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#1140
by
Phil Stooke
on 21 Jan, 2018 02:34
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Found the perfect way to celebrate Electron launches from Mahia:
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#1141
by
Comga
on 21 Jan, 2018 05:04
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It had a seemingly high TWR on liftoff, and I heard the first stage engines aren't even at their full thrust.
Is there a possibility of lengthening the stage(s?), similar to the Falcon 9 1.1 vs 1.0?
With values from Rocketlabs & SpaceX, Electron, at 1.2 m dia & 17 m long has 75% the fineness of the 3.7 m dia by 70 m long Falcon 9.
In theory Electron could be stretched by an additional third, 5.7 m, before matching SpaceX's high fineness.
We shall see if they ever try stretching it.
As batteries and electric pumps improve with time, I wouldn’t be surprised to see some growth.
PS. Wow! Was that ever a clean launch!
Straight as an arrow and smooth.
The biggest fluctuations were video compression artfacts in the otherwise very stable exhaust.
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#1142
by
TrevorMonty
on 21 Jan, 2018 06:12
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Was the upper-stage 'hot swap' switching from one battery to another, then dumping the expended battery? Photos of the stage show nothing, but renders show two modules that could be battery packs and are in the right location to be visible on the stream.
Yup.
I remember the dropping of battery packs being discussed on this forum at one tome. Nice to see our ideas were validated.
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#1143
by
ringsider
on 21 Jan, 2018 06:23
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Watching the S2 burn, about 25 mins into the video, I think they hot-swapped batteries and then eject used battery packs, which is a unique feature of Electron.
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#1144
by
Kosmos2001
on 21 Jan, 2018 10:02
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Watching the S2 burn, about 25 mins into the video, I think they hot-swapped batteries and then eject used battery packs, which is a unique feature of Electron.
I also realised when they dropped them. It is a clever way to get rid of ballast.
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#1145
by
gin455res
on 21 Jan, 2018 11:01
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I wonder, if there was an electron tri-core with electrical cross-feed, and if there were bigger batteries in the side cores (with enough juice to run the central core until staging), if the reduction in the weight of the battery in the central core would give worthwhile improvements in performance?
The limitation with the batteries is how fast they can be discharged, which is about 2 to 3 minutes at best. So having the boosters supply charge to the core may not be an advantage, if the batteries in the core can then not be fully discharged.
Does 'hot-swapping' suggest that this might be feasible? However, unless the core is going to orbit, then maybe not worthwhile.
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#1146
by
gin455res
on 21 Jan, 2018 11:40
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Anyone know how the electric engines affect the vibration loads on the payload?
Can pogo and feed pressure variations be more quickly damped out with electric motors?
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#1147
by
Katana
on 21 Jan, 2018 12:02
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It had a seemingly high TWR on liftoff, and I heard the first stage engines aren't even at their full thrust.
Is there a possibility of lengthening the stage(s?), similar to the Falcon 9 1.1 vs 1.0?
With values from Rocketlabs & SpaceX, Electron, at 1.2 m dia & 17 m long has 75% the fineness of the 3.7 m dia by 70 m long Falcon 9.
In theory Electron could be stretched by an additional third, 5.7 m, before matching SpaceX's high fineness.
We shall see if they ever try stretching it.
As batteries and electric pumps improve with time, I wouldn’t be surprised to see some growth.
PS. Wow! Was that ever a clean launch!
Straight as an arrow and smooth.
The biggest fluctuations were video compression artfacts in the otherwise very stable exhaust.
Perfect the state of art
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#1148
by
Katana
on 21 Jan, 2018 12:05
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I wonder, if there was an electron tri-core with electrical cross-feed, and if there were bigger batteries in the side cores (with enough juice to run the central core until staging), if the reduction in the weight of the battery in the central core would give worthwhile improvements in performance?
The limitation with the batteries is how fast they can be discharged, which is about 2 to 3 minutes at best. So having the boosters supply charge to the core may not be an advantage, if the batteries in the core can then not be fully discharged.
Some hobby RC batteries could be discharged at 70C = 51 seconds
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#1149
by
Katana
on 21 Jan, 2018 12:08
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It had a seemingly high TWR on liftoff, and I heard the first stage engines aren't even at their full thrust. Is there a possibility of lengthening the stage(s?), similar to the Falcon 9 1.1 vs 1.0?
High TWR at liftoff then thottle down may improve overall performance regarding gravity loss and battery weight.
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#1150
by
speedevil
on 21 Jan, 2018 12:25
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It had a seemingly high TWR on liftoff, and I heard the first stage engines aren't even at their full thrust. Is there a possibility of lengthening the stage(s?), similar to the Falcon 9 1.1 vs 1.0?
High TWR at liftoff then thottle down may improve overall performance regarding gravity loss and battery weight.
For small launchers, drag is _BAD_ as you get towards transonic, and you really want to move max Q higher in the atmosphere, as eating ten seconds of gravity loss while you coast upwards at 300m/s may use lots less fuel than trying to bull through.
Electron is almost big enough that this is less of a concern.
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#1151
by
Ronsmytheiii
on 21 Jan, 2018 14:47
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Pretty nifty design but there is probably limited growth margin until there are higher density battery packs. Still an amazing job on their part.
Or they switch over to advanced capacitors, especially if they jettison them like the battery packs currently.
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#1152
by
rashomon
on 21 Jan, 2018 14:57
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I wonder, if there was an electron tri-core with electrical cross-feed, and if there were bigger batteries in the side cores (with enough juice to run the central core until staging), if the reduction in the weight of the battery in the central core would give worthwhile improvements in performance?
The limitation with the batteries is how fast they can be discharged, which is about 2 to 3 minutes at best. So having the boosters supply charge to the core may not be an advantage, if the batteries in the core can then not be fully discharged.
Some hobby RC batteries could be discharged at 70C = 51 seconds
F1 electric assist/kinetic-energy-recovery-system (KERS) batteries can be discharged at 200C, or fully discharged in less than 18 seconds. Energy density is low, however, and they need to be pre-heated to achieve those rates.
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#1153
by
mme
on 21 Jan, 2018 17:10
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It had a seemingly high TWR on liftoff, and I heard the first stage engines aren't even at their full thrust. Is there a possibility of lengthening the stage(s?), similar to the Falcon 9 1.1 vs 1.0?
High TWR at liftoff then thottle down may improve overall performance regarding gravity loss and battery weight.
For small launchers, drag is _BAD_ as you get towards transonic, and you really want to move max Q higher in the atmosphere, as eating ten seconds of gravity loss while you coast upwards at 300m/s may use lots less fuel than trying to bull through.
Electron is almost big enough that this is less of a concern.
It looked to me like the trajectory was much more vertical than I'm used to until after stage 1 separation. I assumed it was an illusion but maybe they really did fly lofted to move max Q?
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#1154
by
john smith 19
on 21 Jan, 2018 18:21
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Anyone know how the electric engines affect the vibration loads on the payload?
Can pogo and feed pressure variations be more quickly damped out with electric motors?
That is a good question. If it's lower it will be a distinct differentiator for Electron.
As to the answer...
Well it doesn't have a separate gas generator for each engine (or any engine). That eliminates a whole set of vibration sources due to combustion instability. It also eliminates the spinning mass of the drive turbines (but replaces them with the spinning rotor in the motor, which should be more stable).
The rest (feed system, engines) are close enough to normal systems that their vibration levels should be about the same.
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#1155
by
FutureSpaceTourist
on 21 Jan, 2018 18:39
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Some interesting observations of the launch by Ben Brockert:
These were my initial impressions from the Rocketlab launch video. Again, a huge accomplishment to make orbit on the second try, and I'm really glad they webcast the attempt.
A huge accomplishment, congrats to them. A few notes as an occasional liquid rocket engine guy:
* The upper stage exhaust was very sparky. That's usually only seen in solids, usually sparks in liquids means that some of the engine is eroding.
* The upper stage nozzle had big streaks on it. Suggests some asymmetric injector behavior, since
there's no gas generator exhaust injection (which causes the streaks on MVac)
* What was up with the big spiral in the exhaust? Wind shear?
* Staging looked amazing. No slosh sway like killed a Falcon 1 .
* Did they stage batteries on the upper stage? I can't think of what else they'd drop mid-burn. If you drop batteries does that make you two and a half stages?
* This launch was very very quickly after the last one, based on the historical launch program data l've compiled. Would be good to see them get two more off this year.
* How are they getting away with not painting the carbon fiber? Just limiting sun exposure as much as possible to get it dumped in the ocean before it can get enough UV damage to matter?
* They really leaned on the upper stage. Long into the second stage burn they called 3km/s, not even half way to orbit.
https://twitter.com/wikkit/status/955160356560674816
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#1156
by
QuantumG
on 21 Jan, 2018 20:29
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If you drop batteries does that make you two and a half stages?
During the callouts at launch they do go/no go for stages 1, 2 and 3.
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#1157
by
BarryKirk
on 22 Jan, 2018 00:12
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Looking at this. I'm wondering at improvements that could be made.
Will Rocket Lab improve their rockets the way SpaceX has been doing. I know that there focus is on small sat launch. But as they gain experience, I would expect capacity and capabilities to creep up.
So...
1. Sub cool the propellants like Space X.
2. With two motors and two pumps, both electric, one has to ask, how difficult it would be to change to a different propellant?
Probably want to stick with KeroLox for the booster, at least initially, but how difficult would it be to change the US to Methalox?
3. Here is a crazy idea. Changing prop in the middle of the upper stage burn. So start the US on a methalox fuel, but when getting closer to orbit and gravity losses are getting small, switch over to hydralox.
Sure you lose thrust, but at that point in the burn, that doesn't matter if the ISP goes way up.
You would probably gain dry mass due to more complex tankage and extra piping though. But the pump might not care about the fuel change.
This would probably really help out if your going to GEO or further out.
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#1158
by
TrevorMonty
on 22 Jan, 2018 01:58
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I expect they will stabilise design and concentrate on volume production and launch. There is still likely to be follow on LV in early stages of development.
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#1159
by
speedevil
on 22 Jan, 2018 06:24
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Pretty nifty design but there is probably limited growth margin until there are higher density battery packs. Still an amazing job on their part.
Or they switch over to advanced capacitors, especially if they jettison them like the battery packs currently.
Capacitors have abysmal energy per Kg, compared to batteries for discharges in the 1-5 minute range.
From memory, well under 2% - that is, you'd need 50kg for each 1kg of battery.