Catching up with a 17,500 mph Space Station

When the Antares rocket took off from NASA's Wallops Flight Facility in Virginia this past Thursday, its Cygnus payload didn't go straight to the International Space Station. The fact is that very few vehicles destined for the ISS go straight from launch to the station. A typical trip to the station is a multi-day voyage and it's only been in the past year that manned flights have begun taking an expedited path and timing that can get crews there within 6 hours of launch.

To understand why we don't usually go from ground to station in one quick trip there is a key concept to know first: in orbit, speed equals altitude. 

The basic concept of an orbit is that an object is moving parallel to the surface of the Earth. Gravity is still pulling on that object so it's in a constant state of "falling", but the object is moving so quickly that by the time it reaches the horizon the surface of the planet has curved down and away from the object. So if that object, such as a Cygnus capsule, keeps going fast enough it will "fall" indefinitely and remain in orbit around the planet!

Hopefully this terrible illustration above helps to visualize the concept. As a projectile (the black circle) moves faster it travels farther along the horizon before finally falling to the ground (the black line).

This second terrible illustration shows that with enough speed the projectile would move forward and downward at the same rate as the surface of the planet, creating an orbit. Because of this concept we have to operate differently in space when trying to go "up", or away from the planet. A spacecraft can't just point away from the planet and fire its engine because it would actually slow down. What it needs to do is fire its engine in the direction of travel! If it goes faster it won't just move parallel to the horizon but actually overshoot the path of the ground. Hm...this may seem confusing. Perhaps its time for yet another awful illustration?

On the left side we see an object orbiting a blue planet. To get that object farther from the planet it fires its engines, pushing it in the direction of the arrow. Eventually it moves so quickly that its path (the red curved line) gets wider than it was before and it moves outward to the second orbit seen on the right side of the diagram.

Now that you have this concept in mind I can tell you that the reason why a vehicle doesn't usually go directly to its destination orbit is because a higher orbit means a faster orbit and a faster orbit means a bigger rocket to give it the "get up and go." Bigger rockets are more complex, heavier, and more expensive so their use is a potential hindrance to regular and affordable launches. But wait! Science to the rescue! Once the vehicle is in orbit it has shed the weight of the rocket that carried it there and its in a vacuum so there's no air resistance. This means a rocket motor is MUCH more efficient in space than in our atmosphere, allowing the Cygnus, in this case, to use its own on-board rocket motor to fire several times and incrementally increase its orbit, which during the ongoing Orb-1 mission calls for 5 "Delta V" (change in velocity) burns that take the vehicle from its original orbit of 134 miles to 226 miles. This stops Cygnus four miles beneath the space station where it then makes a slow, controlled approach. That approach occurred this morning (Jan 12) around 6:00 am EST and by 8:00 am the astronauts aboard the station used the Canadarm 2 robotic arm to grapple and reposition the vehicle for final docking.

Antares, International Rocket for an International Station

One of the two rockets being put to use these days in resupplying the International Space Station is the Orbital Sciences Antares, named for a star in the constellation Scorpius. Antares is a two-stage rocket intended to carry the Cygnus resupply vehicle (a more detailed post can be written about that if there's interest).

Antares is a multinational project, assembled from components built in 4 different countries on 3 continents, which is incredibly appropriate for a vehicle intended to resupply an international scientific outpost. So let's check out the parts from the bottom up:


 AJ-26 Rocket Engines - The part that really makes the thing get up and go! Antares has two of them and when they were originally built they were called NK-33's. These engines have a pretty interesting history because they were built in the late 1960s. 
By the Kuznetsov Design Bureau. 
In the Soviet Union. 
For the N1...their MOON ROCKET!

That rocket was unsuccessful overall but these engines were so advanced at the time that they're still up to modern performance standards with some relatively minor upgrades from the Aerojet Rocketdyne company in California, who has a large enough stock of those motors to supply the Antares for all eight contracted flights to the ISS with some to spare. Antares has two engines that are gimballed, meaning they're mounted in a way that they can be tilted to steer the rocket.

First Stage Fuel Tanks & Structure - The bulk of the rocket is made up of this first stage structure that contains a fuel tank for liquid oxygen (takes up about 2/3 of the length) and a fuel tank for RP-1, a modified form of kerosene. There are also helium tanks built into the fuel tanks that are used to force the oxygen and kerosene out of their tanks and into the engine as quickly as possible. This major section is designed and built by Yuzhnoye Design Bureau in the Ukraine, based in large part on the Russian Zenit rocket.

Interstage Assembly - This is the section that connects the first stage to the second and helps keep the rocket on the right course as it gets close to orbit by operating thrusters, small rockets used to control direction, as the rocket cruises between stages. Built largely from US-based Orbital Sciences' flight computers used on the Pegasus air-launched rocket, this hardware is considered exceptionally reliable which is great because if the rocket can't stay on course then there's no point in launching at all.

CASTOR® 30B Second Stage Motor - Unlike the first stage motors, the second stage is a solid-fueled motor built by Alliant Techsystems (ATK), a manufacturer from Utah that also built the Solid Rocket Boosters for the Space Shuttle. At a recent tour of NASA's Wallops Flight Facility a representative of ATK stated that the fuel formula they're using for Antares is a drastically better than the shuttle fuel which was designed in the 1970s.

Cygnus - The only part of the entire launch that will make it to orbit is this capsule-type spacecraft. It's made of two sections, the Pressurized Cargo Module (PCM) and the Service Module (SM). The SM is the "brains" of the vehicle, containing the solar panels, the rocket engine and thrusters, communications systems, and the environmental controls for inside the PCM, which is where the supplies and hardware meant for the station are stowed away. The SM is based largely on satellite hardware developed and built by Orbital Sciences in the United States. The PCM, on the other hand, was developed and built by Thales Alenia of Turin, Italy, sharing its design heritage with many sections of the space station and the Automated Transfer Vehicle (ATV) built by the European Space Agency.

 All those pieces from all those countries come together at the Horizontal Integration Facility at NASA's Wallops Flight Facility where they become the Antares rocket, one of America's newest launch options that is making low-Earth-orbit resupply an economic and routine process.

I hope you enjoyed this explanation of the Antares rocket and if you have any questions, comments, or suggestions then go ahead and leave a comment below! As always, thanks for reading!

Second Space Age - Orbital Sciences Corporation

If you live on the east coast of the United States then it's likely that over the past year you've been introduced to the work of one of the major players in the Second Space Age, Orbital Sciences Corporation. (If you don't live in that area or have never heard of them, please read on anyway!) They've built and operated the various rockets that have been flying out of NASA's Wallops Flight Facility on the eastern shore of Virginia. Their launches have caught the attention of the public lately thanks to their frequent night-time launch windows (the short time that physics dictates as just the right time to launch a particular mission).

Orbital Sciences is one of two companies contracted by NASA to deliver supplies and new science experiments to the International Space Station under the Commercial Orbital Transportation Services (COTS) program. (We'll discuss the other company in the near future.) Based in Dulles, VA, Orbital Sciences was founded in 1982 and has developed an impressive reputation in the small- and medium-class satellite business, having produced about 140 satellites with two primary focuses. The first is communications and the second is remote sensing which means using instruments aboard the satellite to make measurements and observations of Earth which can be used in scientific studies, military operations, and commercial uses like urban planning and farming.

They've also been building and flying rockets very successfully, and interesting ones at that! Their Pegasus rocket has a triangular wing and is launched horizontally after being dropped by a Lockheed L-1011 carrier plane at 40,000 feet. This has the great advantage of getting the rocket above the thickest part of the atmosphere so the rocket experiences less resistance and it's above most of the weather so the odds of being able to launch are increased greatly.

The rockets that have been catching the public's attention, however, are the Minotaurs (like the one used to launch LADEE a few months ago) that Orbital Sciences have created by acquiring decommissioned US Air Force Minuteman and Peacekeeper missiles and using them as the first two stages then mounting their own flight-proven rockets and computers on top with their satellite payloads. This gets to the heart of what Orbital Sciences does often and does well: assembling pieces that have excellent success rates and are readily available. In this way they are able to put together launch vehicles that are safe, reliable, capable, and cost-effective. That is a crucial ability for any company hoping to hold a position as major player in the satellite launch world and especially when helping pioneer commercial cargo service to our space station.

The next entry will be about Orbital Sciences' newest rocket, the Antares, which will be launching this Wednesday, January 8th, and later in the week I'll introduce you to do Cygnus cargo vehicle that is serving as one of two  commercial resupply vessels for the International Space Station.

If you have any questions about Orbital Sciences or anything referenced here please leave a comment!

This Week in Spaceflight, January 5-11 2014

Here's a rundown of the launches that are scheduled (or rumored!) to happen this week.

The Second Space Age: An Overview

Whether the general public knows it or not, we're in the middle of something amazing. We're living through a "Second Space Age." These past couple years, new rockets and new spacecraft have been coming online and entering service as spaceflight in the United States shifts from government-based to commercially-operated. During the Space Shuttle era, NASA owned and operated their fleet of vehicles and over the shuttle's 30-year history that ownership and operation proved to be more costly than anticipated. While it allowed us to build the International Space Station, the next necessary step to permanent human habitation off this planet, the complex and maintenance-heavy shuttle fleet also drained funding away from new vehicle development. So many people were screaming out to the whole of the internet when the shuttle fleet was retired, fearing that NASA was closing up shop, giving up on sending people into space...but the reality is the exact opposite. NASA had cleared up an immense portion of their ever-declining budget to move on to the next target: exploration beyond Earth orbit.

NASA's new capsule, the Orion, has been making steady progress towards providing us with a vehicle that can take us to asteroids, the moon, and beyond. Most people seem to think it's still just an idea, a concept on a drawing board, but in September of this year the Orion is scheduled to make its first unmanned trip into space. Several years from now it will ride skyward with a crew atop one of the newest and largest rockets in the world: the Space Launch System (SLS).

This rocket makes use of flight-proven hardware such as solid rocket boosters and Space Shuttle main engines (which were so reliable that they were reusable) while also adding in 21st century technology such as composite structure fuel tanks that will be lighter and stronger than the old aluminum alloy tanks. Less weight there means more weight that can go into space. More bang for the buck, figuratively and literally.

But what about the Station? It's still there and still needs to be resupplied and crews exchanged every few months, right? Of course, and this is where the Second Space Age really comes into being. In the short term we've been able to ride with our partners from Russia, who took up the task of manned flight with their Soyuz spacecraft, a vehicle with an impressive safety record over its nearly 50 years of operation. (Don't worry, it's had many upgrades and modifications since the old days!) That's the beauty of an International Space Station, you can work with others to assure continued service.

A lot of people in this country, however, disapprove of sending astronauts (and dollars) to another country to get to space. The long-term side of the plan has been for NASA to work with private corporations to develop several different spacecraft and rockets that will be able to deliver crew and cargo to the ISS, in a way handing over the "routine" aspect of space to private companies that can compete to do it efficiently and at competitive costs. NASA has shared its vast technical knowledge with US-based aerospace corporations and some of those companies are already providing results. 

SpaceX's Dragon and Orbital Sciences' Cygnus have already made trips to the ISS under cargo resupply contracts and may just be a few years until we see private companies operating crewed spacecraft. And the day that a commercially operated, manned vehicle makes it to space will be a VERY big day.

So to summarize the future: private companies operate the rockets that put people into earth orbit and send cargo to the ISS, leaving NASA a bigger chunk of budget to do the bolder, more ambitious projects that take us away from Earth.


There's an impressive collection of companies and individual that are doing amazing things now and in the near-future. Through this "Second Space Age" series you'll be introduced to the new rockets, the new spacecraft, the companies that are building/operating them, and the amazing way it all fits together to expand humanity's ability to understand and navigate through our universe.

Any questions or feedback will be much appreciated. I want to write what you want to read about so let your opinions be known!