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Old January 21st, 2014, 05:40 AM
Delta Force Delta Force is offline
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Alternate American Space Program (mid-1960s Onwards)

I was going to write a PoD here, but I think it would be best to start with a discussion of the rocket and spacecraft families themselves. The setting is the mid-1960s to early 1970s. The Space Shuttle system as we know it has been rejected in favor of separate manned and cargo flights. There's no need to launch a huge system for routine spaceflight, and payload recovery and relaunch is an expensive option. A crewed flight will be sent to do in flight repairs and/or recover any important components from unmanned flights. This really isn't that different, it's what the Shuttle ended up doing for most of its career anyways (I think it recovered all of two satellites).

The American space industry faces foreign competition to put payloads into space from a consortium of Commonwealth and European companies (more information here). Government payloads are likely to be flown on American rockets, but with foreign competition all commercial payloads are going to be flown on the rocket with the best value and/or capabilities. The government has the following needs going into the future:

1. Routine manned access to space. The military and civilian sides both want the ability to dock with space stations and interact with satellites. The military wants the ability to carry out major delta-V changes after launch (to become less predictable and/or access many satellites). The military also wants the ability to launch with and/or recover up to a metric ton of payload for return to Earth (cameras, sensors, objects taken from orbit) and carry out a soft landing.

2. The civilian program wants the ability to launch a variety of scientific probes and payloads. The objects might be a bit larger than in our timeline though, conducting a Planetary Grand Tour in the late 1970s and sending sophisticated rovers similar to the Lunokhods to the Moon and Mars. The military wants the ability to deploy typical military payloads such as communications, positioning, and reconnaissance satellites.

3. The civilian program is interested in flights to Venus (obviously just a flyby) and Mars, but only if flight times can be brought down to a safer limit. They are interested in large space stations, but they don't have to be monolithic. Basically, they are willing to consider Earth Orbit Rendezvous (and other forms of multiple launch) if it offers a higher degree of safety and/or lowered costs. The military program is interested in smaller space stations on par with the Manned Orbiting Laboratory or Salyut.

Obviously, there are also potential commercial sales. What launch vehicles and/or spacecraft families will best meet the needs of government and industry going forward?

Some launch families that were prominent in this era (other variants and families are possible):
-- Atlas
-- Delta
-- Saturn
-- Titan

Some vehicle families that were prominent in this era (other variants and families are possible):
-- Advanced Gemini
-- Apollo
-- Big Gemini
-- Dyna-Soar
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Old January 21st, 2014, 07:00 PM
Delta Force Delta Force is offline
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Bumpity bump.
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Old January 21st, 2014, 07:49 PM
brovane brovane is offline
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As far as manned launch vehicles.

You are probably best off using a deriative of the Saturn.

For LEO tasks a standard saturn with the 1st stage replace with Solids and then a S-IVB 2nd stage and you can get a reasonable payload into orbit. Use the Apollo Command module as your basis. Probably have some type of multi-mission module that sits on top of the S-IVB that you dock with after launch. This can be customized depending on what you need to do. For example going to a space station it could just have supplies etc. Going to work on a satellite it would have a AirLock and other things. If you put 2x156" Diameter Solid Boosters as your first stage with a S-IVB 2nd stage you can put over 70,000Lb to LEO for a fairly cheap cost.

For BEO human launches. You will run into the fact that the VAB doors can only support rockets up to 410 feet tall. The best bang for the buck that I have seen is the MLV-Sat-V-25 (S) proposed variant. It is a standard Saturn V with a stretched S-1C and S-IV stages and 4 156" Solids. With this you can get around 180,000lb to TLI. You can further improve the performance if you swap out the F1's for F1A and swap the J-2 engines for J-2S or HG-3 engine and this can put you up near 200,000Lb to TLI.

However if you are really looking at interplanetary missions with shorter mission times you probably need to look at the NERVA nuclear rocket program.

Just some ideas.
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Old January 21st, 2014, 08:55 PM
Talwar Talwar is online now
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I've been doing some worldbuilding for a story/series and am going to look at Gemini/Big Gemini/MOL-analogues for hardware...
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Old January 21st, 2014, 09:30 PM
Delta Force Delta Force is offline
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Thought on safety and survivability. How did the ejection seats on Gemini compare to the escape towers on Mercury and Apollo? Seems it wouldn't offer a performance envelope or safety margin as strong as the the escape towers. It does make me wonder if thought was ever given to crew encapsulation (B-58/F-111 style) as a hybrid method usable across almost the entire flight envelope (with a heat shield, it might even be able to do reentry).
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Old January 21st, 2014, 10:02 PM
brovane brovane is offline
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Originally Posted by Delta Force View Post
Thought on safety and survivability. How did the ejection seats on Gemini compare to the escape towers on Mercury and Apollo? Seems it wouldn't offer a performance envelope or safety margin as strong as the the escape towers. It does make me wonder if thought was ever given to crew encapsulation (B-58/F-111 style) as a hybrid method usable across almost the entire flight envelope (with a heat shield, it might even be able to do reentry).
Realistically on the Gemini Capsule the astronauts really didn't want to use the ejection seats. The sync was that the heavy doors where supposeed to clear themselves first but nobody was really sure. The astronauts didn't trust that the sync would happen correctly. Also it didn't have as great as escape envelop as the Capsule with the Escape Tower. On Gemini 6 during the pad abort even though the book said to hit the eject neither astronaut wanted to even though they where sitting on top of a potential bomb.
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Old January 21st, 2014, 10:13 PM
Delta Force Delta Force is offline
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Realistically on the Gemini Capsule the astronauts really didn't want to use the ejection seats. The sync was that the heavy doors where supposeed to clear themselves first but nobody was really sure. The astronauts didn't trust that the sync would happen correctly. Also it didn't have as great as escape envelop as the Capsule with the Escape Tower. On Gemini 6 during the pad abort even though the book said to hit the eject neither astronaut wanted to even though they where sitting on top of a potential bomb.
That probably had more to do with being close to the ground, as opposed to concerns with the doors/synchronization. Zero-zero ejection seats are a relatively recent development, and before that point seats had minimum altitude and speed requirements for safe operation.
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Old January 21st, 2014, 10:25 PM
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That probably had more to do with being close to the ground, as opposed to concerns with the doors/synchronization. Zero-zero ejection seats are a relatively recent development, and before that point seats had minimum altitude and speed requirements for safe operation.
That's a good point about the history of the seats, but it misses a point: the decision to go with ejection seats (as opposed to the entire-capsule abort tower on both Mercury and Apollo) was made based mostly on the early hopes about horizontal landing under parafoils, and the need to get the crew up and out of a capsule coming in horizontally to land. However, in doing so, they eliminated a lot of the ability to get crew safely out of a near-pad abort, or an abort happening above...well, I don't know the exact limits of the seats, but I can't imagine pulling the abort lever at Mach 1 or above would have been fun. Because the Titan pulled about 1.3 Gs off the pad and only got faster from there, that means the seats only covered about a 30 second window of the flight. That was a spectacularly risky design decision to make in the pursuit of a landing method they weren't sure was going to work (and indeed didn't end up being used).
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Old January 21st, 2014, 10:43 PM
Delta Force Delta Force is offline
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Originally Posted by e of pi View Post
That's a good point about the history of the seats, but it misses a point: the decision to go with ejection seats (as opposed to the entire-capsule abort tower on both Mercury and Apollo) was made based mostly on the early hopes about horizontal landing under parafoils, and the need to get the crew up and out of a capsule coming in horizontally to land. However, in doing so, they eliminated a lot of the ability to get crew safely out of a near-pad abort, or an abort happening above...well, I don't know the exact limits of the seats, but I can't imagine pulling the abort lever at Mach 1 or above would have been fun. Because the Titan pulled about 1.3 Gs off the pad and only got faster from there, that means the seats only covered about a 30 second window of the flight. That was a spectacularly risky design decision to make in the pursuit of a landing method they weren't sure was going to work (and indeed didn't end up being used).
If speed wasn't an issue, how high up could someone use an ejection seat before they would have to worry about burning up on reentry? Eventually they stopped using encapsulation on high speed aircraft because the crew could usually wait for the aircraft to transition back to subsonic flight, but aircraft don't fly high enough for reentry to be a concern.

I've heard that it would be possible to develop a space suit capable of reentry for a fairly low cost, which (when combined with zero-zero ejection) would provide an abort mode for almost all aspects of flight. Reentry itself might still be an issue, but it's a very narrow flight envelope and most potential disasters are going to occur while the capsule/shuttlecraft is riding the rocket into space.
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Old January 21st, 2014, 11:06 PM
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If speed wasn't an issue, how high up could someone use an ejection seat before they would have to worry about burning up on reentry? Eventually they stopped using encapsulation on high speed aircraft because the crew could usually wait for the aircraft to transition back to subsonic flight, but aircraft don't fly high enough for reentry to be a concern.
You'd have to worry about aerodynamic issues on the way down well before the thermal load becomes a problem. Basically, if you're bailing out at more than Mach 2 (which occurs about a minute after liftoff for the Titan), then your apogee height is enough that you're looking at a task similar to that faced by Felix Baumgartner on the way back down. It's potentially solvable, but there's two major challenges: 1) the crew have to be individually capable of reliably bailing out and performing a high-altitude parachute jump and 2) it still only works if you have an individual ejection seat for each crew member--which brings a major weight and design penalty if you're talking about a 6-person station taxi or something. It's much simpler to have an abort system to get the crew and capsule off--the capsule of course is already a passively-stable pressure vessel across the entire applicable range of Mach numbers/re-entry and has its own landing arrangements (parachutes, airbags, whatever).
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Old January 21st, 2014, 11:14 PM
Delta Force Delta Force is offline
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You'd have to worry about aerodynamic issues on the way down well before the thermal load becomes a problem. Basically, if you're bailing out at more than Mach 2 (which occurs about a minute after liftoff for the Titan), then your apogee height is enough that you're looking at a task similar to that faced by Felix Baumgartner on the way back down. It's potentially solvable, but there's two major challenges: 1) the crew have to be individually capable of reliably bailing out and performing a high-altitude parachute jump and 2) it still only works if you have an individual ejection seat for each crew member--which brings a major weight and design penalty if you're talking about a 6-person station taxi or something. It's much simpler to have an abort system to get the crew and capsule off--the capsule of course is already a passively-stable pressure vessel across the entire applicable range of Mach numbers/re-entry and has its own landing arrangements (parachutes, airbags, whatever).
Do you know if they ever designed or proposed an escape tower for the Gemini capsules? It's certainly going to be an issue once you get past two crew members.
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Old January 22nd, 2014, 12:21 AM
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Do you know if they ever designed or proposed an escape tower for the Gemini capsules? It's certainly going to be an issue once you get past two crew members.
From what I recall and see on the web checking those recollections, most of the the Lunar Gemini proposals went for a tower, as did Big Gemini. I'm not sure about Blue Gemini. However, those were all pretty "paper" projects, so file them more under proposals than designs. Still, it's indicative of what they were thinking.

I think the original Gemini just had the problem that they got the contract in '61 and were expected to have a spacecraft flying in '65, which is a really short schedule. They bet on the parasail landing, and needed ejection seats in case they ran into issues with that deploying wrong or the landing going badly. Then, by the time that it became apparent that wasn't going to work, they were locked into the ejection seats.
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Old January 22nd, 2014, 01:00 AM
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Were the Gemini derivatives going to use upgraded Titan rockets or Saturn IBs (or something else)? Also, do you know why the USAF went with the Titan over the Atlas for its official launch vehicle? I imagine the fact that a derivative remained in service with USAF SAC units probably played a role, but was that it?
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Old January 22nd, 2014, 01:27 AM
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Were the Gemini derivatives going to use upgraded Titan rockets or Saturn IBs (or something else)?
They basically looked at everything. Titan III, Saturn IB, and most of the alternate Saturn derivatives. Especially for Big G, they needed the throw.
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Also, do you know why the USAF went with the Titan over the Atlas for its official launch vehicle? I imagine the fact that a derivative remained in service with USAF SAC units probably played a role, but was that it?
It was more that Atlas was "balloon" tanks. In these, the tank internal pressure is a lot of the structural support of the vehicle--even when standing on the pad, the tank was supported largely by the fuel inside, much less when under thrust. This allows thin, lighter tank skins, but they don't take well to having boosters attached--the booster attachments create point loads, and thus stress concentrations. Moreover, the Atlas only had a gross mass of only about 120 tons, compared to about 340 tons for the Titan core, so it'd take ridiculous amounts of booster oomph to get to the payload the Air Force needed.
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Old January 22nd, 2014, 08:25 PM
Delta Force Delta Force is offline
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It was more that Atlas was "balloon" tanks. In these, the tank internal pressure is a lot of the structural support of the vehicle--even when standing on the pad, the tank was supported largely by the fuel inside, much less when under thrust. This allows thin, lighter tank skins, but they don't take well to having boosters attached--the booster attachments create point loads, and thus stress concentrations. Moreover, the Atlas only had a gross mass of only about 120 tons, compared to about 340 tons for the Titan core, so it'd take ridiculous amounts of booster oomph to get to the payload the Air Force needed.
Forgot about how the newer Atlas rockets are basically different vehicles. Reading about how the Atlas worked makes me wonder how it avoided turning into (and acting like) a deflating balloon as it continued on its flight. How did it avoid losing pressure as the flight went on?
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Old January 22nd, 2014, 08:55 PM
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Forgot about how the newer Atlas rockets are basically different vehicles. Reading about how the Atlas worked makes me wonder how it avoided turning into (and acting like) a deflating balloon as it continued on its flight. How did it avoid losing pressure as the flight went on?
With most rockets, the ullage (gap left behind as propellants are drawn out of their tanks) is filled with pressurized gasses to keep the tank at constant pressure--after all, even if the tank pressure isn't being relied on for structure, the turbopumps are only sized for a certain pressure increase from the tanks to the injectors. There's a few different ways to do it--high-pressure helium tanks or another gas, or tapping off some pressurized propellant gasses, like SSME did, and I'm sure there are others. I'm not sure which scheme Atlas used, but the short answer is that tank pressure was kept constant somehow.
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Old January 24th, 2014, 11:34 PM
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Is there a simple way to calculate payload capacity to certain locations? I don't want to end up with Titans and other light/medium rockets launching impossibly heavy payloads to Mars and beyond, or alternatively, using Saturns to launch payloads where an Atlas, Delta, or Titan would have sufficed.
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Old January 24th, 2014, 11:52 PM
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http://www.silverbirdastronautics.com/LVperform.html

Quite a few launch vehicles already included. Anything else you'll have to enter yourself as 'user-defined'. You just need your orbital parameters for earth orbits or the hyperbolic excess velocity of the interplanetary transfer.
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Old January 24th, 2014, 11:56 PM
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Is there a simple way to calculate payload capacity to certain locations? I don't want to end up with Titans and other light/medium rockets launching impossibly heavy payloads to Mars and beyond, or alternatively, using Saturns to launch payloads where an Atlas, Delta, or Titan would have sufficed.
What I'd recommend is Shilling's calculator, the one linked above. For anything beyond Earth, click the "escape trajectory" option at the bottom right, then fill in a C3 value. Basically, going to the moon needs C3=0, and Mars or Venus is C3=15. Jupiter is about 80, and for Mercury and beyond Jupiter, you're looking for >100 or so. Some Googling can usually turn up a C-3 figure close enough to play with.

Luckily, most viable missions will probably slot into a Titan III of some variant, which you can find under the "historical" tab on Schillings--select the appropriate options, and pick a launch site (recommend the Cape). For other historic or proposed LVs, you can use "user-defined." Get the gross mass and dry mass off of astronautix, and from that you get the dry mass and fuel in each stage. Fill that into Schilling's along with the vacuum thrust and specific impulse figures, and punch it.

It'll give a payload capability for that vehicle to that orbit. I recommend making a table in excel or something for any LVs you have to enter so you have the information handy without re-calculating in the future. Record it for C3=0, C3=15, ect.
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Old January 25th, 2014, 12:05 AM
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Can that calculate the kind of rocket you would need to return something to Earth (or at least Earth orbit) as well? I'm thinking something like Viking/Luna or Lunokhod doing sample return from Mars (possibly other bodies).
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