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takyon writes:

SpaceX's Starship and Super Heavy (formerly Big Falcon Spaceship and Big Falcon Booster, or Big Falcon Rocket) have undergone further changes following a "final" iteration of the design in September. Elon Musk also said that a downscaled Starship hopper (for vertical takeoffs and landings) will "hopefully" be tested starting in March or April 2019, which is months sooner than a "late 2019" estimate made by SpaceX CEO Gwynne Shotwell in September.

Recent photos taken of SpaceX's operation in Boca Chica, Texas have shown a stainless steel nose cone being built. The new stainless steel design was confirmed by Elon Musk, along with numerous other details. Musk said that stainless steel can beat carbon fiber composites due to its superior strength-to-mass ratio and "mirror-like" thermal reflectivity. SpaceX is using an on-site foundry to create its own steel "superalloy", although some steel parts will be made by a supplier. Finally, the test hopper will feature three "radically redesigned" Raptor engines while being slightly shorter than the full-scale Starship, although it will share the same 9-meter diameter:

While the suggestion that Raptor's turbopumps (basically fuel pumps) would need at least 100,000 HP per engine seems to indicate that the flight design's thrust has been appreciably uprated, a past figure of ~2000 kN (450,000 lbf) per engine suggests that Starship V0.1 could weigh as much as an entire Falcon 9 Block 5 rocket (~1.2 million pounds, 550,000 kg) and still having a solid 80-100% of Falcon 9's liftoff thrust. Put simply, the rocket that appears to be coming together in the boonies of South Texas could rival almost any other liquid fuel rocket booster in service, while still being the testbed for BFR's upper stage alone.

While it's ambiguous if several additional comments applied to the Starship prototype, the final product, or both, Musk also indicated that some of the biggest benefits of a shift away from carbon composites to stainless steel would be relative ease with which the material handles extreme heating. Thanks to the fact that stainless steel can ultimately be polished to mirror-like levels of reflectivity and that mirrors are some of the most efficient reflectors of thermal energy (heat), shiny and unpainted steel would ultimately perform far better than carbon composites and could end up requiring "much less" heat shielding for the same performance.

Perhaps most unintuitive is the fact that steel can apparently beat carbon composites when it comes to usable strength-to-weight ratios at supercool temperatures. According to Musk, steel also performs "vastly better" at high temperatures and appreciably better at room temperatures. A comment made on Saturday may lend additional credence to what seems at face value to contradict basic material intuition – at least some of the stainless steel SpaceX is examing would be a special (presumably SpaceX-engineered) alloy that has undergone what is known as cryogenic treatment, in which metals are subjected to extremely cold conditions to create some seriously unintuitive properties. Ultimately, cold-formed/worked or cryo-treated steel can be dramatically lighter and more wear-resistant than traditional hot-rolled steel.

Elon Musk hinted at a "delightfully counter-intuitive" redesign in November, which was almost certainly a reference to the use of stainless steel instead of carbon fiber composites. Here's a video (10m14s) which offers some speculation about how a steel Starship could effectively conduct and radiate away heat.

Also at Business Insider.

Original Submission

takyon writes:

Popular Mechanics has interviewed SpaceX CEO Elon Musk about his decision to move to a stainless steel design for Starship Super Heavy (formerly BFR). The interview reveals new details about the design, including micro-perforations on the outside of the windward side of the rocket that can bleed water or fuel for cooling:

Ryan D'Agostino: How does stainless steel compare [to carbon fiber]?

Elon Musk: The thing that's counterintuitive about the stainless steel is, it's obviously cheap, it's obviously fast—but it's not obviously the lightest. But it is actually the lightest. If you look at the properties of a high-quality stainless steel, the thing that isn't obvious is that at cryogenic temperatures, the strength is boosted by 50 percent.

Most steels, as you get to cryogenic temperatures, they become very brittle. You've seen the trick with liquid nitrogen on typical carbon steel: You spray liquid nitrogen, you can hit it with a hammer, it shatters like glass. That's true of most steels, but not of stainless steel that has a high chrome-nickel content. That actually increases in strength, and ductility is still very high. So you have, like, 12 to 18 percent ductility at, say, minus 330 degrees Fahrenheit. Very ductile, very tough. No fracture issues.

[...] [Here's] the other benefit of steel: It has a high melting point. Much higher than aluminum, and although carbon fiber doesn't melt, the resin gets destroyed at a certain temperature. So typically aluminum or carbon fiber, for a steady-state operating temperature, you're really limited to about 300 degrees Fahrenheit. It's not that high. You can take little brief excursions above that, maybe 350. Four hundred, you're really pushing it. It weakens. And there are some carbon fibers that can take 400 degrees Fahrenheit, but then you have strength knockdowns. But steel, you can do 1500, 1600 degrees Fahrenheit.

Arthur T Knackerbracket has found the following story:

On Thursday night, SpaceX founder Elon Musk shared photos of Raptor rocket engines that recently left the company's factory in Hawthorne, Calif., headed out to be tested at its facility near McGregor, Texas. "Preparing to fire the Starship Raptor engine," he said by way of a caption on Twitter.

The photos were interesting, but Musk had additional comments about the engine that revealed much about how the company is proceeding with overall design of the vehicle it will power. SpaceX's approach seems focused on keeping costs down and moving as quickly as possible towards a launch of the Starship spacecraft and Super Heavy rocket in the early 2020s.

For example, Musk said, "Initially making one 200 metric ton thrust engine common across ship & booster to reach the Moon as fast as possible. Next versions will split to vacuum-optimized (380+ sec Isp) & sea-level thrust optimized (~250 ton)."

This comment is notable for a couple of reasons. First of all, the company appears to have decided to streamline the Raptor engine to a single design that will power both the rocket at liftoff, and the spaceship in the upper atmosphere and outer space. It will take less time to develop, test, and qualify a single engine. It will also cost less money.

Additionally, Musk notes that the goal is "to reach the Moon as fast as possible." The company still appears to be focused on lunar orbital flights, such as the #dearMoon project for Japanese businessman Yusaku Maezawa, as the first missions for Starship.

There is an added benefit to this approach: for the next two decades, NASA appears likely to be highly interested in developing infrastructure near and on the Moon. By flying Starship on early test flights to the same destination, SpaceX has a far greater chance to win government contracts for the delivery of cargo, and potentially astronauts, to the Moon. Heretofore, neither NASA nor the US military has shown much if any interest in SpaceX's ambitious rocket and spacecraft.

-- submitted from IRC

Original Submission

realDonaldTrump submitted a story about SpaceX test firing its Raptor engine:

Elon Musk has been at SpaceX's test site for its rocket engines in central Texas this weekend. The facility near McGregor is where the company both tests Merlin engines for Falcon 9 flights, and also performs some experimental firings.

Due to a variety of reasons including financial pressures, SpaceX is pushing hard on the development of its next-generation Super Heavy rocket and Starship spacecraft. This was evidenced this weekend when, at 1:15am Central Time on Sunday morning, Musk shared a nighttime picture of himself on the test stand at McGregor, saying "with engineering team getting ready to fire new Raptor rocket engine." It was the dead of night on Super Bowl weekend, and they were working on an engine that won't go into space for a few years. But that didn't matter.

The test itself appears to have taken place later on Sunday. Eyewitness reports in Central Texas noted a large pop on Sunday evening, and more later Sunday night. Musk himself tweeted a photo shortly before 10pm local time, and thereafter a video. The test firing itself lasts for a few seconds, and was evidently successful. "First firing of Starship Raptor flight engine! So proud of great work by @SpaceX team!!" Musk wrote.

Also at Fox News.

Previously: In New Starship Details, Musk Reveals a More Practical Approach

Related: Elon Musk: Why I'm Building the Starship Out of Stainless Steel

Original Submission

martyb writes:

Elon Musk Shows off Fiery SpaceX Starship Heatshield Test:

[...] After successfully sending the first commercial crew capsule to the International Space Station in early March, Elon Musk's spaceflight company is on a hot streak and it's looking to continue that with an upcoming test launch of its much-discussed Starship.

But before Starship gets off the ground, Musk has given spacefaring fans a glimpse of the hexagonal heatshield tiles that will eventually protect the craft from searing heat.

Testing Starship heatshield hex tiles pic.twitter.com/PycE9VthxQ

— Elon Musk (@elonmusk) March 17, 2019

Musk explained that the hottest parts of the heatshield, glowing white in the short video above, reached a maximum temperature of around 1650 Kelvin (approx. 2,500 degrees Fahrenheit, approx. 1,375 degrees Celsius). He suggested this could withstand the extreme temperatures associated with returning to Earth, but it is slightly lower than the temperatures NASA's Space Shuttles were built to withstand (approx. 1,500 degrees Celsius).

Also at Teslarati.

Original Submission

takyon writes:

SpaceX targets 2021 commercial Starship launch

The first commercial mission for SpaceX's Starship and Super Heavy launch system will likely take place in 2021, a company executive said June 26.

Jonathan Hofeller, SpaceX's vice president of commercial sales, said the company is in talks with prospective customers for the first commercial launch of that system roughly two years from now. "We are in discussions with three different customers as we speak right now to be that first mission," Hofeller said at the APSAT conference here. "Those are all telecom companies."

[...] Hofeller said the discounted pricing SpaceX gave to early customers of Falcon 9 missions with pre-flown first-stage boosters is now the company's normal pricing. SpaceX Founder Elon Musk said last year that previously flown booster missions were priced "around $50 million," down from $62 million. Musk said SpaceX's prices would continue to decline, too. Hofeller reiterated that prices would keep dropping through the introduction of Super Heavy and Starship. The fully reusable nature of the launch system enables those lower prices, he said.

Being fully reusable also opens up new mission possibilities, he said. "You could potentially recapture a satellite and bring it down if you wanted to," Hofeller said. "It's very similar to the [space] shuttle bay in that regard. So we have this tool, and we are challenging the industry: what would you do with it?"

Starship.

Original Submission

martyb writes:

SpaceX's Starhopper Prototype to Make 1st Untethered Hop Soon, Musk Says:

The company has apparently fixed an issue with the vehicle's Raptor engine.

SpaceX is getting ready to let Starhopper off its leash.

Starhopper, a prototype for the company's future Mars-colonizing Starship vehicle, has conducted two brief test hops to date. Both occurred in early April at SpaceX's Boca Chica test site near Brownsville, Texas, and both employed a tether, which kept Starhopper very close to the ground (for safety's sake).

SpaceX had apparently been holding off on taking the next big testing step — removing the tether and letting Starhopper fly freely — until it could fix an issue with the vehicle's powerful, next-generation Raptor engine. But that problem seems to be solved, company founder and CEO Elon Musk announced via Twitter over the weekend.

Exciting progress in Boca! Hopper almost ready to hover. Based on tonight's test, looks like 600 Hz Raptor vibration problem is fixed. pic.twitter.com/9bLWOHG0sV July 7, 2019

Later that day, Musk sent out another tweet:

Will do Starship presentation a few weeks after Hopper hovers, so prob late July. If that timing works, free LJ chips for all present! July 7, 2019

Watching the progress of SpaceX and its rocket developments reminds me of the thrills of watching NASA's Mercury, Gemini, and Apollo development efforts. The 50th anniversary of the July 20, 1969 Apollo 11 landing on the moon is fast approaching. Were I on the SpaceX team, I know I would be doing everything I could to try and get the Hopper flying by then! Any bets?

Original Submission

DannyB writes:

SpaceX's Starhopper engulfed in fireball after critical Raptor static fire test

SpaceX's Starhopper was engulfed in a fireball shortly after a static fire ignition of its Raptor engine, almost certainly delaying the low-fidelity Starship prototype and testbed's first untethered flight.

With any luck, Raptor, Starhopper, and SpaceX's spartan Boca Chica facilities have escaped relatively unharmed. Regardless, even if Raptor's static fire was technically successful, some repairs will likely be necessary and the off-nominal behavior that occurred after the ignition test will have to be dealt with and understood to prevent such behavior during future Starhopper operations.

[...] Due to the inherently low quality of video captured through thousands of feet of thick, humid Texas air, it's almost impossible to make specific details out. However, shortly after the static fire ignition and shutdown, some viewers believe that there was fire visible at one or several points on Starhopper, although what looks like fire could easily be a simple reflection of the active flare stack just a few hundred feet away.

Hopefully hurt nobody is, damages minimal they are, and lots of telemetry collected it was.

Original Submission

takyon writes:

NASA has announced 19 non-reimbursable Space Act Agreements (SAAs) with 13 U.S. companies, including SpaceX, Blue Origin, Lockheed Martin, Sierra Nevada Corporation, Aerogel Technologies of Boston, and others. No money will be exchanged, but NASA employees will offer their knowledge and expertise for a variety of projects.

SpaceX's SAAs concern landing Starship on the Moon and refueling Starship in-orbit:

SpaceX of Hawthorne, California, will work with NASA's Kennedy Space Center in Florida to advance their technology to vertically land large rockets on the Moon. This includes advancing models to assess engine plume interaction with lunar regolith.

[...] SpaceX will work with Glenn and Marshall to advance technology needed to transfer propellant in orbit, an important step in the development of the company's Starship space vehicle.

Following its 20-meter hop test, SpaceX's Starhopper is scheduled to conduct a 200-meter hop no earlier than August 12, with backup dates on the 13th and 14th.

Blue Origin will work on a navigation system and technologies for the company's planned lunar lander:

Blue Origin of Kent, Washington, will collaborate with NASA's Johnson Space Center in Houston and Goddard to mature a navigation and guidance system for safe and precise landing at a range of locations on the Moon.

[...] Blue Origin will partner with Glenn and Johnson to mature a fuel cell power system for the company's Blue Moon lander. The system could provide uninterrupted power during the lunar night, which lasts for about two weeks in most locations.

[...] Blue Origin, Marshall and Langley will evaluate and mature high-temperature materials for liquid rocket engine nozzles that could be used on lunar landers.

Other technologies being collaborated on include a CubeSat radio transponder for the Space Network, flexible aerogels for rocket soundproofing, and Hall-effect thrusters with extended operating range.

Original Submission

takyon writes:

SpaceX's Starhopper has successfully completed a 150-meter test hop. Due to two orbital prototypes of Starship already nearing completion, Starhopper will not fly again, and will instead be converted into a vertical test stand for Raptor engine static fire tests:

SpaceX's Starhopper test vehicle – after finally gaining the required Federal Aviation Administration (FAA) permit for its highest hop yet – successfully carried out its test on Tuesday. The approval was required to pave the way for the 150 meter jump out of Boca Chica, Texas. Monday's attempt was scrubbed at T-0 due to an issue relating to the ignitor system on the SN6 Raptor, moving the next attempt to Tuesday which was successful.

[...] Currently, SpaceX has two full-scale prototypes nearing completion which are designated Starship Mk 1 and Starship Mk 2 respectively. The Mk 1 prototype is being built at the Boca Chica launch site while Mk 2 is being constructed in Cocoa, Florida.

Construction of both prototypes is progressing well, with the primary structures of the two vehicles nearing completion.

According to SpaceX CEO Elon Musk, the two major sections of the vehicles (fairing and tanks) will soon be stacked together. From there, technicians will install the control fins, Raptor engines, and landing gear.

A presentation revealing new details about Starship has been tentatively rescheduled for mid-September.

Also at Ars Technica and Teslarati.

A video of the flight is available on YouTube.

Previously: SpaceX Launches CRS-18 Using Twice-Flown Booster, Starhopper Finally Flies
SpaceX 'Starhopper' Highest-Ever Test Flight Early Next Week
SpaceX's Starhopper 150-Meter Test... Scrubbed for Monday; Try Again Tuesday at Same Time [Updated]

Original Submission