1662

Said solid rocket boosters also blew up a shuttle that one time.

1663

Coming back to this a few days later, but $60m is the current launch cost, as I understand, and not necessarily the total rocket cost.

Cursory Googling reveals zero good estimates of the unit cost of a Falcon 9 first stage, which makes sense to me: SpaceX’s own accountants probably haven’t quite managed to tease development costs out from their current production costs.

1664

In other news, another article about the Emdrive, everyone’s favorite push-on-the-inside-of-a-box hypothetical engine. This one summarizes an article on arXiv which purports to present a plausible-sounding physical explanation for the EmDrive’s behavior, which also explains the fly-by anomaly (gravity assists sometimes yield changes in velocity up to 10 millimeters per second off of the predicted delta-vs). It goes like this:

  1. The Unruh effect, a predicted consequence of general relativity which claims that an accelerating observer observes blackbody radiation where an inertial observer observes none, is an actual effect.
  2. The mechanism of the Unruh effect, Unruh radiation, is what causes inertia: the pressure of Unruh radiation resists accelerations.
  3. As a consequence, inertia is quantized at very small accelerations. This part is the one that escapes my layman’s understanding of physics. The article says “[… the wavelengths become so large they can no longer fit in the observable universe. When this happens, inertia can take only certain whole-wavelength values and so jumps from one value to the next.” That may be more illuminating for you than for me.
  4. Because photons have mass, when they bounce off of the ends of the Emdrive cavity, they experience inertia.
  5. Because of the difference in size at each end of the Emdrive cavity, the permissible wavelengths of Unruh radiation are different at each end (they must fit exactly in the cavity, to quote from the abstract of the paper).
  6. Since the amount of inertia a photon can have depends on the permissible wavelengths of Unruh radiation, the inertia of the photons must change between bouncing off of each end of the cavity.
  7. Since momentum must be conserved, this inertia-switching generates a thrust.

Like I said, I lose track of things at about #3 and don’t really pick up the thread again until #7, but some quick wiki-reading suggests that none of this is obviously crackpottery. The existence of the Unruh effect is disputed, but at the least, there isn’t a strong consensus against it. The author of the paper, Mike McCullough, has a history of published papers on the same topic, quantized inertia, and makes some predictions about how the Emdrive should behave if his theories about Unruh radiation and quantized inertia are correct.

As a sometimes author of hard science fiction, things like this make me tear my hair out. If the Emdrive turns out to be for real, some random engineer stumbled upon it with a more implausible design than I could have thought up if I’d been trying to design something that sounds like it shouldn’t work. “We’ll build a box that’s bigger at one end, then shoot a bunch of ping pong balls into it with a leaf blower, and it’ll move toward the narrow end for some reason. Science!”

I imagine it would be even worse for rocket scientists. “We spend tens of billions of dollars on designing the cheapest, safest, most reusable rocket yet, and some guy with a radioisotope generator and a dumb-looking engine with nowhere for reaction mass to come out comes along, and can orbit anything his engine can lift from sea level without having to use any explosive consumables at all? Come on!”

1665

Unruh radiation? I really hate it when physics theories are named after people. Makes remembering which one is which very difficult.

1666

All very true, and great examples of why actually landing the booster instead is such a huge practical deal beyond being bloody cool and an amazing technical achievement.

Accurate, though the failure had nothing to do with the re-usable aspects of the SRB as far as anything I’ve seen. Lots of things went very, very wrong there, but the re-use of the boosters wasn’t it.

1667

Interesting breakdown on the barge landing.

1668

‘SpaceX plans to land Dragon spacecraft on Mars’:

very cool.

1669

2018? Wow, that’s super exciting. 6000kg landing on mars would be an amazing achievement.

1670

2018 seems ridiculous. It would take at least half a year to fly there, probably more, the window is only open every two years and they haven’t even tested the heavy lift rocket yet. Still. I’m glad they’re being ambitious.

1671

I’m curious, if the purpose is to tests are to figure out the best way to land and relaunch from a body like Mars, why not start more locally? You could learn a lot doing Moon missions. Could even get some nice science done.

1672

They’re talking about launching in the April-May 2018 launch window, not being there in 2018.

1673

Well if you launch in May 2018 you’ll still get there in 2018…

— Alan

1674

Trip to Mars is 6 months not 18 during the launch window, no?

1675

It’s ridiculously ambitious, agreed, but not outside the realm of possibility. The falcon heavy will have to go flawlessly for this to have any chance at 2018. Hell 2020 seems very risky when compared to NASA’s usually schedule.

Apparently Space X has been firing the falcon engines at 40-70km on every rentry, helping them gather data on how they would perform in Mar’s thin atmosphere:

1676

Yes launch window trip time to Mars is ~6 months.

FYI only 2+ months away from Juno’s arrival at Jupiter.

— Alan

1677

The Vikings did it ages ago (my personal favourite space exploration from my ‘youth’), so i’m sure Space X ‘could’ do it now :)

1678

4th of July!!!

1679

Just curious, any celebrations going on at JPL for it? For the original Voyagers they used to have Planetfest with the Planetary Society… anything geared up for Juno?

— Alan

1680

‘From zero to 100mph in 1.2 seconds, SpaceX’s SuperDraco thruster delivers’:

1681

That is a great question, and I’m sadly oblivious to any planned celebrations. I will find out and report back.