Spaceflight Insider

Elon Musk answers questions about SpaceX’s Mars plans in surprise Reddit AMA

ITS Observatory

Image Credit: SpaceX

In stark contrast to questions SpaceX founder and CEO Elon Musk encountered following his Mars architecture announcement at the 2016 International Astronautical Congress (IAC) earlier this year, the NewSpace entrepreneur entertained questions from a more informed group in a surprise Reddit AMA (Ask Me Anything) on Oct. 23, 2016.

The AMA took place in the website’s r/spacex forum and shed some light on SpaceX’s future plans. Participants were asked to refrain from asking questions about Tesla or Solar City. If fact, Musk spent little time discussing much beyond the company’s Mars-centric hardware. He did, however, talk about the company’s upcoming upgrade for the Falcon 9 rocket.

Falcon 9

SpaceX Falcon 9 FT first stage at Port Canaveral in Florida Photo Credit: Michael Howard / SpaceFlight Insider

Photo Credit: Michael Howard / SpaceFlight Insider

In response to redditor FoxhoundBat, Musk said the Falcon 9 was undergoing a redesign meant to improve performance and reusability:

Final Falcon 9 has a lot of minor refinements that collectively are important, but uprated thrust and improved legs are the most significant.

Actually, I think the F9 boosters could be used almost indefinitely, so long as there is scheduled maintenance and careful inspections. Falcon 9 Block 5 – the final version in the series – is the one that has the most performance and is designed for easy reuse, so it just makes sense to focus on that long term and retire the earlier versions. Block 5 starts production in about 3 months and initial flight is in 6 to 8 months, so there isn’t much point in ground testing Block 3 or 4 much beyond a few reflights.

With the change to the Falcon 9 allowing for practically indefinite reuses, the company has the potential to focus more than 5 percent of its resources toward getting its Mars plans off the ground.

Interestingly, Musk noted the upcoming iteration of the company’s workhorse launcher will be the Block 5. This marks a change to the company’s tradition of christening the successive modifications to the rocket with a version number.

However, if one were to ascribe a “block number” to the preceding iterations of the Falcon 9, it’s not readily apparent how the latest design is the “Block 5”. There seems to be a generation missing in this naming scheme, although Musk did not elaborate. That did not discourage some redditors from attempting to work it out.

It was also not discussed what impact, if any, this change to the Falcon 9 may have on the vehicle’s certification to launch payloads for the United States Air Force.

Interplanetary Transportation System

The greatest interest from the AMA participants was definitely centered on SpaceX’s Mars architecture. Musk spent time answering a wide range of questions about the topic. Notably, he is not a fan of the ITS moniker:

I think we need a new name. ITS just isn’t working. I’m using BFR and BFS for the rocket and spaceship, which is fine internally, but…

While the SpaceX CEO may not like the ITS name so much, he has already settled on a name for the first ship of the line that will visit the Red Planet: Heart of Gold. A nod to the vessel of the same name from The Hitchhiker’s Guide to the Galaxy, SpaceX’s ship will precede any crewed mission and will be laden with equipment meant for constructing a propellant manufacturing plant.

Before any ITS-class ship ever makes a journey to Mars, the company plans to send several Dragon-class missions to gather as much entry, descent, and landing data as possible to mitigate the chances of adding to the collection of craters on Mars’ surface, as well as to better understand the best process for extracting water for making the propellant.

ITS Raptor engines

The ITS engine cluster. Click to enlarge. Image Credit: SpaceX


Ever the science fiction fan, Musk seems to take pleasure any time he can integrate something from the genre into SpaceX’s operations. ITS is no different. When asked about the number of engines in the ITS’s first stage, Musk had a quick and very Musk-esque answer:

“It had to be 42 for important scientific and fictional reasons! The dense packing is just to max out thrust to weight, but it would be cool if there was a virtual nozzle side effect.”

The number “42” plays a notable role in The Hitchhiker’s Guide to the Galaxy as the “Answer to the Ultimate Question of Life, The Universe, and Everything”.

However, not all of Elon’s interactions were steeped in science fiction lore. Redditor TheVehicleDestroyer wanted to know some specifics on the performance of the sea-level Raptor engine when used in vacuum. Musk said the Raptors meant for atmospheric operation would still have quite a bit of power, pushing 290 metric tons of thrust and operating with a specific impulse of approximately 360 seconds.

Living on Mars

Although there is a preponderance of evidence that Mars may have been habitable in the past, it certainly is not welcoming to humans at present. Redditor Ulysius questioned Musk on plans for permanent human habitation on the Red Planet, to which the SpaceX founder replied:

Initially, glass panes with carbon fiber frames to build geodesic domes on the surface, plus a lot of miner/tunneling droids. With the latter, you can build out a huge amount of pressurized space for industrial operations and leave the glass domes for green living space.


ITS spaceship development tank

Photo Credit: SpaceX

One of the key announcements in Musk’s address at the IAC conference was the revealing of a large composite fuel tank. Long the goal of many in the spaceflight industry with their mass savings translating into greater payload capabilities, composite propellant tanks have proven problematic at best, and catastrophic at worst.

Elon, however, feels SpaceX has a good handle on the manufacture of large composite tanks. Responding to redditor nalyd8991, Musk fairly gushed over the composite structure:

Yeah, for those that know their stuff, that was really the big news 🙂

The flight tank will actually be slightly longer than the development tank shown, but the same diameter. That was built with latest and greatest carbon fiber prepreg. In theory, it should hold cryogenic propellant without leaking and without a sealing linker. Early tests are promising. Will take it up to 2/3 of burst pressure on an ocean barge in the coming weeks.

Testing the tank at sea, away from personnel and structures, will help to ensure the maximum level of safety should a failure occur.

SpaceX, however, has some challenges relating to not only the propellant tanks but also to the alloys used in the Raptor’s turbopumps.

Operating at pressures much higher than any other engine, the turbopumps will be subjected to oxygen-rich conditions which may lead to erosion in the pump, though early test firings didn’t indicate that would be a likely problem.

However, according to Musk, “…there is still room for optimization.”



Curt Godwin has been a fan of space exploration for as long as he can remember, keeping his eyes to the skies from an early age. Initially majoring in Nuclear Engineering, Curt later decided that computers would be a more interesting - and safer - career field. He's worked in education technology for more than 20 years, and has been published in industry and peer journals, and is a respected authority on wireless network engineering. Throughout this period of his life, he maintained his love for all things space and has written about his experiences at a variety of NASA events, both on his personal blog and as a freelance media representative.

Reader Comments

For oxygen tank and other parts be used stack, spraying with the addition of nanoparticles.

Wow. I had no idea that SpaceX was this far along cutting metal and claving carbon for real BFR-BFS hardware.

That tank is impressive. Containing liquid methane at 5000 psi and -360°F with an adequate safety margin is momentous It looks like carbon fabrication tech has advanced a lot in the last decade.

It brings an unrelated question to mind: Lockheed-Martin’s X-33 Venture Star reusable SSTO program was cancelled for a couple of big sticking points. The linear aerospike rcocket engine, and the composite liquid hydrogen oxygen propellant tanks. The X-33 was cancelled in 2001, fifteen years ago.

It sounds like X-33 Venture Star might be doable today

X-33 was do-able a couple of years after it was cancelled.

Now we have a vehicle which by itself has nearly the thrust of a Saturn V, and with both sea level and vacuum engines in one cluster. Sheesh…

I’m wondering if the new Block 5 Falcon will be modified to use the Raptor engines, and utilize liquefied methane (densified, of course) and LOX as the fuel /oxidizer couple. I’m also wondering if they might not have an intermediate vehicle as a “proof of concept” demonstrator between Falcon Block 5 and the BFR? Engineering wise, it seems to be an awfully big single step to go right for the BFR? Get some flight time with a smaller composite tank system and Raptor engines could still fly a big payload to Mars.

I love SpaceX. They are doing wonderful work without using a lot of taxpayer money. I watch every launch they do. They are putting people to work, and inspiring young people to study math and science needed to make life easier and longer.
They have accomplished an amazing amount – on Earth. Earth has a nice atmosphere which means you can work in large factories without expensive space suits, or the factories needing to be pressurized. Earth has abundant energy available in the form of electricity and natural gas for heating things. The supply of both is essentially unconstrained. Earth has abundant metals, plastics, glass, wires, chemicals, food, water, computers, machine tools, people with very specialized skills, hospitals, and millions of other items usually available in a few weeks, at most.
Unfortunately, Mars has none of those things. Even staying alive on Mars will be a complex, and extremely expensive undertaking. Having nearly no atmosphere, no fossil fuels, no organics in the poor soil, and no free surface water will be problems that would cost trillions of dollars to overcome. The amount of supplies that will need to be transported from Earth until a self sustaining colony could exist, will be enormous. The 2 year transit time, and relatively small amount of capacity which could be brought by any rocket, will prevent the establishment of a self-sustaining colony on Mars. The list of things that could go wrong to prevent success is virtually endless.
If Mars was more like Earth, with a breathable atmosphere and liquid water, colonization might eventually work. But in a near vacuum, it will never happen. That is why nobody is calling your smart phone from the Moon, a short 3 days away.
A few scientists may live on Mars for some limited amount of time. Scientists live in Antarctica, but access is a piece of cake, compared to getting to Mars. No C-130 will deliver you a new generator, diesel fuel, or food on Mars. And I doubt many people have spent more than a few years in Antarctica. Supporting them is very expensive. And they are nearly all highly motivated scientists doing scientific research. Those who are running the base are probably paid very well, with a plan to return home with a lot of cash. That won’t happen with Mars.

It’s perfectly feasible to set up a settlement in Mars like conditions. My personal favorite is a City inside Olympus Mons. There you would probably find lots of useful metals, water ice and other materials, as wella as caves and lava tubes that could make easily pressured spaces. Also you could make a launch site on the summit, as it’s almost in space already at 20K+. Inside Moms you would not have to worry about radiation or dust storms and it’s so large that it could hold a massive settlement.

Your assumptions are erroneous, and you need to read either Robert Zubrin’s “The Case for Mars,” or “Entering Space.” The atmosphere is a phenomenal source of raw material for an industrial society on the Red Planet. Almost every element needed for a manufacturing facility can be found in situ.

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