# Tag Info

90

Technically, yes, it would be easier to put people on Venus. You need less of a kick for the interplanetary trip and slowing down is trivial with that dense atmosphere...one of the Pioneer Multiprobe sub-probes made a soft landing despite only being designed as atmospheric probes. However, the surface temperature stays close to 464 °C, with over 90 ...

75

Nibiru is fiction. Nibiru, a purported large object headed toward Earth, simply put - does not exist. There is no credible evidence - telescopic or otherwise - for this object's existence. There is also no evidence of any kind for its gravitational effects upon bodies in our solar system. The nice thing about astronomy is that everyone can do it. You ...

59

As long as neither spacecraft nor the astronaut are accelerating or decelerating, the relative speed of the spacecraft and the astronaut remains the same. So the astronaut will hover near the spacecraft. The actual velocity is irrelevant here, it's the same principle with every spacewalk: the ISS is moving at about 27,600 km/h, yet the astronauts do not "...

58

The reason is delta-v, which is a crucial concept in Spaceflight. It means change in velocity, and is the primary 'currency' that space mission have to expend in order to reach places in the solar system. On earth, if you want to go anywhere, you can get there at any speed, it just takes longer. Unfortunately, that is not how it works in space, because the ...

49

Yes, Trajectory Correction Maneuvers (TCMs) are always performed during cruise phases, whether before or after gravity assist flybys. This NASA tutorial serves as a good general reference. One source of error resulting in an imperfect trajectory (one that would miss its aimpoint at the next destination, whether the ultimate destination or an intermediate ...

48

As others have already pointed out, getting humans to Venus would be marginally easier than getting them to Mars. Let's consider survival on Venus in a little more detail though. Although there haven't been any manned missions to either Mars or Venus, there have been unmanned missions to both. So let's consider how long those unmanned missions have survived. ...

47

Delta-V to LEO is about 10 km/s. From there to C3 (Earth escape) is another 3.2 km/s. It's just another 30% delta-V. The problem is the Tyranny of the Rocket Equation. More delta-V means more fuel. More fuel means more mass. More mass means more fuel. How much more? Fuel costs scale according to $e^{\frac{\Delta V}{v_e}}$, that is e to the power of the ratio ...

45

The answer to your title question "Why not travel to Mars in 2 months?" has already been answered. Money. Lots and lots of money. We should first note that the answer to a different question: "Why haven't people gone to Mars?" is much the same. Money. However the amount of money to go there in two months is many times greater than the money to go there ...

41

First a few terms: Low Earth Orbit (LEO) All spacecraft must first achieve low Earth orbit. This is true whether you're sending stuff to the Moon or Mars. Trans Mars Insertion (TMI) The burn needed to send something on its way to Mars. Delta-v Change in velocity needed. Usually measured in kilometers/second. An important metric for space missions. Earth ...

41

The name Nibiru does appear in science fiction. However, the stuff to which you refer is not science fiction. It's just baloney, malarkey, or "fake news." According to Wikipedia's article Nibiru cataclysm about the phony story, science ficition has made some oblique references to it: A viral marketing campaign for Sony Pictures' 2009 film 2012, ...

37

We didn't know how hostile Venus's surface was, until we had landed there. The atmosphere of Venus makes it easier to land there than Mars. From Wikipedia, we learn: Before radio observations in the 1960s, many believed that Venus contained a lush, Earth-like environment. While there was some concept that Venus was hot, and had a high pressure, the exact ...

35

It turns out that outer space is not a perfect vacuum: there are a few hydrogen atoms per cubic centimeter. (reference) For large X, non-relativistic physics, the astronaut and spacecraft will stay close enough to each other. Once X gets small, and you approach the speed of light, these hydrogen atoms could slow down your spacecraft. Therefore, to maintain ...

34

The icy moons are of interest for exploration as part of the overall "follow the water" strategy of exploration that NASA (and others) have been exploring for some time. The "where else can water be found" is a major question in e.g. the US Planetary Science Decadal Survey (which is a community-driven consensus document which outlines the questions of ...

34

It's not hard, it's just expensive. We know exactly how to do it. Compare this to building computer processors with 1nm transistors, or making reliable self-driving cars. Those are both things that we currently don't know how to do, and we don't even know exactly how to get better at doing them. Even going past low Earth orbit to another planet, like Mars, ...

33

Imagine a large vehicle that can recycle water and air, has shielding, and contains everything for a trip that would take months. This would be the cycler. The vehicle is heavy and is needed for a long trip; crew cannot survive in a small rocket. The benefit is that when you launch your crewed rocket to catch up with the cycler, you only need to accelerate ...

29

We have sent telescopes to other planets, almost all the optical sensors on probes are in fact telescopes so they can focus on a specific area in detail. These sensors are to explore the planets they orbit and their moons. We don't send deep space telescopes to other planets because it's pointless, a few million miles closer to even our closest neighbor ...

29

The performance of Shuttle-Centaur would have greatly exceeded that of either the Atlas-Centaur or Titan-Centaur combination. Neither the Atlas nor Titan were able to put a fully fueled Centaur into Earth orbit using only their lower stages. The Centaur would have burned part of its propellant completing the orbital insertion. In contrast, the shuttle ...

27

One good thing about these periodic trajectories / interplanetary orbits, be it Mars Cyclers, Earth-Moon Cyclers (gravity assist UP/DOWN Escalator Orbits), or Resonant Cyclers (fixed VISIT Orbits) is that they can be maintained with a relatively small penalty for the total mass of the spacecraft, so they could be whole industry complexes processing raw goods ...

27

Comet West with its unpredictable but estimated at 558 000 years period is a good contender. Since launch windows can aim for the alignment of N objects, the answer obviously tend to infinity. You also need to remember than launch windows are just "optimal launch times" Using non Hohmann transfers, or long parking orbits, you can launch any time (using ...

23

To resonate with @Hobbes general characterization: Nibiru is contrived nonsense. Ignoring the fact that previously announced dates for the Earth cataclysm have come and gone with no such mayhem, some adherents to the Nibiru cataclysm theory cling to the possibility that it is planet-sized, but so far out in the solar system that we haven't seen it yet. ...

23

Let's compare with 4G, for which I could find some numbers: Your cell phone is transmitting with speeds of up to 50MBps with a maximum of 1 Watt (can be as low as a few µW!), using a tiny antenna that is often obscured by water bags (human flesh and organs), rocks, buildings, trees, etc. Let's compare this with Mars Express, for example: its maximum ...

21

I feel this sort of question benefits from a series of thought experiments. Imagine instead that you've got two astronauts, side by side, zipping through space at some constant speed. They're kind of sweet on each other so they're holding hands. Awwwww. But then they suffer a cruel change of heart and stop holding hands! What do you imagine would ...

20

If the US Government ever gets back in gear, you can read NASA's Design Reference Architecture 5.0 (DRA 5) for human missions to Mars. (I have a copy, but I don't see a way to upload it here.) Here is a summary. The basic idea is to use several Saturn V's or equivalent, and put up pieces of the mission. Some parts are assembled in Earth orbit, some meet ...

20

One picture is worth all your base to us. Before we sent probes to Venus we had no pictures of its surface. Whether it lands or not you have to penetrate the atmosphere of Venus to take pictures of it, whereas the surface of Mars can be easily seen through its weak atmosphere from afar. Most of the information about Venus has been derived from the ...

20

Hohmann launch windows occur each synodic period. Or a more general version of a Hohmann transfer would be a transfer orbit tangent to both departure and destination orbits. This also occurs each synodic period plus or minus. Call period of departure orbit T1. Call orbital period of destination orbit T2. Synodic period = |(T1*T2)/(T1-T2)| So for example ...

19

Speed-of-light delay is mostly irrelevant for data transmission rates. Once you get out of Earth orbit, transmissions are generally "fire and forget"; if data gets garbled, you schedule a retransmission of the garbled portion at a later time. The limit for interplanetary communication rates is the Shannon limit: how fast you can send data while still being ...

19

This is basically the approach being considered for getting all of the hardware to Mars for a crewed mission. However instead of refueling an upper stage that was used to get you to orbit, it is considered much easier with almost the same benefit to launch an entire fueled stage with engines instead of just the tanks with propellant. The only penalty is ...

18

Here is an approximate but quite accurate solution. This assumes that the orbit about the departure body is aligned with the outgoing asymptote of the Hohmann orbit, which is the standard practice when putting a spacecraft in a parking orbit by a launch vehicle before its escape maneuver. This also assumes that the bodies' orbits about the Sun are circular ...

18

Yes, Pioneer 10 and 11 each carried a 0.000001 megapixel camera. The single pixel was scanned over the body by the constant spin of the spacecraft in one direction and a slew of the spacecraft in the other. Building up one image took a long time, over which the relative position of the spacecraft and the body changed quite a bit, distorting the image. ...

18

The asteroid belt isn't nearly as dense as popular media makes it out to be. An answer from the Dawn Mission's FAQ, specifically "What is the average distance between individual asteroids? (6/13/10)", helps here. Asteroids are not distributed uniformly in the asteroid belt, but could be approximated to be evenly spaced in a region from 2.2 AU (1 AU ...

Only top voted, non community-wiki answers of a minimum length are eligible