Back to the Future

[tomnackid]

Spec: I think you haven't been reading what NASA is saying very carefully. If we go with project Constellation we will have GREATER heavy lift cpability than we ever had with the shuttle. And since the Constellation architecture can put a lander at the lunar poles (Apollo could only land on the moon's equatorial regions) we can look for water and begin a REAL space infrastructure. A space station in LEO is useless for trips to Mars or the moon. There is nothing to be gained by using it as a staging point. The amount of energy needed to get to your final destination is still the same. Refueling on orbit is pointless if all the fuel has to be brought up from Earth in the first place. You only end up with more launches, greater expense and greater potential for accidents.

 

[tomnackid]

I think people who don't know much about orbital mechanics and physics look at the size of the shuttle and look at the size of the CEV/LM and say "Oh my god its so much smaller. We are taking a giant step back!" What they don't realize is that going to the moon--especially being able to land anywhere on the moon as opposed to a few equatorial sites as in Apollo days--is a LOT, LOT, LOT harder than just going to LEO. Probably harder than the jump between sub-orbital and fully orbital. People blithely say things like "LEO is half way to the moon." Well, turn it around "LEO is ONLY half way to the moon!" Think of a shuttle launch. Have you ever experienced (I say "experience" rather "seen") one in person? OK now double that to get a shuttle to the moon!<br /><br />People have the mistaken notion that once you are in Earth orbit you can kinda just gently push off and sort of drift to the moon. Being in orbit isn't like drifting on an ocean! It took a Saturn V with more thrust than the shuttle--a vehicle that put up a space station bigger than ISS in one shot!--to allow a tiny, two-man tin foil space ship to land in a few easy-to-get-to equatorial sites.

 

[spacefire]

it all depends on how you want to get to the moon.<br />A spaceborne ferry with a highly efficient ion thruster that would take astronauts and cargo from LEO to Lunar Orbit and back to LEO slowly but surely is the way to go in my opinion. <div class="Discussion_UserSignature"> <p>http://asteroid-invasion.blogspot.com</p><p>http://www.solvengineer.com/asteroid-invasion.html </p><p> </p> </div>

 

[specfiction]

Well, I started this thread to get an idea of what people interested in these things thought. Not what I was expecting, but.....<br /><br />Good luck guys..........<br /><br /> />Well, turn it around "LEO is ONLY half way to the moon!" <br /><br />Not quite, gravity falls off as 1/r**2. The energy required is NOT linear. And by the time you get to the gravitational half-way point, you start falling TOWARD the moon. The scientists that calculated the low-delta-vee orbit selected from a family of solutions to the equ's of motion (this is not a simple problem because the Sun plays a non-trivial role so it's a 3 not two body problem) that solution which minimizes the enery required to get to grav half-way. At that point, you're accelerated by the moon, and the delta-vee (KE budget required) was far less than escape velocity from the surface of the moon. Take your foot off the gas, and enjoy the ride. Don't do it with a software package, do it with paper and pencil.<br /><br />And I meant lift from LEO to the moon, not from Earth's surface. Also--shuttle safty--the failure modes of the two shuttle disasters were not something endemic to the shuttle. I don't think your capsule would have made it if SRB failed as they did for the Shuttle. Also, the insulation on the tank problem should have been delt with years ago. Because something is more complicated, it's not necessarily less safe, i.e. taking a trip down the freeway as opposed to a 747. There is no basis on which to compare the safety of capsule vs shuttle with the cases we have.

 

[tomnackid]

No, the Mass of the ISS could not be put up in one launch by a Saturn Five.<br />------------------------------------------------------------------------------------------<br /><br />OK, I exaggerated, but only slightly. With one launch a Saturn V put up a space station with a habital volume of 361 square meters. The ISS currently has a habital volume of 425 square meters after, what? about a dozen launches over eight years? The fact that the ISS is so much more massive for only 64 more square meters is another testement to the inefficiency of trying to do real work in space with only piddly little low and medium lift boosters. Don't get me wrong--I'm happy to see it being done at all and a appreciate the fact that building a heavy lift booster is a big waste of money if there is no use for it, but if oil had to be shipped from Saudi Arabia one barrel at a time on canoes we would be paying $300 a gallon for gasoline. The shuttle can do a lot, but it still does too little for what it costs.

 

[drwayne]

Keep in mind that Skylab has a LOT of empty, wasted space. It was, after all, simply a reconfgured, empty SIVB with some stuff around the edges and a who lot of nothing in places in the middle, so it is not exactly surprising that it would be lighter and bigger than ISS.<br /><br />Wayne <div class="Discussion_UserSignature"> <p>"1) Give no quarter; 2) Take no prisoners; 3) Sink everything."  Admiral Jackie Fisher</p> </div>

 

[drwayne]

And of course, what I just posted ignores the other neat what-if, the posited used of the second stage as an attached wet-lab experiment....<br /><br />Wayne <div class="Discussion_UserSignature"> <p>"1) Give no quarter; 2) Take no prisoners; 3) Sink everything."  Admiral Jackie Fisher</p> </div>

 

[josh_simonson]

>I don't think your capsule would have made it if SRB failed as they did for the Shuttle.<br /><br />Actually, the CEV would have been delivered in orbit without incident and the public wouldn't have known that a few jets of fire escaped the SRB. Even if the SRB exploded, the CEV will very likely save the astronauts by using the launch escape tower.<br /><br /> />Refueling on orbit is pointless if all the fuel has to be brought up from Earth in the first place. <br /><br />The reliability requirements for launching fuel that costs $1/lb is far less than that for a rocket launching explorationg hardware that costs $5000/lb. It can be launched on the cheapest available rocket, and used to inexpensively qualify new rockets. NASA will never fly their landers, ect, on anything but the most reliable (and most expensive) launchers available.<br /><br /><br />It is true that there are more efficient ways to the moon, but they all take longer. Reducing travel time through the radiation belts is critical for astronauts, and consumables consumed during the journey could be better utilized on the surface of the moon. Speed trumps efficiency in getting people to the moon, however I do question the wisdom of sending all the durable components: lander, fuel, consumables, equipment, via the same fast but inefficient route as the astronauts.

 

[baktothemoon]

Is it possible to create a kind of space ferry that would go back and forth between a spacedock and lunar orbit? It would just be a set of engines, habitation and control module, and a lander. You would refuel and resupply it in orbit, send up just the new lander, send it on it's way, and have the crew return using the spacedock's vehicle like the CXV, leaving as much as possible to be reused in orbit. Would this be practical in the long run, when we want to innovate on the CEV?

 

[specfiction]

>Even if the SRB exploded, the CEV will very likely save the astronauts by using the launch escape tower. <br /><br />I doubt it, but let's hope we never have to put that to the test.

 

[tomnackid]

The reliability requirements for launching fuel that costs $1/lb is far less than that for a rocket launching explorationg hardware that costs $5000/lb. It can be launched on the cheapest available rocket, and used to inexpensively qualify new rockets. NASA will never fly their landers, ect, on anything but the most reliable (and most expensive) launchers available. <br />------------------------------------------------------------------------------------------<br /><br />That's a good point. I was actually addressing the idea of a "shuttle only" scenario where multiple shuttle launches would be needed to stock a fuel depot, obviously a dangerous and wasteful scheme. Being able to launch fuel on cheap(er) non man rated boosters makes the whole concept more reasonable. Another plan (for farther down the road) would be to launch water to orbital depots. Abundant solar power in orbit can be used to electrolyze and liquify it for propellant. The advantage here is that you can avoid boil off by only turning on the electrolysis/liquefaction plant when a mission is coming up. The water can be added to little by little and stored for long periods of time or even used for other purposes like life support, radiation shielding and and reaction mass for future nuclear rockets.

 

[barrykirk]

And the Columbia type of accident is completely impossible with a CEV.<br /><br />First of all, the capsule is located entirely above the insulation, not below it. So, there is nothing above the capsule of TPS to fall on it.<br /><br />Also, the TPS on a capsule system is usually enclosed and protected until it's actually needed. Since TPS systems tend to be delicate, they are made of brittle ceramics after all. It's a good idea to put "packing material" around it until it's needed.

 

[barrykirk]

Well, if you've got a liqufication plant that is up to making all of the fuel liquid, then you already have the capability to keep all of the LOX and LH2 chilled and liquified.<br /><br />Why add the extra step of electrolysis which takes a substantial amount of energy and equipement.<br /><br />Also, depending on the time frame between launch and usage of the fuel and the insulation system. Liquification of the O2 and H2 could take a substantial amount of energy. Potentially a lot more energy than just keeping the liquid sent up as a liquid.

 

[josh_simonson]

>>Even if the SRB exploded, the CEV will very likely save the astronauts by using the launch escape tower. <br /><br /> />I doubt it, but let's hope we never have to put that to the test. <br /><br />The challenger astronauts survived until they hit the ocean - an escape system would almost certainly have saved their lives dispite the shuttle stack exploding.

 

[specfiction]

> The challenger astronauts survived until they hit the ocean <br /><br />How do you know that? Intuitively one would think the concussion alone would have resulted in massive internal injuries (that is if the crew cabin wasn't completely obliterated) Do you have a reference for this?<br />

 

[strandedonearth]

"How do you know that?"<br /><br />It's been noted in Mike Mullane's book "Riding Rockets," links here and here

 

[scottb50]

The main advantage you have in orbit is solar power, the safest and cheapest means of using it is water. <br /><br />I don't think electrolysis is an extra step it's the key. I also think its much easier to keep water as a liquid or as a solid for long term reserves. <br /><br />Hydrogen and Oxygen used for electrical power is recycled as water and re-used. Freed and contained Oxygen gas is used for life-support, Hydrogen gas is kept for fuel, with only simple shielding it should stay pretty cold anyway, so fairly low tech systems would be needed for day to day operation.<br /><br />Fuel cells and rockets, Hydrogen and Oxygen, the only time you need liquid is for propulsion and that could be a separate facility, docked to a Station. As long as you use identical Modules that snap together like Legos. <br /><br />The key is using solar power to electrolize water, why waste a free resource? In fact the same could be done here on Earth. Produce Hydrogen for your car in your garage. <div class="Discussion_UserSignature"> </div>

 

[edkyle98]

The type of solid motor failure to fear isn't the 51L failure, but the Titan SRM failures in 1986 and 1993. Both were debonding failures that caused massive explosions. The 1986 failure happened only eight seconds after liftoff and provided no measurable warning in the reviewed telemetry data. The most worrisome thing about that exposion is that it came years into the program, after more than 140 SRMs had performed perfectly. In the end, the Titan program suffered two solid booster failures out of the 246 solid motors flown. At least one of the failures would most likely not have been survivable. That's not 1 in 2,000, as claimed by ESAS.<br /><br /> - Ed Kyle

 

[specfiction]

Thanks for the reference, but there is no proof. This is just speculation. Just like speculation about foam not being able to puncture the shuttle skin, or the elasticity of O rings with temp. When were these switches changed--no one knows. Why didn't the floor fail under decompression--who knows--stresses are complex and dynamic, as they learned from the foam issue.

 

[vt_hokie]

I think it's more than mere speculation. It is a known fact that G forces after breakup were insufficient to incapacitate the crew.

 

[specfiction]

I'm not talking about G-forces--I'm talking about shear and concussive forces--the kind that destroy tanks in Iraq with a lot less explosive power than the tremendous amount of fuel in the shuttle's main tank.

 

[strandedonearth]

Challenger's ET didn't really explode. It was a rapid uncontrolled combustion. The concussion you're referring to usually requires a detonation, which is an entirely different animal.

 

[qso1]

There is a video about the Challenger accident that shows the crew cabin section appearing to separate due to the vehicle breakup. The cabin section appeared pretty much intact as best as can be told from looking at it at the distance it was from the camera recording it.<br /><br />I recall something as well about PEAPs being activated after the explosion and prior to water impact. <div class="Discussion_UserSignature"> <p><strong>My borrowed quote for the time being:</strong></p><p><em>There are three kinds of people in life. Those who make it happen, those who watch it happen...and those who do not know what happened.</em></p> </div>

 

[lampblack]

It's not just Mullane's book -- there are plenty of other sources, including a few that qualify as authoritative.<br /><br />Here's a link to one authoritative report that took about 15 seconds of vigorous googling to locate:<br /><br />http://history.nasa.gov/kerwin.html<br /> <div class="Discussion_UserSignature"> <font color="#0000ff"><strong>Just tell the truth and let the chips fall...</strong></font> </div>

 

[space_dreamer]

If only the crew cabin had a parachute!