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On 5/12/2017 at 6:23 PM, Ultimate Steve said:

The Hype continues... Best of wishes to Rocket Lab and the X prize team flying on Electron!

Wait, what? How is anybody going to get anything to the surface of the Moon using Electron? To get from LEO to the surface of the Moon, you need 3.1 km/s for the transfer outwards, and then another 2.7 km/s (ish) for the braking burn. Electron can only launch 150 kg to LEO. Let's say that the rover we're trying to deliver weighs 10 kg (which, mind you, is lighter than Sojourner, the lightest rover ever deployed). That gives us 140 kg for the transfer vehicle. Now, it's safe to say this transfer vehicle will be using storable propellants, putting the vacuum Isp around 300s. Given this, the transfer stage's dry mass would have to be around 10 kg for the math to check out, resulting in a 14:1 wet mass/dry mass ratio for the transfer stage. Which is ridiculous, considering the scale.

Does anybody have any information on this? Because, as I see it, assuming my assumptions are reasonable, I don't see how it's possible to use Electron to complete the X prize.

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3 hours ago, IncongruousGoat said:

Does anybody have any information on this?

Moon Express has booked options for up to three launches to the Moon from Rocket Lab. They will be among the first customers - likely the second regular launch. The payload capability is "less than 10 kg", and Moon Express specifically downsized their lander to make it work. It's going to be tiny, and it's not going to be a rover. It'll try to complete the X-Prize's 500 meter travel goal via a propulsive hop.

(Source)

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Electrons 150kg is [email protected]

The website lists 225kg as max payload.

We should find out shortly if this is accurate.

 

The lander needs 300s storables only for LOI and the landing (~2700m/s).

For a final mass of 10kg, this will be a 25-30kg payload.

Do the TLI with 330s kerolox of the upper stage, similar to a GTO insertion.

So you are lifting a 13% of your max payload to LEO.

As long as you have >3100m/s left in the upperstage tanks for TLI, you are good to go.

 

*Nope. Got it wrong Red. 30kg aint goin to the moon on electron.

 

 

Edited by RedKraken
checked with Tsiolkovsky
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A quick check from the spreadsheet :

For electron to get 10kg TLI (~12300m/s)

from 9200kg kerolox @ 300s(atmos-ave) and 333s (vac)

the dry masses of the stages need to be something like 9% (1st) and 6%(2nd).

Less than 10kg TLI looks like a reasonable figure if the isps and dry masses match up.

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5 hours ago, RedKraken said:

Electrons 150kg is [email protected]

The website lists 225kg as max payload.

We should find out shortly if this is accurate.

 

The lander needs 300s storables only for LOI and the landing (~2700m/s).

For a final mass of 10kg, this will be a 25-30kg payload.

Do the TLI with 330s kerolox of the upper stage, similar to a GTO insertion.

So you are lifting a 13% of your max payload to LEO.

As long as you have >3100m/s left in the upperstage tanks for TLI, you are good to go.

 

*Nope. Got it wrong Red. 30kg aint goin to the moon on electron.

That makes more sense. For some reason I read "500 km SSO" as "500x500 km LEO", hence the mistaken assumption. That, and I thought that Moon Express's payload was a rover, and not (as @Streetwind pointed out) a tiny lander doing a propulsive hop.

And I thought I did my research. :P

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On 5/14/2017 at 2:43 PM, Steel said:

I'm not aware of any fuel cell designs using kersoene and/or oxygen. Also Even if there was I don't think you'd get anywhere near the power output required from one anyway.

It's all about the size - get the electrodes (and fuel flow) big enough and enough current shall pass, at the expense of low efficiency. (though you can't raise DC voltage...)

But alright, it's out of question.

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3 hours ago, YNM said:

It's all about the size - get the electrodes (and fuel flow) big enough and enough current shall pass, at the expense of low efficiency. (though you can't raise DC voltage...)

But alright, it's out of question.

You can raise DC voltage - all you need is a circuit known as a step up chopper. Granted the output quality is, umm, choppy, but that can be fixed with the same filtering that a rectifier output needs.

Also you can connect fuel cells in series just like regular batteries and raise the voltage that way. Of course fuel usage will increase consemmurately if the current stays the same.

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15 hours ago, monophonic said:

You can raise DC voltage - all you need is a circuit known as a step up chopper. Granted the output quality is, umm, choppy, but that can be fixed with the same filtering that a rectifier output needs.

Also you can connect fuel cells in series just like regular batteries and raise the voltage that way. Of course fuel usage will increase consemmurately if the current stays the same.

This is pretty much a standard circuit called a DC-DC converter (up or down).  Typically 80% efficiency, you can get a bit over 90% if your load is known (and constant) and you are willing to sweat a bit (pretty much mandatory for any space application).  The output isn't even all that choppy (assuming a less naive design) even before the capacitor filtering.  Look up the design of any switching power supply to get the basics.

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No webcast for this launch, but they say we'll get video after the fact.

Let's keep our fingers crossed for them anyway. SpaceX needed four tries to successfully orbit, one of which actually exploded shortly after launch. These guys can benefit from SpaceX's work and have a higher chance of getting it right the first time, but the learning curve will still be extremely steep. I'll give them a 50/50 chance of pulling it off.

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31 minutes ago, Streetwind said:

I'll give them a 50/50 chance of pulling it off.

I'd say you're being too optimistic.

Too many organisations with much better funding haven't managed to do it on their first try, I don't expect this one to.

I'll be thoroughy surprized and impressed if they do pull it off, though.

As for odds, I'd set them at:

60% RUD

20% failure to reach orbit due to underperformance

15% launch canceled

5% success

 

Neo : Okies dokie.

Neo : Free my mind... no problem.

Mouse : So what if he makes it?

Tank : No one's ever made the first jump...

Mouse : I know, I know...but what if he does?

Apoc : He won't.

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My odds projection, not counting postponement:

30% Explosion/RUD (Fuel tanks, pressurization gas, engines, batteries, or other.)

40% Success (Even partial. If it reaches orbit, it counts as success.) (Maybe slightly lower, I realize I'm being optimistic.)

20% Separation failure of some sort (Fairings, decoupler, ground clamps, etc.)

10% Other equipment failure (Communcation failure, Accelerometers installed upside-down, Ice on rocket leading to underperformance, etc.)

 

That being said, I really hope they do pull this off!

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I would love to see the Kiwis nail this first go. 

Your western island mates are cheering for you.

 

I suspect 4 or 5 attempts will be required to knock out the unknown unknowns.

There are a lot of new design elements that have not flown together or at all.

Engines, tanks, controllers, sensors, software, operational elements, maybe other stuff.

You can only test so much on the ground/simulator.

But this campaign is going to be legendary. I cant wait for the results.

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