TSR Engine Wars comments

Jeff Foust has allowed me to post comments on his blog “The Space Review” and I have linked Ice on the Moon with those comments. I am in fact surprised none of the people replying to my comments have been here yet. They will come. Here are some of my comments from the review:

“It was actually addressed in the shuttle program with the pressure-fed ocean recovered booster. Perhaps the single most egregious wrong turn in the space program was going with the SRB as a cost-cutting measure. The pressure-fed ocean recovered booster is still the missing piece of technology required to enable efficient Super Heavy Lift Vehicle operations. As I have commented many times, Musk and Bezos both failed the genius test by not going straight to the 1972 TRW booster study as a model.”

And, after some wailing and gnashing of teeth replies:

“I guess I should address the validity of the supposed “shortcomings” of pressure-feds:

1. Yes, pressure-feds are built to contain high pressure which means they are quite tough and will last…for repeated launches. The Ares 1X SRB casings were some of the original ones from the 80’s so these kind of boosters can be reused, unlike others, without worrying about their fragility.
2. Comparatively little extra mass is added in regards to pressure supply and this pressure provides even more structural integrity to add to the already robust heavy duty structure.
3. Parachutes add comparatively little mass and are…reusable.
4. Recovering the boosters for reuse by ship is part of the no-land-back reuse scenario. Land-backs require far more powered maneuvering, throttling, landing arrangements, fuel, etc.

The land-back concept, whether to land or barge, subjects the far more fragile non-pressure-fed to a harder landing and requires fuel and landing gear mass. Considering the inspections required to turbopumps and structure the pressure-fed may very well come out ahead in efficiency (and of course, price). The critical advantage is the multi-million pound thrust of ocean recovered boosters compared to much smaller land-back concepts.”

And after a comment about space plane type return of engines after launch:

“I have to disagree. In terms of simple the pressure-fed being parachuted into the ocean simply cannot be beat. I would add that a core stage going to the Moon could actually separate the engine group from the stage after escaping Earth gravity, do a free return around the Moon back to Earth, and with heat shield, parachute, and salt water protection system, also be recovered at sea for reuse. This would allow the empty core stage structure to continue on to Low Lunar Orbit (LLO) and be utilized as a wet workshop.”

And after a fairly ridiculous comment criticizing the wet workshop concept:

“How do you make this stuff up? The Wet workshop is not built in space, it is built on the ground and components stored as payload separated from the tanks. The equipment is moved into the tanks and bolted down in space when the tanks are no longer “wet”. Hence, the “workshop”. It has always been a no-brainer this is the way to go. Except of course, it you are promoting a rocket not big enough for practical wet workshop applications.

The wet workshop cannot be beat because it turns the empty fuel stage into crew quarters and is thus the ultimate reuse scheme. It has been the case for years that anything not found on the flagship company website by NewSpace advocates is denigrated and dismissed. Sad.”

“I would suggest the next iteration of the SLS be built for placing a wet workshop core in Low Lunar Orbit (LLO) using the payload- a lunar lander- engine for the burn. This iteration would also make use of advanced boosters built as pressure-fed ocean recovered components supplying hydrogen and oxygen propellants to the core stage engine group during the initial launch phase. Studies were done of Saturn V designs with this feature and the falcon heavy was also proposed with a propellant cross-feed system.

The core stage would achieve escape velocity and head for the Moon at which point the engine group would separate and follow a free return around the Moon back to Earth, re-enter with heat shield, salt water protection system, and parachute into the ocean for reuse. The empty stage with lunar lander attached as payload would use the lander engine to insert into Low Lunar Orbit. The lander would then descend to the ice deposits and from the ice take on a load of water and manufacture new propellants.

The semi-expendable robot lander would then make repeated trips between the surface and the workshop to transfer water-as-radiation shielding. When the radiation shield was full then two such workshops would be connected with a tether system and spun up to 1 gravity. With massive kiloton range water shields providing a near-sea-level radiation environment and artificial gravity astronauts arriving from Earth would suffer no dosing or debilitation. With large enough living quarters these astronauts could manage tours of several years without any physiological damage.”

And after a typical NewSpace-state-hate-libertarian reply:

“Government efforts are why we are in space- not “private” efforts. You are practicing blatant cognitive dissonance. There is not going to be any “free” space station. There is no cheap. The only significant revenues coming from space are GEO telecom satellites, the rest is fantasy. Only state sponsored programs using Super Heavy Lift Vehicles will expand the human presence into the solar system. “Private space” is a stumbling block as long as the fans keep pushing their tourist and Mars fantasies.

The reality is Skylab was large enough to test the wet workshop concept but was only funded as a dry workshop. For want of a few million dollars a space station with a larger interior space than the ISS could have been sent up in one evening for about the cost of one shuttle launch. The “reusable” shuttle, which threw away a most useful structure and instead brought up small pieces one at a time over a decade resulted in a 180 billion dollar Albatross that is now in the process of dying of old age. While the workshop has equipment installed from a payload area the inflatable of course has a problem with bolting anything down.

The entire inflatable concept is inherently flawed in terms of a space station or spaceship crew compartment if artificial gravity or powered maneuvering is required. It originated with not having a large enough stage to use as a wet or dry workshop. Private space does not have what it takes.

An inflatable might work in a lava tube on the Moon.”

And last of today:

“From wiki:
“-the M-1 project was uprated from 1.2 million pounds force to a nominal 1.5 million pounds force, and the designers deliberately added more turbopump capability to allow it to expand to at least 1.8 million pounds force and potentially as high as 2.0 million pounds force.[1]”

The SLS is presently being built with four RS-25 engines when a single M-1 would do the trick. No really big engines that compare with past efforts are being contemplated. Concerning these new engines a contest between satellite launch concerns is a better description than “engine wars.”

Human Space Flight Beyond Earth Orbit (HSF-BEO ) is going to require Super Heavy Lift Vehicles with those really big engines. My favorite was always the “notional” 325 inch solid with 15 million pounds of thrust. A pair of those (actually they were proposed mounted quad) would triple the thrust of the SLS. But the environmental concerns with SRB’s are not going away and a pressure-fed is the better direction to go in for advanced SLS boosters. The problem is the solid fuel lobby is not going to like a new pressure-fed booster in development taking money out of their pockets.”

Published by billgamesh

Revivable Cryopreservation Advocate

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