sevenperforce
-
Posts
8,925 -
Joined
-
Last visited
Content Type
Profiles
Forums
Developer Articles
KSP2 Release Notes
Bug Reports
Posts posted by sevenperforce
-
-
5 minutes ago, Darnok said:
Estimate, but that is not equal to measure
All measurements involve a margin of uncertainty. Uncertainty in measurement does not an estimation make.
-
2 minutes ago, pincushionman said:20 minutes ago, Darnok said:
I have few questions about LHC...
How they measure mass of particles that are on move during experiment?
Does their hardware and software is able to detect particles moving faster than light?
Math. Knowing the properties of the electomagnetic fields in the test chamber, you can derive particle masses by studying the paths those particles are observed to follow. Sort of like how if you can obseve the orbits of a planet and its moon, you can determine both their masses.
And not faster than the speed of light. Close to it, though. But making it work is a serious engineering challenge.
I would point out that if some of the particles did exceed lightspeed, the LHC detectors would absolutely be able to detect it.
-
19 minutes ago, Bill Phil said:
Newton was wrong about the aether, and wrong about space being static, an after that he was wrong on certain scales of gravity.
But he was not wrong in ways that significantly affected the predictive power of his theories on scales that could be measured during his era.
-
7 hours ago, CatastrophicFailure said:
Hmm. Y'know, I think landing on the moon is gonna take a teensy bit more than that...
Crasher stage. Falcon Heavy boosts across EML-1 or EML-2 onto a collision course with the moon, then restarts and burns retrograde to kill 98% of velocity. The Dragon separates, loses the trunk, and finishes the retrograde burn with a hover landing.
-
2 hours ago, CatastrophicFailure said:
Are there any stats on the D2s delta v?
Anywhere from 380 m/s fully loaded up to 540 m/s empty. That's at SL, though; vacuum thrust and specific impulse will be a bit higher.
-
1 hour ago, fredinno said:
SpaceX doesn't seem to consider it too seriously though, NASA (literally the only potential customer for such a lunar lander) hasn't gotten any proposal from them for a Dragon V2 lander. The 'journey to Mars' hasn't stopped Boeing from props in a lander for example.
Not to mention Dragon V2 is probably too small- NASA wants a 4 person, 15 day lunar lander. Altair back in the constellation days had about 1.5x as much pressurised volume, just for that purpose.
Also, v2 landed has no regenerative power supply and unpressurised cargo bay to host experiments.
It's probably possible to use it as a lunar lander.
But it's doubtful that would ever happen. It's not like SpaceX wants to go to the moon.
I don't have the link in front of me but I am 90% sure I remember Elon saying, "We will be able to go to the moon, so why not? It's on the way to Mars, after all, so it wouldn't make sense not to go there too." Obviously the Word of Elon is not always directly representative of legitimate plans, but it means they are at least talking about it.
And like I said, the uprated Falcon Heavy has enough dV to drop an unmodified Dragon V2 on the lunar surface. No big deal.
-
17 minutes ago, Rakaydos said:
what if they only crossfed the heavy Kerosene, giving the core a large enough oxygen tank for the whole burn, but burning kerosene from the boosters until separation?
you wouldnt get the full effect of crossfeed as youre still limited by the O2 you can cram in, but it simplifies the plumbing, and your kerosene (the part you didnt take out for more oxidiser) is full at separation.
LOX is denser than kerosene.
-
Here's another version, with the ducts on the side and SuperDracos inside the augmentation duct for launch augmentation and supersonic flow control. They fold down with the landing "legs" during landing for biaxial propulsion. Haven't done the math yet though. Crew variant shown.
-
8 minutes ago, wumpus said:
You're sure enough about the dry weight to calculate the cargo to 10kg? In a rocket with 90 tons of fuel? How many struts did you use?
Too many sig figs, I know.
-
I'm endlessly frustrated by depictions of the moon that show the curve while you're standing on it. Or show it only a few 1000 km from Earth.
-
2 minutes ago, todofwar said:
https://en.wikipedia.org/wiki/Liquid_fly-back_booster
So, instead of having the center craft be a rocket like they had in that system, you make the center craft another spaceplane that will serve as your reusable orbiter. I do it all the time in KSP, so it must work
. IRL it failed because you ended up needing so much mass in wings, wheels, and engines, all of which had to survive launch. But your system would allow these boosters to be simple lifting bodies and glide back.
As for landing on the fins, wouldn't that necessitate a powered descent?
Right, I know about the LFBB design; I'm just trying to figure out your implementation.
Yeah, powered descent, but powered by the lift fan.
-
11 minutes ago, todofwar said:
Wouldn't belly to belly be a biamese launch? Again, I'm talking about using this as a fly back booster. I guess you couldn't make the center craft symmetric in my idea anyway, so a biamese tsto or have an angle of attack such that your thrust vector is through your center of mass despite having only engines on one side a la shuttle would be the best way.
More generally, what about landing this as a sea plane? Would the savings in wheels be negated by the increased structural requirements?
Yeah, belly-to-belly is biamese. I guess I'm not sure what you're trying to get at with a flyback booster.
No wheels in the single-engine second render; it lands on the lift fans.
-
47 minutes ago, cantab said:
The pointy one is a cool render, but I doubt it's doable with current materials. You're expecting an entire SSTO to weigh not much more than the Dragon capsule alone.
Well, it's not actually a lot bigger than a Dragon capsule. Smaller cross-section, actually. This design was essentially a thought experiment to see how small an SSTO could be.
The Falcon 9 upper stage is about the same size but is significantly lower in dry mass.
30 minutes ago, todofwar said:For symmetry mostly. I don't think you'd want to strap something to the front of a ship like that. You could have two and do a shuttle like launch I suppose.
Symmetry would demand a biamese launch. The ship is smaller on the belly than on the back so it can act as a lifting body; mating belly-to-belly is really the only way to go.
-
4 minutes ago, todofwar said:
Yeah, my thinking is basically have three of these, except the one in the middle would have a nice big cargo bay. All three are reusable lifting bodies.
Why not just two?
-
9 minutes ago, MatterBeam said:
What's the payload to orbit? How scalable is the design?
3,790 kg to orbit. You can scale it up for a bit pretty easily -- double with two Merlin 1Ds, triple with three, and so forth -- and gain a little bit in payload fraction due to the square-cube law making the dry mass lower, but your AAR gains will start to suffer as you pack more engines in. You'll also run into more structural issues; this is a low-drag design but the aerodynamic stresses are still pretty high, so a larger version will have to deal with higher moments of torque in flight.
My goal was really to design the smallest possible SSTO rather than a large one. Obviously a larger SSTO will have a better mass fraction, but a larger SSTO will also have greater turnaround time and higher reuse costs.
Toying with the idea of SuperDraco-assisted takeoff and landing to replace the lift fan...depends on whether I can get the duct geometry to work.
-
If Elon says they would remove the heat shield and add propellant to Dragon V2 in order to do moon landings, then apparently there is a fair probability that doing so is cheaper than designing an entirely new lander from scratch.
-
On 5/2/2016 at 9:52 AM, todofwar said:
I was saying use this as a liquid flyback booster instead of an SSTO, I seem to have communicated that poorly.
Oh, I see. Booster for what, though? A separate reusable stage?
Did some more calculations with the new uprated Merlin 1D, and it looks like we could make orbit on a single engine, using VTVL with a horizontal-attitude landing on lift fans; the lift fans serve double duty to supercharge the inlet duct during liftoff. Here's a mockup:
GLOW is 99.5 tonnes, total fuel is 90 tonnes. 3,790 kg of payload. Assuming 50% increase to engine mass to account for the fixed ducting. Assuming a tankage/structure/avionics mass of 3.7 tonnes with 1,280 kg reserved for TPS, landing legs actuators, landing fuel reserve (for the gas generator, not for the actual engine), structural modifications, and the lift fans.
Not quite sure where to put the crew cabin. I suppose I could have done it with the AAR ducts on the sides rather than the top and bottom, allowing me to put the crew cabin right in front of the engine.
-
15 hours ago, Mitchz95 said:
Yeah, that's the one. One of the meteors is a fragment of a brown dwarf (which the writers apparently mixed up with a neutron star) that gets lodged in the moon, and they have to "magnetize" the moon's core to eject it into the sun before the brown dwarf's gravity causes Earth and the moon to collide. They accomplish this using an Apollo lander and a bunch of other hardware they apparently designed and built in eighteen days. Yeah, it's bad.
WAT
**reads wiki**
WAAAT
That is...wronger than not even not even wrong. I don't...can't even.
A CHUNK OF BROWN DWARF HEAVIER THAN EARTH IS IN THE MOON. AND THE MOON CONTINUES TO ORBIT EARTH. BUT IT MAKES OBJECTS LEVITATE AT RANDOM.
wat
"The Impact mini-series received little comment from the scientific community due to its lack of realism, incorrect use of terminology, and basic misunderstanding of the law of gravity."
13 hours ago, Bill Phil said:15 hours ago, cubinator said:Huh? What science? I only hear technobabble.
Yeah. That's called "science."
That sound you hear is neurons committing suicide.
-
It would be easy to say that science can still be considered science if it is testable in theory, even if it can't immediately be tested. That would cover most cases. Might not get at the heart of the issue, though.
Perhaps a more holistic approach would be to say that if you are really doing science, you'll be looking for ways to test it already, merely by working through the process. Science is a process of learning and refinement and investigation with some pretty telltale markers. So I suppose that even if a particular line of investigation defies attempts at experimental design, it can still conceivably constitute science based on the process being implemented. Perhaps you already have all the data that could possibly ever be collected and you can only attempt to describe what you already have, with no opportunity to ever collect a new dataset. You can still conduct science with that. It's probably just going to be a bit more challenging.
The important thing, I think, is to not lose sight of the point where science stops being science and becomes pseudoscience. For example, there was a time when the theory of universal common decent by evolution was still in its infancy and alternative theories could have still been viable. But that time is long passed. To persist in advancing something like creationism is not science, no matter how thick a veneer of sciencey investigative activities you layer onto it. The same is true for the vaccine-autism connection, for homeopathy, and for a thousand other foolish notions which could theoretically have begun with scientific intent but which now persist doggedly in their illegitimacy.
-
I've used this as a plot device in fiction before.
The problem is that if you travel to, say, Alpha Centauri at a high enough fraction of c to reach it in one week from your perspective, then time-travel back five years less one week, you could then turn around and intercept yourself before you arrived. Which is a problem. For most people anyway.
In my fictional 'verse I had the FTL drive travel back in time as it went forward in space, so that the time dilation was counteracted in real time. Which introduces its own set of challenges....
-
14 minutes ago, cubinator said:
The asteroid itself wasn't visible, but the impact was. In reality, it would be visible and it would be almost the same size as the moon.
Bahahahahahaha
At the orbit of the moon, an object too small to see couldn't be more than a few km across at the very most. So even if it were made of pure osmium, it would have to be moving at relativistic speeds to make any noticeable change to the moon's orbit. Which would give it enough energy to punch straight through the moon and scatter the whole thing into fragments.
-
48 minutes ago, cubinator said:
If it was a large one like Titan, it could stop it's orbital velocity entirely. Then you just need to shoot one of the Galilean moons out of your giant celestial potato cannon at the right time to circularize it's orbit. Unfortunately, when you impact two large moons you don't get one moon, you get a cloud of space lava, which is not a fun thing to be directly under.
Amusingly, decreasing the size of the impactor actually results in a greater release of energy and even more space lava.
Particularly space lava bombarding Earth, at velocities far in excess of solar escape velocity. Mostly on the facing side (or whatever side happened to be unlucky enough to face the moon at the time the bombardment first reaches LEO) but all over to some degree, because a lot of it is going to be bent into collision or aerobrake into an eccentric orbit.
Actually at some point the lunar gravitational binding energy is going to come into play. Altering the orbit by 5% with the aforementioned 71 km/s, twice-the-mass-of-Mimas body would be 2e29 J, 60% more than the binding energy of the moon. Great.
Did they say approximately how large this "asteroid" was? Like, was it visible with the naked eye?
-
33 minutes ago, insert_name said:
it probably stopped getting bigger because it reached perigee and started going back up, if the asteroid hits the moon at the right angle at the right time it could easily bring down the perigee
If by "asteroid" you mean "one of Saturn's moons" and if by "hits" you mean "impacts at solar escape velocity" and if by "bring down" you mean "decrease by 5%" then sure.
-
26 minutes ago, cubinator said:
I think I read a book like that once. The plot started with a huge "asteroid" which would impact the Moon and be visible on Earth. Unfortunately, scientists "miscalculated" the mass of the "asteroid" and the Moon falls towards Earth. Everyone sees it getting bigger and panics, but it stops just before hitting Earth. Then it causes a bunch of catastrophic tidal effects like flooding coastal cities, and volcanoes that create a worldwide ash cloud that causes a global winter.
IT
STOPS
I think there was a series, but the science was so cringe-worthy that I stopped. Conservation of momentum schmonservation of momentum.
Hmm.
I don't suppose it would "stop" but a sufficiently dense mass hitting it at precisely the right point could drain enough orbital energy to lower the perigee significantly. You'd have a moon that got significantly larger and smaller throughout the (now shorter) month. You'd need another asteroid collision to "circularize" in the lower orbit if you wanted it to stay at that perigee all the time.
And everyone would be dead. First from the rain of meteor debris that would splatter the Earth like so many raindrops, and second from the extreme tides that would cover even the highest mountains, and third from the...well everyone is dead by this point so why go on?
Did it ever suggest how much closer to Earth the moon was?
Presuming a maximum solar-system-object impact velocity of roughly 71 km/s, dropping the orbital momentum of the moon by a mere 5% would require an impactor with a mass of 5.2e19 kg, roughly 200,000 times the mass of Halley's comet or about twice the mass of Mimas.
Red Dragon confirmed!!
in Science & Spaceflight
Posted
The longest (read: most fuel-efficient) route to low lunar orbit is a lunar swingby through EML-2, which takes 6 days. LOX boil-off is 0.2% per day, so you lose 1.2% of your LOX on that six-day transfer. Shouldn't have any trouble reserving enough dV for the crasher-stage landing. However, different trajectories do require a different number of restarts, so depending on the fuel cost of each restart it might be more fuel-conservative to use a faster, more expensive trajectory that requires only one restart for correction/injection.
I'm working on a pet project to find a viable route for a manned lunar landing using two FHE, a single unmodified DV2, and a moderately modified White Dragon for the lunar landing and ascent vehicle. I think I can get a crew of 3...maybe 4 if the math ends up being agreeable enough.