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GCNRevenger, where does it say that Shuttle-C can't even hit 100MT, even with the "stretch" version? Thiokols]http://www.safesimplesoon.com/heavylift.htm]Thiokol's web site lists Shuttle-C lift capacity as 170,000 pounds, but that version only has 2 SSMEs. My calculations show 104.7 tonnes to 185km orbit at 28.5° inclination using 3 SSMEs, 2 OMS pods, and including all the recovery hardware. That uses a pair of 4-segment SRBs and a standard ET.
And dropping one SSME reduces the performance that much? Anyway, since that is apparently the option being considerd, then it doesn't matter what your numbers say, as this is likly the model Thiokol is trying to sell.
It is likly possible to make the basic side-mount Shuttle-C lift 100MT, the question is, why would you want to? If you are sticking with the basic Shuttle "shape," then that will limit your payload diameter...
http://www.astronautix.com/lvs/shuttlec … uttlec.htm
http://www.astronautix.com/lvs/hear2011 … ar2011.htm
...side-mount SDV would have trouble accomodating large diameter payloads, such as Mars vehicles, which should be at the minimum around 8m wide, which I think is a big reason that NASA DRM-III calls for Magnum rather then Shuttle-C. If you need the inline version anyway, then don't bother with the side-mounted one. Plus, for DRM vehicles that don't have a shroud, now you have to make them strong enough to take the place of Shuttle's backbone and add appropriate linkages. Just put the thing on top! It solves so many problems.
I also bet that your figures are, like most things you come up with, optimistic to a fault... Structural mass for the faring's "backbone" (that inline wouldn't have), the mass of your engine pod's recovery gear (heat shield, parachutes, extra power systems, engine bell covers, etc)... all this subtracts from your figure, which I am pretty certain would kill any of this 100MT+ business using the standard Shuttle propulsion systems.
I am still quite convinced that the development costs/time coupled with the inferior payload volume/mass coupled with the added infrastructure needs makes the whole engine pod a terrible, terrible idea. If it costs a billion dollars to develop, which I think is very reasonable and perhaps even a bit low, then Shuttle-C would still have to fly probobly 20-30 times to save a single penny (~$10-15M savings per SSME with refurbishing & reintegration expenses). Oh, and you will still need to build several of them, so you have a contingency if recovery fails... at how much each?
*Invokes the Nike rule: Forget the recoverable pod! It won't save much money even if it does work, and adds extra development cost/time (which NASA has to "pay up front" from its limited supply) and limits vehicle capacity. Just have NASA/MSFC/Rocketdyne build a low-cost one-shot SSME! For goodness sakes, Just Do It!
[i]"The power of accurate observation is often called cynicism by those that do not have it." - George Bernard Shaw[/i]
[i]The glass is at 50% of capacity[/i]
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Nope. I calculated engine mass from NASA published figures. OMS pod mass is also published, as is OMS fuel. I used the mass of a composite fairing for Titan 4B. Helium mass was calculated from published volume and pressure figures. Helium tank mass was calculated from volume. Parafoil mass was scaled from the X-38 parafoil. Ablative heat shield was based on the Apollo command module heat shield, scaled for engine pod mass vs capsule mass. Internal thrust structure is the one for Endeavour.
Remember I did say the calculated lift mass includes the payload adapter which clamps onto the thrust support structure, as well as any structure necessary to hold the payload together. If you launch a single module you won't need any payload structure, but a collection of loose pieces will.
By the way, there are reasons the Shuttle-C configuration listed in Encyclopedia Astronautica has such a low lift mass:
1) 2 main engines instead of 3
2) a full cargo bay with all its structure
3) lift mass quoted to 400km orbit at 28.5° inclination
Since you challenged me, I replaced the "fuselage" figure from my spreadsheet with separate line items for internal thrust support structure, skin, and DurAFRSI thermal blankets. I found the OMS pods have graphite/epoxy sandwich skin with graphite/epoxy ribs, aluminum cross brace and titanium tank support frame. I left the OMS pods as a unit but the rest of the skin I calculated area and used the mass of a Contrives fairing: graphite/epoxy sandwich skin with foamed aluminum ribs. I calculated DurAFRSI thermal blanket mass for all sides and OMS pods. I did discover a mistake: I thought published OMS fuel mass was for both pods, but it's for just one; that doubles OMS fuel mass. I also found precise OMS pod dry mass; it's more than I thought. That significantly reduced lift mass. I haven't included the base heat shield or communications (command & telemetry), but have included flight computer, main engine actuator hydraulics, and a single APU with fuel for 15 minutes. Without aerodynamic control surfaces or landing gear the APU isn't needed during atmospheric entry or landing. I calculated weight for the improved APU that deletes the water spray system for the gas generator valve module and fuel pump.
The result is significantly reduced, primarily due to OMS:
87.4 tonnes to 185km orbit @ 28.5°
74.68 tonnes to ISS
If we keep this up I'll have blueprints for the damn thing. I guess here we start to talk about 5-segment SRBs.
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Doesn't the fact that the SRB's are already man rated make them significantly more ideal than any other options? I would think so, myself.
Some useful links while MER are active. [url=http://marsrovers.jpl.nasa.gov/home/index.html]Offical site[/url] [url=http://www.nasa.gov/multimedia/nasatv/MM_NTV_Web.html]NASA TV[/url] [url=http://www.jpl.nasa.gov/mer2004/]JPL MER2004[/url] [url=http://www.spaceflightnow.com/mars/mera/statustextonly.html]Text feed[/url]
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The amount of solar radiation reaching the surface of the earth totals some 3.9 million exajoules a year.
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So you included the mass of structure needed to connect the fore and aft external tank struts? You will certainly need something, since the off-axis push from the engines I'm sure needs considerable structure to keep from bending the aft strut. If Shuttle-C doesn't come with it, then your payload will have to, which complicates its structure substantially. Hidden charges add up...
Oh, and another thing, did you account for the wasted thrust/propellant of the off-axis engine nozzle angle?
Those figures are starting to sound fairly close for payload, though you will probobly do well to include a signifigant mass budget item for margins (manned vehicle structure margins are 140% even), and the 15min supply for APU fuel isn't enough, you need enough fuel to make several orbits in order to come down exactly where you want, especially for ISS flights.
Blueprints? Hardly... there is a long, long, long way to go before that stage of development. Anyway, if it does or not doesn't change the biggest points of my argument... the engine pod may very well work and be quite practical to engineer. The trouble is:
-That even if it does work, it probobly won't save that much money when you total the development costs, so its a bad investment to begin with, as it adds too much complexity and risk to SDV.
The whole point of SDV is that its simple and available right now. A complex thing like an engine pod, which is itself a completly new space vehicle only somewhat less complex then CEV, is neither.
-Limits payload diameter, which is crucial for Mars ships or future large contiguous objects.
-Still a bit less efficent than in-line vehicles pound for pound, plus the same launch infrastructure probobly can't support both an inline and side mount SDV.
-Increases total mission complexity & risk, that loss or reprocessing delay of the engine pod could be catastrophic to launch schedules if a launch surge is nessesarry (like for a Mars expedition). Think of the increased per-flight cost of expendable engines as insurance.
Edit: Oh, and did you include air bags for engine pod impact in your mass budget?
Edit Edit: Reflections... Another serious problem is, that the development for the engine pod would have to proceed apace with the rest of the SDV HLLV, which is to say, that NASA would have to pay the large development cost up front. NASA has absolutely got to keep development costs, time, and risk under control, which the engine pod adds substantially.
[i]"The power of accurate observation is often called cynicism by those that do not have it." - George Bernard Shaw[/i]
[i]The glass is at 50% of capacity[/i]
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It's really embarrassing that my source of information presented the dry mass of the OME (the engine alone) in a way that implied it was the mass of the whole OMS pod, and the same source implied the fuel for just one pod was fuel for both. That introduced significant error.
However, your comment about off-axis thrust completely misses the point. I took lift mass of the Shuttle orbiter and cargo together, then subtracted the mass of the engine pod and fairing. The remainder is the new lift mass. Since the starting point was the Shuttle orbiter, any issues for off-axis thrust are already built in.
And no, you don't include margins. The Shuttle orbiter already has all the margins necessary for a man-rated vehicle. Any further "margin" is just waste. Actually correct engineering determines the maximum stress upon a part, and designs that part to withstand maximum stresses in all dimensions with any accumulated fatigue. That's it, any margin beyond that is just wrong. The margins you are used to hearing are simple estimates for fatigue.
APU: the Shuttle-C engine pod eliminates all use of hydraulics other than main engine gimbals. Main engines fire for 8 minutes during launch, and the APU is started 5 minutes before launch. The 15 minute fuel supply has 2 minutes of extra fuel. Those 2 minutes are plenty for alternate flight profiles that might extend main engine operation, or a brief pre-launch hold.
Do you want me to include mass for the base heat shield as well as air bags? Fine, then provide them. If you can't provide figures then you're not qualified to criticize someone who does.
As for multiple units: that is the sort of stupid thinking that led us to the budget crisis we have with Shuttle. Government work often makes the argument "why purchase just one when you can have two for twice the price?" Commercial industry knows the answer: why on Earth would you want to double the price? That's stupid! Commercial industry always demands that every capital investment must be continuously utilized to justify its cost. Never, ever, ever, buy an expensive piece of capital equipment just to leave it sitting in a hanger. If the equipment is mission critical, then ensure it can be replaced; not by buying it now but ensuring the vendor will continue to support it so it can be purchased when needed. Creative alternatives are strongly encouraged, such as scavenging parts from decommissioned equipment to serve as spares for mission critical equipment. That means you only build one engine pod. Shuttle orbiters are a reserve of spare parts to build a second engine pod if and when it's needed.
Also notice I calculated just a single Commercial Off The Shelf (COTS) Single Board Computer (SBC) designed for communication satellites. I also include just a single APU, not 3. This is plenty for a cargo flight but the lack of redundancy makes it not man-rated. I keep say "separate cargo from crew". CAIB said that, the report from Challenger said that, how many times does it have to be said? Send crew via dedicated crew taxi, rendezvous with the Mars ship in LEO.
Development of the engine pod really is development of Shuttle-C. The launch stack would be the existing ET and SRBs, existing fairing, and the engine pod. Recovery by a stock flatbed truck (purchase off the lot). MLP would require struts for the engine pod instead of wing supports. Each payload would require its own mission design to hold it together during launch.
Time is getting to be a real concern. Although I think Shuttle-C could be finished relatively quickly, use to complete construction of ISS requires it real soon. To be done in time development of Shuttle-C should already be underway.
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"If you can't provide figures then you're not qualified to criticize someone who does."
*Coughs* Excuse me Robert, I very much can be critical of figures as any reasonably intelligent person... particularly when you are producing them from "sources."
"...that is the sort of stupid thinking that led us to the budget crisis we have with Shuttle... "
What got us into Shuttle wasn't plain vanilla government inefficency, it was intentional taxpayer fraud on NASA's part to create an endless supply of make-work money for engineers. Every goal that NASA has set its mind on it has suceeded, and this the true goal of Shuttle (and by extension ISS and HST), is no different.
"Each payload would require its own mission design to hold it together during launch."
Passing the buck are we? The launcher should be standardized as much as is practical, so that NASA doesn't get tempted to customize too much and drive development costs out of control. And again, the Shuttle-C configuration places limits on payload diameter, which should be at least 8-9m dia for Mars vehicles. All past studies of Shuttle-C max out at 7m. Inline is the way to go, for 80, 100, or 120MT class payloads.
"...then ensure it can be replaced; not by buying it now but ensuring the vendor will continue to support it so it can be purchased when needed. Creative alternatives are strongly encouraged, such as scavenging parts from decommissioned equipment to serve as spares for mission critical equipment. That means you only build one engine pod."
What are you talking about? Just build a single pod? Nonsense! You would have us put our entire HLLV line in the hands of a single working set of engines? And if that single set of engines had the slightest problem, all our launch plans would be scuttled? What a terrible idea! Thats ridiculous... And what if you wanted to launch two (or more) HLLVs in rapid sucession (like a DRM payload and TMI stage)? Waiting and betting on engine pod reprocessing going without a hitch isn't an option when you have an expensive nuclear powerd vehicle waiting in orbit for the next flight to make the departure window.
Oh, and you want to regularly throw money at a corporation so it retains the manpower/machinery/etc to hurry up and rush to build a brand new engine pod with 10-20+ year old parts for the life of the design? And get it done so fast without tons of pod-specific spares laying around? More nonsense! You really may as well just have a spare pod for goodness sakes!
"Creative solutions" are just AltSpace nonsense jibberish buzzwords, we need real planning to get anything done, and if your contingency plan is to have a company with limited liability try and cobble together museum pieces in a huge rush... that isn't a plan, its planning to fail. Frankly, I think the chances that the engine pod will fail on each and every flight or otherwise have to be taken out of service for repair are sufficently high that you would need MULTIPLE pods, which severely impacts the economics of the concept, which are marginal at best versus expendable engines counting development... And then there is the tradeoff for lower total SDV development costs and less risky development too.
"Actually correct engineering determines the maximum stress upon a part, and designs that part to withstand maximum stresses in all dimensions with any accumulated fatigue. That's it, any margin beyond that is just wrong. The margins you are used to hearing are simple estimates for fatigue."
I would like a second opinion on that.
[i]"The power of accurate observation is often called cynicism by those that do not have it." - George Bernard Shaw[/i]
[i]The glass is at 50% of capacity[/i]
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Wouldn't it be better to design an engine pod for rapid turn-around rather than build multiple pods? Notice I completely eliminated all heat shield tiles on the engine pod. That was deliberate, to eliminate labour required to inspect and replace tiles. Thermal blankets are durable so they don't require replacement, and the ablative heat shield is designed to be replaced as a single piece simply by unbolting the old one and bolting on a new one. I saw a TV interview with an astronaut who is an engineer (Julie Payette) who said Space Shuttle main engines are removed for service on a specific schedule (number of flights), not after every flight. I wish she said how many flights.
The http://www.boeing.com/defense-space/spa … .html]SSME also known as RS-24 is still current and available. It was manufactured by Rocketdyne, now owned by Boeing. http://www.aerojet.com/program/display. … _ID=25]OMS engines manufactured by Aerojet are also current and available. But don't buy new parts if you have existing parts in inventory. The COTS SBC computer I quoted is new, but a Lockheed Martin engineer asked me once where to find it so I don't want to publish it. NASA recently held a conference specifically for COTS control computers, so there should be more than one, but I only know one. If someone wants to know more then hire me as a consultant.
As for "sources", you try going through http://www.spaceflight.nasa.gov/home/in … t.nasa.gov and pull out the pertinent technical details. I discovered the mistake by checking with http://www.astronautix.com]Encyclopedia Astonautica, that one is much more readable. I got technical details of DurAFRSI from a web site of Ames and a web site of the http://www.zyn.com/flcfw/fwtproj/Durabl … nufacturer who made it for them. Both DurAFRSI sites are readable. I would link the Ames document but I saved the .pdf file to my hard drive, the link isn't active any more.
"Creative Solutions" don't come from AltSpace, they come from 24 years of working as a computer programmer in commercial industry. Ok, part of that was working for government, but most of the time I worked for commercial companies. The smaller the company the more creative.
As for safety factors and engineering for extreme cases, I'll quote from one conversation I had with an engineer for Bombardier Aerospace. I told her that I heard the ablative heat shield of the Apollo Command Module was twice as thick as it needed to be and astronauts were thankful. She replied that the heat shield was probably designed for some extreme contingency condition. I learned from her that the over-design is not some safety factor multiplier, but rather designed for a specific contingency. Her name is Janyce Wynter. She's also the one who gave me the safety factor multiplier for ultimate tensile strength and the factor for yield tensile strength for calculating 'S' factor, which is used to calculate pressure tank wall thickness. The two factors are different, and there's a reason. I don't know the reason, I defer to her knowledge as an aerospace engineer.
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"Wouldn't it be better to design an engine pod for rapid turn-around rather than build multiple pods?"
NO, no it wouldn't be! The chance the pod will fail or need time-consuming repair are pretty signifigant, signifigant enough that it would be rank foolishness and utterly incompetant to bet that there wouldn't be any problems with it. Having a contingency plan for the pod to fail is the only sane way to run the SDV program.
Contingency plans that can't produce and integrate a new pod in a VERY short time frame are wholey unacceptable, that since we will be using SDV for Mars then it is vital and entirey non-negotiable that we be able to launch in fairly rapid sucession (or otherwise on-time for some mission need). Think about this: for your time-sensitive mission to suceed, you would not only have to rely on this flight going well, but the last flight too! AND there being timely, reliable turnaround on the fragile pod that must survive the rigors of reentry & landing powerd by first-generation reuseable engines... and do it on cost too.
Building a new pod from scratch or museum-bound pieces in the matter of a few weeks is not happening (period), so a backup pod in fuel & fly shape is nessesarry for your pod scheme. In fact, I think the liklihood of loss or reprocessing delay is serious enough to build two or three backup pods, especially for NASA DRM-III that requires multiple flights in a few months or other time-sensitive mission.
If the things cost $250M each to build, $1Bn to develop, and only save you ~$30M a flight (how much does a 7m heat shield cost?), then why bother? Expendable engines weigh less to boot. Put them on the bottom of the tank, three or four depending on payload, and you can lift bigger (up to 10m dia, Saturn-V sized!) payloads, plus buy a few more tonnes "for free" with on-axis thrust.
""Creative Solutions" don't come from AltSpace, they come from 24 years of working as a computer programmer in commercial industry. Ok, part of that was working for government, but most of the time I worked for commercial companies. The smaller the company the more creative."
Like I said, AltSpace jibberish buzzwords... code-speak for cutting corners, abandoning sane planning, plus woeful and radical overconfidance.
[i]"The power of accurate observation is often called cynicism by those that do not have it." - George Bernard Shaw[/i]
[i]The glass is at 50% of capacity[/i]
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Oh come on, after each of the last two failures the Shuttle was grounded for 2 years. Obviously I don't agree it should have been that long, but it was. America has demonstrated a pattern. An unmanned launch vehicle shouldn't be grounded that long, but X-43 was grounded for 4 years after it's failure. If your concern is Mars missions, launch windows open every 26 months. If you think NASA can launch a replacement after a failure so quickly it's within the same launch window, you're dreaming.
Again I emphasise, making operation economically viable must follow commercial practices. That dictates you don't buy a second unit of a multi-million dollar piece of equipment unless the first one is in continuous operation and is restricting use schedule. Never, ever, ever buy multi-million dollar equipment just to leave it sitting on a shelf. If you think you can launch Shuttle-C or any HLLV once every 2 weeks on a continuous schedule, you're dreaming. The Shuttle orbiter is launched once every 2 months, I don't think you'll fill an HLLV launch manifest even that full.
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As with many things, its a matter of timing... in order to pull off a Mars program, and most likly to keep a Lunar base in operation, we will have to start making time-critical launches in relativly close sucession to eachother. We have to be able to do this to meet the modest but still constrained launch windows to get to Mars; fuel boiloff, orbital debries damage/aging, and crew rendezvous means that you will have to put multiple (say, 4-6 for DRM) flights up as quickly as you reasonably can. A Lunar program has similar though a bit less strict constraints for fuel boiloff and crew rendezvous.
Two weeks is probobly out of the question, little doubt about that, but I think that four weeks is not unreasonable to achieve nor to expect from SDV vehicles for a "surge" launch manifest. Such a rate would solve boiloff and storage problems neatly, with margin left over. Readying multiple vehicles in the VAB simultainiously is the best way to do this with SDV, and you can't do that with only one set of engines between them.
And again, it is dumb to plan on the engine pod working perfectly and the reprocessing going without a hitch. A total catastrophic failure of the whole vehicle is one thing, but having a single engine out, or more likely damaging/destroying the pod during return/recovery, is quite another. It is only sane and prudent to plan for this happen, and happen at the worst possible time.
There is no denying your pod would be increasing total per-flight risk, since the launch vehicle now has to perform an extra seperation (including fuel lines), accurate maneuvering, reentry, midcourse/terminal steering, and finally withstand impact undamaged. And do it all again, time and time again, without loss or serious damage... and do it cheaply. And what if your ground crews miss some damage? Well...
The only solution therefore is to have a backup. A fully functional identical copy, sitting in an old Shuttle hanger perhaps, ready to be trucked to the VAB in an emergency. If you intend to operate the engine pod on a regular basis, you will need to have many millions of dollars of spare parts & equipment laying around anyway. You can't "pull an Endeavour" out of your hat using spare parts in time for a constrained launch schedule, so the only solution is to have a spare pod fully assembled and ready to deploy. This will cost probobly around $200M, which further erode the dubious economic bennefit of the pod scheme... particularly when:
-Side mounting reduces total payload mass versus axial
-Engine pod reentry equipment & structure subtracts from payload mass signifigantly
-Side mounting limits payload diameter too much, to around 7m (versus ~9m for DRM, ~8m for MarsDirect, both launched on axial SDV)
And lets not forget, it would signifigantly increase the SDV development, startup costs, and risk substantially, which is precisely what NASA is trying to avoid by going this route in the first place. You could not develop SDV for a reasonable sum if you were to have two seperate designs (one pod based, the other reduced cost expendable) anyway, so the choice is clear... expendable all the way.
Edit: Oh! And axial mounting makes extra large (120MT class) payloads and escape velocity (read: Moon/Mars supplies, megaprobes, mega space scopes) payloads much easier thanks to the simplicity of adding a heavy upper stage...
Taken together, I think that the superior payload capacity (mass and volume), flexibility, efficency, simplicity, development cost, reliability, and ease of rapid launch really seals the deal against the side-mounted engine pod.
[i]"The power of accurate observation is often called cynicism by those that do not have it." - George Bernard Shaw[/i]
[i]The glass is at 50% of capacity[/i]
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It would be more than worth our while to leave the engines on the tank, at least for the inline option.
The tanks already carry more fuel than they use. After second stage seperation the tank can be hoisted to a parking orbit where it can be collected for later use.
After a little Bob Vila action, well have the cheapest Mars ship, habitat, or lunar base ever.
"Yes, I was going to give this astronaut selection my best shot, I was determined when the NASA proctologist looked up my ass, he would see pipes so dazzling he would ask the nurse to get his sunglasses."
---Shuttle Astronaut Mike Mullane
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Higher development cost for a reusable Shuttle-C engine pod with the same performance as the Shuttle orbiter? Higher than an axial configuration that completely changes acceleration load stress, thrust stress, and aerodynamic loads? Higher development cost that re-engineering the external tank? Higher cost than rebuilding all 3 MLPs to move the exhaust hole? Remember, to sustain the launch schedule you're promoting you can't adapt just one http://science.ksc.nasa.gov/facilities/mlp.html]MLP, you'll need all of them.
I still think cost control is more effective to design an engine pod that requires minimum labour to process so it can launch in less than 2 weeks. All those guys who designed vehicles for the X-prize were able to do it, Burt Rutan's vehicle SpaceShipOne was just the one that won the contest. The launch schedule for Delta IV, Atlas V, or even Titan 4 doesn't keep up with 2 week turn-around. There were 4 Shuttle orbiters before the Columbia accident, and they launched every 2 months. I doubt engine pod handling will be the critical factor to attain a rapid launch rate.
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Oh, hi Commodore. Re-using spent external tanks has been proposed before. Actually, the full capacity of the tank is used. With a full tank the Shuttle is only able to lift 16.050 tonnes of cargo to ISS. As ISS falls to a lower orbit that lift capacity will increase a bit, but ISS will have to be reboosted or it'll fall out of orbit. The Space Island group wanted to build a space hotel from ETs using small solid rocket motors strapped to the ET to lift it into orbit. When it's discarded it's most of the way to orbit, the OMS-1 manoeuvre gives the orbiter a little nudge into the final trajectory to apogee, then the OMS-2 burn circularizes the orbit. Doing the same thing as OMS-1 and OMS-2 burns in a controlled manner with solid rockets is difficult.
Furthermore the insulation foam on the ET isn't designed to endure, just last long enough to get into space. Pieces of foam break off during launch, now imagine temperature cycling from -120°C in shade to +150°C in sunlight, intense UV light (degrades plastics), and micrometeoroids as small as a grain of sand striking at 20 times the speed of a bullet. ET foam would have to be replaced by a more durable thermal and micrometeoroid protection layer. That means redesign and would probably add weight. A slight weight increase over something as large as the ET would significantly reduce cargo capacity. Space hotel guys really need a purpose-built self-launching vehicle. That would be a large sustainer stage with strap-on boosters, where the intended cargo is the sustainer stage itself and that has the durable thermal and micrometeoroid protection layer. A purpose built vehicle would also have built-in pressure hatches, windows, mounting points for equipment, etc. You wouldn't want any loose stuff inside the tank during launch, and I don't know how much cargo such a vehicle could lift, but you could get a good size hull up quite effectively. Cargo ships like Progress or ATV could lift equipment loads. But I don't see how you could do it with a Shuttle ET.
::Edit:: One option is a Delta IV CCB modified with said thermal and micrometeoroid layer, pressure doors and windows. Add 2 GEM 60 solid rockets (like Delta IV Medium) but remove the upper stage and cargo. Would it need an OMS or could it insert into orbit as-is? The result would be a 5.1 metre diameter, 40.8 metre long pressure hull. As a comparison Zvezda, the Russian Service Module also know as the Mir 2 Core Module, is 4.2 metre diameter at its widest point and 13.1 metres long. Zarya is 4.1 metre diameter and 12.6 metres long. Unity (node 1) is 5.5 metre diameter and 4.6 metres long. Destiny is 28 feet long, 14 foot diameter. So this one Delta IV module would have more interior volume than all of ISS as currently in orbit. Delta IV Medium+ (4,2) includes 2 SRBs, the upper stage, and a 4 metre fairing for $95 million in 1999 dollars.
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"Higher than an axial configuration that completely changes acceleration load stress, thrust stress, and aerodynamic loads?
Why yes it would change them: it would improve them.
Higher development cost that re-engineering the external tank?"
Yes. The external tank is a pretty low-tech piece of equipment, and its structure was alterd without large expense or fanfare when NASA switched from Aluminum to Lithium alloy. Changing the the LOX tank, considering its already complex shape, should not be anywhere near the challenge of building a brand new large-diameter automated reentry & landing vehicle.
"Higher cost than rebuilding all 3 MLPs to move the exhaust hole?"
Yep. Tens of millions of dollars spent testing the heat shield on your pod, or just cutting bigger holes in the launch tables and moving the hold down clamps... You don't exactly need a rocket scientist for that, but you do for the pod.
"I still think cost control is more effective to design an engine pod that requires minimum labour to process so it can launch in less than 2 weeks. All those guys who designed vehicles for the X-prize were able to do it, Burt Rutan's vehicle SpaceShipOne..."
Please, invoking Burt and his toy rubber rocket plastic Cessna? Burt (and the other X-Prizers') aren't even close to this level of engineering, they are amateurs, and citing them about a rocket where a single shot could involve >$2Bn is a silly comparison.
No, I don't think a two-week turn around for the pod is practical. It could take several days on orbit to pass over the desired landing site, another two or three days to get the pod back to KSC or MSFC, which leaves you with little time to get it ready and back to the VAB.
"requires minimum labour"
Is not how I would describe the reprocessing procedures for SSME engines, refueling the OMS pods, and so on.
[i]"The power of accurate observation is often called cynicism by those that do not have it." - George Bernard Shaw[/i]
[i]The glass is at 50% of capacity[/i]
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This discussion may be http://www.spaceref.com/news/viewnews.html?id=1040]moot.
Give someone a sufficient [b][i]why[/i][/b] and they can endure just about any [b][i]how[/i][/b]
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The larger vehicle looks like Ares, except with inline SSME's instead of the side mounted ones. They don't say how much the larger lift vehicle should be able to launch though. Ares was supposedly capable of putting 121 tons into 300 km orbit, boost 49 tons to the moon, and send 47 tons to mars.
They are saying 240 thousand pounds with 4 SSME's! And the SRB derived rocket will lift 55 to 65 thousand pounds.
http://www.safesimplesoon.com/charts-lg … eliability
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...Which adds up to 108MT. A little lower then the 120MT figure isn't it? I wonder which upper stage engine it uses... the J-2S engine proposed for "The Stick" upper stage probobly lacks Isp and thrust for such big payloads... stick a 5th SSME under it instead.
I'm glad that Griffin & Co seem determined to do best thing for the long haul (especially Mars) and not burn billions on a blind rush for the cheapest/easiest option. Inline all the way, Mike.
Reading the tail end of Bill's link, I am getting worried that Congress might kick the legs out from under VSE...
-Keep Shuttle flying until CEV is available?
-Forbid Griffin from cutting ISS science to fund VSE?
-Forbid Griffin from culling the Shuttle Army?
...I think its time that we had a very, very public counter, to have Griffin personally explain the cold, hard facts of the situation to Congress, that there is not enough money to do all these things, and they just have to be done. Or better yet, have Mr. Bush say so, and tell the "mmmm pork!" congresscritters to suck it up and get with the program.
[i]"The power of accurate observation is often called cynicism by those that do not have it." - George Bernard Shaw[/i]
[i]The glass is at 50% of capacity[/i]
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Interesting: the Safe-Simple-Soon web site lists today: Shuttle-C, tomorrow: an expanded version with 5-segment SRBs and stretch ET, future: inline SDV with 5-segment SRBs, 4 SSMEs, and J-2S/SSME upper stage. Why do they list both engines? Are they unsure which to use or are they talking about 2 upper stages? They do that with "The Stick" as well. This is pretty much what I've been saying; start with something that can be done quickly with low development cost and has an expansion path. Obviously I would prefer Shuttle-C to use a recoverable engine pod and the large version with expendable engines to use RS-68 engines. If they really want to use inline engines for the large version, well fine; just leave at least one MLP configured for the smaller Shuttle-C.
But are they really serious about "The Stick"? Oh please say it isn't so. I thought Challenger proved a solid rocket isn't safe for human travel. We've been limping along with an unsafe Shuttle because it's the only game in town, but they want to continue? Obviously I would prefer the mini-HL-20 space taxi but even an EELV would be safer than "The Stick".
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Time for a rally?
This is potentially the best news re: spaceflight in decades!
Write your congeressmen, all ye Americans!
(Hey, even a European like me is enthousiastic)
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"has an expansion path"
But its NOT an expansion path, the development for both vehicles would be completly different for everything except the avionics, and you couldn't convey it from one design to the next. I imagine Thiokol is just hoping that NASA would want to develop both vehicles along the way.
The RS-68 would be preferable for cost, but they do suffer a substantially lower specific impulse, particularly at low altitude. Developing a regenerative nozzle version would probobly be harder (since its more complex) compared to a simplified SSME (dumbing down), and each unit would probobly have similar cost. Combine that with Griffin's desire to retain SSME personell, and ~$20M extra a flight probobly isn't a big deal to him if it helps keep Congress off his back and maximizes payload (Griffin likes them big...).
"proved a solid rocket isn't safe for human travel"
Not but a few weeks ago, I thought this too, until I read the Q&A section of the glossy... if the Thiokol brochure is telling it like it is, then I would actually prefer a big solid rocket to a liquid one.
My change of heart has really hinged on these points:
-Modern solid rockets don't fail catastrophicly: being the fuel is made of rubber the fuel grain doesn't crack much, and so the chance of radical overpressure is pretty much nil.
-If there was a breach in the (quite sturdy) outter casing, causing hot gasses to escape (ala Challenger), thats going to be a pretty graceful failure. It gets better: the fuel the SRB burns doesn't work effectively at low chaimber pressure, so a leak (accidental or intentional) would actually partially shut the booster off. That would certainly make escape rather easy.
-Reliability... that the SRB is really, really reliable. One failure out of over 200 flights, and that was because it was used out of spec. It is probobly the most reliable rocket of its size ever concieved by man. Furthermore, if the Thiokol glossy can be believed, that when big liquid engines fail there is a 20-30% chance of catastrophic (read: ignites fuel tanks) failure.
-They also included a "metric" for non-rocket-scientists, which basically shows that the lower acceleration of EELVs means that they will take a long time before nearing orbital velocity, which makes aborting dangerous (very high altitude seperation, hypersonic flip, far Atlantic ocean abort).
...plus if Bill's estimate about SRB cost are anywhere close to correct ($30M a pop for the five-segment), then it would be concieveable to talk about well under $100M each (maybe as low as ~$75M), not counting CEV reprocessing and service module. Hard to beat.
Edit: Oh! And if the upper is powerd by a single J-2S engine, that would certainly be better then 2-3 RL-60 engines for EELV.
[i]"The power of accurate observation is often called cynicism by those that do not have it." - George Bernard Shaw[/i]
[i]The glass is at 50% of capacity[/i]
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Been reading their glossy, too, and it looks like a good, safe design.
A lot of peole think about the SRB-caused explosion of Challenger, but it was *not* the SRB that exploded, no, that one was fine, only a 'minor' sideways leak (sorry, tired, bad english) it was that huuge ET that blew. (because of the SRB, ok, but that's not the point)
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I wouldn't call a burn-through of the O-ring seal "minor". And it wasn't the only time; film of the previous launch of Atlantis showed the same burn-through. Atlantis was lucky, the flame happened to point away from the liquid hydrogen tank. When SRB pressure dropped due to fuel running out, the leak sealed itself. Like I said, trying to contain solid rocket fuel with a rubber O-ring next to a liquid hydrogen tank is very, very dangerous. Yea, the failure was caused when Challenger launched when it was too cold and engineers said so in a written memo, but sound engineering would get rid of it. Single-piece solid rockets of Delta IV and Atlas V don't have those seals so don't have that problem. At least "The Stick" doesn't put a liquid hydrogen tank beside SRB segment seals.
The other issue is that solid rockets can't be throttled or shut off. The high thrust may sound good in the Thiokol brochure, but that same high acceleration means you can't simply use a solid rocket escape tower. The main rocket is a bigger solid rocket, try out running it! The Shuttle really has no abort option after lift-off until the solids are spent, and "The Stick" won't either. Solid rockets of the EELVs are small enough that an escape tower could work.
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"I wouldn't call a burn-through of the O-ring seal "minor""
Really? If Atlantis survived it, then escaping should not be a problem. SRB breach is pretty graceful it seems to me, and Thiokol agrees. And remember, that the combustion reduces if there is a leak and pressure loss. Oh, and if liquid fueled EELVs have a ~99% engine reliability (or chance of engine out), then there is a 1/400-1/300 chance of catastrophic failure for every flight (given a 25-30% per failure), and getting RS-68, RD-180, and RL-60/ML-60 up to a higher reliability may be a tall order. SRB is already there most likly.
And you probobly could shut the thing off with a pretty high degree of reliability: have pop-off vents on the sides of the booster with explosives. The reduced pressure would pretty much extinguish the engine. Probobly not ideal, but practical.
Escape from the SRB wouldn't be a big problem, "The Stick" would put the crew under about 5Gs of acceleration (about as much as the Saturn-V at peak), which is not too bad. Escape motors would need probobly about 3-4Gs extra, for a total of 8-9Gs... Which is about as bad or a bit better then a fighter jet ejection seat, except it would be perpandicular to your aorta and spine, so it shouldn't be a problem. The Stick very well will have escape options.
Plus, since the acceleration is higher, then escape ought to be actually safer, since after you do seperate you are probobly in better shape (see last post).
I think that SRB launcher would be safer then the EELV launcher would. Gentler failure modes, lack of catastrophic failure modes, higher overall reliability (only one actual failure?), better position following abort seperation, and so on.
I think its safer then the EELV option actually
[i]"The power of accurate observation is often called cynicism by those that do not have it." - George Bernard Shaw[/i]
[i]The glass is at 50% of capacity[/i]
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I read somewhere (I forget where - space.com maybe) that the SRB for CEV will include a line of explosive charges running down the exterior walls of the SRB.
In the event of abort, these charges tear open the casing from nose to nozzle which terminates the upwards thrust of the SRB. Then, as the CEV escape tower is firing there is no longer an out of control SRB chasing it. This might also kick sideways the remnants of the SRB, away from the CEV.
Give someone a sufficient [b][i]why[/i][/b] and they can endure just about any [b][i]how[/i][/b]
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It wouldn't have to rip the whole thing in half most likely, just puncture it.
[i]"The power of accurate observation is often called cynicism by those that do not have it." - George Bernard Shaw[/i]
[i]The glass is at 50% of capacity[/i]
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