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Questions tagged [guidance]

Questions which relate to how spacecraft and rockets navigate and stay on course.

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2
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1answer
498 views

Samples of old guidance software using computational resources on Earth implementing navigation in space

Answers to Given small computational resources how navigation was implemented ( Not Samples of old guidance software) are excellent. I was stunned to see an article mentioning 65KB was used to ...
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0answers
65 views

Iterative Guidance Mode (Saturn V ascent guidance)

I tried to implement the iterative guidance mode algorithm given in the paper "Development of the iterative guidance mode with its application to various vehicles and missions" by D. C. CHANDLER and I....
4
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0answers
46 views

Optimal Trajectory for SLV in the last stage

I have developed an algorithm for SLV guidance using optimal control theory. I need a reference trajectory to verify my algorithm. The algorithm requires the initial position and velocity coordinates ...
13
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1answer
2k views

Double redundancy for the Saturn V LVDC computer memory, how were disagreements resolved?

In the Smarter Every Day video How did NASA Steer the Saturn V?- Smarter Every Day 223 Destin is talking with Luke Talley about the memory modules used in the Saturn V LVDC computer. This computer ...
12
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2answers
3k views

Did the 1202 error and associated reboot prevent disaster on Apollo 11 landing?

Most accounts of the famous 1202 error reported by the AGS during landing of the Apollo 11 LM characterize the event as result of the successful operation of the AGS, flushing an resetting an ...
8
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1answer
297 views

Apollo-11 delta-v “due to residual pressure in the docking tunnel pushing the spacecraft apart” detected as it happened? Was it corrected?

This answer to How far off did Apollo 11 land? mentions that: Eagle was already 3 miles downrange from the expected position at the start of descent, due to residual pressure in the docking ...
15
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2answers
2k views

What is a “Lear Processor” and how did it work?

This answer to the question What was the mascon “fix” used by Apollo 12? says (in part): The Tindallgrams have some notes on the matter. See pages 307 to 354 of http://www.collectspace.com/...
2
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1answer
76 views

Satellite mission design/performance requirements to attitude/orbit control design specifications

Are there any good sources that discuss: the steps involved in deriving attitude/orbit control design specifications, from satellite mission design/performance requirements?
22
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2answers
3k views

How did the Apollo guidance computer handle parity bit errors?

The following answers mention the use of parity bits in the Apollo guidance computer: this answer to Bits per core for the different versions of the Apollo guidance computer core rope memory? this ...
2
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3answers
182 views

Stability of rocket during flight; why does the lift force change direction when the center of pressure moves?

I am currently learning about fins and the role they play in the stability of a rocket during flight. I came across a relatively minor problem. Here is one of the resources I'm looking at: http://www....
3
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2answers
213 views

Launch profile autopilot

I'm new here, and I am delighted this forum exists! I'm working on a spaceflight simulator (FSX SpacePort) and currently, developing automated guidance module (I guess, a space autopilot). The ...
7
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1answer
508 views

How did the Apollo guidance computer handle the Earth-Moon system's rotation around the Sun?

In this comment I just wrote: "...but at all other times it is just doing math to calculate its trajectory." The math needed a stable clock Timing accuracy of the Apollo Guidance Computer? (also 2, ...
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Lunar ascent module: Guidance Law [duplicate]

I was wondering if there was an optimal law for the thrust (magnitude and direction) during the lunar ascent. I have read many things about this topic in this forum but I still have some doubts. It ...
15
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1answer
1k views

Soyuz Steering during Re-Entry

In this youtube video, it talks about steering Soyuz by changing lift. Why does roll rotation help in changing lift and also helping in cross range steering? I am looking for an answer from ...
8
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1answer
278 views

Bits per core for the different versions of the Apollo guidance computer core rope memory?

The first version of the Apollo guidance computer had a ROM of only 12 K words of 16 bit. Later it was doubled to 24 K and finaly tripled to 36 K words. The first version of core rope read only ...
2
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1answer
101 views

Apollo guidance computer ROM addressing using the ROM bank register, what is the bank register size?

The Apollo guidance computer had 36 K words of core rope ROM. To address 36864 words, a 15 bit memory address for up to 32768 words is not enough, 16 bits are needed. This Wikipedia article describes ...
2
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0answers
73 views

How are Launch Ascent Trajectories and Reentry Constraints Being Implemented these days?

Historically, endoatmospheric guidance for launch ascent has been open loop and suboptimal. Recently, however, it seems as though there has been renewed interest in determining optimal endoatmospheric ...
4
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0answers
367 views

Why would someone use Modified Rodrigues Parameters over Quaternions for spacecraft attitude estimation? And vice versa?

I see quite some papers on spacecraft attitude determination and control, that rely on quaternions. While some others rely on MRPs. The advantage that I see so far is that... for quaternions, the ...
1
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1answer
274 views

How accurate can a satellite's orbit be?

How precise can an artificial satellite be when it comes to following the exact orbit in relation to Earth or hitting the same point above Earth in orbit? Which orbit would be the most stable for this?...
3
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1answer
162 views

What are common guidance strategies for a finite orbital maneuver?

Suppose we have our spacecraft in a circular orbit around the Moon and we want to transfer it to an elliptic orbit with a medium-thrust (10-100N) retrograde burn. Based on the current state estimate, ...
6
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1answer
366 views

How does the Apollo LM ascent guidance program P12 actually work?

P12 is the AGC guidance program for normal ascent from the lunar surface to orbit. According to the mission planning documents, after separation and ignition, the ascent stage holds its initial ...
8
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1answer
868 views

Machine Learning and Classical Navigation, Guidance and Control in Space Exploration

Due to the increasing availability of large quantities of data and computational power, machine learning (ML) is providing increasingly better results in various fields. Much research has been done on ...
5
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0answers
152 views

Small-bodies landing strategies

Looking at past landing missions on small bodies such as Eros, Itokawa and 67P I found different landing strategies Eros: NEAR Shoemaker probe performed 4 impulsive pre-planned open-loop maneuvers to ...
10
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1answer
566 views

Timing accuracy of the Apollo Guidance Computer?

The AGC timing reference came from a 2.048 MHz crystal clock. But how accurate was this clock circuit? Note 3 of this schematic: "The value of the follwing components to be determined at unit test" is ...
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57 views

Was Houston able to control to the Apollo spacecraft if needed? [duplicate]

Was every aspect of a flight, aside from liftoff, solely the responsibility of the crew? Or was Houston able to command parts of the spacecraft and its computers remotely in an emergency or if ...
6
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1answer
332 views

How did the upper stage of the Juno 1 rocket change its orientation while it was spinning?

The upper stage of the Juno 1 rocket was spun up to a high speed prior to launch so it would be spin stabilized and not require a guidance system. After the upper stage separated from the 1st stage it ...
6
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1answer
520 views

Saturn launch precautions for clearing tower?

In watching some Saturn rocket launches from the perspective of the camera being on the launch tower, it seems as if there was relatively little distance between the launching rocket and the tower. I ...
5
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1answer
1k views

Saturn V ascent guidance (simulation)

A while ago, I did a Saturn V ascent simulation in Matlab. The catering for drag, gravity and thrust vectors and mass depletion worked well, but I struggled to implement ascent guidance. I duplicated ...
24
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2answers
13k views

How are the SpaceX Falcon 9 Mod 3 and Mod 4 grid fins different?

Elon Musk tweeted "Flying with larger & significantly upgraded hypersonic grid fins. Single piece cast & cut titanium. Can take reentry heat with no shielding." These have been commonly known ...
4
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0answers
185 views

Apollo re-entry guidance

I am referencing chapter 7 of the book "Spacecraft Navigation and Guidance" by Maxwell Noton. Can anyone tell me how to determine control gains C1 and C2 in equation 7.58 and 7.59 in respective ...
4
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1answer
898 views

Best practices for rocket ascent trajectory guidance

I thought I would ask what the most used methods in industry are, in order to guide a launch vehicle into a desired circular orbit at engine cutoff. It seems that the use of direction collocation ...
4
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0answers
210 views

Lunar Descent and Landing Simulation

I am trying to simulate lunar descent and landing as a part of my undergraduate project. For time being, I have included gravity turn guidance scheme and used these equations Now, I can solve ...
6
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1answer
284 views

Apollo guidance

I am studying the Apollo Guidance, specifically the derivation of guidance equation. While laying the baseline, a Target-referenced time (T) is chosen as time variable for guidance calculation of the ...
4
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3answers
364 views

How can a deep-space spacecraft determine in real time the direction of delta-v?

My spacecraft knows it wants to add a certain delta-v in a certain direction to its motion, relative to the stars. It will calculate current mass based on propellant usage history, which hasn't been ...
8
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1answer
331 views

How does Schiaparelli's guidance system work?

I was not able to find any technical documentation on the closed loop guidance system that was supposed to accomplish the powered descent of ESA's Schiaparelli Entry Demonstrator Module. Several ...
4
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2answers
679 views

Generally, what types of sensors are used in rocket guidance systems?

I was wondering how a rocket adjusts its position to ensure it takes the desired path. What sensors, or generally technology, are used to gain data on the rocket's position, where it is heading and ...
2
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2answers
554 views

Rocket drag and lift based on flight direction - in which frame of reference?

Drag is aerodynamic force component parallel to the direction of motion. Lift is aerodynamic force component perpendicular to the direction of motion. Direction of motion with respect to what? 1) ...
5
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3answers
1k views

Is aerodynamic lift ever useful in rocket flight?

When a rocket is traveling through an atmosphere, the component of the aerodynamic force in the direction of motion is called drag, and the component perpendicular to that is called lift. Usually a ...
5
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1answer
1k views

Coefficients for linear tangent steering law

Given certain simplifying assumptions, a "linear tangent" steering law is optimal for orbital insertion of a launch vehicle: $$\tan \psi = a\cdot t + b$$ i.e. the tangent of the flight path angle ...
3
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2answers
225 views

State of the art of satellite Attitude Determination and Control Systems

I know I might get an answer like "the sky is not the limit"... But considering the actual state of the art of modern satellites ADC systems. Haven't we reached a "maximum" yet? Or are there still a ...
4
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1answer
432 views

How does rocket guidance deal with changing mass?

The first stage of the Saturn V, for example, burned about 26 tons of material in total per second (https://en.wikipedia.org/wiki/Rocketdyne_F-1#Specifications). Therefore the rocket dynamics are ...
5
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3answers
1k views

How are IMU positions decided for rockets and spacecraft?

I imagine that engineers have to decide where an inertial measurement unit (or just an accelerometer, gyro, etc.) is placed in a rocket or spacecraft. I'd like to know how are these positions decided? ...
8
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1answer
792 views

What is the maximum acceptable latency in rocket control computers?

Rockets require real-time computers, in that there are operational deadlines between events and system response. How quickly does the rocket's controller need to respond to sensors and events, without ...
19
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2answers
7k views

How did NASA remotely fix the code on the Mars Pathfinder?

In 1997, NASA remotely fixed a bug that caused priority inversion on their Mars Pathfinder. How did they go about doing this? What kind of communication protocols are used? How do they update the ...
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2answers
895 views

Does terminal velocity play a significant role when launching from Earth?

As mentioned in the question Climbing at terminal velocity minimizes losses? But why? And "of what"? terminal velocity is important when launching space craft from Kerbal (Game Kerbal Space ...
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4answers
3k views

How does the Falcon 9 know where the landing barge/pad is?

The descending Falcon 9 has got to hit (preferably gently) the tiny target of the Autonomous Spaceport Drone Ship (ASDS) in the middle of the ocean. How does the Falcon 9 know where the ASDS is? ...
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1answer
2k views

Were the aerodynamic control surfaces of the Space Shuttle used during ascent?

The Space Shuttle had several aerodynamic control surfaces to control it during reentry and the final phase of atmospheric flight to landing. It seems a waste to haul tons of control surface to orbit ...
20
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1answer
3k views

How do single engine rockets control roll?

While it's obvious how a single gimbaling engine can control a rockets attitude, it is less clear how it could control roll. Nonetheless many rockets use just a single main engine with no fins or ...
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1answer
2k views

Climbing at terminal velocity minimizes losses? But why? And “of what”?

A lucky discovery of a Kerbal engineer's writing gave this deep insight into the mechanics of climbing to orbit: the best way to minimize d/v losses through the atmosphere is to always go at ...
20
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3answers
3k views

Fortran and the Apollo 11 mission

I was just wondering, as a Fortran user. As far as I know, the simulations taken in order to carry the Apollo 11 mission was written in Fortran 2. I would like to confirm this from a reliable source. ...