An Opinion on an Architecture

Doug Plata has a new website at spacedevelopment.org with a concept for sustainable Lunar development. He sent me the link and suggested I look it over. I read it through the first time as a plan and promptly (in my mind) picked it apart. I went over it again as a conceptual approach coming away with considerably more positive feelings about it. I am quite opinionated about various approaches to getting things done with a normal reaction that I could do this or that better after someone else has done the heavy lifting of the initial approach. Anyone interested in developing the moon would benefit from a reading of his website including all the specific links.

My take on it is that it contains many desirable features and has missed a few critical points. One of the main ones is the knock on effect that the drop in launch prices will bring. I can see prices to LEO dropping to under $500.00 a kilogram within the timeframe he is suggesting. FH, New Glenn, BFR, etc in the near future. At that rate, a billion dollars launches 2,000 tons into LEO.  This is the main basis for the criticisms I see. I will use that number in this post.

Doug suggests that a small percentage of the NASA budget could implement his scenario. A billion a year being 6-7% of the normal budget would be sufficient if used intelligently, mostly with COTS type applications. I don’t see any NASA managed project of this magnitude being immune to the various congressional feature creeps for the long term. Major NASA programs  tend to multiples of that, which then tend to political rather than effectiveness direction. He makes a few mentions of international participation which to me has the same effect multiplied. IMO, his scenario needs to be a private venture ramrodded by a hardheaded businessman with a solid technical team in order to remain in reasonable cost territory.

I can see a variation of his vision being done possibly faster than his website suggests. One example is that of the partial gravity research that has been left fallow for so many decades. He suggests the partial gee research takes place on the moon after the early human landings. I suggest that a 50 ton partial gravity research facility in LEO will be possible for $25M in launch costs and  less than $10M in hardware costs. $200.00 a kilogram for hardware is in line with terrestrial computers and electronics, and well above most hardware. With low launch costs, much of the over engineering of current spacecraft can be eliminated. The partial gravity research could start year one with results starting to be well characterized before the first human landings on the Lunar surface. It could be known whether a fetus could develop at 1/6 gravity by the time the first couple headed that way. It may not even be necessary to have a centrifuge on the moon, or it may be desirable to have a much larger one. That knowledge is necessary and long overdue.

The focus on finding and mining water dominates much of Dougs’ concept. I think the results of inexpensive launch has not been well factored in. With methane/LOX a mass ratio of about 5 from LEO to the Lunar surface puts a ton in place for about $2.5M for launch costs.  A hundred tons of water for a quarter billion FOB moon seems like a good early supply. Four hundred tons of equipment and supplies delivered to the moon for a billion dollars seems like a good year two operation. By exploring and prospecting for all potential valuables instead of a water dedicated mining operation, it seems possible that better and easier sources of almost everything will be found. It would be most unfortunate if a massive effort were made to extract water from the polar regolith only to find that nearly pure sources were available in many locations. It would be bad as well to hope that better sources would be found only to find that the polar regolith was indeed the only reasonable source. I suggest a lot of exploration and prospecting before major mining investments.

Doug puts a lot of emphasis on communicating the excitement to Earth in as many languages as possible even if by naturalized Americans with all early crew members multilingual. I personally place less value in talking to people than getting them there in the first place. If a person can be delivered to the Lunar surface alive and healthy with a ton of gear, launch costs of $2.5M per person are down to the point that any interested nation should be able to pay their own way. The six person international teams that he suggests could get there, stay a while, and back for under $40M. Any nation group that can’t or won’t supply that level of support shouldn’t expect much sympathy from those that do pay. International pride would come from self sufficient groups paying their own way instead of being dependent on the charity/political connections of others.

The gymnastics and dance routines that he suggests be practiced with tethers on Earth could instead be developed and learned properly in the Lunar environment. Artists need some freedom to be artists. Earth control and choreography is unlikely to give the best results  compared to the experimentation on location by the artists themselves. Again, $40M for a gymnastics or dance troupe to spend a month or so on the moon seems a quite reasonable cost. It also doesn’t require your geologist to be selected for athletic abilities.

The suggestion is that crew should have very long stays of several years or perhaps indefinitely due to costs and transport risks. I suggest that that attitude is caused by the ridiculous prices of crew transport that exist now, and not those that will exist in the near future. At the $2.5M that I suggest will be possible to get someone to the Lunar surface, and about that much more for a year of supplies, crew rotations could resemble those of the ISS currently. While some could stay longer and would be encouraged to do so, I don’t see it being the bottleneck to Lunar development.

Some of the hardware in the scenario seems to be missing a few tricks. The lander based on the  Masten Space Systems work with ULA seems like a future manned transportation system to the Lunar surface. For early hardware delivery, a variation of the Falcon 9 hover slam seems to have something to offer. A stage that hits hard or tips over is not going to explode as seen in footage of some early barge landings. The propellant will evaporate in the vacuum faster than it could sustain ignition. So the cargo could be saved even in the early learning curve landings. An upright stage that landed properly could unload with an onboard gantry crane in the 1/6 gravity. Several companies could learn by doing rather than learn by designing and simulating and then learning the hard way anyway.

A Lunar rotovator has been proposed many times and a development scenario like Dougs’ could afford to learn to operate it. A 1,600 m/s rotovator could pick up as well as deliver which would eliminate much of the need for mining or delivering water. A 25 ton unit could pick up and deliver ton packages, though not people at first.  That would be about a $100M investment that would pay off in operational knowledge that could apply to LEO, Mars and asteroids just a few years on.

A depot scenario would benefit this development. A delivery to LEO that had extra mass capacity could deliver propellant as a secondary payload for nearly free. A refueled upper stage would make a dedicated transfer stage unnecessary. Refueling or off loading extra propellant in Lunar orbit could also make the trips more cost effective. Storage facilities in Lunar orbit and on the surface would definitely enhance the value of Lunar propellant when it did start becoming available.

Doug mentions saving the capability of the SLS for Mars missions. I say why bother if 4,000 tons can be placed in LEO for the price of one SLS launch. I also disagree that a manned Mars flyby is a useful mission. Phobos and Demos mission, maybe, though I’m not sold on those either. Of course, not being a Mars enthusiast, I probably would be a hard sell for a surface mission as well.

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A Flat Earther

I had a new experience tonight. A woman I went out with a few times a year or so back got in touch and we went out for dinner. Somewhere in the middle of the dinner she mentioned that she had looked into the flat Earth claims that some people are making. I waited for the punch line.

She said there are no pictures of the Earth from space as a round ball. The cameras take a bunch of pictures that are spliced together to make it look that way. Spacecraft couldn’t get through the Van Allen belts anyway so that is why there are no pictures of the whole Earth. The dozen or so pictures on my phone were obviously photo shopped because every picture was different and if they were real they would all be the same. I waited for the punch line.

We obviously didn’t go the the moon and it was all done on sound stages and such with CGI. Frank Bormans’ Earth rise picture  was made from a dozen pictures spliced together and wasn’t real. She knows because she saw an interview with the guy that made the picture and he told how he did it. And then there was the interview with three astronauts just back from the moon. They should have been pumped up but instead they were somber because they knew they were lying to everybody. I waited for the punch line.

The Earth couldn’t be rolling around like they said because at a thousand miles an hour the wind would destroy everything. The proof being that a helicopter that went straight up for an hour and came straight down would come down somewhere else because the Earth would have rotated out from under it if it was really rotating. I started doubting that there was a punch line.

Further proof that the Earth wasn’t round came from some photographers that took some pictures of the Chicago skyline from across Lake Michigan. If the Earth was round they wouldn’t have been able to see it. There was more evidence gathered by people with the same type special camera that could see ships that should have been hidden by the curvature. I realized that there wasn’t a punch line.

Gravity is an illusion because density and mass are the same thing. Several time she mentioned that she was intelligent and not gullible. At somewhere around this point I quit trying to answer seriously and got annoyed. It is possible that me calling her opinions stupid is not conducive to further interaction. I remember thinking that she made Gary Church sound rational. The punch line was me as I had forgotten why we quit going out a year ago.

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The Fate of the Falcons

At some point it seems that SpaceX plans to retire the Falcon series in favor of the BFR (series?). For a fully developed and productive launch system to be retired due to improvements within the company line there must be compelling reason. If it comes to pass of course.

The Falcons seem to have reached one of their goals with 16 successful landings in a row. So are the accumulating first stages of a reusable vehicle to be left to rot when the new kid takes over? Seems quite odd to me. If the BFR series ends up as cheap to operate as projected, it’s just possible that the Falcons cannot be profitably flown by SpaceX when development becomes operations.

What about other launch providers. By the time BFR is fully operational there could be dozens of flight proven Falcon cores available. How many providers would jump at the chance of buying a first stage that could be flown repeatedly after some modifications of their own upper stages. It still wouldn’t let them compete with BFR. It would however, allow them to operate a national or corporate proprietary launch system for substantial savings without having to buy launches externally.

This could provide revenue from the vehicle sales to SpaceX just when it is trying to recover financially from multiple development efforts. There would be a steady revenue stream from parts and technical assistance. It may be one of the reasons for proving the recovery of the vehicle in the first place.

I could see ATK buying a couple of cores to fly out their manifest without have to deal directly with a competitor. Ariane could probably use a few. I wonder how the economics would trade for India.

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Falcon Heavy Skepticism

The long anticipated Falcon Heavy should fly towards the end of this year. Many people seem to believe that this launcher is going to be the answer to the PorkLauncher, big private payloads, launch costs, reliability, and all the other competition. I tend to think it can be a good launch vehicle without being any of those things.

Up until recently, I thought bolting three or more first stages together for larger payloads was close to a no brainer, especially if those stages are getting reused. I saw little problem with using up to seven stages bolted together. A few recent articles have made me question my previous opinion. One about Elon Musk discussing the difficulties of  making three stages work together brought up a few interesting issues on the problem. Another by Rand Simberg going into some detail on dispatch reliability and complexity issues that I have not previously considered.

I have been skeptical of some of the claims made by people from outside the company since they started posting them. There are some that insist that the F9H is going to get costs per pound down to $50.00 or less. I still believe it is too early in the game to confidently predict such prices. It should be possible to be a fan of the SpaceX accomplishments without being a wild eyed fanboy that thinks Elon walks on water in the liquid phase. There are some more debatable points I have met relatively recently.

The F9H will be the death of SLS/Orion as soon as it flies seems to be fairly popular. This would seem to be against the history of government procurement programs. The logical arguments against developing the SLS/Orion system were as valid a decade ago as they will be when F9H flies. If it was about logic, a crew capsule would have been flying on an EELV before the Shuttle was retired. An orbital depot would have enabled any mission the SLS/Orion is purported to have. The SLS/Orion may go out with a whimper in the next decade. It is politically nearly impossible that it will be in direct response to the early flights of the F9H. A politician has a primary job of getting elected, and the SLS/Orion systems will last as long as they contribute to that primary job.

There seems to be a lot of belief that huge private payloads will be ready to go as soon as the LV is available. I don’t think this matches payload history on current launch vehicles. Ariane5 and Delta Heavy don’t seem to have a backlog of full weight payloads. It is common for there to be two or more full size satellites in an Ariane launch. For that matter, F9 doesn’t seem to have payloads that come close to the advertised capability. I believe that the F9H will be an infrequent launcher of specialty payloads that are just a bit more than the F9 and competitors can handle. Once proven, it is likely that the F9H will have single digit flights per year. Elon has mentioned that one of the reasons for the delays in getting the F9H on line is that there is little demand for it. Plenty of others have mentioned that the steadily increasing capability of the stock F9 also cuts into the demand for the heavy.

Launch costs are the choke point on space development and always have been. Many people believe that the F9H is going to solve this problem. The advertised prices seem to support their opinions. The normal method of figuring launch costs use dollars per pound as the metric of affordability. Dividing maximum payload by launch price supports  the belief in the F9H as the frontier enabler. My skepticism comes from some recent articles discussing technical issues I hadn’t previously considered. When the rubber hits the road, all three of the first stages in the F9H have to go through the same level of processing as in a normal F9 flight, plus be integrated into a complete F9H. The additional level of work required to make three stages into one makes it likely that the actual launch prices per pound will end up being higher for the F9H than for the stock F9.

I expect the F9H to be a fairly reliable launch vehicle. I can’t see it matching the parent vehicle in that respect. There will be some risk associated with three cores working together with aerodynamics, vibration, and structural loads that don’t apply to the F9. There will be the additional risk of individual reliability of four stages instead of two in the F9. Very low probability events per stage will have twice as many chances to manifest in the larger vehicle. There is also the likelihood IMO that the F9H will have a much lower flight rate than the stock F9 which could lead to a bit less proficiency in catching the minor issues. Bottom line is that unless the F9H flies a lot, there will always be some question as to its’ reliability relative its’ parent vehicle.

I find the opinions often expressed that the F9H will sweep the competition to be less well thought out than they should be. As long as there are many reasons to launch a variety of sizes and orbital inclinations, there will be a variety of launch vehicles to serve the various niches. From national launchers to smaller proprietary payloads to personal animosities, there will always be reasons to have other launchers by other countries and companies.

At the end of the day, I expect the Falcon 9 Heavy to be a good launcher with fair reliability. I don’t expect it to be the greatest or the cheapest, just a good machine for the intended purpose.

 

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Roton as Booster/LES/Shroud Recovery

This idea has been kicked around in pieces before, though I think this particular combination may be unique.

Mount a Roton blade system on top of the shroud of a standard launch vehicle. Power it up before launch such that it is supplying perhaps 20% of the total thrust at sea level. At the 10/1 Isp gain early on, this would be a serious enhancement to the vehicle performance.

If there is a launch vehicle problem, the payload and shroud are detached to be accelerated out of harms way by the already thrusting Roton unit using it as an LES system.

The Isp gain will fade as it climbs out until in vacuum the tip rockets are at perhaps Isp 300 which is less performance than the main propulsion system. When the shroud is ready for detachment, it is separated from the launch vehicle and pulled away by the Roton unit.

The Roton unit is used to control the shroud reentry and to guide it to a recovery vessel where it auto rotates to a landing.

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A Possible LEO Clearing Market

One of the growing concerns is the amount of small debris in LEO. The big stuff can be tracked and mostly avoided, but the small stuff is a more difficult proposition. A hundred gram shard at some LEO closing velocities can impart the kinetic energy of a main tank gun. It is not the new large satellites that are the problem as most of them have deorbit strategies built into their launch vehicle upper stages and their own end of life safeing plans. It is the thousands of much smaller units proposed by all and sundry that concerns some people.

With the quantity of LEO debris existing and tens of thousands of small satellites that may hit orbit in the next decade, the odds of collisions are higher than some people like. Each collision will create large quantities of smaller debris in unpredictable orbits that increase the odds of further collisions in an ever increasing cascade. I personally don’t know the odds of this happening or if it is a rational concern. There are some people that appear well informed that are seriously concerned about a Kessler syndrome that could make LEO uninhabitable by man or unarmored machine.

It would seem that there might be a market developing sometime in the next decade to remove small debris from LEO from simple self interest. Present and future LEO operators along with their insurance companies might decide that the time has come to address the problem. Deciding to address the problem does not necessarily mean that they will feel generous about the solutions. The tragedy of the commons will not disappear like the air and gravity in LEO.

The solution for cleaning out LEO will have to be economical, safe in terms of having near zero chance of making the problem worse, and work in a timely manner. It won’t happen if the proposed solutions are too expensive, risky, or take centuries to operate.

I suggest that a modest satellite could be launched into polar orbit to get a start on the task. It should have excellent detection equipment along with enough on board computing power to calculate intercept trajectories in real time of objects closing at up to 14 km/sec. After action tracking and calculation must be capable of checking the new orbit or deorbit of the target debris.

The mechanism I suggest is laser sails the size of kites that are steered to intercept by the on board laser. The south bound orbit would focus on debris on the northern leg of their orbit while on the north bound portion it would focus on the debris on the southern leg of their orbit. The zigzag of normal west to east orbits to the limits of their inclination would provide high closing velocities with impact resultant sub-orbital if done right.

In this cartoon, the cleaner is heading south with one of the kites in position to impact some debris heading north-east. The dotted line is the possible changed trajectory of the debris as it deorbits. The purple rectangle is a kite that has been used a few times.

The cleaner is heading south and a piece of debris is heading north east with a closing velocity of between 12 and 14 kilometers per second. The laser propelled and steered kite array is a hundred or so kilometers ahead of the cleaner and one of them is off to the side that the debris will pass through. The kite is laser propulsion steered into an intercept which costs the kite a bit of sail and the debris a bit of velocity. Each gram of sacrificial kite material impacts the debris chunk with the kinetic energy of several 50 caliber bullets. Depending on the amount of sacrificial kite mass, debris mass, and debris orbital velocity, a deorbit is likely. Failing that, the debris should have a much lower perigee that will speed up its’ orbital decay.

After the kite has been used several times it will look like Swiss cheese and is steered back aboard while other kites take its’ place. Two or more ventilated kites are mated together for another go in their turn. Repeat until there is nothing left of the stock of kites but tatters. Then the cleaner sat is either replenished or deorbited in its’ turn.

It has often been suggested that the debris should simply be targeted with a laser. The ablation of the larger debris would cause it to deorbit while the smaller ones would be vaporized. It seems to me that it would take a lot more laser and power to get that job done which would create a couple of other problems. One is that it would be far more expensive, and the other is that it would clearly be a space based weapon.

While it would still take a considerable amount of time to significantly reduce the debris field, a 50 kilometer track per orbit would be bandwidth limited rather than hardware limited. Several dozen or hundreds of pieces gone per day would add up over time. Off hand each gram of sacrificial kite could take down a hundred grams of debris. A ton of lost kite for a hundred tons of eliminated debris seems like it would be a good trade.

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Comment Bumping: Venus Electrolysis and Space Settlement Norwegian Perspective

Life has been busy enough lately that I haven’t been able to do many of my own blog posts, but I wanted to bring two recent comments from old Venus threads to the top to get them a little more attention than they’d likely get in an old side thread.

The first was a question about the feasibility of using the lower Venusian atmosphere for electrolytic extraction of metals from the surface:

James Walker wrote:

A question for the more scientifically literate: With a charge of 10 volts and a pressure of 93 bar, is the atmosphere of Venus thick/charged enough to allow electrolysis?

If so, is having cathodes in the atmosphere collecting Potassium, Sodium, Magnesium, and Aluminium from the acid drenched surface an option?

Not being a chemist or electrolysis expert, I don’t know for sure the answer, though my gut suggests that it’s probably no. If the lower atmosphere of Venus can carry a charge like that, that’s usually a sign of it being a dielectric material, not an electrolyte like you’d need for electrolysis. Unless I’m missing something. I mostly brought this up, because there are enough other people on here who could answer better than I, and while I think it’s a long-shot, it would be huge if it was actually true. Thoughts? Comments?

The second comment I wanted to bump was from a discussion about what the governments would need to be like in isolated settlements in harsh environments. One poster had speculated that the harsh environments would make Venusian cloud colonies, asteroid mines, and other such places fairly totalitarian. Povel Vieregg from Norway had an interesting competing perspective (the part that stood out to me starts five paragraphs in):

I thought I’d add my two cents about the politics and types of society that a Venus colony would be. A lot of people here related to the American experience, but I think there are many other cultural experiences to draw from to say something about this.

As a Norwegian, I also come from a country which had its own flavor of rugged individualism. Norwegians also settled Iceland and went on many polar expeditions. All cases which involved extreme climates and environments.

I personally think people have a tendency to overstate the influence of nature on the culture of a people. For instance the Dutch as surprisingly similar to Norwegians in ways of thinking and organizing society, yet their country could be no more different from Norway. Shared germanic roots and similarities in way of life (both maritime nations) probably led to many similarities.

Americans should not forget that a large part of their national character derives from the British and Irish.

I don’t think it follows that great dependency on each other leads to a totalitarian style regime. I think individualism exists in different forms than just the anglo-saxon style libertarianism. The Vikings were quite democratic minded, or perhaps a better description would be that they were used to seeking and making compromises and find consensus. That was a natural result of weak central power. The dutch are similar. Many lived historically in polders (farm land surrounded by dikes keeping the sea out). If anyone living in the polder failed to maintain their part of the dike, it would spell disaster for everybody.

Neither case led to totalitarianism. Quite the opposite, both Norway and the Netherlands are very consensus oriented democracies. You see similar on Iceland which also lived through pretty rough times when it got settled with a lot of bloody conflicts. That kind of hardship teach people that there is no alternative but to cooperate.

If you read about the polar expeditions by the British and Norwegians, you’ll see very big difference in the approach and culture involved. The British had strict power hierarchies, were commoners and officers were clearly separated. Norwegians had much flatter hierarchies, and was more based on cooperation and consensus that some top leader acting as dictator.

You can see this among any primitive people. Look at Inuits e.g. who live under harsh climates. These groups don’t function as totalitarian regimes. They are not fully democratic either, but there are more marked by cooperation and consensus than by master-servant relationships.

I think likewise a Venus culture will develop with a basis in the culture of the original inhabitants. But I do think that over time it will develop in the direction of Dutch/Norwegian experience. Nobody will have a natural power base to just be a dictatorial ruler. There will be too strong interdependency among people for anybody to assume too much power. You will have to listen to what everybody says.

I don’t think you can necessarily classify such societies as we do countries today, because they will be much smaller and will thus be based far more on informal structures as we see in smaller human societies.

When societies are smaller they can function primarily on trust. As societies get much larger and you can’t know everybody in it or trust them, one will have to rely much more on formal structures and rules.

Anyhow, I know that just reposting peoples comments instead of creating new content of my own is kind of cheating, but a) I thought they were both very interesting, and b) it’s going to be a while before I have the bandwidth to write anything of my own, and I can’t let John have all the fun on this blog.

Posted in Comments, ISRU, Space Settlement, Venus | 16 Comments

Failed Visions (mine)

I just read that XCOR laid off its’ remaining employees with a few core people kept on contract. This is another shot against the vision that I have blogged and commented about many times. The concept being that sub-orbital RLVs would create companies and teams with experience creating RLVs. This is where orbital RLVs would come from. It appears that I was off so badly as to defy excuses.

XCOR seems to have joined a number of other sub-orbital efforts that have folded, or gone into stealth mode at least. Armadillo and TGV being a couple of the best known along with a dozen or so of varying credibility around X-Prize time. I don’t think Virgin Galactic should be considered a validation for my vision even if they are eventually successful.

SpaceX is coming at RLV from the other direction, backing into it from an expendable. I’m sure I’ve posted or at least commented on several occasions that this was a bad idea with little chance of working. Blue Origin  seems to be using its’ sub-orbital RLV as an X-vehicle for its’ orbital class RLV. It would be a stretch to suggest this is similar to my vision as it seems to be a parallel effort rather than serial as I suggested might be necessary. The other orbital companies talking RLV seem to be dragging their heels on any changes so I discount them for this post at least.

It does seem to validate one argument I’ve made from time to time about the difficulty of sub-orbital vs orbital flight. The argument by some others was that orbital flight was 8 times the velocity of sub-orbital flight and difficulty rises as the square of velocity so that made it 64 times as hard. The ones making that argument didn’t believe my calculation that it was more like 4-5 times the difficulty. Maybe they can note that several attemptees have had far more than 1/64 of the funding of SpaceX or Blue Origin with no flying hardware.

There is a bright spot or two though. Masten is still going, and a few others are still in the game. Come on guys, you are the last hope to make me right on this one.

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Mars Barges

One of the incredible mentions in the Elon Mars concept was a thousand spacecraft in orbit ready for the Mars launch window to open. I’m not sure how many launch windows down the road this would be, I assume several decades. Whether it is next decade or next century though, an expensive asset like a spacecraft that is only capable of being used once every other launch window is a massive investment that is mostly idle.

I suggest an alternate concept for having a thousand vehicles heading toward Mars during one launch window. Each vehicle is an inert barge with a homing beacon and barely enough structure to house the cargo during thrust and coast. No engines, electricity, shielding, or other frills.  These barges carry only items that store well. Machinery, provisions, propellant, clothing, etc.

The orbital gathering place for these barges is a high Earth orbit above the radiation belts but below Lunar orbit. The storage orbit keeps however many barges are heading out during each launch window in  parking lot adjacent to a refueling facility that is stocked up between launch windows. The third item is skeletal booster tugs with no frills like ability to reenter or handle gravity.

There is a certain limited amount of time in a Mars launch window when the Hohman transfer orbit uses minimum propellant. There are periods of time on both sides of the ideal window that still get you to Mars, just at the expense of additional propellant. Total available time in the window can be a few months depending on available propulsion.

At the first opportunity, a tug with a dry mass of perhaps ten tons, a propellant load of two hundred tons, and a hundred ton barge, does a short burn to drop its’ perigee to just outside noticeable atmospheric drag. At perigee it is at nearly escape velocity when it does a strong (~4km/sec)Oberth effect burn to place the whole assembly on a Mars trajectory. Immediately after reaching the required velocity, the tug separates and a short retro burn to place the light tug back into an eccentric orbit with an apogee equal to the barge parking lot. The orbital equivalent to the F9 boostback.

Back at the parking lot, the tug does a short burn to match velocities and goes for docking. Refuel, clamp onto another barge, and go again on intervals of one to four days. Depending on assumptions, each tug could send as many as a hundred barges per window to be caught on the other end.

So I can see the possibility of a hundred thousand tons of vessels heading to Mars during one launch window. The main hardware investments being launch vehicles, depots, and tugs that are kept employed at other tasks in the meantime between windows. People launch separately in vehicles suitable.

The main strength I would see in a scenario such as this is that the expensive hardware would be constantly available for use for other tasks. This is important for those of us that don’t see that much value in Mars as the next step out. The same equipment would be useful for asteroid missions or sending a Pluto lander. A heavyweight to Europa or a close solar corona  investigation. Or more immediately useful support for Lunar and NEO missions.

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Stratolaunch as Falcon9 Competition

The roll out of the Stratolaunch aircraft started a considerable amount of criticism on the sources that I read. Basically it has the same problem as the White Knight, superb aircraft with no viable rocket to mate up with. I wonder though if that is the reality.

The Stratolaunch aircraft is supposed to have a lift capacity of 500,000 pounds under that center wing. It would seem to be ideal for the three barrel launch vehicle that Gary Hudson was suggesting a few years back for air launch. Visualize a Falcon 1 heavy slung under that wing with all three Merlins the vacuum variant.  That’s just to create a visual. Now realizing that Musk isn’t involved, I go to the vehicle that I believe could exist somewhere Real Soon Now.

Paul Allen apparently went through three different big name booster companies before settling on the Pegasus. Except the Pegasus doesn’t make sense for such an aircraft. It would seem possible that somewhere there is a very quiet development effort going on. I can think of a few companies capable of developing the vehicle I am going to suggest without feeling the need to Branson about it.

When launching from over 34,000 feet, more than 3/4 of the back pressure losses from sea level are gone. This means you can have a higher expansion ratio nozzle, or lower chamber pressures, or some optimum combination of both. With lower pressure engines that still have good performance possible, pumps become simpler to develop, or even unnecessary with pressure fed by modern materials. Simpler is cheaper. Three barrels with one engine each with all large expansion ratio nozzles. Probably methane and LOX for the self pressurization aspects even at the cost of higher residual pressurant  mass than with helium. Very much an operational cost conscious design.

I start with a GLOW of 500,000 pound as maximum for the aircraft. Suggesting an exhaust velocity 3,300 m/s throughout the flight. 8,000 m/s from drop to orbit. Stage  mass of 8% at cut off.  Total mass ratio of 11.3. Mass ratio to outer stages drop 2.72. Mass ratio of core stage to orbit 4.15. Cross feed from outer stages to core until they burn out.

These are the numbers I came up with starting at the drop from the carrier aircraft in pounds.

GLOW                                           500,000

weight outer stages                     343,543

propellant outer stages               316,060

weight core stage at sep             156,456

propellant core stage                  118,798

mass in orbit                                  37,557

stage mass                                     12,516

payload mass                                25,140

It should be obvious that these peanut gallery numbers are speculation that I put together with a TI 30 at lunchtime. Real vehicles won’t hit these exact numbers as they are just what I got out of a calculator. You would need to round up or down or change the assumptions as you feel necessary to get something realistic. Look at he last number though, over 11 metric tons of LEO payload from three low pressure engines, two of which can be recovered after separation just as the Falcon9 first stage is recovered now. Actually simpler as the Stratolaunch will be from up range so that the outer boosters RTB (Return To Base) without needing a boost back burn. The Falcon9 is rated for more payload than this, but before shouting too loud, I suggest going back and looking at the actual loads orbited and find that every one of them to date is well under what I have speculated here.

Cost could beat the Falcon9 depending on assumptions. An aircraft to maintain instead of a launch pad. Two simple engines and small stages to refurbish before next flight against nine engines and a larger stage. An expended core stage comparable to the Falcon9 upper stage though simpler by design.

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