Related to power satellites (and help request)
Keith Henson
concerns about LNG/LOX and a test they were going to run. LNG/LOX is
not something you want to mix on the pad or anywhere else. It is
about twice as energetic as TNT and is as sensitive to shock as
nitroglycerine.
If there was a bulkhead failure, and a SpaceX booster mixed the whole
LNG/LOX load, the bang would be about half the Hiroshima blast. I
can't blame the FAA for being concerned. Even if it is a remote
possibility, the consequences for the launch complex are dire.
There was, I realized, a solution: with the LOX on top, put an open
container of triethylaluminum (TEA) in the headspace of the LNG tank.
If the bulkhead fails, the TEA ignites, the booster splits open, and
there is a huge fire, but no detonation. I filed for a patent and it
seems that causing a fire to prevent a rocket explosion was a new
idea. My patent lawyer recently informed me that the patent office
allowed it. It took only a few months. I have 6 earlier patents and
I don't think any of them took less than a year or two.
This is connected to the Power Satellite Economics list in that the
StarShip is the current front-runner for a low enough lift cost to
make power from space competitive. It is less connected to arocket,
but I thought the list members might be amused by what a post there
kicked off.
Why do I need help? Despite being a founder of the L5 Society (almost
5 decades ago) and moderating PSE, I don't have close contacts with
SpaceX or Blue Origin. They are the ones who will be the most
affected by whatever the FAA decides to do based on the LNG/LOX tests
they are running at the Dugway Proving Grounds this summer. If the
FAA raises objections to LNG/LOX, they might find it useful to have a
mitigating solution in hand.
(The Chinese might also use it. But I doubt they would license it and
I have no close Chinese rocket contacts either.)
If any of the list readers have high-level contacts--particularly
design people--with SpaceX or Blue Origin, please point them to me or
send me a pointer. Or, if you want to be involved more deeply, talk
to me about a commission.
Keith Henson
https://en.wikipedia.org/wiki/L5_Society
PS Feel free to send this to other lists or people.
Keith
Bryan Zetlen
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james...@aol.com
Let's review what is known or suspected.
1. I have previously raised with the FAA the point about the possible explosive potential of the second stage, following some inflight failure (engine explosion, separation failure, guidance failure, fabrication or assembly error, et cetera) impacting at hypersonic speeds creating the instant vaporization and mixing of the 2,600 tons of propellant. This will result in an explosion not a deflagration as Keith's idea seeks to achieve. Under this failure circumstance, the TEA does nothing as the KE of the crash assures vaporization and mixing. Does the KEA assure ignition?
2. The overall payload mass to GTOW ratio is at best only 3 percent. The payload to total propellant mass ratio is at best only 3.2 percent. What mass of TEA and hardware would be needed to reliably (99 percent confidence) prevent a propellant explosion under possible unanticipated, accidental, or intentional failure initiation circumstances?
3. TEA apparently spontaneously ignites with air. I do not see how an "open container of TEA" is feasible. Further, my limited understanding of the chemistry suggests that TEA is likely sensitive to contamination initiating ignition.
4. How and when would the TEA be loaded onto the vehicle. On the pad? Adding a pyrophoric liquid to the propellant loading sequence would certainly add substantial complexity. Further, how ALL TEA would be assuredly removed after a launch scrub is another consideration.
5. Switching the position of the fuel and oxidizer tanks is a substantial design change that would likely take the design back to stage 1.
6. The existence of apparently known FAA concerns regarding such a fundamental safety issue with the Starship design highlights the failure of the current "just let them do their thing" approach to advancing American spaceflight capabilities. This political failure is especially evident given the "let's just go big" solution to the low net Isp of the propellant choices. The goal with "going big" is to minimize the non-scalable dry weight fraction of the flight system in favor of increasing the payload fraction.
7. My experience at WPAFB suggests that this design concept would there have been rejected outright for what appears to me to be obvious design inadequacies. The single bulkhead, if this in fact the case, is just one. A substantially welded thin structure would have been another. The initial proposition that no substantial TPS would be needed was another. Finally, the massive number of rocket engines is another. And then, there would be the hypersonic inflight crash issue mentioned above as well as the inherent range safety issues raised by such a large vehicle.
Rather than a well-developed strategy to build a highly-integrated national astrologistics infrastructure reaching out to the Moon, we are left with two ego-driven mega billionaires striving to make a name for themselves in the history books. As such considerations/concerns as these are raised, things are not working out as they would appear to wish, eventually leaving the Air Force—not the Space Force or NASA—to pick up the pieces. The Air Force understands proper vehicle design and development and logistics to support forward operations.
Mike Snead, PE
Keith Henson
>
> Keith, I applaud your creativity in seeking a solution to this dilemma.
>
> Let's review what is known or suspected.
>
> 1. I have previously raised with the FAA the point about the possible explosive potential of the second stage, following some inflight failure (engine explosion, separation failure, guidance failure, fabrication or assembly error, et cetera) impacting at hypersonic speeds creating the instant vaporization and mixing of the 2,600 tons of propellant. This will result in an explosion not a deflagration as Keith's idea seeks to achieve. Under this failure circumstance, the TEA does nothing as the KE of the crash assures vaporization and mixing. Does the KEA assure ignition?
fire. But I presume the flight termination system would activate long
before an impact
> 2. The overall payload mass to GTOW ratio is at best only 3 percent. The payload to total propellant mass ratio is at best only 3.2 percent. What mass of TEA and hardware would be needed to reliably (99 percent confidence) prevent a propellant explosion under possible unanticipated, accidental, or intentional failure initiation circumstances?
> 3. TEA apparently spontaneously ignites with air. I do not see how an "open container of TEA" is feasible. Further, my limited understanding of the chemistry suggests that TEA is likely sensitive to contamination initiating ignition.
tank. If it lights off, then oxygen is leaking in.
> 4. How and when would the TEA be loaded onto the vehicle. On the pad? Adding a pyrophoric liquid to the propellant loading sequence would certainly add substantial complexity. Further, how ALL TEA would be assuredly removed after a launch scrub is another consideration.
letting any air into the fuel tank
> 5. Switching the position of the fuel and oxidizer tanks is a substantial design change that would likely take the design back to stage 1.
force the LOX lines to run outside the LNG tank. This messes with the
aerodynamics, but the booster does not go fast so it may not matter.
> 6. The existence of apparently known FAA concerns regarding such a fundamental safety issue with the Starship design highlights the failure of the current "just let them do their thing" approach to advancing American spaceflight capabilities. This political failure is especially evident given the "let's just go big" solution to the low net Isp of the propellant choices. The goal with "going big" is to minimize the non-scalable dry weight fraction of the flight system in favor of increasing the payload fraction.
>
> 7. My experience at WPAFB suggests that this design concept would there have been rejected outright for what appears to me to be obvious design inadequacies. The single bulkhead, if this in fact the case,
> is just one. A substantially welded thin structure would have been another. The initial proposition that no substantial TPS would be needed was another. Finally, the massive number of rocket engines is another.
tolerate one or two failures.
> And then, there would be the hypersonic inflight crash issue mentioned above as well as the inherent range safety issues raised by such a large vehicle.
>
> Rather than a well-developed strategy to build a highly-integrated national astrologistics infrastructure reaching out to the Moon, we are left with two ego-driven mega billionaires striving to make a name for themselves in the history books.
prospects to get into space.
> As such considerations/concerns as these are raised, things are not working out as they would appear to wish, eventually leaving the Air Force—not the Space Force or NASA—to pick up the pieces. The Air Force understands proper vehicle design and development and logistics to support forward operations.
direction.
Keith
Keith Lofstrom
...
> 1 ... possible explosive potential of the second stage ...
...
> 7 ... obvious design inadequacies. The single bulkhead ...
I also applaud Keith Henson's exploration of alternatives,
but "LOX on top" seems structurally costly.
CH4 + 2 O2 -> CO2 + 2 H2O
16 amu + 64 amu -> 44 amu + 36 amu
0.45 kg/l for LCH4 and 1.14 kg/l for LOX, so the
volume ratio is:
0.45/16 to 1.14/64 or 0.028 to 0.018 or
1.58 Methane volume to 1 to LOX volume
Methane boils at 112K, LOX boils at 90K
At stochiometric ratios, the oxidizer weights four times
as much as the fuel, though the fuel takes up 1.6 times
the volume. Stacking a smaller heavier LOX tank on top
of a larger lighter CH4 tank requires more longitudinal
strength and mass around the lower methane tank.
There might be a TINY thermal advantage keeping "warmer"
liquid methane nearer the hot engines during flight, but
I imagine the important consideration is boiloff on the
pad awaiting launch, not internal thermal isolation
during flight. I also imagine methane leakage on the
pad is less risky if it is farther above the igniting
engines.
----
I am NOT a steely-eyed missileman like James Snead, just a
putz with a calculator and google, but even putzes manage
to push the right calculator keys from time to time.
Anyway, I got to the same "nice try, but no" by a
different path than James.
Innovative engineering requires a shit-ton of nice
tries followed by rigorous idea infanticide - my "bright
idea" failure list is ten times longer than my "good
enough to try" list, which in turn is ten times longer
than my "customers actually pay for this" list, which is
ten times longer than my "others steal my ideas" list.
Thank goodness that there are 8 billion of us, yielding
a few surprisingly good new ideas worth stealing per year.
According to my academic citations and investors and
customers, I've implemented one sorta-good idea in my life,
so I've been a winner in the brainfart emission game ...
after a swimming-pool-full of perspiration.
----
The failed idea I'm most proud of ( launchloop.com,
16 kWh/kg to escape, $1/kg at Oregon's 6.44 cents per kWh
industrial electricity rate) hasn't progressed, but then,
neither has the 3 million tonnes/year launch market that
justifies a minimum-length (2500 km) launch loop.
That said, the US produced perhaps 5000 kilometers of
nose-to-tail bomber during World War 2, with 4 meter
rather than 10 centimeter cross section. Launch loops
will happen when we find an excuse to bomb the Moon. :-)
Keith L.
--
Keith Lofstrom kei...@keithl.com
Gary Barnhard
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Bryan Zetlen
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james...@aol.com
My response is lengthy, so I apologize for that.
1. My concern with the issue of a hypersonic impact goes back to the NASP program when I was looking at how to conduct the flight test program with speeds up to Mach 12. The NASP vehicle would not have a destruct system. (Such systems are simply someone's workaround for a poorly designed system in order to convince the person "signing off" on the flight test that that person would not likely be held responsible for letting the system launch.)
I was told by NASA/KSC that on impact at Mach 6+, it is likely that the kinetic energy of the impact will near instantly vaporize and mix the fuel and oxidizer. Since these are present in the propellant tanks at around optimum ratios, the mixture constitutes an explosive mixture. (The oxygen in the air is a minor contributor, I suspect.) Obviously, the thermal energy from the impact will ignite this explosive mixture.
For the second stage of the Starship, I suspect that the 1200 tons of propellant would detonate something comparable to what happened in Beirut several years ago.
https://youtu.be/93tV6-0Ugwk?si=D4jL5iIUAr7qB8fC
Is this a global range safety issue? I think so. If the FAA signs off on Starship launches, they then bear the responsibility for non-involved harm or damage.
2. Is the presumption that a destruct device would prevent this from happening valid? I think this is an unprovable presumption. Destruct systems are subject to failures, faults, intentional sabotage, or hacking just as any other system. Imagine a hypersonic impact and explosion of the magnitude of Beirut happening after the destruct system failed. How would the cause be determined? Who would bear the legal consequences? Elon Musk? The FAA head? The same sabotage that prevents the second stage from operating could also prevent the destruct system from operating, couldn't it?
Remember that the Starship is supposed to carry people. Are these versions also to use destruct systems? If not, what is the justification for protecting lives onboard from accidental harm due to a destruct system failure while not protecting lives on the ground from harm?
3. I think the further assumptions explained on how TEA would be installed and used essentially show this to be an unworkable solution. In the military, great caution is taken with the use of anything that triggers an explosion, such as fuses for bombs. For munitions, substantial testing is performed before a new munition is certified on each aircraft to carry it.
I cannot imagine how such a certification program, sufficient to eliminate a Starship explosion as a hazard, could be carried out using TEA. I don't see simulated testing achieving this.
4. I did not know about the fuel line running through the LOX tank. Again, this would have been rejected as a design consideration. In my view, this is just poor engineering based on an assumption of being able to manufacture and install a "perfect" component. In my opinion, this is an example of how not to design a spaceflight system. There are many such considerations that enter into the mix of concepts that are proposed and then weeded out during the conceptual design phase.
I've included an illustration of the 1970s Boeing RASV, promoted by the Boeing president at the time as a suitable new reusable launch system. Boeing was trying to make use of the new SSME engine's improved Isp to "close" the conceptual design of the quasi-SSTO RASV manned spaceflight system.
During the WPAFB TAV concept evaluations in 1984, Boeing proposed this as one of three TAV concepts. It had received wide publicity. My job was to lead the WPAFB formal tech eval of the proposed TAV designs. I discussed the RASV design with Dr. Jack Lincoln, the Air Force's lead for structural integrity—a fundamental part of airworthiness. (He was also my technical boss in my home office.)
A key to Boeing being able to "close" the design—meaning achieve orbit—was the use of a honeycomb panel concept for the airframe. At that time, honeycomb was considered to be a very good weight saving structural design. It was used in the XB-70, for example, as well as parts of other aircraft. However, experience showed that it had a major problem. This was that if the outer surface was damaged causing a break in the continuity of the surface, water from rain or humidity would accumulate in the cell. When heated by supersonic flight or when frozen by high altitude flight, the cell would rupture, spreading the damage internally and potentially causing inflight delamination of the skins. The use of cryogenic propellants in the RASV meant that any flaw in the surface would "suck" in air/water that would liquefy due to the cryogenic propellants (LH2 and LOX). On reentry, the trapped liquid/solid would boil, causing structural damage/skin delamination threatening the integrity of the airframe. The flaw size could be so small as to be essentially invisible to causal walk-around inspection. We believed that it would be very difficult to maintain a RASV in an airworthy condition. In other words, it would be a "hangar queen".
We also had substantial reservations with the overall RASV "hot structures" approach that was similar to what Starship was proposed to use. Hot structures are vey difficult to design and, especially, to ground test as part of validating the structural integrity of the airframe. This was a major consideration in the NASP program - how to test the airframe? This consideration flows back into key early decisions on what materials to use, what structural concepts to use, what flight profiles to fly, what inspection and repair methods to use, et cetera.
These are just some of the issues we identified with the RASV which was why it was not selected to use as a TAV baseline design.
5. Jet and rocket engines are very complex. Both use rotating hardware operating at extreme temperatures, pressures, and fluid-dynamic and centrifugal loads. Engine primary structure necessarily operates very close to the maximum permitted structural limits in order to achieve the desired level of performance. For this reason, validating the integrity of the engine is critical.
https://youtu.be/uXZbHe4sMUk?si=Ke_5NohfG7CaDX0q
When a failure occurs in a jet engine, such as from a blade failure or a bird being ingested, the engine structurally experiences severe loads. These loads may cause secondary structural failures. At the same time, fuel lines may rupture and fuel may be ignited.
Multiple levels of safety are now incorporated into the engine's design and how it is attached to the airliner to minimize the potential for catastrophic loss of the aircraft. Structural shrouds are included within the engine cowling to prevent blade separation from causing further damage to the aircraft. Engines are tested in extremes of rain exposure and bird impact as well as blade separation to verify continued structural integrity. On commercial airliners, the engines are mounted on a pylon that includes structural "fuses" that break, permitting the engine and pylon to "depart" from the wing should the inertia forces of a failure become extreme. This is to prevent the wing primary structure from being compromised. (This concept originated in the B-47 bomber developed by Boeing in 1947 under management of WPAFB.)
(Military aircraft that have embedded engines are generally equipped with ejection seats. Military aircraft with pylon-mounted engines general don't have ejection seats except for the old B-52.)
Jet engines today are remarkably safe both from a statistical basis as well as from what happens with in-flight failures—even extreme failures such as shown in the video. This safety is "engineered" into the overall engine/aircraft design from the outset. This safety is not worked "back in" later.
Based on the improvements that have been made, the FAA now certifies new airliner designs that only use two jet engines but are permitted to fly long distances over water away from emergency landing sites. The reason is that the statistical probability of two engines failing for other than an "act of god"—such as happened in New York with an airliner flying into a flock of birds—is considered so "remote" as to not be considered a design-to requirement.
Achieving this level of mechanical failure reliability was the result of the efforts at WPAFB to develop engine structural integrity criteria and enabling technological advancements for military jet engines. From the success of this effort, the "core" of these military jet engines then became the core of commercial derivatives commonly used on commercial airliners.
The requisite structural airworthiness of these military jet engines is achieved through the formal Engine Structural Integrity Program (ENSIP) contractually required by the U.S. military. The corresponding airframe effort is the Aircraft Structural Integrity Program (ASIP). Both were initially developed by Dr. Lincoln in the 1970s and 1980s.
Rocket engines have not, to my knowledge, been designed per ENSIP or something comparable. (If they are, I would like to see the criteria.) There is no reason why this is not the case other than a conscious choice by someone. ENSIP is totally available to the public.
Absent something like ENSIP being used, the question then becomes what is the statical probability of failure per mission for different failure modes. Some failure modes may be benign from a safety perspective, enabling the engine to just be turned off with jo further safety risk. Others may result in such damage that the safety of the vehicle is potentially impacted. Obviously, the number of engines on the Starship will increase the probability of a failure occurring on each Starship mission. As with the propellant line passing through the LOX tank, the design of these engines may have fundamental safety issues that would require a substantial redesign to correct.
It is also important to keep in mind that Starship is touted as being reusable and intended to be flown many times. Without something comparable to ENSIP/ASIP-type certification, labeling a system as "reusable" has no real merit, in my opinion, other than just for PR purposes. While airworthiness requires reusability, reusability alone does not imply airworthiness. Unfortunately, even the "rocket" experts on YouTube grasp onto "reusable" as if this equates to something akin to airworthiness.
6. Wernher von Braun's "rocket team" back in the 1960s developed the Saturn V—comparable to Starship in size—using public funds. Oday, NASA and the Space Force think that they are getting a new "reusable" Saturn V for free. For the reasons explained above, this is a faulty assumption. When trying to discuss this with folks in the "rocket community", I consistently get a blank look in response.
Does America need a large, heavy, unmanned Spacelifter? Yes. We have it and it is called the Space Launch System—a version of concepts that first emerged in the 1990s as a derivative of the Space Shuttle. I developed one in 1995 with engineers at Lockheed Martin/Huntsville. How many times a year would it need to fly? Perhaps 4-8. It would be used to launch large payloads into LEO that are too complex to assemble in orbit. Payloads such as space hangars, large crew quarters, complex command and control centers, and large components for large spaceships.
What about transporting people to orbit? As I have described previously, WPAFB was prepared to acquire a suitable human spaceflight system (Transatmospheric Vehicle) in 1985. It would have become operational around 2000. Soon thereafter a commercial passenger spaceflight system would have entered service. Like the TAV, it would have been airworthiness certified. (All military aircraft are formally airworthiness certified just as are commercial airliners.) The first system would likely have transported 10 passengers. A second generation system—also a HTHL system flying from runways—would likely have transported 20-30 people to LEO space hotels constructed using large modules launched by the SLS—much as I first envisioned 25 years ago.
The notion of some that Musk and Bezos offer the only path for America to become a true human spacefaring nation is simply false. While Howard Hughes was finally completing the design of his "Spruce Goose", WPAFB was beginning the development of the B-47 which would establish the design model for all future jet-powered commercial airliners. Where would we be today if America had simply waited for Hughes to "get it right"?
The Apollo program was successful using public funds and sound engineering concepts (for that time). Anything less today is a waste of time and resources.
Bryan Zetlen
To view this discussion on the web visit https://groups.google.com/d/msgid/power-satellite-economics/00ef01dae5cc%2472ab50d0%245801f270%24%40aol.com.
james...@aol.com
Is Starship on schedule and on cost?
Is Vulcan on schedule and on cost?
Has any other air force produced a superior air warfare capability?
Was the last home you had built built on schedule and on cost? 😊
Mike Snead
Bryan Zetlen
Keith Henson
>
> Hi, Keith,
>
> My response is lengthy, so I apologize for that.
>
> 1. My concern with the issue of a hypersonic impact goes back to the NASP program when I was looking at how to conduct the flight test program with speeds up to Mach 12. The NASP vehicle would not have a destruct system. (Such systems are simply someone's workaround for a poorly designed system in order to convince the person "signing off" on the flight test that that person would not likely be held responsible for letting the system launch.)
>
> I was told by NASA/KSC that on impact at Mach 6+, it is likely that the kinetic energy of the impact will near instantly vaporize and mix the fuel and oxidizer. Since these are present in the propellant tanks at around optimum ratios, the mixture constitutes an explosive mixture. (The oxygen in the air is a minor contributor, I suspect.) Obviously, the thermal energy from the impact will ignite this explosive mixture.
ton of TNT is 4 GW seconds, LNG/LOX is twice that or about 8 GWs/ton,
or 8 MJ/kg. I.e., the fuel blast for a Mach 6 StarShip impact would
be 4 times the Ke. I don't think the fuel adds much to the crash
problems if you are standing there.
> For the second stage of the Starship, I suspect that the 1200 tons of propellant would detonate something comparable to what happened in Beirut several years ago.
propellant would be about 2.4 kT. That assumes complete mixing, which
is unlikely. Still, you don't want to be standing there.
> https://youtu.be/93tV6-0Ugwk?si=D4jL5iIUAr7qB8fC
>
> Is this a global range safety issue? I think so. If the FAA signs off on Starship launches, they then bear the responsibility for non-involved harm or damage.
are put at risk.
> 2. Is the presumption that a destruct device would prevent this from happening valid? I think this is an unprovable presumption. Destruct systems are subject to failures, faults, intentional sabotage, or hacking just as any other system. Imagine a hypersonic impact and explosion of the magnitude of Beirut happening after the destruct system failed. How would the cause be determined? Who would bear the legal consequences? Elon Musk? The FAA head? The same sabotage that prevents the second stage from operating could also prevent the destruct system from operating, couldn't it?
> Remember that the Starship is supposed to carry people. Are these versions also to use destruct systems? If not, what is the justification for protecting lives onboard from accidental harm due to a destruct system failure while not protecting lives on the ground from harm?
> 3. I think the further assumptions explained on how TEA would be installed and used essentially show this to be an unworkable solution. In the military, great caution is taken with the use of anything that triggers an explosion, such as fuses for bombs. For munitions, substantial testing is performed before a new munition is certified on each aircraft to carry it.
fire before mixing. It's not going to be tested at full scale.
> I cannot imagine how such a certification program, sufficient to eliminate a Starship explosion as a hazard, could be carried out using TEA. I don't see simulated testing achieving this.
thing you can say about a fire started when oxygen starts to leak into
LNG is that it is better than a blast.
> 4. I did not know about the fuel line running through the LOX tank.
> Again, this would have been rejected as a design consideration. In my view, this is just poor engineering based on an assumption of being able to manufacture and install a "perfect" component. In my opinion, this is an example of how not to design a spaceflight system. There are many such considerations that enter into the mix of concepts that are proposed and then weeded out during the conceptual design phase.
>
> I've included an illustration of the 1970s Boeing RASV, promoted by the Boeing president at the time as a suitable new reusable launch system. Boeing was trying to make use of the new SSME engine's improved Isp to "close" the conceptual design of the quasi-SSTO RASV manned spaceflight system.
>
> During the WPAFB TAV concept evaluations in 1984, Boeing proposed this as one of three TAV concepts. It had received wide publicity. My job was to lead the WPAFB formal tech eval of the proposed TAV designs. I discussed the RASV design with Dr. Jack Lincoln, the Air Force's lead for structural integrity—a fundamental part of airworthiness. (He was also my technical boss in my home office.)
>
> A key to Boeing being able to "close" the design—meaning achieve orbit—was the use of a honeycomb panel concept for the airframe. At that time, honeycomb was considered to be a very good weight saving structural design. It was used in the XB-70, for example, as well as parts of other aircraft. However, experience showed that it had a major problem. This was that if the outer surface was damaged causing a break in the continuity of the surface, water from rain or humidity would accumulate in the cell. When heated by supersonic flight or when frozen by high altitude flight, the cell would rupture, spreading the damage internally and potentially causing inflight delamination of the skins. The use of cryogenic propellants in the RASV meant that any flaw in the surface would "suck" in air/water that would liquefy due to the cryogenic propellants (LH2 and LOX). On reentry, the trapped liquid/solid would boil, causing structural damage/skin delamination threatening the integrity of the airframe. The flaw size could be so small as to be essentially invisible to causal walk-around inspection. We believed that it would be very difficult to maintain a RASV in an airworthy condition. In other words, it would be a "hangar queen".
> We also had substantial reservations with the overall RASV "hot structures" approach that was similar to what Starship was proposed to use. Hot structures are vey difficult to design and, especially, to ground test as part of validating the structural integrity of the airframe. This was a major consideration in the NASP program - how to test the airframe? This consideration flows back into key early decisions on what materials to use, what structural concepts to use, what flight profiles to fly, what inspection and repair methods to use, et cetera.
>
> These are just some of the issues we identified with the RASV which was why it was not selected to use as a TAV baseline design.
>
> 5. Jet and rocket engines are very complex. Both use rotating hardware operating at extreme temperatures, pressures, and fluid-dynamic and centrifugal loads. Engine primary structure necessarily operates very close to the maximum permitted structural limits in order to achieve the desired level of performance. For this reason, validating the integrity of the engine is critical.
time. They seem to have the problems under control.
> https://youtu.be/uXZbHe4sMUk?si=Ke_5NohfG7CaDX0q
>
> When a failure occurs in a jet engine, such as from a blade failure or a bird being ingested, the engine structurally experiences severe loads. These loads may cause secondary structural failures. At the same time, fuel lines may rupture and fuel may be ignited.
rockets are without problems, SpaceX has had some blow up.
> Multiple levels of safety are now incorporated into the engine's design and how it is attached to the airliner to minimize the potential for catastrophic loss of the aircraft. Structural shrouds are included within the engine cowling to prevent blade separation from causing further damage to the aircraft.
> Engines are tested in extremes of rain exposure and bird impact as well as blade separation to verify continued structural integrity. On commercial airliners, the engines are mounted on a pylon that includes structural "fuses" that break, permitting the engine and pylon to "depart" from the wing should the inertia forces of a failure become extreme. This is to prevent the wing primary structure from being compromised. (This concept originated in the B-47 bomber developed by Boeing in 1947 under management of WPAFB.)
>
> (Military aircraft that have embedded engines are generally equipped with ejection seats. Military aircraft with pylon-mounted engines general don't have ejection seats except for the old B-52.)
>
> Jet engines today are remarkably safe both from a statistical basis as well as from what happens with in-flight failures—even extreme failures such as shown in the video. This safety is "engineered" into the overall engine/aircraft design from the outset. This safety is not worked "back in" later.
>
> Based on the improvements that have been made, the FAA now certifies new airliner designs that only use two jet engines but are permitted to fly long distances over water away from emergency landing sites. The reason is that the statistical probability of two engines failing for other than an "act of god"—such as happened in New York with an airliner flying into a flock of birds—is considered so "remote" as to not be considered a design-to requirement.
>
> Achieving this level of mechanical failure reliability was the result of the efforts at WPAFB to develop engine structural integrity criteria and enabling technological advancements for military jet engines. From the success of this effort, the "core" of these military jet engines then became the core of commercial derivatives commonly used on commercial airliners.
>
> The requisite structural airworthiness of these military jet engines is achieved through the formal Engine Structural Integrity Program (ENSIP) contractually required by the U.S. military. The corresponding airframe effort is the Aircraft Structural Integrity Program (ASIP). Both were initially developed by Dr. Lincoln in the 1970s and 1980s.
>
> Rocket engines have not, to my knowledge, been designed per ENSIP or something comparable. (If they are, I would like to see the criteria.) There is no reason why this is not the case other than a conscious choice by someone. ENSIP is totally available to the public.
>
> Absent something like ENSIP being used, the question then becomes what is the statical probability of failure per mission for different failure modes. Some failure modes may be benign from a safety perspective, enabling the engine to just be turned off with jo further safety risk. Others may result in such damage that the safety of the vehicle is potentially impacted. Obviously, the number of engines on the Starship will increase the probability of a failure occurring on each Starship mission. As with the propellant line passing through the LOX tank, the design of these engines may have fundamental safety issues that would require a substantial redesign to correct.
> It is also important to keep in mind that Starship is touted as being reusable and intended to be flown many times. Without something comparable to ENSIP/ASIP-type certification, labeling a system as "reusable" has no real merit, in my opinion, other than just for PR purposes.
enormous cost advantage.
> While airworthiness requires reusability, reusability alone does not imply airworthiness. Unfortunately, even the "rocket" experts on YouTube grasp onto "reusable" as if this equates to something akin to airworthiness.
>
> 6. Wernher von Braun's "rocket team" back in the 1960s developed the Saturn V—comparable to Starship in size—using public funds. Oday, NASA and the Space Force think that they are getting a new "reusable" Saturn V for free. For the reasons explained above, this is a faulty assumption. When trying to discuss this with folks in the "rocket community", I consistently get a blank look in response.
>
> Does America need a large, heavy, unmanned Spacelifter? Yes. We have it and it is called the Space Launch System—a version of concepts that first emerged in the 1990s as a derivative of the Space Shuttle.
can't exceed $100/kg. Say they both will lift 100 tons, 100,000 kg.
SLS cost is a billion dollars or $10,000/kg. That's too expensive by
a factor of 100.
> I developed one in 1995 with engineers at Lockheed Martin/Huntsville. How many times a year would it need to fly? Perhaps 4-8. It would be used to launch large payloads into LEO that are too complex to assemble in orbit. Payloads such as space hangars, large crew quarters, complex command and control centers, and large components for large spaceships.
>
> What about transporting people to orbit? As I have described previously, WPAFB was prepared to acquire a suitable human spaceflight system (Transatmospheric Vehicle) in 1985. It would have become operational around 2000. Soon thereafter a commercial passenger spaceflight system would have entered service. Like the TAV, it would have been airworthiness certified. (All military aircraft are formally airworthiness certified just as are commercial airliners.) The first system would likely have transported 10 passengers. A second generation system—also a HTHL system flying from runways—would likely have transported 20-30 people to LEO space hotels constructed using large modules launched by the SLS—much as I first envisioned 25 years ago.
>
> The notion of some that Musk and Bezos offer the only path for America to become a true human spacefaring nation is simply false. While Howard Hughes was finally completing the design of his "Spruce Goose", WPAFB was beginning the development of the B-47 which would establish the design model for all future jet-powered commercial airliners. Where would we be today if America had simply waited for Hughes to "get it right"?
>
> The Apollo program was successful using public funds and sound engineering concepts (for that time). Anything less today is a waste of time and resources.
get major space programs done, I wish you better luck than I have had
over the last 50 years.
james...@aol.com
I worked at WPAFB for 37 years with much of that in the Deputy for Engineering which provides engineers to the System Program Offices (SPO). In the nearly 25 years that I worked in EN up through the mid-1990s, very, very few engineers left government service to work for a prime contractor. I can think of only a couple.
There were two primary reasons for this. The first was that government employees then were vested in the separate government retirement program that made leaving government employment very financially challenging once you had worked for the government for any substantial time. The second was that the experience and expertise of government engineers was different from those in private companies. Most government engineers—not all certainly—had broad experience in monitoring contractor efforts versus private company experience where an engineer would likely specialize in a particular area.
I once talked about this with my branch chief, himself a former engineer who came to work, like many, from private industry in the downsizing following the end of the Vietnam War and Apollo program. My branch chief told me that in structures work, the typical contractor engineer would “specialize” in a particular area, working that one area for much of their career absent promotion to management. For example, he told me that it was typical for a structures engineer to work only on the door frames surrounding passenger doors of a commercial airliner. In contrast in our branch, the engineers worked on many efforts, reviewing the efforts of contractors under contract to various SPOs. For major programs, such as the B-2, an engineer would be collocated full time to the SPO. (My experience ranged from ejection seats to the NASP and DC-X.)
The entire purpose of the B-2 program was to create a survivable strategic bomber that could, with high confidence, conduct offensive missions in highly contested airspace. The B-2 program was likely conceived in the late 1970s at a time when the Soviets had developed extensive and effective air defense capabilities. For the United States to maintain a true nuclear deterrent force based on the triad concept of land and sea-based missiles and strategic bombers, it was necessary to have the ability to make Soviet air defenses ineffective. (This was also a time with ballistic missile defense was emerging meaning that the missile-side of the triad could become vulnerable.)
I believe the original price noted for the B-2 reflected a fleet buy of 100 bombers meaning that the indirect costs of R&D would be spread over the 100 bombers. With a buy of only 20, along with early program termination costs, as well as the inevitable costs of the full R&D for an entirely new, almost entirely advanced composite aircraft of a novel design, while achieving a miniscule operational radar return signature, added to the per unit costs. Despite this, the B-2 has proven effective as a strategic deterrent while also providing the U.S. with a global covert conventional warfare capability—critical where limited but undefendable operations could prevent the need for a much larger and costly war operation.
The versatility of this design is now verified by the emergence of the B-21—what appears to be an updating to the now 40-year-old B-2 design.
Often now when government engineers reach the retirement age, they retire and become support contractors, often for the same program that they supported before retirement. This provides continuity of experience while preventing the government from needing to hire more full-time career engineers to meet immediate support needs. In other words, it keeps total costs down. I had a friend do this. He had a total of 50 years of service. I did not do this.
Mike Snead, PE
Bryan Zetlen
Tim Cash
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james...@aol.com
Bryan,
I do not dispute that there were cost overruns. There are almost always cost overruns in DOD programs because of the nature of the threat, the length of time involved in developing a new capability while the threat and mission are also evolving, and the inherent initial uncertainty in being able to fully “scope-out” what will be needed when bringing substantially new technological capabilities into operational service.
The federal government long ago decided to rely on contractors to design and build its weapon systems instead of generally relying on in-house weapons bureaus. With this decision came acceptance of “profitability” being a relentless political issue raised to oppose new military programs. It raises the question of what is a politically acceptable profit margin when the need for investment in a defense company must compete with investments in, say, Tesla? Or Apple? Or Microsoft?
You will need to further explain your comments on bomber survivability as they make no sense to me.
You will also need to explain your comments on collusion. One aspect of government defense contracting is to keep the industrial base “healthy” over decades. Look at Starship for example. How long has Starship been under development and it is still not “operational”. World-leading defense companies just don’t spring into action quickly. Starting one is not like selling an idea on Shark Tank. Take a look at Bezos and his 20 years trying to turn Blue Origin into a functioning aerospace company.
There is great animosity in the American public against the military and what many call the “military-industrial complex”. Often, people cite the “warning” by President Eisenhower about the threat of the growing military-industrial complex. Yet, as the Allied Supreme Commander, he made use of the product of this military-industrial complex to lead the U.S. and its allies to victory in Europe. As president for eight years, he made extensive use of this military-industrial complex, in total secrecy, to develop America’s substantial nuclear deterrent forces and substantial air and space reconnaissance and surveillance capabilities. Together, those two “needs” dominated his administration’s national security efforts. Yet, folks believe he opposed the military-industrial complex.
Mike Snead, PE
a.p.kothari astrox.com
Good points, Mike.
Media and Hollywood have salivated over making MIC into boogeyman every chance they get, as easy villains. Sure they have been responsible for many cost overruns but then look at the cost increases in Healthcare in this country. NASA’s budget in the heyday of Apollo was smaller by a factor of 6. Now that factor is 165+. THESE ARE the huge numbers. But media does not take that on.
I wrote this in 2012 so some numbers have changed but you get the point:
- A Rocket Scientist’s Lament: https://www.baltimoresun.com/2012/09/17/a-rocket-scientists-lament-3/ (Baltimore Sun: September 2012)
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Astrox Corporation
AIAA Associate Fellow
Member, AIAA Aerospace Power TC
Ph: 301-935-5868
Web: www.astrox.com
Email: a.p.k...@astrox.com
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From: jamesmsnead via Power Satellite Economics
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james...@aol.com
The real “issue” that we are skirting around is how to avoid such cost overruns in spacefaring efforts.
I think we should always expect some measure of cost overrun simply because of unpredictability in material and labor costs, often because of factors well beyond the control of the contractor or SPO—such as seen in the last several years.
Having said this, what we can control is the uncertainty in the design that leads to design-driven cost escalation. I cite four examples:
1. The first point in cost avoidance is to exclude technical political maneuvering from the consideration of the design of the system.
Example: The National Aerospace Plane effort got its start with a proposal by Tony DuPont to build an X-15-style X-aircraft to demonstrate his version of an injector-rocket hybrid “jet” engine. After many rejections within the Federal Government, he caught the interest of DARPA. DARPA assembled a small team, “loosely managed” led by the TAV Project Office at WPAFB where I had recently joined as the TAV Project Engineer. (The project office was a small group of about 6 people.) The DARPA effort was called “Copper Canyon” and was separate from the TAV efforts. I “went along” on the Copper Canyon meetings to keep abreast of the discussions—primarily focused on the feasibility of scramjet propulsion. This was in 1984-85. They were looking as a 100K GTOW vehicle to test the engine concept. By mid-1985, the effort had caught the attention of the White House and grew into a primary part of a new presidential effort at advancing America’s aerospace capabilities. This made it a “national” program. Soon it came to be jointly “owned” by the Air Force, NASA, Navy, SDIO, and DARPA. As part of the national effort, achieving SSTO became a program objective. In part, this program “killed” the WPAFB TSTO TAV effort.
The F-35 appears to be another good example of a national program failure—a good idea 25 years ago grew into a must-have tri-service “silver bullet”. We tried this before with the F-111.
Lesson-learned: Don’t do “joint” programs. Pick an organizational leader and hold them accountable for their failures.
2. The second point is to not put scientists in charge of how money is to be spent.
Example : Once started, NASP became a high-technology “money bank” for the hypersonic R&D community in the government labs. Many NASP-funded efforts were simply unfunded efforts from previous years.
I was the first engineer assigned to the NASP Joint Program Office. We had a very small engineering cadre of about 10 or so people in the JPO. A couple of years into the program, we were working on the next year’s R&D budget. (There was a separate group in the JPO handling the R&D efforts as this was where most of the money was being spent.)
At that time, we had five prime airframe contractors and three prime engine contractors. This was a presidential/national program and no major aerospace company wanted to be left out and Congress wanted the “fame dollars” spent in their states and districts.
These airframe and engine contractors were working on their particular version of conceptual design of the NASP—meaning we had multiple different concepts in the works. Meanwhile, the R&D community was working on their particular areas of funded research. When the time came to provide engineering inputs into the next year’s R&D budget, this task fell to me as the Chief Engineer was away on TDY as I recall. I decided to ask each of the prime contractors for their inputs as to what proposed work would benefit their conceptual design efforts. They “bravely” responded and indicated that only about 15-20 percent of the proposed funds would be spent on areas that would be of help in maturing their design. I forwarded these results and later got “taken behind the woodshed” for doing so as this cast doubt on the wisdom of the R&D community “knowing” that their efforts had value to the program. By that time, the program was primarily a collection of disparate R&D efforts under the guise of an X-aircraft program. Over a billion $$ were being spent on R&D each year.
Lesson-learned: The role of the R&D community is to assist, not to lead in determining the “Third best” solution to achieve the overall operational capability. Here I refer to Sir Robert Watson-Watt’s “Law of the Third Best”. “Give them the third best to go on with; the second best comes too late, the best never comes." The R&D community vied to propose “first best” solutions while the contractors sought “third best” solutions. Third best is TRL 6+.
Example 3: SpaceX’s Starship. For this discussion, my primary criticism is that the design is far from settled. Essentially, we are watching a conceptual design process being undertaken through building hardware. I don’t fault this being done. I fault the PR that portrays this as a “settled” design on which key national spacefaring planning has been prematurely founded.
Lesson-learned: Don’t “buy-in” based on the hype. The presidential hype of NASP largely contributed to not beginning the WPAFB TAV effort that was based on TRL 6+ technology. (The three-star Aeronautical Systems Division commander recommended starting a TAV program. He was then also managing the F-22, B-2, C-17, B-1B, and F-117 programs—meaning he/ASD understood what it took to develop such new capabilities.) The manned Air Force TAV would have been operational around 2000 with a commercial variant soon after.
Example 4: Hoover Dam. Initially for flood control and irrigation water use, the Hoover Dam was proposed in the 1920s. Government engineers identified the site and developed a detailed description of what was to be built. (See attached.) The specification was reasonably detailed with 100 pages and 76 drawings. This means that considerable in-house effort went into the design of an “integrated” solution. This design/specs were then put out for bid. Due to the scale of the effort, a joint company was formed to submit a bid—Six Companies. One of these companies employed Frank Crowe, one of the leading dam builder. He was put in charge. The effort came in under budget and was completed quicker than the schedule.
Other examples where competent engineering leadership made a difference are the first Transcontinental Railroad, Panama Canal, and the Saturn V.
Lesson-Learned: What are primarily engineering efforts should be led by competent engineers.
=====
The United States has an immense “store” of untapped aerospace “mastery” that is currently not being used or used wisely. This is leading to “wrong-headed” approaches that are failing, in my opinion, in making America a true human spacefaring nation. As a nation, we have forgotten that competent engineering leadership is needed to be successful in achieving substantial operational goals.
Mike Snead, PE
