Chair Force Engineer

Tuesday, November 27, 2007

Engineering a Spacefaring Society

The goal of Project Constellation is to take humanity to the moon, Mars and beyond. That is a noble step on humanity's drive to spread out beyond the earth, explore the universe, and preserve our society beyond the Earth's inevitable death. But it's also clear that there's a massive gap between Constellation's goals (a small moon base and Mars sortie mission) and our eventual goal of spreading out beyond earth. The end-state is what I like to call a "spacefaring society."

In some ways, I think that Project Constellation ignores the technological needs of a spacefaring society in the name of budgetary and schedule expediency. Transportation to the moon and beyond will be achieved with brute-force, by launching large rockets from the earth. But if Constellation is truly a marathon (rather than a sprint,) it should focus on the long-term development of the essential technologies which will enable human exploration of the solar system.

My "technologies for a spacefaring society" list is nothing new. Many of the all-time great visionaries in the space business have said the same things that I'm saying here. Nonetheless, the admission of things that require development is an admission that humanity is not ready to truly leave the cradle for good.

The following is a list of eight technologies that I feel are essential to human exploration of our own solar system. Rather than a "moon-first" focus, I'm beginning to feel that Constellation should be redirected towards developing these technologies before we return to the moon.

1) Space Nuclear Power
Albeit a controversial technology, portable nuclear reactors have the capability to make bases on the moon and Mars sustainable without being hostage to the sun (or Martian weather.) While they would require periodic replenishment from earth, space surface reactors are the way to truly power long-term human bases on other bodies of our solar system.

2) Large-Scale Electric Propulsion
This is not a prerequisite for lunar travel, but they certainly make for a more fuel-efficient cruise to Mars, asteroids or beyond. Current electric thrusters have put out very tiny amounts of thrust. We need much larger thrusters for human interplanetary missions.

While solar power is a possible power source for electric propulsion units, the large array size needed to drive the electric thrusters would make a spacecraft more vulnerable to micrometeoroid impacts. For human missions, nuclear reactors are the preferred power source for driving electric rockets.

Electric propulsion isn't useful for human travel to the moon due to their low thrust. My preferred lunar transport architecture uses nuclear-thermal rockets. Without losing too much thrust over chemical engines, they offer almost twice the specific impulse of hydrogen-oxygen rockets.

3) Artificial Gravity
While we don't understand everything there is to know about long-term exposure to weightlessness, we've seen enough to realize that zero-G is largely detrimental to the human body. We still don't fully understand what rotation rates the human body can tolerate while subjected to an artificial-G system. We also need lightweight materials that can build strong structures for artificial-G spacecraft. An open question is whether it's better to subject a person to a slow, constant spin on a large-diameter wheel spaceship, or if an astronaut could spend short periods of time in a very fast centrifuge to counteract the effects of weightlessness.

4) On-Orbit Fueling
On-Orbit refueling has so much to offer for spacefaring societies. It allows us to launch massive spacecraft from earth into orbit, as long as those craft are launched with empty propellant tanks and refueled on-orbit. Propellant stocks make for cheap payloads and increase the demand for earth-to-orbit transportation.

Beyond their use in earth orbit, propellant depots on the moon and Mars will enable reusable transportation to ferry astronauts between space transportation hubs and the lunar/Martian surface. Whether it's a space station at EML1/2 or on the Moons of Mars, it will serve as a useful staging ground for landings and for inbound or earthbound astronauts.

5) In-Situ Resource Utilization
The ability to make propellant on the moon or Mars will save the expense of launching so much propellant mass into earth orbit. The Sabatier reaction and electrolysis on Mars can produce methane, oxygen, and water by simply using Martian atmosphere combined with hydrogen feedstock. Future missions can make use of water and other substances we find on the moon and Mars.

If astronauts are to survive with little or no resupply from earth, they will need to adopt a "live off the land" philosophy. Just as the pioneers of the American frontier learned how to be resourceful with the things they found in the lands where they settled, so too will the astronauts who settle the moon, Mars and beyond.

6) Closed-Loop Life Support Systems
Unless astronauts can carry massive amounts of consumables with them for long space voyages, they will need to close the life-support loop. Practially everything will need to be recycled. That even means having to find a way to recycle the astronauts' poop. It's a dirty job, but NASA or somebody will need to develop a "biodome" capable of sustaining life with a minimum of mass that will need to be replaced.

7) Aerobraking & aerocapture
The ability to use the atmosphere of Earth or Mars to brake large payloads will save much propellant mass in an earth-Mars transportation system. It's essentially like getting a free ride, as long as we can build heat shields and guidance systems that can make aerobraking effective.

8) Reliable, routine transport to earth orbit
This is a major sticking point for a lot of the space pundits. Many people can't get past the idea that expendible rockets are so wasteful. But it's also true that reusable launchers are more expensive to develop and more expensive to operate. In the current paradigm, the best way to provide human transportation for earth to orbit is with simple, throwaway rockets and simple capsules.

As we build simpler rockets and capsules that can reliably increase the demand and ability to put humans in orbit, we'll get closer to the launch rates that will make reusable rockets cost-effective. It may take 50 or more launches per year to make economic sense of a reusable spacecraft. That day may not come in my lifetime, but it eventually will come.

My current thinking on reusable launchers is that a scramjet-powered first stage would be required for a manned spaceship. It would need an assist from the upper stage's rocket engines for takeoff, but it would then accelerate to Mach 12 (approximately) before releasing its "spaceliner" upper stage. The scramjet-powered mothership would be capable of airliner-like operations, as opposed to the relatively maintenance-intensive upper stage. In the system I envision, there would actually be fewer motherships than spaceliners in order to meet the demand for spaceflights.

Epilogue--Growing Up in the Cradle
As Tsiolkovsky wrote, "Earth is the cradle of mankind, but man cannot remain in the cradle forever." While his words still ring true today, it's clear to me that we are still mere babies in this wide universe. We're trying to stick our hands out of the cradle, but we just don't have the strength to pull ourselves up and out. We will only grow up when we invest time, money, brainpower, willpower, and patience (most importantly) in the tools that will make us strong enough to rise from the cradle.

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Wednesday, November 21, 2007

Delaying the Vision

Depending on the direction the political winds blow in 2008, Project Constellation may face a delay of the political kind. The armchair astronauts have been wrapped up in debating the technical merits of the program, and the political merits are now open to debate as well. (I have argued about the technical merits from the perspective of what's politically acceptable, favoring cheaper development and lifecycle costs in order to make Constellation invulnerable to budget cuts like Apollo was.)

The way Constellation is structured, there are many forms that a potential delay can take. While many pundits have jumped to the conclusion that "Barack is going to extend the US spaceflight gap to 2020," that's not necessarily the case. There are three possible forms that a five-year delay could take:
1. Delay the development of Orion and Ares I. This is the worst option, as it would delay the shuttle's successor to 2020. It would force America to rely on Russia (possibly China and India too) for manned spaceflight, at least until SpaceX can get Dragon working.
2. Develop Orion as planned and delay the development of Ares rockets and lunar hardware. This option would still see the gap extending into 2013-2015, but would fly Orion on the already-developed Delta IV Heavy. A future president would be able to resurrect the lunar program at a later date, although this would appear to be unlikely.
3. Develop Orion and Ares I, while delaying Ares V and lunar hardware. Let's face it: Ares I is neither safe, simple, nor soon. Its major purpose is to justify the early development of the J-2X engine and five-segment SRB's. If Ares V is delayed, at least some of its major elements will already be in production. If a future administration authorizes Ares V and lunar missions, it will "only" require development of the super-transporters, launch pads, servicing structure, EDS, 10m core, and fairing. At least the post-shuttle gap would not grow under this option.

Now that we've talked about delays, let's talk about the way politics and acquisition work in the real world. In a best-case scenario, we're talking about major cost growth on Project Constellation, once the costs of maintaining Constellation facilities, hardware and personnel during the five idle years is factored in.

The most likely scenario is that a politically-imposed delay of more than a year will probably spell the end of the Project Constellation. When Congress delays a program indefinitely, it's simply a more gentle way of killing it. (Just think of the way Milton is fired in Office Space.) The Navalized F-22 was killed in this fashion, as have many other aerospace projects.

The only aerospace project I can think of to survive a politically-mandated, multi-year delay was the B-1 Lancer. In 1977, President Carter terminated the B-1 production contract but still allowed the B-1 test program to proceed. Candidate Reagan used the B-1 as a campaign issue in the 1980 election, and authorized production of the improved B-1B when he became president the following year. Of course, this was the height of the Cold War, and a program such as the B-1 could be justified on national security grounds. If some future president should try to campaign on resurrecting Project Constellation in the 2012 election, he or she probably wouldn't find too many sympathetic ears.

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Sunday, November 18, 2007

Marching to Mars

SpaceWorks Engineering has finally released the AIAA Space 2007 paper and presentation slides on manned flights to Mars. While NASA has focused on getting back to the moon, it's good that somebody is looking ahead to the next step.

The SpaceWorks study makes several assumptions; some are good, while others I feel are invalid. Here's a run-down of the key assumptions which drive the mission design.
--Use of Ares I & Ares V to launch the Mars mission: I think the chances of obtaining full funding for Ares V development are virtually nil in the current political climate. Then again, Ares V reduces the number of launches that need to be performed, which reduces loss-of-mission figures.
--Zero-boil-off systems for cryogenic storage: People I've spoken with on the subject believe that we've gotten pretty good at slowing the boil-off of cryogenic propellants, but we're not at a point where we can say that boil-off can be neglected from our studies.
--Use of aerobraking at Mars: this is a risky technology, but the associated mass savings it enables are enough to justify its development. I'd just like to see NASA make the investment. However, it is noted that SpaceWorks does not utilize aerocapture for the Earth Return Vehicle (ERV) when it arrives at Mars, and I'm wondering why they would choose propulsive capture for this element of their architecture.
--No In-Situ Resource Utilization (ISRU) at Mars: I'd lump ISRU in the same class as aerobraking. It's risky, but it's worth the cost of development. Besides, if we want to establish long-term bases on Mars, we will need ISRU to survive. It's best to develop it now than to leave it off. SpaceWorks neglects it in the study, and pays a mass penalty as a result.
--Chemical propulsion used throughout: the omission of Solar-Electric (ion) or nuclear (thermal or electric) propulsion seriously hinders any mission architecture (through higher mass and lower flexibility,) even though it saves development cost and schedule. I would personally like to see nuclear-thermal or VASIMR propulsion mature before we start sending humans to Mars.
--Surface power provided by Radioisotope Generators: My understanding of the SpaceWorks proposal's ASRG units is that they're essentially RTG's on steroids (using the heat from the radiation source to drive a stirling generator.) But if they are willing to take the political risk of flying radioactive sources on the mission, why not go all the way to a true fission reactor? The development costs of such a fission reactor might be the strike against flying it.
--No artificial gravity provided: This saves on mass and development costs, but I don't think enough is known about how well astronauts will be able to function on Mars after being subjected for 205 days of zero-G on the way to Mars.
--Crew size of three: this is because the study's authors wanted to keep the consumables budget to a minimum. I feel that three crew is too small to handle the workload for the mission. A crew of four to six would result in more science return from the Mars surface mission. To the study's detriment, no consumables budget is provided, so it's impossible to say what the mass impact of adding another crew member would be.

There's a lot I liked about this study, in spite of some assumptions I disagreed with.
--It shows that Ares I&V can support a Mars architecture, using four Ares V's and one Ares I (for crew launch) per mission. Previous NASA reference missions have used six launches of a "Magnum" launcher, with performance slightly less than Jupiter-232. The study counts the Ares V launch as a significant Loss-of-Mission driver, so four Ares V launches are probably more reliable than six Magnum launches.
--The use of drop-tanks on the In-Space Propulsion Stage for the ERV squeezes out more velocity by shedding unused structural mass. I wish the concept was applied to the Trans-Mars injection stage as well.
--Use of existing engines on in-space propulsion stages. The venerable RL-10B-2 is recycled from Delta III & IV to ensure an Isp of 464 seconds on the in-space propulsion stages.

The cost of SpaceWorks's Mars mission will probably make a lot of jaws drop. The plan calls for spending $96.8 Billion dollars between 2025 and 2040 for the first Mars mission. This figure is quoted in FY2007 dollars. It does seem reasonable when compared with a previous NASA estimate of $50 Billion, in FY 1993 dollars. While the costs are spread out, the inevitable sticker shock is going to motivate the plan's political opponents. It's worth noting that over 10% of the life cycle costs are associated with the rigid surface habitat, and I wonder if this cost can be slashed by adapting the TransHab inflatable technology for this application (it's being used anyway for the deep-space legs of the SpaceWorks Mars mission.)

More striking than the budget is the risk associated with the mission. There's a 38.5% chance the mission will be lost, and an 11.5% chance the crew will be lost on each Mars expedition (these numbers are given with 50% confidence.) While NASA will have no problem finding astronauts willing to fly in such conditions, will the American taxpayers be willing to fund such a risky venture?

Anyways, I'd highly recommend a read of the SpaceWorks study to all of this blog's readers. It's definitely worth wrapping your brain around, and it should serve as a starting point for future Mars planning.

Monday, November 12, 2007

Blind Ambition and Heavy Landers

When NASA performed its 2005 trade studies for the lunar mission, it assumed a crew of four astronauts would spend seven days on the lunar surface. I have not seen any justifications for this requirement, and I must say that it seems very arbitrary. Nonetheless, the lunar crew and duration requirements are having serious impacts on Project Constellation.

During Project Apollo, the Lunar Module weighed in at approximately 15 metric tons, and the Apollo CSM was roughly 30 metric tons. The Lunar Module was designed for little more than six man-days (two crew for three days.) Project Constellation reverses the paradigm: the Orion CSM is around 22 metric tons, while the LSAM is budgeted for 47 metric tons. The LSAM will support 28 man-days of lunar surface operations (four crew for seven days.) The LSAM is also expected to perform the lunar orbit insertion burn, which was performed by the Apollo CSM the first time around. (If the Orion CSM performed the LOI burn, it's likely that it would be too heavy to fit on the Ares I launcher.)

The problem with the current scenario is that LSAM is outgrowing its 47 mT budget, around which the Ares V and EDS were designed. One of the figures I've heard was a 55 mT LSAM, although I haven't seen enough evidence to confirm. In any case, NASA may be forced to slim down the LSAM by reducing the crew size, the mission duration, or both.

In a larger sense, we should probably be asking whether the mission requirements for Project Constellation are a bridge too far. NASA expects all the provisions for a long-duration lunar stay to arrive with the LSAM on a single Ares V. But Project Apollo, had it continued, would have relied on vehicles like the LM Shelter and LM Truck to extend the basic capabilities of the Apollo LM. Each of these vehicles would be delivered by an additional Saturn V launch.

A good analogy for the situation is that LSAM is a Winnebago, while the Apollo LM was a compact car. While you can't live out of the compact car for a significant period of time, you can always have a second sports car drive out and deliver a tent, food, and provisions for a longer stay. Having the Winnebago might be convenient, but the upfront costs are steep. NASA is re-learning this lesson the hard way. One one step, we are trying to eclipse Apollo. It might make more sense to duplicate Apollo, then build upon it in subsequent spirals.

Tuesday, November 06, 2007

Say It Isn't So

If all goes according to plan, NASA will soon re-award roughly $175 mil that was originally supposed to fund Rocketplane-Kistler's COTS entry. The loss of this contract is likely to leave RpK in dire financial straits.

On the flip side of the coin, Jeff Foust reports that RpK is redesigning its XP space tourism vehicle to make it more competitive in the suborbital marketplace. The logic behind the change is sound. But the fact that RpK could make that change indicates to me that they were never as far along in the development of XP as they publicly claimed. I haven't seen much info on the engine that the team plans on using (which is allegedly based on the old Atlas sustainer.) It's also been stated that many of the team's personnel, like the legendary David Urie, have been released due to the company's focus on keeping the COTS program alive.

It's been pointed out that, during the late 90's, the Kistler K-1 essentially killed the original Rocketplane (the Pioneer Pathfinder) by winning a key investment by Northrop Grumman. Ironically, the Rocketplane company and its current rocketplane may be killed by their acquisition of the Kistler albatross.

RpK is currently fighting tooth-and-nail with legal appealsl, hoping that NASA will reconsider its decision to re-award the COTS contract. I don't blame the company, but I think a smarter way ahead would be to drop K-1 entirely and try to turn a profit with XP. The K-1 hardware could be sold, although I'm not completely certain who'd be interested in buying it. Orbital Sciences might be interested in buying the NK-33 engines that RpK owns, for use on their upcoming "Taurus II" rocket (hopefully there will be a better name for it soon.)

At one time, I was very enthusiastic about the K-1 concept. By now I realize the the project has been a costly money-pit. I look at the "Launch Assist Platform" first stage and realize that the propulsive return to the launch site is a waste of propellant mass. While the lessons of K-1 could eventually help RpK to build a smaller reusable spacecraft (utilizing a rocketplane first stage and a ballistic second stage,) it has become an albatross that weighed down and sank a once-promising newspace firm.

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Sunday, November 04, 2007

The Long March to a Chinese EELV

Last week, the China Academy of Launch Vehicle Technology (CALT) announced that its Long March 5 family of rockets will make its maiden flight in 2013. The Long March 5 family is roughly equivalent to America's Atlas V and Delta IV, or Russia's Angara family.

The proponents of the belief that China will beat the US to the moon generally don't address the long pole in the tent for a Chinese lunar mission: the launch vehicle. The current Long March 2 relies on the same hypergolic propulsion technologies as the old Titan II, and has similar performance to Soyuz (and the base variants of the EELV's.) In order to fly to the moon, China's propulsion technology will have to take "one giant leap" forward.

A new family of EELV-class rockets is important to China's future space ambitions, but it's still a long ways away from a manned lunar capability. While China hasn't made any comments in this direction, I would suspect that the first Long March 5, in 2013, will be similar in performance to the baseline Delta IV Medium or Atlas V 401. It took two years for the US to progress from the first baseline EELV flight to the first Heavy EELV flight, and I would suspect that the same would be true for China. So let's assume that, by 2015, China has a launcher that can put 25 metric tons in low earth orbit. That's still a far cry from a lunar-capable booster that can put 100+ metric tons in low earth orbit.

Even if China works all the bugs out of the new boosters by 2015, it's still an open question of how they will be used. The heaviest version of the Long March 5 could be used to launch space station modules, but it could also be used to launch two satellites to geosynchronous orbit. (Given the commercial viability of Chinese launchers, I think the latter is more likely.) The 3.35-meter version of the Long March 5 could replace the Long March 2F for manned Shenzhou launches, but there are no publicized plans to do so.

Long March 5 will be launched from Wenchang Space Center on Hainan Island. The choice of launch site is highly advantageous. It will have a sea port that will accept the barges which carry Long March 5 booster cores. It's close to the equator, which will allow for more payload to orbit. I would also suspect that it will allow for highly-inlined orbits by launching to the southeast (a launch to the southwest would carry the launch vehicle over Southeast Asia, so it looks unlikely.)

In short, the Long March 5 family of launchers is a major step forward for China's space program. However, it's unlikely that the Long March 5 program will enable manned lunar landings, and it's uncertain at this point what role (if any) it will play in China's manned space plans.

Thursday, November 01, 2007

2009: A Space Oddity

In the course of every struggle, a turning point emerges. NASA is currently struggling to implement its Vision for Space Exploration, in the face of three major adversaries. The first is a Congress that is hostile towards anything that's associated with the current president. The second is a growing realization amongst the technical community of how flawed the Griffin-Horowitz approach really is. The third is a groundswell of space enthusiasts who oppose the Griffin-Horowitz plan based on its vulnerability to the first two challenges I mentioned.

The pivotal year for the Vision for Space Exploration will be 2009. This is because of two interrelated events: the inauguration of a new administration, and the first launch of Project Constellation.

Michael Griffin's strategy all along has been to use Ares I as a "stick in the doorway" to keep the door open on the rest of his lunar architecture. As long as Ares I is politically immune from cancellation by the time the new administration rolls into D.C., the rest of Constellation should be safe. I find that logic flawed, as Ares V and the Lunar Surface Access Module require significant development that will not occur until well into the next administration.

The problem with the "stick in the doorway" plan is that Ares I will not go operational until 2015, meaning that it will have to survive the entire first term of the first post-Bush president. So Mike Griffin needs a second "stick in the doorway." That's where Ares I-X comes in.

Ares I-X uses a stock SRB from the shuttle, plus a dummy fourth segment, a dummy upper stage, and a dummy spacecraft. The avionics are coming from the Atlas V. So it has to be asked: what relevance does Ares I-X have towards the real Ares I? The answer is both "nothing" and "everything."

From a technical standpoint, the Ares I-X test has little or no relevance towards the real Ares I. With that established, it should be noted that Congress and the Executive Branch probably won't be able to tell the difference. The relevance of testing makes no difference to the budgetmakers, the White House, or the Congress. As long as a test is bold and flashy and makes good headlines, the money will keep on flowing.

The 2009 date for Ares I-X is based on the availability of LC-39B and the inauguration of the next president. The test will be carried out before the new administration can decide on a new space policy. If the test succeeds, the money to continue Ares I will follow.

At the same time, Michael Griffin and his supporters have to ask what will happen if Ares I-X should fail for some reason. I refer to this as the "bloody glove" moment for NASA. It's much like the OJ Simpson trial, where the prosecution had little to gain if OJ fit into the bloody glove, and much to lose if he didn't. If Ares I-X fails, you can say goodbye to the moon. NASA will scramble to close the post-shuttle gap, and it will do so by clearing house of the Griffin people, then mating Orion to a Delta IV Heavy for ISS missions. The shuttle program may even be extended, because Delta IV will not meet Congress's goal of retaining the shuttle workforce.

At the current state of the program, NASA has gone fairly far down the path towards getting Ares I to a level of progress where Congress cannot cancel it. It will be farther down that path by 2009, owing to Michael Griffin's unwavering support for the Ares launchers. The only thing I can see forcing Griffin to change directions is a major technical roadblock on Ares I. I mean, NASA is already gutting the safety features on Orion just to make it light enough to fly on Ares I.

Griffin will have probably left office when Ares I-X flies, having previously indicated that he would leave along with the rest of the Bush Administration. The messy aftermath of a possible flight test failure will be left to his successor. Even if Ares I works, the aftermath will still be messy if the rest of the lunar program is cancelled by the Congress and President we elect in November 2008. Thus, 2009 will be the crucial year for the Constellation Program. I'd hate to be the man appointed to run NASA in the wake of Michael Griffin.