Jump to content

RCgothic

Members
  • Posts

    2,916
  • Joined

  • Last visited

Everything posted by RCgothic

  1. Be aware that manufacturing solid rocket motors in the UK is illegal: "Under the conditions of the 1875 Explosives Act, the 1883 Amendment, and later Prevention of Terrorism acts, it is an offence to manufacture your own solid fuel rocket motors, since these are classed as an explosive." I don't know what the relevant US laws are. It's something to be aware of depending on where you're based.
  2. Wow, the Galactica's a beast! Following on from my previous attempt, I installed a docking port and an RCS system and attempted to hit some of the bonus achievements. Payload up, 1 xenon-electric probe sat: Launched: Docked to a space station: Ore probe for downlift (forgot to fill it - shh!) Ore probe docked: And landed at KSC for probe unloading: Full album: http://imgur.com/a/XyYWU The hitches were that I stuck the xenon-electric thruster on backwards, and forgetting to actually put any ore in my ore probe.
  3. Yes, that looks like a normal F1 concept to me?
  4. New entry for 1.2 before I reinstall FAR. Before Take Off: Full throttle: Take off Rocket mode engaged! Apoapsis established: Orbit acheived! Stayed up a few hours waiting for KSC Dawn: Beauty 1: Beauty 2: Reentry periapsis and fuel remaining: Coming in Hot: Coming in early: Final approach: Landed with 1000 units of fuel still onboard:
  5. I followed up the above post with a calc on the half-period of an orbit with apoapsis at oort and periapsis at sol. 2 million years. So that idea's out. Although imparting an initial velocity would massively reduce that, but the maths is escaping me at the moment.
  6. Much easier would be asteroid redirection. Eg Oort cloud objects don't orbit very fast - 3m/s ish. You could divert a very large object into the inner solar system and it would arrive at earth at approx 42km/s or even faster if it were slingshotted around Jupiter. Somebody check my maths on this, but a high performance ion thruster (exhaust velocity 5km/s) could halt the oort orbital velocity of a 10,000 ton object with 600kg of propellant. The sun would them do almost all the rest. If that could be brought in at 60km/s the kinetic yield would be 4 megatons, or 2 megatons without a slingshot. The drawback would be a painfully long deployment time, but if you brought in many objects periodically on a near miss trajectory they could be altered to strike the earth at much shorter notice. With the very small amounts of DV required and resource extraction, one spacecraft could potentially redirect many such objects. But considering the launch costs for getting out there in the first place, it would be far cheaper to just nuke it. Unless you were already in an oort civilisation.
  7. And that's just an argument for multiple colonies, not zero. Mars would actually be much less vulnerable to global catastrophe too. With power mainly from nuclear and enclosed habitats, there's not much an impact on the other side of the planet could do compared to a similar atmosphere-disturbing event on Earth.
  8. Earth could be rendered uninhabitable by any number of scenarios. In that situation humanity is saved by an offworld colony. Also, in a sufficiently large disaster, even with a 1-5% survival rate civilization on Earth would collapse. With all the easily extracted resources already extracted, there's no reason to assume advanced civilization could emerge again second time. An advanced society based on Mars could bootstrap us back into the space age. There are plenty of reasons why getting off this planet permanently is good for humanity's long term prospects.
  9. Centre of mass is the average position of all the masses in a body. It is always fixed unless you add/remove mass or allow those masses to move around with respect to one another. If the resultant force of all applied forces acts through the centre of mass the body will translate without rotation. Any resultant moment will cause the body to rotate about its CoM without translating unless there is also resultant force. Centre of Gravity is the average position of every mass weighted by the gravity field at the position of that mass. It is a concept that makes visualising resultant forces more easy by allowing a single bulk force to be applied at the CoG but it can be misleading. For instance, considering Gravity as applied to the CoG of an airliner will help you find the pitching moment, but it won't remind you that the weight of the wings still need to be supported back to the fuselage. In a uniform gravity field, CoM and CoG occupy identical positions. For shallow gravity fields (I.e. Earth's), the positional difference is usually negligible except for ridiculously precision applications or ridiculously large objects.
  10. Sure they will, compared to other Martians. It might not be rich by Earth standards, but that's a pretty irrelevant comparison when the nearest Earthling is an 80 day flight away. Who wouldn't want to have corporate/political/fiscal power over a significant fraction of a planet? When the colony is established it will have its own economy. Being top dog in that economy would be like being a big fish in a small pool, compared to being an irrelevant fish in an ocean. That's going to be an attractive investment to a certain type of person. It's trading Earth funds for Martian power.
  11. I would assume that the Spaceship is capable of blasting free of the booster if necessary. If there's a problem with the Spaceship itself there's probably nothing that can be done. You can't just ejector-seat 100 people, and the Spaceship doesn't contain parachutes because it lands propulsively. Any cabin detatchment would have jettisoned its means of landing safely. But at least its launch abort scenarios are likely to be more benign than the shuttle's.
  12. Also, whoever first gets a foot in the door on Mars is likely to end up being the richest person/company on Mars. That's not nothing, even if the investment doesn't return to Earth or the RoI is small by Earth standards.
  13. New Shepherd attains an apogee of what, 100km? That's 0.981MJ/kg specific energy to the payload at apogee, conservatively. Falcon 9 first stage separates at about the same height, but can be doing 8000km/h +. That's an additional 2.46MJ/kg specific energy, or 3.35MJ/kg total. So before even involving the difficulties of piloting to a remote landing site, energetically what SpaceX does is nearly 3.5 times harder. Ok, Blue Origin did it first. But it's like the difference between landing Freedom 7 and landing Apollo 8.
  14. The F1-B engine is part of one proposal for advanced kerolox boosters to replace the shuttle derived ones as part of... Block 2? There are other options as well.
  15. Except that when you hold your breath and that 14% residual volume expands 4x the pressure drops correspondingly to 1/4, which would then actively extract oxygen from your blood. Being a small volume, the partial pressures will equalise some, so it's not quite as bad as 3/4 of a total vacuum. But 60-75% as bad is still pretty bad.
  16. I misremembered. I found the Google report, it's actually 17 seconds to respond to alerts and take back control. To actually react intelligently is another matter entirely. The situation you describe sounds like a pilot with hands on anticipating the situation that they need to rectify. In an emergency whilst operating on automatic the manual operator may have been reading, snoozing, facing the wrong direction. They aren't going to have the situational awareness of an alert pilot anticipating that they're going to have Also 'often completed in less than five seconds' is not 'everyone completes in less than five seconds'.
  17. Studies have shown it takes at least 12 seconds for a passenger to become adequately aware and in control in an emergency situation. Vehicle accidents happen so quickly that a manual override is totally useless. Yes, a system failure will lead to deaths. So you design a system that cannot fail catastrophically or with redundant back ups as much as possible. Automated vehicles will be orders of magnitude safer than manually operated ones. They don't get tired. They don't get distracted. They can look in every direction at once and see through light obstructions. They can talk to each other in order to better manage traffic and reduce possibility of collision. They will never get reckless or exceed the safe operating envelope. They cannot be medically incapacitated at the controls. They can have back ups for failed components. Humans were not designed for piloting vehicles. To suggest we're somehow superior to a purpose designed system is human chauvinism.
  18. Four engines. In the event of failure, two have sufficient power to stay aloft at max throttle, with the third providing trim for offset load. Obstacles and noise issues can be mostly avoided by a minimum height for non-vertical flight. Power lines in the UK aren't higher than 55m And anything taller than that would be both mapped (regulatory requirement) and detectable by the onboard collision avoidance system. Drones won't move as fast as aircraft, so the 200m mandatory minimum distance can probably be reduced. They'll also talk to each other to keep out of each other's way ideally.
  19. Yet on screen evidence suggests it's safe enough to walk around in only a mask. That's either a goof or an indication that H2S is on the order of ppm. LCL0 is on the order of 600ppm (inhaled?) for 30 mins, or 800ppm for 5min. Max US regulatory exposure is 20ppm (inhaled?). Lung surface area is approx 25 times greater than skin surface area (conservatively). It's also thinner and more readily diffused across. It therefore stands to reason that a lethal inhaled concentration of ~800ppm atmospheric equates to less than the regulatory equivalent skin dose. Put another way, the concentration required to kill you if you're wearing a mask by diffusing through skin would be of the order 20,000ppm or 0.02%. If Pandora's atmosphere is around 800ppm it should be safe to wear a mask and lethal in approximately the observed time frame without one. H2S is detectable at around 10ppb, so the smell of Pandora's atmosphere would be very, very strong.
  20. Sorta. If you're in a plane or spaceship that depressurises it's a bad idea to hold your breath because the pressure in your lungs will dangerously over-inflate them without external pressure on your chest. And then once you've breathed out the zero/near zero partial pressure of oxygen in your lungs causes the oxygen in your blood to diffuse out down the pressure gradient and you've got 30s. It's actually a similar situation if you find yourself in an atmosphere at sea level composed of pure nitrogen, carbon dioxide, or other composition with zero oxygen concentration. Breathing normally, that's still a zero partial pressure of oxygen which will suck the oxygen out of your blood by diffusion. 30s. Unless you hold your breath. If you don't breath in the oxygen free atmosphere, then the air in your lungs maintains partial gas pressures not that different to that in your blood. It'll slowly deplete oxygen and accumulate CO2, but the driver is the gas concentrations in the blood. There's no sudden loss of partial pressure to suck the gasses out and you can last a lot longer. So then you have Pandora. That's not a lack of oxygen or a lack of atmosphere. That's toxic gasses. If you breath normally, there's suddenly a partial pressure of toxins in your lungs that force their way into your bloodstream. But if you hold your breath, it's pretty much equivalent to holding your breath normally. The colonel wasn't in immediate danger unless he took a breath. No toxins in the lungs means none in the bloodstream.
  21. Nasa is doing well in the probe department. NASA is not doing well in the manned spaceflight department. Even if SLS/Orion avoids cancellation they have far too few missions planned. This area currently feels anaemic and weak. SpaceX has done a fine job recovering 4 boosters and have designed a damn fine kerolox engine in the Merlin 1D.
  22. The Falcon 9.1 FT is the coolest rocket because it uses super-cryogenic propellants.
  23. Binary planets are fine. They'll gradually spiral out until they're both tidally locked, but can be otherwise stable. The Earth and Moon probably isn't too far off being a binary. The moon isn't that much smaller than Mercury after all, and is actually influenced more strongly by the sun than by earth (Uniquely amongst moons and their parent planet). Another definition is that the centre of mass of a binary should lie outside both bodies, which it will in the earth-moon system in another few hundred million years. One issue with that definition is that unless the two bodies are exceptionally close in mass it generally leads to very distantly orbiting binaries. You're unlikely to find a third significant mass orbiting such a pair, though you could get an insignificant mass orbiting just one of the parent bodies, or very far out around both. Another interesting factoid is that the barycenter of Jupiter/Sun is actually outside the sun. Does that make the solar system a binary star/planet? Jupiter doesn't meet any of the criteria to even be considered a brown dwarf. Food for thought.
  24. I know this was a bad mission, but can we stop killing Orion missions please? The launch rate is awful enough as is! We need to fund things properly! Permanent moon base by 2025! Boots on Mars by 2035! Let's get some proper infrastructure up there! I cannot believe how hard people are making this. In 1960 we hadn't even put a man in space. Nine years later, moon! And 50 years later we can barely fund four manned missions over a decade? Come on people! This is so frustrating.
  25. I that case the payload is essentially negligible. Plucking numbers essentially out of the air: Spacecraft: Let's say guidance and telemetry can be handled by a smartphone. ~100g. There's a minimum volume of monopropellants that would be effective for control. Call it a half-litre plus tankage, maybe 400g. So minimum 0.5kg for the spacecraft. 2nd stage: Payload is 0.5kg, plus engine, plus tank. Assume it does most of the work, 6.8km/s orbital insertion. Atmosphere negligible. Smallest H2/LOX engine I could find is India's CE-20, but it weighs 590kg and has 45kN thrust. ISPvac of 443. A bit overpowered... Stage would weigh about 4.6mt with 3.6mt of fuel and 370kg of tanks at a 10:1 tankage ratio (cryogenic). An Airbus Aestus based second stage (N2O4/MMH, 111kg, 30kN, 325 ISPvac) would weigh about 1.6mt, with 1.4mt of fuel and 70kg tanks (20:1 non-cryogenic). TWR a bit ridiculous at 2 to 17, but I assume our postage stamp doesn't care much about that. So let's go with the Aestus. Burn time is 144s, which sounds not ridiculous. The first stage needs to boost this to 100km and 1km/s. Diameter (engine) is 1.31m. Nitrogen Tetroxide is mixed at a 1:9 ratio with hydrazine. The average density is 0.93g/cm3 and required volume 1.46m3. That would fit in a slightly elongated spherical tank (~15 cm cylindrical section) with internal bulkhead, which would be hilariously stubby, but then we already know this is massively over-engined. Engine is 2.2m long, stage approx 1.3m dia and 4m long including spacecraft as a cone. 1st Stage: Payload is second stage (1.55mt) to 100km altitude and 1000m/s at that point. Needs to fight atmosphere. Gravity approximated as 9.8 all the way to orbit. If atmosphere is negligible above 10km, then you'd need to be travelling 1660m/s as you passed 10km assuming a coast from there to orbit. Climb to 10km is a bit of a guess. You need at least 442m/s, plus extra to fight gravity, plus extra to fight air resistance. Assuming 2G acceleration, let's call gravity losses 220m/s and probably the same again for air losses. Earth's rotation at the equator gets us 465m/s. That's 2.1km/s. Let's call it 2.5km/s for margin. The smallest 1st stage engine I can find is our friend Space X's Merlin 1D FT. RP/LOX, 756kN, 470kg, ISPsl 282, can deep throttle. It needs approx 3.2t of fuel to get the job done. 160kg tankage. TWR a truly ridiculous 4.5 to 14 even at 40% throttle. Burn time 30s. The Merlin 1D is actually smaller diameter than the Aestus, so we keep our diameter at 1.3m. Density of RP/LOX is approx 1g/cm3. 3.2m3 required. That's a hemi-ended cylinder approx 2.8m long for tanks. Engine is 2.9m. First stage approx 5.7m tall. 1st stage mass: 5.4t. Total craft mass: 6.9t. Total craft size: 1.3m diameter by 10m tall. These are just my crude back of the envelope scopings dependent on what's available engine-wise according to Wikipedia. I'm sure someone else could come up with something better.
×
×
  • Create New...