What are Space vehicles? by Pradhuman

 

What are space vehicles?

An Inside Look at the Space Shuttle

Hello readers, Pradhuman Here

In this blog, we will take a close look at the interior of the space shuttle, examining its crew compartment, payload bay, and rear engines. 

Introduction

The space shuttle was a spacecraft used by NASA for 30 years and completed 135 missions. Its last flight took place in 2011. The space shuttle consisted of three main components: the orbiter vehicle, the orange external tank, and the two white solid rocket boosters (SRBs). While the orbiter and SRBs were reusable, the external tank was not and had to be replaced for each mission. It's worth noting that many people refer to the entire assembly as the space shuttle, even though technically it is just a part of it. So, the terms orbiter vehicle and space shuttle are sometimes used interchangeably.

A Typical Mission

Let's take a look at a typical space shuttle mission. The shuttle would launch from the Kennedy Space Center in Florida. The two solid rocket boosters were crucial during the first two minutes of the launch. After that, they would separate and fall back to Earth to be recovered and reused in future missions. The three main engines would then take over for the next six and a half minutes. After that, the orange external tank would separate and burn up in the atmosphere. The main engines would become inoperable for the rest of the mission. The two smaller orbital maneuvering engines (OMS) would perform the final push to enter orbit. Once in space, the shuttle would orbit the Earth every 90 minutes at a speed of 28,000 kilometers per hour. The payload bay doors would be opened, and most of the time, the orbiter would be upside down to protect the astronauts from space debris. Most missions took place at an altitude of about 320 kilometers, but some reached up to 550 kilometers. This region is known as Low Earth Orbit, where all space shuttle missions occurred. At the end of a mission, the OMS engine would ignite to slow down the spacecraft, putting it on a trajectory to reenter the Earth's atmosphere. This phase is known as atmospheric reentry. Once close to the ground, the orbiter would glide to the runway. The wheels would be deployed, and the orbiter would land like an airplane. A red parachute was essential for slowing down the orbiter during landing.

Exploring the Orbiter

Let's take a closer look at the orbiter itself. Some have called it the most complex flying machine ever built. During most missions, it housed a crew of seven astronauts and remained in space for one to two weeks. It measures 37 meters long and 24 meters wide. To provide some context, the Apollo spacecraft that landed astronauts on the moon was much smaller. The orbiter's main structure is divided into three sections: the forward fuselage, the mid fuselage, and the aft fuselage. The aft fuselage contains the three main engines, which are the primary engines of the space shuttle. At the top are the two smaller OMS engines, which stands for Orbital Maneuvering System. The mid fuselage has the wings attached on either side, and in the center is the payload bay, also known as the cargo bay. This is where large objects were transported into space. The forward fuselage includes the nose cone and the forward reaction control system module. The small holes you see are thrusters that can help change the orientation of the shuttle in space. And most importantly, it houses the crew compartment at the bottom. The Thermal Protection System, also known as the heat shield, provides protection for the shuttle during atmospheric reentry. It is made up of over 27,000 silica tiles that shield the shuttle from extreme heat. The underside of the shuttle has three doors that enclose the landing gear. These doors open as the shuttle approaches the runway.

An Inside Look at the Crew Compartment

Now, let's explore the interior of the crew compartment, which is divided into three levels: the flight deck, the mid-deck, and the equipment bay. The flight deck contains the controls for piloting the orbiter. The commander sits on the left, and the pilot sits on the right. There are two additional seats just behind them, but they are usually stowed during the flight. At the back of the flight deck, there are more control panels. Two windows overlook the payload bay, and there are also two windows above and six windows in the front. The flight deck has a hole in the floor that leads to the mid-deck. There is a ladder, but in space, you can simply float to move between the two levels. The mid-deck is where the crew eats, sleeps, and performs some of their work. There are lockers for storing equipment and personal belongings. The sleeping quarters can accommodate three astronauts horizontally, while others sleep in bags attached to the sides. Sleeping in space is different from sleeping on Earth due to microgravity. The crew also has a galley for preparing food and a waste management system for dealing with bodily waste. The airlock is where astronauts put on their space suits before going out into the payload bay. Behind the lockers is the avionics bay, which contains equipment and computers for controlling the shuttle. Seats can be installed on the mid-deck for launch and reentry. The shuttle can accommodate six to eight astronauts, with most missions having a crew of seven: three on the mid-deck and four on the flight deck. Beneath the mid-deck is the equipment bay, which houses waste management systems, water tanks, pumps, and additional storage space. The crew cabin is the only pressurized part of the orbiter and the only place where astronauts can be without their space suits. The side hatch serves as the entrance and exit for the orbiter on Earth but is not used in space to prevent air from being sucked out. When it's time for some of the astronauts to go outside, they will use the airlock. For now, let's move on and explore the payload bay.

The Versatile Payload Bay

Once in orbit around the Earth, the payload bay doors are opened to expose the interior. Opening these doors is crucial as they contain radiator panels to help dissipate excess heat. The payload bay can accommodate payloads up to 18 meters long and 4.6 meters in diameter. It has been used to launch numerous satellites, including the Hubble Space Telescope. It has also been used to deploy modules for the International Space Station. During some missions, it carried a module called Spacelab, which provided additional workspace for scientific experiments. Astronauts could enter it by floating through the access tunnel. On the left side of the payload bay, there is a robotic arm called the Shuttle Remote Manipulator System, known as the Canadarm. It was a contribution from Canada and was controlled from the back of the flight deck. The Canadarm was used to grab and move payloads in space. It also served to assist astronauts during spacewalks. When astronauts put on their space suits and go outside, it's called an Extravehicular Activity (EVA). They put on their space suits in the airlock, open the hatch on the other side, and venture into space. In later shuttle missions, the airlock on the mid-deck was removed, and another one was installed in the payload bay, forming the Orbital Docking System. This allowed the space shuttle to dock with the International Space Station. Once docked, astronauts could freely float between the shuttle and the station.

The Engine Powerhouse

The shuttle's engines are located in the rear fuselage, forming the thrust structure with three openings for the main engines. These engines, called RS-25, are powered by liquid hydrogen and liquid oxygen. The fuels are stored in the external tank during launch, routed through the orbiter's belly, and fed back to the three engines. The fuel is extremely cold before being burned. Hydrogen is pumped along the side of each engine and then flows inside through many smaller tubes. This allows the fuel to serve as a cooling system before being burned. The three engines can be gimballed from side to side or up and down. This was done during launch to steer the orbiter. Above the main engines are the OMS engines, which helped provide the final push to enter orbit at the beginning of the mission and also slowed down the spacecraft at the end of the mission. The OMS system consists of two pods on each side of the vertical stabilizer, each with its own fuel and oxidizer tanks. You will also notice more smaller thrusters here, as well as underneath, which are part of the Reaction Control System (RCS). We saw earlier in the video that there are RCS thrusters at the front as well. The three RCS modules can work together to change the shuttle's orientation.

Aircraft-Like Features

The space shuttle shares several features with an airplane. It has wings, elevons, a body flap, and a vertical tail with a rudder that can also serve as an aerodynamic brake. These features are not essential in the vacuum of space but are crucial during the final stages of landing.