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#20
by
Steven Pietrobon
on 06 Aug, 2019 22:41
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The easy part is aerocapture.
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#21
by
Helodriver
on 06 Aug, 2019 22:46
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Very much like what Hiller Aviation proposed to do with Saturn S1C stages.
Dwayne Day of The Space Review just published a nice article on that program.
At least they will not need the worlds largest helicopter to attempt this.
Will be interesting maintaining orientation and structural integrity with no active guidance system or retrofirings.
F1 and early F9 couldn't do it.
http://www.thespacereview.com/article/1045/1
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#22
by
Steven Pietrobon
on 06 Aug, 2019 22:55
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Some slides I didn't have time to post before. Re-entry of the Electron first stage needs to dissipate 3.5 GJ of energy.
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#23
by
Steven Pietrobon
on 06 Aug, 2019 22:58
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Rocketlab are using the same aerocapture method as shown in this video from 2017. Just noticed their animation copied the sequences shown!
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#24
by
butters
on 06 Aug, 2019 23:09
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I don't see why not. They have more performance margin than their competitors, and as SpaceX showed, they can try and try again without impacting their customers. If they can get through reentry, the helicopter recovery shouldn't be prohibitively difficult on the scale of Electron, and if they can't, they're still in a good position in their market segment.
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#25
by
FutureSpaceTourist
on 06 Aug, 2019 23:21
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#26
by
M.E.T.
on 06 Aug, 2019 23:42
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Am I correct in saying the mass of any parachutes, grid fins or reserve fuel will have to come out of their 225kg payload budget?
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#27
by
JEF_300
on 06 Aug, 2019 23:50
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Am I correct in saying the mass of any parachutes, grid fins or reserve fuel will have to come out of their 225kg payload budget?
Yes, but note that that equipment will be coming with a "block upgrade" to the Electron first stage. There will probably (pure speculation) also be some overall upgrades happening; reducing margins, uprating the engines, etc.
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#28
by
Asteroza
on 06 Aug, 2019 23:57
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Am I correct in saying the mass of any parachutes, grid fins or reserve fuel will have to come out of their 225kg payload budget?
Yes, but note that that equipment will be coming with a "block upgrade" to the Electron first stage. There will probably (pure speculation) also be some overall upgrades happening; reducing margins, uprating the engines, etc.
Considering the pace of battery power/density improvements shrink the size/mass of the battery packs, and Flight 10 will introduce a stage 1 block upgrade which will either shave more weight/stretch the tanks a bit/maybe a rutherford improvement, they may have bought back some performance/mass that will be used for the recovery systems. Tank stretch is easiest, but fineness ratio may be problematic.
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#29
by
Lars-J
on 06 Aug, 2019 23:59
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Am I correct in saying the mass of any parachutes, grid fins or reserve fuel will have to come out of their 225kg payload budget?
Yes, but only a fraction of it applies to the final payload, since it is only on the first stage. I seem to recall that for F9, the LEO payload hit was ~10% of first stage added mass. So 500kg of added recovery hardware mass will only subtract 50kg from the LEO payload. And it sounds like a first stage block upgrade will compensate for that.
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#30
by
gin455res
on 07 Aug, 2019 00:30
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Anyone care to guess how the mass/frontal-area on re-entry for electron compares to an F9 and whether this enables much higher altitude braking?
And would it be worth hot swapping on the first stage to maximise fluffiness further?
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#31
by
ArbitraryConstant
on 07 Aug, 2019 00:34
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Am I correct in saying the mass of any parachutes, grid fins or reserve fuel will have to come out of their 225kg payload budget?
I think the exchange rate is about 7 kg on the first stage costs about 1 kg on the upper stage/payload.
Didn't Beck say they were at or near their 100th engine? No way they've built that many engines without improvements. And they get battery improvements for free. Seems entirely possible cumulative improvements from that stuff have already made up the penalty from recovery hardware and they made the decision to do recovery with the mass margin that creates (though presumably like SpaceX, some flights would be expendable).
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#32
by
ArbitraryConstant
on 07 Aug, 2019 01:01
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Anyone care to guess how the mass/frontal-area on re-entry for electron compares to an F9 and whether this enables much higher altitude braking?
I get about 2585 kg/m2 for Falcon 9 and about 673 kg/m2 for Electron. They seem to stage at close to the same speed. I'm not sure about the math to calculate peak heating or peak deceleration but it does sound like they have less kinetic energy to scrub off per area, that must be easier.
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#33
by
Steven Pietrobon
on 07 Aug, 2019 01:03
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One way Rocketlab could easily increase performance is to use subcooled propellants, just like SpaceX did with Falcon 9. Perhaps that is one the major updates in the block upgrade.
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#34
by
gin455res
on 07 Aug, 2019 01:04
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Anyone care to guess how the mass/frontal-area on re-entry for electron compares to an F9 and whether this enables much higher altitude braking?
I get about 2585 kg/m2 for Falcon 9 and about 673 kg/m2 for Electron. They seem to stage at close to the same speed. I'm not sure about the math to calculate peak heating or peak deceleration but it does sound like they have less kinetic energy to scrub off per area, that must be easier.
And if you eject the entire battery after staging?
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#35
by
ArbitraryConstant
on 07 Aug, 2019 01:23
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And if you eject the entire battery after staging?
I have no idea of the battery mass.
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#36
by
Lar
on 07 Aug, 2019 02:16
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And if you eject the entire battery after staging?
I have no idea of the battery mass.
Also if you eject too many things, you aren't left with much to reuse. You could eject the engines, which clearly would make the remaining part fluffier... not a good idea.
Batteries are (relatively) cheap though..
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#37
by
JEF_300
on 07 Aug, 2019 02:27
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And if you eject the entire battery after staging?
I have no idea of the battery mass.
Also if you eject too many things, you aren't left with much to reuse. You could eject the engines, which clearly would make the remaining part fluffier... not a good idea.
Batteries are (relatively) cheap though..
Electron is relatively cheap.
Beck said something to the effect of 'put it back on the pad, charge it up, and launch it', so I fully expect them to reuse the batteries.
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#38
by
Norm38
on 07 Aug, 2019 02:38
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This will be fun to watch. F9 couldn't survive reentry without a braking burn and kept breaking up. So it's going to be challenging for Electron to hold together with only passive tech. But it is much smaller than F9, so that should help.
I'd forgotten that SpaceX tried to parachute F1 also. But Rocket Lab has the benefit of watching F9 re-entries, and they will also be collecting massive amounts of data on their future launches. Something SpaceX never got to do with F1.
I wish them the best of luck.
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#39
by
Comga
on 07 Aug, 2019 03:20
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The easy part is aerocapture.
No
It’s not
😳
Beck is not showing whatever “magic sauce” they have come up with to orient the stage and protect it from the hypersonic thermal and mechanical loads.
Notice that between staging and reentry the first stage has shifted unseen from top forward to engines forward.
He says they will solve these issues “differently”.
This can only refer to SpaceX’s cold gas thrusters, grid fins, and entry burns.
It seems apparent that they don’t have the mass margin for more than, or even, one of those subsystems in addition to the parasail.
Edit: unless that’s a joke and “aerocapture” includes shredding as long as none of the pieces escape Earth