Use of Shuttle External Tank in orbit

[qso1]

The OMS engines give the orbiter the delta V to reach orbit. Unless the profile has been changed in the last few years. The data I had indicated 16,500 mph for ET sep.<br /><br />At 17,250 mph, your just short of orbit. In either case, the orbit would not be a long enough lasting one to allow missions to outfit the tank on the timescales NASA is used to. The tank would require an OMS like pod or some type of rocket to get it to a stable orbit in much the same way the OMS does so for shuttle. I realize your far more knowledgeable of the space stuff than I so just bear with me if you can. <div class="Discussion_UserSignature"> <p><strong>My borrowed quote for the time being:</strong></p><p><em>There are three kinds of people in life. Those who make it happen, those who watch it happen...and those who do not know what happened.</em></p> </div>

 

[qso1]

Your graphics are very nicely done.<br /><br />Your proposed use of ETs in a manner similar to transportation containers etc. should definetely bring down the cost of getting to orbit. I guess now or the near future is the time for someone to finally be able to demonstrate it. <div class="Discussion_UserSignature"> <p><strong>My borrowed quote for the time being:</strong></p><p><em>There are three kinds of people in life. Those who make it happen, those who watch it happen...and those who do not know what happened.</em></p> </div>

 

[mlorrey]

Well, I think that this is where folks on this board can come in handy: I proposed this constellation as an alternative to the Thiokol VSA/ESAS proposals, as something NASA should be doing. If you agree, I'd encourage people here to spread the word around and start emailing your congressmen and senators that there is an alternative plan that makes more sense and winds up with much more infrastructure in space. Send emails to Mike Griffin too. The base model with the capsule in my graphic was similar to something that was considered by NASA as an alternative to The Stick, but was abandoned because they did not consider the stage and a half option to increase payload in orbit. Dropping all but one engine for each tank assembly when 65-70% of fuel is burned (as was done with the early Atlas) is crucial to get the payload performance from this, while at the same time it gives reusability to the engines.

 

[qso1]

I do agree this approach would be economical if mass produced. Most any proposal would. Problem is NASA which will quote large costs just to do the stick approach. I think the access to space problem needs to be solved by private industry, entrepreneurs while maybe NASA should still do the actual base hardware for lunar Mars.<br /><br />I only say NASA should do lunar Mars unless private industry sees profit potential for doing lunar Mars as that is what would drive them. Part of that profit potential would be achievable if low cost access to space can be realized. <div class="Discussion_UserSignature"> <p><strong>My borrowed quote for the time being:</strong></p><p><em>There are three kinds of people in life. Those who make it happen, those who watch it happen...and those who do not know what happened.</em></p> </div>

 

[tomnackid]

mlorrey,<br /><br />Your still stuck with the same problem. Who is going to pay to keep all those tanks in a stable orbit? As I said before we have been leaving spent upper stages in orbit since the original Atlas. Now launch agencies have to expend delta v to make sure there upper stages WON'T go into orbit so as not to be an orbital debris problem. If we had the ability to use those tanks cost effectively we could have been stock pilling them in orbit since STS-1.<br /><br />Where are all those SSME pods going to land downrange? NASA did consider dropping SSMEs in recoverble pods as far back as the early 80's. I'm not saying these ideas don't have merit, but they also bring problems of their own. IMHO I think we need something like the stick as a first step to give us (fingers crossed) cheaper access to space (cheaper than the shuttle, but more capable than Soyuz at any rate) to build an infrastructure that can make economical use of all those empty tanks.<br /><br />Also with the larger designs you run into the problem of large scale clustering. The Saturn 1 did ok with a cluster of 8 rockets for a first stage, but the N-1 and the Orteg designs ran into problems with large scale clustering. Maybe modern computers could solve the problem (bad programming and slow computers certainly help to sink the N-1) but by the time we need your "F" designs we might be better off with huge, simple, pressure fed engines like the Sea Dragons. Also if you put an entire Sea Dragon second stage into orbit you have a steel hulled space colony, not these namby-pamby NASA aluminum beer cans <img src="/images/icons/wink.gif" />

 

[chriscdc]

The R-7 has 20 first stage main engines and has a success rate of 97.5%.

 

[tomnackid]

But the R-7 is nowhere near as big as mlorrey's ultra-heavy lift designs. And actually the R-7 has 20 thrust chambers but only five engines. 4 strap-ons plus the core for a total of 5 engines with 20 chambers for the first stage. (Not including the verniers.)<br /><br />From the "Russian Aerospace Guide"<br /><br />"Each RD-107 engine consisted of four combustion chambers, fed by a single turbo-pump mounted above the chambers. The chambers were the same basic technology as the German V-2 engine chamber. Each had the same thrust as a V-2 engine, but the chamber pressure was four times higher. The core stage used a RD-108 engine, which was the same as the RD-107, but with four steering verniers. "<br /><br /><br /> I'm not saying its impossible or even undesirable under certain circumstances (for example smaller engines can be dropped as you go and might be worth recovering). But it is an added complexity. Its the same old trade off: development cost (for new, bigger engines) vs. operational costs (the inherent weight penalty and complexity of clustering). Note that the Russians (the masters of rocket clustering) went to great lengths to reduce the number of engines when they developed their Energia HLLV.

 

[tomnackid]

I would like to humbly submit my idea for the most unusual use for a Shuttle ET. The picture (when it shows up) is a self promotion piece for my illustration work (I have used it as a calendar and a greeting card among other things.) It shows how some future comet miners can contrive to have an "old fashioned" Christmas. Comets are "dirty snowballs" after all right? Look closely at what they found lying around to use for the nose.<br /><br />PS: Yes I know, I know, we now know that comet nuclei have dark, carbon covered surfaces that are almost black. Well, I can't let a bunch of boring scientists ruin a clever piece of illustration can I? <img src="/images/icons/wink.gif" /><br /><br />

 

[qso1]

Nice work there, what program did you use to do that? <div class="Discussion_UserSignature"> <p><strong>My borrowed quote for the time being:</strong></p><p><em>There are three kinds of people in life. Those who make it happen, those who watch it happen...and those who do not know what happened.</em></p> </div>

 

[qso1]

Thanks for the input. You'd think at my age I'd finally have some smarts but, what can I say. <div class="Discussion_UserSignature"> <p><strong>My borrowed quote for the time being:</strong></p><p><em>There are three kinds of people in life. Those who make it happen, those who watch it happen...and those who do not know what happened.</em></p> </div>

 

[mlorrey]

Tomnackid, the tanks have RCS installed, as would be needed for the launch vehicle to have roll control, which would be suitable for a few months drifting alone. So that objection is baseless. You may also have noticed I said the first mission would be to put up a docking core, which would lock on the first six tanks to be launched, thus providing enough on orbit capacity for a significant permanent manned presence in space, including the ability to corral more tanks in. Each tank has a docking hatch at the nose and stern, so they can be linked together end to end. This means that the core docking system creates a central kernel from which a complete space station can be built from tanks.<br /><br />The SSME pods will land in the Atlantic ocean, and float with inflatable floatation devices, until picked up by recovery crews. I dare say that recovering one SSME pod should be far easier and cheaper than recovering those big SRBs, so that objection is baseless, too. With the stick you are going to have a recovery crew, AND have problems with the depth divers will need to go to to recover the SRB, in excess of OSHA rules. The SSME pod has no such problems.<br /><br />The N-1 ran into problems being manufactured in a socialist country where a large number of the workers were Gulag prisoners or otherwise underpaid.<br /><br />I agree the F design is a bit big, but the advantages of modularization on economies of scale means that the F design would likely be cheaper than a Sea Dragon, because the same modules are in high production rates for all launchers, rather than custom work on rarely used models. <br /><br />I do forsee the F model primarily being used to loft segments of a true ring space station of sufficient size to produce 1 g artificial gravity. Once we get to that point, I see using the tanks as fish farms, or just shipping them on to the Moon for pre-fab colonist cabins.<br /><br />The other purpose I see in the F model is launching tanks of LH2 into space for nuclear

 

[mlorrey]

The point is that a launcher needs nowhere near as much thrust by the 70% burn point as before, so most of your engine mass is dead weight that detracts from payload capacity. <br /><br />Furthermore, if you look at the reliability, the SSME has flown 342 times, with something like 3 engine failures of various sorts, non catastrophically. The SSME is therefore a far more reliable engine than the N-1's engines, and can thus handle being clustered better. The Russian engine was essentially a massive cluster of V-2 engines, where each engine had 4 V-2 combustion chambers on it (and each V-2 powerhead itself is a massive cluster of smaller heads). So the N-1 isn't a cluster of a few dozen engines, it is a cluster of several hundred engines, most of which share exhaust nozzles.<br /><br />Beyond that, you get aerospike effects from clustering engines that you wouldn't get from building big engines, or rather, the added mass of big engines eliminates the advantages one would gain.

 

[g_sat]

I can follow some of what has been said on this topic, but not all so please excuse my ignorance, but why can't an ET be boosted to ISS's orbit and used as a fuel depot for CEV's and other future vehicles going to the moon and beyond? <div class="Discussion_UserSignature"> </div>

 

[rocketman5000]

The ET doesn't have enough velocity upon release. However I believe that if the only payload was the ET and the shuttle flew empty it might be possible, I didn't run the numbers though.

 

[mlorrey]

If a plasma propulsion system was installed in the intertank space, and fed off residual hydrogen (thousands of lbs available), it could propel the ET to the ISS once the orbiter had put it into a 185 mile orbit or higher.

 

[rocketman5000]

you're thinking a vasimr like device? If so it wouldn't have the thrust to effect the delta V before the ET came back on reentry. That is assuming the ET is a shuttle castoff and not a seperate launch such as you proposed or the SDHLV

 

[mlorrey]

Not VASIMR, a simple arcjet or plasmajet. With a plasmajet, Isp of only 1000-7000 secs, but enough to boost it higher. All it would need would be to have the shuttle leave it in a 185 mile orbit and it could make the rest of the way to the ISS.<br /><br />Lets say we have 3.5 kw of solar panels deploy from the intertank (about what deploys from the propulsion module of the Soyuz).<br /><br />If we were to use plain old arcjets, getting about 550 secs, we'd generate 0.65 Newtons of constant thrust, at a consumption rate of 0.00015 kg/s. Assuming 1000 kg of hydrogen residuals in the tanks, this means 455,000,000 Newton seconds of thrust. <br /><br />Provided that the atmospheric drag at 185 miles altitude (NASA claims a 185 mile orbit is stable) is less than 0.65 Newtons, then the excess thrust above countering drag should, when divided by the 25,000 kg mass of the ET, let you know how many meters/second this system provides to boost the orbit of the ET.<br /><br />Using plasmajets, particularly using diode laser pumped plasmajets, one can get Isp of up to 7000 sec, though this is a new technology and I don't have specific power requirements for high Isp nor what thrust can be produced.<br /><br />However, this sort of system is NOT needed by the launch constellation I have proposed, as this is an entirely different launcher from the STS, it just happens to use the STS external tanks and SSMEs.

 

[mlorrey]

This is one reason I've proposed my launch system. If NASA won't go for it, it might be worthwhile to float as a private venture.<br /><br />To deal with any flaking issues, I have an easy solution: astronauts going out with a large version of those cling-wrap shipping pallate wrappers, attach it at one end of the ET, jet up the MMS pack, and just start orbiting around the ET, wrapping it up.<br /><br />Hey Shuttle_guy, could you dig up some info on the cost of new SSMEs and overhaul costs? Info I have says they are something like $20-40 million a pop.<br /><br />Assuming that 5 SSMEs are mounted to drop pods and recovered by ship, while the sixth is reentered via MOOSE-style reentry foam bag at some point once a permanent manned presence is set up, and able to return via parasail to within a 50 mile radius of a target point, then the primary costs are the incremental engine costs (if it is a 25 flight engine, take the up front cost, divide it by 25, then add a similar incremental overhaul cost), the cost of the ET, fuel, assembly.<br /><br />On the plus side there are no costs related to a huge space shuttle, no TPS maintenance costs, no SRB related costs. <br /><br />Plan on half of the flights including a CEV style capsule, or tSpace CXV, Russian MAKS (minus the RD-701 engines), to add/exchange crews to the station and do assembly work related to the mission and the previous unmanned launch.<br /><br />Half the payload for the manned version (excepting the first launch) can be for-hire, while 3/4 of the unmanned version's payload will be sold to 3rd parties.<br /><br />Per launch engine costs should be about $5 million, ET costs are $750,000 (assuming a contract starting at 10 tanks/yr and going upward from there, I hear Michaud has a surplus of tanks lying around). Fuel costs should be under a million (assuming the brags of $1/lb are true). Need some numbers on CEV/CXV/MAKS costs. Need also to run up a budget to do the assembly mods for the tanks internals so the in-orbit ins

 

[mlorrey]

Gee, you'd think that data would be public information. How is the taxpayer to know what we are paying for?<br /><br />Anyhoo, that's a bit higher than I expected, but not excessively so. Inflation and all...<br /><br />So, figure a Pod will cost $300 million plus thrust structure, fuel lines, parachute recovery (might we use the same system an SRB uses???) and floatation devices. Lets say $350 million (I'm feeling generous), and hope for some quantity breaks from Rocketdyn in the future (if not, screw em and start buying from the Russians or SpaceX's BFR engine). Correct me if I'm wrong, but the new SSME is supposed to be a 10 flights to refurb, 100 flight life engine, correct?<br /><br />If so, then we're talking a per flight amortized cost of the pod at $3.5 million, plus whatever the refurb costs are, so that is still about what I expected. The key to making this work is getting a flight rate high enough that you get ahead of the cost of the money you are investing.<br /><br />On using up the extra tanks at Michaud: yeah, right, I'll meet you there for the firesale next year after Griffin axes the shuttle program. Might be able to pick up some tanks for scrap prices.

 

[mlorrey]

I understand that one reason for this is that the engines are run at 110% each flight. If they operated below 100% all the time, the need for so much inspection and refurb would be much less, true?

 

[rocketman5000]

It could be possible to knock almost all of the foam off the tank once it had become brittle. Leave the tank in an orbit where it wouldn't pose a debris problem. Have vibrators turn on once the foam was adequately broken down at the foams resonate frequency till the tank sheds its foam. Then boost the tank to the appropriate orbit.<br /><br />One drawback would be a high amount of debris in orbit

 

[scottb50]

Think the biggest problem with the ET is its size, it will take a lot more energy to keep such a large, relatively light, object in any orbit than much smaller Modules. <div class="Discussion_UserSignature"> </div>