Question

Cum sunt controlate pozitia si orientarea unui satelit in spatiu ?

Answer 1

Exista intr-adevar exista doua aspecte legate de control:

a) controlul orbitei (pozitia in spatiu) si

b) controlul orientarii (cum este orientat satelitul).

Cele 2 depind fundamental de tipul de misiune despre care vorbim (platforme mari sau mici, zbor in jurul Pamantului sau interplanetar, precizia dorita, constrangeri impuse de restul echipamentelor de bord etc). In mod simplist controlul se poate imparti in activ (atunci cand poate fi comandat- fie de la sol, fie autonom de catre calculatorul de bord) si pasiv (cand nu poate fi comandat depinzand de alti factori externi).

Controlul activ se poate face prin:

1.motoare

2.dispozitive de generare si stocare a momentului unghiular

3.dispozitive electro-magnetice

Controlul pasiv se poate face prin:

1.folosirea fortei gravitationale

2.dipol magnetic

3.stabilizare aerodinamica

4.folosirea presiunii solare

De departe cele mai folosite si cunoscute sunt motoarele grupate dupa categoriile a) si b) in functie de scopul lor, cele de tip a) dezvoltand o forta de tractiune mult mai insemnata dar fiind folosite doar pentru ocazii rare, iar cele de tip b) dezvoltand o forta mai mica dar fiind folosite periodic.

Propulsia poate fi de mai multe feluri: chimica, ionica sau nucleara in functie de principiul folosit. Cele mai uzuale sunt motoarele chimice care se impart la randul lor in "hot" sau "cold" in functie de tipul reactiei chimice. Ele pot folosi doar combustibilul efectiv (caz in care se numesc "monopropelant") sau combinatia combustibil-oxidant (caz in care se numesc "bipropelant").

Cel mai cunoscut caz de combustibil este hydrazina (N2H4) in combinatie cu hydrogen peroxide (H2O2). Alte variante sunt MMH (monomethylhydrazine- (CH3)NH(NH2)) sau UDMH (unsymmetrical dimethylhydrazine- (CH3)2N(NH2)) in combinatie cu nitrogen tetroxide N2O4. Toate aceste substate sunt foarte toxice, de aceea inainte de deorbitarea unui satelit (mai ales pentru cei care reintra in atmosfera si pot avea ramasite care cad pe Pamant) trebuie consumata toata resursa de combustibil de la bord. Deasemenea lansarile se fac de fiecare data pe culoare sigure (spre ex deasupra marii) unde impactul unui accident este minim.

Mai multe in articolul urmator:

http://www.spacealliance.ro/articles/view.aspx?id=200903060429

 

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