Friday, April 25, 2008
On April 19th, a Soyuz TMA spacecraft returned to Earth in the backup ballistic mode. This was the second Soyuz in a row to return in that mode. What does it all mean?
I flew on Soyuz TMA-5 to and from the International Space Station for Expedition 10. I was trained as the copilot, so I was intimately familiar with the spacecraft, it's operation, the backup modes and emergency procedures. Normally, the Soyuz descent module returns to Earth in an automatic mode, which flies a determined flight profile with closed-loop guidance. That is, the spacecraft is maneuvering to hit a defined point in the sky, where the parachute is deployed. In this maneuvering, the spacecraft profile is also designed to minimize the G-loading of the crew, usually to less than five G's. This was the case for TMA-5.
There are a number of failures that can cause a ballistic entry. In these cases, the spacecraft descent module spins and a rate of between thirteen and eighteen degrees per second, depending on the specific mode. There is no closed-loop guidance, the capsule is descending in a stable, but uncontrolled mode, to land where it is pointed. Thus, the footprint on possible landing sites is much larger. The crew is also subjected to higher G-loading, since the autopilot is not flying to minimize this loading. The maximum reported G on the last Soyuz was 8.2 G. This is a high level, but it is certainly tolerable. Anyone who flies on a Soyuz is run through the centrifuge to this level as a medical evaluation.
The real question is why did two Soyuz TMA's enter in ballistic mode? In the case of the first one, there appeared to be at least two failures, with a frayed wire causing a short being officially blamed for the downmoding of the spacecraft. We will have to wait for the incident report to find out what caused the latest downmode.
Is the Soyuz safe? I think so. I have met the people who work on the vehicles, I have seen for myself the environment in which they are created and processed. These are a dedicated group of specialists and they are very serious about what they do. The Soyuz design has been around for decades. It is the single most reliable spacecraft (with the largest number of flights) in history, to date.
I will be following this story closely.
Saturday, April 12, 2008
Do you remember Sputnik and Yuri Gagarin's flight? Gagarin became the first human to be launched into space in April 12, 1961. I was only about eight months old at the time, so I don't remember the actual event. But, I grew up during the space race and followed all of the missions once I was old enough to understand.
Gagarin's flight set off the chain of events that led to the Apollo program and the landing of Americans on the moon. Nobody has been back there since 1972. When will we be there again? Will the Constellation program survive under the new US Administration (no matter who wins the election)?
Sunday, April 6, 2008
Do you believe in COTS? By COTS, I mean the commercial program competition that NASA has committed about $500M towards. The idea is to stimulate commercial outfits to develop an unmanned resupply system for the International Space Station. Sounds good, but let's take a short look.
Two competitors won big NASA COTS awards in late 2006. One of them consequently missed funding milestones and had their award taken away. This award has now been given to a third company. Inside conversations with NASA folks usually involve rolling of the eyes and comments such as "we've been told to believe in COTS." At least one company (not selected for an award) has publicly accused NASA of "not being serious" about it.
I think it is a good idea, but I must admit to being skeptical. NASA is going to make any commercial outfit go through the same safety, testing and review process that a government vehicle must pass. This process is not simple, quick nor inexpensive. How will a commercial company be able to do all of that and still expect to make a profit?
As a reference point, the French ATV recently successfully docked to ISS. It was many, many years in development and in the end, the published program cost was 1.3 billion euros, or about $1.9 B!
What do you think?
PS: The photo above is of Progress 17P as it approached to dock with ISS during Expedition 10. I snapped this photo of it at a range of about 50 meters.