Day: August 20, 2018

For the last year or so, Stratolaunch has conducted a number of ground-based tests on the world’s largest aircraft, both inside its gargantuan hangar and on a runway in Mojave, California. If all goes well, the company plans for the aircraft with a 117-meter wingspan to make its maiden flight by the end of this year.

But the aircraft is only a means to an end—sustainably launching rockets into space. Although Stratolaunch appears to have built a fine airplane, questions have lingered for years regarding exactly which rockets will be flown to a cruising altitude, and then released by the airplane. And when you’ve built an aircraft the likes of which have never been seen before, such curiosity is understandable.

On Monday, the company finally provided some additional clarity. Previously, Stratolaunch announced an agreement to launch small Pegasus rockets from the aircraft, but these boosters can only deliver up to 370kg into low-Earth orbit. (And they are so small, their use could not possibly justify the scale of the Stratolaunch plane, with a wingspan 20 meters greater than even the Spruce Goose).

Fortunately, the new rockets announced this week will have significantly more capacity, and they appear be right-sized for this very large, mobile launch platform:

• Medium Launch Vehicle: A new medium-class air-launch vehicle optimized for short satellite integration timelines, affordable launch, and flexible launch profiles (3.4 ton capacity to LEO).
• Medium Launch Vehicle – Heavy: A three-core MLV variant with capability to deploy heavier payloads to orbit (6 tons to LEO).
• Medium Launch Vehicle – Reusable: A fully reusable space plane that enables advanced in-orbit capabilities and cargo return; Initial designs optimized for cargo launch, with a follow-on variant capable of transporting crew.

According to Stratolaunch, the medium launch vehicle is under development, with a maiden launch targeted for 2022. The heavier version of this rocket is undergoing “early development,” and the company is performing a “design study” of the space plane. Earlier, Stratolaunch dubbed this space plane concept “Black Ice.”

“We are excited to share for the first time some details about the development of our own, proprietary Stratolaunch launch vehicles, with which we will offer a flexible launch capability unlike any other,” said Jean Floyd, Chief Executive Officer at Stratolaunch, in a news release. “Whatever the payload, whatever the orbit, getting your satellite into space will soon be as easy as booking an airline flight.”

Stratolaunch released no additional details about these rockets, such as the engines they will use. Even so, the moment feels significant, as Stratolaunch has long been searching for appropriate rockets to be launched from its aircraft. An earlier deal with SpaceX fell through, as well as a deal with Orbital ATK to develop a custom rocket for the aircraft. Now, the company has decided to go in-house and just build its own rockets.

Relativity is one of the most ambitious companies in the rocket industry. It seeks to manufacture the entirety of its rockets using 3D printing techniques, hoping to one day print a rocket on the surface of Mars to launch from there. But are either of these goals achievable?

Some new moves by the company suggest they just might be. On Monday morning, Relativity will announce the hiring of Tim Buzza as an adviser to shepherd the company’s launch vehicle execution. These duties will include finalizing the selection of a US-based launch site (a decision will come before the end of this year) and overseeing development of ground launch systems at that site.

Buzza is a well-known figure in the aerospace industry. He was employee number five at SpaceX, having hired on in 2002, and over a 12-year career ended up as the company’s vice president of launch operations. In an oral history interview in 2013 with NASA, Buzza explained his early duties at SpaceX.

“I got to work at SpaceX from the beginning working on Falcon 1, and I initially was hired in to run the testing,” Buzza said. “Because the test site in Texas became so similar to what a launch site should be like, I then was given the responsibility for the initial launch site at Vandenberg Air Force Base. Then we moved to Kwajalein and built a launch site there. Completed our Falcon 1 development in Kwajalein and then moved on to Cape Canaveral for Falcon 9.”

This significance of this experience, clearly, is that Buzza has seen what it takes to get from the development stage of a rocket into space. Buzza has experiences with avionics, propulsion, and launch software. “The guy literally knows everything there is to know about rockets,” said Tim Ellis, the cofounder and chief executive of Relativity, in an interview with Ars.

Since leaving SpaceX in 2014, Buzza has spent the last four years at Virgin Galactic and then Virgin Orbit, helping that company bring its LauncherOne rocket to readiness. If all goes well, that vehicle should launch later this year.

Printing certification

Relativity also says that it has made significant progress toward its goal of printing an entire rocket, from the engines up to the payload fairing, with its “Stargate” 3D printer. Ellis said the company recently printed its first materials that passed the most stringent specification for fusion-welded materials in the aerospace industry, a standard known as AWS D17.1 Class A.

The significance of this, Ellis said, is that it demonstrates that the 3D printing process it is using for its engines and rockets meets the highest quality level of the aerospace industry. “So many people question or ask us if 3D printed materials are strong enough,” said. “This gives our customers the highest confidence that it is.”

The next time you’re stuck in traffic, consider taking a cue from the lowly ant. Fire ants may hold the secret to regulating traffic flow, whether it be dealing with cars packed on a freeway during rush hour, shepherding crowds through narrow passageways, or coordinating swarms of robots.

“Ants that live in complex subterranean environments have to develop sophisticated social rules to avoid the bad things that can happen when you have a lot of individuals in a crowded environment,” said Georgia Tech physicist Daniel Goldman, who has been studying fire ants for years and is co-author of a new paper in Science detailing how they optimize their tunnel-digging efforts.

In a jam

Physicists have long been fascinated by traffic jams, especially so-called “phantom” traffic jams (aka, “jamitons”), where there doesn’t seem to be any good reason for the slowdown. It all comes down to density and the physics of self-organization. Traffic moving freely “flows” like a liquid. Traffic jammed to a standstill is akin to a solid.

But there’s a special state in between that German physicist Boris Kerner dubbed “synchronized flow.” It’s where car density reaches a critical threshold and vehicles become highly correlated with other, moving in unison. Here, the slightest perturbation, even if it’s a single driver braking suddenly, sends little ripples through the chain of cars behind. It’s an example of emergent collective behavior, and it’s one reason why slowdowns typically occur near merge points.

Fire ants (and ants in general) provide another textbook example of collective behavior. A few ants spaced well apart behave like individual ants. But pack enough of them closely together, and they behave more like a single unit, exhibiting both solid and liquid properties. You can pour them from a teapot like ants, as Goldman’s lab demonstrated several years ago, or they can link together to build towers or floating rafts–a handy survival skill when, say, a hurricane floods Houston. So it’s not surprising that they also excel at regulating their own traffic flow. You almost never see an ant traffic jam.

Here’s why. In 2008, German scientists built a tiny ant motorway, complete with the equivalent of highway interchanges, so that the ants in their laboratory could navigate between their nest and a sugary food source. Then they monitored how the ants quickly found the shortest possible route between the two. You’d expect jams to form near interchanges, as they do on human highways during rush hour. Instead, whenever a route started to clog, the ants returning to the nest with sugar blocked ants traveling in the opposite direction toward the nest, forcing them to find an alternate route.

Uncooperative

It’s more difficult to get human drivers to alter their behavior for the collective good. Aided by apps like Waze and Google Maps, we generally take whatever is the quickest route for us, with nary a thought about how this affects traffic patterns at large or our fellow drivers. That’s one reason why just widening highways doesn’t really reduce congestion—there’s an inherent conflict of interest between what benefits us personally and what benefits us collectively, so the result is 30 percent longer commute times, per another 2008 study. (The authors dubbed it the “Price of Anarchy.”) But shutting down a few select streets—akin to blocking oncoming ants—forced drivers to act like the ants and find alternate optimal routes, even if they didn’t consciously do so.

Now there are some new insights into the issue, thanks to Goldman’s crew in Georgia. The group first collected ten nests of fire ants over three summers and set up colonies of 30 ants each in the laboratory, housed in transparent containers filled with glass particles to simulate soil. They painted individual ants different colors, the better to track them for the experiments. Then they let the ants go about their business digging vertical tunnels in their containers for 48 hours, all under the watchful eye of a video camera. Those tunnels are narrow, with barely enough room for two ants to pass, yet jams rarely happened.

Why? When an ant encounters a tunnel in which other ants are already working, it retreats to find another tunnel. It also helps that only a small fraction of the colony is digging at any given time: 30 percent of them do 70 percent of the work.

According to Goldman, this inequality among worker ants actually benefits the community, ensuring that the digging gets done efficiently with minimal delays while expending the least amount of energy. But don’t assume that the idle ants are lazy: when the scientists removed five of the hardest working ants, other members the colony stepped in to keep the work flowing smoothly.

To find out if this optimization strategy might work more broadly, one of Goldman’s graduate students built ant-like robots and programmed them to dig through 3D printed magnetic plastic balls designed to simulate moist soil. The robots traveled along narrow tracks, mimicking the narrow tunnels of the ants. The researchers found that up to three robots could efficiently dig together, but adding a fourth jammed up the process and work came to a halt.