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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Sending the Probes

Before embarking on settlement and exploitation missions, the distant targets need to be investigated. It would be sad to spend major bucks developing one NEO only later to learn that another one has better concentrations of whatever you are interested in as well as being in a more convenient orbit. It would also be unfortunate to focus on Mars for instance only to learn that another destination suits your purpose better, and vice-versa.

One solution is to send a lot of inexpensive probes to every destination that just might be of interest to you, or anybody that might be willing to buy the information from you. Cassini was impressive, at the Saturn system, told us nothing about about anywhere else. In order to exploit and settle the solar system, we need a wide body of information about everywhere.

Advances in electronics and communications have reached the point that a 10 kilogram vehicle of 2017 is far more capable than one of the massive missions of yesteryear. The trick is keeping them affordable, and transporting them to places of interest. I suggest that the answer to both could be a fairly small rotovator. A rotovator in an eccentric orbit to Lunar distance would be at just under escape velocity at perigee. It could pick up a probe with no significant propulsion from LEO and sling it to well above escape velocity with no onboard propellant used. The rotovator could recover lost momentum with high efficiency electric propulsion. In this way, the probe uses a multi-ton propulsion system that it leaves behind for future use.

A 3 km/sec rotovator is a bridge too far for a first generation system. A solution is to find less challenging work to learn on. A thorough investigation of the Van Allen belts might be an early challenge for the adolescent rotovator/probe system. A group of small probes is carried into LEO as a secondary payload. The rotovator with just a few hundred m/sec intercept velocity picks one up and slings it to an eccentric orbit through the belts. Reboost and repeat as often as feasible.

Next step is to raise the eccentricity of the rotovator a bit more and start sending probes to GEO and Lunar orbit. Repair vehicles and tugs to GEO could be a market as well as units dedicated to nudging dead sats out of GEO into a destructive reentry orbit. The ones to Lunar orbit could get low and expendable to map with a precision only dreamed of today. Other probes could hit the L points for various reasons.

When the rotovator/probe system is more mature the eccentricity is raised again to nearly escape for the distant probes mentioned earlier. One a week departing at almost 3 km/sec above escape could explore most of the solar system with just a little gravity assist. Fifty deep space probes a year should get the job done, or more rotovators could be orbited to up the tempo. One thing that would be explored here is the fast passages to Venus and Mars as this is a much hotter velocity that the propellant limited exploration vehicles to date.

The rotovator itself should mass about a ton. The solar panels and electric propulsion about two more. Total mass being under four tons and quite compact in launch configuration, it might ride share to orbit on an F9, Atlas, or Ariane.

The rotovator experience would be valuable in itself of course. One in Lunar orbit could land loads from Earth and pick up stationary loads from the surface without burning propellant. Others at Mars, Venus, and scattered through the solar system coe the transportation hubs only dreamed of t the present time.


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A Personal Space Program

Assuming that I reached the point of controlling enough resources to do a serious space effort, how would I do it? Note that the question is, “how would I do it?” Enough resources to me means that I either own a billion dollars in disposable wealth, or have a combination of personal wealth and targeted investments that I control.

The first thing I would do is invest most of the money in a relatively safe place while investigating what to do, how to do it, and who to do it with. There are hundreds of ideas per good idea, and hundreds of good ideas per idea that would be useful to whatever I came up with. First hire would be a librarian/researcher or several to search prior art on any avenue I happened to find interesting.

I would downplay information about my available resources as much as possible. I was at a conference in the early 2000s talking to somebody when he looked over and saw John Carmack. Instantly our discussion was over as he headed that way like a dog after a rabbit. There is a reason that many wealthy people stealth their net worth. I would have no problem being quite rude to people demanding that I follow their particular dream instead of creating my own. Many of the bad decisions I have made in business and life are because I assumed that some adviser knew what they were talking about.

I would start by having the librarians look for every potential revenue source that anybody has ever suggested. Everything from helium 3 mining, to tourism, to SPS, to interstellar probes, everything. Initial investment only lasts until it runs out, then revenue is required. Sorting the possible wheat from the probable chaff would start immediately and continue as long as the program lasted. Some seemingly lucrative concepts would be duds, while some stupid schemes would be winners. Keep a constant lookout for good and bad directions. Business steering is more important than technical steering.

Second would be research into potential suppliers, partners, and organizations with similar goals. The idea is that some things will need to be done in house while some thing are better outsourced. The criteria for dealing with an outsource would be integrity as well as technical competency. An outsource that has lived on phase one SBRs for decades with never a follow up is likely to be a bad one to deal with, not definitely, but likely. On the other hand, one that has been very productive but has a reputation for shady dealing could be even worse with them using a minor variant to compete against me and possibly destroying my portion of that market.

Third would be looking into technical solutions with  the cheapest methods possible. Obviously I would prioritize my own ideas, but would attempt to be open to other concepts. On this blog I have suggested several compensating nozzle ideas, several rocket pump concepts with novel engine layouts, and a bunch of ideas with tethers, airframes, and other stuff I have little or no real world experience with. Research into prior art would be critical to this step with many ideas either busted in concept or patented  by others, either of which would be a show stopper.

Moving to hardware, I would look for the least expensive ways possible to verify concepts. It may be that I would need to hire experienced people, or it may be that it would be better to partner with a group that is already up and running. An XCOR or Masten class connection would possibly be more cost effective than starting from scratch. Modest R&D money plus a percentage of ownership would prove or disprove a lot of concepts in a short period of time. It is my opinion that a compensating nozzle would be easy and fast while boosting payload by several percent and easing combustion chamber requirements. I also believe that a very high pressure engine is possible with some of the integrated pump concepts I have suggested over the years. The idea is to find out on the cheap without committing to risky tech ideas. Several airframe ideas could be checked out with the home built aircraft community. I supply materials including engines and they build the experimental aircraft that they own after I get my information.

After getting the information from the engine and airframe people a decision is made whether to build in house or buy launches. What destinations and business opportunities exist in LEO and beyond would influence the decision as well as costs and availability of transportation. Buy from ULA or SpaceX may or may not be a good business decision. It’s not a slam dunk either way unless internal capabilities are known. My opinions about engine and airframe design may give a major advantage, or they may be the ignorant fantasies of a dreamer. It is important to know first. Beal, Branson, and Allen come to mind at the moment as smart people that have spent large sums on questionable decisions.

If everything has been done properly to this point, expenditures  should have been under $10M. The invested money should have returned more interest than that during this initial phase. The librarian/researchers should have a suite of possibilities worth looking into. Now the heavy investing starts.

Wherever the goals may be in LEO and beyond, humans will eventually be involved. On the ground, a high RPM test rig determines ability to adapt under various arm lengths, RPMs, and restraints to prevent head turns that tumble the inner ear. A partial gravity primate test rig in LEO should be early on the list of things to build. It is important to know if health can be maintained at 0.16 or 0.38 gee without an intensive exercise program. This has been neglected for far too long. If a short arm and low gee section could maintain health, it would make no sense to make bigger and riskier centrifuge wheels, and even less to crap shoot microgravity conditions for long trips. A probe to the moon with a drill and radiation detectors to determine the regolith shielding depth required for various duration missions. The drill hits a depth of ten meters with radiation detectors every few centimeters. Several locations to characterize  dosage at various depths, sun/GCR angles, and materials.  This information would be useful on Mars and LEOs as well. A greenhouse in LEO for intensive study of plants for food, oxygen, and recycling is needed.

There are a number of possibilities for in space propulsion that could save fortunes compared to current options. Depots, tethers, beams, pellet streams, and high ISP options all need to be checked out before the next steps are taken.

By now, it should be obvious which are the best available options for launch to LEO. The best available way to keep people healthy. Methods of travel beyond LEO have been narrowed down to more economical methods than conventionally available. Probes to Luna or NEOs or other planets have found useful and profitable reasons to go. It would be interesting to see what would have appeared by this time.

It is my opinion that Lunar development would be early on the list. A farside radio telescope is on several wish lists. Boots in dust tourism and exploration. Mining for volatiles and minerals useful in space.  NEOs for many reasons. Check out a few competing SPS concepts. A rotovator slinging hundreds of small probes to every destination of interest. it could be interesting.


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Quantifying Public Support

We quite often have someone suggest that some program or destination should be pursued because it has public support. Or that some project should be started to increase public support. My questions are, “what is public support exactly?” and “how does it affect the goals I think important?”

There are varying levels of public support, most of which have very little to do with accomplishing anything important in space. One level is someone choosing to watch something space related on television instead of another Friends rerun. I fail to see how this level of support generates much in the way of useful work. How many of these does it take to equal the effect of one Musk?, millions?, thousands?, tens of millions?…I would suggest x10^8 or so. How many to equal a Goff, Greason, or Carmack? IMO, the spectator public has very little to do with progress in spaceflight except occasionally voting against shutting down some jobs program, and might even be considered a negative in some of those cases.

Perhaps a level up from the couch potato in public support is the talkers like me and some of the ones I argue or discuss things with from time to time. Some of the talkers are doers, but it is hard to tell which ones unless paying real attention.  Realization of x10^7 of us to equal the effect of one of the real players is a bit humbling to us near spectators. For most of us at this level, $ome lack of ability is usually involved, even if it could be worked around with more motivation. However, moral support is often neither.

In my opinion, public support is often vastly over rated. The public support for SLS/Orion is still likely ahead of that for Falcon9Heavy, and even further ahead of Vulcan, New Glenn, or any of our other favorite launchers or launchers to be. Public support though, doesn’t seem to have much effect on launcher manufacture or dropped LOX domes.

Before Falcon 9, and especially before Falcon 1, public support for SpaceX was close enough to zero to be lost in the noise. Before New Shepard, how much for Blue Origin? How much does public support affect ULA unless there are jobs or votes involved?

I’m good with somebody proving me wrong. I would like to think my effect is more than 1/x10^7 of a real player. I am not good though with more people just asserting that the spectators/public are super important for some reason.

To me, the public support that counts is when a customer plunks their money down. Whether it is a satellite launch or a hamburger, paying customers are the ultimate measure of useful public support.

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Random Thoughts/Rocket Legos: Masten Xephr as a Vulcan SRB Replacement?

I’m sick at home today, so had extra time to think about fun technical concepts, so here’s an interesting one to think about. Right now, ULA’s plans for Vulcan include using expendable Orbital ATK GEM 63XL sold strapon boosters to enable higher performance missions, as shown below.

Vulcan Centaur Exploded View (credit ULA)

Here’s my crazy thought–what about a future upgrade replacing the expendable solid-fueled strapon boosters with fully-reusable VTVL liquid-fueled boosters?

Here’s some thoughts/considerations:

  • The boosters usually stage pretty early in the flight, just like the side boosters on Falcon Heavy, meaning that the required dV for boostback and landing are fairly modest, probably enabling all landings to be RTLS land landings.
  • Historically people have estimated that the cost per booster is in the $5-10M range. With a fully reusable booster stage, a much lower number should be possible, meaning that heavier Vulcan flights would be a lot cheaper than otherwise.
  • The GEM63XL has as best I can tell ~450klbf of liftoff thrust. That’s right in the same size range as the Masten Xephr XS-1 concept1, which has ~7x 65klbf engines last I saw.
  • A LOX/Methane stage like Xephr would have ~20% higher Isp than a solid stage, and being pump fed, even with reusability is likely similar or better pmf, meaning there’s a good chance you could still provide the same impulse to the Vulcan stage while maintaining enough prop for RTLS maneuvers.
  • I’m a bigger fan of VTVL powered landing than SMART reuse, but for missions like this, the core booster would be going so fast at staging that recovering just the engines might not be a totally awful approach.
  • It might be possible to design the Xephr boosters to serve both ULA Vulcan strapon booster markets, as well as flying their own expendable or fully-reusable upper stage (for much smaller LEO payloads–maybe in the 1mT class). The strapon booster market would mean you’d want to have a small fleet of 8-10 of these boosters, and ULA would only be using them a few times a year, meaning that the rest of the time you could have them flying smaller payloads such as propellant (enabling lower cost ULA distribute launch), megaconstellation satellites, or cargo deliveries to space facilities.
  • The current Xephr concept already used parallel staging of the upper stage, which would be attached via struts much like strapons are attached onto a core stage. Would it be possible to design the struts to work for both applications?

    Masten’s XS-1 Concept Xephr (credit Masten)

There are a few challenges that would need to be addressed to make this work though:

  • Solids don’t have a lot of propellant on them compared to a liquid fueled first stage like Xephr. GEM63XL has a GLOW of ~117klb, in spite of having 450klbf of liftoff thrust. It might be possible to partially load the stage for Vulcan boost applications to provide more thrust to the main vehicle. Though this will require some optimization and analysis to see how best to balance things.
  • Another challenge is that Xephr is probably more squat than the planned GEM63XLs. Right now some of the pictures show the boosters evenly distributed around the stage, but others have them clustered tightly together on both sides. It would be relatively easy at this point to change the spacing on the boosters, but will become significantly more expensive to change down the road.
  • Another aspect of the fine aspect ratio of the solids relative to the Xephr stage is that it might force you to a higher aspect ratio booster than Masten would ideally like, in order to keep the attachment points the same. Though the LOX/Methane stage is lower density than a solid so it might still be tall enough, just wider. Once again, more analysis and optimization would need to be run.

All told, it’s an interesting idea that would be worth running some numbers on. None of the challenges are obvious show-stoppers, but the devil is in the details. This concept would make Vulcan more competitive down the road, and could potentially have a lot of additional synergies between the two companies. This also would provide a company like Masten with an existing anchor customer for a Xephr-class reusable first stage. Rockets aren’t Legos, but during the early design phase, there’s a lot more flexibility to easily accommodate crazy ideas like this.

Posted in Launch Vehicles, MSS, Random Thoughts, Rocket Legos, ULA | 7 Comments