SpaceX announces Interplanetary Transport System

Miscellaneous and Personal Stuff I Must Share
21

One thing I noticed, or rather didn’t notice, is that there doesn’t seem to be a scape system on the spaceship (as an aside, pretty awesome to start talking about spaceships and not orbiters).
I wouldn’t be surprised if the passengers would be sent up on a separate capsule style orbiter.

One thing did make me roll my eyes though. At the very end of the presentation Mars turns green and seas rise up. Unless they plan to install a humongous magnet on Mars core terraforming it is a fools errand because of the lack of a magnetic field allowing high amounts of radiation on the surface.

22

That didn’t bother me too much. It was the launch tower/crane swinging around grabbing a fuel tanker and slipping it into place that lost me.

I’m just trying to imagine what we could do with 500 tons to LEO. The mind boggles.

23

Also SpaceX talked about getting to other planets and bodies in the solar system, one method was a refueling station around Jupiter to get to Saturn, and perhaps another refueling station to go further. But this does not make sense to me as the refueler has to have a orbit to be able to ‘mine’ material and Jupiter has a very deep gravity well. Climbing down into a refueling orbit, then having to climb out again, I mean wouldn’t a gravitational slingshot be overall faster and more effective?
I guess if you can just make Jupiter, getting refueled there makes sense to go further, but we already have the means to launch into interstellar space. Perhaps just another means to raise interest and support, but this is just not making sense to me.

24

The radiation on Mars is not quite as bad as it’s sometimes made out to be, and not tremendously more than just being on a commercial plane flight: around 15-30 uSv per hour, while a plane flight is around 8 uSv per hour.

Limiting hours on the surface would improve matters–sleeping+working 16 hours underground and spending 8 on the surface would reduce the dose to ~90 mSv/year, which is already less than the “lowest one-year dose clearly linked to increased cancer risk” of 100 mSv (as shown on the xkcd chart).

In some long-term terraforming scenario, the atmosphere will provide additional protection. Of course, given that it’s centuries or millenia off, I’d hope that cancer is a thing of the past anyway.

25

Why is that? The tanker weighs 90 tons dry, which is is a very modest load for a fixed crane. Although the did it inside a building, the Saturn V was also built by stacking via crane. Being only two stages, the ITS should be a much easier assembly than the Saturn V, Shuttle, etc.

26

I watched the presentation, and went over what technical information is available. To me, it looks feasible at the ‘handwaving’ level. In a large project like this with so much new hardware and new concepts, it’s going to be the unknowns and the little technical details that bite you in the ass.

Musk is setting aspirational goals. Even he probably doesn’t believe he can hit them. But setting short timeframes helps keep people motivated, helps with funding and getting approvals accelerated, and all that. I’d be surprised if the first BFR got off the pad before 2023, and the first unmanned flight of the hardware with an ISRU on a lander happened before maybe 2028 or so.

But this isn’t the real problem. The real problem is that the idea of sending thousands of people to Mars to form a permanent, self-sustaining colony is completely daft. We don’t even know if we can keep a single person alive on Mars for the 26 months between launch windows without sending enough food and water. We don’t know how to make a self-sustaining biosphere yet. The couple of times we’ve tried we failed.

A self-sustaining, high-tech civilization is a LOT different than sending settlers into the old west to live off the land. Estimates for the minimum number of people required to maintain a technological civilization run into the millions, not thousands. You need machines that make the machines required to make other machines. You need mining, and rare materials, and the machines that can do the mining. You will be doing all this in an environment that requires high-tech pressure suits, specialized vehicles, etc. When these break down, you need spare parts. If you run out, you need to make them out of raw materials.

So think about this: Every person Musk sends to Mars is going to be dependent on a supply chain from Earth for survival. As Musk lands more and more of his ‘colony’ there, the supply chain grows in size. At some point, if you had thousands of people on Mars you would need a steady stream of hundreds of rockets coming and going just to keep the people supplied with hardware and food and medicine and all the other things they won’t be able to make for themselves for decades or centuries.

Musk hand-waves all this away as not being his problem. He figures if he just focuses on building the rockets, others will figure out how to do it. I think that’s crazy. Terraforming Mars, even if we could figure out how to do it, would take thousands of years. In the meantime, he’d have thousands of people essentially being wards of the Earth and reliant on the Earth being willing to essentially donate billions of dollars per year to them.

That’s also where Musk’s idea that anyone can go for the price of a house is completely nuts. The people that go there are going to represent ongoing costs on a huge scale. Therefore, the only people that should go are the highly trained specialists required to carry out a specific necessary task on Mars. They are going to need a habitat, food, water, and other supplies for at least 26 months, and once there are going to have to be able to contribute meaningfully towards the long-term survival of the ‘colony’.

My guess at a more realistic timeframe:

2025 - the first BFR is launched into orbit as a demonstration/test.
2028 - the first Mars transfer vehicle/lander is sent, with a prototype ISRU.
2030 - a small group of astronauts is sent to Mars to check out the now-fueled return vehicle, collect Mars samples, and return to Earth with them. There, the vehicle will be carefully inspected for its condition after two years on Mars.
2032, another ISRU-equipped vehicle is sent back to Mars.
2034 - A larger group of astronauts (maybe 20) is sent to Mars to start building permanent habitats, but with enough food and supplies to survive if everything goes sideways.
2036 - Another group of astronauts is sent to join the first group, bringing whatever new hardware was deemed necessary from the experience of the first bunch. 3D printed habitats or inflatable habitats covered with regolith begin to be constructed to house 100 people.

And so on. And this assumes that everything goes according to plan. Rockets blow up, landers fail… When you can only iterate once every 26 months, failures are incredibly expensive.

At some point, we’ll either run out of money or willpower to continue and recall everyone home, or we’ll figure out how to live there with minimal resources from Earth and the experiment will continue but will remain small - like McMurdo Station in Antarctica or something like that. Eventually we may build up enough knowledge about how to live and work on Mars that we could truly start something on a larger scale, but that’s decades away at best.

I’m not against this, mind you. It’s Musk’s money. I’d rather have him spend it advancing space science than blowing it on Mega-Yachts like other billionaires do. I just think this is more marketing and inspiration than reality at this point.

27

The person who may be more interesting to watch soon is Jeff Bezos. He also has a large advanced rocket engine - the BE-4. He has experience with reusable landing technology. And his company, Blue Origin, is building the ‘New Glenn’, a very large reusable rocket. It’s not as large as the BFR, but it’s still capable of throwing a huge payload into orbit.

More interesting is the name of his next rocket - “New Armstrong”. That suggests that Bezos’ plan is to go to the Moon, not Mars. And that makes a whole lot more sense. The discovery of large amounts of water and other volatiles on the Moon makes it commercially interesting, and the recent discovery of ‘skylights’ opening into what look like gigantic lava tubes and domes makes the moon a better target for a permanent, self-sustaining civilization. What sounds easier - terraforming an entire planet, or sealing off and pressurizing an underground dome that’s miles across and could house 10,000 people?

The moon may have hundreds of such domes, and thousands of lava ‘tubes’ that could be half a mile across and many miles long. You could probably support millions of people living underground in those things. And we’re not really talking about ‘cave’ living here. We’re talking about hollow structures so large that they’d feel more like living in a large urban park or something. In the case of the potentially largest lava domes, you might even have blue sky and local weather with the right lighting design.

Inside a lava tube/dome you are completely protected from solar radiation, micrometeorites, and harsh temperature swings. The temperature is a constant -20C, which can be dealt with using standard heating technology. The surface is a vacuum, meaning solar panels would be very efficient and could be built extremely lightweight. Nuclear power plants on the surface feeding cables into lava tubes could provide virtually unlimited power.

The Moon is close enough that people there could stay connected to the internet, so they wouldn’t feel as isolated. Turnaround times in the case of emergencies are days, not years. Having no atmosphere it is feasible that the moon could have mass drivers to launch materials into orbit. Harvesting water and turning it into rocket fuel, then launching it into space with nuclear-powered mass drivers could dramatically lower the cost of deep space missions. The moon could feasibly become a resort/retirement/adventure destination. Monetizing a moon program has to be much easier than monetizing a Mars colony. And that’s critical to the long-term survival of any colony.

But just as important is the iteration aspect - to get really good at space travel, we have to do a lot of it. We need short development cycles, and fast iteration of designs. The moon promises to allow for that. You can launch any time. You can be there and back in a few days. You can learn from mistakes, make changes, and fly again in a few weeks or months. Iteration is what’s needed for space travel to become safe and inexpensive. Mars just doesn’t have that kind of potential for rapid development.

In the near term, imagine the excitement of exploration missions to venture inside lava tubes. Can you imagine those first images when a robot or an astronaut fires up a spotlight and we get our first glimpse into a giant lunar cave that has been left pristine for billions of years? With cheap enough rocket technology, that’s the kind of stuff that could be funded by private investors, billionaires, movie studios, or even kickstarter projects for small rovers.

There may even be potential for gas mining for nitrogen and other rare volatiles we’d need. Many lava tubes are still sealed, and outgassing may have pressurized them with various gases. We won’t know until we go. The Grail gravity map data shows that about 12% of the regolith consists of voids of various sizes. No telling what’s trapped in there from cometary impacts, outgassing, etc.

So if Bezos goes to the Moon and Musk goes to Mars, my money is on Bezos.

28

I think that’s the point though, the knock off benefits of developing an interplanetary supply chain would be enormous.

29

Maybe. But it’s not a self-sustaining space colony, which is what Musk says he’s going for. And that supply chain is going to be bloody expensive. And I’m not sure the benefits of an interplanetary supply chain are going to be worth that cost for a very, very long time.

30

The problem with this “interplanetary supply chain” is that it is still dependent upon sending resources from the surface of the Earth to depots and ‘colonies’, which is like sending your dry cleaning to India and having pressed clothes returned; sure, FedEx can do it for you, but even leveraging off of reducing costs by bulk shipping it makes absolutely no sense, and if attempted to do it at too large of a scale, e.g. if everybody in the US sent their dry cleaning to India, it would overwhelm the logistics. The essential capability for self-sustaining space-based or interplanetary installations is in-situ utilization of basic resources such as water, oxygen, nitrogen, organic compounds, structural metals and ceramics, fissile elements, et cetera, and these need to be extracted and refined in bulk as a precursor to any large scale settlement, which argues for a high degree of automation preceding large scale crewed exploration.

The notion of resourceful and ingeniously colonists building hydroponics farms and making a permanent settlement on Mars invokes the heroic myth of scrappy pilgrims building a new life and enjoying newfound freedom in the wild frontier. This notion, however, fails to consider how often colonies in the New World failed despite having abundant natural resources and cultivars left by the previous occupants devastated by the plagues the Europeans brought with them in one of the most agricultural fertile places in the world. Mars, on the other, has virtually nothing to benefit or aid potential colonists; it has essentially no surface water or accessible ice save for the salt-choked ecurring slope lineae. The regolith of Mars has no observable sources of bio-available nitrogen sufficient for fertilizing plant life, which means that hundreds of tons of ammonium nitrate or other fertilizers would have to be delivered to sustain enough crops to support even a small population, while the surface soil would have to be washed of the alkaline salts that would kill any plant that attempted to grow. Mars gets about 43% if the incident sunlight compared to Earth; that is somewhat offset by the much thinner atmosphere which is far more permeable to visible light, but it also filters almost no UV radiation, which means that only UV resistant materials could be use for permanent structures; no polycarbonate windows or unshielded elastomeric seals. Dust storms can also occlude sunlight for months at a time so any energy source for plant growth or other critical functions will have to be something other than solar.

Talking about the atmosphere, Mars is regarded as being the most difficult solid body to land upon because of the thin but not negligible atmosphere which is insufficiently dense to provide lift at subsonic speeds for any reasonable size lifting structure, but will still create an intense aeroheating environment at aerobraking and orbital entry and descent speeds, mandating either really large inflatable decelerators and a significant propulsive landing capability which is a large driver on payload mass. Landing thousands of tons of equipment and materials in a recoverable manner on Mars will require a truly massive amount of propellant (as in petroleum supertankers worth) that has to be transported from Earth’s surface to Mars orbit.

And yet, the challenge of rocket propulsion–the one that Musk is addressing in this presentation–is about the easiest and most straightforward of all of the challenges of crewed interplanetary travel and colonization. The biggest challenge is the people themselves; keeping them alive, protected from space hazards, supporting physiological needs for health and functionality, and all of the psychosocial challenges of isolation, stress, and social interactions in a restricted group, which have been a major problem in nearly all long term team isolation studies. We don’t have any long term data about the physiological response of the human body in significantly reduced gravity and elevated solar radiation environment, but what we have found from the last fifteen years of research at the International Space Station is that the impact of freefall conditions and almost exposure to almost unfiltered cosmic radiation poses greater problems that previously suspected with little in the way of effective mitigations other than simulating gravity and putting large masses of water or another dense substance between the crew and outside space. There is evidence that even the relatively short durations of the Apollo flights beyond Earth’s magnetosphere may have had a detrimental impact on the health of astronauts who went to the Moon.

I do have to take issue with attempting to establish a colony on the Moon. While some of the challenges are reduced (e.g. there is no atmosphere, and the duration of exposure to radiation during a transit is much lower) but the basic problems of the logistics required to establish and support such a capability largely remain. Most of the effort to get resources to another celestial body are just lofting them into orbit, so there really isn’t a great savings, and while landing equipment on the Moon is substantially less challenging, there are even fewer native resources to utilize, and the problem of electrostatically-charged lunar dust on the well-being and functionality of both crew and machines is not to be understated, notwithstanding that the 1/6 g gravity will likely have an even more detrimental impact on human physiology long term even if the occupants are well protected against radiation. Although we have confirmed that there is water in the regolith of the Moon and modest amounts that may be in permanently shadowed craters, the actual amount is vanishingly small or found only near the polar regions and would require grinding through tons of regolith to recover liters of useable water. There may be some practical reasons for establishing an outpost on the Moon for scientific purposes of learning more about lunar geology, but logistically it really isn’t that advantageous.

One critical capability that is often overlooked for any kind of large scale interplanetary exploration is the need for a suitable communications system that would service missions at interplanetary distances. We currently communicate with anything beyond High Earth Orbit via the NASA Deep Space Network, or comparable systems operated by Russia and India. These systems are just barely adequate to maintain communications with the few number of current interplanetary missions, and use systems and components that are obsolescent. A solar-orbiting, space-based communications system is pretty much mandatory for such an effort, and the cost and development time for deploying such a system is not inconsequential but doesn’t seem to be any part of Musk’s plan. This may fall under the umbrella of “somebody else will take care of it,” but at a cost likely approaching ten figures it really can’t be done by anyone short of a government-funded program.

From a practical standpoint it makes far more sense to develop the ability to remotely extract and processing space-based resources, and all of the infrastructure to support that as a precursor to crewed exploration or any attempt at space colonization, and it probably makes a lot more sense overall to built large habitats using minimally processed space resources such as water ice and silicate fiber than to build ‘colonies’ in tunnels under the surface of Mars or moons.

Stranger

31

I agree that self-sustaining colonies are a long, long way away, whether on the Moon or Mars, and that there are many other things you need to figure out before attempting it.

The thing with the Moon, though, is that it at least offers a potential path to commercially bootstrap your way to a real lunar infrastructure. The moon is cheap enough to get to that we already have companies planning to send landers there. The lunar X-Prize already has two companies who have purchased payload space on rockets for their landers.

The logistics of getting people to the Moon and back are again orders of magnitude better than getting them to/from Mars. We did it in the 1960’s and 1970’s, and we can do it again. Transit times of a few days instead of a few months are a huge deal.

If landing on the moon can be done cheaply, there is even the possibility of commercial exploitation in the form of expeditions and movie/TV rights. James Cameron would happily spend a half a billion dollars of other people’s money to film a moon mission, and that’s in the ballpark of funding for huge motion pictures.

Water in the lunar regolith would certainly be hard to extract, but the water at the poles is likely in the form of huge sheets of ice just sitting in permanently-dark craters. The lack of an atmosphere makes it possible to use small jump rockets or mass drivers to move the water to where people need it. Or just locate the base where the water is. We’re not talking about a small amount of water - Chandrayaan-1 found 600 million tonnes of it in 40 permanently-shadowed craters, and there’s no doubt much more yet to be discovered.

As for the lava tubes - some of them look like they have horizontal openings at the mouth of collapsed sections of lava tubes, meaning we might be able to just walk right into them. At first we wouldn’t pressurize the tubes, but something like a Bigelow inflatable habitat would be given instant protection from cosmic and solar radiation, temperature fluctuations and micrometeorites if placed inside one. Rather than building habitats in situ or covering inflatable habs with tonnes of regolith, we might be able to just drive one or more of those into the mouth of a tube and set it up inside.

The lunar dust is a real problem, as is the apparent lack of nitrogen for any long-term habitation. However, it’s possible that we might find pockets of nitrogen from cometary impacts or in cavities filled from outgassing. Nitrogen exploration might be one of those things that captures the imagination and leads to speculation and a ‘gold rush’ of sorts.

But once you get to the point where you can pressurize a lava tube, all the surface problems go away. Dust can be managed, radiation and meteorite risk goes away, etc.

Sure, this is all speculative, there are many hurdles in the way, and it’s high risk. It may be that the reward isn’t great enough to do it in the near future. But compared to the feasibility of actually building a self-sustaining colony on Mars, I’d take it any day.

Also, colonizing the Moon would require the interim development of hardware that strikes me as being much more useful than an ‘interplanetary supply chain’. We would be perfecting techniques for working in vacuum, small transfer ships between Earth and the Moon which could also be used for asteroid mining or transfers in Earth orbit, methods for mining, smelting, and transporting materials from bodies in a vacuum, low-gravity and zero-gravity manufacturing and living, and so on. These strike me as ‘core’ capabilities required for serious spacefaring, whereas much of the technology needed for Mars will be specific to that environment. And, because we would be iterating faster, development will be faster.

My idea for exploiting the moon would start with prizes for the first company to build a lander that can safely descend into a lava tube and send back images, another prize for a rover that can completely map one out, etc. Those would make for compelling pay-per-view or sponsored TV events. If we can cut the cost of space access by a factor of 10, that’s a reasonably self-funding idea. If Bezos’ New Glenn or New Armstrong can send serious payloads to the moon, manned missions become feasible for much less than the billions of dollars a Mars mission would cost.

And if it all goes sideways, like a biosphere collapse for a small station, you can shut it down and get the people off quickly. If something goes wrong on Mars, you’ll have a lot of dead colonists.

32

I’m hoping AI will make human-bearing spacecraft faster and cheaper.

I like the lava tube on the moon idea, but I can’t imagine people spending more than six months under such low gravity. Kinda the same deal with Mars.

If we can make automated fuel makers, how much more difficult to make automated rotating space colony makers? I still think a huge rotating cylinder is our best bet for becoming “interplanetary.”

33

Martian regolith contains water; 1.5-3% in some areas. Some places actually get water fog.

Nitrogen, I’d hope, would be largely recycled. Small amounts are available on Mars (nitric oxide in the regolith and about 2% N2 in the atmosphere), but in any case it should be possible to close the loop on nitrogen (not true of water, which will be used for methane production).

True; and yet methane is cheap. If my math is right, LNG costs about $0.32/kg (the prices I see are in the lovely unit of MMBtu). The ITS needs about 2 million kg per launch, and they need about 5 launches to send the craft to Mars with 450 tons payload. That’s only $3M in fuel. Probably around $10M with LOX costs included. Multiply by 10 to get “thousands” of tons and the cost is still trivial. Obviously, the propellant is still not the long pole here.

I think it’s important to keep manned exploration separate from colonization. Although Musk glossed over the difference in the presentation (understandable for a 1-hour layman lecture), I think it’s pretty clear that the first missions will have only a few people and that building up infrastructure will be the primary mission. There’s no way they’ll have sustainable food production from the very first missions.

Prior to that I could foresee automated missions, though setting up sophisticated infrastructure with no human help might be tricky. Still, things like deploying large solar arrays and dropping large pieces of equipment like reactors isn’t too insane.

34

Whose lifetime? There are people alive today (perhaps even some on this message board) who may see the year 2100 and 84 years is a really long time.

I’ve read that Elon Musk wants to do this to ensure man’s survival in the event of an extinction event. That’s a laudable goal (and a reason to get off the planet that sending a machine won’t accomplish) but it’s not something that should be the responsibiity of one person or one company.

In high school, I read several books by the Princeton physicist Gerard K. O’Neill, who advocated large orbiting colonies. His books had descriptions of how the Moon could be mined for construction materials and the colonies built in space, with large solar generating plants to provide energy for those on Earth. These ideas captured my imagination for a long time.

35

Having never snapped a two stage rocket together it simply seemed far to fast, smooth and simple.

36

I think Stranger is referring not to the cost of the fuel that must be sent to Mars, but to the cost of sending that fuel.

37

Well, it was CG :). Even in the video they present it as taking the better part of a day (see the movement of the sun). And sure, there would be a lot of wiggling around and such to get the placement perfect, which isn’t shown, but there’s nothing wrong with the basic principle.

No doubt–I was really just clarifying that it’s not about the propellant as much as the flights required to get it into orbit. In particular, the booster stage will need to have almost perfect reusability for the costs to be at all reasonable. The propellant costs are irrelevant; the airframe costs are not. SpaceX is claiming 1000 uses for the booster stage, which sounds pretty aggressive but not impossible. I suspect that the flight success rate is the limiting factor here (as compared to degradation of the airframe)–they need to have 99.9% reliability to get 1000 uses out of it. No one has achieved that kind of reliability in a rocket yet.

38

O’Neill’s colonies in space are the perfect cautionary tale here. There are some concepts and ideas that seem eminently feasible at a very high level, but which become completely infeasible once you actually try to solve the problem in detail. Space elevators fit in this category as well.

I remember when people were seriously convinced that we would have colonies in space by the year 2000, constructed from materials fired from the moon with mass drivers. When ideas seem simple in concept, it is easy to overlook the impact of the details.

In the case of a mars colony, one of those details is that long before you can reach a size that is self-sustaining, you will need to be sending a flotilla of ships to Mars just to keep alive the thousands of people already there but unable to provide for themselves.

Hmm… Maybe that’s Musk’s plan after all. He doesn’t expect those thousands of people to be forming a viable colony any time soon - maybe he wants them as hostages to a space program, to force Earth to continue to develop space technology. If Musk keeps dumping people on Mars 100 at a time for a few decades, he can create a situation where Earth either continues to spend money to develop its space-going capabilities, or someone has to make the conscious decision to let thousands of people die because it’s too expensive to keep them alive.

39

A nice report on the Raptor engine:

It’s actually further along than I had thought–they demonstrated a full engine, just scaled down to 1 MN thrust. The full thing will be 3 MN. I wasn’t sure if this test article had even included the turbopump machinery and such, but apparently it’s basically complete.

It’s the second full-flow staged-combustion (FFSC) engine to reach a test stand ever; first cryogenic FFSC ever; first American engine with an oxygen-rich stage; highest power/weight ratio by a wide margin; etc. Lots of firsts with this engine but it seems they’re making good progress.

The use of 3D printing really seems to be revolutionary. Cooling channels in particular are absolutely critical to the design, but tend to make the engines very difficult to produce (the RL-10, for instance, costs $38M/engine, in part due to the manually brazed cooling channels in the nozzle). Here, they are printed right into the design. Likewise, the LOX machinery is tightly integrated into the top of the combustion chamber. Fewer parts, less stuff to go wrong, and cheaper.

I wonder if the first cargo shipments to our Mars colony should be several cubic meters of Inconel powder (the superalloy that SpaceX uses with their printing process).

One thing that came up in a presentation I saw a while back is that methane engines make combustion modeling tractable. In any combustion process, there are numerous intermediate products that all play a role in the time evolution of the process. For kerosene-LOX, there are thousands; perhaps tens of thousands. With methane-LOX, there are around 300. While still very high, this is low enough that can be simulated with modern computers. SpaceX therefore should have very accurate models for their combustion and will be able to pinpoint any inefficiencies or instabilities with relative ease.