by John Walker
September 27, 1993
There's a pretty general consensus that one of the greatest barriers to the exploration and development of space is the cost of launch to low earth orbit. The incessant and acrimonious arguments among partisans of the Shuttle, DC-*, NASP, TSTO, Big Dumb Boosters, bringing back the Saturn V, buying launches from the Russians and/or Chinese, or of developing exotic launch technologies (laser, electromagnetic, skyhook, etc.) conceal the common premise of all those who argue—that if we could launch payloads for a fraction of today's cost, perhaps at a tenth to a thousandth of today's rates of thousands of US$ per kilogram, then the frontier would open as the great railway to orbit supplanted the first generation wagon trains. The dispute is merely over which launch technology best achieves this goal.
Conventional wisdom as to why industry and government choose not to invest in this or that promising launch technology is that there aren't enough payloads to generate the volume to recoup the development cost and, in all likelihood, there never will be.
How much would it cost to find out if this is true?
Could we take a moment's pause from debating which is the best successor to the outrageously expensive way we launch now and, as engineers, ask ourselves just why it is that rockets have to cost tens or hundreds of million of US$ per shot. Space FAQ space/launchers gives approximate per-launch costs of representative systems on which commercial launches can be purchased as:
|Vehicle||Mission cost, US$ millions|
|Long March 3||33|
I've deliberately not included data on performance, reliability, or anything else because that would distract us from the most striking observation about these vehicles; each and every one of them, whatever the technology, country of origin, original design intent, launch history, fuel and oxidiser, success or failure in the commercial launch market, have mission costs in ranging from tens to hundreds of millions of US$.
Why is this? Why do rockets cost so much?
Let's simplify the problem by focusing entirely on expendable boosters built with current technologies—those used in the existing launchers named above. Further, let's consider only pure liquid-fueled launchers (with the exception of Scout and Pegasus, the core stages of each of the above launchers are liquid rockets). From an engineering standpoint, then, what is a rocket?
Well, it consists of a collection, often vertically stacked, of:
Cylindrical fuel and oxidiser tanks
Rocket engines (including turbopumps, gas generators, etc.)
Guidance mechanisms (gimbal joints, hydraulic actuators, APUs)
Guidance and navigation system (IMU, GPS, radio command receiver)
plus other ancillary details like range safety receivers and telemetry sensors and transmitters and the like, and that's about it, isn't it?
Now the question that comes to mind is this: why should something like that cost tens to hundreds of millions of US$?
Cylindrical fuel tanks aren't that expensive, and they make up most of the rocket. (Sure, if you're striving for every last gram of throw-weight in an ICBM, you can push the tankage cost as high as you like, but in a commercial launcher?) And rocket engines are finicky, complicated, and intolerant of defects. Well, yes…but so is a DOHC 4 valve per cylinder turbocharged, intercooled V-8 internal combustion engine, and nonetheless one can purchase such an engine, integrated into a ground transportation vehicle, from a number of manufacturers at a cost three orders of magnitude less than that charged for the rocket, and expect it to function without catastrophic failures or extensive maintenance, for five years, tens of thousands of kilometers, and thousands of mission cycles. Guidance? Again, as long as we aren't gram-shaving, this is pretty mundane stuff—the hydraulics can mostly be adapted from airliners, and the electronics from a PC—“mem'ry for nothin', chips for free”. (For an LEO launcher we don't need radiation-hardened electronics.)
We've seen from the “standing army” argument for launchers requiring minimal (airline-scale) ground mission support the impact of fixed costs on per-mission costs when the number of missions is limited. But the presence or absence of a “standing army”, and the frequency of flights over which fixed costs are spread, isn't fundamentally linked to whether the launcher is reusable or expendable. Consider the following mass-produced expendable rocket.
Number manufactured: 6,240 Number launched: 3,590 Successes: 2,890 (81%) Failures: 700 (19%) In inventory: 2,100 Work in progress: 250 Expended in development: 300 Development program cost: US$ 2 billion Development cost per launcher: US$ 350,512 Total manufacturing cost per launcher: US$ 43,750 Marginal cost, launchers 5000+: US$ 13,000 (Yes, 13K!)
These are actual figures for the first mass-produced rocket vehicle, the V-2 (A-4)—fifty years ago. Prices are in US wartime dollars.
Stating the obvious…. The V-2 was a suborbital vehicle, intended to lob high explosive over relatively short distances. Quantity production of the V-2 at Mittelwerk was accomplished with unpaid slave labour under the brutal rule of the SS. And the failure rate was unacceptable by current standards.
And yet…consider that this was the very first space-capable rocket ever built. That it was manufactured under the constraints of a war that Germany was losing, subject to aerial bombardment by night and by day, with continual supply shortages. That, as a consequence of Nazi slave-labour, the desperate war situation, and the state of current technology, no significant automation was applied to its manufacture. In February 1945 the underground Mittelwerk V-2 factory delivered 800 ready-to-launch V-2s; after the war U.S. intelligence expert T. P. Wright estimated that at full production, unconstrained by wartime shortages, the Mittelwerk plant could have produced 900 to 1000 V-2s per month.
One thousand rockets per month…fifty years ago. Think about that.
Suppose we translate these figures, almost incomprehensible by modern standards (three hundred launch vehicles expended in the development program!) into quasi-modern terms. Consider an orbital launch vehicle two-stage, say, clean and green thanks to LH2/LOX propulsion in all stages. Engines: J-2 or RL-10s or follow-on uprated versions (we'll have plenty of opportunity to develop them and phase them in). A simple two stage cylindrical stack like Titan II, with GPS or ground-commanded navigation. Payload interface is a big ring with bolt-holes and a standard fairing with plenty of volume inside.
Sounds a lot like NLS/SpaceLifter, doesn't it? SSMEs may have marginal advantages over sea-level-optimised derivatives of RL-10 or J-2, but otherwise what's the difference?
What if we launch one every day?
Three hundred and sixty-five a year.
That would be less than one twenty-fifth the production rate of the V-2 under concentrated Allied bombardment in 1945.
How much would each one cost?
Assume we expense the development cost or amortise it over a sufficiently large number of vehicles that it can be ignored. Further, assume that our bigger, more complicated (two-stage), and higher tech (LH2/LOX instead of Ethanol/LOX), launcher costs ten times as much as the V-2, and that 1945 wartime dollars convert into current dollars at 10 to 1. Then, starting with the US$13,000 marginal cost of a V-2, we arrive at a cost of US$1.3 million per launch vehicle. If we launch one a day our total vehicle budget will be US$475 million per year—comparable to a single shuttle flight (no, I don't want to re-open that debate again; let's just say it's the same order of magnitude, OK?). If our mass produced LH2/LOX launcher equals the performance of the Delta 6925 by placing 3900 kg in LEO, the cost to LEO is US$333/kg; if we achieve better throw-weight, this figure goes down accordingly. If we build the thing so cheap, dumb, and heavy that its payload is only 1000 kg—one metric ton—the cost rises to US$1300/kg, which is still a factor of ten lower than the comparable cost to LEO for Ariane, Atlas, Delta, and Titan.
Okay, you say, suppose mass production in these absurd quantities could actually drive the hardware cost down to less than a million and half per bird, we still haven't accounted for the standing army that launch operations require. If it takes thousands or tens of thousands of people to launch tens of vehicles per year, won't it take hundreds of thousands to launch one every day?
Well, why should it? Again consider the V-2. In the two weeks from September 18–30 1944, a total of 127 V-2s were launched from five different launch sites. That's an average of almost ten a day. This was accomplished by two mobile groups totaling about 6,300 men and 1600 vehicles, forced to relocate frequently due to the Allied advance, and subjected to frequent aerial bombardment. It was estimated that, given adequate supply, one hundred V-2s could be launched per day in a “maximum effort” by the mobile units, and that a rate of half that, 350 per week, was sustainable.
Parkinson's law notwithstanding, why, after fifty years of technological progress and experience in launch operations, should it take tens of thousands of people and hundreds of millions of dollars to achieve a launch rate one fiftieth that of a V-2 group launching the very first operational ballistic missile from a launch site with tanks and infantry advancing toward it and airplanes flying over dropping bombs on them?
Yes, LH2 is trickier to handle; a multistage rocket requires a more complicated launch and service facility, and so on. But if we design up-front for a sustained launch rate of one per day, can we not find ways around these problems? Perhaps a mobile transporter / erector / launcher like SS-24 or Pershing II, with fuel and oxidiser delivered by underground pipes that attach to the launch truck. Or something…. Let's tell the engineers to go figure it out and see if they come up with something that works.
It can't be impossible; the Soviet R-7 series launchers (Vostok / Voskhod / Soyuz) almost furnish an existence proof. These launchers, despite their mechanical complexity (4 liquid boosters and 20 first stage engines), are typically launched one to two days after horizontal delivery to the pad. On several occasions beginning in 1962, two manned launches were made from the same pad less than 24 hours apart. On October 11–13 1969, three manned missions (Soyuz 6, 7, and 8) were launched from the same pad within 48 hours.
If we use contemporary sensors and computers to automate the fueling and checkout, why does the “launch team” need to be huge? Bob drives the launcher out to the middle of the circle of concrete, hooks up the hoses, then goes back to the blockhouse and presses the green “Start” button. An hour later, or so, the “Ready” light comes on, and at High Noon he pushes the red “Go” button. Sitting immediately to his right Fred, in the blue suit, follows the proceedings on a laptop computer with his index finger on the orange “Oops” button.
Assuming things go OK, ten minutes after the ship lifts, Bob goes out and drives the launch truck back to the garage where it's reloaded with the next rocket (assume we have ten trucks, or so, to pipeline the setup process and account for attrition). Then it's off the cafeteria for lunch.
Every proposal, prosaic or exotic, for a high-capacity, fast-turnaround launch system immediately runs into the objection, “There just aren't enough payloads to make the system pay. Other than a few established markets for satellites, there just aren't that many profitable, useful, or interesting things to do in space right now, and we already have too many launchers chasing too few launch customers.”
This is the heart of the chicken-and-egg problem that is blocking the development and exploration of space.
As long as launches cost tens or hundreds of millions of US$ each, only governments and the very largest corporations will be able to afford them, and only for the most obvious and essential purposes, such as communication, earth resource, navigation, and reconnaissance satellites. And as long as the number of such payloads is fewer than a hundred per year, who is realistically going to pay to develop a launcher capable of sustained rates many times as great, however cheap it ends up being? You'd just end up with a huge pile of rockets gathering dust waiting for payloads, wouldn't you?
Consider the following scenario. The Agency announces a procurement in which bidders are invited to provide launches, one per day, of 2000 kg or more to a standard Low Earth Orbit, mating with a specified payload and shroud interface and to a prescribed set of services on a flat concrete pad. A suitably derated payload is specified for polar orbit. Bids of more than US$1.25 million per successful launch will be returned unread. The winner of the bid will be awarded a fixed-price contract for 1000 launches at the agreed price. The first 100 launches will be considered development flights and will be purchased at the bid price regardless of success or failure; afterward only successful launches will be purchased. The procurement will be re-competed every 1000 launches; if a new vendor wins with a substantially lower cost per launch, they will be granted the same development period for the first 100 flights. The vendor retains all rights to the launcher design and is free to offer it on the open market independent of the Agency.
Immediately the launch contract awarded, the Agency announces the availability of daily flights of 2000 kg to LEO or 1500 kg to polar orbit. Commercial enterprises may purchase launches for whatever purpose they wish at a price equal to the Agency's cost per launch plus 25%. Unsold flights are offered on a first-come, first-served basis to researchers, government agencies, and individuals. In the event of excess demand, non-commercial proposals will be selected by a peer review process similar to that used to allocate telescope time at astronomical observatories. All risks of launch failure are borne by the provider of the payload; clients should note historical failure rates and build appropriate spares. Provider of the payload assumes all liability for it once it separates from Agency's rocket. Payloads shall be delivered by truck to the loading dock of the Agency's Rocket Garage. All payloads must be supplied with adequate documentation to verify their content and safety. The payload interface specification handbook is available for US$5 from the Agency's toll-free order line; payload test and integration jigs are available in the Agency's regional centres and many major universities around the world. Plans for building your own are available for US$5.
Payloads delivered to the Rocket Garage are inspected to ensure they are not nuclear bombs, sacks of gravel, or otherwise unacceptable. Payloads containing propulsion hardware are reviewed especially closely. Assuming no big no-nos, the payload is bolted to the top of the next free rocket, the requested orbit inclination is dialed into the rocket's guidance system, and it moves down the queue toward the pad.
The adventurous will recall that the Project Mercury capsule had a launch weight of 1935 kg.
If fewer than one payload a day arrives at the Rocket Garage (as is certain at the outset), the Agency will store the excess rockets in the Rocket Warehouse out back, while continuing to launch at least one per week with an inert concrete payload (in a rapidly decaying orbit) to maintain launch team proficiency and verify the continuing quality of rockets supplied by the vendor.
This procurement and offering of launch services is explicitly intended to punch through the chicken-and-egg problem. In essence, the Agency would be spending US$475 million a year on a flock of 365 hens, then waiting to see if eggs started to show up. This runs the risk, of course, of ending up with egg all over one's face.
Suppose it isn't possible to build a rocket that will orbit half the payload of a Delta, launched 50 times less frequently than the V-2, at a cost ten times greater than that primitive fifty year old missile. In that case nobody responds seriously to the Agency's bid, and the Agency goes and blows the money on something else, vowing to try again in ten years.
Now suppose the rockets do start showing up one a day, and departing on schedule with a success rate that makes the supplier's profit margin juicy enough to fund further R&D, but the payloads don't appear. The Agency rapidly becomes the butt of every stand-up comic and a motion is introduced in the Legislature to re-name it the “Orbital Ready-Mix Delivery Agency”. Well, if that's how it plays out, I guess we all ought to pack up and go home then, shouldn't we? Because that would demonstrate, in a real-world test, that there really aren't very many useful things to do in space, after all. That even if we push the marginal cost of launches down to zero, nobody will be able to think of anything to use them for, not for Venus probe science fair projects, personal spysats, hypersonic surfing demonstration/validation flights, nor microgravity research, material processing, life sciences, remote sensing, VLBI radio astronomy, optical astronomy, or anything else. That other than the existing big-market space applications, there's no earthly reason to leave the Earth, that much of the “space age” was based on faulty premises, that the “final frontier” isn't worth exploring.
Is this likely to be the case?
Naturally, things aren't as easy to accomplish in the real world as they are to bandy about on paper. Special relativity limits the velocity with which one can wave one's arms, and the UNDO button doesn't remove a hole you've just bored the wrong place into an expensive piece of metal. Many things might go wrong in an attempt to jump-start the exploitation of space this way. The two real biggies are discussed above: “it won't work”, or “space isn't worth it”. Here are some others I'm concerned about as well.
Given current low launch rates, configuring a range is complicated and takes a long time which couldn't accommodate daily launches, especially to a variety of inclinations. And most existing spaceports can't handle both equatorial and polar launches. Maybe we should plan on Hawaii or Cape York from the outset and get the paperwork started to declare an appropriate air and sea exclusion zone (for two hours per day around the scheduled launch time). Any rocket that meets the launch rate and cost criteria cannot require complex or expensive ground infrastructure.
One reason for insisting on LH2/LOX rather than Kerosene/LOX, hypergolics, or solids/hybrids is that it's clean. We could launch one every minute and contribute less to global warming, ozone layer depletion, and other varieties of atmospheric pollution than 747s crossing the Atlantic every day. Also, exhaust and/or fluffy white clouds resulting from the occasional really bad day aren't harmful to anybody who happens to be downwind. On the solid waste issue, clearly dropping big chunks of aluminum and steel into the ocean every day isn't a particularly elegant way to break the bonds of gravity, not compared to all those sleek paper spaceplanes on the magazine covers. But I suspect if one were to compare the total mass wasted in expended stages to that of non-recycled aluminum cans and automobile engines, it would be an insignificant percentage. It's worth noting that what we're throwing away every day consists basically of aluminum and iron with a dash of silicon, and that these are three of the four most abundant elements in the Earth's crust. Besides, outside the two-hour launch period, salvage boats are welcome to recover the expended stages and sell them for scrap.
So many launches may run the risk of unacceptably polluting the near-Earth environment. Clearly, as noted above, care will be required not to launch payloads likely to explode or otherwise misbehave in orbit. Payloads will probably have to be released in orbits which guarantee the timely decay and burn-up of expended upper stages. We need to make sure the upper stage always burns up completely, leaving no chunks to go “thump” in the night. Payloads intended for high-traffic or high-risk final orbits will require special certification that they will dispose of themselves in a responsible manner.
It may be that if we succeed in pushing the hardware cost down, we'll end up with an airline-like situation where fuel cost becomes a major component of the expense. I don't know how much liquid hydrogen goes for today, and I haven't tried to predict what it would cost when purchased in the quantities a launch a day would require. This needs to be worked out. Even daily launches should be a minor consumer in the market for liquid oxygen.
In the discussion of payload delivery and integration, I confess to glossing over the issue of pre-launch payload servicing. You can't just take a satellite with a solid kick motor and a hundred kilograms of hydrazine on board down to the DHL counter and ship it to the spaceport. The hazardous aspects of payload processing must be done in a thoroughly professional manner at a facility close to the launch site, and the design of these aspects of payloads must be subjected to design reviews comparable to those currently used for commercial launches. This increases the payload cost, but not the launch cost. It will probably promote the emergence of standard spacecraft buses which provide these components of the payload, which can be serviced for launch for a flat fee by their vendors.
The daily launch rate envisioned here would overwhelm existing ground control facilities. Yet the experience of AMSAT and UOSAT proves that sophisticated and expensive gear isn't required to manage a satellite, at least in LEO. Without access to TDRSS or a global tracking network, most satellites are going to have be very autonomous, communicating with their makers in occasional high-bandwidth gabfests as they pop above the horizon. Since it's very likely that one or more manufacturers will offer a standard satellite bus compatible with the launcher, providing power, communications, etc., perhaps they will also market access to an uplink and downlink as a value-added service. From your nearest ISDN jack or Internet site, you could send and receive packets to your satellite and let the bus vendor worry about how and when they were delivered. Deep space missions are a problem; those who propose them are going to have to obtain time on a big dish as part of their grant proposal. One hopes that if many missions with clear scientific merit are proposed, money might be forthcoming to expand the existing deep space communication facilities.
Who said anything about NASA or the U.S. Congress? A total budget of US$475 million per year is within the reach of many industrialised nations, especially at a time when defence spending is being curtailed, aerospace companies are suffering from excess capacity, engineering and manufacturing people are suffering lay-offs, and policy makers worry about how to convert defence industries without harming readiness by eroding the industrial base. US$475 million per year represents the following percentage of the early 1990's defence budgets (CIA World Factbook 1992) of the following countries:
|Country||% Defence Budget|
Any country whose government became convinced that a scheme like this might give it a long-term (literal) leg up in the world and beyond, eventually, could implement it by reprogramming a small percentage of its existing military spending, much of which would flow right back into its own industries and economy and might be seen to have military value it its own right. For that matter, US$475 million is just about what Microsoft will spend on R&D in fiscal year 1993 and a third of their pre-tax profit, and it's less than 3% of Motorola's sales for the same year, so well-heeled and forward-looking companies (or consortia of such) could play as well.
The near-term development of space is constrained by excessive costs of launching payloads to low Earth orbit. The development of innovative launch technologies is discouraged by an apparent over capacity of existing launchers, “where will the payloads come from?”, while development of payloads for new space applications isn't affordable given current launch costs.
Rocketry was originally developed as a branch of artillery. Proponents of various reusable launch technologies argue that as long as an artillery-like model is maintained, affordable launches will never be possible. But to be effective, artillery must not only have adequate throw-weight, it must also provide a rapid rate of fire while minimising the cost of expended rounds. Today's space launch “artillery” costs tens to hundreds of millions of US$ per shot and fires at intervals measured in weeks or months. Yes, expendable launchers are artillery, and the ones we have today are, as artillery pieces, extremely overpriced and under-performing.
The last time liquid rockets were truly treated as artillery was the very first time they were used in war, the A-4/V-2, fifty years ago. Despite an increasingly desperate war situation, constant supply problems, and aerial bombardment, V-2s were manufactured at rates of up to 800 per month, launched at a comparable pace, and produced at a marginal cost of US$13,000 (1945 dollars) for each additional rocket after the first 5000.
Making allowances for all the differences between Nazi Germany and the modern world, between a not very militarily useful nor reliable weapon and a viable space launcher, between a one-stage Ethanol/LOX missile and a multistage LH2/LOX launcher, between 1945 wartime dollars and current currency, still one must ask why, after 50 years of technological progress and rocket experience, our current rockets cost not five, not ten, not twenty times as much as a V-2, but between one hundred (Pegasus) and two thousand four hundred (Titan III/SRM) times as much. Is what a Delta 6925 does, lobbing 3900 kg into LEO, fundamentally three hundred times more expensive than what a V-2 did fifty years ago?
It is interesting to observe that current launchers are bought and launched in quantities about a thousand times less than those of the V-2 at peak production. In no sense are they mass-produced, and therefore they do not benefit from either the means of mass production (investment in highly-automated manufacturing), nor from the learning curve that results when one builds hundreds and thousands of an identical product. Could it be that a large component of the present unacceptably high launch cost is both cause and effect of the present low rate of launches? That, if we thought the problem through carefully and aimed for a very high launch rate by present standards, we could sustain such a rate with a “standing army” of the present size or smaller, and by spreading that cost over a much larger number of payloads, drastically reduce its impact upon the launch customer.
One sure way to determine whether such a launcher could be developed and operated would be to go the market and attempt to purchase it; if a vendor, presented with a large initial guaranteed order and the expectation of follow-on business and perhaps an expanding market thereafter, developed and supplied a suitable launcher, then launch services could be provided to space scientists and engineers in a quantity and with a frequency few imagine possible today. Commercial launch services could be made available at perhaps a tenth the current cost, putting to the test the proposition that new profitable space applications await only a reduction in launch costs.
Some may fear that success of such a program would merely reinforce the “artillery mentality” of current space launch operations and thereby further defer its evolution into an airline-style transportation system. But, even though I've discussed conventional V-2-descendant expendable rockets exclusively, nothing would prevent a vendor from bidding the launch-a-day contract with an innovative launch technology, so long as it met the payload, cost, launch frequency, environmental, and safety constraints specified in the procurement. Even if a brute-force approach did initially prevail and sparked the emergence of a burgeoning market for launch services, the existence of such a market, previously thought not to exist, could spur the decision to invest in new launch technologies to further reduce cost and expand the market.
Others will argue that there is simply no way an expendable rocket can deliver daily launches at the price suggested herein. But before we spend billions developing technologies which, if they work, might be better but which involve great uncertainties, shouldn't we make sure expendables can't do it? What better way to find out than going out and offering to buy them? If we can, we jumpstart the payload business and start building a market for the next generation of launchers to serve. If we can't, then we've proved that next generation launchers are required to truly open the frontier.