Armchair Quaterback Manned Spaceflight

Great Debates
1

After the Columbia disaster, there is considerable question as to what NASA’s priorities should be in regards to manned spaceflight. Here’s what I think we should do:

  1. Keep the remaining three shuttles flying long enough to complete the ISS. We should stick to our original commitment and add another habitation module which will eventually bring the permanent crew to 7. This is important for reasons that will be clear presently.

  2. The last shuttle flight should be to retrieve the Hubble for display at the Smithsonian Air and Space Museum.

  3. Meanwhile, we should replace the shuttle with a scramjet-powered, two stage spaceplane with limited cargo capacity designed only for manned spaceflight to and from the ISS, which will be the jumping-off point for all future missions. Expendable boosters should henceforth be employed to carry cargo to orbit. Research into a space elevator should also go forward, but priority should be given to the spaceplane. The goal here is cheap, reliable, quick human access to space.

  4. Using the ISS as a staging area, a new class of craft should be built. Instead of building specialized vehicles for each mission, the Vibrotronica-class ships will be flexible and as self-contained as possible. The core craft will consist of a habitation module with enough room for a crew of seven or eight and a drive module. Specialized hardware, such as landers or science modules or whatever, can be fabricated and attached as needed. I thinking of something along the lines of a mobile, nuclear-powered ISS here, designed to last for decades and able to take smaller crews on missions lasting three or four years. Perhaps even the drive unit should be designed for replacement in case something better (like fusion) comes along. Perhaps a solar sail could be used as supplimental propulsion. All ideas are on the table.

  5. The Vibrotronica’s shakedown assignment will be a renewed program of lunar exploration culminating in the establishment of a base at the lunar south pole. Perhaps a test space elevator could be constructed on the moon as well, since it seems like it’s a lot easier to do it up there than on the Earth. The goals of this lunar program are to identify exploitable lunar resources and develop techniques for sustainable space habitation that we will then use elsewhere in the solar system. IMHO, it’s better to do the testing three days flight from earth than six month’s flight!

  6. Next, the Vibrotronica or one of her sister ships will do a survey of near-Earth asteroids, with similar goals.

  7. Now that we’ve got the bugs worked out of our new ship, it’s on to Mars. We should establish a base on Phobos, restaffed by periodic trips from Earth by the Vibrotronica-class ships and resuppied by unmanned freighters. Short trips to the surface from the base will eventually evolve into longer stays. The goal is a permanent presence on the surface.

That should keep us busy for a century or so. You’ll notice that it takes a long time to get to Mars in my plan, but that’s OK with me. I’d much rather do it right than stage an Apollo-type dash to the Red Planet. The underlying philosophy is building an infrastructure that will allow a sustained program of manned planetary exploration.

Comments are invited on my plan, which is admittedly incomplete but intended mainly as a jumping-off point for discussion. If you have your own plan, now’s the time to let us know about it. I will ask that those people who oppose manned spaceflight in favor of robotic exploration (which is a perfectly legitimate point of view with many merits) refrain from posting in this thread.

2

Any particular reason for making it a scramjet? You’re addind a lot of extra complexity, weight, and cost for a minor gain in weight fraction. Not having to bring oxygen along for the first part of the trip only marginally offsets the extra weigth of the scramjet and hypersonic inlet and the extra fuel and TPS you have to bring along to survive prolonged hypersonic flight. In fact, I’ve seen math which suggests it may make your vehicle even heavier in the end. A conventional rocket TSTO can be developed with technology that actually exists today.

How so? Doesn’t the moon’s much slower rotation rate make putting a space elevator there much, much harder?

3

Aw Man!!! (I’m on a roll, tonight!) Using the “last” shuttle flight to “retrieve the Hubble Telescope” is the most ridiculous statement I have EVER heard!

Space travel is fraught with danger! EVERY Astronaut (or even pretenders like Christy McAuliffe) KNOW that they are putting their lives on the line!

I would guess that EVERY one of them would say that they would give their lives to CONTINUE the space program!

If you think that ANY of our dead astronauts think we should stop exploration, because of their deaths, I think you are SERIOSLY mistaken!

4

In what alternate parallel universe does one not consider Christa McAuliffe an astronaut?

5

The one where retrieving the Hubble is “the most ridiculous statement I have EVER heard!” link

AndrewL the 1/6 gravity of the moon would allow for a smaller and therefore less massive tether which might be doable with current or near term materials and not mono-diamond filament with carbon nanotube reinforcement.:stuck_out_tongue:

6

Although I don’t really take the comments of someone who ends every sentence in their post with an exclaimation point seriously, I must ask, why do you think that? The Hubble will be retired eventually in favor of the Next Generation Space Telescope and must be retrieved or deorbited so there is no danger of it falling in an inhabited area. Since it has no retro rockets or engines to speak of, it’s going to have to be retrieved by the shuttle.

I’m flexible on that point. I’ve been reading about the technology and figured an air breather was the way to go. The requirements for the spaceplane are that it’s cheap to fly with a minimum of maintanence and hassle. If a chemical rocket can deliver on that, so be it.

Hmm…Hadn’t thought of that. I was figuring the lower gravity and lack of atmosphere would make it easier.

7

[Hijack]

I’d just like to note that the explanation that rocket technology is the proven, safe, available now technology has been used for 50 years, yet rocket still do not have a particularly enviable safety record. Airbreathing engines have advantages other than just payload fraction, including gentler flight profiles (sustained .3 G’s comparable to a passenger jet) and (theoretically) reusability. An airbreathing vehicle will tend to spend a higher portion of its trajectory within the atmosphere (compared to the shuttle, which IIRC does most of its accelerating only in the upper reaches of the atmosophere).

AndrewL is certainly correct about the increased structural fraction and complexity of an airbreathing engine, especially as many proposed spaceplanes are combined cycle engines, combinining ram/scram with either rockets or turbines (or both). It is not a cinch to say that rockets are the obvious choice though.

I don’t know if all current thinking calls for two stages to orbit - for a while single stage to orbit was the wave of the future for hypersonic airbreathing propulsion (thinking back to mid-late nineties Advanced Reusable Transportation Technologies program). The principal advantage of SSTO over TSTO is reduced labor costs (1 vehicle = 1 crew) at the price of increased complexity.

Finally I’d like to note that I am not a disinterested bystander as I work for a company that is closely tied to the hypersonic airbreathing community.

[/hijack]

8

[Hijack]

I’d just like to note that the explanation that rocket technology is the proven, safe, available now technology has been used for 50 years, yet rocket still do not have a particularly enviable safety record. Airbreathing engines have advantages other than just payload fraction, including gentler flight profiles (sustained .3 G’s comparable to a passenger jet) and (theoretically) reusability. An airbreathing vehicle will tend to spend a higher portion of its trajectory within the atmosphere (compared to the shuttle, which IIRC does most of its accelerating only in the upper reaches of the atmosophere).

AndrewL is certainly correct about the increased structural fraction and complexity of an airbreathing engine, especially as many proposed spaceplanes are combined cycle engines, combinining ram/scram with either rockets or turbines (or both). It is not a cinch to say that rockets are the obvious choice though.

I don’t know if all current thinking calls for two stages to orbit - for a while single stage to orbit was the wave of the future for hypersonic airbreathing propulsion (thinking back to mid-late nineties Advanced Reusable Transportation Technologies program). The principal advantage of SSTO over TSTO is reduced labor costs (1 vehicle = 1 crew) at the price of increased complexity.

Finally I’d like to note that I am not a disinterested bystander as I work for a company that is closely tied to the hypersonic airbreathing community.

[/hijack]

**Vibrotronica[\b]

As step 3.5 you should play around with sending unmanned versions of the Vibrotronica to presend supplies along more efficient trajectories to await you at Mars (standard SF planning). This will allow you to check out some systems in extended performance without risking crew.

The only risk of slow and steady is that steady (funding) is not guaranteed without something to whet the appetites of the public/congress. I agree though that having a meaningful program is better than a PR stunt, no matter how impressive.

Just out of curiosity, what do we do when we get to Mars?

9

Keep moving.

10

The ultimate goal of the space program should be to establish a self-sustaining manned moonbase for the purpose of manufacturing all of our satellites, probes, and spacecraft because it takes far less energy to launch from the moon and travel all the way into earth orbit than it does to launch from earth into earth orbit.

11

We blow it up with our illudium PU-32 explosive space modulator.

That’ll teach 'em to obstruct our view of Jupiter!

12

This book should be part of the discussion, I think. The author makes a very good case that the asteroids are an enormously productive potential resource just waiting to be exploited. If we’re going to expand manned spaceflight beyond the Moon, there are a number of NEOs (near-Earth objects) in highly eccentric orbits that would be a lot easier to get to than Mars, and from which major economic rewards could potentially be reaped.

The central point is, in the current political climate, exploration for the sake of exploration is a non-starter. Any program must have a visible break-even mark, followed by profit. According to Lewis’s rather eye-opening book, there are trillions of dollars just floating around out there, if we could only figure out how to get at them. In my opinion, with a little vision, space exploration can and will be driven by industry rather than by public-program fiat.

In the near term, though, I like the “Mars Prize” approach. If the government decides to go to Mars, they have to pay for all the contractor overhead, bureacracy, and so forth. Price tag of the bargain-basement Zubrin plan: $20-30 billion. If you took that same $20 billion, set it aside, and said, “First team to meet the conditions in the appendix gets the cash,” the price would be cut in half.

$10 billion is a perfectly reasonable cost to go to Mars. What is that, three or four high-tech Stealth bombers? It’s just a sad reality that for bureaucratic reasons no government program could succeed with it.

Oh, and I think a moonbase is much more difficult than people realize. It would be easier to create a self-sufficient facility on Mars, not least because of the availability of water. Sure, the moonbase has been a staple of SF for decades, and it has a definite emotional pull, but from a pure engineering standpoint it’s kind of a pipe dream.

I say we go straight for Mars and the asteroids.

13

The availability of water is the reason I located the moon base at the lunar south pole, where there are perpetually-shadowed craters that probably contain water.

14

Yes, that’s true. But there are two major problems with locating moon bases at the poles: First, those regions are much more mountainous than the rest of the moon, which makes excavation a hassle (I assume you’re digging in, to protect from cosmic rays, rather than dropping a lead-lined blister on the surface). Second, reaching the poles is a lot more difficult from an orbital-insertion standpoint; burning the fuel to make a polar landing goes a long way toward negating the gravity-well advantage, which is most of the reason for having a base on the moon in the first place.

15

It’s not just the gravity well advantage, it’s the no atmosphere advantage as well and if we want to get to mars and the asteroids the moon is the better launch point than eath.

16

The lessened gravity helps you, but the slowed rotation rate hutrs you more. An orbital tether needs to reach up past the synchronous orbit point, which is further away for a more slowly rotating body. In fact, I’m not sure that a sybchronous orbit even exists for the moon - you’d probably have to have the tether extending out through one of the lagrange points or something.

Besides which it’s not like it’s hard to get to and from the surface of the moon; a single-stage, reusable lunar-surface-to-lunar-orbit ship would be pretty easy to build. It’s getting off the earth that’s the hard part.

If cost of development is the issue, TSTO with conventional rockets is the cheapest and easiest to develop. Unfortunatly, it’s tricky to make a TSTo fully reuseable - the lower stage has to seperate and fly back to some sort of controlled landing at fairly high speed and altitude. SSTO is theoretically cheaper in to operate, but has a much more severe fuel fraction requirement.

17

Not necessarily. In order to launch anything, you have to have propellant of some sort. (This presumes we don’t invent a magical non-rocketry solution in the next ten or fifty years.) Right now this is generally based around hydrogen and/or oxygen, neither of which is easily available on the moon. Chemical processes can extract oxygen from the regolith, but they are extremely work-intensive and produce very small amounts. Needless to say, they aren’t on the development slate in the near future.

Hence, in order to launch something from the moon, you have to first get the propellant to the vessel — and the propellant originally comes from Earth. Clearly, this is quite wasteful: Put the future propellant in a tank, launch it from Earth, land it on the Moon, fuel up the second-stage vessel, and launch it from there. All the propellant you burn adjusting course and landing on the Moon is effectively wasted, since you could launch straight from Earth and proceed outward without a Moon rendezvous. Until there’s an efficient means of producing rocket propellant from the Moon itself, using the Moon as a staging base for deeper-system exploration makes no sense at all.

Mars is a different story. Robert Zubrin’s book The Case for Mars explains clearly how a variety of propellants can be manufactured from the atmosphere using simple chemical processing, requiring only electrical power (solar or nuclear) and a small amount of catalyst or basis material. In that case, it does make sense to send a chemical plant to Mars, land it, let it generate a massive amount of new propellant that you didn’t have to bring with you (i.e. that you didn’t have to lift off Earth), and then take advantage of the weaker Martian gravity to launch a larger mission.

Further, according to Lewis’s book, which I linked above, there should be large quantities of additional volatiles in comets and asteroids, some of the latter of which are just as easily reached as the Moon. These volatiles can be transformed into propellants using straightforward methods. The tiny amount of possible polar ice on the Moon, by contrast, cannot be so easily exploited.

I repeat my assertion from above: Compared to other available resources in the solar system, the Moon is a dead, useless rock. Eventually it may be possible to put a base on it, taking advantage of other resources and as-yet-unknown technologies, but it shouldn’t be a preliminary goal for anything else.

18

The majority of a craft’s fuel is expended during launch but the airless environment of the moon would let you use maglev tracks to bring a craft up to escape velocity along the surface of the planet eliminating the need for any kind of booster. As for propulsion in space, a nuclear powered craft can use a variety of substances as the working fluid to prodce thrust .

19

Isn’t one of the reasons that all of the repair work on the Hubble was done in orbit due to the fact that it is too heavy for the shuttle to land with it?

I’d put on a link but being in the KSA limits my surfing time.

20

Look up. Way up and I call Rusty.

Check my first post with a link to the return of the Hubble in 2012.