BE-3 uses a tab-off cycle (the turbine is run with hot gases tapped off from the main combustion chamber). BE-3U -which is meant for New Glenn, uses an expander cycle (heated gaseous fuel from engine's cooling lines powers the turbine). BE-3U is practically new engine design.
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Thanks for your correction, I forgot that microgravity would persist after apogee.
5 minutes of microgravity: okay, that’s it, sign me up!
In reality, the Vomit Comet is likely the only microgravity I’ll ever experience. It’s on my Bucket LIst.
5 minutes of microgravity: okay, that’s it, sign me up!
In reality, the Vomit Comet is likely the only microgravity I’ll ever experience. It’s on my Bucket LIst.
You missed the step where the capsule smacks into the top of the atmosphere somewhere before its maximum velocity. At 6:15 the booster is already experiencing 1 gee, 2500 mph, 70,000 ft. It slow down quickly thereafter. The capsule is certainly decelerating strongly by this time since it is much less aerodynamic than the booster.
When they switch back to the capsule at 7:49 it's already decelerated to terminal velocity -- 237 mph. Drogues don't come out until 8:17.
They should be back in their seats by about 5:20. Around 5:30 you start getting meaningful aerodynamic drag. Wedge fins deployed around 5:35, and at around the same time you start seeing the booster pull away from the capsule (due to the capsule having greater drag per kg).
So between approximately between 2:40 and 5:20 they can move around. 2 minutes and 40 seconds, basically.
So between approximately between 2:40 and 5:20 they can move around. 2 minutes and 40 seconds, basically.
Nikxice
Active Member
BO is counting down this morning for their next (groundhog day Jeff?) New Shepard launch. About 10:30 am EDT. Fun to watch, but better with the sound off. The usual BO play by play announcer always comes off a little over the top.
Blue Origin
Blue Origin
Their booster hovers quite a bit before landing, I wonder if that decreases damage to the booster and why Spacex doesn't hover their boosters before landing?
New Shepherd is a sub orbital vehicle with far less mission requirements. It is almost a toy in comparison to a falcon 9. The Falcon 9 needs to conserve as much propellant as possible since it is running close to the design limits of what it can achieve. There are some missions where they simply can’t return the booster because the mission requires too much fuel for the primary mission. So the Falcon 9 doesn’t waste any fuel because it can’t afford to.
If you watch an F9 RTLS landing video you will note that in the final half second before touchdown the booster is barely moving. I can see no utility to decreasing the landing speed to an even lower value.
And what @Cosmacelf said.
The minimum thrust of one Falcon 9 engine is greater than the weight of the landing F9 first stage, so they cannot hover. They must instead get velocity to equal zero at the same moment when the height equals zero.
(at least that was true on previous engines, maybe block 5 can throttle back more)
Was about to say the same thing, and it's still true, as far as I can determine. A single Merlin at 40% output still has around 38.4 metric tons of thrust, while an empty Falcon 9 first stage weighs something like 22 metric tons.
Also the reason provided by Cosmacelf holds true. For maximum fuel efficiency, you want to wait as long as possible before initiating the landing burn, meaning you want to pull as many Gs as possible in the landing burn, and then perfectly have speed and height be zero at the same time. This allows the atmosphere to do as much braking as possible, and decreases the time you are working against gravity.
This is why some Falcon 9 landing burns use three Merlins - means they have very little fuel left over for landing.
This is why some Falcon 9 landing burns use three Merlins - means they have very little fuel left over for landing.
I doubt that New Glenn will be able to hover though they do suggest it will do so in their video. I expect it will have the same issue as F9: too much power. The BE-4 is a big engine. It would probably need a huge number like 90% throttling capability to be able to hover. 90% is a crazy number to pull off with an orbital class rocket engine.
At 10% output, would it also run into the issue of the exhaust (at the exit of the bell) being below ambient pressure?
Worse than that. Even a single Merlin, throttled back as far as it can be, generates more thrust than the weight of the almost-empty F9 booster. So it literally can't hover. It has to decelerate to zero-zero (close, anyway) then shut down to land. This used to be referred to as "hover-slam", IIRC.
Nikxice
Active Member
Barely a news blip, on Wednesday more Deja Vu all over again for Jeff and the gang at BO. The New Shepard launch starts at the 40:00 minute mark. It almost seems that Jeff and Sir Richard are in a race to the bottom to be the last space company to fly passengers sub-orbital.
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