In 2013, I walked through roughly 24 grand challenges to space settlement and set about breaking it down as a scientific, engineering, and business problem simultaneously. The key was to find a way to flatten the investment and innovation curves required (reducing time and saving money) while making things modular and keeping consistent standards for the first major phase of space settlement. That talk is here on YouTube and the presentation is here. This series will break down each challenge, the current state of the solution set, and proposed paths to move forward efficiently.

The Problem

There must be an affordable way to get payloads into space in bulk greater than 50 tonnes to low earth orbit, and ideally much more than that. This problem is dual – low cost and high mass. Low cost, low mass payloads are useful for experiments and commodity payloads like supplies, but they are not useful to crewed vehicles because pressurized compartments are difficult to assemble into coherent structures. A 100 tonne vehicle divided into five, twenty-tonne launches would spend too much of the mass on separate pressurized volumes and bulkheads between modules. High cost, high capacity vehicles like the Space Launch System are also marginal because they aren’t affordable enough to launch regularly.  They can't have an impact on settlement because they cost too much and fly too infrequently to make a difference. 


On the commercial side, there are three low cost, high capacity SHLLV boosters in development.  This article compares what we know about each so far. 

New Glenn (Blue Origin):  Unfortunately, we don’t have any real numbers on Blue Origin’s New Glenn launch vehicle. Fortunately, there is nearly zero chance of Blue Origin running out of money on the development. Jeff Bezos is worth $66.5 billion with as a constant revenue source, whereas Elon Musk is worth $11.3 billion on ventures that run on thin profits or negative, growth-focused margins. Secondly, the vehicle construction facility has made progress. We should see something flying within 5 years of the proposed launch date of 2020, because Bezos tends to be conservative with his scheduling.

If New Glenn can actually deliver larger payloads to LEO, it will effectively cut into both Falcon 9 and Falcon Heavy launch markets. The problem is – it needs a high-powered second stage to get beyond LEO. That said, Blue Origin already has a cryo-engine (for New Shepherd) and a relationship with United Launch Alliance to build engines for their future projects. Falcon 9 uses its second stage alone to get payloads all the way GTO, then deorbits the stage. It even launched a payload to the Earth-Sun L1 point, 1 million miles in deep space, with the second stage alone. New Glenn must have a similar capacity in the second generation version. Blue Origin has also mentioned plans on a New Armstrong to bring payloads to the moon and back, and has a strong focus on space settlement in the Earth-Moon system.

UPDATE:  The payload of New Glenn has been announced as 45 metric tons to LEO and 13 to GEO.  The first stage is reusable and designed to last at least 25 missions.  It would land on a large ship at sea.  

Blue Origin has also just announced an robotic cargo lunar lander that could land 10,000 pounds (4536 kg).  It could be launched by SLS,  Atlas V, or New Glenn.  It could fly as early as 2020.

Falcon Heavy (Space-X): This program has been delayed repeatedly, but is the closest to launch. It is basically a combination of two technologies – the Falcon 9FT (Full Thrust) and the ability to transfer propellant from the side stage tanks to the core engine during early ascent, then switch propellant sources to the core stage tanks after the side stages drop away. The former is flight tested, but not with the stress of having several bolted together. The latter has not been tried in any substantial launch vehicle. The engineering problems with this are complex but not dramatic. The fuel is RP1, which is basically highly refined jet fuel. There should be no issues with switching fuel sources because it’s done all the time with aircraft switching tanks, although at much lower flow rates. Switching between super-cooled liquid oxygen sources is more challenging. Bear in mind, the side tanks are not dry when the vehicle stages – they must have enough propellant left to land vertically, and are therefore still under pressure.  If they do not close the valves shortly before separation, they will not have enough propellant to land. This will probably require multiple levels of valve work, which all must function and do so quickly. The motion of the valves while the system is at full pressure on the launch pad should be possible to test pre-flight. Expect a few “learning experiences” during early flights. However, the engineering of a high-flow, cryogenic valve system is routine enough in industry that the system should become reliable in a few years.

Falcon Heavy will be used for Mars Entry Vehicle (Red Dragon) tests and will not require commercial payloads in the near term to keep it funded. If those tests are successful, there is probably a model to sell lab space to nations and universities on future Red Dragon Mars landers, and “Gray Dragon” (my term, not theirs) lunar missions. This would make the research flights self-supporting in the 2020’s, regardless of the status of ITS.

When launch vehicle providers like Ariane 5 made boosters bigger than the satellites they were meant to launch, they simply launched more satellites per flight. Space-X has already demonstrated multi-satellite launches with Falcon 9. The low per-unit cost would drive both the market for more launches and reduce the risk of satellite providers developing heavier payloads for communications and other commercial missions. 4K television and the constant need for more bandwidth for communications could drive the desire for larger, more powerful satellites. The combination of Falcon Heavy and New Glenn being available would also reduce the dependency on one provider for those launches. This risk reduction helps both the satellite manufacturer and launch providers justify going to large-scale capacities. Funding satellites with economy of scale capacities of more than double current systems would drive strong investment in this sector. Satellite television generates roughly ten times the revenue of NASA’s entire budget expense, so it provides a solid economic basis that is not slave to political whims or government budget limits.

ITR/ITS (Space-X): The biggest problem is lack of funding. Elon Musk joked about this in his announcement with a slide that included the line “collect underpants”. This is not only a reference to an episode of South Park, but a subsequent reference in a National Space Society 2011 keynote on space settlement where the X-COR CEO Jeff Greason used it as a metaphor for space settlement funding models.

Interplanetary Transport System (Credit: Wikipedia)

In the table below, note that the hypothetical super-booster Space-X was proposing prior to the ITS as an SLS replacement would have cost less to develop than ITS, but would have had a much higher cost per flight.  I assume this is because it would have been built with far less cutting-edge carbon fiber technology, because the carbon fiber fabrication technology for ITR and ITS was only developed in the last two years. ITS will require either massive government investment (unlikely given the combination of technical risk and cost), or internal investment from other Space-X and “Musk, Inc.” ventures such as the proposed internet satellite constellation.

The problem with the satellite constellation is that it lacks a business model that is not currently exploited by Google. Apple sells expensive phones and collects commission at the app and music stores. Google gives away operating systems for cheap phones in exchange for advertising revenue and marketing data. Google benefits directly from the next billion poor people owning cell phones in remote areas, because they get that much more exposure for their advertisers. Space-X has a design for small, magazine-sized antennas. This could be an option for cable-cutters if those antennas can be stuck to the ceiling or high-rise window above a modem. But there won’t be enough exposure in remote areas to turn a direct profit – a lesson Teledesic, Iridium, and Globalstar learned the hard way with the profusion of cell phone towers in third-world countries.  While Google's satellite plans are on hold, their "Project Loon" high altitude balloon system is still in active development. 

Cost/Mass Estimates


Dev Cost

Per Launch


Payload (MT)

Launch Rate






1 per 24 Months






1 per 48 Months

Falcon Heavy





1 per 3-6 Months

New Glenn






"Falcon XX"











1 per Day

Table Notes:  The development costs for SLS and Orion are through 2015, and they aren't done yet.  Orion can only be launched on SLS.  The development cost for ITS and ITR are from the announcement video - it is far too soon to say if they are accurate.  The price for "Falcon XX" was given by Musk when trying to get considered to develop a replacement for SLS.  This was before the advanced carbon fiber methods of ITS/ITR were commercialized, so probably reflected more conventional construction but the same engines as ITR.  Launch Rate is how many months between launches.  The budget for maintaining SLS is expected to be $4 billion/year, so with a flight rate of once every two years on average, that equals $8 billion per launch.  As for the prices, nothing is truncated so that the extreme differences in prices are more easily seen. 

Robert Zubrin (Mars Direct, The Mars Society) has proposed modifying ITS to a more conventional approach with more separate systems at a much-reduced price. This would involve an independent second stage that moves the spacecraft to high transfer orbit then returns to Earth a week later. It would also reduce the fuel capacity of the ITS spacecraft.

I think Elon Musk is going for the future DC-3 (a technology revolution with forward looking design that will do whatever, wherever), whereas Robert Zubrin is going for the future Ford Tri-Motor (a purpose-built, less risky, lower tech design with a higher probability of becoming obsolete sooner). Given the high development cost of the ITS, Dr. Zubrin may have a point. There is also great risk in going from a simple capsule (already weighing far more than any Mars Entry Vehicle in history) to a massive spacecraft with no transitional forms. The idea of landing the first stage back in the launch cradle also seems a bit risky the first time out. While we don’t want to get bogged down in development iterations for the next four decades, we also don’t want the company to fail because they go too deep too fast, and something goes wrong with an irreplaceable investment.  

I suspect a mini-Raptor launcher with fewer engines, a second stage with on-orbit refueling doing Zubrin’s highly elliptical transfer orbit, and a smaller crewed vehicle could do a smaller crewed Mars mission without the $10 billion upfront investment, while reducing the risk to that investment. It could be scaled to go beyond both Falcon Heavy and New Glenn. It could do crewed lunar missions without breaking a sweat, while demonstrating lateral biconic entry vehicles with vertical landing on Earth, the Moon, and Mars. Each Raptor engine is the equivalent to three Merlin engines. That means a Raptor in the same configuration as a Falcon 9 would have the same capacity as the Falcon Heavy, but would be far easier to maintain and be more competitive with New Glenn. It could replace the Falcon family entirely and keep the entire Space-X ecosystem in a single engine, single fuel advancement effort. As a bonus, a space-refueled massive tug could transport crewed labs anywhere in deep space from Earth-Sun L1 and L2 and Lunar orbit. It could also prove out the all-carbon booster and spaceship configurations on a smaller, commercially supported vehicle before betting the company on a larger investment.

It would be far easier to find investors, government customers, and payloads for an ITS with flight-proven hardware, construction methods, and landing approaches. That said, when confronted with the fact that a $35,000 electric car would lower the cost to the point where production needs would require the doubling of lithium battery construction for the entire world, Tesla built a single factory with that much capacity that is the largest building in the world.


Space-X has a strong frenemy in Blue Origin. No CEO of a satellite manufacturer is going to go out on a limb to create billion-dollar communication satellites that no one can launch if Space-X goes out of business. But with two launch providers, and one having a strong financial backer, the risk is reduced enough to green light such developments. We could theoretically see satellites with four times the capacity at twice the mass, depending on how the economies of scale shape up with such a system.

As a corollary, satellite refueling and servicing missions would make more sense than in the current satellite market – particularly if satellites are built from scratch with this capacity. Lower launch costs would allow for lower cost servicing missions. This leads to more experience with fuel transfer in microgravity, robotic servicing, and so on. I’ll have more to say about that in a future article.

Large inflatable habitats for future space stations from Bigelow will also be mature around the time these systems are able to launch them. The current space station also is expected to be retired around the mid 2020’s. Its replacement may be rental space from a private company, but at far higher volume.

With the incoming administration, there are rumblings that SLS will be cancelled to make room for Space-X and Blue Origin to make a cheaper, more capable system. NASA could then spend the $2 billion per year budgeted for SLS on something a big rocket could actually launch, like larger space telescopes or crewed missions to the Moon and Mars.

The Grand Challenge Series

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