Spaceflight Insider

SpaceX sends Raptor to Texas for testing

SpaceX's Raptor rocket engine undergoes a static test fire in this NASA image. Photo Credit: NASA / Stennis

SpaceX’s tests one of the Raptor rocket engine preburners at NASA’s Stennis Space Center in 2015. This month, the first full Raptor was shipped to McGregor, Texas, for firing. Photo Credit: NASA

In a keynote address at a Utah conference about small satellites, SpaceX president Gwynne Shotwell talked about how the company is working to fly CubeSats and other small spacecraft as a side payload on upcoming vehicles, including the Falcon Heavy and Red Dragon. She also mentioned the company has shipped the first Raptor engine to their McGregor, Texas, test facility for firing.

The speech was at the 30th annual Conference on Small Satellites at Utah State University in Logan, Utah. Shotwell talked about how the company, which first developed the Falcon 1 for small satellites before retiring it due to not being able to “make Falcon 1 work as a business”, is working with other companies to send items, such as CubeSats, as secondary payloads atop their much larger Falcon 9 and future Falcon Heavy.

Additionally, according to Space News, there was a lot of interest by attendees on SpaceX’s Mars plans. Shotwell said the company is working on making space available to send small satellites in not only the trunk of Red Dragon but also inside the capsule itself. The Spacecraft is expected to land on the Red Planet as early as 2018.

The Raptor Engine

SpaceX rocket 2010 lineup

In 2010, SpaceX showcased a lineup of its current and future rockets with the Saturn V. While the company’s plans have changed in the last six years, this is the closest official rendering the NewSpace firm has released regarding their future massive rocket. Image Credit: SpaceX

Red Dragon is part of SpaceX’s plans to begin developing a Mars architecture to begin sending payloads and eventually people to the surface of the Red Planet. Elon Musk, the CEO and founder of the company, is expected to make those plans public at the September International Astronomical Congress in Mexico City.

Said plans are expected to include the Mars Colonial Transporter (MCT), a vehicle that is projected to be larger than the Saturn V. There have been concepts of potential concepts for an MCT floating around the Internet, but so far, no firm plans have been made public.

One thing that is certain for the MCT, however, is the need for a new engine. This is where the Raptor comes in. It will be powered by methane and liquid oxygen in the MCT tanks.

“We just shipped the first Raptor engine to Texas last night,” Space News reported Shotwell as saying at the conference. “We should be firing it soon.”

While this is the first full Raptor engine that SpaceX will fire, the company has already tested individual pieces at various places. In 2014, the company began development and testing of the injectors and completed a full-power test of a full-scale oxygen preburner in 2015.

Some 76 hot-fire tests of the preburner were conducted at NASA’s Stennis Space Center from April to August 2015, totaling around 400 seconds of test time.

Additionally, in January 2016, the U.S. Air Force awarded SpaceX $33.6 million development contract for the company to develop a prototype upper stage version of its future Raptor for use on the Falcon 9 or Falcon Heavy rockets.

The NewSpace firm was required to double-match the amount for a total of about $67.3 million. Testing of this upper stage is expected to be done at Stennis and be completed by 2018.

The specifications of the Raptor is still unclear. According to Wait But Why in 2015, Musk said engineers were targeting around 510,000 pounds (2,300 kilonewtons) of thrust with a fuel ratio of approximately 3.8 to 1. This would give the engine about three times the thrust of the current Merlin 1Ds – which are used on the Falcon rockets – and be about one-third the thrust of the Saturn V’s F-1 engine. According to Ars Technica, it is believed that a cluster of nine of these engines would power the MCT.

Raptors are expected to use a “staged combustion cycle” as opposed to the “open cycle” gas-generator system that the Merlin engines use. On an open cycle, the gas used to power the turbopumps is exhausted without passing through the main combustion chamber. It can be thought of as like a muffler on a car.

An RS-25 being tested at NASA's John C. Stennis Space Center. Photo Credit: NASA / Aerojet Rocketdyne

An RS-25 is tested at NASA’s Stennis Space Center. This engine, which also helped propel Space Shuttles to orbit, utilized a staged combustion cycle process. Photo Credit: NASA / Aerojet Rocketdyne

For staged combustion, instead of being channeled out separately, all of the gasses and heat go through the combustion chamber. This makes the engine more efficient, but it also makes for harsher turbine conditions and is usually more complicated.

For comparison, the Space Shuttle Main Engines, which are the same RS-25 engines that are going to be used for the Space Launch System, are staged combustion.

However, what makes Raptor unique is, according to NASASpaceflight in 2014, it will be the first “full-flow staged combustion cycle” designed to use methane and liquid oxygen. This means 100 percent of the oxidizer, with a low-fuel ratio, and 100 percent of the fuel, with a low-oxygen ration, will power the oxygen pump and methane pump, respectively. This is expected to allow the turbine to run cooler and at lower pressures resulting in a longer engine life.

Prior to this, only two full-flow staged combustion engines had progressed to the test stands: the Soviet RD-270 in the 1960s and the integrated powerhead demonstration project in the mid-2000s. The latter was a U.S. government-funded Aerojet Rocketdyne project. Neither progressed to actual flight worthiness.

Ongoing Work

F9-0024 test

SpaceX continues to conduct full-duration firings of the F9-0024 core, which helped loft the JCSAT-14 spacecraft to geostationary transfer orbit. The company has fired it at least twice and hopes to conduct up to six more tests of the booster. Photo Credit: SpaceX

Raptor and MCT will continue the work that SpaceX engineers are doing regarding innovation. This includes the ability to cool the fuel and oxygen inside the rocket’s tanks close to their freezing points to allow for more propellant to fit inside tanks; 3-D printing many of the critical parts of the engine; and retropropulsion technology in order to land on Earth as well as Mars without parachutes, just to name a few.

Since 2012, the NewSpace company has been hard at work in developing a rocket that has “full and rapid reusability”. In late 2015 and throughout 2016, the company has seen the fruits of their efforts begin to pay off with the first stage of the Falcon 9 being recovered on multiple missions – both at sea and on land. At least one, possibly two, of these boosters are expected to refly later this year, according to Space News.

Additionally, Musk announced at Code Conference 2016 that SpaceX hopes to send people to Mars as early as 2024 with a landing in 2025 if everything goes according to plan.

Starting with the 2018 Red Dragon mission, the company hopes to send at least one spacecraft to Mars on every launch opportunity, which occurs once every 26 months.

“We’re establishing cargo flights to Mars that people can count on for cargo,” Musk said at the June conference.

The company hopes to launch the first uncrewed MCT to test in deep space as early as 2022.

In the meantime, the company is continuing to refine their process for reusing the Falcon 9. Last month, the booster recovered in the May 2016 JCSAT-14 mission was taken to McGregor. There a full duration test-fire was conducted not once but twice in two days. That booster has been deemed by Musk as the “life-leader” as the booster experienced the most stress that could be expected on a successfully recovered stage. This particular stage is not expected to refly.

The first stage that is expected to refly is the booster that was recovered in April 2016 during the CRS-8 mission.

“We’re going to run as many tests on [the JCSAT-14] stage as we can pull off,” Shotwell said. “Hopefully, we’ll get more than four, and maybe eight to ten of these before we go ahead and refly.”

Video courtesy of SpaceX


Derek Richardson has a degree in mass media, with an emphasis in contemporary journalism, from Washburn University in Topeka, Kansas. While at Washburn, he was the managing editor of the student run newspaper, the Washburn Review. He also has a blog about the International Space Station, called Orbital Velocity. He met with members of the SpaceFlight Insider team during the flight of a United Launch Alliance Atlas V 551 rocket with the MUOS-4 satellite. Richardson joined our team shortly thereafter. His passion for space ignited when he watched Space Shuttle Discovery launch into space Oct. 29, 1998. Today, this fervor has accelerated toward orbit and shows no signs of slowing down. After dabbling in math and engineering courses in college, he soon realized his true calling was communicating to others about space. Since joining SpaceFlight Insider in 2015, Richardson has worked to increase the quality of our content, eventually becoming our managing editor.

Reader Comments

I was wondering. Does the term “BFR” include the MCT? As I understand it. The BFR will be using 9 Raptor engines in a first stage but the MCT (the second stage) will have a nuclear powered propulsion system perhaps in addition to Raptors.

From the same conf:

Has SpaceX considered other propellants, like hybrids or nuclear?

For booster propulsion, it’s definitely liquid propulsion. Are looking somewhat at electric propulsions for use in space.

For nuclear, there’s a lot of work to do, but it holds promise.

MCT (Mars Colonial Transporter) consists of BFR (Big F*** Rocket) and BFS (Big F*** Spaceship). From speculation by various people as well as a few of Musk’s comments from reddit AMAs:

– BFR will likely have ~30 ish engines, optimised for a surprisingly low thrust level (the 9 engine stuff is out of date) and be 13m-15m in diameter. Its job is to boost up the BFS and return to launch site.
– BFS may look like a larger version of Crew Dragon, but ~15m-20m in diameter with Raptor engines instead of Super Dracos. It will use its propellant to achieve Earth orbit.
– It will then be refueled using a tanker version of BFS (3 refueling flights per Mars mission) and burn for Mars.
– At Mars, it will enter the atmosphere and use a lofting trajectory to slow down as much as possible and then use super sonic retro propulsion to land.
– Then it will be refueled using ISRU and fly directly back to Earth where it will reenter and land at the launch site.

That would be simply the most epic thing to be seen in a lifetime.

Other sources/speculations say BFR first stage will use 25-30 Raptors.

Yea the 9 engine BFR is bogus. 9 x 500k thrust is basically no better than FH. 25-30 seems like more likely to provide the thrust needed to be significantly higher than Saturn V.

There’s also the fact that even a single Raptor, throttled down to, say, the same 70% setting that is the minimum for the Merlin 1-D, will still crank out 350,000 lbs. of thrust. Unless the BFR’s empty mass is at least this great, it will have to “hover-slam” to land like the F9 and, soon to be, FH cores do. I suspect SpaceX would rather this much more expensive asset be able to actually do a true hover for at least a few seconds and settle down more gently so as to minimize the possibility of damage on landing. A 15- or 20-meter dia. stage with 30-plus engines might be heavy enough to “float like a butterfly” just before touchdown.

I don’t know what the thrust-to-weight ratio of the Raptor will be. It uses a staged combustion cycle which is different than the gas generator combustion cycle of the Merlin 1-D, which has a sea-level T-W ratio of 180. Among other existing staged combustion engines, the best T-W ratio is that of the Russian RD-191 at 90 – half that of the Merlin 1-D. Assuming the Raptor can match its Russian counterpart, a Raptor making 2.7 times the thrust of a Merlin 1-D should weigh 5,500 lbs. 30 Raptors would weigh 165,000 lbs. The BFR stage will need a heavy thrust structure to mate these engines to their tankage and supporting structure. At least the outer engines will have gimbaling systems and the propellant delivery plumbing will be formidably complex and fairly hefty as well. Then there will be landing legs – at least four and quite possibly more. Each of these may weigh up to a ton or more. It’s easy to foresee a dry mass for the whole BFR stage of at least the 350,000 lbs. that would seem to be required to enable true hover on landing. As much as two-thirds of this mass might reside in the bottom 25 or 30 feet of the stage. This, combined with a profile more squat than that of the Falcon cores should make the BFR stage extremely stable on its landing legs.

is there video of the keynote by Gwen?

I have wondered if while SpaceX is talking about sending people to Mars, if the company has invested in any research regarding the deep space radiation issues to protect the crews, and the gravity problems? Does anyone know?

From the same conf:
Q: What considerations are being given to the radiation environment for manned interplanetary flight?
A: Yes, we’re looking at it, but we’re not focused on it right now because we understand that others are.

NASA has been studying this, in particular.

With the Raptor reportedly having around 510,000 lbf of thrust and the Blue Origin BE-4 being designed to produce 550,000 lbf of thrust with both using liquid methane as a propellant and made for reusability they sound pretty interchangeable.

ULA is planning to use the BE-4 for their Vulcans. The SpaceX Raptor powered Falcon sounds like a mirror image. It should be interesting to see how the companies differentiate themselves. If it is solely by price I think SpaceX will win any competition.

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