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Comment: Re:How convenient! (Score 3, Informative) 62

by cjameshuff (#47168143) Attached to: Lepton Universality In Question, a Standard Model Assumption

Consider how long it took to gather enough of the right events to be reasonably certain about the Higgs, the various false alarms that vanished as more data was collected, etc. Another version just a bit rarer could easily be lost in the noise. Or the two could be similar enough that their signals aren't distinguishable from each other yet.

Comment: Re:WTF is wrong with you? (Score 1) 193

by cjameshuff (#47013659) Attached to: Are Glowing, Solar Smart Roads the Future?

I didn't say it couldn't be done. I said it was a terrible idea, and that your claimed advantage (guarantee of being free from obstruction) didn't actually exist. The same solar cells placed in a solar farm located in a sunny area without a thick layer of textured, dirty glass, leaves, vehicles, etc between them and the sun could easily produce several times the output. The electronics and cabling used to collect the power and convert it to a useful form would be put to far better use in such a farm, in a road most of the capacity will be wasted due to the non-ideal location and orientation, frequent obstructions, etc.

Comment: Re:WTF is wrong with you? (Score 2) 193

by cjameshuff (#47007735) Attached to: Are Glowing, Solar Smart Roads the Future?

"As far as roads go, here's an opportunity to leverage a massive area of square footage that is guaranteed to be clear of plants or other obstructions"

Uh...no, it's actually guaranteed to be obstructed frequently, by cars, leaves, snow and ice (the suggestion of melting these away is absurd, there's nowhere near enough power for it), dust and dirt, machine grime, nearby trees, its own textured surface, etc. In addition, with all the stuff embedded in them and the enormous quantity of modules needed, things are going to break frequently, and maintenance access requires shutting down roads. Beneath the road surface is a *terrible* place for solar panels.

Comment: Re:SpaceX isn't ready (Score 4, Insightful) 272

On the man-rating...the cargo Dragon is actually already man-rated. Once it's up at the ISS, people have to open the door and go inside to unload supplies and load experiments for return to Earth. What it lacks is a launch escape system. Well, and seats.

On the versatility...apart from carrying more cargo and more crew, the Dragon is equipped with heat shielding that can handle return from lunar or Mars trajectories, and for reuse. It's even adaptable for landing on other bodies such as Mars, as in the Red Dragon proposal. It's launcher can operate in single core or three core variants, eventually with varying degrees of core reuse depending on payload/orbit requirements.

So the OP's claim that Soyuz is "much more versatile" is really rather bizarre...

Comment: Re: SpaceX always have an excuse for failure (Score 1) 110

by cjameshuff (#46888189) Attached to: SpaceX Looking For Help With "Landing" Video

It's entirely possible it actually was recorded in some buoyant piece of hardware, just in case...but it'd probably have been intended to be picked up out of the debris field of a descent failure in fair weather. Where would it have ended up after the storm tore the rocket apart?

They could engineer a ruggedized black box with a tracking beacon and deployment system...but that's a bit much when they've only got a few water landings left, and those are unlikely to happen in storms. I think they were more concerned with making the rocket land itself.

Comment: Re: SpaceX always have an excuse for failure (Score 1) 110

by cjameshuff (#46888139) Attached to: SpaceX Looking For Help With "Landing" Video

They claim it was successfully able to return to the surface and perform a soft "landing". Which it did...and it did so in thoroughly bad weather, in high winds and on heavy waves instead of solid ground. Their mission objectives were met completely the moment the rocket cut its engine and started tipping over. Actually fishing the thing out of the ocean intact would have been a nice bonus, but it has nothing to do with their actual plans for recovery and reuse...and the only reason it didn't happen is that nobody wanted to attempt it during the storm.

Comment: Re:A 2nd backup camera? (Score 3, Informative) 110

by cjameshuff (#46888035) Attached to: SpaceX Looking For Help With "Landing" Video

You *do* realize the power output of a rocket engine isn't electrical, right?

In reality, spacecraft have strictly limited power budgets. The booster's electronics are running off battery power from the moment the umbilicals disconnect. It also flew above the bulk of the atmosphere, so you can't exactly rely on air cooling to keep the transmitter from frying itself...and there's plenty of other power-consuming, heat-producing electronics that have rather more important functions. And a more powerful transmitter would be completely unnecessary for the solid-ground landings, which SpaceX hopes to start by the end of the year.

Comment: Re:A 2nd backup camera? (Score 2) 110

by cjameshuff (#46886031) Attached to: SpaceX Looking For Help With "Landing" Video

Stronger signals take bigger transmitters with higher power consumption. They don't normally require such a signal: for launch (and eventual solid-ground landings) they have line of sight with big receivers, and when they actually recover a stage, they'll be able to get recordings. The splashdown was below the horizon from the launch site, and the video signal was picked up from a chase plane. To top it all off, weather was lousy and deteriorating fast.

They'll have a lot more launches and landings, another water-landing test is coming up soon. Getting video on an early test that was given a 60-70% chance of failure and wasn't even an actual solid-ground landing was a lower priority than trying to make it succeed.

Comment: Re:What about the DC-X? (Score 1) 176

by cjameshuff (#46846429) Attached to: SpaceX Files Suit Against US Air Force

The DC-X was a small scale experimental vehicle built to demonstrate vertical takeoff and landing under rocket power. It was never able to or intended to fly very high or very fast.

This was the first stage of a Falcon 9 orbital launch vehicle, returning after boosting the second stage and payload, on a launch that actually delivered a payload to the ISS. It's far bigger (the empty Falcon 9 first stage masses about as much as the fully fueled DC-X), far more capable, and it's currently being mass produced. It also uses a cheaper and easier to handle fuel and a more efficient and flexible staged architecture than the SSTO architecture envisioned for the launchers derived from DC-X.

Comment: Re:Not sure about the recovery test (Score 1) 125

by cjameshuff (#46797859) Attached to: SpaceX Launches Load to ISS, Successfully Tests Falcon 9 Over Water

Those boosters were hollow steel tubes, open at the back. Seawater partially flooded them, that's why they popped up. The Falcon 9 first stage is mostly empty tanks that aren't going to flood (barring severe damage from the waves). If held vertical, the weight of the entire stage wouldn't push it down even two meters into the water...its diameter is greater than that. The engines aren't that heavy, half the mass of the vehicle is in those very long tanks...it's going to float very high in the water, on its side.

Comment: Re:Cost breakdown (Score 1) 125

by cjameshuff (#46797443) Attached to: SpaceX Launches Load to ISS, Successfully Tests Falcon 9 Over Water

NASA is paying for Dragon missions to the ISS, not just mass to orbit. They're getting a lot more than the launch: delivery of a Dragon loaded with supplies to the ISS, a brand new man-rated spacecraft that people will be working inside while it's at the ISS, return of more payload to Earth than any other option currently available, and operations in orbit and recovery. And probably also various other expenses and extra work involved in working with NASA and the other ISS partners. Their defense launches are also priced higher for the same reason, working with the DOD involves extra work that the customer demanding it has to pay for.

Comment: Re:Not sure about the recovery test (Score 2) 125

by cjameshuff (#46795543) Attached to: SpaceX Launches Load to ISS, Successfully Tests Falcon 9 Over Water

It doesn't need to brake to a complete stop and then retrace its outgoing path, it needs to bend it's largely-upward trajectory into one that comes back down over the landing site, and manage its velocity so it doesn't go too high and hit the atmosphere too fast on the way back down. As for the difference in separation speed, the flight profile for the reusable flights may very well take a more vertical trajectory during the first stage burn, the first stage taking on more of the gravity losses and going more for altitude rather than speed, and the ratio of propellant loading between the first and second stages may be different for reusable flights...they could oversize both at a minor cost in mass and tweak the ratio to suit the launch, the maximum loading being set by the first stage thrust rather than the total tank capacity.

Comment: Re:Not sure about the recovery test (Score 4, Informative) 125

by cjameshuff (#46794183) Attached to: SpaceX Launches Load to ISS, Successfully Tests Falcon 9 Over Water

It got up there while carrying a lot more propellant and a whole second stage. The braking burn uses only 3 engines to limit the acceleration and ends with just enough propellant left to stop it when it reaches the ground. On top of this, it gets passive aerodynamic braking the whole way down.

The mass ratio for the first stage burn, burdened with the second stage and braking propellant, is probably around 4, and a braking burn with equal delta-v would need the same mass ratio, except with no second stage and ending with the rocket empty. The overall first stage mass ratio is around 30, so all else being equal, a return would take around 3/29 = 10% of the propellant on the first stage. But all else is not equal, the returning rocket is mostly empty tanks descending through a thick atmosphere that provides plenty of braking, so the final burn only has to bring it to a halt from terminal velocity, and I omitted the second stage propellant. Overall, 4% sounds quite reasonable.

The bogosity meter just pegged.

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