Tuesday, November 18, 2014

And Now, For Our Next Trick...

So, we landed on a comet. What do we do for an encore?

Well, eventually we land on another comet, and do it even better.  But it will take time to figure out why what went wrong went wrong, and design and fund another mission, and get there. This will take years, but comets will still be there when we are ready to launch. We can, and must, and will be patient. We will play the long game. When we do it again it will be easier to do better because we will have learned in the interim.

In the meantime, I will quote the admirable Emily Lakdawalla, who did good service covering the Philae landing on twitter.
Coming up soon: Japan launches Hayabusa 2, an asteroid sample return mission, on November 30. New Horizons wakes up to begin encounter science for its Pluto flyby on December 6 (the flyby itself is next July). Dawn will get its first images of Ceres in February, and they'll already be better than Hubble's. Curiosity is doing the kind of science it was intended to do for only the third time on its mission, at a spot called Pahrump Hills in Gale crater. Opportunity is very close to the peak of the mountainous crater rim it's been climbing for a couple of years. Cassini has been on a high-inclination orbit at Saturn for a long time, but will soon be switching into an equatorial orbit that means lots more views and close flybys of Saturn's mid-sized icy moons. There's a lot going on!! But some sad things are coming -- both MESSENGER at Mercury and Venus Express at Venus are expected to crash into their respective planets within the next few months, ending those long missions (they've both nearly run out of maneuvering fuel).
Less immediately, in 2016 Juno arrives at Jupiter. And OSIRIS-REx launches, also intended to visit an asteroid and bring back samples.

We launch, and launch again. It's a great life, if you don't weaken.

These are the days of miracle and wonder...

Saturday, November 15, 2014

Comets Are Weird

So this week, humans landed a robot on a comet. And when I say landed, I mean we bounced it off the comet twice, until it came to rest.

Philae was one of two robot spacecraft launched over ten years ago. Rosetta was the larger of the two, and still orbits Comet 67P.

Philae bounced twice, and landed in a place that was mostly in shadow and so starved for solar  power  It continued to transmit data until only enough power was left from her batteries to put the craft in hibernation, and it uploaded quite a lot. Plucky robot.

It gave us images of the surface. The one above is the strangest landscape beyond Earth's surface I have seen to date.

But wait, there's more.

We have known for some time that the nucleus of the typical comet is mostly fluffy; typically about half the density of water. They have been described dirty snowballs or snowy dirt balls.

But wait! Some of the uploaded data already show a more complicated picture than we thought. One of Philae's experiments, MUPUS, was designed to hammer one of its sensors into the surface of the comet. The surface turned out to be much harder than expected, and apparently broke the probe.

Perhaps we should think of comets not simply as dirty snowballs, but dirty snowballs that a cosmic prankster dipped in water and then left at subzero temperature until the exterior was as hard as rock. Alternatively, this might be a condition peculiar to impact craters on comets, and Philae happened to fall into one. But Philae also bounced pretty hard at the first landing site.

Or one might think of the comet as a a deep space Mallomar, or in this case a chocolate dipped Peep: a hard crust around a fluffy interior. But the reality is probably still more complex than that, with all but the most recent crater floors dusted with ejecta from later impacts.

And  even the fluffy parts of the comet might include large chunks of less fluffy matter: dirt, rocks  or ice.

Update:  As of November 18, ESA scientists say the data received so far suggests 4-8 inches of dust over hard ice, and a fluffy porous interior below that.

Wednesday, November 12, 2014

Humans Continue to Play the Long Game in Space

Today, the European Space Agency successfully landed a robot spacecraft on a comet for the first time in human history. Well done! It was launched ten years ago.

It was intended to launch even longer ago, to a different comet in January of 2003. A 2002 launch failure of the intended launch vehicle required a change in plans.

This is how you do it: with patience!

Tuesday, November 11, 2014

Humans Prepare to Land a Robot on a Comet Shaped Like a Rubber Duck

Well, they are and it is. The pictures remind me of an Alp in space, because that's more or less what comets are. There's a lot of snow.

But, I read that the comet itself is quite dark, like a lump of coal.

These are the days of miracle and wonder.

Sunday, November 09, 2014

Ansari and Orteig: The Hard Going to the Stars

On Friday, October 31, Spaceship Two, Virgin Galactic's suborbital manned rocket, broke up in flight, killing one pilot and seriously injuring the other, and providing another harsh reminder of the risks of space flight.  Following the loss of an Antares rocket on October 28, it was a bad week for the launch industry.

I'll repeat what several other people has have said this week: space is hard.  Getting to space requires harnessing enormous energies with very light hardware. The Space Shuttle high pressure fuel pumps
each produced about 71,000 hp, equal to 15 large diesel locomotives, yet they were not much bigger than an automobile engine. They had a power to weight ratio of over 100 hp/pound: .5 hp/pound is typical for an automobile engine.

Ed Kyle puts it well:
Modern rocketry is a frightening balancing act. To accelerate from a dead stop to more than seven times faster than a rifle bullet in a few minutes, an orbital launch vehicle must create, contain, and endure extreme pressures, temperatures, and forces. All it takes to trip up the process is one loose connection, one small piece of sand or rust, a bad bit of metal or insulation, a misplaced bit in a control program, or an unexpected vibration.
Suborbital is technically a lot easier. 2,500 mph is probably enough to reach space briefly on a suborbital flight, compared to about 18,000 for orbital. And six times the velocity requires 36 times the energy, and much better shielding on reentry.

SpaceShipOne had the enough volume and payload to carry three humans to at least 100 km in altitude.  SS1 was less than four metric tonnes, fully loaded. It was launched from the White Knight One carrier aircraft, probably similar in mass fueled but not including the SS1 payload.

The closest orbital comparison is the Soyuz launcher and manned spacecraft, over 300 metric tonnes fully fueled and capable of carrying three humans to orbit and back.  And that's for an expendable launcher, while SSI and WK1 were reusable except for the SS1 motor.

But. While suborbital space flight is technically a lot easier than orbital, its economics are far more challenging. Commercial satellites are so profitable that their owners are willing to pay tens of millions of dollars to get one launched. The most capable launchers can charge over $100 million for an orbital payload.

If Virgin Galactic fills six passenger seats on SS2 per flight at their announced price of $250,000, that's only $1.5 million. A brief suborbital flight measured in minutes is simply a lot less valuable than an orbital flight that can last as long as you have supplies for.

And building a reusable rocket plane capable of speeds in excess of Mach 2 is not a trivial task at all.

One that carries six passengers is even harder. SS1 had a theoretical capacity of only two passengers. The supersonic X-planes carried only a pilot.

Compare the Orteig prize to the Ansari X Prize.

The first offered a prize of $25,000 in 1919, worth about $340,000 in 2014, for "the first aviator of any Allied Country" to fly nonstop from New York to Paris, or vice versa. To win required an aircraft that could fly the required distance at about 100 mph. Lindbergh won, but there were several other entrants that could have won if history had been somewhat different. They included a Wright-Bellanca WB-2 and a Fokker C-2 Trimotor, both of which became successful commercial aircraft, although operating in an environment of subsidized mail transport.

Linbergh's plane was a unique variant designed for the stole purpose of winning the Orteig Prize, but still part of a successful family of Ryan monoplanes.

In contrast, when SpaceShipOne attempted the Ansari X Prize in 2004, there were no rivals remotely ready to fly,  Building a rocket-powered airframe that can fly to the edge of space at over twice the speed of sound and return safely is much, much harder than flying nonstop from New York to Paris.

When only one company has shown that they can fly a reusable rocket capable of carrying passengers into space, if that company blunders in building their operational vehicle, there's no one to provide an alternative.

Yes, there's XCOR and their Lynx spaceplane. I wish them well, but they haven't flown it yet.

I believe the people responsible for SpaceShip Two have made at least major mistakes. The first was in making a jump to a spaceplane twice the size of the one that one went to the Smithsonian, instead of following it with a SpaceShip 1.1 for further flight tests followed by operational flights.  The second is choosing and sticking to the immature technology of hybrid rocket motors.

I think it's fair to say that entrepreneurs like Branson are rather more prone to hubris than the  average mortal. But it's a mistake to think that NASA administrators are quite free of hubris: pre-Challenger estimates of Space Shuttle reliability and the decision to launch Challenger in 1986 would both seem to qualify.

And government space agencies have their own unique failure modes: particularly, making important technical decisions influenced by jobs at stake in key Congressional districts, or the non-US equivalent.

I believe that some version of SpaceShip Two can be made operational, perhaps with significant modifications, and be relatively safe by the standards of dangerous pursuits like climbing Everest. Unless the investors lose faith in the project.

But remember: space is hard.

Saturday, November 08, 2014

The Bridport Muster: 1457

The Bridport muster  roll gives an unusually complete record of one of the musters held by the Lancastrians in 1457. Held at Bridport in Dorset, it records the arms owned, or that should have been owned, or in 82 cases were not owned, by 201 named individuals. Frequently the contraction ordinab occurs, probably for the Latin ordinabitur, or "he was instructed". Presumably it reflects equipment the individual should have had, but didn't bring to the muster. It's unclear how many of them the authorities expected to actually make good the deficiency, and how many would simply by fined.

For those that actually had bow and arrows, the most common kit was was jack, sallet, bow and arrows, often with a sword and dagger, for 33 individuals. Two had jack, sallet and habergeon: the 1473 Burgundian ordinance of St. Maximin de Tréves expected mounted archers to wear a a habergeon beneath their jack. One had jack, wallet and leg harness. One had a sallet and habergeon. 20 had bow and arrow, but no armor. 7 of the archers had a sallet as their only armor.  5 had a jack but no sallet.  Two had brigandines but no sallet.

This is somewhat at variance with Le Fèvre and Waurin's report that most of the English archers at Agincourt were unarmored: one would expect an expeditionary force to be better equipped than a local muster. Probably the many Welsh foot archers were less likely to have armor, and so brought down the average prevalence of armor among the archers as a whole.


Friday, November 07, 2014

The English Archers' Equipment at Agincourt

The archers were for the most part without armor, in their pourpoints, with their hose rolled down, with hatchets and axes hanging from their belts, or long swords.  Some were completely barefoot, and some wore hunettes (huvettes in Waurin) or cappelines of boiled leather, and some of osier reinforced with iron (sur lesquelz avoit une croisure de fer: covered with pitch or leather in Waurin )
Jean Le Fèvre and Jean Waurin were both present at that battle, and both wrote chronicles that described what happened at Agincourt. Their accounts were not independent: they essentially compared notes after the battle and their two versions of what happened were very similar. I have translated Le Fèvre above, with significant variations in Waurin noted.

Hunettes/huvettes and cappelins were head defenses.  Huvettes  could be made of boiled leather, but also iron, scales and plates, and were sometimes described as small and round.  Cappelins seem to have been a sort of helmet favored by infantry and light cavalry. Le Fèvre and Waurin seem to be describing some of the English archers wearing small helmets with lower, less pointed crowns than the bascinet of the contemporary man at arms.


Le Fèvre de Saint-Remy, Jean, and François Morand. 1876. Chronique de Jean Le Fèvre, seigneur de Saint-Rémy, transcrite d'un manuscrit appartenant à la bibliothèque de Boulogne-sur-Mer. Paris: Loones.

Thursday, November 06, 2014

The Dunning-Krugerrand Effect

This is a cognitive bias in which incompetent individuals overestimate their own competence, and so make excessive investments in a bright and shiny commodity metal, in the false belief that it is undervalued compared to other investments.

Wednesday, October 29, 2014

We Lost a Rocket Last Night

We lost an Antares rocket and a Cygnus spacecraft, bound for ISS, last night. About twelve seconds off the pad something went wrong. There seems to have been rapid unscheduled disassembly at the aft end of the launcher, and then the rocket fell back to the ground and exploded.

Throwing hardware out of our gravity well is really, really hard, and this is a reminder. The energies required are immense, yet the builder is required to make the rocket as light as possible

But, we know this is hard. So the United States can also reach ISS with completely different hardware: SpaceX's Dragon spacecraft and Falcon launcher. Russia, the European Union and Japan all have their own spacecraft and launchers as well. Our bench strength is deep.

To watch the launch I stepped out on the patio with my phone to point the way to due south and my laptop to watch the launch until it climbed above the horizon. Space travel is still hard, but we do live in an age of marvels.




Saturday, October 25, 2014

The Great Docudramatist of the 16th Century

It is well to remember, in watching any of Shakespeare's histories, that he was always a playwright first. Whenever he had to choose between good drama and good history, drama would win.  And he was working from Holinshed, at least one remove from the primary sources.

Shakespeare was in the business of writing seductive untruths for a living. Remember that when you watch his Henry V, or any of his histories.