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A fifth RS-25 on the corestage and a stronger upper stage would just about get them to 130 metric tons to L.E.O. So why aren't they doing it?! That's the $64 billion dollar question. Almost literally...
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Space Science Coverage / Re: JAXA Hayabusa-2 Discussion
« Last post by CuddlyRocket on 06/17/2018 11:30 PM »
I read that the water found on comet Churyumov - Gerasimenko by Rosetta/Philae was slightly different, which meant that comets like it could not have brought water to Earth.

More precisely, they couldn't have brought all the water to Earth. If there had been another source of water, it would likely be different thereby resulting in the mixture being different.
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SpaceX BFR - Earth to Deep Space / Re: Elon The Boring Company
« Last post by nacnud on 06/17/2018 11:30 PM »
There seems a reasonable solution to both removing the muck and powering the TBM. Temporary storage of muck and electricity on the TMB.

The muck train when attached recharges the battery on the TBM from batteries on the train and empties the muck storage into the cars making up the train. You could even have a standard car that had a motor, batteries and muck storage in one unit.

The relative size of the batteries on the TBM and train and the size of muck storage on the TBM and train would depend on a lot of factors I have no idea about (time take to swap trains, distance to tunnelling face, rate of tunnelling, power used to tunnel etc) it should allow for continuous tunnelling though.
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Quote
NASA replied: “Now that the SLS design has matured and the program has more data as a result of progress with hardware manufacturing and testing, our current analysis shows the Block 1 configuration of SLS can deliver an estimated mass of 95 metric tons (209,439 pounds) to low-Earth orbit based on a 200 by 200-kilometer orbit with a 28.5 degree inclination, which is a commonly used orbit in the industry for estimating performance.”

Here's the SLS users guide. Unfortunately, Block I performance is not listed. Block IB can put a minimum mass of 94.0 t into a 463 km orbit. Future upgrades increase this to 100.7 t. Block II is 108.3 t. Extrapolating to 200 km, I get 97.7 t, 104.7 t and 112.3 t. I don't see how Block I can get anywhere near 95 t with iCPS using a single RL-10 engine. We also see that Block II doesn't get anywhere near 130 t payload to LEO.

https://ntrs.nasa.gov/search.jsp?R=20170005323

Pretty ironic. After all the justifications given for this system to be scaled up and made as big as it is, NASA still utterly fails to conform to the letter of the law even when it comes to meeting the 130 ton vehicle requirements

Even after giving Alabama everything they wanted and more the vehicle still can't do a single thing it was required to do by law.

It's really unbelievable at this point. I wonder how much more ridiculous this is going to get before we reach stick levels of absurdity.
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SpaceX BFR - Earth to Deep Space / Re: Elon The Boring Company
« Last post by CuddlyRocket on 06/17/2018 11:24 PM »
Initial skate test:

This seems to be a bit more interesting than people have remarked upon.

We've previously been told that the two modes of traffic would be either a flatbed skate upon which a car or other vehicle would ride (though I suppose you could put a cargo container on board instead) or a dedicated skate with an enclosed space for passengers.

This appears to be a third option. One where the car (a Model X in this case) runs on its own tyres but is guided and powered by some mechanism that seems a lot less substantial than a flatbed skate. In fact, given an appropriate interface between the mechanism and the car, the car could provide its own motive power. Why go to the expense of providing the skate with its own battery and other power systems where the car could provide the power and energy itself?
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Historical Spaceflight / Re: Our beloved Judy Resnik
« Last post by Astrovox on 06/17/2018 11:17 PM »
A slightly better version of Judy's yearbook photo.
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It's sequential.  First you use lunar fuel to take satellites from LEO to GEO, saving mass.  Then you start to replace the mass of satellites with extraterrestrial materials.  Then they get more advanced until you can do things like space solar power.  ULA seems to think there is promise in microwave power transmission. 
You're going to need to break down your assumptions.
One ton of fuel in LEO may cost $10K (if you believe P2P), $300K if you assume $50M per BFR launch.

Given that this is a small cost for even 50 tons of fuel for all current GEO satellites, and given that the actual incremental cost may be close to $0, where is your funding coming for making this lunar fuel?
Lunar fuel is also annoyingly far away from LEO - something like 2.5km/s if you're able to do aerocapture, 6km/s if you're not.

(Above numbers are broadly similar for new armstrong)

I'm not saying ISRU is a bad plan, but if you're planning on developing a billion dollar ISRU plant, that buys a _lot_ of fuel.
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Here’s the first deboost:



[original size]

almost 90 km!
The graph shows the perigee, the semi-major axis and the apogee obtained from the TLEs.

The updated reentry trajectories (9 TLEs used):



[original size]

but it will change again.
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SpaceX BFR - Earth to Deep Space / Re: Elon The Boring Company
« Last post by RedLineTrain on 06/17/2018 10:06 PM »
From what I can tell, most of the big TBMs use either slurry or conveyor belts to remove the muck.  But apparently, some recently have figured out that simple old muck cars are best when boring long distances for up-time reasons.

http://www.therobbinscompany.com/projects/great-hydro-network/
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I'm locking this for several (should be) obvious reasons, not all of them are to do with the posts.

Use a pinch of sponsored salt for anything Politico report.
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