Might Shuttle C - save Hubble?

GCNRevenger · 2004-07-21 09:59:34

Adaptive optics don't correct for atmospheric absortion, only atmospheric scattering/bending of light. Telescopes on the ground recieve less light per-aperature than Hubble does because of absortion, but it is simply more economical to build a bigger mirror on the ground.

RobS · 2004-07-21 11:21:35

GCN Revenger, you're talking about spending 10-15 billion to build a SDV. That's equivalent to 70 to 100 EELV launches at $150 million each.

I'm talking about a system that cuts the number of EELV launches needed about in half. If you want to put 25 tonnes on Mars, one EELV launches the 25 tonne payload; another launches the aerobrake, lander engine, lander fuel, parachutes, and xenon propellant.

The solar tug would mass about 8-12 tonnes (I've seen different estimates), would already be in earth orbit, and would be reusable (ion engines and solar panels last a long time).

You have to perform an automated docking of the cargo to the aerobrake/lander, and another automated docking of the combination to the solar ion tug. This requires some technological development, but is doable. The Russians do this all the time.

The tug pushes both to L1, where it detaches and returns to low earth orbit. This it can do quickly because the ion engines are pushing only 8-12 tonnes. It never goes to Mars. (Of course, you could use the solar ion tug to send the payload to Mars, but that will take about a year, and the tug would then have to loop fly by Mars and return to earth over another year or so).

At L1, the Mars cargo vessel would dock to a "Lifter" vehicle that flew up from the lunar surface with hydrogen and oxygen fuel. The "Lifter" would leave the moon with about 16 tonnes of LOX/LH2, arriving at L1 with 9 tonnes. The Lifter would dock to the cargo vehicle, perform a small delta v (about 200 m/sec) to loop it around the moon and back to Earth, then give it a delta v of about 0.7 km/sec to send it on a Hohmann trajectory to Mars. The Lifter would then slow itself down and return to L1 or straight to the moon (it's have about a tonne of fuel left after trans-Mars injection and masses about 2 tonnes empty).

The Mars cargo vehicle would do its own midcourse corrections, aerobrake, and land on the surface, the way Spirit and Opportunity do now.

Costs: say $1 billion to develop the tug (estimates I have seen are $500 million, but lets be generous); two $150 million EELVs; some millions in xenon (or maybe argon, if it can be used instead).

Yes, you have to go to the moon first; but the Bush plan requires that, and the Bush speech spoke of using lunar resources. Near as I can tell, that's a reference to lunar water. The lunar orbiter and landers will be geared to the question of whether the water is there and whether it can be used. The lunar lander mission that was just approved as a semifinalist for consideration for launch in 2009 has as its principal investigator Michael Duke. Duke's the guy who proposed the solar electric vehicle as a main element in a lunar transportatin system in 1997 (whose article I talk about ad nausam). He's at Colorado School of Mines and collaborated in a study of the uses of lunar water in low earth orbit; he has been working at CSM on the design of a rover to scoop up icy regolith.

So there's momentum behind the idea to use lunar water and momentum behind the idea of using it to launch things to Mars. It was the NExT (NASA Exploration Team) that proposed a station called "Gateway" at L1 for moon and Mars transportation. Duke knows the NExT folks. They've also proposed a solar ion tug (there's a design for it on the web). Zubrin says the NExT team has a good track record of predicting where NASA is going.

Back to the 25-tonne cargo landed on Mars. According to Mars Direct, it requires 140 tonnes in LEO using chemical propulsion. That's one or two SDV launches at about $1 billion each. Why spend $10-15 billion to develop an SDV and at least $1 billion to launch each when one can spend $1 billion on a tug and maybe $300 million on each launch? It doesn't make sense.

Furthermore, there's this thought: in the next twenty years we may very well see commercial ventures develop a way to launch stuff into LEO for much less per pound than SDV or EELV. But if that happens, the payloads will be small; perhaps ten tonnes. We'd go crazy trying to fly to Mars with ten tonnes of cryogenic fuel launched each time. A solar ion tug would facilitate use of ten tonne payloads.

-- RobS

SpaceNut · 2004-07-22 11:47:56

The biggest problem with Hubble is not the repair but is when. The actual reason that anything is being done in the first place is that it will come down on our little heads if nothing is done.
With Nasa's budget constantly being stripped or lowered it makes it very hard to do anything but to maintain those programs that are already in the pipe line.
Hubble is definitely worth saving but there must be a limit to the cost. Also Nasa must always design into any probe that circles where ever. The ability for a clean deorbit if it wishes to have safety, or no contamination to the environments that these probes circle to not be impacted.

BWhite · 2004-07-22 11:59:58

RobS - - the biggest problem I have with using luanr water for rocket fuel is economic.

As launch costs fall, the value of lunar water falls in exact proportion. Today, Zenit-2 can lift to LEO for about $1,000 per pound. Dip a bucket in Lake Michigan and stick on a Zenit-2 and you have water in LEO for $1000 per pound.

If launch costs fall, that number falls in a similar fashion.

I cannot imagine how we can possible mine lunar water and ship to LEO at a cost of $1000 or less anytime soon.

LaGrange? Shipping lunar water to a LaGrange point is better yet which is cheaper? One robust nuclear thermal tug able to push cargo pods from LEO to a LaGrange point or a lunar mining operation?

Build the lunar water facility and watch as the Russians, Chinese or French deploy a nucelar thermal tug and undercut your price per pound for LaGrange rocket fuel delivery.

SpaceNut · 2004-07-22 12:26:26

Maybe it is time to think of non oxygen oxidizer fuels source. Such as the story that ran last month on fuels for Mars which used magnesuim oxide rich soil and carbon dioxide with an iodione catylst.

GCNRevenger · 2004-07-22 13:16:16

I don't think that the SDV will be such an expensive project, if NASA has a change of heart and finally decides to put its continued exsistence ahead of prolonged Shuttle engineer employment... Building the EELVs, new main engines, new structure/tanks, almost new everything costs only a few billion. Also, if NASA is able to shed a large portion of the Shuttle workforce, I don't think it at all unrealistic to talk about <$500M per flight for a 100MT to orbit.

The HLV version of the EELV by the way, costs in the region of $200-250M, not $100-150M roughly. The Atlas-V might be a few bucks cheaper, but it holds a little less mass as well. Speaking of EELV, it is not at all unreasonable to upgrade them beyond their current performance: the engines of both Delta-IV and Atlas-V HLV have plenty of thrust for more payload, it is simply a matter of larger fuel tanks. Such an upgrade would not be terribly costly, and could reach payloads of 40MT without radical alteration to the vehicle concepts... So 40MT for $300M doesn't sound too bad to me if SDV is not available to fly often.

Harvesting of Lunar water as rocket fuel and the use of ion drives to reduce the fuel needed for TMI or Lunar landing is a great idea... on paper. You will still have to harvest many tons of water (time, energy to remove from soil by heating), electrolyze that water (HUGE energy cost), then liquify the resulting gasses (big energy cost), store them without substantial boiloff (big energy cost again), load them onto a fairly large surface-L1/TMI launch vehicle... which has to be reuseable, and able to land within feet of target with reliability many times... and you have to burn substantial fuel to get the lander back down (maybe more than 1MT)... This all has to work for years with minimum human intervention, without breaking the bank, many many times to make it worthwhile.

Or, you can trade up that EELV for EELV+ and bring the fuel you would otherwise mine from the Moon (or at least the heavy LOX) and just run your solar ion tug between LEO and L1... EELV+ with 40MT capacity, launching a 20-25MT payload... 2MT launch faring doubling as aerobrake shield NASA-DRM style, a small cryogenic TMI stage with 7MT of fuel leaves you with about 5-10MT for the lander section and margins... less on-orbit docking/assembly involved, no mass penalty for the Moon/L1/TMI shuttle, and only one EELV+ flight per 20-25MT mission. Though the tug would have to cope with fuel boiloff from the payload TMI stage, and it would have to be refueled from a seperate flight probobly on occasion... set up a one-launch Xenon fuel depot, storing it as a gas at low temperatures, and have the Xenon tug use its Hydrogen condenser to refuel its own tanks between missions.

No Moon involved... for an extra $100-150M a shot

And about SDV, you can send about 40MT to Mars using a ~120MT launch vehicle equipped with cryogenic engines, or 60MT using NTR engines, none of this 140MT launcher for 20-25MT stuff... Now about that big rocket... say it does cost wind up costing about $500M a flight as it could with proper management. Thats not a bad deal compared EELV+ either since you don't need a tug, double the payload (which is good, since you don't have to devide up the payload and package separatly) for about $150-200M compared to the EELV+ & Tug scheme.

Hauling Lunar water sounds great, and ion-powerd tugs to L1 sound great, but it just cannot compete with simply building a bigger rocket when you aren't launching many, many payloads often.

PS: Oh! I forget to spell it out, but an EELV+ able to haul an aerobrake shield, TMI stage, and Martian lander would only take one flight rather than two regular EELV-HLVs.

SpaceNut · 2004-07-23 07:03:04

Besides using lunar mined water, we must think outside of the box in ways to save this precious comodity. Launching vehicles by other means from the lunar surface is a must. Ideas such as the space elevator and magnetic pulsed rail gun system that are solar powered are a few that come to mind.

GCNRevenger · 2004-07-23 07:13:12

No, we need to figure out how to get signifigant (20MT) masses to Mars with a minimum of cost, risk, and effort. Eliminating Lunar water entirely by increasing the size of the Earth's rocket fuel tanks eliminates the whole trouble of Lunar water mining in the first place. Using a larger launch vehicle, which by virtue is more efficent than a smaller one with its bigger volume per surface area and little/no need for orbital docking is even better if you don't need to launch often.

BWhite · 2004-07-23 09:09:03

No, we need to figure out how to get signifigant (20MT) masses to Mars with a minimum of cost, risk, and effort. Eliminating Lunar water entirely by increasing the size of the Earth's rocket fuel tanks eliminates the whole trouble of Lunar water mining in the first place. Using a larger launch vehicle, which by virtue is more efficent than a smaller one with its bigger volume per surface area and little/no need for orbital docking is even better if you don't need to launch often.

Since bigger rockets means better mass fractions (more fuel with less structure) how did the alt-space hype start to begin with?

I suppose reuseable systems are helpful, but isn't the ideal booster one that would use the least residual mass that did not end up either:

(a) combusted for thrust; or

(b) placed in LEO as payload?

SpaceNut · 2004-07-23 09:35:45

Changing the height to diameter of a stage such that you increase the diameter and decrease the over height would this not be better for reducing the mass of a given stage.

GCNRevenger · 2004-07-23 13:12:15

The mass fractions for small-to-intermediate sized rockets that the AltSpace people can afford to build are good enough for satelite launches... they simply can't afford to develop a larger rocket.

As for the ideal expendable booster yeah, but there is a limit to how big is useful and expedient.

RobS · 2004-07-23 21:44:05

Regarding some of the questions about solar-ion tugs and lunar water. . . .

There is a very detailed economic study about lunar water available at

http://www.mines.edu/research/srr/Refer … ...ted.pdf

The title is "Space Resource Economic Analysis Toolkit: The Case for Commercial Lunar Ice Mining" by Brad B. Blair, Javier Diaz, Michael B. Duke, Elizabeth Lamassoure, Robert Easter, Mark Oderman, and Marc Vaucher. It's a very thorough piece of research and analysis and is accompanied by a detailed business plan. You might want to look it over.

The summary is as follows: with government subsidy to build some of the equipment, if lunar water were used to launch all geosynchronous satellites from LEO to their final destination (which isn't very many; 3 per year initially), the operation could make a profit. The study also shows, however, that the conclusion is immensely sensitive to the assumptions and that the effort could break even or lose billions. They did a thorough and honest job in the cost analysis.

I mention this publication to show that a lot of thought has gone into the problem, and with the likelihood of ice at the poles (they assumed using regolith with only 1% ice in it) we can be sure there will be a lot more thinking done.

If one assumes the development of solar ion tugs, the commercial basis for using lunar water in LEO is destroyed; the demand would be insufficient. Indeed, if one were to develop a solar ion tug to haul satellites from LEO to GEO, one might undermine the entire commercial launch industry, because that would cut the number of launches per year about in half.

The picture changes greatly, however, if one assumes manned missions to the moon and Mars, because that increases the number of launches to LEO, justifying the current EELV launch infrastructure AND a solar ion tug. It may change the situation for the profitability of lunar water as well. Blair et al make no assumptions for the use of water in manned space flight. And note I only assume the use of lunar water from Lagrange 1 to Mars. Getting water from the moon to L1 is cheaper than getting it all the way to LEO.

Yes, this will require reusable vehicles able to land within meters of a destination on the moon and a lot of energy for electrolysis and refrigeration. We'll need the latter for Mars Direct anyway. And without an atmosphere to deflect a landing space vehicle, especially if it's following landing beacons, there's no reason to assume it won't be able to land within a few meters of its destination (like smart bombs hitting chimneys). Most stages that can be reignited in space for a second burn are designed so they could be reignited several other times. The Blair et al publication assumes a dozen reuses. Considering the vehicles will be battling weak lunar gravity and won't have atmospheric buffeting or corrosion to deal with, this strikes me as withing the realm of possibility.

As for "Russians, Chinese or French deploy[ing] a nuclear thermal tug and undercut[ing] your price per pound for LaGrange rocket fuel delivery" dream on. The French (or the Europeans in general) don't have the political will to develop nuclear power in space. The Russians don't have the money. And the Chinese won't spend that kind of money for some time.

As for larger versions of EELVs, I'm all in favor of them! I'd prefer 40 tonnes to LEO. But even then, you'd need three launches to send 25 tonnes of usable stuff to Mars (I don't think two is correct). Even without lunar water, a solar ion tug would reduce that to two, saving $300 million (whatever the launch cost of the EELV+ would be) each time. That adds up fast, especially if it's used for lunar cargo as well as Martian (which it would be).

-- RobS

GCNRevenger · 2004-07-25 12:38:24

Mmmmmm it might be some day, but I don't know if there will be enough launches to justify the large expense of a lunar fuel operation... it really will be alot of trouble. The little Prometheous class reactors, which will probobly be modified and used on early to near term Mars missions, might not be enough to operate a tens-of-tons fuel factory and storage facility on the Moon. And the launch vehicle comparison with smart bombs misses the fact that the launch vehicle has to go much, much, much faster so it becomes a matter of resolution of the flight control... $$$

I think that two 40MT launches could send about 20MT to Mars... you can send about 1/3rd of the mass to Mars as you can to LEO (MarsDirect Ares lifts 120MT or 40MT to TMI), so you launch the TMI rocket and LOX in launch one, then the 20MT payload + 5MT lander + 1-2MT aerobrake plus the Hydrogen in launch two. The lander performs maneuvers and docks with the LOX/TMI stage and then burns to head to Mars. Two launches, $500-600M, no ion tug or lunar fuel needed.

Or with a ion tug to Lagrange as in earlier posts, carry a small TMI stage to Lagrange with the 20MT payload and 5MT lander in only one EELV+ launch and go from there.

ANTIcarrot. · 2004-07-25 17:59:05

As for "Russians, Chinese or French deploy[ing] a nuclear thermal tug and undercut[ing] your price per pound for LaGrange rocket fuel delivery" dream on. The French (or the Europeans in general) don't have the political will to develop nuclear power in space. The Russians don't have the money. And the Chinese won't spend that kind of money for some time.

The chinese are more likely to use zond style capsules and send a couple of people on an Apollo 8 style trip round the moon. Something they could easily manage a few years from now. Rondavouzing a Zond and 1 or 2 soyuz size booster-stages should be well within their capacity by then. Ditto for russian docking technology.

In fact, secretly helping them do just that might be one of the smartest things NASA could at the moment.

ANTIcarrot.

RobS · 2004-07-25 23:08:58

I agree that the economics of lunar water recovery will be dicey for some time. That's what the report I cite says as well.

By the way, in terms of power, Michael Duke's "Lunar Reference Strategy" presentation in 1998 estimated that a 1-tonne, 25-kw solar or nuclear power system could produce 32 tonnes of hydrogen-oxygen fuel per year. He later told me in an email that the estimate was low and that 25 kw could make more. It appears the report I cited thinks 25 kw can make well over 100 tonnes per year, but they don't state a number clearly anywhere.

So a Prometheus or Mars-sized reactor would work.

-- RobS

SpaceNut · 2004-07-26 07:45:39

Problem is that Nasa just does not have the budget for the Prometheus size reactor and may not get it back until later years. I think different chemical fueled engines are what will aid in lunar launches.
Martian Jet Engine Burns Carbon Dioxide or other non water based fuels.
http://www.space-rockets.com/marsjet.html

GCNRevenger · 2004-07-26 08:21:16

Okay SpaceNut, how will this help us get off the Earth and into orbit? Dr. Zubrin's MarsDirect plan has already cut a feasable Mars mission down to just two launches of a superheavy lifter or 6-8 medium/heavy lifter.

SpaceNut · 2004-07-26 08:32:51

These would only help on lunar or mars return flights for saving of water mined fuels not meant for Earth to orbit use.
Water has a higher priority for the colonist or for Base functions than for fuels.

GCNRevenger · 2004-07-26 08:49:57

Yeah which is good and all, and is how MarsDirect works (sort of), but that isn't so much the problem... the problem is getting stuff to the Moon and Mars from Earth without breaking the bank or making the project drag on forever.

SpaceNut · 2004-07-26 09:02:18

All the more reason to start making things aboard the ISS, including recycling of what some would earmark as garbage(plastics,foils ect..).

The needed skills to do so in a near zero gravity environment is a must. Also developing the needed smelting furnaces, mining equipment and other tools that work off from alternative power sources is also a must.

GCNRevenger · 2004-07-26 10:58:08

But the ISS does none of these things, nor can it. In fact, the biggest problem with getting to Moon/Mars is simply getting the fuel into orbit, which is much of the mass of the spacecraft. The answer is not to piece together endless numbers of tiny payloads or tiny fuel loads at a space station, this has proven to be horribly expensive no matter how much "experience" we have... we should instead simply build larger rockets, and connect together fewer larger pieces by remote docking.

SpaceNut · 2004-07-26 12:25:46

The only problem is that this same issue will still be in place at any lunar or Mars base of the future. We must learn how to do things without relying on the Earth as much once we are there.

GCNRevenger · 2004-07-26 12:49:39

Although that is true, its much easier from a technology standpoint to get off of the Moon or Mars, since they both have far less gravity and a much less atmosphere in the way. LOX/LH or even lower Isp systems would have enough efficency to do the job... the problem is on the Earth end, that we have more gravity and thicker air to fight to get into space, even with the very best of chemical fuels in our rocket engines.

SpaceNut · 2004-07-26 12:56:12

So why did we move from the first stage saturn rocket engine use of LOX and Kerosene, to Hydrogen and Lox for the Shuttle. Is it safer to use or more environmentally friendly.

GCNRevenger · 2004-07-26 13:34:27

There are a couple of reasons, mainly where the engine is supposed to be used.

Early in the flight it is more important to pick up speed quickly then it is to save every gram of fuel, otherwise it takes too long to defeat gravity and has to push against the thicker air at lower altitudes. So, a high-thrust engine like the Saturn's F-1 or the Shuttle SRB is preferred to a lower thrust one operating more efficently.

The Space Shuttle uses its main engines to give the last extra nudge needed to get off the ground using the big SRBs on the sides, but where they really shine is at high altitudes and speeds - where the SRBs are spent and ejected - and is able to achieve orbital velocity for a minimum of mass.

The Saturn rockets all used hydrogen fuel for their 2nd and 3rd stages because it is so light weight for the amount of power you get... most modern American rockets use it for the 2nd stage too.

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#51 2004-07-21 09:59:34

Re: Might Shuttle C - save Hubble?

#52 2004-07-21 11:21:35

Re: Might Shuttle C - save Hubble?

#53 2004-07-22 11:47:56

Re: Might Shuttle C - save Hubble?

#54 2004-07-22 11:59:58

Re: Might Shuttle C - save Hubble?

#55 2004-07-22 12:26:26

Re: Might Shuttle C - save Hubble?

#56 2004-07-22 13:16:16

Re: Might Shuttle C - save Hubble?

#57 2004-07-23 07:03:04

Re: Might Shuttle C - save Hubble?

#58 2004-07-23 07:13:12

Re: Might Shuttle C - save Hubble?

#59 2004-07-23 09:09:03

Re: Might Shuttle C - save Hubble?

#60 2004-07-23 09:35:45

Re: Might Shuttle C - save Hubble?

#61 2004-07-23 13:12:15

Re: Might Shuttle C - save Hubble?

#62 2004-07-23 21:44:05

Re: Might Shuttle C - save Hubble?

#63 2004-07-25 12:38:24

Re: Might Shuttle C - save Hubble?

#64 2004-07-25 17:59:05

Re: Might Shuttle C - save Hubble?

#65 2004-07-25 23:08:58

Re: Might Shuttle C - save Hubble?

#66 2004-07-26 07:45:39

Re: Might Shuttle C - save Hubble?

#67 2004-07-26 08:21:16

Re: Might Shuttle C - save Hubble?

#68 2004-07-26 08:32:51

Re: Might Shuttle C - save Hubble?

#69 2004-07-26 08:49:57

Re: Might Shuttle C - save Hubble?

#70 2004-07-26 09:02:18

Re: Might Shuttle C - save Hubble?

#71 2004-07-26 10:58:08

Re: Might Shuttle C - save Hubble?

#72 2004-07-26 12:25:46

Re: Might Shuttle C - save Hubble?

#73 2004-07-26 12:49:39

Re: Might Shuttle C - save Hubble?

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Re: Might Shuttle C - save Hubble?

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Re: Might Shuttle C - save Hubble?

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