sevenperforce

No, Dragon 2 has plenty of abort ability. It's just that SpaceX can freeze dev and run test flights pretty cheaply since they have a good launch cadence, so they chose the "validate by testing" approach rather than a much more time-consuming and expensive "validate by preparing a zillion reports on full-spectrum theoretical analyses".

Same answer as with DADT and the military in general. Homophobes are the problem, not the people they're afraid of.

This is the year 2018. Anyone who still discriminates on the basis of sexuality is really ridiculously foolish. Same-gender orientation is not a disease or a syndrome or a problem. It is observed in thousands of animal species. We simply happen to be the only species which has made it into a problem. At the risk of getting this thread locked: virtually all socially regressive policies stem from misogyny. We evolved in an agriculturally-driven, high-mortality society where it was economically advantageous to have strongly-structured gender roles. Industrialization led to a decline in the utility of these roles, and today there is no compelling reason to follow rigid gender roles, let alone mandate them. However, the affinity for those gender roles was deeply ingrained in the majority of societies, so deeply that the loss of these roles was seen as a threat to male identity. Toxic masculinity, in response, has systematically attacked anything which deviates from the male-led, heteronormative, gender essentialist patriarchal social model. Thus patriarchal misogyny is the root cause behind homophobia, transphobia, violence against women, and general gender inequality. On a lighter note: https://www.smbc-comics.com/?db=comics&id=2036#comic

I check https://spaceflightnow.com/launch-schedule/ almost daily...I saw that the Long March launch was delayed past March 12, but I never saw it come back up.

Sure thing. Fuel flow should be 5 lbs per second, but yes, then that is correct. Again, this works if your fuel flow is 10 lbs per second. You've gotta keep track of your units. People can report fuel flow in a lot of ways: pounds per second, kilograms per minute, tonnes per hour, gallons per mile, liters per hour...it all varies. If your fuel flow is 10 lbs per second and your thrust is 1000 lbs, then yeah, 100 seconds. Now we have no units at all. Here's a good example of where the units are tripping you up. If your fuel flow is 100,000 lbs per second and your thrust is 1000 lbs, then your Isp is actually 0.01 seconds. Oops! Well, if you are using lbs/sec for fuel flow and lbs for thrust, then yes, you get an Isp of 34.9 seconds. This is quite right; if you're dumping more than 50 pounds of fuel every second and getting less than 2,000 pounds of thrust, that's a really poor specific impulse indeed. Your propellant isn't even supersonic. Again, no units here. What am I looking at? You could be reporting fuel flow in mpg and reporting thrust in kN for all I know. Gotta get those units. Suppose you want to know the specific impulse of a Cessna propeller engine during cruise. Chances are that its thrust and fuel flow are not going to be given in pounds and pounds/sec, respectively. Only by using units properly will you be able to solve it. For that matter, most rocket engine thrust is given in kN and most fuel flow is given in kg/sec, so that's a whole separate conversion right there.

Shoot, somehow I missed the Long March launch on the 17th. I may go back and do that one....

I've worked for a while on trying to get a reusable TSTO with ground infrastructure, where your lander flies down and couples with the lower stage and is fueled for liftoff, and the lower stage flies back to the launch site like a Falcon 9.

Well, Orion's service module isn't done yet. By the time it is done, we'll be flying Commercial Crew with both Dragon 2 and Starliner. Send Orion to LEO on Falcon Heavy, then send crew to Orion on Starliner via Atlas V, then send a single International Docking Adapter into LEO on Falcon Heavy, and use Falcon Heavy's restart capability to perform an eyeballs-out TLI burn. You could also do it all with SpaceX, but that seems unfair and would run into cadence problems since SpaceX only has one pad for FH and it's the same pad for CC. You could send Orion to LEO on Delta IV Heavy, but that seems unnecessarily expensive.

Isp is how long the engine could fire if the weight of its propellant was equal to its thrust. It is also the average speed of the molecules coming out of an engine, divided by the gravity of Earth.

They can send Orion to the LOP-G without an SLS. Other than pure politics, I don't understand why they wouldn't.

With the new structural shells, I wonder if the reusable TSTO approach might work, using 5-meter parts, Wolfhounds up top, and a ton of Vectors beneath.

On a less political topic, Expedition 56 Soyuz docks with the ISS in about an hour, so here's that mission:

ISS Expedition 56 Docking This is a short one! That's all, folks!

What about: Spacecraft (a reusable manned vehicle which depends on an expendable/separate module for its propulsion) Spacetug (a reusable propulsion module for moving spacecraft around) Spaceship (a reusable manned vehicle with its own reusable onboard propulsion module) That's simple, right? So we've been in the age of spacecraft so far, and we are closing in on the age of spaceships.

If I had my druthers, I'd say to make high-Isp LFO engines run on an alternate fuel mixture. All engines currently run on the exact same mixture of fuel and oxidizer, but high-Isp engines like the RL-10 or J-2 use hydrogen, which is a richer fuel-oxidizer mixture. So the Wolfhound (well, really the Skiff) should do the same. It wouldn't make it impossible for newbies to use these engines, but they'd end up with leftover oxidizer if they weren't careful. It would give another way to use wing tanks in space without throwing an LV-N on. Doubt they'd ever do this, of course, but it would get at the complexities of hydrogen storage and excessive dry mass without having to add a whole new fuel type. I'd also love to see tripropellant engines that can burn LFO+monoprop at high thrust, lower Isp or switch to LFO only for lower thrust, higher Isp. On the subject of fuel and other consumable management, I would REALLY like to see a way to dump fuel. The best way I can think of to do this would be to add an "active cooling" part, which would consume a small amount of propellant (selectable in much the same way as you can select LF, LO, or mono on the convert-o-trons) in exchange for cooling. It could be set to simply dump propellant outright or to dump it in proportion to heat exposure. Same shape as some of the new MH structural pieces; layer them on the surface of your ship and you can use your whole ship as a heat shield.

Something that implies the notion of integrating an upper stage and a spaceship.

Rapiers are good enough on their own if you are only going to LKO. If you are going very, very far with few or no refueling stops, pick a nuke. The middle ground where a Wolfhound might be good is an SSTO with ISRU capability. That high Isp will get you out to Minmus to refuel but you still have better takeoff thrust on places like Duna and Tylo than you'd get with a nuke. The SPS was a biprop hypergolic, not a monoprop. Incidentally, the Puff was the highest-TWR vacuum engine smaller than the Rhino, until the Skiff came along. The J-2 was a gas-generator-cycle hydrolox engine, so it had a median isp of 421s, which is quite close to the 412s which I insist should have been on the Skiff rather than the Wolfhound. That should be the case for every engine. Well, heavy, low TWR, and good Isp as far as bipropellant engines go. Squad hasn't confirmed it, but there are code fragments which suggest a mistake and prerelease descriptions of the Wolfhound talk about its high TWR, I believe. The Apollo CSM SPS was originally intended to be used as the LM ascent engine, so its vacuum TWR needed to be high. I can think of plenty of situations where I needed high vacuum thrust and didn't care as much about ISP. The J-2 was used as a second and third stage in Apollo. Stage 3 of the Saturn V, powered by the J-2, provided the TLI burn; those BLEO burns are where you really want the highest isp. If you're actually going to go somewhere and use an engine to stop, high TWR and low dry mass is the way to go.

Anyone have any ideas on what might be achievable with new stock parts as far as Eve ascent vehicles are concerned? Any chance at a workable Eve SSTO?

Squad accidentally swapped the stats for the Skiff and the Wolfhound. The Skiff is the J-2 analogue, which is supposed to be heavy, with a low TWR but a ridiculously good isp. The Wolfhound is the Apollo CSM SPS analogue, which is supposed to be lighter, with a poor vacuum ISP but a ridiculously good TWR. They simply swapped the stats. It's a coding error.

I never did do a Jool-5 in any of the earlier threads, so a 1.4.1 version might be fun. Giving it a shot.

I don't think they ever said for sure, but it suggests five refuel flights. Probably about right.

I think a lot of the SSTO speculation w/r/t BFS came from this graphic: This states that for payloads up to about 15 tonnes, the BFS is carrying 8.5-9 km/s of dV fully fueled, which should in theory be enough to reach orbit, right? Trouble is, this graphic is about on-orbit refueling, which assumes the 375-second isp of the Raptor Vacuum engines. The first segment of the flight would need to use a much lower specific impulse. It would also need to deal with extremely high gravity drag due to low takeoff thrust.

Well, it's an SSTO, but it's not a reusable one, which defeats the purpose.

One thing to help you become more used to working with units and unit conversions: try messing around a little with the supercalculator at Wolfram Alpha (google it). It can do all the unit conversions automatically, but it will show its work so you can see what you end up with. An even trickier one: let's switch from Imperial to metric. Suppose your engine produces 9800 kN of thrust and burns 2 kg of propellant every second. What is the specific impulse?

Not to mention that the thruster symmetry would be thrown off by the mass of the engine you choose.