Heavy Lift an unnecessary impediment?

[GeoDude]

launching things in small packages and assembling in orbit requires a much higher mass to be launched and results in more complicated structures with a multitude of joints. You also don't get the chance to have the completed vehicle tested fully beforehand. It has to be assembled first and then tested. For an example there was a proposal at one point to take the shuttle and use the engines and the cockpit area and convert everything in between to a big living space cylinder. Loose the wings and such in the process. The result would have been more living space then the current ISS with only one launch. The total projected cost was much less then that for a multi-module ISS.
You can make things lighter and more efficient if they aren't split up into a bunch of pieces. On orbit assembly works, but it is costly, takes a long time, and has some inherent risks. For a Mars mission being able to launch a fully assembled and tested vehicle in one shot makes a lot of sense. I would suggest what we need is a vehicle that can launch all of the Mars vehicle as one launch, the Earth departure stage as a second, and when those are docked and ready to go you send the humans up in a smaller craft.

 

[rockett]

launching things in small packages and assembling in orbit requires a much higher mass to be launched and results in more complicated structures with a multitude of joints. You also don't get the chance to have the completed vehicle tested fully beforehand. It has to be assembled first and then tested. For an example there was a proposal at one point to take the shuttle and use the engines and the cockpit area and convert everything in between to a big living space cylinder. Loose the wings and such in the process. The result would have been more living space then the current ISS with only one launch. The total projected cost was much less then that for a multi-module ISS.
You can make things lighter and more efficient if they aren't split up into a bunch of pieces. On orbit assembly works, but it is costly, takes a long time, and has some inherent risks. For a Mars mission being able to launch a fully assembled and tested vehicle in one shot makes a lot of sense. I would suggest what we need is a vehicle that can launch all of the Mars vehicle as one launch, the Earth departure stage as a second, and when those are docked and ready to go you send the humans up in a smaller craft.

That's really a design and engineering issue. While yes, you add some mass and effort in connecting the pieces, you gain flexibility in assembling them. If a replacement is needed, you just replace that part, not the whole spacecraft, engines for instance. Also, the size and configuration is not tied to a single mission. You could swap different pieces for say, a lunar transport vs a Mars mission (which would require a different hab module).

A really big advantage in the modular approach is the size of what you boost to orbit. For a Mars mission, you would need either a whopping big booster, or it would be a very cramped, long, trip (Think sardine can, or Apollo capsule. Not bad for 3 days or a week even, but months or years?)

 

[rcsplinters]

I may be under a misconception but I always thought there was some pretty compelling but simple mathematics behind very heavy lift vehicles. For example, if one has probability of mission success of p, then the probability of success without failure in n missions is 1 - (1-p)^n. In the case of on orbit construction, you need n successful missions to complete and fuel the craft. Assuming that p is equal for lower versus heavy lift vehicles, one definitely wants to keep n as low as possible using this very simplistic model. Heavy lift is key to driving n lower. Interestingly, the Augustine report graphically suggests that as many as 9 - 10 ARES V class lifts will be needed for a manned trip to Mars. This would place n at 9 or 10. At half that lift capacity, then n jumps to 18 - 20, or perhaps even more depending on manifest size (not everything is going "divide evenly" so to speak). Since (1-p) is less than 1, (1-p)^n will diminish rapidly with increaing n, which means 1- (1-p)^n will start to grow. Bottom line is that even with a very good individual flight success expectation, mission success expectation can drop significantly with the number of lifts to LEO. End result, its better to have fewer flights.

As to the comments relating to our sloth until 2015, I see this as being the fatal and dramatic flaw in the administration's plan. The crushing debt which is likely to be present at that time and skill and talent hemorrage that will drain NASA by that will make new program start up very very difficult for a massive program like this. Essentially we'll have to "start over" in many respects. Further, the presumption is that we'll have new, bigger better toys by 2015 (scoff, errr, cough). that also implies that more will have to be manufactured from scratch by industry that has been sitting on its hands for years. We'll have no better chance to build such a craft in 2015 than would China or ESA in 2015. I see this situation as very grim and don't buy gibberish coming out of NASA's leadership or the administration.

When Kennedy pointed this nation at the moon, our response was not to sit on our hands for 5 years. Inaction is not a plan.

 

[sftommy]

Development Costs:
Constellation $10B
New Heavy Lift $5B

Cost of launching a single Atlas V-551 Heavy variant $200M

For the cost of developing and not developing these new rockets we could have put 75 of the big Atlas V payloads in orbit.

 

[rockett]

As to the comments relating to our sloth until 2015, I see this as being the fatal and dramatic flaw in the administration's plan. The crushing debt which is likely to be present at that time and skill and talent hemorrage that will drain NASA by that will make new program start up very very difficult for a massive program like this. Essentially we'll have to "start over" in many respects. Further, the presumption is that we'll have new, bigger better toys by 2015 (scoff, errr, cough). that also implies that more will have to be manufactured from scratch by industry that has been sitting on its hands for years. We'll have no better chance to build such a craft in 2015 than would China or ESA in 2015. I see this situation as very grim and don't buy gibberish coming out of NASA's leadership or the administration.

When Kennedy pointed this nation at the moon, our response was not to sit on our hands for 5 years. Inaction is not a plan.

Have to agree with ya 'splinters. Not getting started until 2015 is silly. Not fielding it until between 2020 and 2030 as Bolden says, is ridiculous. We were to the moon AND back several times in less time than that, with ALL NEW spacecraft. Says to me that the Obama Administration is just stalling until they don't have to deal with it.

 

[rockett]

Development Costs:
Constellation $10B
New Heavy Lift $5B

Cost of launching a single Atlas V-551 Heavy variant $200M

For the cost of developing and not developing these new rockets we could have put 75 of the big Atlas V payloads in orbit.

And between the Atlas and Delta, we could be on our way somewhere at least, LONG before 2015!

 

[NelsonBridwell]

Yes, we need Heavy Lift if we actually want to go anywhere, rather than spending decades and 100s of billions in LEO on attempting to perform manufacturing in space of structures like the ISS. The Ares V can put up 7x the payload of the Shuttle or "heaviest" Atlas V, so it could have assembled an ISS in only a few trips. "Penny wise, pound foolish!"

 

[pathfinder_01]

Yes, we need Heavy Lift if we actually want to go anywhere, rather than spending decades and 100s of billions in LEO on attempting to perform manufacturing in space of structures like the ISS. The Ares V can put up 7x the payload of the Shuttle or "heaviest" Atlas V, so it could have assembled an ISS in only a few trips. "Penny wise, pound foolish!"

The troublle is Heavy lift costs money to develop and what do you do with the heavy life once your station is developed? Ares V would have drained Nasa of the money needed to land stuff on the moon. I think that any Heavy lift should be built in a way that the same workers who do EELV build the heavy lift rocket to. Keeping two lines would be costly.

 

[DarkenedOne]

I may be under a misconception but I always thought there was some pretty compelling but simple mathematics behind very heavy lift vehicles. For example, if one has probability of mission success of p, then the probability of success without failure in n missions is 1 - (1-p)^n. In the case of on orbit construction, you need n successful missions to complete and fuel the craft. Assuming that p is equal for lower versus heavy lift vehicles, one definitely wants to keep n as low as possible using this very simplistic model. Heavy lift is key to driving n lower. Interestingly, the Augustine report graphically suggests that as many as 9 - 10 ARES V class lifts will be needed for a manned trip to Mars. This would place n at 9 or 10. At half that lift capacity, then n jumps to 18 - 20, or perhaps even more depending on manifest size (not everything is going "divide evenly" so to speak). Since (1-p) is less than 1, (1-p)^n will diminish rapidly with increaing n, which means 1- (1-p)^n will start to grow. Bottom line is that even with a very good individual flight success expectation, mission success expectation can drop significantly with the number of lifts to LEO. End result, its better to have fewer flights.

There are a few things you are missing in your analysis.

First of all there are commercial rockets currently available that have a demonstrated high reliability of over 95%. Some such as the Delta II are over 98%. If you choose to develop a new heavy lift system it is not likely that you will be able to achieve such high reliability ratings due to the fact that we have relatively little experience with that large a launch system.

Second of all using smaller rockets is considerable less risky. This fact is because when you do lose a payload the loss is small. NASA was in this situation when they lost the Challenger. The project was delayed but it went on. Nasa simply rebuilt the payload and put it on another rocket. Lets compare that to the Ares V. Losing just one of them would cost NASA practically half of its manned space budget.

Thirdly and probably most important advantage is the redundancy. This issue was driven home with the shuttle when it failed. Fact is that when you build these large launch systems you create a single point failure. You fact the prospect that if something goes wrong with your launch system you lose the capability completely. Fortunately we had a backup, the only commercial manned rocket in the world, the Soyuz. On the other hand if you choose an architecture based on commercial rockets than you have many rockets to choose from and great redundancy. If one rocket has problems you simply switch to another.

 

[edkyle99]

... there are commercial rockets currently available that have a demonstrated high reliability of over 95%. Some such as the Delta II are over 98%. If you choose to develop a new heavy lift system it is not likely that you will be able to achieve such high reliability ratings due to the fact that we have relatively little experience with that large a launch system.

I would count STS as a large launch system. It places more than 100 tonnes into orbit during each flight, and has done so 130 times in 131 attempts, making it one of the world's most reliable launch systems. Delta 2 has flown only a few more times (147) than STS. I see no reason that a large launch system can't be as reliable as a smaller system, as long as the propulsion is also scaled so as to keep the number of engines or motors reasonable. (SRB, which produces 6.6-ish million pounds of thrust using just two big motors, has been key, IMO, to Shuttle's reliability results - but this is all history now.)

That said, I agree that it should be possible to perform deep space missions using smaller rockets combined with a LEO propellant depot approach. The risk with such an approach won't necessarily be dominated by launch failures, since a lot can go wrong in orbit. Some redundancy will be required for propellant flights at least.

- Ed Kyle

 

[rcsplinters]

Actually, Darkened, there are several aspect to my post that was less than rigorous. However, the underlying principle is quite sound and taught in any elementary probability and statistics course. The concept is less than intuitive but the question we are all asking is, given n flights, what's the chance that we incur at least one failure which results in loss of payload (not meaning to be callous about the crew, but its the final assembly that's our focus for now). So if you have p the probability of failure (and I may have stated this backwards earlier) then the probability of at least one failure is 1-(1-p)^n over n flights.

I cranked out a few numbers for fun. To start with, I sincerely hope you are wrong about the success rate on commercial rockets. For 10 missions to complete an assembly with an individual flight success of .95, we find that the chance of at least one failure is about 40%. Over 30 missions, that number is a startling 78% of at least one failure. I suspect the commercial industry has a MUCH better success rate than 95%.

I also looked at the numbers with the shuttle. The last loss of craft failure rate I saw for them was 1.5% and that seems to have been its track record. Don't quote me on the numbers though, I didn't go back to research them fully. These will do for conversation sake. At that loss of craft rate, over 10 missions we'd expect at least one failure at about 14%. Over 30 missions you'd expect about at 36% chance of at least one catastrophic failure. If we look at an individual failure rate of .5%, then we come back in line with the 10 mission performance for a 30 mission assembly. What this tells us is that an HLV vehicle can offer similar or better expectations of a successful assembly with a lower individual mission success rate. We can essentially ignore redundancy in the booster as this is factored into its individual mission success rate.

Now these are nowhere close to engineering class computations on which we'd invest billions. They do qualitatively illustrate the risks involved with multiple missions for orbital assembly and the benefits of large booster capabilty on the success expectation of the final assembly. We should find this to be no surprise. Otherwise we'd have one booster size and they'd just build what they need in orbit with multiple trips. You factor this into the fact that you don't have to lift that first and second stages over and over again and you see why NASA, ESA and the Russians have built successively larger boosters. We will see that trend continue, at least in Russia, ESA and China. THe Augustine report reached essentially the same conclusion that heavy lift was a critical capability beyond LEO.

 

[Capricorn_One]

Since Falcon 9 is still more fiction than fact, it should probably not be referenced as a launch alternative...

 

[Windbourne]

Is heavy lift a distraction? No. The current obsession with getting Ares V/I going IS the distraction. Look, having a craft that you use once or twice a year is EXPENSIVE to run and a mistake. Instead, we should be focused on getting our current rocket capabilities to being used heavily. That means that we need to invest into private space stations and getting businesses to use these. In the mean time, we do the research for tugs/fuel depot.
Finally, help give the push to private space to head to the moon. When we leave LEO, we will need a super-heavy to lift to LEO large items, such as the BA balloon units. There is little doubt in my mind that when we go to the moon and one to mars, that the very first base will be based on balloon structures. Large ones MUST be sent up as a single unit.

 

[job1207]

The thinking is this. The only place you can go with a conventional rocket is to the moon. So the US is going to build a next gen rocket. Personally, I would dust off the Saturn 5 plans, put the exotic engine at the top and have at it. Once the exotic engine is developed.

We have heavy lift, we do not have to reinvent the wheel, yet again.

 

[EarthlingX]

dV is not on the side of Moon being a first step in space resource utilization. There are many other things you can do on the Moon with tele-presence from Earth, as we will see in the relatively near future. It could (and very likely will) be used as a test site for more distant robotic activities, while preparing ground for people.

It is the most visible destination, but not the closest - we are just beginning to find out about millions and millions tons of ice and rocks much closer to LEO.

Fuel depots make sense, since you would otherwise need to launch a lot in a rather short time. Solving problem with hydrogen evaporation is easy - do not use it, use some other fuel, which doesn't evaporate.

It will take some time, before there will be hydrogen or oxygen in-space production - use other fuels before that.

I like that idea about 50t-60t Common Booster Core, since it makes most sense, if market can support it with regular flights, and i suspect that no to be too much of a problem, especially if there are multiple-payloads, which are not so uncommon.

 

[dgilsdorf]

Most of what I would have said has already been said, including storing fuel long term as water and using electrolysis to convert it when needed. I agree with those who have said that heavy lift beyond what we have is an unnecessary luxury, given what we can do with on-orbit construction. That said, OTRAG lives, and will deliver heavy lift as it continues to develop. Armadillo Aerospace is developing a similar, parallel-staged approach in the US, if we insist on being economic protectionists about it.

What I still need to say is a word of caution about exploiting lunar water as fuel. It is a limited resource, and bringing more of it to Luna to stay would be an expensive proposition. If we are to maintain a long-term human presence on Luna, we need to keep a reliable supply of water there for colony use. On Earth, the water that is exhausted from our rockets is returned to the water cycle. On Luna, a similar statement would be nonsense; nearly all of the exhaust would be lost to space.

 

[holmec]

There are a couple of basic problems with building with small parts in orbit (obviously there are some good things as well), but since you asked here are the problems:

1. Fuel storage in orbit. This problem needs to be licked before building in orbit can be solved. Fuel just doesn’t do very well in the heat and cold of space. There is no real data on how that fuel will hold up in orbit. Some obviously some work needs to be done to get some data points on this subject.

I keep seeing people say that, and it is in the Obama Space Plan, but I wonder, why would you store fuel in orbit? Why not simply wait until it is needed before launching it?

In other words, let's say you are going to assemble a vehicle to go to an asteroid. You put the crew habitation and command module in orbit. Then, you prep another module, which has the propulsion device (chemical rocket, vasimr, whatever), and you put that in orbit. Then, you launch a fuel module containing the fuel. Finally, you launch the people on a space taxi. All these launches are using commercial rockets such as Delta IV or Falcon 9 or whatever.

The module with the fuel should not stay up for more than, say, two or three days before the people go up and you leave.

I don't really see why you would have a fuel depot in LEO unless you're somehow generating the fuel in LEO. Otherwise, you have to launch the fuel to put into the depot, which itself requires fuel.

--Brian

I love this idea. The problem is that its a mental change. What I mean is that NASA has had the mindset of making big rockets to use expendable space operations (other than shuttle orbiter) assets.

If you start building reusable assets in orbit, then you can save money by making the most of your launches to supply consumables and crew to the ship. Call it a tug, call it a starship, but it needs to be reusable. Put chem rockets or VASIMIR like plasma thrusters, and get commercial companies to supply the fuel.

Then it can go to asteroid, moon, mars....wherever, manned or unmanned. Put a hab on it and its a temporary station on whatever its orbiting.

How to get it back in Earth orbit? I suggest let the crew depart on a capsule for landing, and the craft can use aerobraking to get back into a servicing orbit.

But this would require a mindset change in NASA.

 

[JonClarke]

The thinking is this. The only place you can go with a conventional rocket is to the moon.

Also Mars and NEAs

Personally, I would dust off the Saturn 5 plans...

The tooling for most of it (except the J-2 engine) does not exist. Most of the suppliers do not exist. There have been advances in electronics, materails, and design techniques. It would be easier, cheaper and better to do a new design (but of course taking advantage of Saturn experience where relevant. Also the Shuttle.

put the exotic engine at the top and have at it. Once the exotic engine is developed.

No need for an exotic engine. Whatever that is.

We have heavy lift, we do not have to reinvent the wheel, yet again.

Indeed we have. It is called the Shuttle

 

[JonClarke]

I love this idea. The problem is that its a mental change. What I mean is that NASA has had the mindset of making big rockets to use expendable space operations (other than shuttle orbiter) assets.

If you start building reusable assets in orbit, then you can save money by making the most of your launches to supply consumables and crew to the ship. Call it a tug, call it a starship, but it needs to be reusable. Put chem rockets or VASIMIR like plasma thrusters, and get commercial companies to supply the fuel.

Then it can go to asteroid, moon, mars....wherever, manned or unmanned. Put a hab on it and its a temporary station on whatever its orbiting.

How to get it back in Earth orbit? I suggest let the crew depart on a capsule for landing, and the craft can use aerobraking to get back into a servicing orbit.

But this would require a mindset change in NASA.

You don't need a mind set change at NASA. All these options have been exhaustively studied. What is needed is a mindset change among US politicians across the board.

 

[DarkenedOne]

I would count STS as a large launch system. It places more than 100 tonnes into orbit during each flight, and has done so 130 times in 131 attempts, making it one of the world's most reliable launch systems. Delta 2 has flown only a few more times (147) than STS. I see no reason that a large launch system can't be as reliable as a smaller system, as long as the propulsion is also scaled so as to keep the number of engines or motors reasonable. (SRB, which produces 6.6-ish million pounds of thrust using just two big motors, has been key, IMO, to Shuttle's reliability results - but this is all history now.)

Well generally less experience leads to less reliability. Yes the Shuttle has flown 131 times, put that pales in comparison to the number of launches made by Delta II class vehicles. Also when talking about super heavy lift like the Ares V these vehicles are in a whole class of their own.

That said, I agree that it should be possible to perform deep space missions using smaller rockets combined with a LEO propellant depot approach. The risk with such an approach won't necessarily be dominated by launch failures, since a lot can go wrong in orbit. Some redundancy will be required for propellant flights at least.

- Ed Kyle

Truth is that most of the problems associated with space flight are with the launch and reentry. All the deaths that have occurred in space flight have been on the way up and on the way down. We have yet to have someone die in space.

 

[holmec]

I love this idea. The problem is that its a mental change. What I mean is that NASA has had the mindset of making big rockets to use expendable space operations (other than shuttle orbiter) assets.

If you start building reusable assets in orbit, then you can save money by making the most of your launches to supply consumables and crew to the ship. Call it a tug, call it a starship, but it needs to be reusable. Put chem rockets or VASIMIR like plasma thrusters, and get commercial companies to supply the fuel.

Then it can go to asteroid, moon, mars....wherever, manned or unmanned. Put a hab on it and its a temporary station on whatever its orbiting.

How to get it back in Earth orbit? I suggest let the crew depart on a capsule for landing, and the craft can use aerobraking to get back into a servicing orbit.

But this would require a mindset change in NASA.

You don't need a mind set change at NASA. All these options have been exhaustively studied. What is needed is a mindset change among US politicians across the board.

Studying them and putting them into action is the difference. NASA studies a lot. Its management that puts into action (to include Congress). So still the mindset needs to change. I think this Obama space plan could be the beginning of such a change.

The russians are already there. Their way of going to the moon is using their existing rockets and the ISS to build a stack that will go to the moon.

 

[Paul_L_Smith]

The only problem with the Shuttle Stack is the Orbiter. Too many things to check out and refurbish. The SRB's, ET and SSME's are all good, proven designs and when you are dealing with human space flight you want PROVEN reliable designs and hardware. Take a look at http://www.directlauncher.com. This plan uses the existing shuttle stack minus the orbiter.

It could be OPERATIONAL by 2015 for a lot less than even ARES I.

It also offers a lot of room for growth and would save a lot of the NASA workforce and talent and keep the USA on top in manned access to space.

 

[rockett]

The thinking is this. The only place you can go with a conventional rocket is to the moon. So the US is going to build a next gen rocket. Personally, I would dust off the Saturn 5 plans, put the exotic engine at the top and have at it. Once the exotic engine is developed.

We have heavy lift, we do not have to reinvent the wheel, yet again.

We can't. The plans are gone, many of the people are gone, and much of the tech is gone. When they started Constellation, the only thing they could find was the J2X second stage engine. Everything else was lost.

 

[rockett]

The only problem with the Shuttle Stack is the Orbiter. Too many things to check out and refurbish. The SRB's, ET and SSME's are all good, proven designs and when you are dealing with human space flight you want PROVEN reliable designs and hardware. Take a look at http://www.directlauncher.com. This plan uses the existing shuttle stack minus the orbiter.

It could be OPERATIONAL by 2015 for a lot less than even ARES I.

It also offers a lot of room for growth and would save a lot of the NASA workforce and talent and keep the USA on top in manned access to space.

This has already been discussed elsewhere. This thread for one:
We should do Direct 3.0 Shuttle Derived Heavy Lift Launcher
http://www.space.com/common/forums/viewtopic.php?f=15&t=23421&p=443500&hilit=direct#p443500

A search will turn up still more...

 

[Aggelos]

The only problem with the Shuttle Stack is the Orbiter.

the srb exploded with Challenger..and there are heatings units on srbs to warm the rubber joints in the cold days.all that maybe should end ,and be replaced with a kerolox core and more(5 or more) one piece Composite srbs,,like of deltas ,or atlasV....