Thursday, March 12, 2015

The Importance of Dog Bones and Doughnuts: Revisiting the Freeluna Space Program

Given the success of SpaceX and Elon Musk's and Mars One's intent to colonize Mars, I think it's high time to revisit the notion of a rotating space station in low earth orbit, and eventually using said station (or something like it) to transport people to Mars. Before we go colonizing other planets, we really need to find out if humans can stay healthy in a partial gravity (less than 1 g but more than 0 g) environment, such as what humans will encounter on Mars (0.377 g) or the Moon (0.165 g). To the best of my knowledge, there has been absolutely no research done in these two gravity regimes. Our knowledge of zero gravity (microgravity) is extensive, and we have known for decades that exposure to it causes substantial physiological decay. What we need to find out is how badly or if Mars colonists will suffer decay within the gravity field of Mars.

To this end, let me introduce you to the concepts used to design a rotating space station created for the purpose of testing partial gravity fields on the human body. In the old 50's sci-fi movies, we saw plenty of examples of spinning wheels in space that represented space stations. In the movie 2001: a Space Odyssey, Dr. Heywood R. Floyd first finds himself heading for a double wheeled space station spinning in Low Earth Orbit, before he heads to the moon. The principle of artificial gravity used in these films is just an application of conservation of angular momentum, commonly called centrifugal force. Spinning a person around in circles can cause problems such as dizziness for some people, but almost all people can tolerate a spin rate of 2 rpm and some people can tolerate a spin rate as fast as 7 rpm. Depending on the RPM and the gravitational pull one is trying to induce, the radius of the spinning space station varies. The formula for calculating the radius for earth-like gravity is as follows:

Where 9.8 is acceleration of gravity at Earth's surface in meters/second^2 (use 3.7 for Mars and 1.6 for the moon), 'pi' is 3.14159.., and so on. With this calculation in hand, you can derive various habitat radii for different RPM.

If one so desired, a apparatus could be set-up on earth to simulate these spin rates and radii to test for human spin tolerance, such as with a vehicle connected to a central pivot via appropriate length cables and forced to drive around in circles to simulate station spin. The induced gravitational pull would be somewhat over 1 g, but should allow observation of inner ear phenomena, nonetheless. A graph below shows the various speeds of such a system...

Building a complete space station ring could get quite expensive, but building just a pole with small habitats on either end of it would be far less of a challenge. For a Mars equivalent gravity in a station spinning at 2 RPM, the length of the pole would need to be about twice the radius shown in the first table, or about 169 meters long. This could be reduced by offsetting the center of mass of the station towards one end of the pole. By placing most of the mass of the station at one end of the pole, the pole length to the Mars habitat would still need to be 84.4 meters from the center of mass of the station, but the pole length extending the opposite direction could be much shorter. The extra mass could consist of the station's batteries, rocket engines, fuel, water, solar, panels, radiators, etc. It might also contain a lunar habitat, using the shorter radius of 36.5 meters, thus allowing testing of both Martian and Lunar gravity effects in one station. A crude layout of such a station, which I am calling "the Dog Bone", is shown below:

The martian habitat would be on the left end of the station's central boom, and the lunar habitat would be on the right end of that boom. The extra pod to the right of the lunar habitat represents the extra weight of various station components which offsets the station's Center of Mass or Center of Gravity (I'm using the terms interchangeably here. Sorry, sue me if you must.). If it can be shown that subjects can tolerate a higher RPM, then the central boom of the station shrinks significantly.

I don't think such a station need be incredibly expensive to build. The central boom is the most awkward piece of the station, and I believe it could be assembled in orbit. The boom is, after all, not much more than a big aluminum pipe. Assuming 3 boom sections could be put in orbit per flight, with each boom being approximately 13 meters long, it would take about 3 flights just for the boom sections, potentially two more flights for habitat sections, and two more flights for the "counterweight" and docking interface, so somewhere around $480 million for launch costs for the station. Assuming my numbers are off by a factor of three, this is still a very inexpensive space project, and the payoff for having such a station is huge.

Friday, March 06, 2015

Dawn Spacecraft is Ceres-ly Orbiting a Dwarf Planet

It has been announced that the Dawn Spacecraft has successfully transitioned to orbiting around the dwarf planet Ceres. Someone thought it amusing to label this accomplishment as a first, as Dawn is now orbiting a dwarf planet, rather than orbiting some other type of celestial rock, which we have orbited before. But seriously, it wasn't until 2006 that Ceres was even referred to as a dwarf planet. Before then, it was called an asteroid, and an orbit of an asteroid was already achieved on February 14th, 2000 (Mission was NEAR, the asteroid was 433 Eros). With any luck, the IAU will redefine Ceres as something like a dormant, mega-comet at some point, and a new NASA mission can be sent there to claim yet another astronomical first.

The real first is that Dawn has accomplished is to achieve orbit at two separate celestial destinations during one mission (Vesta and now Ceres), and this is due to its use of ion propulsion. Ion engines are about ten times more efficient than conventional bi-propellant engines, when it comes to using fuel. As a result, they allow spacecraft a greater wander range than a conventional engine would allow. In this case, increased engine performance results in much smaller fuel tanks, which results in a smaller spacecraft with more range.

Ion engines put out a miniscule amount of thrust -- it takes the Dawn spacecraft 4 days to accelerate from 0 to 60 miles per hour, but unlike chemical propulsion, Dawn can maintain that thrust continuously for months at a time. The Ion engines are remarkably simple and sturdy, and can run for upwards of five years at full thrust without breaking.

Now that Dawn has arrived at Ceres, we will get the chance to investigate this peculiar planetoid. So far, scientists have speculated that Ceres has a thick crust of ice surrounding a rocky core. It appears as though Ceres' surface is coated with a fairly thick layer of dust, and there appears to be some activity that has revealed the underlying ice layer. We should be in for an exciting several months of science ahead.

Friday, February 27, 2015

Spock: End of an Era 2015

My son called me with the saddest news this morning. Leonard Nimoy, directory, artist, and actor indelibly linked to the character Spock, from Star Trek the original series, has died. He was 83 and suffering from end-stage Chronic Obstructive Pulmonary Disease (emphysema) when he was taken to the hospital on the 19th of February with chest pains. On the 23rd, he tweeted, "A life is like a garden. Perfect moments can be had, but not preserved, except in memory. LLAP" Leonard was born in Boston, Massachusetts in 1931 to Russian Jewish parents. He started acting at the age of 8 in children's and neighborhood theater. His parents encouraged him to take up a more stable career than acting. His father even encouraged him to learn to play the accordian, rather than act. Fortunately, his grandfather intervened at that point and steered young Leonard towards the acting life. Thus the world owes Leonard's grandfather a huge debt of gratitude on at least two counts.

Leonard served in the Army from 1953 to 1955. He took on various parts in TV shows and movies starting in 1951, often in westerns, police dramas, and similar action roles. In 1964, Leonard acted in a pilot for a futuristic, space-age action/drama TV show that was to become Star Trek in 1966. Although the original Star Trek series only lasted for three seasons, it left an indelible mark on the American psyche, as well as on the careers of all of the actors who were involved with it, most especially for Leonard Nimoy and William Shatner. Leonard wasn't entirely keen on being type-cast and had somewhat of a love/hate relationship with Spock over the years. It should be noted that some of his other works, such as this, this, and this, were mercifully overshadowed by the character Spock.

He was a great man though, and will be greatly missed. For more insight into Leonard Nimoy, here are links to an interview he did back in 2012..

Hero Complex Part 1
Hero Complex Part 2


Thursday, January 08, 2015

SpaceX Redux on Saturday One Dark Thirty

"What?!?" you exclaim, as SpaceX scrubs the launch at 3AM PST last Tuesday, "can't Space-X get anything right?"

Why yes, they can. This would've been the 13th Falcon 9 launch, had everything gone off without a hitch, but hitches happen, especially when the vehicle in question has only flown only a hand full of times. To me it's far better to abort a launch and delay the next launch attempt for a few days rather than go ahead and launch and have Dragon not make it to orbit, thus delaying the arrival of the CRS delivery to the space station by several months.

The launch has now been rescheduled for early Saturday morning at 4:45AM EST/1:45AM PST, with livecast beginning at 4:30AM EST/1:30AM PST. You can find more info here with the webcast being covered here. Enjoy!

And Now on a more Somber Subject

By now, most everyone has heard of the news of the attack on the offices of the French satirical magazine "Charlie Hebdo". This event has hit me especially hard. The attack on Charlie Hebdo was both a tragic loss of life and a global attack on free speech and a free press, and therefore an attack on every blogger, video maker, writer, commenter, and any person who expresses an opinion out loud, in short, all of us.

We built our country (the United States) with the expressed safety of our rights being paramount, and we expressed that in the Bill of Rights, which is a list of the first ten ammendments to the U.S. constitution, and which established the rights of the citizens. The first ammendment and one might conclude the most important ammendment of that document guarantees every citizen freedom of religion (and freedom from a particular religion), freedom of speech, and freedom of the press. So that is why I have changed my avatar to "Je Suis Charlie" in honor of the lives lost in Paris, and as a reminder that today, we are all Charlie.

Monday, January 05, 2015

Space-X CRS-5 to Barge Its Way into History

Space-X plans to launch it's 6th visit to the ISS tomorrow morning starting at 6AM EST/3AM PST. The launch can be viewed live on If all goes well, this launch will be followed shortly by an attempt to land the first stage of the Falcon-9 onto a ocean-going barge parked out in the Atlantic Ocean. Space-X has been incrementally gearing up for this goal over the course of a number of Falcon 9 launches and experimental flights using their Grasshopper test vehicle. The purpose of this test is to reduce the cost of spaceflight by re-using the major components of the rocket vehicle.

Friday, December 19, 2014

Nifty Video of Orion Re-entry from Inside Orion

Not much news today related to space, but this video of the Orion spacecraft re-entering was pretty cool. In other news, Sony corporation demonstrated a complete lack of spine in their decision to forego release of "The Interview". I am profoundly bummed. "The Interview" and "The Hobbit: Battle of the Five Armies" were my two must-see holiday movies.

Wednesday, December 10, 2014

Congratulations to NASA on Orion EFT-1 Mission Success

I'd like to congratulate NASA for a successful flight of the Orion capsule. The Delta IV Heavy launched from Cape Kennedy at 12:05 UTC on December 5th (4:05 Pacific Time/7:05 Eastern), did two orbits around the Earth, and then splashed down in the Pacific Ocean off of the coast of Baja California. On the second orbit, the capsule was boosted to 3700 miles above the Earth prior to re-entry to simulate a return from deep space. The Orion capsule's re-entry velocity was about 20,000 mph/32,000 kph. This is a bit higher than capsules returning from the ISS (with typical re-entry speeds in the 17,500 mph/28,000 kph range), and less than the speed of the Apollo spacecraft returning from the moon (24,750 mph/39,600 kph). The spacecraft splashed down about four hours after launch, and has since been recovered by the US Navy.

While this was a great demonstration flight, I don't agree with some NASA people who say this is our future spacecraft to Mars. If all goes well, and there are doubts that all will go well, Orion won't be flying again for at least the next two years. The next flight is scheduled for 2017, when it and the SpaceX crewed Dragon vehicle will hopefully start sending crews to ISS under the Commercial Crew Transportation Capability (CCtCap) contract. SpaceX, meanwhile, will be flying at least 10 more Dragon missions to ISS and space in general. So SpaceX will have quite a bit more experience with their craft before Orion flies again.

Also, it's important to keep in mind that Elon Musk himself is fixated or perhaps obsessed with going to Mars, and he is not dogged by temperamental congresses and their hot/cold space program funding cycles. I wouldn't be at all surprised if the astronauts on the first NASA Mars mission are welcomed to Mars by Elon and members of the SpaceX staff when they get arrive their.