Alan Boyle reports on the work of the Space Development Steering Committee in laying out a lower cost approach to human Mars missions than the current vague NASA plans based on the SLS rocket: Spaceflight experts work on alternate vision for Mars trips – NBC News.com
As Alan mentions, alternatives to the giant rocket approach to space exploration and development have been proposed for years. However, they have not gotten nearly enough exposure and discussion. Congresspersons who lead NASA policy have avoided as best they can to have such ideas presented in public hearings.
United Launch Alliance (ULA) several years ago laid out an architecture for lunar exploration based on the use of their Atlas V and Delta IV launchers. See the Exploration section of the ULA papers collection, which includes, for example, Affordable Exploration Architecture 2009 (pdf). The abstract lays out the problems with the monster rocket approach and the advantages of medium launchers coupled with propellant depots:
The present ESAS architecture [i.e. the Constellation program canceled in 2010] for lunar exploration is dependent on a large launcher. It has been assumed that either the ARES V or something similar [i.e. the SLS], such as the proposed Jupiter “Direct” lifters are mandatory for serious lunar exploration. These launch vehicles require extensive development with costs ranging into the tens of billions of dollars and with first flight likely most of a decade away. In the end they will mimic the Saturn V programmatically: a single-purpose lifter with a single user who must bear all costs. This programmatic structure has not been shown to be effective in the long term. It is characterized by low demonstrated reliability, ballooning costs and a glacial pace of improvements.
The use of smaller, commercial launchers coupled with orbital depots eliminates the need for a large launch vehicle. Much is made of the need for more launches- this is perceived as a detriment. However since 75% of all the mass lifted to low earth orbit is merely propellant with no intrinsic value it represents the optimal cargo for low-cost, strictly commercial launch operations. These commercial launch vehicles, lifting a simple payload to a repeatable location, can be operated on regular, predictable schedules. Relieved of the burden of hauling propellants, the mass of the Altair and Orion vehicles for a lunar mission is very small and can also be easily carried on existing launch vehicles. This strategy leads to high infrastructure utilization, economic production rates, high demonstrated reliability and the lowest possible costs.
(My emphasis.) Competition among commercial launch firms to fill orbital propellant depots will offer redundancy and also encourage lower costs and innovation, especially with respect to reusability. The economics of reusable launch vehicles benefit greatly from the high launch rates that depot filling would generate.
An internal NASA group produced a study in the 2010-2011 time frame that found similar benefits from an exploration architecture based on medium scale launchers and propellant depots but it has never been released.
A group led by Dr. Alan W. Wilhite, Langley Professor of Engineering at Georgia Tech, has published a series of papers on such architectures:
- A Sustainable Evolved Human Space Exploration Architecture Using Commercial Launch and Propellant Depots,
FISO Telecon – Feb.13.13 (pdf, Slide presentation) - Reusable Lunar Transportation Architecture Utilizing Orbital Propellant Depots, Erik Axdahl et al (pdf)
From Wilhite’s FISO presentation:
Rick Boozer‘s book The Plundering of NASA: an Exposé, which I’ve mentioned here several times, discusses these alternative exploration architectures in detail. It’s available at Amazon.
But does this plan maximize payments to companies in the correct Congressional districts?
If not, it’s a non-starter at NASA.
Oh, yea of little faith and keen insight. It would be wonderful if you weren’t so correct.
RS, NASA’s current public-private programs seem designed to achieve relatively low-cost, competitive, commercial cargo and crew and, as far as I can tell, is not based upon maximizing pork for specific districts. So, whereas what you are saying is true for HLVs, there’s a modest window of opportunity to make sustainable progress so long as it is done through the public-private window which is supported by NASA, the Administration, and increasingly, Congress. The key here I think is the next step and that is to apply the success and lessons learned to establishing the next phase which would be for public-private programs BLEO. LunarCOTS.com.
Wilhite’s presentation seems to agree well with my new analysis of the situation from July: http://www.thespacereview.com/article/2330/1
The only small difference I would have with this article is that use of current rockets does not eliminate the need for an HLV, but it does eliminate the need and political pressure for EXPENDABLE HLV’s. All of the propellants and most of the hardware can be launched into LEO using existing or very near term boosters.
However, there are some larger, but not necessarily very heavy components and vehicles that would be far too difficult to assemble in space from smaller parts. To be able to land on Mars and be able, on ascent, to carry enough fuel up as payload to land again, means you need a very wide Ferry vehicle. Georgia Tech studies show up to 15 meters across at the base, while mine is 14 meters, but has only 30 tons of mass dry, and its tanks are only 15% full when landing. This means most of the deceleration is done by passive drag, and less than 1/4 is done by thrusting.
http://www.nss.org/settlement/mars/AccessToMars.pdf
(note that this presentation is 2 years out of date in terms of infrastructure – a Mars mission would now depart from EM-L1, not LEO.)
To launch a 14-15 meter base diameter Mars ferry (shaped like a large capsule) into LEO takes a 10 meter (33 foot) diameter launch vehicle. if such a launch vehicle was built as an expendable booster, it would be useless for this purpose since it would cost too much to launch it 15-20 times in a few years. Only a reusable HLV makes such a program practical and affordable.
So the answer is that we need both reusable boosters and reusable space vehicles to be able to afford Lunar and Mars missions.
John Strickland
Thanks John for the response and the link to your talk. I definitely agree that reusable launch and in-space transportation systems are key to affordable and practical space development.
A HLV like the Falcon Heavy that can be assembled from medium scale reusable vehicles that are highly utilized seems the most sensible way to deal with the occasional too-large-to-fit payload.
Flight rates are what matters. A reusable HLV that doesn’t fly very often will be nearly as expensive as an expendable HLV. I was shocked to hear that Griffin once used the example of ever larger oil tankers as an analogy for super HLVs. Of course, the obvious difference is that super large oil tankers are used continually and easily pay for themselves. A dedicated super HLV cannot pay for itself in any likely near or medium term scenario that I can think of.