# Tag Info

66

Well, it is very common indeed to regain communications with a space probe after losing contact. In fact, communications are generally not continuous for the entirety of any mission. These are generally planned, for example This happened with almost each and every satellite at the beginning of the space age. Both the former USSR and the US are huge ...

49

An elliptical one. The Wikipedia page you link gives a signfiicantly different apogee and perigee and a period of 20.8 hours. So, on average, it moves West to East a bit faster than the Earth does, but at apogee it's moving more slowly and the Earth overtakes it a bit (which are the "S-bends" in the track). It swings a little North of the equatorial plane ...

43

All interplanetary probes that I am aware of were launched into a parking orbit, and then waited some time in that orbit before restarting a stage or igniting another stage to inject on the desired outgoing asymptote. This is done for convenience to allow long launch windows on days in the launch period. It is possible and slightly more efficient to launch ...

36

Keeping a burnt-out stage attached doesn't hurt until it's time to start the next stage. In fact, keeping it attached until shortly before it's time to ignite the next stage can improve the total launch delta V. Stage three separation occurred at an altitude of 184 km. There's still air up there. It's not very dense air, but for a vehicle going at close to ...

28

Besides limiting aerodynamic stress and drag losses as you and Antzi mention, using the core engine only at high altitude means the engine can be optimized for low-pressure use by putting a larger nozzle on it. This optimizes expansion of the exhaust, and in the case of GSLV MkIII contributes to a ~6% increase in specific impulse over the sea-level version ...

24

As @Ame mentioned, the rocket didn't have enough fuel to put it there in one shot, like most US/Russian rockets do. However, the actual physics behind the orbital maneuver is slightly different than described. Specifically, the physics is called the Oberth effect. The short explanation of this is that a rocket thrust is more effective if done at perigee. ...

21

There are several reasons why Satellites need to orbit Earth before they go interplanetary... The first reason: The launch site is very rarely in the right position to start an interplanetary flight. Earth rotates on a tilt, so a launch has to be timed when Kennedy Space Center crosses the ecliptic plane (the general plane that most planets orbit on). Also, ...

21

Comparing Mangalyaan (MOM) to Maven there's a significant difference in mission, scientific capabilities and operational lifetime. Maven's primary purpose is to study the martian atmosphere, whereas MOM is more of a general purpose probe with surface study instruments. Maven has over 4 times the payload (65kg vs 15kg) and nearly double the number of ...

21

China has nothing to prove in this case, as it asked to be part of the International Space Station. This request was shut down by the US Government, which now prevents NASA from working with any Chinese citizen affiliated with the government (e.g. CNSA). This is entirely on the US and its decision to bar the CNSA from any cooperation with NASA, and not on a ...

20

Are there any space probes\landers which regain communication after being lost? IMAGE Contact was lost with IMAGE on December 18, 2005, 07:39 UTC and it was detected again by amateur satellite hunter Scott Tilley on January 20, 2018. You can read more about it in that Wikipedia article and this answer and this answer SOHO SOHO was nearly lost. ...

18

Sphere of influence The gravitational sphere of influence asks which of two gravitating bodies should be used as the origin for purposes of modeling the behavior of some third body such as a spacecraft. This comes into play in at least two key places: In a patched conic approximation, what's the right place to switch from one conic to another? When a ...

17

As per "From lighter rocket to slingshot, Isro innovates its way to Mars" from Hindustan Times: The main reasons for the low cost are: Low labour cost. In India scientists are working with very low pay which indirectly drives cost down. Scientists relied on technologies they had used before. India had their PSLV launches before. The hardware of Chandrayaan ...

16

The coasting period is certainly to perform a Gravity Turn. It is a trajectory optimization that uses gravity to steer the vehicle onto its desired trajectory. ... the thrust is not used to change the ship's direction, so more of it is used to accelerate the vehicle into orbit. Once the vehicle has coasted into the right angle, P4 ignition takes ...

16

Your assumption that we need max thrust at takeoff is partially wrong. Although right at takeoff you do want max thrust, it might be counterproductive short after: Your rocket and payload are Max G rated. You can't have an arbitrary high acceleration Atmospheric drag is higher at lower altitude and increase with the square of speed. If you go too fast too ...

16

It was not a thermal image at all. It is an optical image that has been captured by Orbiter of the lander spot and not thermal image as reported by others media houses. OHRC is same like our human eye. Since it consists of only one spectral band in visible region, so Image will be of gray scale, Not color image. https://twitter.com/Madrassan_Pinky/...

14

In the case of India's PSLV, the launch vehicle is not powerful enough to insert the Mars Orbiter Mission probe directly on a route to Mars. In contrast MAVEN is to be launched using the much more powerful Atlas V. The probe has to use gravity assist to gain enough velocity to travel to Mars. I.e. the probe first goes into a highly elliptical orbit, and ...

13

ISRO calls these "Midnight Maneuvers". This question, why do these maneuvers fall at around midnight Indian Standard Time (IST), has been asked by some of their readers on Mars Orbiter Mission's Facebook page before, and ISRO answered: “Firing has to happen near the perigee and in the visibility from ISTRAC ground stations. All these orbits have ...

12

Their future plans does not have Mars as a target at the moment. The ISRO is working manned mission technology in addition to the Moon, Venus, Sun and asteroid probes. They are also working to collaborate more with NASA on Mars and Moon missions after their first successful NASA/ISRO success: “To this end the working group agreed to continue discussions ...

12

There are a couple of definitions, but the most useful one is called the Hill Sphere. Essentially this is the area around which one can orbit around an object, and not be pulled away by another object (Such as the Sun). As the linked article states, it can be calculated for objects that have one object much more massive than the other (Almost every case of ...

10

ISRO's MOM lifting off (credit ...

10

Kerbal Space Program, the video game, teaches us that it is most effective to thrust at apoapsis (highest point of orbit) to increase our periapsis (lowest point of orbit). Waiting to fire the next stage there will make better use of fuel. Note that you want all the force applied at apoapsis, so you want to burn a little before and after it, since it is a ...

10

Any rocket flight will involve a burn in it's final orbital position. If you want to enter a 500km orbit your engine will shut down at 500km up. The profile shows it needs nearly 19 minutes to reach altitude but the rocket burn times only add up to 15 minutes. You can't magically make it get there in 15 minutes because you don't have extra fuel. Thus the ...

10

The biggest factor is probably the "inside-out" staging design, where the solid core burns out but is not jettisoned, while the liquid boosters continue to run. Spaceflight101 gives the empty mass of the (steel-cased) solid stage as 28 tons (with an unremarkable 83% mass fraction); this means the otherwise decent specific impulse of the strap-on engines is ...

10

PSLV is a bit of a weird duck because it's a transitional step from small solid-rocket designs to larger ones that rely more heavily on liquid rocket engines with higher specific impulse. It doesn't represent an uncompromised "clean sheet" optimal design. ISRO's first two orbital launcher designs, SLV (1979-1983) and ASLV (1987-1994), were small, not-very-...

10

The degree of orbital shadowing experienced by an orbiting object with small orbital altitude is determined by its beta angle (normally used in reference to LEO objects but the concept applies to lunar orbiters as well). The angle is taken between the satellite's orbital plane and the vector to the Sun. Depending on the value of the beta angle, a satellite ...

9

Other than taking images of Mars' moon Deimos far side (something not done in decades) not much has been attributed to MOM yet. The key here is to remember that the the orbiter likely won't discover anything per se, but the science data it produces can be used (probably in conjunction with other data) to help us understand the history of Mars. Here is an ...

9

I think a somewhat reasonable first-order analysis would look at the fates of similar hard impact failures on the moon and in deep space. The most immediately relevant is the failure of Israel's Beresheet lander, which failed similarly during landing. Beresheet was much smaller and lighter, so the hard impact resulted in total loss of mission. I think the ...

8

Before you get to all other advantages, let's start with the single, essential one. A rocket floating in place (not flying up at all, just hovering over the launchpad) needs to generate enough thrust that would otherwise give it $9.8 m/s^2$ acceleration (1g) in horizontal flight. That's quite a bit, and that's all wasted thrust. If you launch directly up, ...

8

There were plans for a Venus mission in 2015 (alternate article) An Indian scientific mission to Venus is being considered by the space community. This was announced by M S Anurup of Isro at the 17th National Space Science Symposium which has been jointly organised by Isro and Sri Venkateshwara University. According to Anurup, a preliminary ...

8

"CLG INIT" stands for "closed loop guidance initiation", and means that the launcher is switching into a mode where it actively steers based on its current trajectory rather than a fixed, unconditional program (referred to as "open loop guidance"). In the early part of flight, it is safer to use a "pitch-versus-time" or similar simple logic to guide the ...

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