The 1,069 pound Messenger (MErcury Surface, Space ENvironment, GEochemistry, and Ranging) spacecraft is only the second spacecraft sent to Mercury. Mariner 10 flew past Mercury three times in 1974 and 1975. Messenger was launched on 3 August 2004 and flew for 6-1/2 years on a circuitous trajectory that included 15 orbits of the sun, one flyby of Earth, two flybys of Venus, and three flybys of Mercury before entering orbit around Mercury in 18 March 2011. The series of planetary flybys allowed Messenger to decelerate relative to Mercury and achieve orbit with minimal use of fuel.
The NASA Messenger mission website is at the following link:
Messenger is solar-powered, with its science payload and propulsion system located behind a sunshade to protect against the intense solar radiation encountered at Mercury’s close orbit of the Sun.
Source: Johns Hopkins University/APL
Messenger has instrumentation for mapping and characterizing Mercury using imaging cameras, laser altimeter, various spectrometers, magnetometer, and a radio science package to measure slight velocity changes in orbit. You can read details on the spacecraft instrumentation systems at the following link:
After four years in orbit, fuel needed to maintain orbit is expected to be depleted in April. Messenger’s orbit will decay and the spacecraft eventually will crash at perigee into Mercury’s surface at its orbital speed of 8,750 mph.
12 January 2016 update:
On 30 April 2015, Messenger crashed into the surface of Mercury on the side facing away from Earth. Before crashing, Messenger orbited Mercury 4,105 times and collected more than 277,000 images. A composite photograph of Mercury created from thousands of Messenger images is shown below:
This program should be near and dear to all Lynceans because we share a common mascot with XCOR. The Lynx two-seat, piloted space transport vehicle was intended to take humans and payloads on a half-hour suborbital flight to 100 km (330,000 feet) and then return to a landing at the takeoff runway. Lynx was designed as a horizontal takeoff and horizontal landing vehicle, using its own fully-reusable rocket propulsion system to depart a runway and return safely.
Lynx was designed for aircraft-like operations, with plans for up to four flights per day from any suitable, licensed spaceport. The spacecraft was being designed for 40 flights before planned maintenance actions are needed.
Source: XCOR AerospaceSource: XCOR Aerospace
See details about the planned XCOR commercial space program at the following link:
XCOR Update April 2018: XCOR filed for bankruptcy on 8 November 2017 after it was unable to line up partners or new investors to enable it to complete development of the Lynx spaceplane. A nonprofit organization called Build A Plane purchased XCOR’s assets at auction for just under $1.1 million.
Build A Plane founder Lyn Freeman with unfinished Lynx prototype. Source: Douglas Messier/Space.com
You can read more about the bankruptcy filing here:
SpaceShipTwo is Virgin Galactic’s vehicle for commercial, suborbital, human spaceflight. The spacecraft is carried to high-altitude by the White Knight 2 carrier aircraft, and then released to fly under rocket power to more than 100 km altitude and return for a landing at the takeoff runway.
Source: Virgin Galactic
You can read more about this spacecraft at the following link:
After an in-flight accident during testing on 31 October 2014, Virgin Galactic’s first SpaceShipTwo was destroyed and the crew was killed. You can read details on the accident and the post-crash investigation at the following link:
The second SpaceShipTwo is being built and was introduced in January 2015. You can read the latest news on Virgin Galactic’s commercial space program at the following link:
When commercial spaceflight operations begin, they will take place at Spaceport America, which is located about 180 miles south of Albuquerque, NM. Below is a photo of the main building at the spaceport and the White Knight 2 carrier aircraft.
Source: Virgin Galactic
Blue Origin and the New Shepard spacecraft
Blue Origin’s New Shepard system will take astronauts to space on suborbital journeys using rocket-powered Vertical Take-off and Vertical Landing (VTVL) technology. The New Shepard vehicle includes a Crew Capsule carrying three or more astronauts atop a separate rocket-powered Propulsion Module, to be launched from a West Texas Launch Site. After descent and reentry into Earth’s atmosphere, the Crew Capsule will separate from the Propulsion Module and land under parachutes near the launch site. Meanwhile, the Propulsion Module will make a vertical, powered landing at the launch site and then be made ready for reuse on a later flight. An early design of this vehicle is shown below.
Source: Blue Origin
Blue Origin reported on 7 April 2015 that it had completed acceptance flight tests of its cryogenic BE-3 “deep-throttle” rocket engine that will power the reusable New Shepard spacecraft. “Deep throttle” means that the 110,000-lb.-thrust rocker engine can be throttled down to 20,000 lb. thrust, which is needed for a vertical landing. Autonomous flight tests of the spacecraft are scheduled to occur later in 2015. Engine development will continue into 2017.
Visit the Blue Origin website to read more on their commercial space program and BE-3 engine testing at the following link:
Radioisotope Thermoelectric Generators (RTG), also called Radioisotope Power Systems (RTS), commonly use non-weapons grade Plutonium 238 (Pu-238) to generate electric power and heat for National Aeronautics and Space Administration (NASA) spacecraft when solar energy and batteries are not adequate for the intended mission. In comparison to other RTG heat sources (Strontium-90, Cesium-137), Pu-238 has a relatively long half-life of 87.75 years, which is a desirable property for a long-life RTG.
Approximately 300 kg (661 lb) of Pu-238 was produced by the Department of Energy (DOE) at the Savannah River Site between 1959 – 1988. After U.S production stopped, the U.S. purchased Pu-238 from Russia until that source of supply ended in 2010.
Limited production of new Pu-238 in the U.S re-started in 2013 using the process shown below. This effort is partially funded by NASA. Eventually, production capacity will be about 1.5 kg (3.3 lb) Pu-238 per year. The roles of the DOE national laboratories involved in this production process are as follows:
Idaho National Engineering Lab (INEL):
Store the Neptunium dioxide (NpO2) feed stock
Deliver feed stock as needed to ORNL
Irradiate targets provided by ORNL in the Advanced Test Reactor (ATR)
Return irradiated targets to ORNL for processing
Oak Ridge National Lab (ORNL):
Manufacture targets
Ship some targets to INEL for irradiation
Irradiate the remaining targets in the High Flux Isotope Reactor (HFIR)
Process all irradiated targets to recover and purify Pu-238
Convert Pu-238 to oxide and deliver as needed to LANL
Los Alamos National Lab (LANL):
Manufacture the Pu-238 fuel pellets for use in RTGs
Source: Ralph L McNutt, Jr, Johns Hopkins University APL, 2014
In 2015, the U.S. had an existing inventory of about 35 kg (77 lb) of Pu-238 of various ages. About half was young enough to meet the power specifications of planned NASA spacecraft. The remaining stock was more than 20 years old, has decayed significantly since it was produced, and did not meet specifications. The existing inventory will be blended with newly produced Pu-238 to extend the usable inventory. To get the energy density needed for space missions while extending the supply of Pu-238, DOE and NASA plan to blend “old” Pu-238 with newly produced Pu-238 in 2:1 proportions.
Since 2010, NASA’s RTG for spacecraft missions has been the Multi-Mission Radioisotope Thermoelectric Generator (MMRTG), which It is based on the SNAP-19 RTG flown on the two Viking Mars landers (circa 1975) and the Pioneer 10 and 11 deep space probes (circa 1972). At beginning of life, the current MMRTG can provide about 2,000 watts of thermal power and 110 watts of electrical power from eight General Purpose Heat Source (GPHS) modules that contain a total of 10.6 pounds (4.8 kilograms) of plutonium dioxide fuel. Electric conversion efficiency is about 6%.
Assembled MMRTG on a transport dolly. Source: NASA
NASA had a program to develop an Advanced Stirling Radioisotope Generator (ASRG), which was designed to produce about four times the power of the MMRTG per unit of Pu-238. Electric conversion efficiency was about 26%. The ASRG required a total of 2.7 pounds (1.2 kilograms) of plutonium dioxide in two GPHS modules. However, the ASRG would produce less waste heat, which can be used productively to warm electronics in the interior of a spacecraft, such as the Mars rover Curiosity. In November 2013, NASA announced that ASRG development had been discontinued because of budget cuts. You’ll find a NASA ASRG Fact Sheet at the following link: https://rps.nasa.gov/resources/65/advanced-stirling-radioisotope-generator-asrg/
On 22 December 2015, DOE reported the first U.S. production in nearly 30 years of Pu-238. This production demonstration, which was partially funded by the NASA, was performed at ORNL and yielded 50 grams of Pu-238. The last U.S. production of Pu-238 occurred in the late 1980s at the Savannah River Plant in South Carolina.
DOE reported that it plans to set an initial production target of 300 – 400 grams (about 12 ounces) of Pu-238 per year. After implementing greater automation and scaling up the process, ORNL expects to reach the the production target of 1.5 kg (3.3 lb) Pu-238 per year.
The next NASA mission that will use an RTG is the Mars 2020 rover, which will use an MMRTG, as used on NASA’s Mars rover Curiosity.
In the past three years, ORNL has made scant progress in producing Pu-238. In a 13 December 2018 article, “NASA Doesn’t Have Enough Nuclear Fuel For Its Deep Space Missions,”author Ethan Siegel reports: “Although current production (at ORNL) yields only a few hundred grams per year (less than a pound), the laboratory has the eventual goal of ramping up to 1.5 kilograms (3.3 pounds) per year by 2023, at the earliest. Ontario Power Generation in Canada has also begun producing Pu-238, with the goal of using it as a supplemental source for NASA.” You can read the complete article on the Forbes website at the following link: https://www.forbes.com/sites/startswithabang/2018/12/13/nasa-doesnt-have-enough-nuclear-fuel-for-its-deep-space-missions/#1a73d47e1c18
The Canadian plans for becoming a source of Pu-238 was announced on 1 March 2017: “Ontario Power Generation (OPG) and its venture arm, Canadian Nuclear Partners, are participating in a project to produce isotopes in support of deep space exploration. Under the agreement, OPG would help create isotopes at the Darlington nuclear station east of Toronto that will help power space probes.” You can read the complete OPG press release here: https://www.opg.com/news-and-media/news-releases/Documents/20170301_DeepSpace.pdf
The NASA Mars rover, Perseverance, was launched from Cape Canaveral on 30 July 2020, with an expected landing date of 18 February 2021 in the Jezero crater on Mars. Once on the surface, Perseverance will be powered by an MMRTG.
The Pu-238 and some other special materials for the Perseverence MMRTG were produced in the U.S. at ORNL, as described in the following short (2:03 minutes) video, “ORNL-produced tech fuels NASA’s Perseverance mission to Mars”:
In a 20 July 2020 news release, ORNL provided more information on the U.S. production process for Pu-238 and reported that, “the lab has been consistently increasing its Pu-238 production capabilities, aiming to produce 1.5 kilograms per year by 2026.” You can read this ORNL press release here: https://www.ornl.gov/news/ornl-produced-plutonium-238-help-power-perseverance-mars
At the planned U.S. production rate for Pu-238, NASA should be able to conduct an MMRTG mission at about four-year intervals. If NASA MMRTG missions will be more frequent than this, the U.S. will need to purchase additional Pu-238 from another source, perhaps Canada.
5 March 2021 Update:
The Perseverance rover landed on Mars on 18 February2021, in the planned target area in Jezero Crater. Power from the MMRTG was nominal after landing. Perseverance will spend at least one Mars year (two Earth years) exploring the landing site region.
The next NASA mission with an MMRTG-powered spacecraft is the Dragonfly mission to Saturn’s moon Titan, which will launch in 2026 and arrive on Titan in 2034.
The Voyager 1 and 2 spacecraft were launched in 1977, each with three RTGs delivering a maximum of 470 watts of electrical power at the beginning of the mission. Both spacecraft have left the solar system (Voyager 1 in 2013 and Voyager 2 in 2018) and continue to transmit from interstellar space in 2021 with their RTGs operating at a reduced power level of about 331 watts after 44 years of Pu-238 decay during the mission. NASA plans to continue the Voyager missions until at least 2025.
The Spitzer Space Telescope, an infrared space observatory, was launched on 8 August 2003 into an “earth-trailing” orbit around the Sun. It is one of four “Great Observatories” launched by NASA; the others being the Hubble Space Telescope, the Compton Gamma-ray Observatory; and the Chandra X-ray Observatory.
Diagram source: NASA
The primary mirror is 85 cm in diameter, made of beryllium, and until May 2009, was cooled by liquid helium to 5.5 degrees K. With the on-board liquid helium supply exhausted, most of the instruments were no longer usable. However, the two shortest wavelength modules of the Infrared Science Archive (IRAC) camera remained operable at their original sensitivities. This allowed the mission team to continue with the “Spitzer Warm Mission”.
You can read about the design of the Spitzer Space Telescope at the following link:
“After more than 16 years studying the universe in infrared light, revealing new wonders in our solar system, our galaxy and beyond, NASA’s Spitzer Space Telescope’s mission has come to an end…..the spacecraft was placed in a safe mode, ceasing all scientific operations.”
You can read the NASA announcement and a summary of the accomplishments of the Spitzer mission here:
The Opportunity rover landed on Mars on January 25, 2004. It originally was designed for a 90 Sol mission (a Sol, one Martian day, is slightly longer than an Earth day at 24 hours and 37 minutes). The rover has proven to be far more durable than expected. A marathon is a long-distance running event with an official distance of 42.195 kilometers (26 miles and 385 yards). The rover Opportunity is the first extraterrestrial rover to complete this distance. The record time for this event was 11 years and 2 months.
Rover Opportunity; source: NASA
Map of the marathon trek; source: NASA
8 July 2015 Update:
On 2 July 2015, NASA/JPL uploaded an 8-minute time-lapse video of rover Opportunity’s marathon road trip on Mars. This compilation of images from the low-resolution, wide-field-of-view hazard-avoidance cameras on rover Opportunity between January 2004 and April 2015 shows the rover’s-eye-view of the Martian marathon from its landing location to the rim of Endeavour Crater. The sound in the video is synthesized from accelerometers on rover Opportunity. You can view this video using the link below. The view from the rover is in the left-hand panel, and a map of the rover’s path is on the right-hand panel of the video.
NASA’s Kepler extrasolar planet (exoplanet) hunting observatory was launched on 7 March 2009 into an Earth-trailing orbit around the Sun. From this vantage point, Kepler has a continuous, unobstructed view of the selected target areas in the “northern” sky, above the ecliptic plane (plane of the solar system). Kepler has a very narrow field of view, which is about twice the size of the scoop of the Big Dipper as we see it from Earth (about 1/400th of the sky).
NASA’s Kepler mission website is at the following link:
The Kepler mission team primarily uses the “transit” method to detect exoplanets. NASA explains the transit method as follows:
“When a planet passes in front of a star as viewed from Earth, the event is called a ‘transit’. On Earth, we can observe an occasional Venus or Mercury transit. These events are seen as a small black dot creeping across the Sun — Venus or Mercury blocks sunlight as the planet moves between the Sun and us. Kepler finds planets by looking for tiny dips in the brightness of a star when a planet crosses in front of it — we say the planet transits the star.
Once detected, the planet’s orbital size can be calculated from the period (how long it takes the planet to orbit once around the star) and the mass of the star using Kepler’s Third Law of planetary motion. The size of the planet is found from the depth of the transit (how much the brightness of the star drops) and the size of the star. From the orbital size and the temperature of the star, the planet’s characteristic temperature can be calculated. From this the question of whether or not the planet is habitable (not necessarily inhabited) can be answered”.
The following figure illustrates the effect on brightness of a planet transiting across a star.
Source: NASA Ames
Kepler originally used four reaction wheels to orient the spacecraft to observe specific regions of the sky. After failure of a second reaction wheel in 2013, Kepler no longer was able to maintain a desired orientation with sufficient accuracy. The mission was stopped and the spacecraft was put in “safe mode” until a modified mission plan, dubbed “K2” or “Second Light” was tested and then implemented in May 2014. This K2 mission plan defined new target areas that could be observed using the two remaining reaction wheels and thrusters to orient and stabilize the spacecraft. Measured pointing accuracy in the K2 configuration has been shown to be almost equal to the pointing accuracy with three reaction wheels. The K2 mission is expected to continue through the end of 2016.
The Kepler mission team announced discovery of the first Earth-sized planet in the habitable zone of a star in April 2014. This planet, named Kepler-186f, orbits a red dwarf, the most common type of star in the Milky Way, about 500 light years from Earth.
You will find current information on the confirmed and candidate exoplanets discovered by Kepler at the following link to the NASA Kepler website:
In March 2015, NASA’s Kepler team won the National Air and Space Museum 2015 Trophy for Current Achievement. Read more about this award at the following link:
The 10 May 2016 issue of The Astrophysical Journal includes an article entitled, “False Positive Probabilities for all Kepler Objects of Interest: 1284 Newly Validated Planets and 428 Likely False Positives,” by T.D. Morton et al. This paper reports the results of the first large-scale demonstration of a fully automated transiting planet validation process that calculates the probability of an observation being a false positive. A remarkable aspect of this work is that the automated validation process was applied to every Kepler Object of Interest (KOI). The key results reported in this paper are as follows:
Out of 7,056 KOIs, the team determine that 1,935 have probabilities <1% of being astrophysical false positives, and thus may be considered validated planets.
Of these, 1,284 have not yet been validated or confirmed by other methods.
428 KOIs are likely to be false positives, but have not yet been identified as such by other means
You can download the complete paper at the following link:
NASA announced that the Kepler Space Telescope ran out of fuel today and no longer could orient itself to study cosmic objects or transmit data to Earth.
“As NASA’s first planet-hunting mission, Kepler has wildly exceeded all our expectations and paved the way for our exploration and search for life in the solar system and beyond,” said Thomas Zurbuchen, associate administrator of NASA’s Science Mission Directorate in Washington. “Not only did it show us how many planets could be out there, it sparked an entirely new and robust field of research that has taken the science community by storm. Its discoveries have shed a new light on our place in the universe, and illuminated the tantalizing mysteries and possibilities among the stars.”
The Dawn spacecraft is the only spaceship built to orbit two extraterrestrial bodies; the large asteroid Vesta and the dwarf planet Ceres, both of which are in the main asteroid belt between Mars and Jupiter. You can see that Vesta and Ceres are quite small in comparison to Earth’s moon.
Source: NASA
Dawn spacecraft showing ion propulsion engine firing:
Source: NASA
Dawn’s mission was enabled by an advanced solar-electric xenon ion propulsion system. You can read more about the propulsion system and Dawn’s instrumentation at the following NASA link:
Using its ion propulsion system, Dawn departed Vesta in September 2012 and headed for it’s rendezvous with Ceres, arriving in orbit on 6 March 2015. You can read about the orbital insertion and see a 360 degree view of Ceres at the following link:
View of Ceres from Dawn, showing two bright spots of unknown origin.
Ceres. Source: NASA
Dawn’s initial orbit was at an altitude of 8,400 miles above Ceres. Over the next month, Dawn is using it’s ion propulsion system to spiral down to a “survey orbit” 2,700 miles above Ceres. After the survey is complete, the ion propulsion system will be used again to spiral down gradually to a 910 mile “high-altitude mapping orbit”. Late in 2015, the spacecraft will descend again until it reaches a “low altitude mapping orbit” at an altitude of 230 miles. Because of the very low thrust of the ion propulsion engines, the transitions between orbits takes a long time (several weeks). You can read the details about the in-orbit management of the spacecraft at the following link:
The New Horizons spacecraft is scheduled for a flyby of Pluto and its five known moons on July 14, 2015. Launched in January 2006, New Horizons has gone through 18 “hibernation” cycles enroute to Pluto. It came out of its last hibernation cycle on December 6, 2014. New Horizons electrical systems are powered by a radioisotope thermoelectric generator (RTG) that produces electricity from the heat of decaying Plutonium 238. Propulsion is by means of hydrazine thrusters.
New Horizons spacecraft. Source: NASA
You can find details on the design of the New Horizons spacecraft at the following link:
As noted in that article, Charon’s mass is roughly a tenth of Pluto’s, which gives it enough gravitational pull to have a noticeable effect on Pluto’s position.
You can follow details on the New Horizons mission on the following NASA website:
After the Pluto encounter, New Horizons will continue on to visit one or more objects in the Kuiper Belt, which circles our solar system beyond the orbit of Pluto. The Hubble space telescope has been used to search for potential Kuiper Belt Objects (KBOs).
Mark your calendar! March 18, 2015 marks the 50th anniversary of the very first extra-vehicular activity (EVA) in history, which was performed by Russian cosmonaut Alexei Leonov, who briefly left Voskhod 2 while in orbit in 1965.
This was a 12 minute spacewalk. Spacesuit over-inflation made it difficult for Leonov to re-enter the Voskhod 2 capsule and faulty hatch closure contributed to an off-course reentry.
You can read a brief article about this and other EVAs that did not go as planned at the following link:
The U.S. military-operated Global Positioning System (GPS) achieved full operational capability in 1995 and was declared a “dual-use” (military and civilian) system in 1996. Today, GPS functionality is embedded in many of the electronic products and vehicles we use on a daily basis. You’ll find plenty of information on GPS at the following link:
Globalnaya Navigatsionnaya Sputnikovaya Sistema (Global Navigation Satellite System), GLONASS is a Russian military-operated satellite-based navigation system. The intent for GLONASS to be a dual-use system was declared in 2007 and full global coverage was achieved in 2011. By the end of 2011, GLONASS claims it met a goal of matching GPS accuracy and reliability, and GLONASS may be more accurate than GPS at high latitudes because of the higher inclination of GLONASS satellite orbits. iPhones and several types of Android phones have both GLONASS and GPS chips and may use both satellite signals to improve navigation results. Check out the story at the following link:
While European independence from GPS & GLONASS was a key goal behind the creation of the new system, Galileo is intended to be 100% interoperable with GPS and GLONASS. The first two operational Galileo satellites were launched in October 2011, with two more following in October 2012. These four Galileo satellites represent the operational nucleus of the future 30-satellite constellation. The 5th & 6th Galileo satellites were launched in August 2014 into incorrect orbits and are not operational.
You can get more information on Galileo at the following European Space Agency web site:
Relativistic corrections needed for satellite navigation system accuracy:
These three satellite navigation systems depend on relativistic corrections to ensure that accurate data are delivered to the end users. You can find a short article entitled, “Real-World Relativity: The GPS Navigation System,” at the following link:
Source: Johns Hopkins University/APL
Source: NASA / Johns Hopkins University/APL
Source: XCOR Aerospace
Build A Plane founder Lyn Freeman with unfinished Lynx prototype. Source: Douglas Messier/Space.com
New Horizons spacecraft. Source: NASA
Source: NASA
Source: NASA
