There have been many comments over the years on many sites about cost plus being used when nobody has any idea of the costs of a project or how to bid it. This morning on Clark’s site spacetransportnews.com he linked to an article claiming that getting bids was so uncertain that contractors would bid 50% higher than it would run to do the same project cost plus to make sure they didn’t lose money. That is an interesting claim. Cost plus is noted for budget over runs while straight bids, honestly enforced, cannot over run as the contractor wouldn’t get paid.

Considering the Constellation mess, wouldn’t it possibly have been cheaper back in 2005 to put the project out for bid? With the current projection of $35B to complete Ares, 50% more would have been a $52.5B  bid. If there was that much money on a fixed price contract, how many companies would have been willing to bid on the expectation of making a large profit? How much would they have been willing to cut to get the bid? This is when someone usually points out that there are only one or two companies qualified to bid on such a system. That should be a red flag. If you are specing a system with too few qualified bidders, then you are overspecing more often than not.

Cost plus seems to have a fairly low percentage of profit or even a fixed profit in the contract and requires extensive oversight to keep the contractors honest. I question whether the mandated low percentage itself eliminates potential contractors. Who wants to do a contract with a limit on potential profits when there is other work with much higher margins except the one or the few companies that are set up to do the insane paperwork and deal with the oversight? I think the profit limits in the name of taxpayer cost control end up costing far more than letting companies make higher profits or take their losses. If there were a half dozen or so companies bidding on the Ares, don’t you think it possible that some of them would think they could do the job for far less than $52.5B, or even $35B?

There are companies that are just better at cost control than others just as some people are smarter than others. I don’t think it is out of line to suggest that some companies can execute a rocket project for half of the cost of a competitor. If one qualified company bids $10.00 on a widget and another bids $9.00, go with the lower bid, and don’t pay if they don’t produce. Then if the second company has costs half that of the first, then they spend $4.50 in costs while the first spends $9.00. The second company has profits of 50% of income while the first has 10%. The government attitude seems to be that since this is taxpayer money, excessive profits are harmful to the taxpayer. With this attitude, the more expensive company has the edge since they will make twice as much profit as the better managed one at the same percentage.

If government contracting would quit worrying so much about how much profit a company makes, and start worrying about what is being delivered for the dollar, more companies would try for the contracts. A possible contract with 25-50% profit potential will attract more players. As more players enter a field, some will have better people or ideas which translates to lower costs, which becomes lower bids. When faced with real competition, Lockheed and Boeing can both find cost saving options when it is in their best interest to do so and they can make higher profit margins doing it.

In the long run, competition will cut into the possible profit potential and the end result will be a percentage similar to that mandated in cost plus except on a far lower total price. Financial oversight can be vastly reduced for further savings.

One objection many make is about quality when a simple low bid is the criteria. They believe that low cost is low quality. This has been demonstrated to be false anytime there is a competent purchasing agent involved. If the product doesn’t perform, don’t pay.

Another thing brought up all the time is dishonest contractors when there is no oversight, with the assumption that most contractors will cheat when no one is looking. Thomas Matula says that this is why the government must have a ten page spec for an ashtray. From rotten food to weapons that don’t work to vehicles that don’t run, he suggests that every single one of those specs is required due to suppliers cheating at one time or another. I believe this is a  poorly thought out objection. Every single time one of those suppliers cheated, there was a government official not doing his job of confirming an acceptable delivery. It is a matter of historical record that much of the time the particular official was corrupt. You want honest delivery, write a simple spec and have one (1) official responsible for the proper delivery. Responsible includes prison for corruption, which he can share with this supplier.

Many of us have complained from time to time about the lack of true progress from NASA even while agreeing that there are a lot of very smart motivated people in the agency. It would be useful if some way could be found to use the capabilities of those skilled  people without the anchor of bureaucracy holding them back. It is even more difficult considering the role congress plays in controlling the outcome of funding for the different stakeholders.

I wonder if it could be made possible to provide incentives to the people that can produce, while simultaneously preventing the bureaucrats in the agency from interfering with the producers. I suggest a thought experiment for increasing agency performance in a politically acceptable manner, while reducing long term costs. This is just a first cut for the Halibut.

List a series of projects internal to the agency for employees to bid on. A condition of the bid is that successful completion of the project ahead of time and budget qualifies the participating employees for full retirement effective immediately after the demonstration of success. Incentive also is that 10% of the funds remaining from being under budget is split among the participating employees. Failure to complete on time and budget is immediate layoff from the agency.

Other NASA employees have no oversight role for these cheetah teams. If the team leader and his group are good though, they will get the support of many of the theoretically uninvolved to help accomplish the project, even though they will not be eligible for the retirement package.

A project might be a multipropellant depot in LEO. It must accept LOX and fuel from at least two vehicle types and dispense the propellants to a different vehicle type after storing it for at least two months. Time limit three years and bid cap at three billion including projected retirement payments.

 Whichever group gets the bid will increase spending in a congressional district through at least one election cycle and possibly two. With congressmen on the bid review board, it seems likely that they will be going for the infusion of near term pork and will worry about the following elections later. The bidding NASA teams will be aware of this and will dutifully spread the pork as far as they need to to get the congressmen on their side.

A bid might be a team leader and a couple of hundred other NASA employees bidding $2.6B and 32 months. If they succeed on time and for $2.1B, they split $50M two hundred ways by whatever formula they agreed to among themselves and retire early with full benefits. The depot is in orbit and operational and two hundred people with a performance track record are available to the private sector if they choose to keep working. Also $850M less than the original cap could be available for the follow on projects.

The retirement incentive is center to the strategy. After slamming a project through with little time for the agency drone workers, the project members will need to get out as too many toes will have been stepped on for them to be part of the clique again. The termination for failure is the stick to balance the carrots.

An F1 class kerosene engine might be another project with a functioning rotovator for a different group.

A suitably motivated group could have had Ares I flying by now, or if none would bid it would have been understood that it was a turkey five years ago. Either there would be working hardware, or the money wouldn’t get spent.

If there is a project that none would bid on, as seems possible for the Ares, then it is understood that the agency is not capable of that task. That would be a clear signal that the ‘experts’ in that field were not up to the job and would run the risk of losing whole departments that couldn’t get results in their field. The agency would need to get teams to produce with failure to do so carrying real penalties. Employees wouldn’t sign on to a project to be sacrificial goats to the bureaucrats and drones, so the bureaucrats and drones would need to support the teams in their own best interest.

With the truly productive getting projects and getting out, the agency drones would run out of workers to hide behind and could then be dismissed as excessive to the requirements of the agency. The congressmen gaining from the project pork would possibly support getting rid of people not getting them as much return in favor of the high profile projects they brought home. The high profile projects could get them more votes than the standing armies for this election, and the next one could be worried about later.

There is a fairly constant murmur that commercial space will not go beyond LEO and more mumbling that there must be a specific destination with a specific timeline.

The second mumbling assumes that there is some top down command structure that will make one thing happen regardless of obstacles or opportunities along the way. Goals for the short term are often good, but not so much for the uncertain future. It is roughly the difference between getting married or staying single. When you get married, it better be the right one, and all the other options better be off the table. A single goal and time frame assumes that no other goal is worthwhile, and that nothing will ever change the relative values.

The murmur about commercial not going beyond LEO is often from people that haven’t considered the implications of CATS. For this post, I suggest that CATS is $1K per kilogram to LEO and work out a few costs that apparently haven’t been considered openly enough. I also suggest that RLVs are giving launch on demand in order to hit that price point.

Say someone wants to send a small commercial robot probe to a NEO. Current state of the art might be a one ton spacecraft with a mass ratio of three to go from LEO to the object. At $10K per kilogram for launch costs, $30M. The way it is currently done, perhaps $50M for the vehicle itself and another few million for operations. So $85-90M for one data set. From program start to launch could easily be from three to five years, plus looking for funding and operating the vehicle almost as an afterthought. It would be easy to burn a decade on the program, and well over $100M considering the time value of money.

With CATS and launch on demand, other methods become attractive. If it is allowed to triple the mass of the probe and use less efficient engines, a three ton vehicle with nine tones of propellant becomes 12 tons IMLEO instead of 3 currently, though launch costs drop from $30M with a long lead time to $12M whenever you get ready to go. With relaxed mass constraints developing the probe becomes a construction project rather than research and development. Shield modern electronics with mass rather than use expensive antiques that are space rated. It seems possible that the three ton probe could drop to $1,000.00 per kilogram in construction costs, for a total of $3M in hardware costs. Lead time could drop to a few months with relaxed hardware mass restrictions. Engineers could spec a 7mm bolt from COTS suppliers rather than spend the time and money to determine that a 6.26mm bolt gives the exact safety margin required.

If CATS makes it possible to send a NEO probe within three months of decision for a total cost of  $15M, that is a time frame and cost that fits into a quarterly stockholders report. Pick your favorite reason to go, and it is quite possible that there is a millionaire out there that will agree with you. Minerals, volatiles, SPS materials, or just to see what is there become affordable to many thousands of interested people. At that price point, hundreds of probes per decade would certainly fly.

Many many people will point out that a three ton probe is way too much craft for early prospecting. Some people will certainly agree that 10 kg of fairly sophisticated instruments could be quite capable and not even be all that expensive if they didn’t have to support a decade program and could avoid a lot of that helpful oversight. 10 kg of instruments in a 40 kg vehicle with an IMLEO of 200 kg including propellant would drop the launch costs to $200k. Instruments and hardware by the right people might double that total cost. With a total of $400k per flight, commercial and private players would launch them by the thousands. I think it would be safe to suggest that known NEOs, the moon, Mars, Venus, Mercury, and most of the asteroid belt would be explored for a fraction of today’s government exploration budgets.

There are some that would try to do probes with a 1 kg cube sat, While I’m skeptical, CATS would make it possible for them to prove me wrong for around $10k.

I personally am more interested in the effects on human spaceflight. With $1,000.00kg for launch costs, a person’s direct mass cost to LEO would be around $100k. A reasonable overhead for life support and supplies would bring it to perhaps $500k for a several week visit. A true CATS launch on demand would let people go during a month vacation. Bigalow would have to get busy building stations and hotels to accommodate the customers that could and would  go at that price point.  There is a laundry list of experiments that companies and governments would do if their orbital workers could do a three month LEO  tour for under a million. An EVA worker cost would drop to a couple of thousand dollars an hour under these conditions.

What about beyond LEO? A five ton vehicle could certainly shuttle from LEO to LLO and back with four people. Flying the same vehicle repeatedly with four people and supplies would require about twelve tons of propellant and provisions per trip. Twelve tons of supplies is about $12M in launch costs and about $6,346.50 for the actual supplies. Circumnavigating the moon for under $4M per person including launch costs and LEO accommodations is considerably less than anything currently planned and should be proportionately more attractive to customers.

If the vehicle has entered LLO, then a modest craft can single stage from there to the surface and back. Propellant costs would bring the whole adventure to about $8M per person for the round trip from Earth’s surface to a moon base and back. Additional time on the surface is simply a matter of supplies. At $10k per kilogram on the Lunar surface, a person could stretch their stay by about three weeks per million dollars. It is a fairly safe bet that many people will go, and some of them will go for profit as they look for something they think valuable to some market. Anyone that can create more than 5 kg per day in resources from the local materials can stretch their stay almost indefinitely.

For some, it’s Mars or nothing. There is no reason they can’t get to Mars while everybody else exploits the nothing they disdain. Think of a ship of a thousand tons for their comfortable journey to Mars that takes ten thousand man hours of EVA to assemble and needs three thousand tons of propellant for the trip. What would that cost? At $1K per kg for the ship mass, $1B for construction. $4B for launch cost. $20M for EVA labor costs. Total costs for a thousand ton ship on Mars trajectory, $5.02B plus tax, tag, and title.

Quit yammering about commercial stopping in LEO. If commercial creates CATS, the rest follows.

What if games can be quite entertaining even if not practical. This particular one is what if Griffen had dictated an RS-68 for the Ares? It is existing and has considerably more thrust than the J2S, which would seem to imply a more capable second stage with considerably more payload to orbit.

Second glance is where the problems and fun start. A fifth segment was already required for the Ares I first stage even with the available thrust of the J2S, so the SRB would seem to be even more inadequate to support an RS-68 upper stage. Unless you parallel stage to get enough take off thrust, but then you are stuck with a clumsy layout and a sea level  nozzle on the upper stage. Serial stage seemed to be a requirement. Using a pair of stock SRBs would provide enough performance to lift a large upper stage compatible with an RS-68 fitted with a vacuum optimum expansion nozzle, but that would have been a different game altogether.

This what if idea comes from another direction. What if the gas generator cycle RS-68 pumped it’s propellants into the SRB to increase it’s thrust as much as adding another segment only without adding the mass and development of that segment? The gas generator cycle presumably can send propellants through a pipe without concern as to where they are actually used. So the plumbing for the upper stage has two flow paths for the propellant down stream of the pumps. One goes to the first stage  SRB to boost thrust and ISP, while the other path goes to the RS-68 thrust chamber as second stage propulsion.

With the hundred foot L* of the SRB and the rough and tumble combustion of the solid, it would seem that there would be no problem with mixing and burning even with minimal injector capability. A dozen or so ports of inches in diameter should be sufficient. The effective sea level Isp of the virtual RS-68 should even be higher than a stock version as found on the Delta IV because the expansion ratio would be less and the exhaust temperatures higher due to the much higher temperatures of the solid combustion products. The H2/O2 combustion would actually lower the temperature of the solid rocket exhaust though which would drop that effective Isp some. The net Isp effect would seem to be similar to a stock SRB parallel staged with a stock RS-68. The total thrust and Isp would seem to be a bit higher than the five segment SRB while being much lighter.

Testing could be by bolting an H2/O2 propellant supply to a stock SRB at ATK’s static test stand. It shouldn’t be more expensive or time consuming that the five segment development. It would also test a possible command throttle capability.

If this could be made to work, it would put a ~700,000 pound upper stage at roughly the same altitude and velocity as the Shuttle stack at SRB burnout. A very high expansion ratio RS-68 should get an Isp considerably higher than a stock engine, possibly approaching RL-10 performance. Various assumptions give a mass ratio of 4 to 5 for the rest of the way to orbit. If this different Ares I placed 140,000 to 175,000 pounds in LEO, then effective payload should be in the 30-40 ton class even with the extra tankage supporting the first stage burn.

Properly handled, this would seem to be a better, faster, cheaper way to get a strong medium lift. We all know better, which is why this is just a what if post for fun. Unless the concept itself is viable and can be applied to other vehicles later on.

As near as I could tell, after Columbia happened, nobody kept working on the AG-NEP design, or even on Mars studies for that matter. If they did, I certainly didn’t know about it.

But for some reason, the whole idea kept rattling around in the back of my head. There were a few reasons that the JSC guys had given me that were compelling for AG-NEP as a Mars vehicle.

1. You solve the muscle and bone loss problem through artificial gravity. You don’t have to worry about hours of exercise or fret whether their bones will snap when they re-enter the Earth’s atmosphere. They’re going to be good and strong when they get home because you made sure that their bodies felt a normal level of gravity throughout the trip.

1a. Because you’ve solved the muscle and bone loss problem, the pressing need to fly the mission quickly is tremendously diminished. You can go to Mars and come back in the three-year time frame that is more astrodynamically “natural”, in other words, the time frame that aligns with the Earth and Mars’s movements around the Sun.

2. By using nuclear-electric propulsion, you actually have a credible propulsion system to execute a mission abort if you need to, for some reason along the way. You’re not going to get back quickly, but you can get back.

3. By using nuclear-electric propulsion, you actually have a credible story for vehicle reuse. You could refuel the vehicle and go again. Or you could go somewhere else like an asteroid. You have a lot more flexibility than in a chemical or NTR vehicle.

I liked the basic idea. Here was a vehicle that might actually be a true “spacecraft” as we like to think of them, with the ability to go and come from a variety of destinations and be reused. I imagined that this might be the kind of vehicle that would be in Captain Picard’s ready-room a few centuries from now as a little model, with him saying, “This is a model of the vehicle man used to explore the solar system in the early days.”

But there were definitely residual technical problems with the design as it stood when I was exposed to it. The biggest one had to do with getting the body-mounted electric thrusters to point in the right direction as the vehicle moved around the Sun, and the problem got so bad when you got to a spiral-in, spiral-out scenario around a planet that it was practically a no-go. It came down to the architectural decision to orient the thrusters so that they were firing in the same direction as the vehicle’s angular momentum vector (orthogonal to the rotation plane). That approach certainly solved any problem of plume impingement, but since the inertial direction of the thrust vector was going to change by >180 degrees during the transit to Mars, and by that much or more on the way back, you had to continuously move the angular momentum vector of your spacecraft around, and there was a non-trivial cost associated with doing that. During spiral-in or spiral-out the cost became prohibitive.

The other problem concerned spin up and spin down of the system. The JSC design assumed that spinup and spindown would be done by dedicated thrusters on the habitat module end of the vehicle. That meant a duplication in thrusters and tankage for a capability that you would want to utilize as little as possible.

Despite these problems, I recognized that the JSC design as it stood had also solved a great many problems, and that perhaps it represented a minimum in the design space of overall difficulty. I’m fond of saying “you have to pick your pain” when it comes to system optimization, and that the “best” system always involves residual problems. Perhaps this was as good as it got.

Or maybe it could be even better.

One day I was driving down the street in the pouring rain and a simple sequence of thoughts formed in my brain:

1. I had spent a whole bunch of time trying to figure out how to get solar panels on a MXER tether to point at the Sun while the tether rotated.

2. I had been lucky enough to meet Steve Canfield and had figured out how to use the Canfield joint to fix the problem of pointing the panels at an inertial target (the Sun) while the overall structure (the tether) rotated.

3. The basic problem that the AG-NEP vehicle faced was the need to point its electric thrusters at an inertial target (its thrust vector) while it rotated, much like the MXER tether needed to do with its solar arrays.

4. The reasons that JSC had rejected rotating machinery for the AG-NEP vehicle had to do with the difficulty of moving propellant and electric power across a rotating connection like a rotary joint or slip ring, and these were good and valid reasons.

5. The Canfield joint had no such problems because provided that propellant lines or power cables were flexible, they could transmit fluids and power across a Canfield joint.

thus…maybe a Canfield joint was the answer to the problems of the AG-NEP vehicle!

I couldn’t believe that I had known about the Canfield joint for so long and hadn’t put these utterly compatible ideas together.

If we were to use the Canfield joint on the AG-NEP vehicle, the overall geometry would change substantially. The logical location for the thrusters moved from the center of the vehicle, on a cross-brace, to the reactor end of the vehicle. This kept the high-power lines short since they didn’t have to run all the way to the middle of the vehicle to reach the engines. You could also place the propellant tanks on the reactor end of the vehicle as well.

This in turn led to several other vehicle advantages:

1. The moment-arm from the reactor module to the hab module is shortened (or alternatively the moment arm from the CM to the hab module can be lengthened) because now there is much more mass counterbalancing the hab module. The thrusters and the propellant constitute a lot of mass.

2. The truss between the reactor module and the hab module now doesn’t need any “cross-brace” on it or any other body-mounted structures. It can be a strong but simple extensible structure, like a CoilABLE boom, with nothing more than the power connection between the reactor and the hab module integrated into it.

3. The main thrusters can be used for spin up and spindown operations. By placing them on the end of the moment arm, they now have the ability to change the angular momentum of the vehicle, by simply remaining fixed relative to the vehicle during spinup and spindown. In fact, spin rate can be changed during thrusting simply by changing the fraction of the spin arc during which the thrusters fire.

4. The angular momentum vector of the vehicle doesn’t have to point along the thrust vector (like in the JSC design) but can point orthogonal to the spacecraft’s orbital plane. This means that the angular momentum vector’s direction doesn’t have to be altered during flight. This also means that spiral-in/spiral-out maneuvers at planets are no problem.

5. If you wanted to use the AG-NEP vehicle for asteroid missions, the electric thrusters might even be able to be used as “descent engines” provided some “landing gear” were provided on the habitat module.

6. Propellant could be used for additional reactor shielding during the flight.

Over the years since this realization, I’ve developed the capability to show how such a vehicle might look as it rotates. Here’s the link to a Java code that will show the vehicle rotating along with the Canfield joints. You can click and drag to rotate the view around and zoom in and out with the mouse wheel.

For reference, here’s the original set of slides from JSC describing the problem and their original design solution.

My writings have elicited strong responses, both here and over on the NSF forum. People have asserted that I am simply wrong, or that I have gone into the analysis with a bias that has somehow compromised my results, or that I have ignored some obscure advanced version of an NTR that they assert can solve the problems that I have identified. Of these criticisms, it is the criticism that my bias compromises my results that troubles me the most. As an engineer, we want to believe that we are immune to opinions and biases but my experience has been that that is not the case at all. They creep into our judgement, and sometimes they sit flat on our face. I have seen for years now at NASA how even the most clever engineers can be seduced or bullied into accepting terrible vehicle designs, and in a perversion of the Stockholm Syndrome, eventually come to “love” the fatally-flawed design that they would have initially rejected.

I cannot be certain that my biases do not affect my work, but I am always striving to reduce them as much as possible. The most effective way I have found to do this is to get to “the numbers” as quickly as possible. We can talk all day long about how much better this technology is than that technology, but when we get to the numbers we can begin to improve the signal-to-noise ratio of our discussions more quickly than anything else I know.

Let me tell a story about a time when my opinion was changed significantly through solid engineering analysis. When I first got to NASA in 2000, I was part of a study called by a number of different names. Some called it “Decadal Planning”. I thought of it as “go to Mars and back in a year”. Within a few months of getting there, I was running a part of the study looking at propulsion technologies, and we were comparing a number of them. I met a lot of people in the field and began to develop a distaste for nuclear electric propulsion (NEP). The study concluded quietly and in my opinion, was a failure. Some of that was my own fault. But that’s some other post.

Near the end of 2002, my boss asked me to be a part of an MSFC response to a JSC study on a new and different NEP vehicle. As I recall they were interested in launch vehicle options. So in January 2003 several of us went to JSC to talk to them. I was very impressed by what they had done.

Essentially, they had asked “what are the big barriers towards sending people to Mars?” and then “how do we deal with them?” The biggest barrier they had identified was uncertainty about what happens to people after many years in microgravity. So they decided from the outset to design a vehicle that incorporates artificial gravity, thus cutting the “gordian knot” that had driven previous mission planners to “fast” trip times. My own experience on the one-year-round-trip Mars study had convinced me that it was utterly foolhardy to try to go to Mars and back too quickly. But I know the idea still rattles around in the Internet and is carried by the astrodynamically misinformed.

To accomplish the artificial gravity approach, the JSC study anticipated using the natural countermass of the nuclear reactor that would power the NEP vehicle to counterbalance the mass of the inflatable crew habitat. The boom that would be present anyway to keep the reactor away from the crew would now double as the separator needed for artificial gravity. Any time you can get a “two-for-one” value like that in space vehicle design, you want to take it.

The persistent problem in the design was the need to point the engines along an inertial direction while the vehicle was rotating. The JSC planners had rejected the idea of rotating slip or roll rings, for good reason and based on their experience with the ISS. To keep the engines body-mounted and yet pointing along an inertial direction required rotating the vehicle in inertial space, nearly 180 degrees during the transit to Mars. Once they got to Mars, the “spiral-in” proved very difficult, since now they would need to move the rotation axis of the vehicle through 360 degrees on every orbit. They came up with a compromise, called “minor-axis rotation” that mitigated some of the issues associated with this maneuver, but I don’t think they were terribly satisfied with it.

The design wasn’t complete or perfect, but it was a real step forward. And I was very impressed by their willingness to challenge their pre-conceived notions about Mars travel and examine a design completely different from what they had looked at before. And it changed my mind about the value of nuclear electric propulsion technology. In a future post, I’ll describe how a design innovation I came up with could solve the remaining architectural concerns with the AG-NEP vehicle and make it far more feasible.

My contrast, the response of some of the MSFC personnel I was travelling with was not so open minded, at least with regards to launch options. Before we went over to the meeting, we met at a Denny’s for breakfast. There were two senior personnel, a mid-level manager, and me. One of the senior folks (who’s no longer with MSFC) began to lay down the “MSFC position” for the meeting, which he said would be Shuttle-C. I gently began to demur, saying how the use of Shuttle-C would commit us to using the expensive Shuttle infrastructure for decades to come. He quietly but firmly cut me off and said:

“The answer…is Shuttle-C.”

I understood from the tone of his voice that this decision wasn’t technical, it was strategic. Shuttle-C was based on propulsion hardware developed and controlled at MSFC. If the Mars program went forward, if this vehicle was developed, if Shuttle-C was baselined for its launch, then MSFC would be supporting it for many years to come. I looked over at the other senior person and he was nodding his head in agreement. I looked at the mid-level manager and he wasn’t saying anything. He and I were like enlisted men getting our orders from the officers. And so Shuttle-C it was…the only option we were permitted to present to the JSC study team.

As it was, several weeks later the Columbia was destroyed on reentry. Everything changed at the agency and everyone forgot all about Mars studies. But I still remember what I learned and think that there are lessons to draw from it.

Wrong. Super wrong.

Nuclear-thermal SSTO turns out to be one of the worst ideas anyone has ever come up with, for two simple reasons: hydrogen and the lousy thrust-to-weight ratio of nuclear thermal rockets. Those are the same two reasons that make NTR lousy or marginal for nearly any other space application as well, but this post will focus on the issues surrounding NTR SSTO.

In the case of any earth-to-orbit vehicle, you’ve got to have the thrust to get off the ground in the first place. Let’s assume that we’re dealing with a vertically-launched NTR SSTO. It has to have a vehicle thrust-to-weight ratio greater than one, and probably a fair bit better than that in the first place, just to get off the ground. So we can take those expressions that I derived before, assuming hydrogen as a propellant and the engine thrust-to-weight ratios that have been quoted by NTR proponents like Stan Borowski to quickly try to figure a payload fraction for an NTR SSTO.

We find the propellant-mass-sensitive term (derivation here) assuming the liquid hydrogen has a density of 71 kg/m3, ullage of 3%, a mixture ratio of zero, and a tank structural mass factor of 10 kg/m3. This gives us a value of 0.1452 for this term.

We find the gross-mass-sensitive term (derivation here) by assuming that the engine has a vacuum thrust of 15000 lbf, a weight of 5000 lbm, and vacuum thrust-to-weight of 3 to 1. I’m not even going to “ding” the engine for sea-level performance, since as we’ll see, it won’t even matter. With a vacuum T/W of 3 and the same for the sea-level T/W and an initial vehicle thrust-to-weight ratio of 1.25, and we’ll just say that the thrust structure doesn’t weigh anything either, the gross-mass-sensitive term comes out to be 0.4167.

We’ll also ignore any recovery hardware (wings, landing gear, TPS, etc) and say all that weighs nothing. We’ll assume that the engine has a vacuum Isp of 900 seconds and that it takes 9200 m/s of delta-V to get to orbit. Plugging those numbers in the rocket equation gives us a mass ratio of 2.835 (very good!) and a propellant mass fraction of 64.73%. Next we use the prop-mass-sensitive and gross-mass-sensitive terms, along with the propellant mass fraction to get the payload fraction (derivation here).

We start out with the final mass fraction (1 – prop mass fraction) of 35.27%. It doesn’t get any better than that. Then we subtract the gross-mass-sensitive term (41.67%). Now we could stop right here, because we’re already negative (-0.064). That is to say, even before accounting for the issues with tankage, we’re already out of performance. The engines weigh too much. But we’ll keep going and subtract the product of the prop-mass-sensitive term and the propellant mass fraction (0.6473*0.1452 = 0.0940) and we end up with a payload fraction of -0.1579.

So it’s a no-go with these engines. Our payload fraction is grossly negative and we’ve got nothing. It’s clear from the magnitude of the numbers that the engine thrust-to-weight ratio is the main culprit, although the “fluffy” liquid hydrogen tanks don’t help much either.

So what kind of engine performance would you have to have to get even a zero payload fraction? Well, I ran some rough calculations based on a variety of speculative vacuum T/W ratios for some putative NTR engine, at a few different values of specific impulse and plotted the results here:

The graph tells the story. To get payload fractions of zero (a launch vehicle of infinite size) you have to have a T/W at 900 sec Isp of over 10. That’s more than three times the T/W that Stan Borowski projects for his sporty 15K NTR design, which he says will have a T/W of 3. So if you think that Stan or others can design an NTR that only weighs a third of what he thinks it will weigh, then you can dream about an NTR SSTO of infinite mass.

As for me, I’ve thought for some time that NTR was a really bad idea for almost every application for which it is considered. The SSTO application is probably the worst.

The increasing tempo of VTVL development flights and the recent success of the Falcon 9 lead to possibilities for a different type of cooperative venture. Two companies have VTVLs testing  that are pretty much gas-n-go while SpaceX has vehicles that are quite difficult to get back. Using gas-n-go boosters to improve an expendable rocket payload might be a viable business.

Two VTVLs are built proportionate to the Falcon 9 and used as strap on boosters with propellant cross feed so that the Falcon 9 is fully fueled up when the VTVLs stage off and return to launch site for a pinpoint landing. What I propose that is different than what I have seen before is that the VTVLs separate at about a minute into the flight before transonic flight and maxQ is reached. By separating at high subsonic, the VTVL vehicles and the coop vehicle clusters never have to be designed for or subjected to the stresses of transonic and supersonic flight.

Subsonic flight is a far more forgiving and understood aerodynamic problem than the higher velocities and leads to considerably less problems, though also with less results. By staging at high altitude the Falcon’s engines are attaining near vacuum thrust and the vehicle could be considerably heavier than on a ground take off. A small tank stretch and a subsonic boost should get about 40-50% more payload to orbit. While the Falcon would be the main player, the supporting cast could improve the bottom line considerably with benefits for all.

The benefits for Falcon would be of the same order as the subsonic air launch scenarios that so many have studied. The VTVLs just do the airplane’s job. It is the emergence of the fast turnaround rocket vehicles that make it possible to virtually airlaunch in unlimited sizes.

The VTVL players would have a market for a fairly low velocity vehicle with a high dollar (compared to the suborbital field) market that doesn’t require high flight rates. It would give them early experience with a larger vehicle than would fit in their normal course of development, and a large launch assist platform in the bargain. Though the vehicles developed for Falcon assist would not go supersonic in their booster role, they would have plenty of size margin for modifications to allow them to carry relatively large VTVL upper stages to mach 3-4 and still do an RTLS maneuver for another flight or two that day.

SpaceX nailed the Falcon 9 on the first try. There is enough crow being eaten around the country now that somebody should put out a cookbook. My serving comes from the expressed belief that the opening of space will come through the incremental development with RLVs starting from suborbital through small orbital and so on, and not through all up test flights of ELVs. I could develop a taste for this brand of crow, so SpaceX, serve it up. Prove me wrong.

I haven’t changed my opinion of how space will be opened up in the long term, but this is an increasing sum game. I can cheer for my favorite teams without wishing ill on the others.

Ares is a different team in a different league playing a different decreasing sum game, so I can wish ill on that one. I think their players will be drifting away to more productive sports, and the events of Friday will accelerate that drift.

Recent events make it easier to describe one scenario for getting orbital costs down. This specific example almost certainly won’t happen and just stands in for the dozens of possible ways that orbit could become affordable.

Masten and XCOR have a joint venture for developing a methane lander. Consider the possibility of future cooperation. If in five years Masten and XCOR are operating profitable sub orbitals out of Mojave, it will be past time to start on orbital hardware. If both companies have 300+ kg payload capacities to above 100 km, then the Lynx  will have the capacity to lift one of the earlier Masten vehicles (Xombe 0.5?)to above 100 km. A fairly rapid partially retrograde development could have the small Masten vehicle capable of very long suborbital flights if properly assisted.  Say, Mojave to Kodiak, Oklahoma, or New Mexico. The Lynx lofts the Masten vehicle to mach 3-4 at high altitude and stages. The Masten test article finishes the boost for one of those spaceports while the Lynx returns to it’s runway.

The experience gained in test flights with almost existing equipment will go a long way toward convincing investors that orbit is well withing the reach of a conservative  three stage to orbit transport. (Pete suggested this as two stage over on Transterrestrial) The reentry problems can be explored for mach 10 to 15 including turnaround time and environmental impact. Reentry noise can be one of the largest hurdles for inland recovery of second stages. If, and only if, inland recovery can be done in an acceptable manner will this concept work. A tiny smallsat stage might be launched from the Xombe 0.5 if required to make the point.

For a second set of tests, Masten launches a three barrel vehicle with their full size suborbital craft. The two outers deliver the same assistance to the center vehicle as Lynx does to the smaller craft. The full size suborbital vehicle lands downrange at one of the available spaceports. Once this is explored, a 300 kg upper stage is used to place a useful smallsat in orbit. Some testing is done on recovering the upper stage.

If the above tests confirm that the technical concept is sound and acceptable to the uninvolved public at the recovery spaceport, then funding can be sought for a full orbital system. A much larger XCOR vehicle (Panther  for this post) is developed to launch the full size three barrel Masten (Xorbit for this post) assembly. This time the two outer vehicles cross feed propellant to the center vehicle and land at one of the downrange spaceports. The center vehicle goes on to deliver 300 kg of payload to orbit. This allows XCOR to focus on the much larger suborbital Panther while Masten focuses on improving existing vehicle performance and reentry. The Panther could also be the rent-a-booster as Clark suggests over on Space Transport News. The technical risk to orbit from that point would be comparable to funding XCOR and Masten to a full suborbital operation now.

A launch organization has four main costs. Development costs. New vehicle costs. Fixed operating costs. And marginal costs. Only marginal costs are mostly unaffected by flight rate. On a gas-n-go vehicle propellant is a major marginal cost.

On this three stage to orbit with each stage having a mass ratio of three, (total MR=27) there would be about 36,000 kg of propellant or about $18,000.00 per launch. Other marginal consumables would double this to $36,000.00 per launch or about $120.00 per kg in marginal costs.

Starting from a base of operating vehicles and recent development experience with an intact team, I speculate that the development cost would be about $250M. Expected interest on the money for this high risk field could easily be in the 25% range for a development cost of $65M per year to service the debt. If there is one flight every two weeks, $2.5M per flight to service the debt. At two flights per week, this drops to $625K. With multiple airframes flying twenty payloads per week, this drops to $63K per flight to service the debt.

New vehicle costs for the four airframes (Panther and 3 Xorbits) could be in the $20M range after the bugs are out. At a flight every two weeks, it would take $770K to pay off a set in a year. At two flights per week per airframe, it drops to $193K to pay off in a year. If some financing can be arranged, then costs can drop considerably more. (It could be much less in the reality as the Panther could lift 20+ times per week while the Xorbits could possibly do two each.)

 My first guess on fixed operating costs is $30M per year keeping two or more spaceports fully operating with all support staff, including transporting the Xorbit stages back to Mojave. These numbers are based on this guess. At a flight every two weeks, $1.154M per flight. At two per week, $289K per flight. At twenty flights per week, $58K per flight figuring that staff doubles at that flight rate.

flight frequency   debt    vehicles      fixed              marginal           total      

two weeks           $2.5M    $770K       $1.154M        $36K            $4.46M     

two per week    $625K      $193K         $289K          $36K            $1.143M    

twenty per week$63K      $193K         $58K              $36K              $350K     

If it worked out like this, then a flight rate of once every two weeks would break even at a little under $7K per pound, while twenty flights per week could get it down to around $530 per pound. A lower flight rate under every two weeks would make the plan unworkable while a higher flight rate than twenty per week would make it somewhat cheaper than $500.00 per pound. These numbers assume that interest only is paid on the development and that the vehicles must pay for themselves in one year.

This is very much a first generation space transport. Obvious places to get the cost down further are to reduce development costs while still getting an acceptable vehicle group. Getting a better interest rate. Improving propulsion and dry mass fraction to get the mass ratio down from 27 to 16 or so with less dry mass to lift in the first place. Getting it down to two stages to orbit to eliminate supporting downrange spaceports and the extra stages. Flying each airframe more than the twice a week I have here. Reducing the cost of new airframes and spreading the payback time over more than one year. Reducing the number of support personnel required per flight. And so on to get costs insanely low compared to the present day.

 Developing orbit into an economic driver is going to take a lot of work and intelligent handling. Orbital development to date with existing transportation is a mere shadow of the possibilities given transportation that is economical, reliable, and convenient. Everything changes when a decision can be made and executed reliably and affordable in a matter of weeks or possibly days. When was the last time you scheduled anything years in advance? How many times in your whole life do you schedule something years in advance and know that it might cato before it gets started? That is what the whole launch industry is forced to do at this time.

Basing on this cooperative venture creating a somewhat convenient transportation method to orbit, speculation on markets becomes possible. The first markets are somewhat limited in orbital inclination by the restrictions of the downrange spaceport requirement. The choices are a somewhat retrograde high inclination orbit, or a normal orbit with an inclination at  Mojave’s latitude. Anything to ISS is out due to inclination restrictions. Tourism is out due to the small vehicle size. What can you do?

While proving the vehicles, expensive payloads are out, so the focus must be on things that have low intrinsic value with only being in orbit making them valuable. Propellant is the first obvious choice. The first launch to each available inclination carries the largest propellant tank that it can as payload with subsequent launches filling it up. Or possibly one of the ELV companies leaves an upper stage in the right orbit that can serve as a depot. This is only good if there is a market for propellant from that particular orbit though. I dislike the concept of buying propellant, or water, or sand in orbit for the purpose of artificially creating a market.

The first stopgap depot would need to be in a normal orbit at Mojave’s latitude. When it has sufficient propellant delivered to make it worthwhile, one of the majors launches an un fueled GEO bird from the Cape to rendezvous with it. A 25 ton GEO bird unfueled could take on 50 tons of propellant before boosting to it’s final orbit. This would make for a very massive satellite compared with the current operational GEO sats. This would take about 170 launches of Panther/Xorbit. A contract for a million a launch would be profitable to both sides. The GEO provider would have the capability of a 75 ton launch vehicle for an extra $170M per GEO sat while only risking a 25 ton launcher. The Panther/Xorbit companies would need to get the launch rate above 3 per week to make a profit and pay off their debt. The 3 launches per week to reach profitability would take over a year to complete for each GEO bird that takes advantage of the capability. Assuming there are at least two of these monster satellites per year to refuel,  the launch rate is at nearly 7 per week. If deliveries could reach that flight rate, about 40% of each launch would be for profit or paying off the debt. Debt payoff would be under 3 years and would further reduce the launch costs by a factor of almost two, which would make the launches even more profitable at that price point.

Propellant is not the only possible cheap on the ground expensive in orbit payload though. Military surveillance would benefit from the ability to place fleets of cheap observation satellites in orbit. The gaps in coverage of the existing sats are most likely known to the people with something to hide. They probably time most of their sensitive moves to take place in these gaps. The military could easily spec an LEO surveillance sat that could be mass produced for under half a million. Though these birds would be far less capable than the high end machines they use now, a thousand of them would provide wall to wall coverage. At a million a launch and half that for the actual satellite, they would be looking at $1.5B for the whole program not including collecting and integrating the data. Allowing three years for placing the constellation, flight rates and costs match that of the propellant market only. Under three years to payout and higher profit thereafter.

Communications is frequently brought up as the target for early market. With cheap reliable launch as suggested here, less capable LEO satellites could be used in constellations with spares on orbit and on the ground ready to be launched in days if required. It is quite conceivable that these 300 kg comsats could be mass produced for a half million just as the surveillance satellites are. A billion and a half for a robust LEO comsat constellation of a thousand birds should be a business plan that would close. A three year launch schedule has the same numbers as the propellant or surveillance constellations. Under three year payoff and 40% profit after at a million a launch.

Astronomy and microgravity science and Earth observation satellites should be a market to match the last two.  Though the individual capabilities are less with the smaller satellites and cheaper construction, a cast of thousands could make up the difference. The ability to launch follow up or replacement experiments in a week or less would make commercial use of LEO much more user friendly. Over a hundred countries with thousands of universities and tens of thousands of private companies would be the market this time. With similar launch rates to the other users, the money works out the same.

If all four of these markets were to emerge though, a flight rate of 30 or so per week would drop costs still further. Costs of under $350K per flight would allow a charge of a half million per flight to make over 30% profit available for the debt payoff or investor ROI. It would also create even more incentive for the users of the service to make less expensive satellites for an even lower total cost. $4.5M per week profit would pay off the development debt in just over a year.

The assumption that these satellites would be inferior to the $Dirksen Galactica models launched by the current providers might not be true. The current birds are just too expensive and hard to replace to fail so every possible effort is spent making them reliable. This means literally gold plating some components and using only hardware that has been “space rated”. The time required to space rate components added to the long lead time on the current launch capability means that by the time any component reaches orbit, it is incredibly expensive, and it is obsolete by standards on the ground. The point has been made many times by many people that many of the current satellites, especially comsats,  are so expensive that the cost of launch is not all that important. With replacement launch on demand, satellite reliability becomes somewhat less important. It becomes possible to launch the latest electronic devices without “space rating” them at all. If they survive, they are space rated, if not, they are not. Henry Spenser has noted that the commercial stuff launched in the Canadian satellite that he worked with has lasted for years. How much capability is in $10K worth of May 2010 commercial electronic components components compared to $100M of “space rated” 1995 electronic components?

When failure is not an option, success can get expensive. We have all read that. How many have also noted that when failure is not an option, success also gets much  less capable?

With launches available on demand for half a million, many high risk or complicated capabilities can be tested and possibly implemented. A 300 kg tug could do considerable work in LEO. It is past time to deploy tethers for extensive testing. Debris cleanup vehicles can be tested and then employed. Fairly small service vehicles could do good work in GEO. National Geographic could afford a 300 kg Lunar, Mars, or NEO probe that was launched on one flight and fueled up by others.

It just gets better and the sky is not the limit.