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Comment: Re:Wrong Focus (Score 1) 76

by Rei (#49366605) Attached to: SpaceX's New Combustion Technologies

Not today. But maybe in the future. If you can develop a crazy-power-dense energy source and cooling system, you could probably do it with a MPD thruster. The research I've seen on MPD thrusters operating in pulsed mode yields crazy output relative to the mass of the thruster. But you can't run it continuously because it'd overhead and take way too much power. But who knows about the future? There's the potential for extreme heat conductors like isotopically pure diamond, maybe a some kind of fission fragment reactor with a deceleration grid for power...

(of course, if you have a fission fragment reactor, at least when you're in space itd be best just to jet your fragments rather than use them to power a MPD thruster...)

Comment: Re:It is (Score 1) 76

by Rei (#49366565) Attached to: SpaceX's New Combustion Technologies

I hope they simulate propane too, not just methane. Propane has some really interesting properties as rocket fuel but have (like methane) never gotten much research. But now there's a big rush to research methane as fuel based on the concept of generating it on Mars - so propane still gets left in the dark.

Methane's ISP is only very slightly better than propane's - 364,6 vs. 368,3 at a 100:1 expansion into vacuum and 20MPa chamber pressure. But propane at around 100K (note: not at its boiling point, 230K) has far higher density (782 kg/m^3), closer to that of room temperature RP-1 (820 kg/m) then that of boiling point methane (423 kg/m^3), which reduces tankage mass and cost. 100K propane's ISP is of course better than RP-1's 354.6 in the same conditions as above. Plus, its temperature is similar enough to your LOX that they can share a common bulkhead, which reduces mass further and simplifies construction.

Hydrogen generally is the easiest fuel to synthesize offworld. Methane is generally second, and propane third. Hydrogen is often rejected as a martian fuel because of the tankage and cooling requirements. Methane can be kept as liquid on Mars with little cooling in properly designed reflective / insulated containers - but so can 100K propane, in similar conditions, but with significantly smaller tankage requirements.

It seriously warrants more research, I tell you what.

Comment: Re:Mystery (Score 1) 272

by satch89450 (#49364833) Attached to: Why the Final Moments Inside a Cockpit Are Heard But Not Seen

Looks like the memory card on the the black box has been "lost". Is this true? How is it possible if the black box is designed to withstand 3500 g ? Would the data on the memory card contain information on the door status (locked / unlocked / open / closed /...) ?

Also, why isn't data streamed to ground stations nowadays? And why black boxes do not float ?

In short, together with the door design, it all looks like amateuristic design.

1. Door-locked status: Don't know, but you can't record everything -- there are already plenty of channels that are captured that are far more important

2. Streaming to ground: The NTSB has been working with other air safety bodies to make recommendations to do just that. One issue is available bandwidth: there just isn't enough of it available. So the amount of information that can be transmitted would be limited.

3. Floating black boxes: Like the downlink scenario, breakaway recorders that float are being looked into. More importantly, though, are better crash locator beacons, so the crash debris field can be found more quickly.

Comment: Re:Conditional recording (Score 1) 272

by satch89450 (#49364793) Attached to: Why the Final Moments Inside a Cockpit Are Heard But Not Seen

Perhaps they could video the cockpit (and the fuselage for that matter) and destroy the footage once the plane has safely landed.

In the case of the FDR and CVR, that already happens, sort of. The devices are only able to handle a finite amount of data, and new data overwrites the old. So eventually you effectively get what you are suggesting by normal operation.

And there is a good reason not to dump the recordings. During an investigation of a crash where wake turbulence was suspected to be the main culprit, the investigators had the FDR of the plane ahead of the accident plane pulled to see just exactly where it was in relation to the accident plane. As I recall, the data showed the leading plane was much closer to the accident plane than anyone had suspected, and the wake turbulence would have thrown the accident plane around violently. WIthout the additional data, investigators would not have been able to confirm a hypothesis as to a contributor to the crash.

Comment: Quote (Score 1) 134

by Rei (#49363093) Attached to: Russia Wants To Work With NASA On a New Space Station

"We are pleased Roscomos wants to continue full use of the International Space Station through 2024 -- a priority of ours -- and expressed interest in continuing international cooperation for human space exploration beyond that. The United States is planning to lead a human mission to Mars in the 2030s, and we have advanced that effort farther than at any point in NASA's history. We welcome international support for this ambitious undertaking.

Yeah, that's basically "Go F* yourselves" in diplomatic speech.

And as it should be.

Comment: Re:WIMPs (Score 1) 215

by lgw (#49362505) Attached to: Dark Matter Is Even More of a Mystery Than Expected

Yes, you've got the core of the scientific method right in hand. You use math to formalize some model that explains both old and new observations, then you extrapolate using the math to make predictions, then you weed out all the failures with the next set of data. Everyone in physics does understand this, except maybe the string theorists, who went off the rails some time ago and IMO are an embarrassment to the field now.

But the math is the tool that lets you make that prediction, and it's not enough for the current model to be "wrong", you have to have an alternative that successfully predicts new data. That what all the internet cranks and crackpots seem to miss: yes, fine, you can contrive limitless alternative explanations for the existing data. So what? It's all about the predictions, and those are usually meaningless without the math to back them up, to set bounds and make them falsifiable.

The inability of GR to give a good model at universe-scale is hardly new - Einstein himself identified the need for a cosmological constant quite early on. The mystery has only deepened since - but that doesn't necessarily mean anything's wrong with GR, only that there's more to learn (dark energy is easy to describe in GR terms, but GR gives no explanation of why it's there in the first place).

He keeps differentiating, flying off on a tangent.

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