A recent newspaper column by Michael Griffin and Daniel Dumbacher claims the new SLS launch vehicle is essential to the nation’s space program. The column also claims that SLS costs are expected to be about the same as current commercial launchers. Griffin is a former NASA administrator, and Dumbacher is a former deputy associate administrator.
NASA has its critics, and it has a demonstrated history of badly underestimating costs, which is primarily why it has critics. I am not interested in criticizing anyone. Personally, I am just interested in the best facts and estimates that I can uncover. The SLS will certainly have its critical uses. I am less confident than Griffin and Dumbacher in its cost-effectiveness.
Back in 2012, I searched out payload data and launch cost estimates for several launch vehicles, some domestic, and some foreign. There was some conflicting information, which I resolved as best I could. Where possible I used data direct from the manufacturers. Some of the vehicles I researched are no longer flying, some have not flown yet, but most are flying today.
To this database I have added this year the historical data for the NASA space shuttle (now retired), and the best available projections from NASA (and from NASA’s critics) for its new SLS vehicle, currently under development. There is considerable disagreement and uncertainty about the projected launch prices for SLS in its 3 projected versions. Much depends upon the actual flight rate, which was presumed to be once a year for the data I used. See figure 1 for my database.
This kind of data comes from sources across a multitude of years, which requires correction for inflation to a common comparison year. My original database is corrected to 2012 dollars, and I did not change that. The SLS estimates have not really changed by any amount I could find from 2012 to present. Inflation rates have been quite low for many years. I used 2% as a representative figure. See figure 2 for my inflation-adjusted launch prices.
What I generated with this data was a plot of unit prices to low earth orbit (LEO) as a function of payload mass sent to LEO. You calculate this as launch price divided by the max payload capability (in this case to LEO). Then you plot that unit price versus max payload. It is generally expected that there should be a gently-decreasing trend of unit price as payload size increases, especially for vehicles that compete commercially in the satellite launch business. This is the “price break for larger sizes” effect, in rockets.
This unit price (expressed here as millions of 2012 dollars per metric ton of payload) represents a minimum unit cost to send payload LEO, obtained only because the rocket flies “full”. You must remember that the rocket costs the same to launch whether it flies “full” or not. If the rockets fly “half full”, then the achieved unit prices are twice those reported here. 10% full is 10 times the price, etc.
The units of measure here are 2012 dollars (in millions) and payloads measured in metric tons. A metric ton is 2205 pounds per ton instead of the US customary 2000 pounds per ton, so a metric ton is about 10% larger than a US ton. But that’s still pretty close.
I used two estimates for NASA’s SLS system: their target is $500 million per launch at about one flight per year, while their critics contend that figure is likely closer to $1000 million ($1 billion) per launch, at that same flight rate. Thus I show a lower-bound curve (NASA) and an upper-bound curve (their critics) for SLS. See figure 3. I used the same launch price for all three versions of SLS, because the data are still too uncertain to resolve the price differences among the three configurations.
The expected trends of gentle price break with larger rockets is definitely there, as illustrated by the commercial rockets. That would be the Spacex Falcon family, the ULA Atlas-V group, Ariane, Proton, and ULA’s Delta-IV. For the 20-ton class of payloads, prices range from about 5 to about 8 million dollars per ton to LEO. Extrapolating, we would expect lower numbers at 50 and 100 tons, based on these trends, perhaps in the 1-3 million dollars per ton range.
The Titan-IV data are considerably higher at around $23M/ton for a 20-ton-class payload, but that is because Titan-IV was never used for commercial competitive satellite launch. The others discussed so far were; it’s not about the rocket as much as it is the logistics that support it. That is how prices were reduced by a factor of 3 or 4, for the same basic technology and the same payload class. Titan-IV no longer flies, it is obsolete and fairly-recently retired.
The data point for the space shuttle represents an entirely-different technology: the semi-reusable boosted space plane, not a throwaway rocket booster. Its deliverable payload in the cargo bay was 20 tons to LEO, but what was sent to orbit was that plus a recoverable space plane, totaling 100 tons. For my curves, I based the unit price on deliverable payload. If instead you base that on the entire orbiting vehicle, that unit price drops from $75M/ton to about $15M/ton, very comparable to the non-commercial Titan-IV.
However, that’s still about factor 2-3 higher than what is currently available commercially in the same payload tonnage class. In that sense, the two government-only vehicles (shuttle and Titan-IV) illustrate quite clearly the effects of commercial competition upon simplifying logistics to lower the price per launch. Commercial is about factor-3 cheaper for the same thrown payload than government.
That government-vs-commercial effect shows up in the projected unit prices with NASA’s new SLS, even if you accept their launch price estimates. Over the 70 to 130 ton payload range, that unit price ranges from about $7M/ton down to about $4M/ton.
So far there are no commercial vehicles in that payload class, but based on the commercial unit price trend, one might reasonably expect such vehicles to price out closer to $1-3M/ton. The SLS might actually turn out to be closer to $8-14M/ton (my upper-bound curve), if NASA’s critics are closer to right. In any event, it is unlikely to fly before 2018 at the earliest, based on what I read. And it is very unlikely to be as cheap as any commercial rockets that may come to exist in that size class.
Given those data that demonstrate a clear commercial cost advantage, I would suggest for the near term using SLS only for those missions absolutely requiring 70-130 ton payloads. Anything and everything else ought to “fly commercial” for around factor 3 savings. And soon, we won’t be restricted to 20-ton-class payloads on those commercial rockets. Falcon-Heavy is supposed to fly its first time this year, or next year, providing a 53 ton capability.
I don’t know about the other companies, but Spacex is reportedly considering an upgrade to its not-yet-flying Falcon-Heavy that could up its payload capability closer to the low end of the range covered by the SLS configurations (about 70 tons).
Spacex is also reportedly considering an entirely-new vehicle called “MCT” that equals or exceeds the payload capability of all the SLS configurations. It will be very interesting to see how that one prices out, as it will be designed by people with real competitive experience, and with commercial competition in mind from the outset, just like its earlier siblings.
Meanwhile, the political “long knives” have come out in Congress over the recent failures of a Spacex Falcon-9 and an Orbital Sciences Antares. They seek to kill the new initiatives aimed at commercial crewed launch and commercial unmanned space station resupply.
When you think about it, all the rocket makers have had their histories of failures to overcome, so it is clear the “long knives” are politically motivated to protect the older companies from the competition of the newer companies.
Commercial is demonstrably cheaper than government-supplied, and likely will always be cheaper. It would be very unwise to listen to the “long knives”, or to let them win.