OrbitalHub

Credits: NASA

In a nutshell, it is really tough! The higher you go, more bad things can happen to you… the increasingly rarefied air, freezing temperatures, ionized atoms, radiation, and space debris make life challenging. So, besides thinking of how to place spacecraft in orbit, engineers must consider all of the factors mentioned above (and much more) when designing a spacecraft.

The space environment (the vacuum, the radiation, the space debris, etc.) definitely poses big challenges to spacecraft design engineers. From 1971 to 1989, more than 2,700 spacecraft anomalies related to interactions with the space environment were recorded. These interactions with the space environment are called space environment effects and the changes in the space environment define what is called the space weather. Believe it or not, there are dedicated programs aimed at developing the ability to predict these changes in the same way the weather forecasting does for terrestrial weather. The Space Weather program was formed in the mid-1990s by the National Science Foundation (NSF). The Europeans developed a similar program under the umbrella of the European Space Agency (ESA).

The space environment effects can be grouped into several categories. Such categories include: vacuum, neutral, plasma, radiation, and micrometeorid/orbital debris. So, basically, we can discuss the effects of the vacuum environment, the neutral environment, etc. Each one of these environments interact with the subsystems that comprise a spacecraft: the propulsion system that provides the means of maintaining a certain orbit or attitude, the electrical power system that provides power to the rest of the subsystems onboard, the thermal control system, the attitude and orbital determination and control system, etc.

The vacuum environment imposes challenges when it comes to designing the structure, choosing the materials, and defining a strategy for thermal control. The pressure differential between the inside and the outside of a manned spacecraft is tremendous (around 350 km above the surface of the Earth, the pressure is ten orders of magnitude less). The lack of atmosphere translates into the fact that the spacecraft will have to deal with solar ultraviolet (UV) radiation (the UV radiation is energetic enough to degrade material properties). Also, the spacecraft can only cool itself by conduction or radiation.

Credits: NASA

Even if very rarefied, the neutral atmosphere in low Earth orbit is dense enough to cause a significant atmospheric drag force. The atoms can physically sputter material from surfaces and even cause erosion. All these mechanical and chemical interactions depend on the atmospheric density.

In low Earth orbit, the solar UV radiation ionizes the oxygen and nitrogen atoms. This environment, known as the plasma environment, can give rise to very interesting effects, like spacecraft charging and arcing between regions of differing potentials.

By far, the most dangerous environment in Earth orbit is the radiation environment. In the regions of charged particles, known as trapped radiation belts, particles with energy levels in the order of MeV pass through the surface layer and interact with the materials inside the spacecraft. Present shielding technology cannot protect living organisms inside a spacecraft in these regions.

Micrometeoroids and orbital debris are a cause of great concern to spacecraft design engineers and spacecraft operators as the kinetic energies associated with impacts at orbital velocities are very high. The main effect on spacecraft in this case is the physical damage upon impact. Other effects include surface erosion, ejecta resulted from impacts, changes in thermal control properties, and generation of electro-magnetic impulses (EMIs).

As most of the characteristics of the space environment were determined by remote observations or during short duration missions, one long duration mission was necessary to verify and validate these measurements.

In April 1984, the Space Shuttle Challenger placed into low Earth orbit (LEO) a spacecraft carrying a number of experiments for the purpose of characterizing the low Earth orbit environment. The spacecraft (known as the Long Duration Exposure Facility, or LDEF for short) was a twelve-sided cylindrical structure three-axis stabilized in order to ensure an accurate environmental exposure. The spacecraft was supposed to spend one year in orbit, but just before the planned retrieval, the Space Shuttle fleet was grounded as a result of the Challenger accident on January 28, 1986.

The spacecraft was returned to Earth by the Space Shuttle Columbia in January 1990. After almost six years in low Earth orbit, the results of the experiments onboard the facility contributed a great deal to the understanding of interactions between artificial objects and the environment in low Earth orbit.

You can find all the above in much more detail in Alan Tribble’s book The Space Environment – Implications for Spacecraft Design. Alan Tribble presents an excellent account of the effects the space environment can have on operational spacecraft. The book offers a unique perspective, as it combines the study of the space environment with spacecraft design engineering. .

Alan Tribble spent over ten years designing spacecraft. He is a technical project manager in the International Software Defined Radios group for Rockwell Collins.

Credits: NASA/CSA

Canadian astronaut Chris Hadfield will take command of the station during the second half of his third space mission. Hadfield will launch aboard a Soyuz rocket in December 2012, and spend six months on the station as part of the crew of Expedition 34/35. He will return to Earth in a Soyuz capsule in June 2013.

Hadfield is the only Canadian to board the Russian Mir space station, in 1995, during his first space flight, while he served as Mission Specialist 1 on STS-74. He is also the first Canadian mission specialist and the first Canadian to operate the Canadarm in orbit.

His second space flight was onboard STS-100, where he served as Mission Specialist 1. STS-100 was the International Space Station assembly flight 6A, which delivered and installed the Canadarm-2 on the station. During this mission, Hadfield performed two spacewalks.

Chris Hadfield also served as Director of Operations for NASA at the Yuri Gagarin Cosmonaut Training Centre in Star City, Russia; as Chief of Robotics for the NASA Astronaut Office at the Johnson Space Center in Houston, Texas; as Chief of International Space Station Operations; and as the Commander of NEEMO 14, a NASA undersea mission to test exploration concepts living in an underwater facility off the Florida coast.

The official announcement was made by the Canadian Space Agency. Chris Hadfield’s biography is also available here.

Credits: CNES

Since the launch of Sputnik-1, on October 4, 1957, some 4,600 launches have placed more than 6,000 satellites in orbits around Earth.

All these activities have created a cloud of particles orbiting the Earth, which is referred to as orbital debris.

The majority of these particles are fragments from explosions and collisions (such as the Chinese Fengyun-1 ASAT test in 2007, and the collision between Iridium 33 and Cosmos 2251 in 2009). Some of them are spent rocket stages and defunct satellites. The total mass in orbit has been estimated to 5,800 tons.

As the ejecta generated in explosions and collisions have a wide range of velocities, the evolution of the particle cloud following the event can evolve in ways that are sometimes hard to predict, as some of the particles can disperse into orbits that are dissimilar to the original orbits.

Credits: NASA

To make things more complicated, the particles comprising the orbital debris environment are quite hard to detect. Some of them are impossible to detect due to technological limitations (present equipment is capable of tracking only objects larger than 1 cm in diameter in low Earth orbit and larger than 50 cm in diameter in geosynchronous orbit) or simply because they have orbits that are out of the range of tracking stations (such as highly elliptical and high inclination orbits with the perigee situated deep in the Southern Hemisphere – the Molniya orbits).

Even if most of the particles orbiting the Earth at velocities in the range of 8-10 km/s (or 28,800-36,000 km/h) are less than 1 cm in size, the kinetic energies associated with impacts at orbital velocities make them a source of great concern.

Just to get a sense of the effects that even small particles with velocities in the order of 10 km/s can have on space structures, if we assume a density of 1 g/cm³, a particle as small as 0.1 mm can cause surface erosion, and a particle 1 mm in size can inflict serious damage. A 3 mm particle moving at 10 km/s has the kinetic energy of a bowling ball moving at 100 km/h. A 1 cm fragment has the kinetic energy of a 180 kg safe. It is easy to visualize the effects of an impact with such an object on an operational satellite or a space station parked in low Earth orbit.

To find out more about orbital debris you can visit the NASA Orbital Debris Program office website.

Credits: NASA

The Orbiting Carbon Observatory 2 mission is scheduled to launch in February 2013.

The previous spacecraft failed to reach orbit on February 24, 2009, after being launched on top of a Taurus XL launch vehicle from Vandenberg Air Force Base in California.

The OCO spacecraft will make global CO₂ measurements from space, quite useful as scientists are trying to understand the global carbon cycle in order to be able to make predictions of future atmospheric CO₂ increases.

NASA awarded the launch services contract to Orbital Sciences Corp. of Dulles, Virginia. OCO-2 will be launched by a Taurus XL 3110 launch vehicle from Vandenberg Air Force Base.

We quote from the NASA press release:

“OCO-2 is a NASA’s first mission dedicated to studying atmospheric carbon dioxide. Carbon dioxide is the leading human-produced greenhouse gas driving changes in the Earth’s climate. OCO-2 will provide the first complete picture of human and natural carbon dioxide sources and sinks, the places where the gas is pulled out of the atmosphere and stored.”

You can find more information about the Orbiting Carbon Observatory on NASA’s website.

Credits: NASA

During the Apollo 13 mission, after the explosion of an oxygen tank crippled the Service Module, the astronauts had to abandon the third Moon landing. The Apollo 13 crew used the Lunar Module as a lifeboat. The Lunar Module was jettisoned by the Command Module just prior to re-entry.

A team of engineers from the University of Toronto Institute for Aerospace Studies (UTIAS) played a key role in the separation of the Lunar Module and the Command Module. As the tunnel connecting the two modules was pressurized, the UTIAS team had to determine how much pressure was necessary to safely separate the modules. Not an easy task considering the fact that if there was too much air in the tunnel, the explosion that triggered the separation would have damaged the hatch of the Command Module, and the astronauts would not have survived the re-entry.

The Apollo 13 astronauts, Commander James A. Lovell, Command Module Pilot John L. Swigert, and Lunar Module Pilot Fred W. Haise, were recovered by the U.S.S. Iwo Jima in the South Pacific after splashing down on April 17, 1970.

If you are in Toronto next Tuesday, on April 13, 2010, you can meet some of the members of the UTIAS team at the Canadian Air and Space Museum. They will receive the Pioneer Award for their role in the Apollo 13 rescue.

Credits: NASA/Kim Shiflett

On March 6, 2009, the Delta II launch vehicle carrying the Kepler spacecraft lifted off from Launch Complex 17-B at Cape Canaveral Air Force Station in Florida.

In May 2009, Kepler started to hunt for other Earth-like planets in our galaxy. The technique used by Kepler to discover exo-planets is called transits. The large field of view of the Kepler telescope simultaneously captures the light of a very large number of stars in the Cygnus and Lyra constellations.

Kepler scientists already announced the discovery of five exoplanets named Kepler 4b, 5b, 6b, 7b, and 8b. The data collected by Kepler was also used to detect the atmosphere of the HAT-P-7b giant gas planet.

Kepler is expected to be operational until at least November 2012. Scientists hope to discover exo-planets in the habitable zone of other stars. The habitable zone is a region around a star where water can exist in liquid form on the surface of a planet. You can find more information about Kepler on NASA’s Kepler Mission website.