tater

3.22 is at least lighter than the Mk3 cockpit, though the latter would still have 15 m/s better impact tolerance, 25 kN*m better torque (about 0.5 tons to add that on), 350 more EC (0.015t) and 70 more mono propellant (which masses 0.28 or so). So the Mk3 cockpit is then 0.68 heavier but the excess stuff it has masses 0.795, and that's not accounting for impact tolerance (we can say that comes out in the wash vs the lower heat tolerance it has). So just to make the mk1-2 fair vs the mk3, it would then be 3.105, and that's assuming that with the same "stuff" they should be equal (and the mk3 is far larger, so that actually still seems goofy. Maybe better to add a couple tons to the mk3.

Even though I actually agree with the last choice, I might have voted that even if I didn't, because I found it pretty funny.

They'd only need the higher dry-weight tanks for the return trip, so you could assume half the propellant is used immediately for the trans-Mars injection burn, and the low/zero boil-off tanks only for the return trip propellant. You can also simply include extra propellant carried for boil-off (15%?) using better mass ratio tanks. Note that the DRA assumes LH2 for both types of rocket anyway, so the boil off issue is the same (though there is less with chemical, since part of the mass is O2. Bottom line is that NASA seems to think they are at least competitive with each other.

This is just 100% incorrect. I know people working on this, and they're not spending their own money, lol. http://www.nasa.gov/centers/marshall/news/news/releases/2014/ntrees.html

It's back to the original wording. Thanks! (more importantly, the original version is FUNNY)

I could not disagree more. They are in fact the only requirements for manned flight, anyway. For probes science is the purpose, but as a national program in a democratic society, both must secure funding.

To be fair, while I can get where that picture is taken on a trail literally from my back yard (there is 1 house sort of between me and the summit), it takes about 5 hours to get where the image was taken (runners do it far faster than I can), most of it rather steep (it's about 6.5 km over, and 1200m up from my house).

Yeah, there can certainly be possible savings, though equipment savings need to include refurbishment and testing costs. Aircraft are checked about every month of flight time (so every few months calendar time) in a check that takes just overnight. Every 1.5 years they get a check that might take a few weeks---the type of thing that might in fact be very short by the standards of Shuttle. If your launch pace is such that your ground crew is just "full time employed" busy 100% of the year, and the time to refurbish is low enough, then reuse starts showing real benefit. Again to use Shuttle as an example, a single orbiter cost ~1.7 billion, and over the entire program launches ended up averaging 1.5 billion each.

We have one of each, but nearly any dog is better than nearly any cat, IMO. People who are cat fans interpret non-social disinterest as intelligence. Dogs are social animals, and are considerably more intelligent than cats, and you can actually do something with your dog, like go for a walk in the back yard:

I use the Mk1-2 as well, but on actually long missions I also include multiple Hitchhikers, and a science lab. Of course in my current game Minmus is 45 days away, so I need habs even for that.

A simple solution (dunno if it is actually simple, lol) would be something that turned fairings into "petals" that instead of being blown off would hinge at the bottom and open like a clamshell. It could be a toggle on the fairing, no extra parts needed.

The Shuttle Orbiter cost about 4% of the total program cost, so the post-landing costs hugely exceeded the cost of a single vehicle. Note that for 60T to LEO, you'd need 3 Shuttle launches, so that's 4.5 billion. A slightly spiffed Delta 4 Heavy would do that in 2 at 1/4 the price. If FH costs are as claimed, it would take a single FH, plus a regular F9 launch, a ~29X savings. Even using the per launch figures for shuttle that ignore most of the actual costs, shuttle would still cost more. Any Shuttle V2 would need to be an order of magnitude cheaper to operate than the original to be even in the same ballpark.

Yeah, it's an interesting idea, but once you really look at the details it's not terribly sensible, even if it were possible. Even the lunar version doesn't work well, though the forces are much lower. The climbers would take a LONG time given the longer cable required to L1 or L2. Who wants a week-long elevator ride?

The masses of many such parts make no sense, frankly. Look at the Shuttle command/crew part. It's substantially better in every respect than the Mk1-2, and masses less. The part descriptions claim that lander cans are fragile... but they are not. The parts need to be altered to make sense. Less mass in some cases, or more or less capability. As was mentioned above, if LS was a thing, then you could give different standard values for mission duration based upon capsule type as well.

My vote and opinion are the same.

The point should not be to design a vehicle of a certain type, but to have a mission that requires a certain total mass be delivered wherever, then figure out what the best way to do that is. Say the mission is landing a habitat, rover, and crew lander on the Moon, and returning them to earth after a few months of work on the lunar surface. Then you figure out what the best way to do that is. If the goal is just LEO, what is that LEO goal? Sending crew to ISS, or payloads? The solutions are entirely different.

You need to demonstrate that reusability actually makes a meaningful cost difference. An Earth orbital nuclear ferry vehicle would presumably be reused as long as it had nuclear fuel via refueling the LH2 propellant. So it gets reused perhaps many times before it is retired. Retiring a NTR of course requires some thought. A normal craft would be deorbited, we'd not do that with an NTP design. Perhaps end of life is defined as a function of dv per full tank of propellant. When nuclear fuel degradation/ablation results in total dv below some value for the nominal craft, it is at "end of life." Then, perhaps we dock a probe to it instead of the cislunar vehicles it might usually carry, and send it off to never return. Not just a reuse, but a retask in this case.

A manned flyby mission seems pretty pointless to me. Manned spacefight is a stunt. It's a stunt I'm particularly fond of, but that doesn't change what it is. For the price/mass to Mars of such a mission we could send fabulous orbiters and landers, even sample return, instead. What that won't do is create excitement for space, I get that. The last section of the proposal talks about adding excitement via EVA, IMAX, etc. Sorry, it's not that exciting to see a stunning Mars shot that happens to have a spacesuit in the foreground. I think that adding "excitement" is a real thing for manned flight, since the main purpose is to generate interest, and a sense of adventure frankly. This is where Mars One actually has a fragment of a single good idea in their sea of nonsense. The whole "reality show" aspect is not as silly as it sounds. I have no desire to see the soap opera aspect of people thrown together for a few years, but the idea that there might be a way to make a popular program about such a mission that is on TV often is actually intriguing given the true goal of manned flight. Of course I don't think a flyby has the excitement level, honestly a lunar landing would be more spectacular in that sense. Land an enclosed rover capable of long drives, and a hab. Have them do stuff on the surface for a while, ideally someplace visually interesting.

Note that the cost for SLS per year is about the same as the cost of the Space Shuttle. For that expense we will get 1 launch per year vs 4.5 launches per year. Within the STS 4.5 launches per year we got service to ISS, which with SLS will be an additional expense (luckily far cheaper because of commercial crew).

The actual cost per kg for Shuttle (actual payload, not counting the Orbiter) was ~$60,000. (total cost of program over total carried payload mass) If the job of shuttle had just been to shuttle crew someplace, it would've looked more like Dream Chaser (which is a more sensible spaceplane design).

TWR matters for crewed missions. For unmanned missions, obviously Isp is king, TWR doesn't matter at all. SEP transit times (like all ion) to and from Mars are measured in years.

The shuttle loaded was ~90T-100T(max), it could carry only 25T. So 75% of the payload was "spaceplane." Because spaceplane. As a small, crew vehicle (Sierra Nevada) it can make sense assuming multiple possible landing sites worldwide for emergencies. As a giant pig of a thing like Shuttle... no. For HLVs that are reusable, some of the old VTVL ideas looked at decades ago might make more sense. That's assuming you have some use for an HLV in the first place.

A tiny % of people would care and be vocal in the US. The same people didn't like RTGs, either.

They are not all that big. The NTP group has a version that is about 1600kg, and they are pretty close to being able to test it as I understand it. Manned spaceflight is a stunt. It's a stunt that I think is awesome, but it's a stunt. Everything manned could be done better by robots science-wise, and that is only getting more true as capabilities improve in that area. The Space Race was about the Moon. Having done it, it instantly became routine. Manned missions need to be spectacular or no one cares. The vast majority of people have no idea what is currently happening in space exploration. A new station near the moon would maybe get some time on the news right away, then no one would care. That's the reason why funding dropped. That said, in constant dollars NASA has been remarkably constant since the end of Apollo in terms of funding.

A lunar station would need many resupply flights, and NASA can't really afford 1 SLS launch per year, much less several. NTP is still on the table for manned Mars, so like other propulsion candidates it deserves testing. I want to say the current design is only about 1600kg.