It’s time for NASA to abandon the Apollo mission modelby John K. Strickland
|
| In a nutshell, the Apollo Mission model relies on a fully expendable system consisting of a giant expendable rocket, one or two expendable types of crew vehicles, and a focus primarily on science and exploration. |
The new 285-page report on our future in space from the National Academies, titled “Pathways to Exploration” and issued on June 4, has correctly identified some of the technical issues that remain to be fully solved before humans can safely land on Mars. The three issues the report deemed most critical are entry, descent and landing (EDL) for Mars; advanced in-space power and propulsion; and the hearth-related issues of radiation exposure. However, they have ignored several other critical ones, such as cryogenic propellant storage and transfer, use of local materials to support expeditions, and the development of reusable in-space vehicles and robotic in-space construction capabilities. The primary focus on 50-year-old style expendable space transport, and ignorance of logistics, is a flagrant symptom of a continuing reliance on the “Apollo Mission” model in the way that the report’s authors and NASA management think about human space missions. As long as they continue to think about missions this way, the door to the future for, at least the NASA-led space program, will effectively be blocked.
The “Pioneering Space” report issued by NASA in late May has been thoroughly analyzed by Dr. Paul Spudis. His article discusses exactly, and bluntly, what needs to be said about the report, covering a set of characteristics that exemplify the Apollo Mission model. In summary, Spudis says: “this new ‘pathway’ [to Mars, as described in the report] is the very antithesis of space permanence and Earth-independence.” I fully agree with him that the report writers are willing to “talk the talk”, but NASA itself is not willing to “walk the walk”: they use the right buzzwords but propose no matching actions. A quick look through this report reveals a number of such unsupported buzzwords, such as “permanent presence,” “Pioneering,” “Earth Independent,” “sustainability,” and even “infrastructure.” Spudis has continued his analysis with a review of the NRC report. Both articles are well worth reading.
In a nutshell, the Apollo Mission model relies on a fully expendable system consisting of a giant expendable rocket, one or two expendable types of crew vehicles, and a focus primarily on science and exploration. There would be no base construction at any destination, no unmanned cargo vehicles to provide robust material support, no integration to support multiple goals, and no or little involvement with, or support from, the private sector. This is the essence of the “flags and footprints” type of space mission, justly lauded 40 years ago when it was really necessary, but now a major obstacle to progress. Yet in its approach to human Mars and other BLEO missions, NASA seems to support another set of such missions, each to a different destination and none providing support for subsequent missions. As an example, all the officially sanctioned Mars mission models to date have assumed that humans would land on Mars using expendable landers, instead of reusable ferries.
What, then, is the opposite of the Apollo Mission model? It is the concept of a set of continuing missions designed to operate with a set of reusable space vehicles (both for crew and cargo), allowing the creation (and construction) of enduring infrastructure in specific locations in space and at surface destinations beyond low Earth orbit, using local materials, and making each subsequent mission easier, safer, and cheaper. One very critical aspect of this concept is the use of fully reusable spacecraft in an integrated cislunar transport system. Despite its name, such a cislunar system is not focused exclusively on access to the Moon, but to multiple cislunar and other inner solar system destinations. While at least one booster is about one year away from being operationally reusable, almost all spacecraft and other boosters are not, and according to some are in fact prohibited from being reused by NASA.
| Some experts, including the NRC report writers, think that space infrastructure creates a financial drain on the space exploration budget instead of advancing the program, and that to progress to a new program, old ones such as the station must be abandoned. |
A transportation system, whether it is on Manhattan or in space, consists of both transport vehicles and transport infrastructure. What good is a subway if there are no subway stations? By creating a series of space logistics bases—in LEO, at L1 or L2, and another in low Mars orbit—you create not only a set of refuges for crews in case of problems, but you also greatly increase the reliability of mission success by breaking a trip into smaller segments, each of which can be traversed as a round trip by a single stage (reusable) rocket vehicle. (The only trip segment where this cannot be easily done is from the surface to LEO.) The best example of such a round trip is from L1 or L2 to the lunar surface and back again. Using liquid oxygen (LOX) and liquid hydrogen propellants, a ferry of almost any size can deliver a payload equal to its own dry mass to the lunar surface over and over again. An L1 or L2 base is especially important as a safe place to accumulate vehicles, cargo, and propellant, safe from the high space debris impact levels in LEO. The set of bases creates a logistics pyramid, similar to the system of a chain of camps used for decades by Mt. Everest expeditions.
Some experts, including the NRC report writers, think that space infrastructure, such as the existing space station, creates a financial drain on the space exploration budget instead of advancing the program, and that to progress to a new program, old ones such as the station must be abandoned. This dangerous mindset merely continues the thinking of impermanence. Maintaining the station currently costs the US over $2 billion a year. However, if we are to use reusable spacecraft, they must be based, refueled, and maintained at stations or bases of some kind. Logistics capabilities need to be added to the station, or a new LEO logistics base must be built. The further we go away from Earth, the more stations and bases we will need to maintain. Some of these bases can be human-tended and need to be partly self-maintaining.
The NRC report does recognize the need for continued microgravity research, but ignores the need for testing the vehicles and equipment for use beyond LEO. Some kind of a station is also needed to do this. What is also critically needed is research, development, and testing to reduce the amount of money and crew time it takes to operate and maintain habitats and exploration vehicles. Why not use the station we already have for this work? At the moment, funding for such work is not forthcoming due to the same misplaced priorities in Congress and at NASA that have prevented the development of propellant depots. However, in spite of the continuing Congressional disbelief in what amounts to an impending “reusable rocket revolution,” the costs of travel to, and resupply of, space stations and bases of any kind should drop significantly as privately developed reusable boosters come into wider use. This should free up funds for the research work, and will later make building and supporting multiple stations and bases at the same time practical.
Another major aspect of privatization is the increasing reliance on private industry for launch vehicles and, now, spacecraft. The development of the reusable Dragon V2 capsule is a good example. The smaller, more integrated teams working for business, with a focus on reducing costs, can often create a better, cheaper, and more reliable design and get it built faster than a government-led team. Design commonality of components and design integration are hallmarks of many successful industry projects, while a total lack of integration is a common condition of many government programs. The asteroid retrieval proposal is a good example of no integration, where there are no plans to use materials from the retrieved asteroid for crew radiation shielding or asteroid mining tests.
Another sign of up-to-date thinking is the use of robotic cargo spacecraft to carry supplies and cargo for crews on missions. With Apollo-style missions, the only supplies are what the crew has in their capsule. The resupply of the space station by the Dragon, Cygnus, and other vehicles is an embryonic form of this, but only one of the current spacecraft could possibly be reused, and “missions” to the space station are not exploration missions. For real missions to the surface of the Moon or Mars, hundreds to thousands of tons of equipment are needed.
| With its focus on the budget limits, and the prevailing Apollo-style mindset, a major failing of the NRC report is that it assumes the same high launch and operational costs as for the space station and shuttle, pegging the cost of a manned Mars program between 300 and 600 billion dollars and taking until 2060 to even reach Mars once. |
To make delivery of such robust levels of equipment and supplies practical, reusable in-space vehicles are a must. Unfortunately, the absence of references to reusable vehicles is apparent in both of the current reports. The NASA report refers to reusable systems, and storage of cryogenic propellants, but nowhere does it refer to reusable spacecraft or cryogenic propellant depots, along with the critical requirement to be able to transfer the cryogenic propellants from delivery tankers to the depots and from the depots to the vehicles that need fuel. Without perfecting this technology, we will not be able to use cryogenic propellants in any reusable space vehicle. This would force an increase in fuel mass and a decrease in payload mass. Logically, the vast bulk of any Moon or Mars base and its equipment should be delivered by separate robot spacecraft, and not as part of a crew vehicle. Virtually no funding is currently available to advance these technologies.
As Spudis points out, the ability to construct things in space is critical to space development. The use of large external robot arms to do construction and then logistics work in space, such as at logistics bases, is a key component. Some needed structures, like trusses, are “balloon cargo,” too large and bulky to be practically launched from the ground. Concepts for deploying trusses in space were developed decades ago and then abandoned. Exploiting the rapidly developing robotics capabilities will allow us to bypass this balloon cargo problem. Truss construction in space could provide critically needed docking space at the space station. The existing combination of the Canadarm2, Dextre, and the Mobile Transporter on rails is an embryonic form of what is needed, and also what is being underutilized. Up to now, the construction of large structures in space has been very limited due to the enormous launch costs. It took over a decade to build the space station, which has a mass of only about 500 tons. Again, with the advent of reusable boosters, we will soon be able to launch thousands of tons into orbit in a single year. We will want to be able to take advantage of this ability.
NASA’s “Pathways to Exploration” report places some of the blame for current problems on the spending levels available, which have seen NASA’s spending power decline gradually with a flat budget, and with no annual increases to match inflation. Unfortunately, even though any infusion of money would help some, the current level of political control by Congress over how NASA spends its budget would virtually guarantee that most of any additional money would be wasted on pork such as the SLS. What is more critical is that any money that NASA does get be directed into the right areas.
Many of the recommendations in both reports seem more oriented to staying within the budget, rather than innovations that would make much more efficient use of whatever budget existed. With its focus on the budget limits, and the prevailing Apollo-style mindset, a major failing of the NRC report is that the writers assume the same high launch and operational costs as for the space station and shuttle, pegging the cost of a manned Mars program between 300 and 600 billion dollars and taking until 2060 to even reach Mars once. They conclude that without some very unlikely budget increases, such a program is fiscally impossible. The upfront discussion of the huge cost of the entire 40-year-long program, instead of the annual cost, is what killed the original Space Exploration Initiative (SEI) back in 1990. (Some still believe that this tactic was deliberate). Based on the high launch rates and high launch masses that will be possible by the end of this decade, coupled with privatized, semi-mass production of space vehicles, much more capable expeditions, including related lunar operations, should be possible for well under $100 billion.
There is some other questionable thinking in the reports themselves. The NRC report groups the motive to provide a backup copy of humanity and its culture via off-Earth colonies as an “aspirational” rationale and at the same time, groups inspiring students with pragmatic rationales. Most of you know that backing up your computer data is pretty pragmatic, but can we make the mental leap to the concept of backing up humanity itself? The pragmatic, business-oriented people at SpaceX have.
| To succeed with a practical and affordable space exploration and development program, we need clear thinking and carefully chosen goals and methods. We need to free ourselves from the cobwebs of past mindsets such as the Apollo Mission model. |
The same report also points out that “it is not possible to say whether off-Earth settlements could eventually be developed that would outlast human presence on Earth”, without adding similar provisos to the other rationales. At the same time, they assume that comparatively boring trips to the space station will inspire students to study math and science. As is well known, to inspire you must do something that is inspiring. The human survival goal summary makes no mention of planetary defense from asteroid impacts enhancing human survival. Adding human survival (including planetary defense) as a pragmatic goal for NASA would legitimize real space development efforts and tip thinking away from pure Apollo-style (science-only) exploration. The NRC report also focuses on the exploratory “ultimate” goal of Mars, without mentioning the development goals of space materials and energy utilization. Development goals are complementary to exploratory goals, since both need a transportation system to reach the object or location that is to be explored or exploited.
Finally, and most shocking, is this statement from the NRC report: “Any defensible calculation of tangible, quantifiable benefits—spinoff technologies, attraction of talent to scientific careers, scientific knowledge, and so on—is unlikely to ever demonstrate a positive return on the massive investments required by human spaceflight.” This seems to indicate that the report writers have either never heard of the massive benefits of space solar power with its ability to end global warming, and the risks and benefits posed by asteroids, or they have chosen to ignore them.
To succeed with a practical and affordable space exploration and development program, we need clear thinking and carefully chosen goals and methods. We need to free ourselves from the cobwebs of past mindsets such as the Apollo Mission model. Let’s try the cislunar transport model instead. As Paul Spudis points out, “A cislunar transportation system can take us to the planets – to Mars.”
