56

A big difference is that you wouldn't need to leave someone in lunar orbit. We now have experience and confidence in the remote operation of an uncrewed vehicle. So you could have a crew of two instead of three. Or perhaps a crew of three to the surface with a larger LM. Overall, there would be much more automation, especially for the landing process, ...


48

The short answer is it would cost a lot of money. In order to get a 1G force, you'd either need something really big, or rotating very fast. For example, the reference design for the space colonies I'm working on calls for a structure with a 900 meter radius rotating once a minute. For something the size of the ISS, it would have to be rotating much ...


33

This mission study came up with a 900 kg nuclear-electric-propulsion spacecraft launched on an Ariane V with a C3 of 100 and a Jupiter gravity assist along the way. 1.05 kW electrical power at Pluto from RTGs is required. That would be four "classic" NASA RTGs, or about nine MMRTGs. It has a 20 kg science payload. (New Horizons has ~30 kg of instruments, ...


33

I do not think your assertion that "other rockets were just as capable of performing the task at that time" is correct at all. I'd love to hear your counterexamples, if you have any. Perhaps you are referring simply to their payload-to-LEO capability? If so, that is only the tip of the iceberg. No other vehicle at the time provided all the elements of EVA ...


32

The long distance to the Sun mandates long exposure times. The New Horizons spacecraft needs to be relatively stable and its pointing accurate throughout these long exposure times. New Horizons does not have a scan platform. The cameras and other science instruments are fixed with respect to the vehicle. The satellite has to turn as a whole to keep the its ...


31

This was one of the questions just now during the Rosetta press briefing. This video was shown during the presentation: The triangular trajectory are hyperbolic orbits with respect to the comet and they'll (also, among other tasks also mentioned in the image you're attaching) serve to establish its mass. In essence ...


29

Launching and assembling the ISS in its current design could not have been accomplished without the STS (Shuttle system), but that is largely because the ISS was designed with the STS in mind as its launch vehicle. The ISS could be designed to be assembled in orbit using a large number of spacewalks because designers knew they would have the shuttle ...


28

Space is basically a vacuum, so there's no air resistance. A probe that's been launched will travel at the same speed indefinitely. Because New Horizons is moving away from the Sun, it loses some speed to overcome the Sun's gravity. New Horizons was launched on the fastest rocket they could get. Then it used a gravity assist from Jupiter to gain some more ...


26

In order to use the direct ascent method of landing on the moon, which is where the entire vehicle descends and leaves the moon, you would need a rocket an order of magnitude bigger than the Saturn V, not just a bit bigger. Here's an early comparison NASA made back before they decided to use Lunar Orbit Rendezvous: The C1 became the Saturn I, the C-5 ...


26

The uncrewed Surveyor probes landed on the moon before Apollo did. They provided visual images of the landscape and pictures of soil samples that were dug up robotically. All the visual indications were that the terrain was fairly firm: Surveyors also took pictures of their own footpads to see how deep they went into the soil: The ground pressure of the ...


25

Dawn has several mission objectives, including to continue testing the Ion Thruster. But why Ceres? Ceres and Vesta were chosen, because they have contrasting content, one icy and one rocky. Also, they are among the protoplanets that remain intact since formation, which (hopefully) leads to a better understanding of the formation of our solar system, ...


22

While many missions have been able to continue beyond their design lifetimes (Cassini and the Mars Exploration Rovers being prominent examples), the type of mission and orbit Juno must undertake to accomplish its goals will subject the spacecraft to a truly massive radiation dose. In order to meet the mission’s science goals within the budget set by NASA, ...


22

Propulsion Until someone solves the N-body problem every spacecraft needs some kind of propulsion to correct its course during the mission. New Horizons uses a Hydrazine based propulsion system including four 4.4 N main thrusters and twelve 0.9 N attitude control thrusters. Its 77 kg fuel tank allows a total post launch delta-v of somewhere over 290 m/s (...


21

During the early part of the Apollo program, the "direct ascent" mode was favored and Lunar-orbit rendezvous (LOR) was considered far too complex. In fact, the specifications of the Apollo service module were set by the direct ascent plan: the SPS engine is sized to lift off from the moon, and the fuel tankage is sufficient for lunar ascent and return to ...


20

This is probably the easiest to answer if we take the same mission profile and just track from the Pluto flyby backwards. I'll make some rather broad assumptions and first order approximations, like that NASA had their NEXT ion thruster developed to the highest technology readiness level (they did exist when New Horizons launched, but not at TRL required to ...


20

The first, experimental redocking was performed on Soyuz 29 (though by crew of Soyuz 31) with the Salyut 6 station. Afterwards, the maneuver was repeated several times, usually between different ports of a station, moving a docked craft from one port to another, in order to make room for a new arrival, although other purposes happened too - e.g. visual ...


20

Power and Mass From this paper (emphasis mine): The specific power of an 241Am-fuelled RTG cannot match that of a 238Pu system (except perhaps at small power output levels); however, the design work undertaken provides confidence in potential capability and performance of 241Am systems for future space missions. Medium-sized RTGs in the 10 W to ...


19

There's an assumption in your question. the Apollo configuration of 3-person CSM and 2-person LM, launched atop a single vehicle was considered the optimal choice for its day. The simplest mission profile would have been a direct flight. The docking required for both EOR and LOR schemes seems to have been distrusted at the time; hence a major objective ...


18

The STEREO satellites used multiple gravitational assists from the Moon to significantly decrease the amount of fuel needed to put those two satellites into heliocentric orbits. The first flyby resulted in STEREO ahead (STEREO-A) being ejected from the Earth-Moon system with a semi-major axis slightly less than that of the Earth-Moon system. STEREO-A has a ...


18

Not very quickly, for a number of reasons. Here's a list of some of the reasons: Soyuz requires 2 astronauts just to fly it (Under nominal operations) It can only take down 3. Thus, 6 Soyuz launches would be required. (Note, this might be a reference to manned flight, Soyuz does have remote capabilities). Some work could probably be done to reduce that to 1 ...


17

There is a Soyuz capsule (source1) docked to the ISS at all times, allowing for immediate evacuation in an emergency. This limits the ISS to 3 people when it is the only capsule available. For Expidition 20, they docked 2 capsules, allowing for six astronauts at a time. Your scenario involves the destruction of these vessels and simultaneously ...


16

In addition to what John provided, it's also worth noting that given the scale of tens of thousands of years, the stars will actually move. This is clearly shown in a Wikipedia article. As can be show, Alpha Centauri will only be 3 Light Years away in about 30,000 years. Okay, so the fastest mission I've heard of using nearly obtainable technology is the ...


16

Here's how you can work it out. First, thrust in kilo-Newtons (kN) divided by mass in metric tons yields acceleration in meters-per-second-per-second. Divide by 10 to get acceleration in approximate Earth surface gravities (9.81 is the real factor). Dawn uses its thrusters only one at a time (they aren't pointed the same direction), and a single NSTAR ...


15

The point of the ISS is to study 0G. 1G sleeping bags defeat the purpose... The humans are experiment subjects too:)


15

OK let's build a hypothetical cylindrical sleeper system that could fit inside the crewed area of the current ISS for example, and look at some of the issues you would need to address. We'll name it after the famous Bill Haley and the Comets song: Shake, Rattle and Roll. You can also apply what's learned here to a futuristic, much larger structure for a ...


14

Max-Q is a function of both altitude and velocity. There isn't any reason in particular that it needs to fall at a particular Mach number. It's just the point at which the rate that atmospheric density is falling outpaces the rate at which the square of the velocity is increasing. Nothing more.


13

It will be several years before we get to see what actually happens here. However the overall driver for the currently stated NASA plan is money. (In contrast, the currently stated Russian plan seems disconnected from what one might assume about their budget realities.) If the NASA budget remains flat, and there is all expectation that it will, ...


13

Hellas basin is certainly an interesting region, and several landing site selection processes evaluated candidate sites in it, mostly in the Northernmost region that's above the 30° South circle of latitude:      All Mars candidate landing sites that were considered for all NASA missions up to Mars 2020 Rover. Source: 1st Mars &...


13

The big difference is in weight. Satellites in Earth orbit can be much heavier than deep space probes, simply because it takes a lot of energy to launch something into an Earth-escape trajectory. Satellites are often in the region of 8 tons, while deep space probes are rarely above 1 ton. The materials are mostly the same. Aluminium for the structure, the ...


12

The software used for this at JPL is all homegrown. A great deal of effort goes into the optimization algorithms for complex, multi-body and/or low-thrust trajectories. You can try to request tools here. Examples are CATO, Mystic, and MALTO. However these tools are not really intended to be "user friendly", and require a great deal of domain expertise to ...


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