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The reactivation of STS need not be a death knell for space exploration. We can retain STS to do what little good it does, have commercial crew and cargo transfer vehicles to service ISS, use ISS as an orbital manufacturing facility to reclaim the materials in the STS and SLS ET's, and use SLS to lift cargo required for a real manned space exploration program. Consolidation of facilities and elimination of non-essential programs is the key.
The cost of STS was driven by permitting contractors to operate support facilities all over the country. If NASA had mandated that all flight hardware be built, tested, and launched from one location, then the number of employees required to maintain facilities, contractor travel costs, and hardware transportation costs plummet. Head count for redundant operational support also plummets.
Man-rated flight hardware that's available right now and not years into the future, if and when it's development is completed- something that is entirely dependent upon political support, is what we should use. NASA doesn't have a manned space program right now because the obvious issues with STS, Ares/SLS, and Altair/Orion were ignored.
Although some useful upgrades were incorporated into STS, a lot of equally important cost reduction measures, head count reduction measures by any other name, were never implemented. The orbiter TPS immediately comes to mind. If JPL can design robots that drive around on Mars, then it can sure as heck design a robot that lays ultra-lightweight sand bricks back here on Earth.
There are some limited instances where it's desirable to have a crew service a payload, and STS was designed for that. To my admittedly limited knowledge, NASA doesn't have the technology required to travel back in time and smack the decision makers who created requirements that forced STS to be the kluge that it was upside their heads. So, as long as we have lemons we make lemonade.
The two "accidents" in the STS program were more willful ignorance on NASA's part that resulted in destruction of flight hardware. Those kinds of things happen when you ignore your engineers.
If LANL can fabricate a new class of reactors for satellite power in less than a year and for less than a million dollars, then for a few billion not wasted on redundant capsule systems, I'm quite certain that a gas core reactor is in the cards for us. That's where I want our development dollars directed. VASIMR and other NEP technologies may be entirely feasible once nuclear fusion is perfected, but let's not hold our breath waiting for that to happen.
Getting back to the question posed in the OP, can we use the uber gas cans as raw materials for construction of ISS modules or Mars landers from an orbital manufacturing facility aboard ISS? I think so. If the money has already been expended to push the ET's to orbital velocity, then dumping them into the ocean is egregiously wasteful. So what if some gas is required to circularize the orbit? The gas can still has around 1% of the gas in it at MECO. Is it an impossible engineering task to develop thrusters to convert that residual to a circular orbit?
The core stage of SLS will never achieve orbit. It's a big dumb rocket. Even though SSME was designed to be reusable, SLS will never be able to deliver its core stage engines to orbit.
Wait. What? I thought SLS Block I without an upper stage was supposed to push 70t to LEO. Is that incorrect?
Second, SLS practically is the Ares rocket from Mars Direct. In fact, from what's posted online, designers are considering 5 main engines for block 2. So with 5 SSME in the core stage, a pair of J-2X for the upper stage, and a pair of SRBs, that is Ares. The only difference is 5-segment SRBs instead of 4-segment. One option I wish they would consider is 5 SSME with 4-segment SRBs. That skips the vibration problem with 5-segment boosters.
Would composite casings mitigate the vibration problems with the 5-segment design?
One design feature is to use 4 RL-10 engines instead of a pair of J-2X. Interesting: J-2X produces 1307 kN thrust (133,276.9 kg force), Isp=448s. RL-10 produces 110 kN thrust (converts to 11,216.878 kg force, but you should round off to 3 significant figures), and Isp = 450 to 465.5 seconds. Why is Isp in vacuum a range? So 4 RL-10 engines provide much less thrust, but a little better Isp. If you burn those engines longer, could it provide more delta-V? That's one thing they're talking about.
From an engineering complexity standpoint, is there a good reason why right-sizing the core stage design to achieve the desired throw isn't preferable to adding a stage atop the core stage? Most efficient? Obviously not, but what insane amount of money will be required for a man-rated second stage?
Separating cargo from crew is generally a good idea, but we need a launcher for crew. SLS is that launch vehicle.
I agree on the first point, but SLS need not carry crew. We have existing hardware to blow mad money on LEO transport service. If each Orion/SLS flight costs just as much as a Space Shuttle flight or more, then Orion has no purpose, apart from preventing development of real space exploration hardware.
Here's why I want to do this.
- Increase flight rate to maintain workforce and its proficiency at manufacturing flight hardware
- Skip RL-10/J-2X/DUUS/EUS and other upper stage acronym soup chemical engine development to ensure funding for gas core nuclear rockets, nuclear power solutions for exploration vehicles, and methane powered engines for Mars landers is available
- Gas core nuclear rockets eliminate the need for heavy aeroshells required for risky aerobraking maneuvers to achieve Mars orbit and the attendant weight of propellant required for Mars orbital insertion, thus keeping individual SLS payload weights within a margin that SLS with advanced SRM's could realistically achieve
- Ensure continued availability of funding for advanced long term storage of cryogenic propellants for the nuclear rockets
- Provides both reason and utility for the continued existence of ISS
- NASA could partially fund development of Dragon Rider for propulsive landing of crew on Mars so the cargo landers would not have to be man rated or require separate designs for cargo-only versus crewed landers
I still want to retire STS and SLS, but at a time when their capabilities are no longer of utility to our manned space program.
I think that the STS program should be re-activated immediately and all orbiters refurbished and upgraded for a specific purpose, retrieving SLS hardware and orbital assembly and servicing of payloads launched on SLS.
Somehow the various contractors will make Orion's development and use every bit as expensive as the far more capable Space Shuttle. Orion was developed for a manned lunar program that no longer exists. It has no purpose for a Mars mission. The proposed lunar fly-by stunt is just that.
If it were up to me, I would follow most of the recommendations proposed for the Space Shuttle upgrades. Specifically, the avionics and fuel cell upgrades, landing gear improvements for greater landing weight, and channel wall nozzles for the RS-25's are all worthy of development dollars. Additionally, to eliminate the insane amount of manual labor that refurbishment of the orbiter TPS requires, a robotic TPS refurbishment and inspection capability should be developed. Cancellation of Orion would make available the required funding for the necessary Space Shuttle upgrades and operation.
Here's my proposal for a re-activation of the STS program:
Presumptions:
I presume no more than 2 SLS launches per year and an equivalent number of STS launches to retrieve the RS-25's. I also presume that work on the Dark Knight boosters moves forward to lower the cost of the SRM's and increase their performance. The general idea is to remove the most costly aspects of SLS (expenditure of expensive reusable hardware) and STS (labor intensive reusable components) and increase the flight rate of common hardware.
Problem:
The RS-25E development programs have to contend with the fact that RS-25 was designed for reuse and is way too expensive for use in expendable launch vehicles.
Solution:
SLS would become the cargo-only rocket that it always should have been, STS would infrequently transfer crew and cargo to ISS and space exploration vehicles, and it would return the costly RS-25's from SLS rockets.
Pre-req's:
The SLS engine barrel would require a slight redesign to separate it from the tankage and subsequently circularize its orbit for retrieval of the RS-25's.
The RS-25 would require a redesign to permit easy removal of the nozzle extension from the powerhead.
Intended Use:
The first ISS module that a STS return-to-flight mission should carry would be a machining module to repurpose the aluminum from the engine barrel to eventually construct space station module shells in orbit. It demonstrates the capability to use largely autonomous machining centers operating in microgravity to have them turn SLS scraps into construction stock for ISS or spare parts for space exploration hardware. At a later date, if it is possible to boost the entire core stage into orbit, then the capability to entirely reuse the overwhelming majority of SLS flight hardware becomes possible.
Conop:
Each STS mission would follow a SLS mission to transfer supplies or modules to ISS, take space exploration crews to their space exploration vehicles docked at ISS, and retrieve RS-25's from SLS missions to repurpose the materials from the engine barrel and eventually the tankage, too.
Goal:
ISS would finally be a space exploration mission support tool. The machining unit would turn the microgravity experiment into a space-based manufacturing facility to construct mission hardware from SLS remnants, and a staging area for space exploration crews/vehicles.
Conclusion:
I have no idea what the technical challenges would be with this solution or if it's reasonable, but the payload capacity is there if the landing gear receive the upgrades.
Apart from testing the ability of the Mars landing craft to make a landing on another body, verifying that the Mars habitat and power supply can be reliably run for a period of two to four years afterwards with autonomy, and testing of crew environmental support solutions, I see no other purpose for lunar missions.
It's obvious that no spacecraft with a few weeks worth of supplies onboard is ever going to take humans to Mars. Degrading the capability of the service module to hit mass targets for Ares I severely restricted its capabilities for lunar missions. Apart from taking humans to ISS, Orion/SLS has no practical utility at this point with the Altair program cancellation and a Block I SLS configuration that can't put that much mass into TLI anyway, so it's no better than the Space Shuttle in terms of cost and can't even perform the mission it was built for.
If NASA insists on launching Orion on a flying pork barrel, I mean SLS, then there was no reason to retire the Space Shuttle. The cost of an Orion/SLS mission will be the same as a STS mission and there's no landing craft to land on anything with, so what's the point?
NASA's Space Shuttle was not unreliable, the humans involved simply ignored the problems and the result was destruction of flight hardware.
Given the cost differential between Orion/SLS and Dragon/Falcon 9, I'd rather NASA did the following:
- Continue work on SLS, absent any other launch system with comparable capabilities; SpaceX BFR is a paper rocket at this point
- Work with SpaceX to man rate Dragon, a system proven sufficient for LEO taxi service; if Orion is man rated before Dragon I'll be suitably impressed
- Cancel Orion, as it's not required and there's no compelling reason to drag a capsule all the way to the moon or Mars and back
- Restart work on Altair and EDS with an eye towards lander and/or EDS reusability and refueling from propellant depots
- Use SLS to launch the Altair/EDS combination and propellant depots
- Put a small inflatable habitat module atop Altair instead of a confining tin can
- Work on EOR with Altair for lunar missions
If there's still money burning a hole in NASA's pockets:
- Composite tanks for SLS
- Composite SRM casings