NASA Astronomy Picture of the Day

July 27, 2023

Galaxies in the River

Large galaxies grow by eating small ones. Even our own galaxy engages in a sort of galactic cannibalism, absorbing small galaxies that are too close and are captured by the Milky Way's gravity. In fact, the practice is common in the universe and illustrated by this striking pair of interacting galaxies from the banks of the southern constellation Eridanus, The River. Located over 50 million light years away, the large, distorted spiral NGC 1532 is seen locked in a gravitational struggle with dwarf galaxy NGC 1531, a struggle the smaller galaxy will eventually lose. Seen nearly edge-on, spiral NGC 1532 spans about 100,000 light-years. The merging galaxies are captured in this sharp image from the Dark Energy Camera mounted on the National Science Foundation’s Blanco 4-meter Telescope at Cerro Tololo Inter-American Observatory in Chile. The NGC 1532/1531 pair is thought to be similar to the well-studied system of face-on spiral and small companion known as M51.

https://apod.nasa.gov/apod/astropix.html?

>>19250702

NASA, DARPA Partner with Industry on Mars Rocket Engine

Jul 26, 2023

NASA and the Defense Advanced Research Projects Agency (DARPA) announced Wednesday Lockheed Martin of Littleton, Colorado, as the prime contractor for the design, build, and testing of NASA and DARPA’s nuclear-powered rocket demonstration, in collaboration with other industry partners.

The Demonstration Rocket for Agile Cislunar Operations (DRACO) program will test a nuclear-powered rocket in space as soon as 2027.

"Working with DARPA and companies across the commercial space industry will enable us to accelerate the technology development we need to send humans to Mars," said NASA Deputy Administrator Pam Melroy. "This demonstration will be a crucial step in meeting our Moon to Mars objectives for crew transportation into deep space."

NASA and DARPA partnered on the DRACO program to advance development of nuclear thermal rocket technology, supporting both agencies' goals. For NASA, nuclear propulsion is one of the primary capabilities on the roadmap for crewed missions to Mars.

A nuclear-powered rocket would allow for a shorter, faster trip to the Red Planet, reducing the mission's complexity and risk for the crew. This type of rocket can be more than twice as efficient as conventional chemical rockets, meaning it requires significantly less propellant and could carry more equipment for scientific goals. A nuclear-powered rocket also could provide more power for instruments and communications systems.

Under the terms of its agreement with DARPA, Lockheed Martin is responsible for spacecraft design, integration, and testing.

BWX Technologies, based in Lynchburg, Virginia, is responsible for the design and build of the nuclear fission reactor that will power the engine. NASA's Space Technology Mission Directorate (STMD) is responsible for the overall management and execution of the nuclear-powered DRACO engine.

“Through NASA’s prior investments – in collaboration with the Department of Energy – we’ve supported the commercial sector to grow their capabilities in nuclear propulsion technology,” said Dr. Prasun Desai, acting associate administrator for STMD at NASA Headquarters in Washington. “Now, those investments are coming full circle as we work with these same companies to build the first nuclear-powered rocket to fly in space."

In addition to the DRACO program, NASA also works with the Department of Energy and industry on other space nuclear technology initiatives, including Fission Surface Power and a separate effort to explore possible designs for future nuclear thermal spacecraft.

NASA is committing up to $300 million toward the DRACO partnership. This includes up to $250 million in costs for the design and development agreement for the nuclear-powered engine, as well as technical oversight and expertise from agency personnel.

The U.S. Space Force will provide the DRACO launch and launch site support.

https://www.nasa.gov/directorates/spacetech/nasa_darpa_industry_partner_mars_rocket_engine

Aeolus satellite reentry: the breakdown

July 26, 2023

After a remarkable life in orbit, Aeolus is out of fuel and out of time – it’s returning to Earth this week. Planned and built before any regulations were put in place on ‘end-of-life’ disposal, the Earth Explorer was designed to naturally return through our atmosphere.

After months of detailed planning and analysis, ESA together with industrial partners has designed a complex and never-before-performed set of manoeuvres to control, as much as possible, Aeolus’ fall.

The assisted reentry attempt is built on four main phases, now begun at ESA’s mission control:

Phase I: once Aeolus has fallen naturally to 280 km, the first manoeuvre is performed – the largest in the mission’s five years in orbit. The main objectives are to lower the satellite down to 250 km and to check how the satellite behaves when executing a large manoeuvre at such low altitudes – more than three times the size of any performed during routine operations.

Phase II: after three to five days, a series of four manoeuvres will lower Aeolus’s ‘perigee altitude’ – the point in orbit closest to Earth – down to an altitude of about 150 km.

Phase III: a final manoeuvre will lower Aeolus to a perigee altitude of 120 km.

Phase IV: in the final, shortest phase, Aeolus the spacecraft becomes space debris, completing its final descent in just a few Earth revolutions.

In this animation, round regions temporarily lit up in bright green show the moments that Aeolus is in contact with antennas on Earth. It is in these periods that mission control is in touch with the satellite and can send up commands and get its data down.

Aeolus is repeatedly turned, or ‘slewed’ by 180° in order to switch from the routine orientation (or ‘attitude’), in which the satellite’s ‘X-band’ antenna points toward Earth and the GPS can function to track the mission – crucial to maintaining knowledge of its position – and the ‘retrograde’ attitude.

This second, ‘upside down’ position is necessary for the thrusters to fire in the opposite direction to Aeolus’s flight direction, causing it to lose energy and lower in orbit.

While the ultimate goal is for the spacecraft to burn up as it reenters through the atmosphere, teams need to keep it functioning long enough that they can continue to send up commands and control it on its path.

After the final commands are sent, Aeolus will be ‘passivated’. Passivation is when any energy onboard a spacecraft is removed, for example, its propellant or batteries. Doing this prevents explosions and fragmentation events, that could cause the release of lots of pieces of unwanted space debris.

For Aeolus, already out of fuel, it will simply be turned off. After this point, teams at mission control will continue to monitor the situation until Aeolus’s ultimate reentry location is confirmed.

For rolling updates on Aeolus's reentry, follow ‘Aeolus reentry: live’ on the Rocket Science blog.

https://www.esa.int/ESA_Multimedia/Videos/2023/07/Aeolus_reentry_the_breakdown

https://blogs.esa.int/rocketscience/2023/07/24/aeolus-reentry-live/