My question is twofold. 1) IRL are there any impediments that I'm unaware of (apart from a large bag of money ) to doing this and if so how difficult would they be to overcome and 2) Once you know this what sort of missions could be enabled by it?
NASA appears to have a horror of multiple launch missions. A pathological fear that some half fueled payload will be stuck in space due to launch mishap, delayed pad refurbishment or whatever.
It takes a couple of days to reconfigure the range for a new flight from the same location. So, that means one location at a time for a launch, separated by a couple days to the next reuse of the same location. Then you're going to need to worry about launch windows all to the same plane and then rendezvous from the inevitably different phase angles, and the propellant and control that will take, plus the ability of the earlier payloads to loiter while they wait.
It would require a massive campaign of AR&D to be useful for anything. If cooperative, every launched element will need to be a full autonomous spacecraft with GN&C, power , attitude and propulsion etc. If uncooperative, you need a fairly involved "tug" element to get the full stack together. Depending on how things are configured, you may need to transfer propellants, either storable and/or cryo.All these technologies are relatively low maturity in US, so nobody is going to pay for 60 ton payload that relies on all that.
Note that both COTS winners for the cargo contract to the ISS use automated docking and rendezvous systems already
ISS? How many launches over how many years to build, fuel, supply, and crew that multiple launch mission? There were twelve launches to ISS alone just this year.
Which brings up another point - why only U.S. launches? Throw in Proton, Ariane 5, H-2B, Zenit, and maybe others and the mass to orbit grows in a hurry.
The launch range reconfiguration restriction could be nullified with appropriate funding. Back in the day, rockets flew from the Cape within hours of each other, sometimes on the same day.
Quote from: john smith 19 on 12/31/2013 12:12 amNote that both COTS winners for the cargo contract to the ISS use automated docking and rendezvous systems alreadyNeither of them docks, both are berthed.
I think the technology for autonomous spacecraft is mature enough I'd have no issues having it be part of a mission architecture.
On a Mars mission I'd trust it a lot more then I would the present state of development in tightly closed loop life support.
Though what's more important to me then the payload all at once is what kind of payload can be orbited over the course of six months using existing launch vehicles.
That is useful to know. In an era when automation is relatively cheap to do it's surprised me that the time needed between launches should go up.
Quote from: john smith 19 on 12/31/2013 10:33 amThat is useful to know. In an era when automation is relatively cheap to do it's surprised me that the time needed between launches should go up. It is an issue of limited shared resources, where automatic has little use. The range is manned for 5/40 with overtime and creative shifting used to cover other hours. The range operator is like a launch team, where the same team works all the launches. There has to be a break between ops. Additionally, there are items like tracking cameras that would have be moved to cover different launch pads. voice channels have to reconfigured and verified between different control centers. Roadblocks have to be moved around. There is more, will need some time to think.
Quote from: edkyle99 on 12/30/2013 11:50 pmISS? How many launches over how many years to build, fuel, supply, and crew that multiple launch mission? There were twelve launches to ISS alone just this year.A fair point but ISS is very much an outlier where NASA is concerned. It's not going anywhere and it's not a stage that's expected to take a payload anywhere.
... I'm not sure what the H-2B launch record has been like. As for US launchers only the answer is ITAR, and the ensuing row by the Legislature of foreign launchers.
1. I was wondering how many separate ranges there are that could operate at the same time. My instinct is Wallops Island for Antares II and whatever the resources are at Kennedy Space Centre / Cape Canaveral Air Station, but I'm not sure how that's split up. Is that 2 or 3 ranges?2. I'm guessing but do you know if the Delta IV /Atlas vehicles interface to the range in roughly the same way? I mean that it would be easier switching from covering a Delta IV Heavy to an Atlas V launch than say Delta IV Heavy to F9?3. So far it's looking like you'd need additional tracking cameras to avoid the delay of moving them around, faster voice and data channel re-configuration processes and an extra supply of roadblocks (and staff to man them?)
Planning a LEO rendezvous mission that requires a big launch surge in a short period of time creates more opportunity for mission failure. If one flight falters, the whole mission is lost.
If the mission is designed for gradual buildup, over many months (or even years), and for long-duration on-orbit propellant storage, flight failures can be tolerated. (ISS is still there, despite the loss of Shuttle access for two years and despite an unprecedented Progress launch failure.) An extra plus would be that no new launch pads or extra launch range expenditure would be required to support the surge.
I see ISS as a valuable (unparalleled actually) teacher when it comes to LEO buildup missions. We know, for example, that the flight pace needed for ISS is possible, not just technically but financially and politically. Why not plan to use similar techniques for beyond LEO?
For ISS and other purposes, probably 70-90 tonnes of storable hypergolic propellant is routinely orbited every year. The stuff lasts for years and years - even decades - in orbit, and that is not a theory, it is proven daily by hundreds of operating satellites .
H-2B has four launches and no failures since 2009. Smaller H-2A has flown 22 times with one failure since 2001. Re: foreign launchers - U.S. astronauts are launched, and will continue to be launched for years to come, by Russia. U.S. satellites are orbited by European and Russian rockets. The Pentagon and NASA both depend on Russian rocket engines (Atlas 5 and Antares), and on a Ukrainian built stage (Antares), etc. Orion will use a European service module and SLS will use tank panels made in Germany. That "foreign" bridge was crossed long ago.
I don't want ISS to go away in order to support this big campaign, so Ed's point that we have the political will for multiple launches, while true, doesn't necessarily mean we have enough will for the launches needed to sustain ISS PLUS this campaign.
Neat exercise though.
To Jim's point, ranges can have more cameras and can be staffed 24/7 and etc. It just takes bagfuls of money and the NEED. As long as there's another way, there may not be the need. Or not the apparent need.
Quote from: edkyle99 on 12/31/2013 04:11 pmIf the mission is designed for gradual buildup, over many months (or even years), and for long-duration on-orbit propellant storage, flight failures can be tolerated. (ISS is still there, despite the loss of Shuttle access for two years and despite an unprecedented Progress launch failure.) An extra plus would be that no new launch pads or extra launch range expenditure would be required to support the surge. True. But you have 2 problems where NASA is concerned. 1) Once outside of LEO NASA are convinced that LO2/LH2 is the only serious option for large vehicles. 2) Despite 5 decades NASA has flown no actual flights to demonstrate long term (and in this context I mean as little as 1 week) cryo storage.
It is hard to beat LH2 for high energy missions, but a large number of NASA's beyond Earth orbit missions were not boosted by hydrogen fueled stages. Many of the Mars missions (Pathfinder, Spirit, Opportunity, Mars Global Surveyor, Mars Odyssey, and others) were launched by Delta 2 rockets with their hypergolic pressure fed and solid fuel upper stages. Galileo and Magellan were boosted by IUS solid rocket motors. The most recent lunar mission, LADEE, went up on an all-solid rocket, with final boosting by LADEE's own on-board storable propellant system. Orion will use the tried and true hypergolic propellant combination, as likely will any commercial crew spacecraft and as already do the commercial cargo spacecraft.
Cryos are going to boil off from a depot, especially in LEO and especially liquid hydrogen, no matter how good the insulation. That lost propellant mass is extra mass that must be launched, which obviously will offset some or all of the performance benefit offered by the higher specific impulse of the fuel. It all makes me wonder why storable hypergolics aren't seriously contemplated for larger scale deep space missions.
My pragmatic response. Launch the payload on multiple launches as close together as possible to enable cryo use with minimal boiloff.
Actually it's not that big a mystery. When NASA do an architecture study and include storables that increases the mass to orbit by a lot.. Plus the fact that AFAIK there are no pump fed storable engines in the US inventory. IIRC the Shuttle OMS got ab out 312secs, the RL10s about 450sec plus? Agena seemed to be the last big one.