The Blue Origin BE-4 might get certified for flight tests by December of this year. It is about 5-6 years late for an original 2017 planned operational date. The BE-4 engine project started in 2014. It would be the most powerful liquefied natural gas (LNG) fueled rocket engine ever developed. Using an oxygen-rich staged combustion cycle, BE-4 is capable of producing 2,400 kN (550,000 lbf) thrust with deep throttle capability. The ULA (United Launch Alliance) Vulcan rocket plans to use the BE-4 engine and Blue Origin has designed a Falcon Heavy class New Glenn rocket to use BE-4 engines.
ULA said the Vulcan program “is now focused on completing BE-4 qualification testing and flight engine deliveries. [Its] other elements are progressing through final qualification testing to support initial launch capability.”
Before it can gain flight certification, ULA must complete two successful flight tests. Then, it will be greenlit to launch sensitive U.S. military and intelligence cargo.
The U.S. Space Force said it expects to complete initial certification of the Vulcan rocket with the BE-4 engine by March 2023. However, final certification for the “largest and most stressing” national security missions isn’t expected until 2025.
Elon Musk’s SpaceX, meanwhile, was recently awarded final certifications to fly its Falcon Heavy rocket to launch the same types of sensitive classified missions ULA aims to launch with Vulcan.
They chose LNG because it is highly efficient, low cost and widely available. Unlike kerosene, LNG can be used to self-pressurize its tank. Known as autogenous repressurization, this eliminates the need for costly and complex systems that draw on Earth’s scarce helium reserves. LNG also possesses clean combustion characteristics even at low throttle, simplifying engine reuse compared to kerosene fuels.
BE-4 was designed from the beginning to be a medium-performing version of a high-performance architecture. It’s a conscious design choice made to lower development risk while meeting performance, schedule and reusability requirements. With our hardware-rich approach, multiple developmental units and redundant test stands enable a high test tempo and rapid learning.
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6 thoughts on “Blue Origin Nears Flight Test Certification for BE-4 Rocket Engine”
The basic problem for the BE-4 is that it achieves slightly more thrust than the Raptor by being much larger, because it starts out with a substantially lower chamber pressure.
1,950 PSI chamber pressure,
550,000 lb thrust,
72″ engine diameter
5 degree gymbal.
80-1 thrust to weight.
Raptor 2, by contrast,
15 degree gimbal.
140 thrust to weight
Throttle to 40%.
So it’s got a lot lower thrust to weight ratio, and you can pack in more thrust per square meter of rocket cross section.
So, at this point, the Raptor is absolutely the better engine, and it’s not even close.
Now, maybe BO can upgrade it to beat the Raptor 2 on those key metrics, but by then?
Raptor 3, or maybe 4.
One more spec that probably matters, SpaceX is already well into the struggle to mass produce Raptor 2 and get the price per engine into the several $100k range vs the $10M+ range for BE4.
Raptor is a better engine that costs a tiny fraction as much.
And, really, the thrust is close enough that in the end they’d probably be better off just using the Raptor even on the Vulcan; The Vulcan plans to use 2 BE-4 engines, but you could easily fit 3 Raptor 2’s on it, for more total thrust.
To amplify, thrust to weight is REALLY important on first stages, and somewhat so afterwards. On the first stage, every ounce of dry weight of the rocket is an ounce of engine thrust that’s wasted on nothing but hoovering in place. It’s the thrust in excess of weight that does all the work.
So the fact that the Raptor has nearly twice the thrust to weight ratio, by itself, is important.
Then you add that they’re smaller, so you can pack more engines in the same size rocket, and you can take off with a lot higher acceleration. And, again, only the acceleration in excess of 1 g is doing any work, so you’re using the thrust more efficiently with Raptor engines. Yeah, this likely means you’ll hit max Q faster, but as the air thins out you regain that advantage.
And even once you’re in zero G, when there isn’t that wasted thrust, you still don’t want to be carrying around any more engine weight than you have to, to get the job done.
Then there’s that slightly higher gymbal angle, that gives the engines more control authority. Especially since the smaller engine can be further from the center and not protrude. So a rocket relying on Raptors will be more nimble, less likely to end up outside its control envelope.
All around it’s just a better engine than the BE-4. With enormously more real world experience accumulating.
Other important point:
Starship booster will have 33 Raptors, instead of 7 BE4s
I’ll believe it when I see it. I’d love to be proven wrong, though.
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