Content that violates any copyrights will be deleted. Encyclopedic content must be verifiable through citations to reliable sources.
You are about to undo an edit. Please check the comparison below to verify that this is what you want to do, then publish the changes below to finish undoing the edit. If you are undoing an edit that is not vandalism, explain the reason in the edit summary. Do not use the default message only. |
| Latest revision | Your text | ||
| Line 1: | Line 1: | ||
{{Refimprove|date=October 2013}} |
|||
{{Short description|Small rocket engines that help fuel settle in 0g before main engine start}} |
|||
[[File: |
[[File:Vasters 1761 (6586697303) (2).jpg|thumb|This [[Saturn IB]] second-stage Auxilliary Propulsion Unit is similar to one used on the [[Saturn V]] third stage, which performed as an ullage engine for [[translunar injection]].]] |
||
'''Ullage motors''' (also known as '''ullage engines''' or ''' ullage rockets''') are relatively small, independently fueled [[rocket engine]]s that may be fired prior to main engine ignition, when the vehicle is in a [[zero-g]] situation |
'''Ullage motors''' (also known as '''ullage engines''' or ''' ullage rockets''') are relatively small, independently fueled [[rocket engine]]s that may be fired to accelerate the [[rocket]] prior to main engine ignition, when the vehicle is in a [[zero-g]] situation. |
||
==Description== |
==Description== |
||
| ⚫ | [[Image:Saturn v schematic.jpg|thumb|right|Three sets of ullage motors are shown in this schematic of the [[Saturn V]] rocket]] |
||
[[Cryogenic]]-liquid-fueled rockets keep their propellants in insulated tanks. These tanks are never completely filled to allow for expansion. In [[weightlessness|micro-gravity]] conditions the cryogenic liquids are without a [[free surface]], and exist in a slushy state between solid, liquid, and gas. In this mixed state, [[ullage]] gases may be sucked into the engines, which is undesirable, as it displaces useful propellant, reduces efficiency, and may damage the engines. |
|||
Small rocket engines, called "ullage motors", are sometimes used to settle the propellant |
[[Cryogenic]]-liquid-fueled rockets keep their propellants in insulated tanks. These tanks are never completely filled to allow for expansion. In [[weightlessness|micro-gravity]] conditions the cryogenic liquids are without a [[free surface]] existing in a slushy state between solid, liquid, and gas. In this mixed state, [[ullage]] gases may be sucked into the engines, which is undesirable, as it displaces useful propellant, reduces efficiency, and may damage the engines. Small rocket engines, called "ullage motors", are sometimes used to settle the propellant prior to the main engine ignition to allow the formation of a temporary free surface (with a distinct boundary between liquid and gas states). These motors provide acceleration that moves the main engine liquid propellants to the bottom of their tanks ("bottom" in this usage always meaning relative to the alignment of the main motor the ullage motors are serving), so they can be pumped into the engine plumbing. The [[RM-81 Agena#Agena-A|Agena-A]] was one of the first vehicles to make use of an ullage system in preparation for ignition after separating from its [[Thor-Agena|Thor]] booster.<ref>{{cite journal|url=http://www.nro.gov/foia/declass/WS117L_Records/133.PDF|title=Discoverer I System Test Evaluation Report||publisher=National Reconnaissance Office|access-date=15 March 2015}}</ref> Failure of the Agena's internal timer was also blamed for premature ignition of this ullage system in the failed launch of "Discoverer Zero" on January 21, 1959.<ref>Philip Taubman, 2003; "Secret Empire", p721; {{ISBN|0-684-85699-9}}</ref> Such motors were also used by Soviet engineers for the [[Molniya (rocket)|Molniya]] interplanetary [[launch vehicle]] in 1960. |
||
The firing of the ullage motors is used |
The firing of the ullage motors is used during stage separation of rocket and/or stabilization of a rocket when there are brief reductions in acceleration which could allow the liquid propellant to float away from the engine intakes. Ullage motors are also commonly employed on deep-space missions where a [[liquid rocket]] needs to start a burn after traveling in micro-gravity. |
||
To perform this ullage pre-acceleration, [[reaction control system]] (RCS) thrusters are sometimes used. Larger ullage motors can also use solid propellant, which makes them generally single-use. |
|||
== American operations == |
|||
[[File:Saturn V Rocket, 3rd Stage – Johnson Space Center. 20-3-2017 (38889065350).jpg|thumb|left|Ullage engine on Saturn V third stage]] |
|||
| ⚫ |
[[ |
||
The [[RM-81 Agena#Agena-A|Agena-A]] was one of the first vehicles to make use of an ullage system in preparation for ignition after separating from its [[Thor-Agena|Thor]] booster.<ref>{{cite journal|url=http://www.nro.gov/foia/declass/WS117L_Records/133.PDF|title=Discoverer I System Test Evaluation Report|publisher=National Reconnaissance Office|access-date=15 March 2015}}</ref> Failure of the Agena's internal timer was also blamed for premature ignition of this ullage system in the failed launch of "Discoverer Zero" on January 21, 1959.<ref>Philip Taubman, 2003, ''Secret Empire - Eisenhower, the CIA, and the hidden story of America's space espionage'', p721; {{ISBN|0-684-85699-9}}</ref> |
|||
The second stage ([[S-II]]) of the [[Saturn V rocket]] used in the American [[Apollo program]] used four (originally eight) ullage motors located on the aft interstage skirt. In the [[S-IVB]] third stage, there was an Auxiliary Propulsion System that also had ullage functions. Ullage is often a secondary function of the [[reaction control system]] such as on the Apollo [[Lunar Module]] (LM). In his book ''Lost Moon'', [[Jim Lovell]] recounted a description of a course-correction burn of the LEM's main descent engine to re-enter a [[free return trajectory]] to Earth during the successful recovery of the [[Apollo 13]] capsule: |
The second stage ([[S-II]]) of the [[Saturn V rocket]] used in the American [[Apollo program]] used four (originally eight) ullage motors located on the aft interstage skirt. In the [[S-IVB]] third stage, there was an Auxiliary Propulsion System that also had ullage functions. Ullage is often a secondary function of the [[reaction control system]] such as on the Apollo [[Lunar Module]] (LM). In his book ''Lost Moon'', [[Jim Lovell]] recounted a description of a course-correction burn of the LEM's main descent engine to re-enter a [[free return trajectory]] to Earth during the successful recovery of the [[Apollo 13]] capsule: |
||
<blockquote>When the ship had stabilized in the proper attitude for firing, Lovell would deploy the LEM's landing gear, extending its four spidery legs to get them out of the way of the descent engine. Next the computer, relying on other instructions Haise typed into it, would fire four of |
<blockquote>When the ship had stabilized in the proper attitude for firing, Lovell would deploy the LEM's landing gear, extending its four spidery legs to get them out of the way of the descent engine. Next the computer, relying on other instructions Haise typed into it, would fire four of Aquarius's attitude jets for 7.5 seconds. This procedure, known as ''ullage'', was intended to jolt the spacecraft slightly forward and force the descent engine fuel to the bottom of its tanks, eliminating bubbles and air pockets. After that, the main descent engine would ignite automatically firing at 10 percent thrust for 5 seconds.<ref>Jim Lovell & Jeffrey Kluger, 1994;"Apollo 13 (previously titled: Lost Moon)", p176; {{ISBN|0671-53464-5}}</ref></blockquote> |
||
== Soviet/Russian operations == |
|||
Ullage motors were used by Soviet engineers for the [[Molniya (rocket)|Molniya]] interplanetary [[launch vehicle]] in 1960. |
|||
Russian [[Proton (rocket family)|Proton]] rockets use ullage motors called SOZ motors. These have a bad tendency of exploding years after end of operations, contributing to space debris. So far, 54 such SOZ motors have exploded in orbit.<ref >[https://www.space.com/russian-rocket-motor-breakup-space-debris SPACE.COM: Old Russian rocket motor breaks up in orbit, generating new cloud of space debris]</ref> |
|||
==References== |
==References== |
||
<references/> |
|||
{{commons}} |
|||
{{Reflist}} |
|||
[[Category:Rocket engines]] |
[[Category:Rocket engines]] |
||
Copy and paste: – — ° ′ ″ ≈ ≠ ≤ ≥ ± − × ÷ ← → · § Cite your sources: <ref></ref>
{{}} {{{}}} | [] [[]] [[Category:]] #REDIRECT [[]] <s></s> <sup></sup> <sub></sub> <code></code> <pre></pre> <blockquote></blockquote> <ref></ref> <ref name="" /> {{Reflist}} <references /> <includeonly></includeonly> <noinclude></noinclude> {{DEFAULTSORT:}} <nowiki></nowiki> <!-- --> <span class="plainlinks"></span>
Symbols: ~ | ¡ ¿ † ‡ ↔ ↑ ↓ • ¶ # ∞ ‹› «» ¤ ₳ ฿ ₵ ¢ ₡ ₢ $ ₫ ₯ € ₠ ₣ ƒ ₴ ₭ ₤ ℳ ₥ ₦ № ₧ ₰ £ ៛ ₨ ₪ ৳ ₮ ₩ ¥ ♠ ♣ ♥ ♦ 𝄫 ♭ ♮ ♯ 𝄪 © ® ™
Latin: A a Á á À à  â Ä ä Ǎ ǎ Ă ă Ā ā à ã Å å Ą ą Æ æ Ǣ ǣ B b C c Ć ć Ċ ċ Ĉ ĉ Č č Ç ç D d Ď ď Đ đ Ḍ ḍ Ð ð E e É é È è Ė ė Ê ê Ë ë Ě ě Ĕ ĕ Ē ē Ẽ ẽ Ę ę Ẹ ẹ Ɛ ɛ Ǝ ǝ Ə ə F f G g Ġ ġ Ĝ ĝ Ğ ğ Ģ ģ H h Ĥ ĥ Ħ ħ Ḥ ḥ I i İ ı Í í Ì ì Î î Ï ï Ǐ ǐ Ĭ ĭ Ī ī Ĩ ĩ Į į Ị ị J j Ĵ ĵ K k Ķ ķ L l Ĺ ĺ Ŀ ŀ Ľ ľ Ļ ļ Ł ł Ḷ ḷ Ḹ ḹ M m Ṃ ṃ N n Ń ń Ň ň Ñ ñ Ņ ņ Ṇ ṇ Ŋ ŋ O o Ó ó Ò ò Ô ô Ö ö Ǒ ǒ Ŏ ŏ Ō ō Õ õ Ǫ ǫ Ọ ọ Ő ő Ø ø Œ œ Ɔ ɔ P p Q q R r Ŕ ŕ Ř ř Ŗ ŗ Ṛ ṛ Ṝ ṝ S s Ś ś Ŝ ŝ Š š Ş ş Ș ș Ṣ ṣ ß T t Ť ť Ţ ţ Ț ț Ṭ ṭ Þ þ U u Ú ú Ù ù Û û Ü ü Ǔ ǔ Ŭ ŭ Ū ū Ũ ũ Ů ů Ų ų Ụ ụ Ű ű Ǘ ǘ Ǜ ǜ Ǚ ǚ Ǖ ǖ V v W w Ŵ ŵ X x Y y Ý ý Ŷ ŷ Ÿ ÿ Ỹ ỹ Ȳ ȳ Z z Ź ź Ż ż Ž ž ß Ð ð Þ þ Ŋ ŋ Ə ə
Greek: Ά ά Έ έ Ή ή Ί ί Ό ό Ύ ύ Ώ ώ Α α Β β Γ γ Δ δ Ε ε Ζ ζ Η η Θ θ Ι ι Κ κ Λ λ Μ μ Ν ν Ξ ξ Ο ο Π π Ρ ρ Σ σ ς Τ τ Υ υ Φ φ Χ χ Ψ ψ Ω ω {{Polytonic|}}
Cyrillic: А а Б б В в Г г Ґ ґ Ѓ ѓ Д д Ђ ђ Е е Ё ё Є є Ж ж З з Ѕ ѕ И и І і Ї ї Й й Ј ј К к Ќ ќ Л л Љ љ М м Н н Њ њ О о П п Р р С с Т т Ћ ћ У у Ў ў Ф ф Х х Ц ц Ч ч Џ џ Ш ш Щ щ Ъ ъ Ы ы Ь ь Э э Ю ю Я я ́
IPA: t̪ d̪ ʈ ɖ ɟ ɡ ɢ ʡ ʔ ɸ β θ ð ʃ ʒ ɕ ʑ ʂ ʐ ç ʝ ɣ χ ʁ ħ ʕ ʜ ʢ ɦ ɱ ɳ ɲ ŋ ɴ ʋ ɹ ɻ ɰ ʙ ⱱ ʀ ɾ ɽ ɫ ɬ ɮ ɺ ɭ ʎ ʟ ɥ ʍ ɧ ʼ ɓ ɗ ʄ ɠ ʛ ʘ ǀ ǃ ǂ ǁ ɨ ʉ ɯ ɪ ʏ ʊ ø ɘ ɵ ɤ ə ɚ ɛ œ ɜ ɝ ɞ ʌ ɔ æ ɐ ɶ ɑ ɒ ʰ ʱ ʷ ʲ ˠ ˤ ⁿ ˡ ˈ ˌ ː ˑ ̪ {{IPA|}}
Wikidata entities used in this page
Pages transcluded onto the current version of this page (help):
This page is a member of 4 hidden categories (help):
