Robert Zubrin is the head of the Mars Society and has written several books how to really do space exploration. I like his engineering, though his philosophy comes off as a bit naive sometimes. Still, he knows his stuff.
On space.com last week, he discussed the new plans to go to the Moon and to build a “heavy lift vehicle” or HLV. We’ll need this to get to the Moon and planets. He also discussed the Shuttle, of which he is obviously not a fan. NASA wants to keep the Shuttle going for a few more years to complete building the space station, as well as repair Hubble.
This bit by Zubrin caught my eye:
The only really time-critical shuttle mission is Hubble Space Telescope repair. This is indeed a truly important mission, and it should be flown with dispatch, as it is without question worthy of the 2-percent risk to crew that any shuttle mission must entail. But the rest of the shuttle manifest is devoted to space station construction, and these cargos could be delivered much more expeditiously by the HLV that NASA needs to develop to reach the Moon anyway.
Griffin’s HLV design will be able to deliver 125 metric tons to low Earth orbit. The shuttle can only deliver 20 tons. With a single launch then, the HLV will be able to deliver as much payload as the shuttle program can during a year — and that’s during a good year.
Compared to current shuttle launch rates, which will have managed only one flight between February 2003 and February 2006, (at a cost of $15 billion), the HLV will be able to launch in an afternoon everything the shuttle program would be able to launch for the next 18 years.
I wonder how accurate that statement is… usually a comparison like this is an oversimplification. Still, it does show how wasteful the Shuttle is, and how we should work on a better vehicle to replace it sooner rather than later.
December 15th, 2005 at 3:04 pm
Interesting commentary.
I agree on the time-sensitivity of Hubble, and it’s continued value to astronomy.
Regarding launch payload size, he is probably correct when he talks about the HLV being much better suited to launching the components.
There is a couple of problems with the comparison.
1. The ISS modules and such are sized in certain ways, constrained by the Shuttle payload bay. There is a certain amount of external work required to assemble the station. Theoretically, the payload elements could be assembled better/more and launched assembled, reducing the external assembly time. Practically, that will depend in large part upon the design of the HLV – attach points, payload packing size, etc. Also, the structures may not be able to handle the HLV loads in that configuration. So certainly there would be a LOT of work in repackaging Shuttle sized launch packages for a new vehicle that doesn’t exist yet.
2. There is still a need for a sizable crew for assembly, independent of the need for extended crew operations. This would necessitate a dual launch, or a crewed portion of the HLV. I am under the impression the HLV is to be uncrewed.
3. The Shuttle still has one capability I have not seen on any of the new vehicle plans (though I haven’t looked at them very thoroughly, so I may be missing something) – the Shuttle has the ability to return sizeable payloads to Earth, safely.
However, this is a problem even with the existing plan, because the intent is to retire Shuttle after assembly complete. The ISS was designed with teh assumption it would be regularly serviced by the Shuttle. This means that the philosophy is based upon removeable and replaceable items (Orbital Replacement Units, ORUs) that are serviced/repaired on the ground. The intent is to reduce the on-orbit maintenance time by trading out used/broken items for new ones and sending the others home for refurbishment/repair. This is critical for numerous items that have a use life and then must be refurbished. Without the ability to return the hardware from Orbit, this means fabricating replacement units from scratch, rather than tweaking hardware that is mostly good. Like throwing away your car and buying a new one instead of getting an oil change. This philosophy of ground servicing is in jeopardy if the Shuttle is not replaced by a vehicle with return capability.
We are currently facing problems from that operational mode. Without Shuttle running regularly, there are only two servicing vehicles. The Progress Module has about 1/3 of the payload volume of the Shuttle, and can only be used for delivery to Station. It is ejected (full of garbage) and burns up on reentry. The Soyuz is the 3 person crew vehicle. It goes up and down, but has a very limited hardware payload capability, primarily due to space and safety constraints for the crew. Ergo, it cannot be used for heavy/large item servicing. Thus, the ISS got awfully full of things that needed to be returned to the ground that NASA didn’t want to throw away (because they’re EXPENSIVE) but didn’t have a way to get down. The latest mission helped in that respect, as it was a logistics flight, but we’re not out of the woods yet. And the scary thing is even the current plan calls for Shuttle to end service while ISS is beginning full use.
I also don’t think the current launch rates comparison is all that fair. We have only had one mission in 3 years primarily because of the break in service to repair the flaws from Columbia. That isn’t representative of what Shuttle should or will be doing. A more fair assumption might be 4 flights a year.
Disclosure – I work on equipment for use on the ISS by the astronauts. I’m not a Shuttle employee, but I have worked on Shuttle flights.
December 15th, 2005 at 4:56 pm
3. The Shuttle still has one capability I have not seen on any of the new vehicle plans (though I haven’t looked at them very thoroughly, so I may be missing something) – the Shuttle has the ability to return sizeable payloads to Earth, safely.
How many times has this facility been used? Once? Twice? Is it really worth aroung $1Bn a flight?
The shuttle is actually a 100-ton+ LEO launcher. Unfortunately, 85 tons is the vehicle itself.
December 15th, 2005 at 5:42 pm
Very comprehensive (and good) entry Irishman.
What I have always failed to understand is the “all eggs in one basket” mentality that says the Shuttle is an all or nothing prospect. Wouldn’t the program be better served with a few select launch options for manned flight?
Bottomline, I just hope that the manned space program gets back on a productive track and neither the Hubble or ISS are jeapordized.
December 15th, 2005 at 7:27 pm
One point:
“Griffin’s HLV design will be able to deliver 125 metric tons to low Earth orbit.”
Yes but when you get it there what are you going to do with it? You have to have a manned launch or a robotic cargo ship to move the cargo.
Yes the shuttle is a 100t LEO however most derivative designs have a payload of about 65t – studies are called the Shuttle-C.
Griffin’s designs throw away SSMEs that are only produced at the rate of about 4 per year as they are exceedingly complicated and difficult to build as they have such a high Isp – I am not sure how that is to be resolved.
We actually have a HLLV already. The Delta 4 heavy has the capability with progressive modifications to be a 60t or 80t to LEO launcher. It also uses engines that are designed to be thrown away.
Also as much as I admire Zubrin for his Mars Direct work he does have a bit of a all-up obsession. It is not clear that a successful Mars spacecraft cannot be assembled safely in orbit from smaller modules.
Also I do not like at all the CEV being launched on a solid rocket. That is not good design. The CEV should be made universal so it can be launched on any current launcher such as the Atlas 5 or Delta4 or even the Ariane 5 or Proton
December 15th, 2005 at 9:42 pm
Zubrin has some great points. I guess I’m somewhere in the middle. I think we should fly the minimum number of shuttle flights to support ISS building and supply while we focus our resources on the CEV/CLV and also on the HLV. A flight to HST and maybe a half dozen ISS flights are probably all we should fly. Shuttle takes away from the HLV work and the sooner we get started the better our future in space will be. CEV and CLV can both support ISS by providing crew support and s launch capability for anything that does not require the larger HLV capacity. Not much in the pipeline for ISS will benefit from HLV since most of it is built or nearly built and designed for Shuttle delivery.
If Shuttle is to be retired in 2010, we’ll have about 4 years of flights and if 18 flights are required to complete ISS, there’s no way the 3 orbiters and current flight capability can provide that many flights. Especially with the constraints Shuttle is being forced to fly with.
Jim.
December 16th, 2005 at 6:56 am
An earlier post wondered how many times the shuttle has been used to return items to Earth. A look at the station launch manifest shows that the Multi Purpose Logistics Modules have been used 6 times so far to bring supplies to the station and then return items to Earth. The items are completed science experiments, science racks, and other items no longer needed on the station including garbage.
Anyone know how many non-ISS flights brought back items from space?
December 16th, 2005 at 8:46 am
Hey Phil. I’m a new reader and only came across your blog this week. I’ve been an armchair astronomer since I was a kid. I agree, the space shuttle needs to be mothballed. We need another mechanism to get “stuff” into space and the shuttle is not an economical way to do it. An HLV is a great idea but there are still cost factors associated with R&D, construction, and tests. But one would tend to think that we could save a boat load of cake if we could make it happen, then we could spend money on cheap exploratory missions like the one going to Pluto and the like. The U.S. has its ass on the line to finish the ISS, and we are behind. I noticed over at the Nasa site there is a cool animation that shows how we could return to the moon. I think it was strange seeing a 21st century version of a late 60’s lunar lander and command module.
December 16th, 2005 at 8:48 am
“Anyone know how many non-ISS flights brought back items from space?”
I don’t know definitively, but I do recall that at least one failed satellite was returned for repair & re-orbit, and the LDEF was returned.
It’s important to note, however, that for the cost of returning old objects from orbit, then refurbishing & re-orbiting them is particularly wasteful. The only thing saved is the cost of worn out components. The mass of a shuttle orbiter always far exceeds that of the payload it carries, so to put an old, repaired satellite back on orbit with the shuttle incurrs the cost of lifting the orbiter, and yet the orbiter has nothing to do with the functionality of the payload. It’s cheaper just to factor in retiring old satellites and replacing them with lower cost throwaway boosters.
December 16th, 2005 at 9:32 am
Jeff says:
> I noticed over at the Nasa site there is a cool animation that shows how we could return to the moon. I think it was strange seeing a 21st century version of a late 60’s lunar lander and command module.
Yeah, that was pretty neat! Amazing what they can do with CGI. I can’t help but think, though, “Great! We’re back to disposable capsules again.”
December 16th, 2005 at 10:47 am
I agree strongly with Zubrin about Hubble. To not send a mission to it is a travesty.
On the subject of ISS, I think that like Shuttle, NASA has started on something that they really can’t afford to do. ISS is in caretaker mode now – the astronauts and cosmonauts who spend time on station are spending the vast majority of their time as maintenance engineers. All the ISS countries need to get together and take a hard look at what it would take to get ISS finished *and* whether there is a reasonable plan for really using it when it’s done.
For my money, you can’t use ISS until you can get more crew onto it, and to do that requires a different crew delivery vehicle, presumably one that’s an order of magnitude cheaper per launch.
Until you reach that point, I don’t see any sense at using shuttle as a space truck. Take the money you would have spent on the shuttle flights, use it to adapt the modules you need to launch to work on expendables, and then proceed when you’re ready.
Or, as an alternate option, pair one shuttle launch with a couple of modules on an expendable. Launch the shuttle first, let it do its work at station, then launch the expendable to a nearby orbit. Shuttle can go and get it, and take it to station.
Of course, none of this factors in any of the political realities (both international and domestic). Shuttle is as much an employment program as it is a space exploration program (okay, it’s *more* an employment program…), so making big changes would be disruptive.
December 16th, 2005 at 1:06 pm
JusANuttaBackYahdah Said:
>What I have always failed to understand is the “all eggs in one basket� mentality that says the Shuttle is an all or nothing prospect. Wouldn’t the program be better served with a few select launch options for manned flight?
As I understand the original premise, in order to get the frequency of flights up high enough for the reusability to start paying off, NASA had to drive all launches to the Shuttle. Since then, other realities have intruded upon that decision. Primarily the design of the Shuttle never lived up to the original dreams for servicability and turnaround. Also, there was a problem demonstrated by Challenger regarding having only one launch vehicle. Essentially, Shuttle just hasn’t performed the way it was envisioned.
Charles Randles Said:
>”the Shuttle has the ability to return sizeable payloads to Earth, safely.”
>How many times has this facility been used? Once? Twice? Is it really worth aroung $1Bn a flight?
Nancy Said:
>A look at the station launch manifest shows that the Multi Purpose Logistics Modules have been used 6 times so far to bring supplies to the station and then return items to Earth. The items are completed science experiments, science racks, and other items no longer needed on the station including garbage.
>Anyone know how many non-ISS flights brought back items from space?
Let me clarify my statements a bit. There’s different ways to use the Shuttle to return items.
1. Pick up something (like a satellite) that is in space and bring it down. This is inefficient and wasteful. It costs more to launch the Shuttle for the return than to build a new satellite from scratch.
2. Take large items up and then bring them back. Uses – Neurolab, Spacehab, work platforms to support Hubble refurbishment, etc. Effectively every Shuttle mission is currently in this mode to some extent now that the docking module is installed, but that’s considered a necessary “part of the orbiter” to accomplish ISS docking, so it’s debatable. Heavy lift launchers are great, except if you need their payloads crewed. Is your HLL crew-rated? Do you have a separate crew vehicle, which then requires a second launch and a rendezvous? If you want to do science in space (like life-science experiments), can you bring them back on your return vehicle?
3. Take somewhat smaller items up and down to support on orbit operations – ISS resupply (using the MPLM’s for instance). This is exactly the point I mean. Payload racks for ISS interior, clothing and dirty laundry, station equipment that needs repair, operational items that need regular servicing, air sampling kits, water sampling kits. Garbage can be ejected in the Progress Modules and good riddance, but a lot of stuff isn’t garbage just because it is used. Do we really want to throw all laundry away as garbage? (Exercise – add up all the underwear and socks needed for a crew of three to last six months, assuming reasonable number of times re-wearing your dirties. Determine a weight and volume for said amount of garments. No laundromat in space. Do you want the crew spending time doing laundry, or do you want to cycle back to Earth, or do you want to throw it all away after 1 or 2 uses? Justify your decision for cost and schedule. If laundry in space, justify resources in power consumption and water.)
Ender Said:
>Also as much as I admire Zubrin for his Mars Direct work he does have a bit of a all-up obsession. It is not clear that a successful Mars spacecraft cannot be assembled safely in orbit from smaller modules.
It is not just a matter of safe assembly, it is also a matter of cost-effective asssembly. ISS is an experiment in space assembly – not necessarily the best plan, but a plan. Still, on-orbit crew time is much more expensive than technicians in a shop on Earth. The more that is pre-assembled, the better.
>Also I do not like at all the CEV being launched on a solid rocket. That is not good design. The CEV should be made universal so it can be launched on any current launcher such as the Atlas 5 or Delta4 or even the Ariane 5 or Proton
There is the problem of ensuring your launcher is crew-rated. Just how safe are those alternate launchers? Solid launchers vs. liquid launchers is a separate argument than dedicated launcher vs. using any existing launcher.
December 16th, 2005 at 1:18 pm
Anyone read the Space Elevator book that was published not long ago? Essentially it is a summary of the feasibility report that NASA commissioned looking at building a carbon nanotube fiber tether to geosynch as a launch platform. While there were some assumptions and estimates I’m not able to fully evaluate, the plan presented seemed fairly comprehensive in addressing the issues, or at least identifying the areas that need more work to find answers. The plan scopes out not just building a tether, but considers operations, the expense, and methods for driving the launch cost per pound quickly down to the magic $100 per pound and less that we’ve all heard so much about.
What I found impressive was that the carbon nano-tube fabrication and strength issues are largely already being addressed in industry for other purposes, which means the space elevator tether would be more of an adaptation of commercially available materials than an original, stand-alone need. That means the manufacturing costs and availability are more reliable and cheaper than they would be otherwise. The bulk of the problems left to be resolved are purely engineering work, and not basic science or new technology drivers. That greatly supports the overall feasibility of the concept.
I’m heartened by the recent space elevator challenges that have been initiated to work on designs for climbing tethers powered by light. That is an element of the outlined plan that needs more attention.
The Space Elevator concept is a launch and return method that pushes the envelope while opening up space to greater exploration and commercial access. It truly is a new approach, as opposed to the current Moon/Mars plan.
December 16th, 2005 at 8:47 pm
There are many reasons to bring stuff back down from orbit. While it’s not enough to justify the cost of the Shuttle, iit definately worth something.
Example: Returning data from experiments. Say you just grew some odd crystals, or a cell culture. You want to bring those samples back down where they can be studied for years in a full-size, well equipped lab up close by scientists. Without downmass capability, you’re limited to whatever data you can collect with the highly weight-limited equipment in orbit, in the limited time budget of the station crew. Sometimes you can put your results into a seperate de-orbit package and send it back down by itself. But sometimes the valuable bit will be the whole experiment package, or it needs careful tending.
This is certainly not enough to justify the whole cost of the Shuttle program. But it isn’t worthless, either. And many ISS experiment packages have been designed on the assumption that the whole package will be returned to Earth for later study. It just goes into space to be exposed to microgravity and/or vacuum; the real results are measured on the ground afterwards. Those will need to be redesigned, and that’s going to be expensive.
December 17th, 2005 at 5:56 am
Irishman – Assembling pre-tested modules for a Mars spacecraft should be no harder than the ISS assembly. Also what happens if the HLLV fails at launch – then your whole mission is destroyed. At least with module assembly the whole mission is not in one flight.
The shuttle is the first manned spacecraft to use solid rockets and that was against the objections of some experienced hands. It came down to nothing else would get the thing off the ground and it was to expensive to develop liquid boosters.
The main problem with solid rockets is that once you light the blue touch powder they are off and unstoppable. Liquid fuel boosters can always be shut off in an emergency. If there is a problem with the solid booster at launch the CEV has to somehow seperate from a unstoppable rocket at hypersonic speeds and dynamic pressures. The Saturn V of Apollo had no solids neither does the Soyuz launcher.
To man rate a Delta 4 or Atlas 5 the destruct charge has to be removed and a few dummy flights made. However there is nothing in their design that is different from the Atlas rocket that launched all the Gemini missions.
December 19th, 2005 at 3:24 pm
ender Said:
>Irishman – Assembling pre-tested modules for a Mars spacecraft should be no harder than the ISS assembly.
Admittedly, ISS assembly isn’t necessarily the smartest or easiest, either. But we are learning by experience. I think there’s something to be said for launching larger packages on larger launchers with less assembly. Shuttle isn’t necessarily the best plan, either. I’m not committed either way. There are trade offs that have to be made to come up with a plan.
>Also what happens if the HLLV fails at launch – then your whole mission is destroyed. At least with module assembly the whole mission is not in one flight.
True, but depending upon orbital periods, resource constraints (such as cryo fuel), and other factors, there may be time constraints for on-orbit that do not go well with a critical element in the middle of the assembly sequence disappearing. It isn’t economical or practical to built two of everything on the off chance there’s an explosion, so the recovery plan in that case would need to be developed carefully. All of which just means we need a good, thorough plan before we begin work.
>The shuttle is the first manned spacecraft to use solid rockets and that was against the objections of some experienced hands.
Let me be clear, I’m not advocating solid boosters. I agree with your objections. My objection was to crew-rating the existing rocket designs after the fact. It may be doable, but is it really cheaper than designing from scratch a unique launcher for this application?
>To man rate a Delta 4 or Atlas 5 the destruct charge has to be removed and a few dummy flights made. However there is nothing in their design that is different from the Atlas rocket that launched all the Gemini missions.
I’m not so certain of this, though I don’t really know the details. There are certain reliability levels that we would want for a crew-rated vehicle that are not necessarily required for a non-crewed launcher.
December 19th, 2005 at 7:59 pm
Irishman – true enough – there must be a balance between lift mass and assembly. Cryo fuel is a huge problem and I don’t think storables have the Isp. Maybe we will have to revive H2O2 and RP7 (Isp285).
I would have thought the man rating existing boosters would be far easier. Gemini and Mercury all used modified ICBMs. The only purpose designed manned rocket was Apollo and the Saturn V. The Soyuz launches both manned and unmanned payloads and was developed from an ICBM.
There is just something about the ’stick’ design of the Crew Launch Vehicle that does not look right. The EELV launchers were considered however I think political reasons to reuse as much of the shuttle hardware as possible took over.
http://www.geocities.com/i_s_s_alpha/launch_vehicles.htm
December 20th, 2005 at 9:49 am
Thanks, Ender.
October 24th, 2006 at 5:16 pm
Thanks to you both. This is one of the best discussions of this topic I have read & makes a host of very valid points. Having studied the Space Elevator book at some depth (but no longer have it handy having loaned it to a friend) I can say that there are some important materials problems still to solve. …Unless you guys can point me to a source I have missed.
While carbon nannotubes are theoretically strong enough & light enough we can so far only make very short ones and cannot bind them into cables with anything like the strength/weight properties required. There is some very promising work from CRIRO and Uni of Texas twisting them into ‘yarn’ and a company has been able to launch and attract investment on the basis of the Space Elevator but there is also some work which suggests we can never make cables with the strength required! Not out of carbon nannotubes anyway and nothing else comes close.
I think we all fervently hope the materials problems can be overcome as it would deliver the cheap access to space that we need to make space exploration/exploitation truly economically viable.