Suborbital VS Orbital

I did a post on this a few years back, but couldn’t find it to repost.

A commentor in response to one of Rand Simbergs’ articles brought up (again) the old orbital is 8 times the velocity of suborbital and therefore 64 times as hard because energy goes as the square of velocity. Where to begin arguing this again?

The argument was that suborbital is Mach three vs orbital being over Mach twenty-four. Mach three won’t get you to space. 900 meters per second (~Mach 3) vertical velocity will get you 90 seconds of climb at an average of 450 meters per second, or about 40.5 kilometers of altitude. That doesn’t include drag, gravity losses during acceleration or engine back pressure losses. Mach 4 gets you 72 kilometers if you are in vacuum the whole time. It would take nearly Mach 5 to reach the Von Karmin line from sea level if you were in vacuum the whole way. 1,430 meters per second is considerably more than the 900 meters per second implied by the comment.

That was a straight up and down in vacuum from sea level. The flight doesn’t start in vacuum. Back pressure losses on a rocket engine gives 5-20% less performance at sea level than in vacuum. That is a major Isp hit on performance to a vehicle with a finite propellant capacity and facing exponential weight gain for excess mass. That 5-20% more propellant for a given thrust must be lifted by even more propellant. That extra propellant requires a larger airframe and engine capacity. The larger engine and airframe requires more propellant and so on. A suborbital vehicle has just as much back pressure loss as an orbital vehicle .

The vehicle has drag while it is accelerating toward space. The drag costs more propellant equals more engine and airframe, equals even more propellant and so on. If too much acceleration is done too early drag goes up by several more factors which would cost more propellant etc… Another aspect of the drag is heating if too much time is spent at high mach during the climb in the atmosphere. Thermal protection can get up there fast with a poor design. A suborbital vehicle has just as much drag loss in the climb out as an orbital vehicle.

There are gravity losses during the climb out. A suborbital vehicle has just as much drag loss as an orbital vehicle.

Actual mass ratios for suborbital above the Von Karmin line tend to be in the 3 to 4 range. If Mach 3 in vacuum was the whole story, then mass ratios would be in the 1.3 to 1.5 range. Orbital mass ratios tend to be in the 10 to 20 range depending on propellant choices and engine efficiency. The difference in mass ratios is about 4 to 5 with similar propellants. That is undeniably a major difference and order of difficulty. Just not 64 times the difficulty, especially with staging.

Life support is clearly different for manned vehicles. Bottled air for 30 minutes is different than 30 days for one. Food, toilet facilities, and creature comforts are quite different as well. This particular aspect may well be 64 times as hard. I doubt it, but it is possible.

Acceleration couches, controls, and displays will be about the same. More propellant for the RCS with the same number of thrusters is not that much more difficult. Communications will be more complex if the mission requires, though not an order of magnitude, and certainly not 64 times as hard.

Unmanned vehicle payloads have even less need for the 64 times as expensive meme. The energy supply is about the only thing that is clearly in a different league, though solar panels are getting to be quite well known even there.

Look at the historical record for more data. Working backwards from Elons’ billion investment in orbit with the 64 times as hard, any suborbital company spending more than 15 million should have been providing reliable service. Count for yourself the ones that have spent over 15 million and still don’t have an operational vehicle.

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Healthy Industries vs. Monocultures

One of the things I’ve believed for a long time is that for the NewSpace industry to be successful and healthy, that we need to see multiple providers and customers for the various goods and services in the industry. One needs look no further than the situation with Aerojet/Rocketdyne and ULA to realize how unhealthy monopoly/monopsony arrangements can be. In an ideal, healthy industry, we’d see several competitive low-cost launch companies offering a range of launch services, multiple companies building in-space facilities like hotels, stations, unmanned free-flyers, and depots, etc.

Having multiple providers and multiple customers is good for many reasons:

  1. Resiliency: If you have multiple providers and customers, problems with one entity don’t necessarily grind the industry to a halt. An example of this was how badly ISS was impacted by the Shuttle fleet stand-down post Columbia. There was also the close-call with Soyuz a year or two ago, where it wasn’t clear if they were going to have to stand-down crew deliveries to the station. On the customer side, technologies and consumer preferences change over time, so having a wide range of customers means that if one particular application stops being as viable, it doesn’t take down the industry with it. In general, more providers and more customers makes any one entity less critical, and makes the industry more robust.
  2. Competition: Having multiple providers to chose from often helps keep an industry innovating, and keeps costs lower than if there were just one provider. Think how good it was for computer users to have both AMD and Intel competing with each other for much of the past 20 years. Would Intel have moved as aggressively at innovating, and would costs have been as low for consumers without them?
  3. Diversity and Specialization: One size doesn’t fit all, and the more firms there are in an industry, the more likely you are to see specialization leading to better solutions for people with different needs.

The interested reader could probably think of other reasons why it’s good to have a range of providers.

Now admittedly, while having a range of providers and a range of customers is ideal, not all industries are large enough to support that level of diversity. Some tend towards “natural monopolies”.  I think at current launch costs, reasonable people can differ on if space launch falls into that category or not. But I think we can all agree we’d like to see a space industry that has a big enough pie to make that sort of healthy diversity possible.

Why am I bringing this all up? Mostly because I’ve been noticing an unhealthy trend towards monoculturalism/”Highlander Syndrome” among many in the NewSpace community. You see this a lot in twitter commenters who seem to think the government should just ditch ULA and give all their flights to SpaceX, or the anger over why NASA picked Boeing as well for a CCtCap award even though they were more expensive than SpaceX. You see this in how people only ever talk about Bigelow Aerospace for in-space habitats. You see this with people badmouthing Masten or Blue Origin and saying that they should give up now because obviously SpaceX is better.Now, I actually like SpaceX and Bigelow a lot, have a ton of respect for what Elon’s team has managed to do over the years, and really genuinely want to see both of those companies wildly successful. But I want to see others successful too. In many cases there isn’t a huge amount I can actively do, since Altius isn’t very involved anymore on the launch side of things, so my support may be limited to trying to cheer on progress by not just SpaceX, but ULA, and Blue Origin as well. I do what I can to put ideas out there that can benefit everyone, and to work on technologies at Altius that can help more than one provider be competitive. I’ve always preferred to run a shop with a reputation for being on friendly terms with everyone as much as possible.Anyhow, I hope others find these thoughts useful.

Posted in Bigelow Aerospace, Commercial Crew, Commercial Space, Launch Vehicles, Space Policy, SpaceX | 17 Comments

Capsule Que Pasa

I was jolted a bit when I read the amounts and requirements for commercial crew last week. Not that Boeing got more than SpaceX, but rather that $6.8B is budgeted for a developing a couple of commercial capsules to fly on existing launchers. Boeing’s $4.2B doesn’t bother me as it should be expected of traditional contractors, SpaceX’s $2.6B does.

I am not going to suggest that human transport vehicles to LEO should be trivial or cheap. I do suggest that SpaceX requiring $2.6B to finish development of  a capsule that is supposedly almost ready to go, even including the maximum 7 flights, is well out of step with the reported development costs of that company. It has been said quite often that SpaceX developed the Falcon 1, Falcon 9, and Dragon 1 for under a billion dollars.

My question is, why should capsule development cost on the order of triple that of an entire Falcon 9 launch vehicle? This is not to trivialize the work to be done, or the paperwork involved, but seriously asking what is so complicated and expensive inside that vehicle that drives the cost far beyond that of entire launch vehicle families?

This post might be considered snark. That is not the intention. It is a serious puzzle that affects development of the solar system. A puzzle that I can’t yet understand. I am not real interested in the standard NASA bashing response of how the government drives up costs that we have all rehashed a hundred times. I am interested in any solid information on the hardware/software cost drivers of this bus without a main engine.

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CCtCap and Blue Origin/ULA Article on SST

I just did a guest post on the Sic Semper Tyrannis blog on the CCtCap and Blue Origin/ULA announcements. They’re aimed at people less familiar with space news than most Selenian Boondocks readers, but I figured I’d link to it so I can say I’ve done at least one post on this blog this month… :-)

Posted in Administrivia, Commercial Crew, SpaceX | Leave a comment

VTSL Vehicle

I got into a discussion the other day about the Blue Origin/SpaceX barge landing issue. I suggested that it was very difficult to write such a comprehensive patent that there was no way to design around the restrictions. As an offhand illustration, I suggested that landing on a hovercraft was unlikely to be covered by a barge landing patent. Being called on it as an idea instead of mere talking point, I did a quick search to refute the point of hovercraft not having the capacity to handle the weight.

The two craft that remembered from TV documentaries I found in minutes. The Marine Corp LCAC is the Landing Craft Air Cushion and is rated for 60-75 tons and 40 knots speed. The operational radius apparently 200 miles. The English channel ferries that were retired after the Chunnel opened for business were rated for 52 cars and 60 mph. It is likely that there are hovercraft in these performance ranges available for sale in the world without having to build your own.

The point I couldn’t address was whether hovercraft of any size would be stable enough for a landing at sea. I didn’t find any definitive source on the relative stability of these vessels compared to anything else.   In order to raise this thought to at least idea level I decided to assume that they could not be stable enough for the conventional landing we tend to think of.

The idea of any landing is to get the vehicle down without any damage whatsoever. This covers everything from model airplanes and rockets, to airliners, VTVLs,  and Space Shuttles. Even a hovercraft like the LCAC capable of carrying an Abrahms tank wouldn’t seem to have the excess capacity for a full landing platform capable of landing a rocket stage and securing it against the rolling and pitching from even a fairly mild sea state. Horizontal landings of a serious rocket stage a la aircraft carriers is so absurd as to defy serious thought.  I came up with the slant landing technique, as demonstrated by Masten Space Systems during the Lunar Lander Challenge.

So Vertical Take off and Slant Landing is VTSL. When Masten was testing vehicles in the Mojave wind, sometimes the vertical landing vehicles would be, I’ve read, leaning 20-40 degrees from the vertical to compensate for the extremely high winds for precision landings. An LCAC at high speed will produce relative winds of as much as 40 knots  (46mph,I think) plus the natural wind component for a total wind across  the deck of 50-70 mph. A stage landing on the fast moving vehicle will be leaning into the wind just as the Masten vehicles did. A net on a pair of pivoting booms could match the angle of the incoming stage to catch it at near zero relative velocity in a three axis capture.

LCAC Lander

The whole length of the vehicle could be soft netted simultaneously to avoid any ten story structures falling to the deck. As soon as netting secured is confirmed the hydraulics retract to the horizontal for the trip home. Being a hovercraft, the destination is inside the stage integration building instead of the barge dock. It seems likely that the listed 200 mile range of the LCAC is fully loaded with dangerous people and their tools. The hovercraft going for a stage capture could make the trip out with bladder tanks in the cargo area for a massive range extension

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Asymmetrical Payload Boost

Paul451 made a suggestion on the last post that triggered a thought on boosting payloads on many current vehicles at a reasonable cost. I claim 50% credit for this concept with Paul getting the rest.

He suggested that the tanks on the last post should be thin walled balloon tanks with a structural truss from the thrust structure of the first stage to the second stage. This would allow modular stacking and swap outs with minimum pain. It would also allow greater flexibility in modifying vehicles for different missions. The thin wall tanks were to compensate for the mass of the structural truss as well as for cost reasons.

My quibble was with the truss mass, though the ability to go with cheaper and lighter tanks appealed greatly. My thought based on his thought started with using an existing LV for the structural truss with the thin wall tanks attached to the sides much like in the previous post. Then SRBs are attached to the outsides of the strap on tanks. My squeamishness about SRBs is not shared by several of the experienced companies that actually launch rockets.


Several companies use strap on SRBs as a matter of course. The Atlas sometimes uses a single SRB, which answers many of the concerns expressed in comments about asymmetrical loads or thrust vectors expressed in the previous post. A variety of existing and well known SRBs are available to launch companies right now, as opposed to the liquid engines that I would prefer. SRBs are frequently mentioned as relatively inexpensive engines. My qualms have to do with the unfortunate failure modes.

If two tanks are strapped onto an LV with direct feed to the core engines, the core will be far too overloaded to leave the ground. Add enough SRBs to the outside of the strap on tanks and the vehicle will have the TW to launch. At SRB burn out, the core vehicle’s engines will be at full vacuum thrust. A lofted trajectory will allow the total vehicle to have a TW of less than one including the strap on tanks. The vehicle first stage mass ratio from Mach 3-4 and 25 miles could be as much as double that of a standard core vehicle doing a ground launch. Payload could triple or so.

An Atlas 5 with this modification could match the theoretical payload of an Atlas 5 heavy with the expenditure of one RD170 instead of three.  Other vehicles run by companies not squeamish about SRBs could get similar results.

As pointed out by Peter in the previous post, it is not required to stop at two strap on tanks as the Saturn I for instance had multiple parallel tanks.

In the event of SRB cato, the strap on tanks act as shrapnel catchers. This might make it possible for standard LVs to use SRB boosters with less concern about losing the core vehicle and payload. The payload might make it into LEO instead of GEO after losing the extra boost and propellant.  A tug could be designed and tasked to rescue these stranded vehicles and take them to their intended destination.


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Asymmetrical LV

There are several limitations on the ability to expand a launch vehicle past certain sizes. One of them is tank diameter. On the smaller launchers, diameter limits might be dictated by available pipe sizes. A step up from there and tank diameter might be limited by available tooling. A couple of steps up from there and ground transport becomes an issue. Too large and it becomes somewhere between inconvenient and prohibitively expensive to transport from factory to launch site. Another limitation is height and fineness ratio. A launch vehicle gets into problems when the stack length is too large a multiple of tank diameter. 8″ irrigation tubing might be a good basis for a 10′ rocket, but gets into trouble before it reaches 20′. By the same token, the Atlases, Falcons, and similar vehicles are probably very close to the limits of length in relation to diameter. The standard build for a launch vehicle is, starting from the bottom, engines, fuel tank, inter tank structure or common bulkhead, LO2 tank, inter stage adapter, engine, fuel tank, inter tank structure or common bulkhead, LO2 tank, and payload. This is all in one long skinny cylinder except for a hammerhead shroud. To make the launch vehicle larger requires either more diameter, more length, or both, with the  manufacturing and transport problems from the diameter increase, or the structural problems from the length increase. There might be a way to double the size of a given vehicle class while holding the costs and other problems down. This idea is to build a vehicle that is asymmetrical around existing tooling. Also use a modular assembly technique to avoid both transport problems and the necessity of new tooling or construction techniques. Asymetrical LV   I still don’t have a computer that lets me draw cartoons all that well. The sketch is two possibilities for the vehicle concept. A stretched LOX tank built on existing tooling  that is as long as the original entire first stage. A stretched Kerosene tank proportionate to the LOX tank also built on existing tooling. These tanks are trucked separately to the launch site where they are clamped together along with the thrust structure. On the left the sketch has the helium tanks, avionics and such in the space above the shorter Kerosene tank with the second stage above the center line of the vehicle. The figure on the right has the second stage nested above the Kerosene tank with the helium tanks and such moved elsewhere. If this concept is feasible, a first stage could effectively double in size without causing problems in manufacturing and ground transport. Engines would double in number, but dome tank ends would not. The increased cost of the larger vehicle would be dominated by the engines. Eliminating the inter tank structures would eliminate a place for fumes to gather and possibly cause problems. The tank connectors could easily be lighter and cheaper than the normal inter tank structure. There would be no place at all for potentially explosive fumes to gather, which means that a leaking tank might be less of a problem. By going modular, any problem section could be swapped out with relatively little effort. The four modules being LOX tank, Fuel tank, thrust structure, and second stage. Two of these units could be flown together in a quad layout. Three of these units could act as boosters/first stage for a conventional  vehicle centered between them in the seven tank hexagon layout.

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SpaceX and Sea Launch

Another speculative thought. Suppose we have all been assuming that Falcons will try to land on a barge at sea or accept the payload penalty of RTLS, when all the tests have actually been in support of a launch at sea to a land recovery.

Sea Launch has the sea going craft to launch large rockets at sea. They are also, according to rumors, not making quite as much money as the investors would prefer. It seems possible that they might be at least semi-motivated to sell off the under performing launch assets.

What if the real intention of SpaceX is to acquire those assets at bargain prices for use in house. Launch a few hundred miles at sea from Vandenburg for a feet dry landing there, with the actual launch location dictated by the desired launch azimuth. The first stage would never have an IIP intersecting property on land, while the second stage would have an IIP that moved fast enough to minimize theoretical injury and property damage probabilities. A day out to launch and a day back. Twice a week seems possible.

From Brownsville the trip would be even shorter. A quick run to a point that gave the right launch  azimuth and distance from the cape for a Falcon recovery there. Possibly a day trip with the launch frequency that implies if the business develops.


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Falcon III H (R)

The vehicle SpaceX lost the other day has been described as a Falcon IX R with three engines. It is a bit intriguing to speculate on the purpose of three engines as opposed to the nine of the full up stage, or the one of the Grasshopper I.

The first and most likely thought is that more than one and less than nine are needed for the test flight profile. So three are required to do the job, but there is no financial sense in tying up, and possibly losing, six additional engines that are not required for this particular test program. The problem with that explanation for us in the peanut gallery is that it is boring and gives us nothing to speculate about.

An explanation that I find more fun and interesting is that there might be a financial and technical case for a three engine Falcon. A shortening of the stack for the lighter vehicle would produce a lower profile for a possible reusable version. Landing on a barge at sea would be with a vehicle with far less bending moments that a full Falcon IX stage. It seems possible that such a vehicle could land (barge) in a much heavier sea state than the larger vehicle. If that is a actual possibility, then Falcon III boosters could be attached to a Falcon IX stack with very low costs per mission if the mini boosters could be reused quickly and often.

Even a first take on such an arrangement yields some suggestive possibilities. A 66% increase in take off thrust would allow as much as 66% more take off mass and slightly more than that increase in payload with the additional staging event. With cross-feed, the Falcon III stages would drop off at under a minute and a half, barely supersonic, and fairly close to the launch site for a quick booster RTLS. The fully fueled Falcon IX would be in near vacuum conditions by that time with the considerable gain in Isp compared to a ground launch. A payload gain of over 2/3 for minimal cost could not be ignored if technically feasible.

For flights where the basic Falcon IX has enough performance to do the primary mission, but not enough for any recovery options, the Falcon III boosters could up the propellant reserve to allow core stage recovery. Small, quick turn around boosters enabling the recovery of a core for certain missions would be a nearly slam dunk decision if technically feasible.

For some Falcon IX missions, a Falcon III heavy could possibly deliver a bit more payload with the same number of engines. The engines being one of the major expense items could make not requiring more of them a sound business decision if the staging events become safe and routine enough. The extra payload would come from the same nine engines powering the stack for the first couple of minute as the normal Falcon IX, after which the two boosters drop off with the consequent dead mass reduction for the remaining stage. The remaining Falcon III would have the same velocity and remaining propellant as the base Falcon IX at this point, but would be boosting 1/3 of the engine and tank mass along with the upper stage and payload.

Last thought is on the difficulty of RTLS of stages entering from far down range. A barge landing is often mentioned, virtually always coupled with the words “good sea state” in some manner. This means that barge recovery is permanently dependent on  the sea not being too rough.  Some missions could be delayed by days or weeks to let the waves subside from a previous storm. Some whole seasons could be off limits if the recovery is sensitive enough.

The helicopter recovery I suggested a couple of years back might bear revisiting for lighter stages. The major objection to snagging a Falcon IX core in the air with a helicopter and flying it back to launch site was the excessive weight of the stage. A Falcon III stage might be air recoverable in a way the the Falcon IX stage could not be.


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Andrew Peregrin Goff

There are probably less than 5 people in the world who a) care about my family life, b) don’t follow me on twitter, c) don’t follow Tiffany on Facebook, d) didn’t get an email about this already, but e) do read this blog. So for those of you who fit in that category, I’d like to announce the birth of our son Andrew Peregrin Goff. Andrew is our fifth son after Jarom (deceased), Jonathan (9yrs old), James (7), and Peter (5).

Andrew was born this Wednesday evening at 5:20pm in Boulder. He was two weeks early (but still technically full-term), 6lb 11oz (3.03kg), and 19in (48cm) long. He’s doing great, and both he and his mother are home as of this afternoon.

If you’re wondering about the name, Andrew is my middle name. We also have several friends with Andrew as a first or middle name. It also fits with Peter, James, and Jonny (sort of) as a sort of semi-intentional Apostolic naming theme. We debated a lot of middle names–Andrew is somewhat tough to find good middle names to go with. Our two finalists were Sheridan after Tiff’s dad, and Peregrin (yes after Pippin from Lord of the Rings). We ended up going with Peregrin in the end. The good news is that with a middle name that can be shortened to Pippin, he’s set whether he’s a LOTR-fan nerd like his dad, or whether he gets into basketball…

After having picked the names, we found out that Andrew means “manly or brave”, and Peregrin (which amusingly enough was the word of the day on today) has connotations of wanderer, traveler, etc.

His current nicknames are spud, french fry, burrito, and self-eating-burrito.

Here are some pictures of baby Andrew:


Posted in Family | 10 Comments