ZLSA Design

SpaceX Falcon 9 landing burn

Sun, 22 Dec 2019 00:00:00 +0000

This piece depicts a Falcon 9 booster in the final stages of its landing burn. The landing legs have been unlatched and are beginning to deploy, the pistons pushing the legs out against the airstream. At the top of the booster, the interstage-mounted grid fins continue to pivot to keep the booster pointed towards the landing pad. Now that the single Merlin 1D engine in the center of the octaweb has slowed the booster down to a near-standstill, the turbopump exhaust flame mostly burns down instead of wrapping around the octaweb and up the side.

Looking closely at the clean white impression of the landing legs on the body, there are seven individual latches on the body to hold the landing leg in-place during ascent and descent. These latches open up at the last minute, just a few seconds before touchdown, and a small starter piston pushes the legs out, giving the primary pneumatic pistons enough mechanical advantage to finish the job. On the right side of the booster, beneath the “U” of the bottom leg, is a small white flap. The flap protects one of two octaweb-mounted quick-disconnects from the chaos of launch and reentry. Before launch, the propellants in the first stage booster are loaded through these quick disconnects.

Technical Details

Everything you see in this piece was created with Blender 2.80, Eevee, and Cycles.

There are two sets of PBR textures for the first stage; each of them is 2048x2048, and are produced with a custom Blender scene and rendered with Cycles. There is an additional “cover” texture, used to mask out the sooty parts of the vehicle. The Falcon 9 here is actually pretty low-poly, at ~40k vertices. The normal maps really bring out the fine details in the legs and the body.

The lens dirt, vignette, and film grain are all pre-rendered in, you guessed it, Eevee. The lens dirt image was created with a particle system, the particles being camera-facing planes with a custom simulated bokeh (to avoid the high render times of real bokeh, which isn’t needed anyway in this case.) The vignette and film grain are both pure shader solutions, rendered to images for compositing.

The Falcon 9 model is fully rigged. The leg pistons slide in and out automatically as the leg bone is rotated. The grid fins are fully rigged as well, and can open, close, and pivot.

Links

The HDRI I used was found at HDRIHaven. Their HDRIs are awesome; go check them out!

Let me know what you think about this piece on Twitter and ArtStation. And if you’d like this as a poster, check it out on RedBubble. I highly appreciate all comments and critiques. Thank you for checking this out!

This is a fan-made render, and no copyright infringement is intended. I believe this work is sufficiently transformative for its use of copyrighted material to qualify as fair use.

Xon Wasp departing Venalis Station

Tue, 03 Sep 2019 00:00:00 +0000

This piece shows the Xon Wasp general-purpose atmosphere-capable jump ship as it travels from Venalis Station to a nearby mining outpost. To conserve fuel, the jump drive isn’t engaged for short moon-to-moon hops like this one. Instead, the trip is performed entirely in normal space, where efficient maneuvers make a real difference.

Background

The Xon Wasp is a marvel of engineering. Design work began in 3242, and after only 9 years — a remarkably short span of time — it was certified for general sale by the International Astronautical Union. As an atmosphere-capable jump ship, it’s a rare breed of spacecraft; able to take off from the surface of an atmospheric planet, travel up to 150 light-years, then rendezvous and dock with a space station. Most ships can do either one or the other, requiring surface-to-orbit shuttles to carry payload to and from the surface of atmospheric planets. This flexibility comes at a cost, though: its size is limited by existing launch infrastructure, and despite its small size, it’s staggeringly expensive. For these reasons, the Wasp is very popular with high-flying executives, heads of state, and other people who need its flexibility and can stomach the price.

In this promotional photo, the Wasp is traveling from Venalis Station to a small mining outpost in the rings of the gas giant. It’s performing its correction burn at its perigee around the asteroid to its left to maximize performace and efficiency. Its primary engines are burning hydrogen, and the reactor is at near-maximum capacity, as evidenced by the glowing radiator panels (only the right-side radiator panel is visible in this photo.)

Inquiries about the Xon Wasp can be made at your system’s Xon shipyard. We look forward to doing business with you.

Technical Details

Everything you see in this piece was created 100% with Blender 2.80 and Eevee (we don’t need Cycles here!) The environment a cubemap, pre-rendered in Eevee; it’s imported directly into the primary scene with a custom cubemap world shader to avoid the distortion from equirectangular projections. The ship itself is rather detailed, with panels being built into the geometry, not delineated with a normal map. (The panels are shrinkwrapped to a hidden “body shape” object to keep their normals consistent even when their shapes are tweaked.) The radiator texture is pre-rendered in Eevee as a grayscale heatmap; the glowing colors are added in the primary scene with a custom shader. The engine volumetric effects are created with judicious use of fresnel and add blending; there are dozens if not hundreds of overlapping meshes at any point in the image.

The lens flares, lens dirt, vignette, and film grain are all pre-rendered in, you guessed it, Eevee. The lens dirt image was created with a particle system, the particles being camera-facing planes with a custom simulated bokeh (to avoid the high render times of real bokeh, which isn’t needed anyway in this case.) The vignette and film grain are both pure shader solutions. The lens flares are created with many layers of custom shaders and exported as high-dynamic-range EXR files to prevent banding or clipping.

Compositing and post-processing are also done in Blender, in a separate file to allow for screen-space effects like lens flare to be created in the 3D Editor. The pre-composite render is not included in this scene; instead, it’s added in the compositor to prevent Eevee’s antialiasing from reducing its quality. The lens flares are 3D elements, positioned on top of the pre-composite render with the help of a reference image. Finally, the composite scene can be rendered, and the final image you see here can be saved.

Illustration for Robert Zubrin's article on Moon Direct for the New Atlantis

Mon, 14 Jan 2019 00:00:00 +0000

This image was commissioned by The New Atlantis to accompany an article about Moon Direct by Robert Zubrin, known for his Mars Direct plan.

The Bearded Dragon

Mon, 26 Nov 2018 00:00:00 +0000

Note

Based on a writing prompt from u/almighty_smiley.

I didn’t want to move to Riverside. I didn’t want to say goodbye to my childhood home, to the friends I’d made, the fun we had. I even began to think fondly of Mrs. Roberts, the history teacher that hated the stunts my friends and I pulled in her classroom. But my father told us that his promotion to manager of the new Riverside branch would give him a substantial raise, and he was dead-set on accepting. I think my mother understood how hard it was for me; she’d told me about her own childhood, and how she had never made any friends because her father was relocated to a different base almost once a year. But she and my father had already decided, and all my pleas fell on deaf ears.

At Riverside, I had no friends. When school started, I didn’t make any friends, either. I was the new kid, the person that nobody knew. I wasn’t bullied or anything; just ignored. It’s a feeling I’m used to, but it still hurt.

And then I met him. Two weeks after school started, he came up to me in the hallway after the bell.

“Hey,” he said, holding his bag in his lap and extending his other hand to offer a handshake. “I’m Sam, and I have a pet lizard at my place. Wanna see it?”

I nodded. Of course I did. I called my mother and asked if it was okay if she picked me up from Sam’s house instead. She hesitated a moment, then tentatively agreed, but only if I called her if anything came up, and to promise that I’d be at the door and ready to go home by 7 pm. I rolled my eyes and agreed, hanging up, and told Sam in a stage whisper that my mother just wanted to avoid a horrific death by ax.

We rolled up to his house from the bus stop, Sam chattering about reptiles and lizards the whole time. “Did you know that dinosaurs were warm-blooded?” he asked me. “Lots of them even had feathers!” And in a dramatic tone, he declared that Jurassic Park had let down science.

His lizard was named Bonnie, but he confided that she was actually male. “The clerk at the store told me Bonnie was a girl,” he defended. “But I think she made it up to get me to leave.”

“Bonnie” was sunning himself when we got to Sam’s room. He had a nice terrarium set out for Bonnie, with dusty yellow rocks and a thin layer of sand on the bottom and a bright yellow lightbulb on top to keep it warm. “Leopard geckos are from the highlands of Asia,” he told me, extending a finger into the terrarium. “So I made sure to give him rocks from his native home.”

We talked for a while, about lizards and many other things. Sam and his dad moved to Riverside a few years ago, and he also had trouble settling in and making friends. He was a voracious reader; he knew all about reptiles, lizards, and even salamanders. “They’re not actually lizards at all, but lots of people don’t realize that,” he told me. “Just because it’s small and has four legs doesn’t mean it’s a lizard. Salamanders aren’t even cold-blooded. Know the difference!”

I was at the door when my mother knocked. Sam’s dad opened the door and invited my mother in, which she did once she looked me once-over to make sure I was still mostly in one piece. She raised her eyebrows at Sam and, seeing his extended hand and serious expression, shook it. When my mother’s back was turned, I rolled my eyes at Sam in the universal “parents, right?” gesture and he cracked a smile.

She asked me about Sam on the ride home, of course. She wanted to know everything about the boy I’d made friends with. As we pulled into our driveway, I told her that I wanted a pet lizard.

Three months later, for my birthday, my parents’ gift was a lizard – a bearded dragon. Thanks to Sam, I now felt like an expert on lizards and reptiles. When my parents told me that the clerk had identified my new lizard as female, I could double-check it. (She was.) My parents had even gotten a terrarium with a layer of store-bought gravel, and my dragon looked happy to be sunning on the gray rock under the heat lamp. In a fit of giddy irony, I named her Clyde.

I thought Clyde’s colors were beautiful. My parents thought her scales were bland and dirty; but among the beige and yellow scales there were black flecks, polished to perfection. Her eyes were expressive, flicking around to stare at something or other. Her minuscule claws, surrounded by tiny, delicate pinpricks of scales, flexing slowly under the warm yellow glow of the lamp. The red spot of scales on the tip of her nose. Even Sam didn’t know how she’d gotten that birthmark.

It took Sam and I a few weeks to transform the terrarium to an Australian paradise for Clyde. We added a thick layer of bone-dry dirt and placed some dusty slabs of orange rock on top. We even added some native Australian plants. I’m not a great judge of reptile expressions, but Clyde seemed to be enjoying her new home.

Two months later, my mom invited Sam over for dinner. Afterwards, we were watching Clyde lying on the rock in his warm terrarium, the cold winter rain pounding at the window. “Hey,” Sam whispered. “Is she supposed to have those nubs at her shoulders?” He pointed at two small bumps under her shoulders, bulging up under her skin.

I frowned and looked closer. I had no idea what it was; I certainly hadn’t seen anything like it. Definitely something to note in my diary.

“I’ve never seen anything like it,” he said, frowning. “It’s probably not bad or anything, but– just keep an eye out, ok? For Clyde’s sake.”

The next morning, Sam texted me. He asked me if I had seen his lucky coin. I hadn’t heard of any such lucky coin, I told him, or I’d love to help him find it. He seemed anxious to get it back. “It’s my lucky coin,” he told me at lunch. “When I was 9, I decided I was old enough to get rid of any kid toys like that. And, you know…” he trailed off, staring over my shoulder into space. “After that, I’ve carried it ever since.” I told him I’d keep an eye out for it.

When I got home, there was a gold coin in Clyde’s terrarium, perched proudly on the biggest rock. I told Sam I’d found his coin, and he was at my bedroom door ten minutes later. He was bewildered.

“It was in my pocket the whole time, like it always is,” he told me as he plucked out the coin, Clyde lethargically stretching out a leg. “I have no idea how it got into Clyde’s terrarium. I don’t even know how it got out of my pocket.” Sam’s dad and my mom were talking downstairs on the doorstep; she asked him how he was handling, and Sam and I winced. Thankfully, his father replied with a short, noncommittal statement, and Sam waved goodbye and headed back home with his dad.

I shook my head at Clyde, who stared at me reproachfully.

A week later, my mom asked me at dinner if I’d seen her wedding ring. I had a sneaking suspicion of where it was, so I headed to my bedroom to check Clyde’s terrarium. Sure enough, there was my mom’s wedding ring and its glint of gold, proudly displayed on Clyde’s rock. I reprimanded Clyde with a look and waved my finger threateningly. I fished out my mom’s ring and returned it to her. I didn’t tell her that Clyde took it, because that would be crazy.

When summer break started, I invited Sam over for a weekend. I showed him some of my writing and scribbles of constellations and far-off galaxies, and he said he liked it; we spent some time working together on a group essay for school (about reptiles, of course.) When Sam was getting ready to leave, we were resting on the deck in the backyard, staring up at the clouds, the fiery fringes of light cast from the setting sun. I watched Sam’s hand on his lap, holding the lucky coin. His hand was playing with the coin, flipping and turning it, the glint of gold from the reflection of the sun dancing around on his shirt. And then, from one moment to the next, it disappeared. Sam didn’t fumble and the coin didn’t fall. It just disappeared.

He jerked upright and stared at his empty hand, and our eyes locked. As quickly as we could, we went inside and into my bedroom, checking Clyde’s terrarium. Sitting proudly on Clyde’s rock was Sam’s coin, shining brightly below the lamp. But not Clyde. I glanced around the room; Clyde was nowhere to be seen.

I moved closer to the gold coin. There was a very distinct mark beneath it on the rock. Trembling, I moved closer and, with two fingers, delicately lifted up the coin to reveal the mark.

It was a burn mark. A small starburst of blackened soot. I retrieved the coin and sniffed the small smudges of soot on my fingertips. Definitely soot.

I looked at Sam; Sam looked at me. We agreed to not tell anybody about what happened. The next morning, looking appropriately distraught, I told my mom that Clyde escaped in the night; she was unhappy, but understanding. It had been a warm night, and I’d left the window open. Clyde could have escaped the cage and gotten outside by himself.

At night, I’d lie in bed and stare at the stars outside, thinking about what it must be like to go there, and trying to not glance at the dark terrarium.

I was the only person to show up at Sam’s 14th birthday party. He didn’t seem to mind it at all. I got him a reptile field guide, all 512 pages of it, with some of my art tucked into the pages, hidden away. He smiled and awkwardly wrapped his arms around me, our parents watching.

We went to his bedroom to watch Bonnie as he languidly climbed along the new row of rocks. We’d moved some of them from Clyde’s terrarium; there was no sense in keeping the rocks there if Clyde wasn’t. I didn’t realize how long we were sitting there, holding hands, until my mom knocked on the door and told me it was time to go home.

That night, while I lay in bed and didn’t stare at the terrarium, I heard a scratch and a faint knock at my window. I tried to ignore it; but then it came again, more insistent this time. The moonlit projection of my window on the bedroom door shifted, just a bit; then, the silhouette of a long, sharp claw slowly moved across the window. I froze for a moment, then slowly turned to look at the window.

There was a lizard outside the window. Its head was five feet wide. There was a lizard outside my window. No, it couldn’t be a lizard, I heard Sam say in my mind. The biggest lizard is the Komodo Dragon, and they only reach 10 feet long. Whatever this is, it’s not a lizard. From my bed, I could see the fringe of scales around its eyes, the sharp reflection from its huge black eyes, and behind it – was that a wing, out in the street?

Quietly, cautiously, I got out of bed and pulled myself to the window, not bothering to use my wheelchair. I held onto the windowsill and looked up, at the dragon, at the spot of red scales on her nose. She nudged the window again with her claw, and I automatically opened it. She extended a single claw into the window and gestured at me to come outside. I nodded, pointing silently at the door and my wheelchair, and she seemed to understand. She fell back onto the lawn, patiently waiting for me. I closed the window and pulled myself into my wheelchair, wheeling out to the front door.

Outside, I stopped on the patio, staring at the dragon. Her wings extended from the side of our house all the way to the sidewalk on the other side of the street, and her legs were the size of tree trunks. She stood nearly 8 feet tall at her shoulders, and her head stood a good two feet above even that. Her thick tongue flicked out for a brief moment; it was nearly as big as me.

Slowly, I wheeled down the path to the driveway under her watchful gaze as she angled her head to keep an eye on me. I reached a foot and stopped, unsure of what to do. Slowly, she lifted it up and beckoned at me, leg set out in invitation. I carefully set the brake on my wheelchair, then pulled myself up to her leg. Climbing up was a little bit awkward; there wasn’t much to grab ahold of, and I didn’t want to hurt her.

It took a while, and twice I needed to stop and rest. Clyde was incredibly patient, though, and let me climb up without fussing at all.

Finally, I pulled myself over her spine, reaching the soft spot behind her shoulders. She peeked back at me, and shook her shoulders, prompting me to grab the spikes near her neck. She snorted and looked ahead, then straightened her wings and jumped straight up into the air, her wings pushing down, rustling the trees and pushing aside a stray garbage can, sending it tumbling down the driveway, a lone styrofoam cup rolling out onto the street.

I looked back at my house until it shrank to nothing, then my neighborhood, and finally the city, too, was left behind. I leaned against Clyde’s shoulder, feeling the muscles harden under her skin as she pulled her wings against the warm summer air. It was glorious, to be so free, and when we leveled off, I patted her shoulder to let her know. But I think she knew, one way or another, how I felt.

Up high, the night sky was beautiful. The faint rainbow brushstrokes of color washing over bright pinpricks of the stars beneath and the slash of the Milky Way. This far from the city, the ground was dark, and the only light we’d find was the occasional yellow wobble of a car on some remote mountain passage. Up high, far above us even now, were the dark trails of jet airplanes crisscrossing the sky. I caught Clyde looking up longingly at them, and I patted her to let her know I understood.

We coasted for hours, just Clyde and I, until the horizon went from black to blue to purple and the stars began to fade. She had brought us back around to the city, and when we were only a few hundred feet away, she flew in a dizzying spiral, landing directly in our front yard. My wheelchair was still there, in front of the door, and the styrofoam cup was still spinning along the street, kicked up by the powerful sweep of Clyde’s wings as she settled down.

“Thanks,” I whispered, sliding off along her leg. “Thank you so much.” She reached out her leg, and I leaned into my wheelchair and settled myself in.

My arms were numb from being still for so long, and my back felt funny. It was the best night of my life. I could feel the smile on my face, the dryness around my eyes, a single tear sliding down. I looked up at Clyde, and she nodded at me, then turned around to face the open street. In a single fluid motion, she pushed her wings down and leapt into the air. I watched her as she flew away, shrinking down to the size of my thumb, to the size of my pinky, then to nothing.

For a moment after she disappeared, I watched the spot where I’d last seen her as the sun crested the horizon and shone its flaming colors into the sky, lighting the clouds and shining down onto my house. For a moment, I pretended I was as free as Clyde; free to go wherever I wished to go, to see whatever I wished to see. But only for a moment.

For my 15th birthday, Sam got me a book about the stars.

A Brief Recap of Reusable Rockets

Wed, 11 Jul 2018 00:00:00 +0000

The Space Shuttle lifts off. Credit: NASA

In the decades since the first rockets flew, the only launch vehicle that was capable of any kind of reuse was the Space Shuttle. And while the orbiter and the solid rocket boosters were recovered after every flight, in-depth inspection and refurbishment was required after each flight. For these reasons, the Space Shuttle cost far more to fly than an equivalent non-reusable rocket. With a total program cost of $196 billion and 135 launches, the Shuttle cost almost $1.5 billion per launch. (It was initially expected to cost about $54 million per launch, adjusted for the USD in 2011.)

One of the major advantages of the Shuttle when compared to other vehicles was its ability to launch both crew and cargo on the same flight. Today, no launch vehicle has the same capability, and there are no serious plans for a spacecraft that launches crew and cargo at once. Despite this advantage, the Shuttle was just too expensive, complex, and unsafe; and in 2011, the Space Shuttle program came to an end.

Reusable rockets aren’t new. Although SpaceX was the first company to successfully recover the first stage of an orbital-class rocket in December of 2015, reusable rockets have been considered since the 1960s. Even the Saturn V, the rocket that launched humans to the Moon, was the subject of multiple proposals that would enable partial recovery of the launch vehicle. In the end, none of these proposals were ever implemented.

The DC-X on its fourth flight Credit: McDonnell Douglas

In the 1990s, McDonnell Douglas began testing the DC-X, an experimental testbed for building rockets capable of vertical landing and takeoff, or VTOL. The DC-X vehicle first flew in 1993, and over the next three years it flew eleven more times. These were all small hops of only one or two kilometers; the final flight reached an altitude of only 2.5 kilometers. Even though it never demonstrated high-altitude flights, it proved that building a VTOL rocket was possible.

The DC-X program was shelved when a landing leg failed to deploy and the rocket tipped over after landing, damaging the aeroshell. NASA did not have the budget to devote to the DC-X program, and it was cancelled in 1996. Several of the remaining DC-X engineers are now involved with Blue Origin, which is working on its own reusable rockets today.

Now, for an explanation of why it’s so easy to reuse airplanes and cars and why it’s so difficult to reuse rockets.

Rockets that reach orbit need to fly very, very fast. There is a huge difference between reaching space, which is only 100km above sea level; and orbit, which requires a velocity of at least 7.6 kilometers per second. That’s 22 times the speed of sound. The only way to get that fast is to bring a lot of fuel with you, and to bring fuel you need a place to store it.

At liftoff, modern rockets are about 90% fuel by mass. Of the remaining 10% mass, the useful payload is usually less than 30% (or 3% of the total vehicle mass at liftoff.) The lighter the rocket, the heavier the payload it can launch into orbit. Everything you add to make a rocket reusable also reduces the maximum payload.

This has made reusable rockets a difficult pill to swallow. The payload capacity would need to be cut nearly in half to make even the first stage reusable, and then you would need to prove that the stage could reliably land and fly again with minimal maintenance. It’s a huge financial gamble that might not even work out.

In 2001, Elon Musk wanted to get the public excited in Mars, to push Congress to increase funding for NASA. He decided to send a greenhouse to Mars, called Mars Oasis; in his words, it would “show great images of green plants on a red background” and “get the public excited [about Mars.]” The greenhouse itself would be relatively simple; but the rocket launch would not. Musk visited Russia three times, attempting to buy used ICBMs; however, they were far more expensive than he thought they would be. On the plane back to the United States after his last trip to Russia, he turned to aerospace consultant and friend Jim Cantrell and said, “I think we can build a rocket ourselves.”

The SpaceX Falcon 1 lifts off from Omelek Island Credit: NASA

In 2002, Elon Musk founded SpaceX with the goal of making life multiplanetary. As he saw it, the issue was that expendable rockets had a fixed cost: because you needed to build a new rocket for each flight, you couldn’t distribute the manufacturing cost of the rocket across all of its flights. Passenger jets cost hundreds of millions of dollars, but the cost is spread out among all the flights. Reusable rockets were key to the dramatic launch price reductions that would make space more accessible.

But before SpaceX could tackle reusability, they needed to build a rocket that could reach orbit. Their first rocket, the Falcon 1, was a 21-meter tall two-stage rocket. Its maiden launch, in 2006, ended in failure after an engine fire; the rocket fell back into the ocean less than a minute after liftoff. The cause was eventually traced to a nut that had corroded after exposure to saltwater spray.

The next two launches did better, with Flight 3 nearly reaching orbit. At this point, though, SpaceX was running low on money for a fourth flight, and Elon had to personally fund the fourth launch of the Falcon 1.

At around the same time, SpaceX President and COO Gwynne Shotwell managed to win SpaceX a NASA contract for the CRS program. Under this contract, SpaceX was to be paid $1.6 billion for 12 resupply missions to the International Space Station. The other winner of the contract, Orbital ATK, was a defense supplier that had already demonstrated dozens of successful orbital launches. For SpaceX to win this contract before they had even reached orbit demonstrated the potential that NASA saw in the SpaceX engineers.

Thankfully, the fourth launch of the Falcon 1 went off without a hitch, as did the fifth. At this point, SpaceX decided to begin the design process on their new Dragon spacecraft and a new rocket: the Falcon 9. These were the vehicles that SpaceX would fly to the ISS under the NASA resupply contract; and in the future, SpaceX would modify the Dragon and Falcon 9 to fly crew.

Although the Falcon 1 never flew again, its legacy lives on in the Falcon 9. Many of the key technologies in the Falcon 9 were proven in the Falcon 1, including the Merlin engines and the tank construction. The Falcon 1 flights even experimented with recovering the first stages with parachutes, but the boosters kept breaking up before the parachutes were even deployed. These lessons were very valuable when SpaceX decided to design recovery systems for the Falcon 9.

The CRS-2 Falcon 9 lifts off, carrying the Dragon capsule to the ISS. Credit: NASA

The Falcon 9 v1.0 is a two-stage rocket standing 54 meters tall. It’s large enough to launch cargo and crew to the International Space Station with the Dragon capsule, and because it has nine engines, it can still complete its mission even if an engine fails during launch.

The Falcon 9 launched for the first time in 2010 and performed flawlessly, deploying a dummy spacecraft into low-Earth orbit. Like on the Falcon 1, SpaceX tried to put parachutes into the Falcon 9 first stage; once again, the stages broke up before the parachutes even had a chance to deploy.

So, in 2011, SpaceX announced that instead of using parachutes to recover the first stage, they’d use actively-guided propulsive landing. This means they’d use the Falcon 9’s engines to guide the booster back to land. This would involve several different maneuvers; first, the booster would need to turn back towards land and restart three engines for the boostback burn; then, it would turn to face engines-first and restart the same three engines to slow it down in the entry burn; finally, as it approached its landing pad, it would start up the single center engine for the landing burn; then, seconds before landing, it would deploy its four landing legs and touch down on land only a few kilometers from its launchpad.

The Grasshopper testbed, in 2012. Note the mechanic standing next to the landing leg. Credit: Steve Jurvetson

However, such a plan would need a lot more fuel. Normally, the first stage engines are shut down and the stages separated only when the fuel is nearly depleted. SpaceX would need to shut the engines off earlier than normal and leave a substantial amount of fuel onboard the first stage. This fuel would be used to reignite the engines to fly the booster back to land. It would also require very accurate control of the booster, or it would land dozens of kilometers off-target, or worse, hit the ground at Mach 1 and explode.

So SpaceX built an experimental rocket, called the Grasshopper. It made eight successful flights in 2012 and 2013, demonstrating accurate throttle and gimbal control of the engine. These flights were all small hops, similar to those made by the DC-X. The Grasshopper vehicle demonstrated stable hovering, horizontal diverts, and on its final flight, reached an altitude of over 700 meters. At this point, SpaceX had reached the limits of the Grasshopper, and the vehicle was retired and replaced with the more capable F9R-Dev1.

The F9R-Dev1 testbed in-flight. Note the four landing legs. Credit: SpaceX

The F9R-Dev1 was a more advanced version of the Grasshopper; where the Grasshopper featured custom landing legs and other hardware, the F9R-Dev1 was a mostly standard Falcon 9 v1.1 booster. Even the landing legs were the prototype carbon-fiber legs that would eventually be used on the Falcon 9. The F9R-Dev1 flew five times, reaching a peak altitude of one kilometer; on its final flight, a blocked sensor caused the vehicle to veer off course, and the flight termination system was triggered, ending the flight.

In 2013, SpaceX flew the first flight of a significantly larger Falcon 9 v1.1, with almost twice the fuel capacity, along with internal modifications that would allow legs and other hardware to be attached. Over the next few flights of the upgraded Falcon 9, SpaceX attempted to perform soft ocean landings to demonstrate the technology; the first successful landing was with the CRS-3 mission. The booster touched down on the ocean’s surface during a storm, and although it splashed down gently, it broke apart when it hit the ocean, as expected.

'Just Read the Instructions', SpaceX's first droneship. Credit: SpaceX

The NS2 booster, the first ever rocket to reach space and land vertically. Credit: Blue Origin

Next, SpaceX needed a place to land. They hadn’t yet built a landing pad, and they also hadn’t received permission to bring a rocket back to land. Ocean landings wouldn’t work; the booster was so tall that it would disintegrate when it fell into the ocean. So they modified a barge, converting it to a powered droneship, and painted a giant “X” on it. It was sent out into the ocean for the first time in 2015, for the CRS-5 mission.

The CRS-5 booster smashing into JRTI Credit: SpaceX

The CRS-5 launch went perfectly, and the Falcon 9 booster performed all the necessary engine burns flawlessly; however, the grid fins used for maneuvering the booster ran out of hydraulic fluid, and the booster smashed into the droneship at highway speeds. Needless to say, the landing was not very smooth, and the only parts that came back were in a pile on the droneship, covered by a tarp.

The next attempt, with the CRS-6 mission, did far better. The booster performed perfectly, but when it was less than ten seconds from landing, an engine throttle valve got stuck, and the booster landed hard and tipped over seconds later. Just like CRS-5, they brought back the remains of the booster in a pile.

On the next launch, with the CRS-7 mission, the launch vehicle failed before there was a chance to attempt a landing, and the CRS-7 Dragon capsule was destroyed. SpaceX was grounded for several months while they solved the issues that caused the CRS-7 failure.

In the meantime, Blue Origin’s experimental test program, shrouded in secrecy for years, announced that their New Shepard rocket had become the first ever rocket to reach space and land vertically. The New Shepard booster, like the Falcon 9, was designed to be reusable; unlike SpaceX, Blue Origin had been planning to land their rockets propulsively from the start, and they had been quietly experimenting with it for over a decade.

The New Shepard vehicle is about 15 meters tall and has many different types of fins to stabilize and control the vehicle as it returns to Earth; notably, at the bottom of the vehicle, there are four maneuvering fins; and at the top of the vehicle, there are drag brakes (to slow the vehicle) and wedge fins (to keep the vehicle stable) mounted to the ring fin.

Whereas the Falcon 9’s purpose is to launch payloads into orbit, the New Shepard is both a testbed and a space tourism platform. It’s capable of launching multiple space tourists to 100km and returning them safely, requiring far less energy than reaching orbit. For this reason, the New Shepard is fully reusable; both the crew capsule and the propulsion module can be recovered and reused for future flights.

The Orbcomm OG2-M2 booster after its landing. Credit: SpaceX

The Iridium-6 fairing just misses Mr. Steven, SpaceX's fairing recovery ship Credit: SpaceX

SpaceX’s next mission was the Orbcomm OG2-M2 launch; the first flight after the CRS-7 inflight breakup. It was also the first Falcon 9 to be powered by densified propellant; this, combined with the lightweight payload, meant that the Falcon 9 booster could return to the launch site.

The flight was picture-perfect, and less than ten minutes after liftoff, the booster touched down smoothly and softly at SpaceX’s landing pad at Cape Canaveral, marking the world’s first recovery of an orbital-class booster.

On March 30, 2017, SpaceX made history when they launched a rocket with a reused booster for the SES-10 mission, cementing SpaceX’s place in history as the first company to ever refly a recovered booster from an orbital-class launch vehicle. This marked a major milestone in the journey for reusable rockets.

Over the next few months, SpaceX continued to recover every core they could, and so far, they’ve recovered 25 more boosters, by land and by sea. Two of these cores were converted into Falcon Heavy side boosters. Alongside a brand-new center core, they launched the Falcon Heavy into space, along with its test payload: Elon’s original Tesla Roadster. The side boosters both flew back and landed at Cape Canaveral, about 100 meters and 3 seconds apart.

While it’s not economically sensible to recover and reuse the Falcon 9 upper stage, SpaceX is working hard at recovering the Falcon 9 fairings. Combined, they cost about $6 million (about 10% of the total cost of the rocket), and they take up a substantial amount of floor space in the factory to build.

The NS2 booster, underneath the crew capsule at the moment of abort motor ignition. Credit: Blue Origin

In September of 2016, SpaceX announced their Interplanetary Transportation System, a rocket SpaceX hopes will begin the colonization of Mars. Both the first and second stages will be recovered and reused on every launch, dramatically reducing launch prices and opening up whole new worlds of human space exploration. SpaceX plans to reuse the booster a staggering 1,000 times; the propellant tanker and Mars lander are planned to be reused 100 and 12 times, respectively. These numbers bring Mars colonization within reach for the first time ever.

The final flight of the Blue Origin NS2 vehicle was in 2016, with the crew capsule performing an in-flight abort to verify the safety of the crew in the case of a booster failure. Miraculously, the booster survived the heat and debris from the solid rocket motor exhaust, then proceeded to continue its flight to space. Only a few minutes later, it performed a smooth landing on its landing pad. The booster was retired, and Blue Origin plans to perform more test flights this year. They’re planning to fly crew by the end of 2018.

Recently, Blue Origin unveiled their proposed orbital launch vehicle, the New Glenn. Like the Falcon 9, the first stage is built to be reusable; it will land itself on a ship in the ocean under its own engine power. Blue Origin is currently building a factory for the New Glenn at Cape Canaveral, and they hope to perform the first flights of the new vehicle by 2020.

With Blue Origin and SpaceX both demonstrating that booster reuse is possible, it now falls to the rest of the industry to follow along. Soon, the price for a launch on a reused rocket will drop, and the entire launch industry will need to lower their prices to remain competitive. I, for one, cannot wait for the low-cost future of spaceflight, where launches don’t cost tens or hundreds of millions of dollars; where you don’t need to be a giant international corporation to launch your satellites.

And just maybe, a future where your address will need to specify a planet.

SpaceX BFR 3D model

Sun, 24 Jun 2018 00:00:00 +0000

This is a 3D model of the SpaceX BFR spacecraft.