Tom Mueller

[Grendal]

The man behind the scenes at SpaceX (SpaceX's J. B. Straubel) is Tom Mueller. He is rarely seen and runs the MacGregor facility. Here is a very recent interview of him. It is filled with lots of detailed information:

Twitch

 

[HVM]

Reddit transcript: reddit.com...tom_mueller_interview...

Arstechnica article: arstechnica.com...a-top-spacex-employee

NSF (Daniels30):

• Block V landing legs will be able to retract them selves and have better ablative protection across the bottom of the rocket. - Presumably removing all smouldering that occurs after landing.
• Satellite constellation will double current global bandwidth, better in more remote locations due to lack of users.
• Hitting limits of chemical propulsion with Raptor.
• Raptor is designed for 99% chemical efficiency.
• SpaceX looking at nuclear propulsion for mars surface power with NASA, this will be used for propellent production however as stated by Musk solar will be first. Nuclear propulsion also but testing bans, performance limitations and ultimately money stopping it.
• Electric propulsion will be used for satellite constellation. (As i thought due to hiring patterns in Seattle, lots of ex NASA JPL folks)
• Musk can be extremely demanding to work for.
• Musk is known for going a totally different direction despite engineers wanting to go down the other route, has had horrible results but has also worked well.
• Merlin 1D uses a method called “[face] shut off”, removes most valves reducing chances of failure by removing components and removing a lot of risk of a hard start. - Musk convinced Mueller of using this method despite Mueller explaining what it is and how it increases complexity of R&D and increased costs due to blowing lots of hardware up before mastering the method.
• Mars Rocket (BFR) will render all other LV’ inert.
• Roughly 1000tons of propellent needed to get home(Earth) from Mars according to Mueller. Manufactured over a two year cycle.
• Musk wanted a 12 hour turnaround for Block V but was stopped after being told it was too tricky currently, settled for 24 hour turnaround after landing.
• Raptor runs 3.5, 3.6 O/F ratio.

 

[NikeWings]

My son graduates from MIT next month and accepted a job with the SpaceX rocket propulsion team. While he admires Elon tremendously, he accepted the offer for one reason only - Mueller!! He's been a motivating driver of both my kids (another graduating next year) passionate interest in space travel. I hope to travel off our planet some day, if not, they already know what to do with my ashes. Jaw dropping amazing times.....wish I was young enough to start over.

 

[ecarfan]

Merlin 1D uses a method called “[face] shut off”,

Should be "phase", not "face", I believe.

I listened to that call with Mueller. Nice guy. Hope he didn't reveal too much. Some of the things he said have not been publicly stated before.

 

[HVM]

Should be "phase", not "face", I believe.

I listened to that call with Mueller. Nice guy. Hope he didn't reveal too much. Some of the things he said have not been publicly stated before.

"Furthermore, with proper design the sleeve can be made to fully shutoff both propellants at the injector face (hence, “face shutoff”), thereby eliminating all dribble volume from the injector."

http://www.rocket-propulsion.info/resources/articles/TRW_PINTLE_ENGINE.pdf

 

[AudubonB]

Thanks for the clarification. When I first read ".....sleeve....propellants...face shutoff.....dribble...." I was envisioning the nominal interaction between my shirt cuffs and my nostril tips.

 

[Grendal]

The story about Elon comparing a Model S to the Merlin engine is fantastic. It absolutely clarifies why Elon is such a great CEO/CTO.

Even airliners are kind of expensive for our cost trades. From Elon, I’d always get, you know, how much does it cost to make a Model S, a Tesla? Start from there, and work my way up to the rocket.

Like, here’s a conversation I had maybe about five years ago on the Merlin 1D when we first developed it. He asked me; he said, “How much do you think it costs to make a Model S?" And I’m like “I don’t know; 50 thousand dollars?” He said “No, about 30 thousand dollars.” That’s the marginal cost for that car.

And he said, “How much does that car weigh?” And I said, “About 5 thousand pounds.” And how much does a Merlin engine weigh? I go, “About a thousand pounds?” So, he’s like, “So why the heck does it cost, you know, some fraction of a million dollars to make a Merlin engine?”

And I mean, he has a good point. And the material you’re using isn’t aluminum, it’s not stamped, so I’ll give you a factor of five. So it’s equivalent to a five-thousand-pound rocket engine. So why’s it 20 times the cost? So that’s the way we look at it and the way we think at SpaceX trying to get the amortization cost of the rocket down. Once you start reusing it, the real big cost becomes the amortization cost of the rocket, the operational costs, and the fuel costs, which is basically the same model as the airliners.

Should be "phase", not "face", I believe.

I listened to that call with Mueller. Nice guy. Hope he didn't reveal too much. Some of the things he said have not been publicly stated before.

I also thought it was "phase." It seems we were both wrong about that...

There were some unknown juicy details but I doubt he could into too much trouble. It's really nothing that Elon hasn't done before too.

 

[ecarfan]

"Furthermore, with proper design the sleeve can be made to fully shutoff both propellants at the injector face (hence, “face shutoff”), thereby eliminating all dribble volume from the injector."

http://www.rocket-propulsion.info/resources/articles/TRW_PINTLE_ENGINE.pdf

thanks for the correction! The audio quality on that skype call was poor and I was sure I heard "phase". My apologies.

 

[ecarfan]

The story about Elon comparing a Model S to the Merlin engine is fantastic. It absolutely clarifies why Elon is such a great CEO/CTO.

That was a good analogy, though if one were to set up a manufacturing facility to make 100,000 Merlin engines a year (assuming there were buyers for that kind of volume) than it probably would be a lot easier to get the cost down. But when one is building far less than 200 Merlin engines a year (currently) it's a lot harder to reduce costs.

 

[HVM]

Model S ~400 kW
Merlin ~3,000,000 kW* ~= 2.5 time traveling DeLoreans

*(like all heat engines only 1/3 goes to move the exhaust gas, also using power as measure in rocket engines is meaningless, but fun)
;P

@AudubonB
Amazon.com: Gentleman's Checkered Casual Hankie Soft, Brushed Cotton Handkerchiefs Medium Size 12x12 inch size, Set of Four: Handmade

 

[jkn]

Model S ~400 kW
Merlin ~3,000,000 kW* ~= 2.5 time traveling DeLoreans

*(like all heat engines only 1/3 goes to move the exhaust gas, also using power as measure in rocket engines is meaningless, but fun)
;P

@AudubonB
Amazon.com: Gentleman's Checkered Casual Hankie Soft, Brushed Cotton Handkerchiefs Medium Size 12x12 inch size, Set of Four: Handmade

Reddit transcript: reddit.com...tom_mueller_interview...
...

• Raptor runs 3.5, 3.6 O/F ratio.

Methane gives 55.50 MJ/kg. 4 kg O2 is needed to burn 1 kg CH4. So we get 11.1 MJ/kg with O2. E= mv²/2 -> Speed of exhaust, if all energy is converted to speed v = 4.711 km/s.

3.5 kg O2 + 1 kg methane -> 3.5/4=0.875 kg burned CH4 + 0.125 kg unburned

0.875 kg CH4 gives 48.5625 MJ and with 3.5 kg O2 we get 10.792 MJ/kg.

v = sqrt(10.792 MJ * 2) = 4.646 km/s

Raptor vacuum ISP: 382 s = 3.747 km/s = 7.020 MJ/kg

7.020 / 10.79 = 0.65

So 65% of energy is used for speed of exhaust (relative to rocket)! Unfortunately much less is used for speed of rocked.

When CH4 is burned with limited O2 it produces CO2, CO, H2O, H2 and CH4. I don't know how this changes energy produced, so 65% is not very accurate.

H2 + O2 engines are used with 5:1 - 6:1 MR. 8:1 would burn all H2. That's done because H2 in exhaust gives better ISP than H2O, even though there is less energy. I guess same applies to CH4 engine.

 

[Nikxice]

Quote from Tom Mueller. "And then we built the Falcon 1, which had a single Merlin engine on it, could throw about 1k lbs into LEO; and they said, you guys, you guys were able to build a small rocket. But you’ll never be able to build an EELV-class, EELV-mission class rocket. And so we built the Falcon 9 and started flying it. And they said you’d never be able to reuse it; you’ll never be able to get to the space station. And at some point, you stop listening to it. And I think it’s great, you know, if people think what you’re doing is impossible then you must be doing the right thing. You can still find the YouTube video online where people are critiquing our recovery thing as being photoshopped or CGI’d. That’s pretty high praise, when people don’t actually believe you’re doing."

I'll admit to having initial doubts concerning SpaceX's ambitions and their chances of success. I remember about 10 years ago a NASA historian friend and I joked that some of their plans seemed crazy. How the hell were they going to make 9 Merlin engines burn together simultaneously with any reliability? Visions of former Soviet N1 rocket catastrophes rained down that day. I soon woke up after their first successful orbital flight. Which fortunately led me full throttle into Tesla. I quickly realized that if Elon created a SpaceX team that could do something really difficult, developing a successful terrestrial EV would be challenge, but realistically doable. Thank you Tom Mueller!

 

[ecarfan]

Yep, I loved that statement from Mueller about how they kept being told what they were doing was impossible but they kept working anyway and disproved the skeptics over and over again.

That isn't to say that everything SpaceX attempts in the future will be successful. Of course there will be failures. But they keep trying and eventually they get it right. Exactly the same story with Tesla: Elon sets crazy goals with crazy timelines. Tesla meets the goals, invariably past the announced timeline, but they still achieve their goals.

That's how you do super hard stuff.

 

[TLej]

That was a great interview, I read the transcript on the weekend. I liked the part about making cars at the same speed as a bottling plant bottling beverages. Some exaggeration there I'm sure, but who knows ultimately how much? You'd need some pretty quick-curing paint to have the paint shop running that fast...

 

[ecarfan]

The reference to future Tesla factory car production speed was for the production line where vehicle assembly is performed. Clearly it takes a significant amount of time to prime and then paint a car even with the latest robots.

But we are getting off topic from SpaceX...

 

[ORB]

Reading about Tom reminded me of George Mueller (no relation, I believe), the NASA manager during the '60s who promoted the "all-up" testing model to accelerate the Apollo development schedule. Both strong-willed guys who faced opposition to their ideas but succeeded.

 

[Grendal]

SpaceX’s Tom Mueller to Address 2017 Mars Society Convention

details at:

The Mars Society

The 20th Annual International Mars Society Convention
University of California, Irvine

September 7th - 10th, 2017

 

[ecarfan]

Thanks @Grendal that should be an interesting presentation! I'm counting on the guy who runs the Facebook SpaceX group, Bill Carton, to attend and post about anything new and exciting that Mueller talks about.

 

[Grendal]

Tom Mueller will be speaking at the ISDC 2018, May 24-27, in L.A.

http://isdc2018.nss.org/
ISDC 2018 (@ISDC) | Twitter

 

[Grendal]

Article on Tom's accepting his award. Some tidbits on SpaceX and Raptor:
SpaceX propulsion guru Tom Mueller looks ahead to Raptor rocket engines for Mars