OrbitalHub

Credits: JAXA

HTV stands for H-II Transfer Vehicle. HTV is an unmanned spacecraft designed and built in Japan. HTV is designed to deliver supplies to the International Space Station (ISS).

The typical mission for HTV starts at the Tanegashima Space Center (TKSC) near Tsukuba, in Japan.

A H-IIB launch vehicle will inject the HTV on a low Earth orbit (LEO). After the separation from the H-IIB second stage, the transfer vehicle is able to navigate independently.

It will take approximately three days for HTV to reach the proximity of the ISS. During this time, it will maintain contact with the Control Center at TKSC (designated as HTV-CC) through the Tracking and Data Relay Satellite System (TDRSS). TDRSS is a network of satellites that allow a spacecraft in LEO to maintain permanent contact with the control center on the ground. HTV will use GPS to position itself at 7 km behind the ISS.

At this point, the berthing phase of the mission starts. HTV will approach the ISS within 500 m and use the Rendezvous Sensor (RVS) to move closer to the ISS. Reflectors that are installed on Kibo will allow HTV to maintain a distance of 10 m below the ISS.

Credits: JAXA

HTV does not have the capability to dock on its own to the ISS (as opposed to the European ATV), so the Canadarm2 robotic arm will be used to grab the transfer vehicle and berth it to the nadir side of the Node 2 module.

While the HTV is berthed to the ISS, supplies from the HTV’s pressurized section are transferred to the space station by the crew, and waste will be loaded from the ISS.

The cargo from the un-pressurized section will be unloaded using the robotic arm and attached either to the Exposed Facility of the Japanese Experiment Module (JEM) or the ISS Mobile Base System.

The HTV mission will end in a similar way to the European ATV: a destructive re-entry above the Pacific Ocean.

Here is some more background information about the HTV. The spacecraft is a cylinder-shaped structure 10 m long and 4.4 m in diameter. It has a total mass of 10,500 kg, of which 6,000 kg is cargo (divided into 4,500 kg pressurized cargo and 1,500 kg un-pressurized cargo). HTV can carry 6,000 kg of waste during the re-entry.

HTV consists of four modules: the Pressurized Logistics Carrier (PLC), the Unpressurized Logistics Carrier (UPLC), the Avionics Module, and the Propulsion Module. The UPLC carries the Exposed Pallet (EP), which can accommodate unpressurized payloads.

Credits: JAXA

The PLC is equipped with a Common Berthing Mechanism (CBM). This will allow the crew present on the station to enter the module in order to unload the supplies and load waste material.

The EP carried by the UPLC can be either Type I or Type III Exposed Pallets. The Type I EPs will carry payloads for the Kibo’s Exposed Facility (EF), while the Type III EPs will be used to deliver the Orbital Replacement Units (ORUs) to the ISS.

The systems in the avionics module enable HTV to execute the autonomous flight to the space station. The module also contains communication and power systems. The thirty-two thrusters installed on the propulsion module provide HTV with the capability to execute orbital adjustments and control the attitude during the mission.

HTV will add to the existing fleet of transfer vehicles that includes the Russian Soyuz and Progress spacecraft, as well as the European ATV. The first HTV mission is scheduled for late 2009.

For more information about HTV, you can visit the H-II Transfer Vehicle page on the JAXA web site.

Credits: Donna Coveney/MIT

MIT is developing an ion propulsion system that uses nitrogen as propellant. The new system is called Mini-Helicon Plasma Thruster.

Research and development of the Mini-Helicon is taking place at MIT’s Space Propulsion Laboratory (SPL).

“The Mini-Helicon is one exciting example of the sorts of thrusters one can devise using external electrical energy instead of the locked-in chemical energy. Others we in the SPL work on include Hall thrusters and Electrospray thrusters. This area tends to attract students with a strong physics background, because it sits at the intersection of physics and engineering, with ample room for invention,” said Manuel Martinez-Sanchez, director of the SPL and a professor in the Department of Aeronautics and Astronautics.

The Mini-Helicon has a simple design: a quartz tube wrapped by a coiled antenna, surrounded by magnets. The gas used as propellant is pumped into the quartz tube, where it is turned into plasma. The magnets confine, guide, and accelerate the plasma into an exhaust beam, which creates the thrust.

The Mini-Helicon design has its roots in a larger and more powerful propulsion system developed in collaboration with former NASA astronaut Franklin Chang-Diaz. A team led by Oleg Batishchev, principal research scientist in the Department of Aeronautics and Astronautics, did a theoretical analysis showing that components of the larger system could be used for different applications. The idea “was that a rocket based on the first stage [of Chang-Diaz’s system] could be small and simple, for more economical applications,” said Batishchev, who noted that the team’s prototype would fit in a large shoe box.

Batishchev notes that it could be years before the technology can be used commercially, in part due to certification policies through NASA and other agencies.

For more information about MIT’s Mini-Helicon, check out the MIT News Office website.

Credits: NASA/JPL

The Dawn spacecraft is currently performing the Mars flyby phase of its mission. The purpose of the Mars flyby is to alter the trajectory of the spacecraft in order to rendezvous with its first scientific target in the main asteroid belt.

The spacecraft will come within 549 km of the surface of Mars on February 17, 2009, at 4:28 PST.

The flyby is a gravity assist maneuver used in orbital mechanics to alter the trajectory of a spacecraft. The gravity assist is also known as a gravitational slingshot. The first ever gravity assist maneuver was performed by Mariner 10 in February 1974, and most of the interplanetary missions have made use of it since then.

The scientific objective of the Dawn mission is to answer important questions about the origin and the evolution of our solar system. The currently accepted theory about the formation of our solar system states that Jupiter’s gravity interfered with the accretion process, thereby preventing a planet from forming in the region between Jupiter and Mars. This led to the formation of the asteroid belt.

The asteroids chosen as scientific targets for the Dawn mission are Vesta and Ceres. Due to their size, they have survived the collisional phase, and it is believed that they have preserved the physical and chemical conditions of the early solar system. The asteroids have followed different evolutionary paths and have dissimilar characteristics, which makes them perfect research subjects.

Credits: NASA/JPL

The design of the Dawn spacecraft is based on Orbital’s STAR-2 series, and uses flight-proven components from other Orbital and JPL spacecraft: the propulsion system is based on the design used on Deep Space 1, the attitude control system used on Orbview, a hydrazine-based reaction control system used on the Indostar spacecraft, and command and data handling, as well as flight software, from the Orbview program.

The core structure of the spacecraft is a graphite composite cylinder, while the panels are aluminum core with aluminum/composite face sheets.

The central cylinder hosts the hydrazine and xenon tanks. The hydrazine tank can store 45 kg of fuel, while the xenon tank has a capacity of 450 kg.

The attitude control system (ACS) uses star trackers to estimate attitudes in cruise mode. A coarse Sun sensor (CSS) allows ACS to keep the solar panels normal to the Sun-spacecraft line. ACS also uses the hydrazine-based reaction control system for the control of attitude and for desaturation of the reaction wheels.

Credits: NASA/George Shelton

The solar panels are capable of producing more than 10 kW at 1 AU and 1 kW at 3 AU (on Ceres’ orbit).

The command and data handling system (CDHS) is based on a RAD6000 board running VxWorks. The software is written in C. There are 8GB available on the board as storage for engineering and scientific data.

The scientific payload consists of the Framing Camera (FC), the Gamma Ray and Neutron Detector (GRaND), and the visible and infrared (VIR) mapping spectrometer.

The FC will be used for determining the bulk density, the gravity field, for obtaining images of the surface, and for compiling topographic maps of Vesta and Ceres. In addition, the FC will capture images for optical navigation in the proximity of the asteroids. For reliability purposes, the payload includes two identical cameras that can run independently.

GRaND will serve for the determination of the elemental composition of the asteroids. GRaND is the result of the expertise accumulated during the Lunar Prospector and Mars Odyssey programs.

Credits: NASA/Jack Pfaller

VIR will help map the surface mineralogy of the asteroids. The instrument is a modified version of the visible and infrared spectrometer flying on the Rosetta mission.

The Dawn spacecraft uses ion propulsion to make its journey to Vesta and Ceres. Ion propulsion will also be used by Dawn during the low altitude flights over the asteroids.

While the fact that Dawn’s engines have a thrust of only 90 mN can hardly impress a reader, the important detail to mention when discussing propulsion systems is the specific impulse. Dawn’s engines have a specific impulse of 3100 s. For a chemical rocket, the specific impulse ranges from 250 s for solid rockets to 450 s for bipropellant liquid rockets. The only drawback (if this can be regarded as a drawback) is that the ion engines must be fired for much longer in order to achieve an equivalent trajectory.

With such high specific impulse engines, Dawn makes use of the fuel onboard in a very efficient way. The fuel used is xenon, a heavy noble gas placed in group 8A of the periodic table. The power produced by the large solar panels is used to ionize the fuel and then accelerate it with an electric field between two grids. In order to maintain a neutral plasma, electrons are injected into the beam after acceleration.

Credits: NASA/Amanda Diller

Dawn was launched from Cape Canaveral Air Force Station and injected on an interplanetary trajectory by a Delta II launch vehicle.

The main contributors to the Dawn mission are the University of California in Los Angeles (science lead, science operations, data products, archiving, and analysis), the Jet Propulsion Laboratory (project management, systems engineering, mission assurance, payload, navigation, mission operations, level zero data), and the Orbital Sciences Corporation (spacecraft design and fabrication, quality assurance, and payload integration).

The scientific payload was provided by the Los Alamos National Laboratory, the German Aerospace Center, the Max Planck Institute, and the Italian Aerospace Center. The Deep Space Network is responsible for data return from the spacecraft.

For more information about Dawn, you can visit the Dawn Mission Home Page on the JPL web site.

Credits: NASA

The Japanese Experiment Module (JEM) a.k.a. Kibo is the first contribution of the Japan Aerospace Exploration Agency (JAXA) to the International Space Station (ISS) program.

Kibo improves the research capabilities of the ISS by accommodating a maximum of four astronauts who can conduct scientific research activities and experiments in orbit.

JEM has six major components: the Pressurized Module (PM), the Exposed Facility (EF), the Experiment Logistics Module – Pressurized Section (ELM-PS), the Experiment Logistics Module – Exposed Section (ELM-ES), the Remote Manipulator System (JEMRMS), and the Inter-Orbit Communication System (ICS).

The PM is the largest component of JEM. It has a cylindrical shape, 4.4 m in diameter and 11.2 m in length. A total of twenty-three racks can be installed in the PM, six racks on each of the four walls, except for the zenith wall, which can accommodate a maximum of 5 racks. Some of the visible features are the airlock (which allows access to the EF), the two windows located above the airlock, the berthing mechanism for the EF (EFBM), an Active Common Berthing Mechanism (ACBM) on the zenith side for berthing the ELM-PS, and a Passive Common Berthing Mechanism (PCBM) used to connect with the port side ACBM of the Harmony module.

Credits: NASDA

The EF is a box-shaped structure, which is 5.0 m wide, has a length of 5.2 m, and a height of 3.8 m. The EF has 12 payload attachment locations. Each payload location can accommodate a science experiment that must be conducted in the exposed environment.

Kibo’s robotic arm (JEMRMS) is used for attaching and removing the payloads.

The ELM-PS is a cylindrical structure 4.4 m in diameter and 4.2 m in length. The ELM-PS contains a total of eight rack locations. ELM-PS can be used as storage space for experiments, samples, and spare items.

The ELM-ES provides storage space for up to three payloads. ELM-ES will be attached to the end of the EF. Besides the function of in-orbit exposed storage facility, the ELM-ES can also be used to return scientific payloads to Earth. The ELM-ES is a frame structure 4.9 m wide, with a length of 4.1 m, and a height of 2.2 m.

Credits: NASDA

The JEMRMS is a robotic manipulator system. JEMRMS will have two roles: supporting the experiments conducted on Kibo, and assisting with Kibo’s maintenance tasks.

A 10 m long Main Arm (MA), a 2.2 m long Small Fine Arm (SFA), and a robotic control workstation are the components of the robotic manipulator system.

The ICS has two subsystems: a Pressurized Module (ICS-PM) and an Exposed Facility (ICS-EF). The ICS-PM occupies a rack inside the PM, and provides command and data handling functions. The ICS-EF is basically the antenna used for communication.

Kibo is a large structure and more Space Shuttle missions are required to complete the deployment of all the components.

STS-123 Space Shuttle Endeavour delivered the ELM-PS component and ICS-PS to the ISS. JAXA astronaut Takao Doi was part of the STS-123 crew as mission specialist. During the mission, the ELM-PS was berthed to the zenith port of the Node 2 (Harmony) module. The ELM-PS carried the system racks and the experiment racks that are operated in the PM.

Credits: NASA

STS-124 Space Shuttle Discovery delivered the PM and the JEMRMS components to the ISS. The JAXA astronaut assigned to STS-124 as mission specialist was Akihiko Hoshide. STS-124 had to perform a number of operations in order to activate and assemble the pressurized components of JEM: installation and activation of PM, rack deployment, installation of JEMRMS, and the relocation of the ELM-PS from the zenith port of Node 2 to the zenith side of the PM.

The EF is the last major component of Kibo that has to be hauled to the ISS. The STS-127 mission will carry the EF, together with the ELM-ES and the ICS-EF components. The completion of Kibo will be done in two steps: the EF will be attached to the PM through the EFBM, and the ELM-ES will be attached to the EF as the last step. JAXA astronaut Koichi Wakata will be on board the ISS to supervise the operation as mission specialist.

The Japan Aerospace Exploration Agency has a web page dedicated to Kibo.

Credits: ESA/NASA

Columbus is an integral part of the International Space Station (ISS), and it is the first European laboratory dedicated to long-term experimentation in zero-g conditions. The projected lifetime of the laboratory is ten years.

The laboratory is named after the famous Italian navigator and explorer Christoforo Columbus, who discovered the Americas in 1492.

The Columbus Laboratory is a large, pressurized aluminum cylinder measuring 4.5 meters in diameter and 6.9 meters in length. Its side walls contain eight research racks, with another two in the ceiling. Each one of these racks contains its own power and cooling systems. Video and data links systems feed information back to researchers and control centers on the Earth.

Columbus is the smallest ISS laboratory, but it has the same scientific, power, and data handling capacity as the other laboratories owned by Russia, USA, and Japan.

Credits: ESA/NASA

Scientific experiments started immediately on the Columbus because the laboratory arrived at the station with four scientific facilities pre-installed.

Columbus is used to carry out experiments in many different disciplines, including biology, biotechnology, fluid and material science, medicine, and human physiology.

The key element in these experiments is the micro gravity. In micro gravity, with gravitational forces much weaker than on the ground, processes that are obscured by gravity become noticeable. The research racks onboard Columbus are designed to investigate how micro gravity affects materials, biological specimens, and people.

Columbus contains the European Physiology Module Facility, the Fluid Science Laboratory, the BioLab, the Material Science Laboratory, and the European Drawer Rack, which can house a variety of small experiments.

Credits: ESA/NASA

Problems that are investigated on Columbus include the loss of bone cells by astronauts, plant growth in micro gravity, fluids behavior, and combustion of materials.

Experiments are also conducted outside of Columbus. These experiments are used to study the Earth or to expose materials to the harsh radiation, temperature, and the vacuum of space.

The mission that delivered the Columbus Laboratory to the ISS was STS-122. On February 7, 2008, the Space Shuttle Atlantis lifted off from Cape Canaveral, with Columbus docked into its cargo bay.

A vital part of the ISS and a prerequisite for the STS-122 mission, the Italian-built Node2 module (a.k.a. Harmony) was delivered to the ISS by the STS-120 mission in October 2007. The node is used as a connecting component for the Columbus Laboratory and the Kibo Laboratory. Node2 is also a docking port for the Space Shuttle.

Credits: ESA/NASA

Prior to the STS-122 mission , there were two spacewalks performed by the ISS Expedition 16 crew to prepare Node2 in order to receive the Columbus Laboratory.

ESA astronauts Léopold Eyharts from France and Hans Schlegel from Germany were members of the STS-122 mission. With five other NASA astronauts, they were part of the Columbus assembly and commissioning mission.

Schlegel spent twelve days in space and undertook two spacewalks to install the laboratory. Eyharts oversaw the installation and the start-up of the laboratory during a longer mission spent onboard the ISS.

Columbus was attached to the Harmony module on February 11, 2008, during the first spacewalk of the STS-122 mission. During this spacewalk, NASA astronauts Stanley Love and Rex Walheim spent nearly eight hours outside the ISS. The ISS robotic arm, Canadarm2, was used to move the laboratory from the cargo bay of the Space Shuttle to the starboard side of the Harmony module.

Credits: ESA/NASA

The second spacewalk of the mission lasted six hours and forty-five minutes. Schlegel and Walheim performed a regular station maintenance operation: they replaced the nitrogen tank that is used to pressurize the ammonia cooling system that runs on the ISS.

ESA was quite inspired to name the laboratory Columbus because it will open the world of micro gravity to a multitude of discoveries, in the same way that Christoforo Columbus opened up the New World to European explorers.

Credits: NASA

The propulsion division of SpaceX has performed another important test. After the test of the Falcon 9’s first stage Merlin engines, the smallest engine of the SpaceX family, Draco, has been put to test.

During the test, the thruster fired for ten minutes, paused for ten minutes, and then was restarted for an additional minute.

The test was performed on a new vacuum test stand built by SpaceX, and put into operation in March 2008 at the SpaceX Test Facility outside McGregor, Texas.

“Draco performed perfectly during the entire test, with expected temperatures and excellent performance,” said David Giger, Propulsion Manager, SpaceX. “We also broke the SpaceX record for longest continuous burn previously held by Kestrel, the Falcon 1 second stage engine.”

The Dragon spacecraft uses eighteen Draco thrusters for orbital maneuvering, attitude control, and to initiate the atmospheric re-entry. Each Draco thruster can deliver up to 400N of force. The thruster is powered by a combination of mono methyl hydrazine (MMH) and nitrogen tetroxide (NTO), which is the same bipropellant used by the orbital maneuvering system (OMS) of the Space Shuttle.

Credits: NASA

MMH and NTO are used as propellants because they have long on-orbit lifetimes. This will allow the Dragon spacecraft to perform longer missions to the International Space Station (ISS). The goal is to use the spacecraft as an emergency escape capsule for the crew working on the ISS.

SpaceX has released a video of the Draco thruster vacuum firing.