OrbitalHub

Credits: ESA

ESA plans to design and build an autonomous lifting and aerodynamically controlled re-entry system. Critical technologies are being tested: instrumentation for aerodynamics and aerothermodynamics, thermal protection and hot-structure solutions, guidance, navigation, and flight control using a combination of jets and aerodynamic flaps. The Intermediate Experimental Vehicle (IXV) will be the European platform for in-flight testing of re-entry technologies.

The design activities are already underway; the development of the spacecraft is scheduled to begin in January 2009.

The mission is planned to launch from the European spaceport at Kourou, French Guiana. In 2012, a new launch vehicle will inject IXV into a low Earth orbit. The small spacecraft will perform a controlled re-entry, its descent slowed by a parachute, and will land in the Pacific Ocean.

Credits: ESA

ESA released a new video with computer generated animation that presents the planned IXV mission.

We presented in a previous post the Lunar Reconnaissance Orbiter (LRO) mission. The goals of the LRO mission are to map the lunar resources and to create a detailed 3D map of the lunar surface in preparation for future NASA missions to the Moon. However, NASA is not the only space agency that has high hopes regarding the exploration of the Moon. The Indian Space Research Organization (ISRO) is another agency heavily involved in space activities.

Credits: ISRO

Interest in undertaking a lunar scientific mission was sparked at a meeting of the Indian Academy of Sciences in 1999. One year later, the Astronautical Society of India made a recommendation supporting the idea.

The ISRO formed a National Lunar Mission Task Force that involved leading Indian scientists. The Task Force provided an assessment on the feasibility of such a mission. The mission, called Chandrayaan-1, was approved in November 2003 for an estimated cost of $83 million USD.

The Chandrayaan-1 spacecraft is a 1.5 meter cube with a weight mass of approximately 523 kg. The spacecraft bus is based on an already developed meteorological satellite. Chandrayaan-1 will carry a 30 kg probe that will be released to penetrate the lunar surface. The power for the onboard systems is generated by a solar panel. The 750 watts generated by the solar panel will be stored by the rechargeable batteries onboard the spacecraft. Maneuvering in the lunar orbit is done using a bipropellant propulsion system.

Credits: ISRO

The scientific payload contains a diverse collection of instruments. The instruments were designed and developed by ISRO, ESA, NASA, and the Bulgarian Space Agency.

There are two instruments that will map the surface of the Moon: the Terrain Mapping Camera (TMC) will produce a 5 meter resolution map of the surface, and the Lunar Laser Ranging Instrument (LLRI) will scan the lunar surface and determine the surface topography.

The X-ray spectrometer onboard the spacecraft has three components: the Imaging X-ray Spectrometer (CIXS), the High Energy X-ray/gamma ray spectrometer (HEX), and the Solar X-ray Monitor (SXM). The X-ray spectrometer will measure the concentration of certain elements on the lunar surface as well as monitor the solar flux in order to normalize the results of the measurements taken.

The mineralogical configuration of the surface will be mapped by four instruments: the Hyper Spectral Imager (HySI), the Sub-keV Atom Reflecting Analyzer (SARA), the Moon Mineralogy Mapper (M3), and the Near-Infrared Spectrometer (SIR-2).

The Radiation Dose Monitor (RADOM-7) will record the radiation levels in the lunar orbit.

Credits: ISRO

ISRO has two operational launch vehicles: the Polar Satellite Launch Vehicle (PSLV) and the Geosynchronous Satellite Launch Vehicle (GSLV). For Chandrayaan-1, ISRO has chosen to use PSLV as a launch vehicle. The PSLV developmental flights were completed in 1996 and the rocket has had 12 successful missions since then. PSLV is 44.43 meters tall and has a weight of 294 tonnes at launch. It can inject a payload of 1,000 kg – 1,200 kg into a polar orbit.

The launch of the Chandrayaan-1 mission is scheduled for the end of October 2008. The PSLV rocket will take off from the Satish Dhawan Space Center in Sriharikota on the southeast coast of India. The transfer to the lunar orbit will take approximately five days and after additional maneuvers the spacecraft will reach its final polar orbit, 100 km above the surface. The spacecraft will be operational for two years.

The Chandrayaan-1 mission opens the door to future lunar missions. ISRO has already committed to a second Chandrayaan mission that will land a rover on the surface of the Moon. The rover will perform a number of experiments on the lunar surface and the results will be relayed to Earth by the Chandrayaan-2 orbiter.

We will come back with more details about the Chandrayaan-1 mission as the events unfold. Please stay tuned on the OrbitalHub frequency.

In the previous three posts we presented the most common solutions employed by spacecraft designers in order to generate the power needed by onboard systems during a space mission: the batteries, the solar panels, and the radioisotope thermoelectric generators. We will conclude by presenting two more existing solutions: the fuel cells and the nuclear reactors.

Credits: NASA

Fuel cells are devices that convert chemical energy into electricity. Even if using the same type of energy conversion, fuel cells are more efficient than the batteries. Electricity is produced directly from an oxidation reaction. The fuel and an oxidant react in the presence of a catalytic material inside the cell. By eliminating the reaction products and maintaining the input flows, fuel cells can operate continuously. For space applications, only hydrogen and oxygen have been used as reactants. Other sources rich in hydrogen that can be used as fuel are methane, methanol, and ethanol.

Regenerative fuel cells are a viable option for energy storage in large space systems. They could successfully replace the secondary batteries. The regenerative fuel cells would use stored hydrogen and oxygen to generate electricity during eclipse periods and would use solar arrays to generate electricity to recharge the fuel cells during the illuminated portion of the orbit. The generated electricity would be used to produce oxygen and hydrogen by electrolyzing the water produced by the fuel cells during normal operation. As far as we know, there are no direct applications of regenerative fuel cells in the space industry to date.

The nuclear reactors used by spacecrafts for power generation are smaller versions of the nuclear reactors used onboard nuclear submarines or nuclear aircraft carriers. They are the only compact solution for large power levels, hundreds of kilowatts to megawatts. In principle, the controlled nuclear reaction generates the heat, while an agent carries the heat away and is used to generate steam. The steam is used to drive a turbine that generates electricity. I was not able to find any technical details on the cooling agent and the liquid (or gas) used to drive the turbine (or even if a turbine is used) for the SP-100. SP-100 is the only nuclear reactor destined to power space systems built by the US. I was able to dig up the information that the Russian-built nuclear reactors that operated on the RORSAT reconnaissance satellites used NaK-78 as cooling agent (NaK-78 is a sodium and potassium fusible alloy with a low melting point).

SP-100 initially was supposed to have a mass of approximately 3,000 kg and generate 100 kWe. The SP-100 program was eventually canceled due to the fact that as the design matured the weight exceeded the acceptable limit.

Credits: NASA/JPL

The RORSAT Russian satellites have an interesting story… they had active radars onboard and had to be placed in low Earth orbits in order to have the surveillance equipment work effectively. Orbiting in LEOs, RORSAT missions had a shorter lifespan and had to perform a destructive re-entry in the atmosphere. In order to avoid the re-entry of any radioactive material, the nuclear reactor’s core was ejected in a so-called disposal orbit (a high orbit that would postpone the re-entry of the core for a couple of hundreds of years).

Failures were recorded. Most notably, in 1978, a RORSAT mission failed to boost the radioactive core into the disposal orbit and radioactive material entered the atmosphere above the Northwest Territories in Canada. The affected area had over 124,000 square kilometers.

A major disadvantage of the deployment of nuclear reactors is that for manned missions, heavy shielding is required. The shield mass can be reduced by employing designs that use geometric separation, but this is attainable only for large configurations. Other disadvantages are the reduction in reliability due to the moving parts and the possible mechanical interferences due to the vibrations that any dynamic system generates. Despite all these drawbacks, nuclear reactors offer a considerable promise for the future.

Power systems are essential for a space mission and, due to the challenges raised by the space environment, finding the right solution for a space mission requires careful consideration of many factors. Each solution comes with its own advantages and disadvantages making the work of space systems design engineers hard and rewarding in the same time.

We hope you enjoyed reading this series of posts and that you found them interesting. We are looking forward to your feedback and welcome your comments.

We covered the ATV Jules Verne mission in a previous post (Jules Verne close to the End of its Space Journey) and mentioned that the typical ATV mission ends with a destructive re-entry above the Pacific Ocean. We come back with this post to present the conclusion of the ATV mission.

Credits: NASA

The ATV separated from the International Space Station (ISS) on September 5, 2008, filled with more than 2 tonnes of waste. The ATV undocked from the aft port of the Zvezda Service Module and it was placed in a parking orbit for three weeks. While being parked, a series of tests of the guidance and control systems were performed.

By carrying out re-phasing maneuvers, the ATV positioned itself to a predefined position behind and underneath the ISS. In this way, the crews from the ISS and from two specially equipped observation planes in the skies of the South Pacific were able to view and to record the re-entry.

Credits: NASA

The re-entry was initially modeled on computer in order to anticipate the trajectory and the location of the area where the breakout fragments of the spacecraft will fall. The observations helped determine if the re-entry matched the computer modeling.

As planned, the first ATV mission concluded on September 29, 2008, when two engine burns de-orbited the spacecraft. ESA scheduled the re-entry on this date because the lighting conditions were appropriate for an imagery experiment and the breakup happened at approximately 75 km above the waters of the Pacific Ocean. The remaining fragments fell into the Pacific some 12 minutes later.

Credits: ESA

This first mission proved the logistical value of the ATV. The delivery of 6 tonnes of cargo to the ISS, the automatic rendezvous and docking capabilities, the attitude control maneuvers performed, they all show how far the European space capabilities have developed.

ESA engineers are already working on the next two ATV spacecrafts. The next ATV mission is scheduled for 2010 and there are many proposals to adapt the ATV to other types of missions.

Credits: ESA

One important variation of the typical ATV mission is the Large Cargo Return (LCR). The LCR configuration will consist of a large cargo capsule capable of bringing back on Earth hundreds of kilograms of cargo and valuable experiment results. LCR would be able to dock to the US side of the ISS that has larger docking ports and would make possible the transfer of complete payload racks.

The video showing the destructive re-entry of Jules Verne is available on the ESA website.

Some of the most important questions asked in modern science are: how did the Universe begin, how did it evolve to its present state, and how will it continue to evolve in the future? To ask these questions, the remnant radiation that filled the Universe immediately after the Big Bang must be analyzed. This remnant radiation is known as the Cosmic Microwave Background (CMB).

Credits: ESA

ESA plans to answer these questions with Planck: the first European mission to study the birth of the Universe. The Planck Mission will collect CMB radiation measurements using highly sensitive sensors that are operating at very low temperatures. The measurements will be used to map the smallest variations of the CMB detected to date.

The Planck spacecraft will weigh around 1,900 kg at launch. It is 4.2 m high and has a maximum diameter of 4.2 m. There are two modules that comprise the spacecraft: a service module and the payload module.

The service module contains the systems for power generation, attitude control, data handling and communication, and the warm components of the scientific payload. The payload module contains the telescope, the optical bench, the detectors, and the cooling system (which is of critical importance, as we shall see).

The telescope is an important onboard component. The Planck telescope is a Gregorian telescope with an off-axis parabolic primary mirror 1.75 x 1.5 meters in size. A secondary mirror focuses the incoming microwave radiation on two sets of highly sensitive detectors: the Low Frequency Instrument (LFI) and the High Frequency Instrument (HFI). The Gregorian design offers two key advantages: it is compact and it does not block the optical path.

Credits: ESA/Thales

The LFI will be operating at –253 degrees Celsius. The array of twenty-two tuned radio receivers that comprise LFI will produce high-sensitivity, multi-frequency measurements of the microwave sky in the frequency range of 27 GHz to 77 GHz.

The HFI has to be cooled to –272.9 degrees Celsius in order to operate (one tenth of one degree above the absolute zero!). HFI’s fifty-two bolometric detectors will produce high-sensitivity, multi-frequency measurements of the diffuse sky radiation in the frequency range of 84 GHz to 1 THz.

A baffle surrounds the telescope and instruments. The baffle prevents light from the Sun and the Moon from altering the measurements. A complex system of refrigerators is used onboard the spacecraft in order to achieve the temperatures needed for nominal operation. The detectors have to work at temperatures close to the absolute zero, otherwise their own emissions can alter the measurements.

The two instruments will be used to measure the small variations of the CMB across the sky. By combining the measurements, a full sky map of unprecedented precision will be produced. The map will help astronomers decide which theories on the birth and the evolution of the Universe are correct. Questions like ‘what is the age of the Universe?’ or ‘what is the nature of the dark-matter?’ will be answered.

The mission was initially designed as COBRAS/SAMBA (Cosmic Background Radiation Anisotropy Satellite and Satellite for Measurement of Background Anisotropies) because it grew out of two mission proposals that had similar objectives. When the mission was approved in 1996, it was also renamed as Planck in honor of the German scientist Max Planck (1858 – 1947). Max Planck was awarded the Nobel Prize for Physics in 1918.

Credits: ESA

The mission is a collaborative effort. The Planck spacecraft was designed and built by a consortium led by Alcatel Alenia Space (Cannes, France). The telescope mirrors are manufactured by EADS Astrium (Friedrichshafen, Germany). The Low Frequency Instrument (LFI) was designed and built by a consortium led by the Instituto di Astrofisica Spaziale e Fisica Cosmica (IASF) in Bologna, Italy. The High Frequency Instrument (HFI) was designed and built by a consortium led by the Institut d’Astrophysique Spatiale (CNRS) in Orsay, France.

The Planck Mission has two predecessors: the Cosmic Background Explorer (COBE) and the Wilkinson Microwave Anisotropy Probe (WMAP).

Credits: ESA

The Planck spacecraft will be launched in early 2009 from Kourou, French Guiana. An Ariane 5 booster will place the spacecraft in a trajectory towards the L2 point. The L2 point stands for Second Lagrangian Point and it is located around 1.5 million kilometers away from Earth in a direction diametrically opposite the Sun. It will be a dual launch configuration, as the Herschel spacecraft will be launched together with Planck.

Between four to six months after the launch, Planck will reach its final position. It will take six more months before Planck will be declared operational.

Planck will perform scientific measurements for fifteen months, allowing two complete sky surveys. The spacecraft will be operational as along as there are resources for the cooling systems onboard.

For more details on the ESA’s Planck Mission you can visit the mission’s home page on the ESA website.

After six years of tremendous effort and more than $100 million USD spent, SpaceX made a successful launch of Falcon 1. Falcon 1 is the first booster built by a private company to ever reach the Earth’s orbit. This is the fourth Falcon 1 mission.

Credits: SpaceX

The booster lifted off yesterday from the testing site on Omelek Island in the Kwajalein Atoll located in the central Pacific some 2,500 miles southwest of Hawaii.

The previous three missions were not successful, but SpaceX managed to remove all the stumbling blocks out of the way. In less than two months from the previous attempt, on August 2nd 2008, SpaceX had another booster ready for launch.

The payload carried by the Flight 4 mission is a mass simulator that weighs around 165 kg. The payload did not separate but remained attached to the second stage as it orbits the Earth.

Falcon 1 is a two-stage booster. It uses liquid oxygen and rocket grade kerosene as fuel. The booster is 21.3 meters long and 1.7 meters in diameter. It weighs 27, 670 kg when ready to launch. The first stage of the booster is powered by a Merlin 1C engine and the upper stage is powered by a Kestrel engine.

The Merlin 1C engine is a turbo pump fed engine, while the smaller Kestrel engine uses tank pressure to inject the fuel into its combustion chamber. In order to simplify the design, the Merlin engine uses the high-pressure kerosene to cool the combustion chamber and the nozzle. In addition, the engine uses the high-pressure kerosene for the hydraulic actuators, thereby eliminating the need for a separate hydraulic power system.

Credits: SpaceX

Falcon 1 is the first in a family of launch vehicles that SpaceX will build and operate. NASA awarded Commercial Orbital Transportation Services (COTS) funding to SpaceX to demonstrate delivery and return of cargo and potentially a human crew to the International Space Station (ISS). In order to achieve these goals, SpaceX is developing a bigger booster, Falcon 9, and a cargo and crew capsule, Dragon.

SpaceX holds a unique position in the launch vehicle market, being able to take over the delivery of supplies and human crews to the ISS, after the Space Shuttle’s retirement in 2010. For more information about SpaceX and its fleet of launch vehicles, check out their website.