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Warp drives have a long history of not existing, despite their ubiquitous presence in science fiction. Writer John Campbell first introduced the idea in a science fiction novel called Islands of Space. These days, thanks to Star Trek in particular, the term is very familiar. It’s almost a generic reference for superliminal travel through hyperspace. Whether or not warp drive will ever exist is a physics problem that researchers are still trying to solve, but for now, it’s theoretical.

Recently, two researchers looked at what would happen if a ship with warp drive tried to get into a black hole. The result is an interesting thought experiment. It might not lead to starship-sized warp drives but might allow scientists to create smaller versions someday.

NASA’s Eagleworks attempted to test Alcubierre warp drive concept. Credit: 2012

Remo Garattini and Kirill Zatrimaylov theorized that such a drive could survive inside a so-called Schwarzschild black hole. That’s provided the ship crosses the event horizon at a speed lower than that of light. Theoretically, the black hole’s gravitational field would decrease the amount of negative energy required to keep the drive going. If it did, the ship could pass through and somehow use it to get somewhere else without getting crushed. Furthermore, the mathematics behind this idea points the way toward the possible creation of mini-warp drives in lab settings.

What’s a Warp Drive?

Could scientists build a micro- or mini-warp drive in the lab? Good questions. To understand the team’s work, let’s look at the major players in this research: warp drives and black holes.

The idea is inspired by the fact that nothing can go faster than light speed. Given the distances in space, traveling to the nearest star would take years (if we could go at light speed). Going across a galaxy or to more distant galaxies would take years and many lifetimes. So, if you want to be a space-faring species, you must travel faster than light (FTL).

How would you do that? This is where warp drives come in. Theoretically, they allow you to put your spaceship inside a bubble that could slip through space at FTL speeds. That’s how the starships in Star Trek (and other SF stories) get across huge distances so quickly. The Star Trek ships use an energy source in a “warp core” to power warp field generators. They create the warp bubble in subspace. The ship uses that to go wherever the crew needs to be.

Do Physicists Like Warp Drive?

Such a warp drive is a tantalizing idea with many caveats. For example, generating a warp field requires an insane amount of energy. Some physicists suggest that it would take more energy than we’re capable of generating. Creating that energy would require huge amounts of exotic matter—something like “unobtanium”. So, that’s a problem right there.

Others say that creating such a drive goes against our current understanding of spacetime physics. However, that hasn’t stopped anybody from speculating on ways to make it happen. For example, Mexican physicist Miguel Alcubierre had an idea for such a drive in 1994. He suggested that it could create a bubble that would shift space around an object. He has continued his research about a ship that could get somewhere faster than light. However, he and others still point out various problems with both creating and sustaining a warp drive. That includes the idea that such a drive effectively isolates itself from the rest of the Universe. Among other things, it means the ship can’t control the drive that’s making it go. So, there are a still few bugs to work out.

This artist’s illustration shows a spacecraft using an Alcubierre Warp Drive to warp space and ‘travel’ faster than light. Image Credit: NASA About Black Holes

We are most familiar with black holes in terms of stellar mass and supermassive ones. These also sport accretion disks that convey material into the black hole. For example, the central supermassive black hole named Sagittarius A* in our own Milky Way Galaxy periodically gobbles down material. Then, it emits a belch of radiation. Other, more active galaxies send out jets of material emitted as the central supermassive black hole feeds continuously.

Simulation of a black hole. (Credit: NASA/ESA/Gaia/DPAC)

A black hole is a concentration of mass with gravity so strong that nothing, even light, can escape. In their study about black holes and warp drives, the authors used Schwarzschild black holes. These so-called simple “static” black holes curve spacetime, have no electric charge and are non-rotating. Essentially, they are good approximations for mathematical explorations of the characteristics of slowly rotating objects in space.

When A Ship with Warp Drive Crosses into a Black Hole

The Schwarzchild black hole is the “perfect” black hole to use in this theoretical exploration of a warp drive crossing the event horizon. To figure out the scenario, Garattini and Zatrimalov decided to mathematically combine the equations describing the black hole and the ones describing the warp drive. Among other things, they found that it’s possible to “embed” the warp drive in the outer region of the black hole. The warp bubble itself is much smaller than the black hole and needs to be moving toward it. The black hole’s gravity affects the energy conditions needed to create and sustain the warp drive. That means you can theoretically decrease the amount of negative energy required to sustain the warp bubble. In addition, the researchers suggest that if the warp bubble is moving at less than the speed of light, it effectively erases the black hole horizon.

The research team also described the idea that such an occurrence could evoke the conversion of virtual particles into real ones in an electric field. If so, it could lead to the creation of mini warp drives in the lab.

Changing the Black Hole a Bit

Interestingly, the team also suggests that, if the warp bubble is moving slowly and is much smaller than the black hole horizon, it could increase the entropy of the black hole. However, as they state in their closing arguments, “there are potential problematic issues in other physical situations: namely, when the warp drive is completely absorbed by the black hole, it may decrease its mass, and, therefore, its entropy.

Likewise, when there is a larger warp bubble passing through a black hole, it would produce a ”screening” effect and de facto eliminate the horizon, making it impossible to define the black hole entropy in the Hawking sense. If warp drives are possible in nature, these issues indicate that we still do not understand them from the thermodynamic point of view.”

Warp Drive Technology Remains to be Seen

So, while this research may prove valuable theoretically, and could lead to lab production of mini black holes, many questions remain. Perhaps in the future, when we understand the quantum mechanics behind both of these objects, we might find warp technology a slam-dunk. If so, then, as ships travel through black holes, we could face a weird time. For example, signals from inside a black hole could get carried out by a warp bubble merging from the singularity. That would allow us to send images or recordings of what it’s like inside the event horizon—something nobody knows about today. There’s also a chance that those fearsome black holes could make a warp drive less difficult to achieve since they won’t need so much exotic “negative energy” source material.

For More Information

Black Holes, Warp Drives, and Energy Conditions
The Warp Drive: Hyper-fast Travel Within General Relativity
Schwarzschild Black Hole Simulations

The post What if you Flew Your Warp Drive Spaceship into a Black Hole? appeared first on Universe Today.

In 2022, NASA’s DART (Double Asteroid Redirection Test) spacecraft collided with an object named Dimorphos. The objective was to test redirecting hazardous asteroids by deflecting them with an impact. The test was a success, and Dimorphos was measurably affected.

Follow-up research shows that Dimorphos was more than deflected; it was deformed.

In recent decades, we’ve made progress cataloguing the asteroids in the Solar System. Some of them are close enough to Earth to be dangerous. If an object comes within 1.3 astronomical units of the Sun, it’s called a Near Earth Object (NEO.) If it’s more than 140 meters (460 ft) across and crosses Earth’s orbit, it’s called a Potentially Hazardous Object (PHO.) Over 99% of NEOs and PHOs are asteroids, and the remainder are comets.

Earth has suffered many impacts from these objects in the past. The most famous impactor was Chicxulub. When it struck Earth about 65 million years ago, it was responsible for the end of the dinosaurs.

Now that we know the danger these tumbling space rocks pose, NASA and other agencies are preparing to do something about it. DART was a test mission to see how effective a simple kinetic impactor could be at changing the trajectory of an asteroid.

JWST captured this sequence of the DART collision on Dimorphos. Courtesy NASA, ESA, CSA, and STScI.

Dimorphos doesn’t pose any threat to Earth. It was chosen as the test target because it’s actually one part of a pair of objects. Dimorphos is a tiny moon of an asteroid named 65803 Didymos. Because Dimorphos is in orbit around Didymos, it’s easy to measure changes in the object’s movement after the impact.

An entire team has been following Dimorphos since DART impacted it to track how the object’s orbit has changed. Their observations show that the test was a success. Dimorphos’ orbit around Didymos was shortened by 32 minutes when the objective was to shorten it by only 73 seconds. Interestingly, it wasn’t the impact that affected Dimorphos’ orbit; it was because of the recoil effect from the ejected debris.

New research published in The Planetary Science Journal shows that Dimorphos was more deeply affected by the impact than thought. The paper is titled “The Dynamical State of the Didymos System before and after the DART Impact.” The lead author is Derek Richardson from the Department of Astronomy at the University of Maryland. Richardson is the team leader for one of the DART investigation teams called the Dynamics Working Group.

“For the most part, our original pre-impact predictions about how DART would change the way Didymos and its moon move in space were correct,” said Richardson. “But there are some unexpected findings that help provide a better picture of how asteroids and other small bodies form and evolve over time.”

Pre-impact observations showed that Dimorphos had an oblate shape. But after the impact, it became prolate or elongated. This went against pre-impact observations, which suggested that Dimorphos was initially elongated.

DART had a mass of 610 kilograms (1,340 lb) and struck Dimorphos at a speed of about 21,000 km/h (13,000 mp/h). The impact had a force equivalent to about three tons of TNT exploding and unexpectedly altered Dimorphos’ shape.

“We were expecting Dimorphos to be prolate pre-impact simply because that’s generally how we believed the central body of a moon would gradually accumulate material that’s been shed off a primary body like Didymos. It would naturally tend to form an elongated body that would always point its long axis toward the main body,” Richardson explained.

“But this result contradicts that idea and indicates that something more complex is at work here. Furthermore, the impact-induced change in Dimorphos’ shape likely changed how it interacts with Didymos,” Richardson said.

Didymos and Dimorphos are connected gravitationally, and after the impact, scattered debris from Dimorphos altered their relationship, reducing Dimorphos’ orbit around Didymos. It isn’t certain yet, but Dimorphos may have entered a tumbling state.

Image captured by the Italian Space Agency’s LICIACube a few minutes after the intentional collision of NASA’s Double Asteroid Redirection Test (DART) mission with its target asteroid, Dimorphos, captured on Sept. 26, 2022. Credits: ASI/NASA

“Originally, Dimorphos was probably in a very relaxed state and had one side pointing toward the main body, Didymos, just like how Earth’s moon always has one face pointing toward our planet,” Richardson explained. “Now, it’s knocked out of alignment, which means it may wobble back and forth in its orientation. Dimorphos might also be ‘tumbling,’ meaning that we may have caused it to rotate chaotically and unpredictably.”

If it’s tumbling, Dimorphos could cause problems—not for Earth but for Hera, the follow-up mission.

The ESA’s Hera mission will be launched in a few weeks. Its mission is to perform a detailed post-impact survey of Dimorphos. To do that, it needs to get close. If Dimorphos is tumbling, its orbit is less predictable, and that will make it difficult for Hera to get close. If that’s the case, the data Hera collects will suffer. It’s possible that, over time, secular damping will calm the tumbling, but there’s a lot of uncertainty at this point.

“While secular damping is possible in the near future, it is unlikely to have major effects on the system when Hera arrives. Thus, Hera may encounter a tumbling Dimorphos, complicating proximity operations,” Richardson and his co-authors write in their research.

DART changed the mutual orbit of Didymos and Dimorphos, and it also changed their orbit around the Sun. The initial impact wasn’t entirely responsible for this change. The ejecta also contributed. “The initial impulse delivered to the system’s barycenter was augmented by the momentum carried by the ejecta that escaped the system,” the authors explain.

Many different researchers have calculated the ejecta, and different observations have arrived at different amounts. However, the researchers say that the impact ejected some tens of millions of kg of material.

This figure from the research shows the fate of the material ejected by the impact. Image Credit: Richardson et al. 2024.

The impact could change Didymos’ shape, too. It spins so fast that it’s at greater risk of structural failure when ejecta from Dimorphos strikes it. “Small perturbations, such as ejecta from the impact site on Dimorphos striking Didymos at various speeds, could thus trigger a reshaping process, wherein its equatorial radius increases while its polar radius decreases, resulting in a more oblate shape,” the authors explain.

The impact generated so much ejecta that Dimorphos formed a tail. Some of that debris had to have landed on Didymos, but observations so far show that it hasn’t affected its surface or its dynamics. “This implies Didymos’s surface was strong enough to withstand such impacts,” the authors write. However, in the past, Didymos likely suffered some type of fracturing, possibly due to its fast spin rate, and debris from that event likely formed Dimorphos.

The impact results are uncertain. DART carried a secondary Italian spacecraft named LICIACube (Light Italian CubeSat for Imaging of Asteroids) that separated from DART 15 days prior to impact. It drifted past the asteroid and captured images of the asteroid and the ejecta with its pair of cameras. LICIACube’s observations helped scientists understand what happened, but the small CubeSat executed only a single flyby.

These images show the DART impact as seen by LICIACube. The left panel shows an approach observation 156?seconds after impact, with the ejecta in front of and partially obscuring Dimorphos. The right panel shows the ejecta morphology after close approach, 175?seconds after impact, with Dimorphos silhouetted against the ejecta cone. Image Credit: Cheng et al. 2023. CC BY 4.0

It’s up to the ESA’s Hera spacecraft to answer questions about the impact. It’ll reach Didymos in October 2026, and in December, it will begin about six months of proximity operations. “The primary goal of Hera is to measure the mass of Dimorphos,” the authors write.

The mass is the missing piece that will help us understand how the ejecta contributed to Dimorphos’ altered orbit. Hera also has two CubeSats, Juventas and Milani, and all three will work together to constrain Dimorphos’ mass more precisely. “Once Hera gets closer, its Radio Science Experiment (RSE), involving the main spacecraft and the two CubeSats, Juventas and Milani, should obtain Dimorphos’s mass to higher precision and measure the extended gravity fields and rotational states of both Didymos and Dimorphos,” the paper states.

When you smash an impactor into an asteroid, you can expect some unintended results. But if asteroid redirection is to serve as a tool to protect Earth from dangerous impacts, then we need to know in as much detail as possible what to expect. That’s what DART and Hera are all about. However, they’re also telling us about the relationships between small binary objects.

“The DART mission, together with the Didymos observing campaign, not only represented the first test at a realistic scale of a hazard mitigation technique but also provided unprecedented measurements of dynamical effects in a nonideal small solar system binary for testing theoretical models,” the authors write.

Many of the pre-impact predictions turned out to be true, but other results are surprising, and there are plenty of unanswered questions.

“We look forward to revelations from the Hera mission, which promise to further refine our understanding of small bodies in general and the formation and evolution of binary asteroids in particular,” the researchers conclude.

The post DART Did More Than Deter Dimorphos; It Sent It Into a Chaotic Tumble appeared first on Universe Today.

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