48
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What eliminates the velocity when occupants return from ISS to earth, and how much?
Nearly all the velocity is cancelled by atmospheric deceleration of the descent module, before its parachutes are deployed.
ISS orbital velocity is around 7700 m/s. An initial retro-burn of the ...
- 167k
28
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Do exploration spacecraft enter Mars atmosphere against Mars rotation, or on the same direction?
There is always a benefit to entering a planet's atmosphere with matching rotation.
In the case of Earth, the difference is a rather huge 920m/s effective airspeed between reentering prograde or ...
26
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What eliminates the velocity when occupants return from ISS to earth, and how much?
The process is described here, which answers nearly all of your question. The reentry burn removes about 120 m/s of velocity from the capsule (that's your 1) and the final impact is 15 miles per hour ...
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24
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Bounce off the atmosphere at reentry?
Yes, a capsule cannot literally bounce off the atmosphere and its kinetic energy must be reduced by an encounter with the atmosphere, rather it would just pass through the atmosphere and back into ...
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17
votes
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Can a reentry be done slowly?
Not without propellant. Or at least not easily. However the "why" is a bit tricky.
This is far from the whole story but one of the problems is that generating enough lift to keep you from diving too ...
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17
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Would it be feasible to decelerate a crewed vehicle from ~25 km/s only using the atmosphere of Mars (in the context of an "express transit")?
Nope, sorry.
Completely disregarding the (enormous) heat factor of the aerobraking.
The requirement specifies manned.
The path through Mars' atmosphere will be very nearly a straight line.
A bit of ...
16
votes
Multiple aerobraking
This works well in reality too, and helps to reduce heat loads.
The reason this is not used is the fact that you must then pass through the Van Allen radiation belts multiple times, where you ideally ...
16
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How do we control a Reentering Capsule in the denser part of the atmosphere?
The entry vehicle for the Apollo missions is the command
module (CM), which has a symmetric body with an offset center of
gravity (c.g.). This offset c.g. causes the CM to trim
...
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15
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Multiple aerobraking
This is used in reality, although it is not as easy to do in real life as it is in Kerbal Space Program. Such passes dramatically increase the heat that the capsule is forced to deal with, and as a ...
- 121k
14
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How do we control a Reentering Capsule in the denser part of the atmosphere?
For Gemini, Apollo, and Soyuz capsules, lift is achieved by offsetting the center of gravity of the reentry module from the center line of the craft. This is represented in your diagram by the "...
- 167k
13
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How can delta-v and aerobraking as shown in this chart be explained?
Here's the original source of the diagram:
https://www.reddit.com/r/space/comments/29cxi6/i_made_a_deltav_subway_map_of_the_solar_system/
Your concerns are also discussed there.
27000m/s is a very ...
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13
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Gliding into the atmosphere
It most certainly won't hurt anything. From FAA's document on returning from space, there is a very interesting chart, which I've included below.
So the maximum g load is almost always at around 4500 ...
- 121k
12
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Can a reentry be done slowly?
It is possible to do a slow and cool reentry. But it would be extreamly expensive.
Just slow down from orbit speed to subsonic speed above the atmosphere and then fight gravity until it is possible ...
- 48.8k
10
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How can delta-v and aerobraking as shown in this chart be explained?
The calculations for Ulysse Carion's chart were done by Curious Metaphor. If you go the this Reddit thread, you'll see a conversation between Curious Metaphor and I. For years I made delta V charts ...
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10
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Mathematically, what is the argument in favor of skipping reentries?
The two systems that I know of that were qualified for skip entry, Apollo and Shuttle, did so purely for cross-range capability. The skip entry would have been used for an emergency return that could ...
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9
votes
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Could a reentry powered monorail and flywheel make a kinetic engine for lift?
Take the super-optimistic 500 kJ/kg energy density of flywheel energy storage. In reality 10% of that would be a great result.
$ E_k = {1 \over 2} mv^2$ so 0.5*1kg*(8km/s)^2 = 32MJ per kilogram of ...
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9
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Do exploration spacecraft enter Mars atmosphere against Mars rotation, or on the same direction?
Space craft will tend to enter orbit counter clockwise as viewed from the northern hemisphere. This is due to the fact that most objects in the solar system orbit and rotate this way with the ...
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8
votes
Gliding into the atmosphere
You can't just slow it down over many orbits
I think the question is suggesting letting a little bit of drag slow the Cessna down until it's at a normal speed before gliding through the atmosphere. ...
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7
votes
What will Max Q for descent be?
According to https://www.flightclub.io/results/?code=SS10 , reentry Q for flights like SES-10 peak at almost 92kPa at T+434 sec, about 3x the ascent max Q.
The reentry prep burn brings velocity down ...
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7
votes
Gliding into the atmosphere
First of all, the heat shields aren't there just for the dense atmosphere with high deceleration, the upper atmosphere part of reentry also generates heat. If you had a craft that could fly in the ...
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7
votes
How can delta-v and aerobraking as shown in this chart be explained?
A 250km periapsis Earth orbit won't produce significant atmospheric drag. The inbound-aerobraking-possible notations for orbits are assuming that you dip lower into the atmosphere in order to slow ...
- 167k
7
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How can delta-v and aerobraking as shown in this chart be explained?
Adding to @Rikki-Tikki-Tavi answer.
For destinations where aerobraking is possible, and you have a sufficiently heat and acceleration hardened vehicle, it's possible to cheat. The map shows how much ...
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7
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Starting refueled in LEO, how much payload could a heat-protected Starship softly land on Mercury after a gravity assist from Venus?
A single Venus flyby helps, but it does not make the journey possible for Starship.
Below is a plot of 2025-2030 trajectories from Earth to Mercury that flyby Venus once. They are plotted by the Earth ...
- 9,685
6
votes
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Is this a first Mars aerobraking for ESA, or for anyone?
ESA has done aerobraking with Venus Express. NASA has done aerobraking at Mars several times, as well as at Venus. This will be the first time that ESA has done aerobraking at Mars.
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6
votes
Do exploration spacecraft enter Mars atmosphere against Mars rotation, or on the same direction?
See also answers to
How much does the rotation of the Earth affect re-entry and could we go against it?
When things land on Mars what fraction of their velocity do they remove propulsively?
...
- 149k
6
votes
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Starship reentry velocity on return from Mars: What are the options
Starship's limited $\Delta V$ means that it can't stray too far from minimum energy transfers.
100t payload + 120t dry mass + 1200t of propellant + 380s $I_{sp}$ $\to$ ~$6900m/s$, turns out this wasn'...
- 9,685
6
votes
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How did Venus Express' periapsis decay so quickly?
Venus Express (VEX) used a highly elliptical, polar orbit. A peculiar feature of this orbit around Venus is that the pericentre altitude will drift due to third body perturbations from the Sun's ...
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5
votes
In what atmospheric densities or pressures have aerobrakings been performed?
No spacecraft has yet used aerobraking for orbital insertion. That's called aerocapture. Aerobraking has been used by orbiters only after a propulsive orbital insertion.
What matters for the drag of ...
- 58.5k
5
votes
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How will BFS maneuver during aerobraking?
According to Elon, mainly with aerodynamic control surfaces.
Compared to the design I showed last time, you can see that there’s a small delta wing at the back of the rocket. The reason for that is ...
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