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A small push slows a spacecraft by a hundred metres per second, and the air takes care of the other 7.8 kilometres per second, as a fireball.

11 min

NASA/JPL/Space Science Institute

ku A Local Solar System Itsinda Umunyamuryango na ku A. in iyi Ikintu?

Home i: ku Umuvuduko. A Kuva: Kuri Gukomatanya in. Bya ni Bya Kuri, na OYA Kuri Inyuma Umwanya.

A ballistic capsule entering from a 400 km orbit, and three returns from the Moon compared (too steep, right, too shallow). Point-mass model with an exponential atmosphere.

Tangira & vendorShortName; i. i.

Kureba

  1. i , i ya: A iminota na Hasi ku 100 m / s. i Iburyo: Bya i.
  2. Entry interface, about 120 km up. The capsule meets the first thin traces of air still moving at about 7.8 km/s.
  3. . Mbere Bya i ni Ikomeye, Bya Dogere Kubona Gihinguranya ya: A i & Ubwoko: Bya i Idirishya.
  4. i Kuva: i Ku 11 km / s, i Icyinjijwe Imfuruka Iburyo: Kuri A Bya A Dogere: na i i, na i Bidakora Bidakora i Nka A Bidakora amazi.
  5. . Bigyanye 10 i ni Ku A Km H. Gufungura, na Ku A Isigamwanya.

Gusobanukirwa

From a 400 km circular orbit (r = 6,778 km) the speed is 7.67 km/s. An ellipse whose low point is 50 km up has a = 6,603 km, and at 400 km its speed must be 7.57 km/s. The deorbit burn is the difference: about 102 m/s, just 1.3% of the orbital speed.

ni ½ V² A Air density ρ roughly halves every 5 km of descent (scale height about 7.2 km), so the deceleration rises steeply, peaks, and falls as the capsule slows. i Urugero hejuru:

IcyinjijweUmuvudukoInguniGuhagarika
Hasi:7.85 km/s1.5°8 g
i11 km/s8°about 31 g
i in i11 km/s5.6°7 G
i,11 km/s4.8°Inyuma Inyuma

Na: A Kwimura (Cya hafi Bya ni Bidakora - Hagati:, na Kuri, i Kuri 4 g ya: A na Kuri 2 Dogere.

Umunyeshuri

Urugero i Bya Na: na Kurura:

dv/dt = −μ r/|r|³ − (ρ(h) |v| / 2β) v,   ρ(h) = ρ₀ e^(−h/H)

with β = m/(C_D A) = 350 kg/m² (capsule-like) and H = 7.2 km. A Icyinjijwe, na (1958) i ni Bya β:

a_max ≈ v_E² sin γ / (2 e H)

For the steep lunar case (γ = 8°) it gives about 44 g; the full simulation gives 31 g, because gravity keeps bending the path shallower as the capsule descends. , i Icyinjijwe Imfuruka, OYA i Ingano:, i G - Ibirimo, ni buri A.

Gushaka

Using the vis-viva lesson, check the deorbit burn: a circular orbit at 400 km (r = 6,778 km) has speed √(μ/r). An ellipse from 400 km down to 50 km has a = (6,778 + 6,428)/2. How much slower must the capsule go at 400 km? (μ = 398,600 km³/s²)

Igisubizo

3 Muhugura Ibibazo. Kuri NIBA ni i Iburyo:.

  1. About how much must a spacecraft slow down in orbit to start coming home from 400 km?

    1. A 7.7 km/s
    2. B About 100 m/s
    3. C 1. km/ s
    4. D Guhagarara
    i

    B. About 100 m/s A Gitoya i Bya i i; i i Bya i Umuvuduko.

  2. i

    1. A Na: i Ikimenyetso
    2. B in Imbere Bya Gihinguranya Nka
    3. C Amashanyarazi
    4. D Ibikorwa
    i

    B. in Imbere Bya Gihinguranya Nka

  3. NIBA A Kuva: i i

    1. A Byahinduwe
    2. B Guhagarara Inyuma Umwanya
    3. C Hejuru
    4. D in
    i

    B. Guhagarara Inyuma Umwanya

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