Tidal forces: Roche limit

thanks to one of my frequent readers I will add short post to tidal forces because I forgot very important thing: Roche limit.

Roche limit is distance from object (star, planet). If satellite (moon) crosses this distance it will be eventually ripped apart (by tidal forces). Important is that for every satellite it is different because every satellite, like man-made has different properties. It is very complicated to know exact Roche limit for anything because there is lot of stuff you must count in.


On first picture there is planet orbiting sun in save distance and no great tidal forces are disturbing it.

On second planet is coming closer to Roche limit and its shape is disturbed because red side is much closer.

When planet crosses limit is starts to be ripped apart. Stuff nearer (red) starts to fly faster and that is end to our planet.



Tidal force

sorry for not writing such long time, I was enjoying holidays for whole week. Anyway I am coming back with post about tidal force.

Tidal force is effect of gravitational force and it can be seen as for example tide.

So you have Moon which is attracting everything, even water in our oceans. Water closest to Moon is attracted with greatest force while water far away with least. As you can see on the picture there is Moon (Satellite) on the right this grants us two high tides per day.
So as is Moon orbiting it changes the place where low and high tides are.

This effect creates amazing things: rings! Planetary rings can be made by some satellite which moved too close to its planet and tidal forces were so strong that it ripped it apart, so there is higher probability that larger planet will have ring.

Tidal force also can be “seen” in effect called spaghettification which is made by black holes or other massive objects.


What could happen to our Universe: The Big Rip

before I continue with Apollo missions I will write something short about Space, this time what will happen to it.

There are three main hypothesis and in this post I will write about The Big Rip (TBR).t_{rip} - t_{0} \approx \frac{2}{3|1+w|H_0\sqrt{1-\Omega_m}}

Firstly I heard about it in the TV but it was not explained very well so I had to search on internet… i greatly recommend video by Kurzgesagt (its in english) and it summarizes perfectly what next posts will be about.

So TBR is theory about end of Universe  For the first time it was published in 2003.

It bases on the expansion of Universe which would increase over time so that observable Universe would shrink into area smaller than anything: atoms, quarks or even hypothethical preons so that no interaction would be possible. Everything would be torn apart because it would not be gravitationaly bounded.

This bases on thing called phantom energy (kind of dark energy) which would have “w” smaller than -1 (ratio between dark energy pressure and energy density).

In aprox. 22 billions years there would be nothing like Universe.


Apollo missions: Apollo 7

Before I start to talk about Apollo 7 I will try to explain why I skiped 2,3,4,5,6.
The reason is that before Apollo 1 there were not piloted missions: AS-201, AS-202 and AS-203 and they were renamed to Apollo 1A (wifes of dead astronauts did not wish to Apollo 1 name be used again), Apollo 2, Apollo 3 so next not piloted mission was called Apollo 4.

So just briefly: Apollo 4 was mission for test of heat shield.
Apollo 5 test of lunar modul on the orbit of Earth.
Apollo 6 second test of rocket Saturn V, there was problem in starting of third level of rocket so it had to land which was done without any problems.
Apollo 7 mission started 11th October 1968 and it was long about 11 days. It was first piloted mission which was completed in the program Apollo and also first which was seen in the TV.
Again there were three men: Walter Marty Schirra who was captain and this was his third mission, he is only astronaut who was in Mercury, Gemini and Apollo programs.
There was Donn Fulton Eisele and this was his first flight. And Walter Cunnigham (also first flight).

This mission was for the test of two new sections in the rocket and it was under way without any major problems. This mission was extremely important after catastrophe almost two years before.

There were couple of experiments running.
1) Scanning of Earth for geology, meteorology, hydrology.
2) Change in astronauts bones: there was less calcium.
3) Change in astronauts blood count (how much white and red blood cells there is in blood)
4) Blood pressure

While everything happened well enough there were some arguments between astronauts and between guys on Earth, that concluded into Donn´s and Walter´s ban for another missions.
Also even that all of them had their favorite food they had problems with it because it was too sweet and caloric and also all of them got flu on this mission.Posádka Apolla 7 (zleva: Eisele, Schirra a Cunningham)

163 turns around Earth were made


PS: here you can check my previous post on Apollo 1: https://dragallur.wordpress.com/2015/07/01/apollo-missions-apollo-1/
and here my prologue about Apollo program: https://dragallur.wordpress.com/2015/06/24/apollo-missions-prologue/

Apollo missions: Apollo 1

Let´s talk about first piloted mission of the program Apollo. Before this one there were other missions but without people (AS 201,AS 202,AS 203). Apollo 1 was planned for 21st February 1967 but it ended before it could even start.Apollo 1 patch.png

There were three guys in this mission
Virgil Ivan Grissom, Edward Higgins White, Roger Bruce Chaffee. All of them were experienced pilots from planes or Gemini missions… Grissom was captain.

So in 27th January there was one of many tests while this one was essential for leaving Earth month later.
Main problem with this mission was that it was made in great hurry so that NASA could finish goal made by president Kennedy. Guys who made cabin did that with flammable materials and NASA knew that. Problem was that it would need complete rebuilt of whole cabin to repair those problems and lot of money. So they decided to not to do anything with that.Posádka Apollo 1 - Grissom, White, Chaffee

All three members of crew knew that there are some mistakes and they were trying to point them out. Even that day of 27th January it was planned that Joe Shea will be present in this test inside rocket but he refused saying that he can watch from bunker. Slayton (guy who was candidate for astronaut) said that he will be there but finally he was not because there was not much free space inside.

Start of test had to be delayed because crew sensed some strange odor. Some guys checked it and it seemed that nothing is wrong. Cabin was full of pure oxygen with 110% atmospheric pressure which was purposeful to see if there are any gaps in cabin. Anyway you can probably see what happened now. First they had problems with radio connection and Grissom was saying something like this: “How can we land on Moon if we are not able to talk across three rooms!” Than some spark around Grissom´s seat made fire and it took five minutes before under-pressured cabin could be opened which was too late.

This was huge wound to NASA because it was first missions with people and it did not even started. Luckily next time it was much better prepared.