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Friday, October 31, 2014

Through footless halls of air

Virgin Galactic SpaceShipTwo failed today under rocket power, killing one astronaut and seriously injuring another. This is three independent commercial flight failures under rocket power in a month and a half, SpaceX, Orbital and now Virgin. Really, we need to find a better and safer means of getting into space. And now, the pressure on NASA's Orion/EFT-1 flight next month has become enormous.

The test pilot who was killed today has not yet been named in the press, but may he or she rest in peace.

Thursday, October 30, 2014

Orion Rising

The first Orion space capsule is complete, today. The United States of America once again is in possession of a crew-rated spacecraft, the first since the retirement of the space shuttles. In the words of Joe Biden, this is a BFD.

Russian Roulette

The malfunction and then detonation of the Antares/Cygnus cargo spacecraft at Wallops on Tuesday is now being tied to the use of refurbished 1960s Soviet vintage AJ26 rocket engines. I'm not going to speculate on whether or not this is the case; I suspect that the age of the engines had very little to to do with the accident, but I have no evidence to back this up either way.

What is more conclusive is that chemical rockets remain A) the only means we have of launching any payload into low earth orbit and beyond and b) dangerous as hell.

A little bit of sloppy number crunching, looking just at the space shuttle program. Five orbiters totaling some 130 launches, two of which failed catastrophically. That's about a 1.5% failure rate. Scaled up to commercial aircraft, that's about 20 major airline disasters every single day. At Seattle-Tacoma International Airport. By itself.

This is a serious problem for true commercial spaceflight. If the ground crew cheered every time a Boeing 737 took off or landed safely, nobody in their right mind would fly in Boeing 737s. For routine commercial spaceflight to be feasible, we need something which works reliably every time it flies. Highly volatile chemical rockets probably are not the answer.

One possible answer floating around (sorry) is lighter than air craft. The idea of riding a dirigible into space, at first glance, seems a little absurd. But John Powell of JP Aerospace has demonstrated how a hypersonic dirigible could reach the International Space Station, and beyond. Another possibility is using less volatile hybrid (HTPB/N2O "rubber and laughing-gas") rockets, but these have yet to reach the 100 km Kármán line, much less low earth orbit. But better propellants and/or oxidants may be found, which are still reasonably stable. Until then, what we have looks less like science than theology. And if part of your routine flight-plan includes "pray real hard," you're not yet ready to fly grandma to the moon.

Thursday, October 16, 2014

Mars One: Bouncing the Reality Check

Today a group of engineering students from MIT published a very well-researched feasibility study about Mars One, the Dutch plan to put a human colony on Mars by 2024, for a reality TV series.

The study is good, and solid. It basically comes down to "they don't know what they don't know" (the headline about the study was "Humans on Mars One mission would start dying in 68 days" which sums it up pretty well). You can read all of the MIT feasibility study here, it's a pretty interesting read.

The elephant in the ballroom here is that Mars One, to date, has raised a grand total of about $600,000 worldwide. With that, they can buy one pretty nice brand-new single engine Cessna, and maybe fuel, a bag of donuts and a thermos of coffee for the flight to wherever a Cessna 172 can get to from Amsterdam.

Tuesday, October 14, 2014


This Sunday the Oort Cloud comet Siding Spring (also called Comet C/2013 A1) will pass within 140,000 kilometers of Mars. This is about half the distance from the earth to the moon, and much, much closer than any known comet fly-by of earth. It will be observed by rovers on Mars and spacecraft in Mars orbit, as well as terrestrial land-based and space-baced telescopes. Currently orbiting Mars are the Mars Reconnaissance Orbiter (MRO), MAVEN, Mars Odyssey, the ESA Mars Express, and India's Mars Orbiter Mission (MOM). It is only by blind, dumb luck that this one-in-a-million flyby is happening at a time when we are actively surveying Mars for eventual human colonization. This should be a very interesting week.

Friday, October 3, 2014

Cargo to Crew

This is the ULA Delta IV Heavy that will launch the Orion spacecraft on its uncrewed maiden voyage this December.

This raises the issue of the difference between rockets for cargo flights into low earth orbit versus crewed flights to the same destinations, and specifically why we can't just use the same rockets for what is nearly the same job. It turns out that modifying an existing cargo rocket for crewed flight is a fairly involved exercise.

The reason is safety, mostly. Rockets have an unhappy propensity for exploding, so any crewed vehicle must be able to safely escape an explosion. Part of the solution is a Launch Escape System, which is simply a small rocket on top of the spacecraft to pull it away from the main engines and fuel tanks in the event of a catastrophic failure. Here is an example, with an Apollo space capsule.

Cargo rockets take the shortest, fastest and simplest (hence closest to vertical) route to orbit that their engines allow, with little consideration for the massive changes in g-forces that the cargo is subjected to. Humans need a slower and gentler ascent. Also, cargo rockets maximize the distance they coast upward unpowered between stages, and by launching essentially vertically the exhaust remains below them. Neither of these are problematical so long as the launch proceeds normally. However, if the LES needed to deploy at certain parts of the launch trajectory (such as at the top of one stage's coasting before the stage above it ignited, or the first few seconds of a launch when the huge exhaust fireball is below the rocket), the LES would be unable to safely extract the spacecraft. These time intervals in which the LES cannot launch the crew safely away from an exploding rocket are called "black zones." Every crewed rocket has some, but the goal is to minimize both the amount and duration of these. One method for accomplishing this, for example, is to launch the rocket in a lower parabola so that for most of its flight to orbit, the spacecraft does not have its own exhaust gasses below it.

The currently used Delta IV, Atlas V and SpaceX Falcon rockets are all presently being modified for commercial crewed flights. Each of these rockets will be discussed here in greater detail, as this series progresses.