Monopropellant System

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Office europeen des brevets (11) EP 0 950 648 A1

(12) EUROPEAN PATENT APPLICATION

(43) Date of publication:ation: (51) Int. CI.6: C06D 5/08 20.10.1999 Bulletin 1999/42

(21) Application number: 98201190.0

(22) Date of filing: 15.04.1998

(84) Designated Contracting States: (72) Inventors: AT BE CH CY DE DK ES Fl FR GB GR IE IT LI LU • van den Berg, Ronald Peter MC NL PT SE 2291 KJ Wateringen (NL) Designated Extension States: • Mul, Johannes Maria AL LT LV MK RO SI 2013 AE Haarlem (NL) • Elands, Petrus Johannes Maria (71) Applicant: 2804 LK Gouda (NL) NEDERLANDSE ORGANISATIE VOOR TOEGEPAST-NATUURWETENSCHAPPELIJK (74) Representative: ONDERZOEK Smulders, Theodorus A.H.J., Ir. et al TNO Vereenigde Octrooibureaux 2628 VK Delft (NL) Nieuwe Parklaan 97 2587 BN 's-Gravenhage (NL)

(54) Monopropellant system

(57) The invention is directed to a monopropellant composition for propulsion and/or gas generation, comprising a solution of hydrazinium nitroformate (HNF) and/or ammonium dinitramide (ADN) in water and/or an alkanol.

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Description

[0001] The present invention is in the area of monopropellant composition systems, for instance for spacecraft propulsion, in emergency systems for jet fighters or in emergency gasgeneration systems for submarines. 5 [0002] Spacecraft propulsion is defined as that needed for the orientation (attitude control) and positioning (orbit control including de-orbiting) of spacecraft after delivery into the required orbit by the launch vehicle. It is quite separate and distinct from launcher propulsion. The need for spacecraft propulsion begins with its separation from the launch vehicle and terminates at the end of its useful service life. It is usually the depletion of the spacecraft's propellant that terminates its mission. 10 [0003] Typical requirements for attitude and orbit control are very low thrust (0.1 N typically), a pulsed operational mode for attitude control, a continuous operational mode for orbit control and accurate and repeatable performance and reliable leak-free operation. For de-orbiting the thrust can be higher. [0004] The propulsion in this area is amongst others generated by so-called monopropellant thrusters, wherein a propellant is catalytically or thermally decomposed into hot gases which are then expanded through a nozzle. In the area 15 of monopropellants hydrogen peroxide and hydrazine are presently traditionally used. They provide a specific impulse of respectively 1872 and 2266 m/s at an expansion ratio of 50, zero ambient pressure, chamber pressure of 1 MPa and at chemical equilibrium outflow conditions. [0005] Both systems have, however, some drawbacks. Hydrogen peroxide is known for its instability and autodecom- position behaviour. Drawbacks of hydrazine are its toxicity and flammability. 20 [0006] These aspects of currently used monopropellants accordingly require high level, and thus costly, requirements for production, transport, storage, handling and disposal. [0007] The same problems are encountered in emergency systems for jet fighters (emergency start-up of engine after flame-out) and submarines (emptying ballast tanks in emergency situation by generating gas). [0008] It is one of the objects of the present invention to provide a monopropellant composition for spacecraft propul- 25 sion and the other uses described above, which obviates these drawbacks of the prior art system. It is a further object to provide a stable, clean, less toxic, and/or less flammable monopropellant composition. It is also an object to provide a monopropellant composition for spacecraft propulsion that could contribute to a relaxation of requirements and there- fore to a reduction of costs and launch preparation time. [0009] The present invention is based on the surprising finding that known solid high energy oxidisers such as 30 hydrazinium nitroformate and ammonium dinitramide, when dissolved in water provide a liquid monopropellant system having a specific impulse that could be equal to the specific impulse of the conventional monopropellants, without having the disadvantages thereof. [0010] The invention is accordingly directed to a solution of hydrazinium nitroformate and/or ammonium dinitramide in water and/or a lower alkanol as monopropellant composition, especially in spacecraft propulsion. The amount of 35 water and/or lower alkanol in the system should be such that the system is liquid, which determines the lower level of the amount of water. On the other hand there should be sufficient hydrazinium nitroformate and/or ammonium dinitramide present in the system to provide the required impulse. Due to the nature of spacecraft propulsion, this specific impulse of the propellant system should be as high as possible, in order to prolong the lifetime of the satellite. [001 1 ] According to a preferred embodiment hydrazinium nitroformate in water is used. In another embodiment of the 40 propellant system according to the invention additionally an amount of an organic solvent, for example a lower alkanol, such as methanol, ethanol, propanol or butanol, can be used. It has been found that this increases the specific impulse of the monopropellant. The amount of alkanol in the solution is preferably between 0 and 70 wt.%, whereas methanol and/or ethanol are preferred. [0012] An especially preferred system consists of 25 to 75 wt.% of hydrazinium nitroformate, 5 to 50 wt.% of water 45 and 0 (more preferred 5) to 25 wt.% of lower alkanol. [001 3] In accordance with the invention it is also possible to include other additives in the propellant system, including, but not limited to solubilisers, vapour pressure decreasing agents and performance improving agents. [0014] In another embodiment the present invention is directed to a process for orienting and positioning of spacecraft after delivery into the required orbit by a launch vehicle using a spacecraft propulsion system based on monopropellant so thrusters, wherein the monopropellant discussed hereinabove is used for propulsion. [0015] Hydrazinium nitroformate and ammonium dinitramide are known high energy solid oxidisers. The use of hydrazinium nitroformate as ingredient in high performance propellant combinations for rocket engines is for example disclosed in European patent application 350, 1 36. A production process for hydrazine nitroformate is further disclosed in the international patent application WO-A 9410104. Ammonium dinitramide is also a known material, the production 55 of which is for example disclosed in WO-A 9424073. [001 6] The monopropellants according to the invention can be used in the conventional way for spacecraft propulsion, in existing systems, whereby it is to be noted that due to the properties of the system, less strict requirements concern- ing storage, transport and handling are possible.

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Description of the figure.

[001 7] The figure shows a comparison of specific impulse of various propellant systems. [0018] The specific impulse of various monopropellant systems in accordance with the invention has been compared 5 with the values for an aqueous solution of ammonium dinitramide and hydrazinium nitroformate in water, at 50 wt.% water. In the following table and in the figure the specific impulse is given for an expansion ratio of 50 and a chamber pressure of 1 MPa, zero ambient pressure and at chemical equilibrium outflow conditions.

Table 1 Specific Impulse m/s Ingredient Based on 50% water and For the pure oxidiser 50% oxidiser Hydrazinium 1 754 2950 Nitroformate (HNF) Ammonium 1267 2319 Dinitramide (ADN) Hydrogen Peroxide 1 872 (H202) Hydrazine 2266 (N204)

[001 9] As can be seen in the table 50% oxidisers/water mixtures result in a performance loss compared to hydrogen peroxide and hydrazine. This performance loss may be acceptable in view of the reduction of cost due to simpler pro- 30 cedures for production, transport, storage, handling and disposal. Furthermore, by increasing the amount of dissolved oxidiser the performance can be further increased. If fuels such as lower alkanols are added, performance equal to or even exceeding the performance of hydrazine is possible. [0020] In the attached figure the specific impulse is given for various compositions of hydrazinium nitroform in water, using various concentrations, ammonium dinitramide in water using various concentrations and for a combination of 35 hydrazinium nitroform, ethanol and water.

Claims

1. Monopropellant composition for propulsion and/or gas generation, comprising a solution of hydrazinium nitrofor- 40 mate (HNF) and/or ammonium dinitramide (ADN) in water and/or an alkanol.

2. Monopropellant composition according to claim 1 , wherein the amount of HNF and/or ADN is from 25 to 95 wt.% of the composition.

45 3. Monopropellant composition according to claim 1 or 2, comprising water and an amount of a solvent, preferably a lower (C1 to C4) alkanol.

4. Monopropellant composition according to claim 3, wherein the alkanol is methanol and/or ethanol. so 5. Monopropellant composition according to claim 3 or 4, wherein the amount of alkanol is between 5 and 70 wt.%.

6. Monopropellant composition according to claim 1-5, consisting of 25 to 75 wt.% of hydrazinium nitroformate, 5 to 50 wt.% of water and 0 to 25 wt.% of lower alkanol.

55 7. Monopropellant composition according to claim 1-6, further comprising solubilisers, vapour pressure decreasing agents and/or performance improving agents.

8. Use of a composition of hydrazinium nitroformate and/or ammonium dinitramide according to claim 1 -7 as propel-

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lant in spacecraft propulsion.

I. Use of a composition of hydrazinium nitroformate and/or ammonium dinitramide according to claim 1-7 as emergency propellant in jet fighters.

0. Use of a composition of hydrazine nitroformate and/or ammonium dinitramide according to claim 1-9 in an emergency gas generation system for submarines.

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Patent Number European EUROPEAN SEARCH REPORT Application Office EP 98 20 1190

DOCUMENTS CONSIDERED TO BE RELEVANT Citation of document with indication, where appropriate, Relevant CLASSIFICATION OF THE Category of relevant passages to claim APPLICATION (lnt.CI.6) DATABASE COMPENDEX C06D5/08 ENGINEERING INFORMATION, INC. , NEW YORK, NY, US OXLEY J C ET AL: "Thermal decomposition studies on ammonium dinitramide (ADN) and N and H isotopomers" XP002075366 * abstract * 8-11 & J PHYS CHEM A; JOURNAL OF PHYSICAL CHEMISTRY A JUL 31 1997 ACS, WASHINGTON, DC, USA, vol. 101, no. 31, 31 July 1997, pages 5646-5652,

X US 5 316 749 A (R.J. SCHMITT ET AL.) 31 1 May 1994 A * column 6, line 45 - column 7, line 8 * 8-11

X WO 97 06099 A (FORSVARETS 1 FORSKNINGSANSTALT) 20 February 1997 A * 4, line 26 - 5, line 2 * 8-11 TECHNICAL FIELDS page page SEARCHED (lnt.CI.6) D,X WO 94 10104 A (AEROSPACE PROPULSION 1 C06D PRODUCTS B.V.) 11 May 1994 C06B A * page 1, line 35 - page 2, line 9 * 8-11 C01B * page 6, line 7 - line 15 * AGRAWAL J P: "Recent trends in 1,8-11 high-energy materials" PROGRESS IN ENERGY AND COMBUSTION SCIENCE, vol. 24, no. 1, 1998, page 1-30 XP004107967 * page 29 - page 31 * US 5 648 052 A (K.J. SCHAEFER ET AL.) 15 8-11 July 1997 * column 1, line 27 - line 39 * V-

The present search report has been drawn up for all claims Place of search Date of completion of the search Examiner THE HAGUE 24 August 1998 Schut, R CATEGORY OF CITED DOCUMENTS T : theory or principle underlying the Invention E : earlier patent document, but published on, or X : particularly relevant if taken alone after the filing date V : particularly relevant if combined with another D : document cited in the application document of the same category L : document cited for other reasons A : technological background O : non-written disclosure & : member of the same patent family, corresponding P : intermediate document document

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Patent Number J European EUROPEAN SEARCH REPORT Application Office EP 98 20 1190

CHEMICAL ABSTRACTS, vol. 123, no. 14, 1,8-11 2 October 1995 Columbus, Ohio, US; abstract no. 174351p, T. ANAN ET AL.: "Physical and chemical properties of HNF" page 281; XP000663569 * abstract * & KAYAKU GAKKAISHI, vol. 56, no. 3, 1995, pages 99-104,-104,

TECHNICAL FIELDS SEARCHED (lnt.CI.6)

The present search report has been drawn up for all claims Place of search Date of completion of the search Examiner THE HAGUE 24 August 1998 Schut, R CATEGORY OF CITED DOCUMENTS T : theory or principle underlying the invention E : earlier patent document, but published on, or X : particularly relevant if taken alone after the filing date Y : particularly relevant if combined with another D : document cited in the application document of the same category L : document cited for other reasons A : technological background O : non-written disclosure & : member of the same patent family, corresponding P : intermediate document document

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ANNEX TO THE EUROPEAN SEARCH REPORT DN EUROPEAN PATENT APPLICATION NO. EP 98 20 1190

rhte annex lists the patent tamily membersrelating to trie patent documents citad in the above-mentioned European search report, rhe members are as contained in the European Patent Office EDP file on rha European Patent Office is in no way liable for these particulars which are merely grven for 1he purpose of information. 24-08-1998

Patent document Publication Patent family Publication cited in search report date memberts) date US 5316749 A 31-05-1994 NONE WO 9706099 A 20-02-1997 AU 6539696 A 05-03-1997 EP 0843647 A 27-05-1998 NO 980534 A 06-02-1998 SE 9503326 A 09-02-1997

W0 9410104 A 11-05-1994 NL 9201916 A 01-06-1994 CA 2148352 A 11-05-1994 EP 0670823 A 13-09-1995 NO 951678 A 27-06-1995 US 5557015 A 17-09-1996

US 5648052 A 15-07-1997 NONE WO 9119669 A 26-12-1991 US 5254324 A 19-10-1993 CA 2059654 A 19-12-1991 DE 69106848 D 02-03-1995 DE 69106848 T 18-05-1995 EP 0487693 A 03-06-1992 JP 2519621 B 31-07-1996 JP 5500795 T 18-02-1993

m For more details about this annex : see Official Journal of the European Patent Office, Mo. f 2/82