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A black hole is a region of spacetime where gravity is so strong that nothing—no particles or even electromagnetic radiation such as light—can escape from it. The theory of general relativity predicts that a sufficiently compact mass can deform spacetime to form a black hole. The boundary of the region from which no escape is possible is called the event horizon. Although the event horizon has an enormous effect on the fate and circumstances of an object crossing it, according to general relativity it has no locally detectable features. In many ways, a black hole acts like an ideal black body, as it reflects no light. Moreover, quantum field theory in curved spacetime predicts that event horizons emit Hawking radiation, with the same spectrum as a black body of a temperature inversely proportional to its mass. This temperature is on the order of billionths of a kelvin for black holes of stellar mass, making it essentially impossible to observe.

Objects whose gravitational fields are too strong for light to escape were first considered in the 18th century by John Michell and Pierre-Simon Laplace. The first modern solution of general relativity that would characterize a black hole was found by Karl Schwarzschild in 1916, although its interpretation as a region of space from which nothing can escape was first published by David Finkelstein in 1958. Black holes were long considered a mathematical curiosity; it was not until the 1960s that theoretical work showed they were a generic prediction of general relativity. The discovery of neutron stars by Jocelyn Bell Burnell in 1967 sparked interest in gravitationally collapsed compact objects as a possible astrophysical reality.

Black holes of stellar mass are expected to form when very massive stars collapse at the end of their life cycle. After a black hole has formed, it can continue to grow by absorbing mass from its surroundings. By absorbing other stars and merging with other black holes, supermassive black holes of millions of solar masses (M☉) may form. There is consensus that supermassive black holes exist in the centers of most galaxies.

Video credit: NASA Jet Propulsion Laboratory

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The International Space Station (ISS) is a modular space station (habitable artificial satellite) in low Earth orbit. It is a multinational collaborative project between five participating space agencies: NASA (United States), Roscosmos (Russia), JAXA (Japan), ESA (Europe), and CSA (Canada). The ownership and use of the space station is established by intergovernmental treaties and agreements. The ISS program evolved from the Space Station Freedom, an American proposal in the 1980s to construct a permanently crewed Earth-orbiting station.

The ISS serves as a microgravity and space environment research laboratory in which scientific experiments are conducted in astrobiology, astronomy, meteorology, physics, and other fields. The station is suited for testing the spacecraft systems and equipment required for possible future long-duration missions to the Moon and Mars. It is the largest artificial object in space and the largest satellite in low Earth orbit, regularly visible to the naked eye from Earth’s surface. It maintains an orbit with an average altitude of 400 kilometres (250 mi) by means of reboost manoeuvres using the engines of the Zvezda Service Module or visiting spacecraft. The ISS circles the Earth in roughly 93 minutes, completing 15.5 orbits per day.

The station is divided into two sections: the Russian Orbital Segment (ROS), operated by Russia; and the United States Orbital Segment (USOS), which is shared by many nations. Roscosmos has endorsed the continued operation of ISS through 2024, but had previously proposed using elements of the Russian segment to construct a new Russian space station called OPSEK. As of December 2018, the station is expected to operate until 2030.

Video credit: NASA

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After the Space Shuttle program was brought to an end in 2011, NASA no longer had a spacecraft system capable of sending humans to space. As a result, it was forced to fly its astronauts to the International Space Station (ISS) aboard the Russian Soyuz space vehicle, at a cost of up to US$80 million per astronaut. As an alternative, NASA contracted with private companies such as SpaceX for the Commercial Crew Program, which is expected to cost 50% less than Soyuz once in regular operation. Up to the launch, NASA has awarded a total of US$3.1 billion for the development of the Dragon 2. The Demo-2 mission is expected to be SpaceX’s last major test before NASA certifies it for regular crewed spaceflights. Prior to that, SpaceX had sent twenty cargo missions to the ISS, but never a crewed one.

Video credit: NASA’s Kennedy Space Center

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Perseverance, nicknamed Percy, is a Mars rover manufactured by the Jet Propulsion Laboratory for use in NASA’s Mars 2020 mission.

The Perseverance rover was designed with help from the Curiosity’s engineering team, and they are similar to each other. Engineers redesigned the Perseverance rover wheels to be more robust than Curiosity’s wheels, which have sustained some damage. The rover has thicker, more durable aluminum wheels, with reduced width and a greater diameter (52.5 centimetres (20.7 in)) than Curiosity’s 50-centimetre (20 in) wheels. The aluminum wheels are covered with cleats for traction and curved titanium spokes for springy support. The combination of the larger instrument suite, new Sampling and Caching System, and modified wheels makes Perseverance heavier than its predecessor, Curiosity, by 17% (899 kg to 1050 kg). The rover will include a five-jointed robotic arm measuring 2.1 metres (6 ft 11 in) long. The arm will be used in combination with a turret to analyze geologic samples from the Martian surface.

The rover’s power generator (MMRTG) has a mass of 45 kilograms (99 lb) and uses 4.8 kilograms (10.6 lb) of plutonium dioxide as the source of steady supply of heat that is converted to electricity. The electrical power generated is approximately 110 watts at launch with little decrease over the mission time. Two lithium-ion rechargeable batteries are included to meet peak demands of rover activities when the demand temporarily exceeds the MMRTG’s steady electrical output levels. The MMRTG offers a 14-year operational lifetime, and it was provided to NASA by the US Department of Energy. Unlike solar panels, the MMRTG provides engineers with significant flexibility in operating the rover’s instruments even at night and during dust storms, and through the winter season.

The rover’s computer uses the BAE RAD750 radiation-hardened single board computer. The computer contains 128 Megabytes of volatile DRAM, and is run at 133 MHz. The flight software is able to access 4 gigabytes of NAND non-volatile memory on a separate card.

Also travelling with Perseverance as a part of Mars 2020 is the Mars helicopter experiment, named Ingenuity. A solar-powered helicopter drone with a mass of 1.8 kilograms (4.0 lb), it will be tested for flight stability and for its potential to scout the best driving route for the rover over a planned 30-day period. Other than cameras, it carries no scientific instruments.

Video credit: Aerojet Rocketdyne

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The SpaceX Starship is a fully reusable super heavy-lift launch vehicle under development by SpaceX since 2012, as a self-funded private spaceflight project.

The second stage of the Starship — is designed as a long-duration cargo and passenger-carrying spacecraft. It is expected to be initially used without any booster stage at all, as part of an extensive development program to prove out launch-and-landing and iterate on a variety of design details, particularly with respect to the vehicle’s atmospheric reentry.

While the spacecraft will be tested on its own at suborbital altitudes, it will be used on orbital launches with an additional booster stage, the Super Heavy, where the spacecraft will serve as the second stage on a two-stage-to-orbit launch vehicle.

Integrated system testing of a proof of concept for Starship began in March 2019, with the addition of a single Raptor rocket engine to a reduced-height prototype, nicknamed Starhopper — similar to Grasshopper, an equivalent prototype of the Falcon 9 reusable booster. Starhopper was used from April through August 2019 for static testing and low-altitude, low-velocity flight testing of vertical launches and landings in July and August 2019. More prototype Starships are under construction and are expected to go through several iterations. All test articles have a 9 metres (30 ft) of diameter stainless steel hull.

SpaceX is planning to launch commercial payloads using Starship no earlier than 2021. In April 2020, NASA selected a modified human rated Starship system as one of three lunar landing systems to receive funding for a 10-month long initial design phase for the Artemis program.

Video credit: SpaceX

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Crew Dragon Demo-2 (officially Crew Demo-2, SpaceX Demo-2, or Dragon Crew Demo-2) was the first crewed test flight of the Crew Dragon spacecraft. The spacecraft, named Endeavour, launched on 30 May 2020 at 19:22:45 UTC and carried NASA astronauts Douglas Hurley and Robert Behnken to the International Space Station in the first crewed orbital spaceflight launched from the United States since the final Space Shuttle mission, STS-135, in 2011, and the first ever operated by a commercial provider. Demo-2 was also the first two-person orbital spaceflight launched from the United States since STS-4 in 1982.

Demo-2 was intended to complete the validation of crewed spaceflight operations using SpaceX hardware and to receive human-rating certification for the spacecraft, including astronaut testing of Crew Dragon capabilities on orbit. During their time aboard, Behnken conducted four spacewalks with fellow American astronaut Chris Cassidy to replace batteries brought up by a Japanese cargo vehicle.

Docking and undocking operations were autonomously controlled by the Crew Dragon, but monitored by the flight crew in case manual intervention becomes necessary. The spacecraft soft docked with the International Space Station at 14:16 UTC on 31 May 2020. Following soft capture, 12 hooks were closed to complete a hard capture 11 minutes later. Hurley and Behnken worked alongside the crew of Expedition 63 for 62 days. Endeavour autonomously undocked from the station at 23:35 UTC on 1 August 2020 and returned the astronauts to Earth on 2 August 2020 in the first water landing by astronauts since 1975.

Endeavour will be refurbished and reused for the SpaceX Crew-2 mission, expected to launch in February 2021. Crew Dragon’s next mission, SpaceX Crew-1 — SpaceX’s first operational astronaut flight — is slated to fly with four Expedition 64 astronauts in late September 2020.

Video credit: NASA/SpaceX