & Whitney actually had a license to manufacture the RD-180 engine domestically. They literally had the blueprints and everything they needed to know on the metallurgical side to make it happen. They eventually chose not to execute on the license because just duplicating the Russian/Ukrainian design was sufficiently outside of the capabilities of P&W that they felt they would never be cost competitive with the price ULA could buy the engines as imports - duties and all. And lest you think P&W were just a bunch of schleps, they were the makers of the RL-10 engine.

So it's not just a 50 year-old technology. Less than 20 years ago, one of the premier rocket engine manufacturers in the US couldn't make it work even with the recipe. //

I Like Pi Seniorius Lurkius
16y
23

deadman12-4 said:
) How is a big bulky weight penalty on your second stage good for reuse?

Um…you get the stage back… //

Malmesbury Smack-Fu Master, in training
1m
91

deadman12-4 said:
hmm... I would disagree at this point. We're talking about 1970s tech. Yes they were amazing for time, but their time was like 2 generations ago. They are only still relevant because so few engines have been made and used in the last 50 years.
I would say it would be embarrassing if a company couldn't blow past the benchmarks of soviet engines today.

Not long ago, the Received Wisdom from professionals in the industry was that only incremental improvements on existing engines were worthwhile. And possible.

Now, everyone and his dog is building new engines. Using cycles that the pros said they couldn’t do. //

greybeardengineer Ars Tribunus Militum
5y
12,948
Just to be clear, this Stoke first stage engine is methalox. They use hydrolox for their second stage. The article doesn't make that clear and it appears that some in the comments don't realize this. //

phat_tony Ars Centurion
18y
291
Subscriptor

Joey S-IVB said:
445 kilonewtons for each engine, or 3.1 meganewtons for all seven engines combined on the first stage. That's under half of the Falcon 9's approximately 6.9 meganewtons. So, if it can put 5 tonnes into LEO, I'm guessing the second stage isn't as powerful/efficient as the F9's second stage? If this first stage is roughly half as powerful as the F9's booster stage, it is putting less than half the tonnage in comparison (should be about 8.5 tonnes to LEO if half). Still, it's great to see that Stoke is making rapid progress.

Others have pointed out the reusable second stage adds mass vs expendable; but furthermore, you just shouldn't expect rockets to scale linearly at all. Other things being equal, the larger the rocket, the higher percentage of the rocket's total launch mass can be payload.

The SS-520 is the smallest orbital rocket and it's 5,700 lbs and the mass to orbit is effectively 0 - it's 9 lbs. Any smaller and the rocket could not even get itself to orbit.

Some things on the rocket don't scale - the avionics and sensors for a tiny rocket and Starship aren't necessarily very different, so there's a flat mass you need to take. But the most important thing in rocket scaling is that the volume of a fuel tank goes up faster than the surface area when you make it bigger, keeping all proportions identical. The bigger the tank, the lower the ratio of tank mass to fuel mass.