Ukungeniswa kwe-orbital: ukuqashwa

Ngomhla ka-10 kuMashi 2006, ngemuva kwezinyanga ezisithupha ezindaweni ezingaphandle kwelanga, iMars Reconnaissance Orbiter ye NASA yafaka izinjini zayo ezine ezinkulu ngemizuzu engu-27. Ngongxenye yale sikhathi yayingaphansi kweMars, ngaphandle kokuxhumana kwe-radio: akukho muntu emhlabeni ongakwazi ukwazi ukuthi isebenzela yini. Uma ukudlidliza kungakaphumelela, i-spacecraft izohamba ngaphezu kweMars futhi ifike e-orbit engapheli ngaphesheya kwelanga.

Ukufika akunembile. Kudingeka uthathelwe.

Bona

I-spaceship ayikwazi “ukuyeka” eplanethi. Iwela kuyo, ihamba ngokushesha njengoba ifika eduze, ku-curve evulekile ebizwa nge-hyperbola. Uma ishiya icala, izohamba ngaphesheya kweplanethi futhi ikhuphuke kancane, ngokuya ngejubane layo.

Ukuhlala, kufanele ilahlekelwa yijubane ngesikhathi esifanele, ukufinyelela okuncane:

1. I-capture burn. Ama-engine ashaya ngokumelene nesimo sokuhamba. Umlilo ophansi uguqula i-curve evulekile ibe yi-ellipsis ende, evala.
2. Aerobraking. Ngezansi kokushaya ngaphezu kwegesi, abalawuli bakhuphula indawo ephansi ye-orbit engxenyeni ephezulu ye-atmosphere. Nganoma iyiphi indlela, i-air drag encane ihamba kancane futhi indawo ephezulu iwela phansi.
3. I-Science orbit. Ngemuva kwamakhulu ezikhathini ezingaphezu kwezinyanga eziyisithupha, i-MRO yafinyelela ku-orbit ephansi, encane kakhulu, eyi-250 nge-316 km phezulu, futhi ingaqala ukudweba i-Mars.

Ukuqonda

Ukusuka emhlabeni ngendlela efana neHohmann, indiza yelanga ifinyelela kuMars 2.65 km/s phezulu Kusuka engxenyeni yeMars, lokhu kuyi-”speed at infinity”, v∞. Ukuwa ku-426 km phezulu komhlaba, ihamba ngokushesha kuze kube

v = √(v∞² + 2μ/r) = √(2.65² + 2 × 42,828 / 3,822) ≈ 5.4 km/s

Ku-ellipsis kusuka ku-426 km kuya ku-44,500 km, isivinini esiphansi kufanele sibe yi-4.56 km/s (vis-viva). I-ideal, i-instantaneous capture burn yilokho okungo 0.87 km/s. Umlilo ongokoqobo wemizuzu engu-27 awusebenzi kahle ngoba usakazeka ngakwesobunxele; i-MRO yamisa isithuthi sezulu ngamakhilomitha angu-1/s.

Ukuqoqa ngokuqondile ku-orbit ephansi ye-circular kuzobiza cishe amakhilomitha ayi-2 / s (bona Zama). Ukubhujiswa kwe-aerobraking kulondoloza ingxenye enkulu yale nkinga, futhi igesi egcinwe ibe yimoto yendawo kanye nesayensi.

Umphathi

I-hyperbola inengxenye enkulu yomgwaqo a = −μ/v∞² nesimo esihlukile e = 1 + r_p v∞²/μ. Isikhathi sokuhamba kusuka kude kuya ku-periapsis sibekwe yi-equation ye-hyperbolic Kepler M = e sinh F − F.

Ukuqapha Δv ku-periapsis r_p kuya elithipheni nge-apoapsis r_a yi

Δv = √(v∞² + 2μ/r_p) − √(2μ r_a / (r_p (r_p + r_a)))

oncane kakhulu ku-ellipse ende kakhulu (r_a → enkulu): indiza yendawo engaphandle ayikwazi ukuthathwa. Lokhu kusho ukuthi izindiza ziqala nge-orbit evulekile, futhi kungani i-aerobraking noma ukudlidliza okuncane kulandela. Imisebenzi yeMars esebenza ngeqembu, aerocapture (ukuhamba okunzulu olunye ngaphakathi kwe-atmosphere ngemuva kwesihlungi sokushisa) kungashintsha ukukhishwa komlilo wonke.